Rotary motor with integral fluid seal

Abstract

A rotary compressor or expander apparatus embodies a scaling solution that is based on the physical configuration of the leakage path and various of its features to substantially inhibit flow of fluid through the leakage path, with minimal leakage.

Description

TECHNOLOGICAL FIELD

[0001] The present disclosure is generally in the field of apparatuses that can compress a fluid or utilize a compressed fluid to generate power. Such apparatuses include compressors, pumps, expanders, or engines. More specifically, this disclosure concerns such apparatuses that employ a rotating displacement-mechanism, like positive displacement compressors, pumps, expanders, and positive-replacement engines.BACKGROUND ART

[0002] References considered to be relevant as background to the presently disclosed subject matter are listed below:

[0003] U.S. Pat. No. 4,890,990

[0004] U.S. Pat. No. 9,638,035

[0005] Acknowledgement of the above references herein is not to be inferred as meaning that these are in any way relevant to the patentability of the presently disclosed subject matter.BACKGROUND

[0006] Rotating mechanism are well known in the art for compressing or expanding a fluid. These involve a main rotor with a plurality of projections that rotate in an annular space formed between opposite surfaces of the rotor and the stator (this rotor is referred to herein, also, as “male rotor”). In such rotatory mechanism these projections that closely engage the opposite stator surfaces of the annular space, define, with reciprocating or rotary elements that are fixed in the stator and fit into the annular space and closely engage it, dynamic chambers that change in volume as these projections approach to or recede from such fixed elements. Apparatuses that embody such a mechanism is disclosed in U.S. Pat. Nos. 4,890,990 and 9,638,035.

[0007] One of the challenges in such rotary-mechanisms is to adequately seal the annular space and avoid leakage of compressed fluid through the small clearance between the rotating elements (to be referred to herein, at times, as “fluid leakage path”) and the surroundings of the apparatus. This is particularly acute where, in addition to a main rotor, the elements that are fixed in the stator and fit into the annular space and closely engage it are rotating elements that rotate in tandem with the main rotor (often referred in the art as “female rotor(s)”).

[0008] A solution to this problem is taught by U.S. Pat. No. 4,890,990 through a paraboloid-like cross-sectional shape of the annular space. The difference in the radial and axial expansion of the different elements upon heating is balanced and compensated by the angle of the side walls, which have the same or similar ratio, thus maintaining mostly an even gap of the leakage path formed between the male rotor and the stator. This notwithstanding, the walls of the fluid leakage path between the male rotor and the stator will nonetheless expand differently and thus it is practically impossible to completely seal the fluid leakage path, especially at sharp corners, where the radial and axial expansions are different.

[0009] Additionally, as noted above, it is particularly difficult to seal fluid leakage path occurring at the intersection of the male and female rotors, where the fluid leakage path between the male rotor and the stator is interrupted giving rise to a fluid leakage path that is formed between the male rotor and the female rotor that bifurcates into two fluid paths, extending in different directions, one formed between the male rotor and the stator and the other between the female rotor and the stator. As the intersection of the rotors is between versions of a similar hyperboloid geometry, however with different axes and diameters, there are sharp edges between different leakage paths at the intersection which may increase leakage. This problem is compounded by the fact that such sharp edges at such intersection cannot practically be produced, which means that they will be rounded, increasing the gap of the leakage channels at such point and potentially increasing fluid leakage.GENERAL DESCRIPTION

[0010] The present disclosure concerns an apparatus with a rotary mechanism where two main rotating parts are rotating relatively to each other around the same, main axis of the apparatus—one may be a rotor and the other may be a stator, and form together a radially and axially confined annular space between them, confined in both circumferential and axial directions (to be referred to herein as “confined annular space”). There is at least one a projecting element that extends from one of the parts into the confined annular space and closely engages the walls of said space, and at least one additional rotor (referred to herein as “auxiliary rotor”) rotating about a different axis (referred to herein as “auxiliary axis”), typically parallel to the main axis, that is disposed in one of the two parts and rotates in synchrony with the main rotating part. The auxiliary rotor, which is an axially symmetric element, has a portion that abuts into the confined annular space (that may be referred to herein as “abutting portion”), that closely engage the walls of said space. The term “closely engage” denotes an engages that substantially minimizes or even essentially avoid flow of fluid therethrough. The at least one projecting element and with the at least one abutting portion define between them at least one annular chamber that continuously changes in its length in consequence of the rotation—contracting when the projecting element advances in its rotation towards the abutting portion and expands when the projecting element recedes in its rotation away from the abutting portion.

[0011] In order to permit rotation, there needs to be minimal clearance between rotating parts and other rotating or static parts, taking into consideration also expansion and contraction that inevitably occurs upon respective increase or decrease in temperature during operation. This minimal clearance leads to gaps that create paths that enable leakage and losses of fluid within the annular chambers (such path(s) to be referred to herein as “leakage path(s)”), especially when such chambers contain highly pressurized fluid. The leakage path extends from within the confined annular space to the apparatus' periphery along the surfaces of the rotating elements in the apparatus in a general axial direction.

[0012] The present disclosure provides sealing solutions for such apparatuses.

[0013] The disclosure herein concerns such an apparatus with a unique sealing arrangement.

[0014] The apparatus of this disclosure may be configured to operate as one or more of a compressor, pump, or an expander.

[0015] The current disclosure provides an apparatus for rotary compression or expansion of a fluid with a unique sealing mechanism that functions to substantially seal a confined annular space in which the fluid is compressed or expanded.

[0016] Between any two elements that rotate one versus the other and operate in fluid compression or expansion, there are fluid leakage paths formed between a rotating element and congruent faces of another element of the apparatus, and consequently the working fluid (namely the fluid the undergoes compression or expansion) may leak therethrough, hampering the operation efficiency, as noted above. The present disclosure provides configurations of the fluid leakage paths to minimize or at times practically avoid leakage of fluid through the fluid leakage paths. Provided by the present disclosure is also an apparatus implementing such configurations of the fluid leakage paths, in which such fluid leakage is impeded or even substantially avoided, namely is avoided to a great or significant extent.

[0017] There are several embodiments that are described herein identified by their serial number according to the order as they are described, as “embodiment (1)”, “embodiment (2)”, etc. Each of these embodiments may be implemented in a variety of different ways which may be referred to also by the term “embodiment”; for example, “by one embodiment of embodiment (1) . . . ”; etc. It should be noted that these embodiments may be used individually or in any combination in an apparatus that is used in accordance with the teaching of this disclosure.

[0018] When referring to the leakage paths according to the different embodiment of the scaling arrangements, the term “proximal” and “distal” may be used to denote relative position of such sections with respect to the confined annular space and the flow path of the leaking fluid along the path. In other words, the leakage path extends from within the confined annular space in the general proximal-to-distal direction, with distal sections of the leakage path being further removed along the leakage path as compared to proximal sections; and the leaking fluid flows along the leakage path in the general proximal-to-distal direction. A flow in the proximal-to-distal direction may be referred to herein as “forward flow” and a flow in the opposite direction may be referred to as “counter flow”.

[0019] The Apparatus of this disclosure embodies a sealing solution that is based on the physical configuration of the leakage path and various of its features to substantially inhibit flow of fluid through the leakage path, with minimal leakage. The term “active sealing” denotes that the scaling is active once the apparatus is in operation and is a consequence of the flow of leaking fluid through the leakage path. The active sealing is embodied in one or more of: (i) a first, proximal section of the leakage path that extends over circumferential side walls of the confined annular space that are defined by the rotor (embodiment (1)); (ii) provision of interrupted leakage paths where a leakage path branches into differently directed paths (embodiment (2)) with optional rotary projections extending from the main and / or the auxiliary rotor that are applicable, in particular in the interrupted leakage paths configuration. The active sealing may also be supplemented by passive sealing elements known per se, such as a rotary sealing. This is particularly enabled by an embodiment of embodiment (2). The embodiments may be combined with each one providing an additional sealing effect to one or more others.

[0020] Some additional terms used herein and their meanings, include:

[0021] The term “apex”, as used herein in connected with a fluid leakage path to denote the most radially extending region of an arcuated section of the path.

[0022] The terms “seal” or “sealing” denotes the substantial blockage of leakage of fluid from the confined annular space to the apparatus' exterior, such blockage at least significantly minimizes fluid losses and, at times, blocks these completely. In other words, a seal substantially inhibits such leakage, meaning that even if some minute leakage remains, it has no or very little functional effect on the operation of the apparatus.

[0023] The term “fluid” is used herein to denote any compressible working fluid that may be a gas, a gas mixture, a gas carrying aerosol or other particles, etc. As can readily be understood the disclosure herein is not limited to any specific compressible fluid which may be chosen according to the specific working conditions or needs.

[0024] The term “rotor-associated leakage path” denotes a fluid leakage path formed between the external surface of a rotor and opposite congruent surface, primarily those of a stator. Specifically, the terms “auxiliary rotor-associated leakage path”, “second part-associated leakage path” and “main rotor-associated leakage path” denote a fluid leakage path that is, respectively, formed between the auxiliary rotor, the second part and the main rotor, and between opposite congruent surfaces.

[0025] The term “about” as used herein means that the value may ±1% of the indicated value and at times ±2%, ±3%, ±4%, ±5%, ±6%, ±7%, and up even up ±10% of the indicated value. It should be noted that any numerical value given in this disclosure even with an “about” qualifier should be read as meaning to be a value which is about that which is given.

[0026] Other terms that are used herein will be understood from their context.

[0027] By embodiment (1) of this disclosure, the confined annular space has side walls that are defined by circumferential radially extending projections that have each an arcuated surface defining, jointly with congruent faces of the rotor a first section of a fluid leakage path that extends in a general axial direction over the arcuated surface into other sections of the fluid leakage path. The centrifugal forces that act on the leaking fluid, cause droplets, mist or other particles that are dispersed in the fluid to accumulate in the apex region of the arcuated surface and the formation of a film at that region. The film has a sealing effect hindering, once formed, leakage of fluid through this section and, hence, having an effect of at least partially sealing the confined annular space.

[0028] By embodiment (2) the main rotor and the auxiliary rotor are configured such that their intersection with one another creates a branching out of the fluid flow path in the forward flow direction. The branching is into two distal sections: one directed in the general axial direction along auxiliary rotor-associated leakage paths and the other in a general radial direction along a generally radially extending section of the second part-associated leakage path or the main rotor-associated leakage path defined below. This may induce: several active sealing effects, among these backing up of leakage losses through oscillations in consequence of the cyclical change of pressure in all angular sections of the confined annular space which means; and increase in the flow time of the fluid such that the time it takes for the fluid to flow through the distal sections of the leakage paths is less than the change of pressure within an angular section of the confined annular space, and, thus, forward flowing fluid will counterflow as a result of pressure reduction in the associated angular section before traversing the entire leakage path.

[0029] Such branching, also yields two distinct leakage path that permit to add additional leakage preventing features to each of the branched. For one, as will be described below, it permits also to form the rotors with one or more circumferential radial projections, each with an arcuated rim, defining a tortuous fluid leakage path with two generally radial sections extending about the rim of the projection. Similarly as in embodiment (1) the centrifugal forces that act on the leaking fluid, will cause droplets, mist or other particles that are dispersed in the fluid to accumulate at the rim region and the formation of a film at that region. The film at has a sealing effect hindering, once formed, leakage of fluid therethrough. Additionally, this clear segregation of the leakage paths, permit to fit rotary seals at the end of such paths.

[0030] It was also realized in accordance with another embodiment of this disclosure, to be referred to as embodiment (3), that in order to avoid significant changes in the width of the gap between the congruent surfaces of the generally radial sections, in view of the difference between radial and axial heat-induced expansion of the confined annular chamber and other parts of the apparatus, the generally radially extending sections should be angled such that the change of width will be within ±25% tolerance over the range of operating temperatures of the apparatus. Namely, the generally radial sections should be angled with respect to the axis such that given the difference in radial to axial expansion there will only minor changes in the gap between the congruent faces of such sections. To achieve that these generally radial sections may have an angle of about 80-81° vis-à-vis the axis, typically about 81°. Such sections include, for example, the generally radially extending section that extends from the intersection of embodiment (2) or the generally radial sections defined by the circumferential radial projections of embodiment (2).

[0031] Provided by this disclosure is, thus, an apparatus that comprises a first part and a second part, one or both rotatable against one another about a main axis, defining axial direction (a direction parallel to the axis) and a radial direction (a direction normal to the axis). There are one or more auxiliary rotors that are fitted in said first part and rotatable about auxiliary axes parallel to said main axis. The apparatus may comprise two or more (e.g. 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or even more) auxiliary rotors. The auxiliary rotors are fitted in said first part and are rotatable about auxiliary axes parallel to said main axis. The rotations of the rotatable elements are synchronized and function jointly to compress, expand or pump a fluid within a confined annular space formed between the first and second parts. There are fluid leakage paths that are formed between congruent opposite faces formed between each two of the first part, the auxiliary rotor, and the second part. Each fluid leakage path is configured with an active sealing element obstructing flow of fluid through said path upon rotation, the active sealing element comprises one or both of the following (1) and (2):

[0032] (1) a proximal section of the leakage path that extends from within the confined annular space and is formed between an arcuated peripheral surface of circumferential side walls of said space that are defined by said second part and between congruent surfaced of said first part, and

[0033] (2) an interrupted leakage path in which a proximal section of the fluid leakage path extending from within the confined annular space branches into two distal sections including (i) one or more auxiliary rotor-associated leakage paths, each extending in a general axial direction and formed between one of the auxiliary rotors and congruent surfaces of the first part, and (ii) a generally radially extending section of a second part-associated leakage path formed between a member of said second part and congruent surfaces of said first part.

[0034] Also provided by this disclosure is, an apparatus that comprises a first part and a second part, one or both rotatable against one another about a main axis, defining axial and radial direction. There are one or more auxiliary rotors that are fitted in said first part and rotatable about auxiliary axes parallel to said main axis. The rotations are synchronized and function jointly to compress, expand or pump a fluid within a confined annular space formed between the first and second parts. There are fluid leakage paths that are formed between congruent opposite faces between each two of the first part, the auxiliary rotor, and the second part. The fluid leakage path having a section that has a generally radial trajectory, angled at about 80-81°, typically 81, with respect to the axis.

[0035] Embodiments of this disclosure will now be described with reference to two set of embodiments: one set under the heading of “general aspect” and the other under the heading of “specific aspect”, both concerning apparatuses of this disclosure. The term “aspect” is used only from linguistic convenience and has no connotation beyond that. Embodiments described in connection with the general aspect applies also to the specific aspect, at time while making necessary alterations; and vice versa.General Aspect

[0036] The apparatus, of the general aspect of this disclosure, comprises a first part and a second part, one or both rotating against one another about a main axis that defines axial directions (a direction parallel to the axis) and a radial direction (a direction normal to the axis). The first part may be a stator and the second part may be a rotor. The apparatus also comprises two or more (e.g. 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or even more) additional rotors, defined herein as “auxiliary rotor(s)”. The auxiliary rotors are fitted in said first part and are rotating about auxiliary axes parallel to said main axis. The rotations of the elements function to jointly compress, expand or pump a fluid within a confined annular space defined between the first and second parts at a radial engagement sector about the second part. The two or more auxiliary rotors engage the second part.

[0037] There are fluid leakage paths that are defined between congruent opposite faces between each two of the first part, the auxiliary rotor and the second part. The fluid leakage paths each comprise one or more sections extending over an apex of a circumferential radially rotating projection.

[0038] According to embodiment (1) of this general aspect, said confined annular space has two circumferential side walls extending from said second part with an arcuated peripheral surface and said fluid leakage path has a proximal section of the leakage path that extends from within the confined annular space and is formed between the arcuated peripheral surface and congruent surface of the first part.

[0039] According to embodiment (2) of this general aspect, the fluid leakage path is configured with an interrupted leakage path in which a proximal section of the fluid leakage path extending from within the confined annular space is branching into two distal sections including (i) one or more auxiliary rotor-associated leakage paths, each extending in a general axial direction and formed between one of the auxiliary rotors and congruent surfaces of the first part, and (ii) a generally radially extending section of a second part-associated leakage path formed between a member of said second part and congruent surfaces of said first part.

[0040] According to embodiment (3) of this general aspect, the fluid leakage path comprises one or more sections that extend in the general radial direction and has a trajectory such that the difference in heat-induced radial to axial expansion will cause a minimal change in the width of the gap between congruent surface of said section. Said trajectory may be angled at about 80-81° with respect to the axis, typically about 81°.

[0041] The generally arcuated surface may have a semi-circular cross-section, may have a cross section defining part of an ellipse, a polygonal cross-sectional shape or generally any kind of spline. The rotation causes centrifugal forces that cause droplets or mist particles to accumulate at the apex of the arcuated surface where these may coalesce and form a film that will inhibit flow of leakage fluid.

[0042] According to an embodiment of this disclosure the proximal section branches into two distal sections consisting of (i) an auxiliary rotor-associated leakage path (for each of the one or more auxiliary rotors), and (ii) a second part-associated leakage path. Each of the auxiliary rotor-associated leakage paths extends in a general axial direction and is formed between one of the auxiliary rotors and congruent surfaces of the first part. The second part-associated leakage path is generally radially directed and is extending from the branchpoint along faces of said second part.

[0043] By an embodiment of this disclosure said generally radially directed section is linked at its distal end to a distal section extending from said distal end in a general axial direction. Thus, the distal section of the second part-associated leakage path that extends from the branch point is has one leg that is generally radially oriented and another leg that has a general axial orientation.

[0044] By an embodiment of this disclosure, said annular members have an inner, generally radially oriented face defining side walls of the confined annular space, an outer face longer than the inner face extending in a generally radial direction and defines said radially directed section. Where said second part is the inner element encompassed within the confines of or a frame constituted or defined by said first part, said outer face extends radially in the general direction of the axis. Where the arrangement is reversed, namely said first part is encompassed within the confines of said second part, said outer face extends in the opposite direction, namely in a direction away from the axis.

[0045] The branching the proximal section into the two distal sections may yield a backup of leakage losses by oscillations of the fluid along the path of each branch and may also induce pressure drop and concomitant reduction speed and condensation of flow of the fluid the leakage path branchpoint and, hence, de facto sealing of these paths.

[0046] The rotating elements and the fluid leakage paths on the two sides of the apparatus typically display a mirror symmetry about a plane of symmetry passing through the midline of the confined annular space and normal to the main axis.

[0047] The apparatus by an embodiment of this disclosure comprises at least one circumferential radial projection, namely a projecting member that extends radially in all directions and having the general form of a disc, extending from a rotating element of (e.g. a main rotor and / or an auxiliary rotor) into and rotatable within a congruent receiving recess of another element, defining a tortuous fluid leakage path with sections thereof extending in a general radial direction and linked to one another by a section extending over a rim of the at least one circumferential radial projection. As the leakage paths are typically mirror symmetric on both sides of the confine annular space, the radial projections may be symmetrically formed on both sides of said space. There may be two or more such circumferential projections in each fluid leakage path and in such a case they may all be of the same radial span from the rotating element (namely the maximal diameter of the radial projection), although typically (albeit not exclusively) at least one of them has a radial span that is different than at least one other circumferential projection. In some cases there may be one such circumferential projection with a relatively large radial span flanked by two, three or more circumferential projections of a relatively small radial span; or there may a two or three with a first of these (namely the first encountered by the fluid flowing through the leakage path out of the confined space) being the largest and consecutive ones with descending radial extensions.

[0048] The at least one circumferential projection may be formed in the second part and rotatable within a congruent receiving recess of said first part to define a tortuous auxiliary fluid leakage path with sections thereof generally radially extending from both axial sides of the projection and linked to one another by a section that extends over the rim, typically arcuated, of the circumferential projections. Similarly, the at least one circumferential projection may be formed in the auxiliary rotor and rotatable within a congruent receiving recess of the first part, defining a tortuous auxiliary fluid leakage path with sections thereof generally radially extending from both axial sides of the projection and linked to one another by a section that extends over the rim, typically arcuated, of the circumferential projections. The circumferential projections may have a generally tapering cross-section extending from their base to a rounded tip.

[0049] The fluid flowing through the leakage path is induced into a swirl by the rotating element. The rotational component of the swirl increases when the fluid flows about the circumferential projections, as the absolute speed of rotation at the apex is greater than at the basis. This gives rise to centrifugal forces that grow toward the apex, and these centrifugal forces cause accumulation of fluid carried components (comprising one or more of droplets, mist or other particles carried by the fluid) to accumulate at an apex of such segments of the circumferential radial projections, typically generating a film that reduces or at times almost entirely prevent leakage.

[0050] According to an embodiment of this disclosure the auxiliary rotor-associated fluid leakage path has a segment immediately distal to the branchpoint that defines a general trajectory away from the auxiliary axis.

[0051] Said generally radially directed section has typically a trajectory such that the difference in heat-induced radial to axial expansion will cause a minimal change in the width of the gap between congruent surfaces of the generally radially directed section, e.g. a change in width that is less than about ±25% over the range of operating temperatures of the apparatus. By one example, the trajectory of said proximal section is about 81°.

[0052] It should be noted that similar considerations for the trajectory of said generally radially directed section may apply also to the generally radially directed sections of the fluid leakage paths that are defined about the circumferential radial projections.

[0053] The angle between the said segment of the auxiliary rotor-associated leakage paths and said outer face may be about 90°.

[0054] By an embodiment of this disclosure the leakage paths are configured such that the flow time of fluid from the annular confined space has a travel time through the leakage path (particularly, but not only, in a consequence of the branching at said leakage path branchpoint and the slowdown of the rate of flow of the fluid in consequence thereof) is longer than the time for pressure change in angular portions of the confined annular space in consequence of rotation of the projecting elements in said space between different pressure strokes: including a pressure-stroke with high pressure to a suction-stroke with low pressure, when the apparatus is configured or operative as a compressor; or from an expansion stroke with high pressure to a complete expansion or a condensation-stroke in the annular chamber(s), when the apparatus is configured or operative as an expander. There is some inherent delay between a rise in pressure until it translates into flow of fluid through the leakage path (or any fluid flow path for that matter) pressure. The pressure of fluid in any portion of the confined annular space cyclically changes between high and low pressure. If the flow time of pressurized fluid through the flow paths is longer than the time it takes for the fluid to travel through the fluid flow paths before a resulting flow of fluid through the leakage paths, this may serve as a barrier for fluid leakage. Namely, there will rather be a cyclical change in flow direction in the fluid leakage paths between a forward direction and a counter direction.

[0055] The peripheral portions of rotating elements that comprise the apex of said arcuated section or the rim of the circumferential radial projections define segments of a leakage path with congruent faces, that yield, as noted above, to the accumulation of particles, including droplets and mist, resulting in formation of a film in such segments that impedes, or at times, substantially blocks free flow of fluid through the leakage paths.

[0056] By an embodiment of this disclosure, the fluid leakage path has an enlarged cross-section at a portion thereof opposite the rim of a circumferential radially projecting member. This results in a local pressure drop, in consequence of the enlarged cross-section, reducing speed of the fluid flowing therethrough, thus facilitating deposition of droplets or mist and the formation of a film.

[0057] By embodiments of this disclosure, one or more of leakage paths are configured to have one or more section with a width different than other sections. Enlargement of the width may yield reduction in pressure of the fluid flowing in the leakage path and a resulting slow-down in travel speed of fluid in the fluid leakage path. The leakage path branchpoint may also be configured to cause reduction of pressure and a resulting slow-down in travel speed of fluid in said auxiliary rotor-associated leakage path and the radially directed section of the second part-associated leakage path. This may be achieved through a change in dimensions of said width, which causes a pressure drop and, hence, a slowdown of flow-speed of leaking fluids through the leakage paths. In some embodiments the fluid leakage paths may be configured to have number of width changes of dimensions. This may be through design of some imperfect congruencies at certain sections of the liquid flow paths.

[0058] The slowing down of the flow of the fluid through the fluid leakage paths may also be achieved through a three-dimensional surface structure that is configured to increase friction of the fluid flowing in such section. Such a surface structure may be achieved through the introduction of minute or even microscopic surface imperfections, such as abrasions, indentations, or protrusions. For example, a portion of one or both of (i) a section of said auxiliary rotor-associated leakage path that extends from said branching and (ii) said proximal section, has such a three-dimensional surface structure.

[0059] In some embodiments, particularly embodiments of embodiment (2), a fluid seal is fitted in one or more of the fluid leakage paths. These may comprise one or more rotary sealing elements fitted at an end of a fluid leakage path. Such rotary sealing elements may comprise encapsulated ball bearings.

[0060] The apparatus of this disclosure may be configured to operate as a compressor or an expander. Where the apparatus is configured as a compressor, it may be configured to reach an increase of pressure in a first step of at least two rotary steps and a further increase of said pressure to a higher pressure in a second step. Where the apparatus is configured as an expander, it may be configured to reach a decrease of pressure in a first step of at least two rotary steps and a further decrease of said pressure to a lower pressure in a second step.

[0061] Said first part may be a stator and said second part may be a main rotor. The main rotor may comprise projecting elements that extend therefrom into the confined annular space that define in their rotation, jointly with portions of the auxiliary rotors that adjacently project into said space, two or more chambers within said annular space that either expand, as the projecting elements recede in their rotation away from said portions or shrink as the projecting elements advance in their rotation towards said portions, to thereby, respectively, expand fluid contain therein or compress such fluid.

[0062] Said second rotating member may be configured as a male, main rotor, namely having radial projections (referred herein as “projecting elements”) that adjacently fit into the confined annular space, and said auxiliary rotor is a female rotor, namely configured with one or more recesses for receiving said projections. The female rotor that is disposed in said first part, is peripheral to said male rotor, where said first part is peripheral to said second part. The arrangement may, however, be also reversed with the first part being defined within the confines of said second part.

[0063] Each of said portions of the auxiliary rotors may comprise one or more recesses that are configured to receive the projecting elements and the rotations of the main and auxiliary rotors are synched to permit such reception as the projecting elements rotate past such portion.Specific Aspect

[0064] Some specific embodiments will now be described. The explanatory notes already provided above, that are applicable also for some of embodiments described below, will not be repeated.

[0065] The apparatus of this specific aspect comprises a main rotor and a stator. The main rotor is rotatable about a main axis, the main rotor and the stator having respective annular rotor face and annular stator face that face one another and define between them a confined annular space. Two or more (e.g. 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or even more) of auxiliary rotors are embedded in form-matching receiving spaces within the stator and are radially disposed about the main rotor, each engaging the main rotor at a radial engagement sector. Each of the rotors is axially rotatable about an auxiliary axis parallel to the main axis and configured to rotate in synchrony with the main rotor. Each of the auxiliary rotors has an engaging portion with an engaging abutment that abuts into the annular confined space and that is configured to roll at sealing fitness over the annular rotor face. A plurality of projecting elements are disposed on said annular rotor face and extend therefrom into the confined annular space and are rotatable with the main rotor within the confine annular space. The projecting elements are configured to adjacently engage said annular stator face and to be adjacently received in an engaging groove formed on said engaging abutment. The projecting elements define in their rotation, jointly with said engaging portions, transient and volume-changing compartments for fluid intake, compression, expansion, or discharge.

[0066] According to embodiment (1) of this specific aspect, each of the fluid leakage paths comprise a proximal section extending in a general axial direction and formed between a generally arcuated face of one of the annular members and congruent surfaces of the stator.

[0067] According to embodiment (2) of this specific aspect, each of the fluid leakage paths comprise a proximal section extending in a general axial direction and formed between a generally arcuated face of one of the annular members and congruent surfaces of the stator; and wherein said proximal section is branching into two distal sections including (i) one or more auxiliary rotor-associated leakage paths, each extending in a general axial direction and formed between one of the auxiliary rotors and congruent surfaces of the first part, and (ii) a generally radially extending section of a second part-associated leakage path formed between a member of said second part and congruent surfaces of said first part.

[0068] According to embodiment (3) of this specific aspect, each of the fluid leakage paths comprise a proximal section extending in a general axial direction and formed between a generally arcuated face of one of the annular members and congruent surfaces of the stator; the fluid leakage path comprising one or more sections that extend in the general radial direction and has a trajectory such that the difference in heat-induced radial to axial expansion will cause a minimal change in the width of said section. Such trajectory may be angled at about 80 or 81° with respect to the axis, typically about 81°.

[0069] The rotor has two annular members on two sides of the confined annular space, each with an inner face defining side walls of the confined annular space and outer face longer than the inner face extending to a generally axially extending base, the two walls connected by and arcuated section.

[0070] There are fluid leakage paths that are formed between congruent opposite faces that are defined between the main rotor, the auxiliary rotor, and the stator. Each of the fluid leakage path comprises a proximal section extending in a general axial direction and formed between a generally arcuated face of one of the annular members and congruent surfaces of the stator. The generally arcuated face may have a semi-circular cross-section, may have a cross section defining part of an ellipse, a polygonal cross-sectional shape or generally any kind of spline.

[0071] By an embodiment of this disclosure said proximal section branches into two distal sections: (1) auxiliary rotor-associated leakage paths, each extending in a general axial direction and formed between one of the auxiliary rotors and congruent surfaces of the stator; and (2) a generally radially directed section of a main rotor-associated leakage path

[0072] By an embodiment, the radially directed section comprises a proximal section is linked at its distal end to a distal section extending from said distal end in a general axial direction. Thus, the radially-directed section is one leg and the generally axially-directed section is another leg of a generally L-shaped distal section of fluid leakage path.

[0073] Said branching may give rise to backing-up leakage losses and build-up sealing of the fluid leakage paths.

[0074] The rotating elements and the fluid leakage paths on the two sides of the apparatus typically display a mirror symmetry about a plane of symmetry passing through the midline of the confined annular space and normal to the main axis.

[0075] By an embodiment, there is at least one, and often two or more, radial circumferential projections extending from the main rotor and / or from the auxiliary rotor into and rotatable within a congruent receiving recess of the stator, defining a tortuous leakage path of the radially directed section of the main rotor-associated fluid leakage path with sections defined about the at least one circumferential radial projection. Where there are two or more such projecting members, there may be at least one which has a radial span different than at least one other such member. Such projections may, typically (albeit not exclusively) have a tapering cross section extending from their base to a rounded rim. Centrifugal forces caused by rotor rotation, may cause accumulation of liquid droplets or mist at the rim region of such members, to form a film that impedes fluid leakage.

[0076] By an embodiment, the auxiliary rotors have an annular recess with a complementary curvature to that of the rounded apexes of the main rotor's annular members.

[0077] The proximal section (namely that closest to and directly extending from the branching point) of the radially directed section of the main rotor-associated fluid leakage path may have an angle vis-à-vis the axis such that the difference in heat-induced radial to axial expansion will cause a minimal change in the width of the gap between opposite congruent surfaces of the generally radially-directed section, e.g. a change in width that is less than about ±25% over the range of operating temperatures of the apparatus. By one example, the trajectory of said proximal section is about 81°.

[0078] It should be noted that similar considerations for the trajectory of said generally radially directed section may apply also to the generally radially directed sections of the fluid leakage paths that are defined about the circumferential radial projections.

[0079] The auxiliary rotor-associated fluid leakage path may have a segment at said branching that defines a general trajectory away from the auxiliary axis. The angle between the said segment of the auxiliary rotor-associated leakage paths and said outer face may be about 90°.

[0080] As already briefly noted above, axial centrifugal forces, caused by increasing rotational speed at the rim of a radial projection, such as at the apex of the main rotor's annular members (that are defined in said proximal section) causes fluid-carried components, which may be one or more of droplets, mist or other particles carried by the fluid, to accumulate at an apex of such segments. These components may accumulate at such apexes and yield the generation of a film at such locations.

[0081] The leakage paths may be configured such that the flow time of fluid from the annular confined space has a travel time through the leakage path (for example, in consequence of the branching) that is longer than the time for pressure change in an angular portion of the confined annular space in consequence of rotation of the projecting elements in said space.

[0082] The fluid leakage path may have an enlarged cross-section at a portion thereof opposite a rim of a circumferential projection. Also, one or more of leakage paths may be configured to have one or more section with a width different than other sections. The change in width may cause reduction of pressure of fluid flowing in the leakage path and a resulting slow-down in travel speed of fluid in the fluid leakage path.

[0083] The branching of the proximal section into the two distal sections section may be configured to cause reduction of pressure and a resulting slow-down in travel speed of fluid in said auxiliary rotor-associated leakage path and said proximal section. Additionally, a portion of one of the distal sections, e.g. a portion close to the intersection, may have a three-dimensional surface structure that is configured to increase friction of the fluid flowing in such section. This may be in the form of surface irregularities of the kind noted above.

[0084] The apparatus, particularly one embodying embodiment (2) may also comprise fluid seals in one or more of the fluid leakage paths. Theses seals may comprise a rotary sealing element fitted at an end of a fluid leakage path.

[0085] The apparatus of this aspect may be configured, by an embodiment, to operate as a compressor. It may also be configured, by another embodiment, to operate as an expander. By another embodiment the apparatus may be configured to operate both as a compressor and as an expander.

[0086] By one embodiment the main rotor is the fitted within the stator. By another embodiment the stator is the internal elements and fitted within the rotor that rotates about the stator.EMBODIMENTS

[0087] In the following sections embodiments will be listed in numbered passages intended to add onto the above description and not limit it in any way. The embodiments include such drafted in an independent format and other that dependent from such independent embodiments and may add additional elements to or modify embodiments from which they depend. Embodiments that are depended on one or more embodiments may also constitute elements that add to or modify other embodiments from which they do not depend.General1. An apparatus comprising:

[0089] a first part and a second part, one or both rotatable against one another about a main axis, defining axial and radial direction, with one or more auxiliary rotors fitted in said first part and rotatable about auxiliary axes parallel to said main axis, the rotations being synchronized and function jointly to compress, expand or pump a fluid within a confined annular space formed between the first and second parts; and

[0090] fluid leakage paths that are formed between congruent opposite faces formed between each two of the first part, the auxiliary rotor, and the second part; wherein

[0091] the fluid leakage path is configured with an active sealing element obstructing flow of fluid through said path upon rotation, the active sealing element comprises one or more of the following (1) and (2):

[0092] (1) a proximal section of the leakage path that extends from within the confined annular space and is formed between an arcuated peripheral surface of circumferential side walls of said space that are defined by said second part and between congruent surfaced of said first part, and

[0093] (2) an interrupted leakage path in which a proximal section of the fluid leakage path extending from within the confined annular space branches into two distal sections including (i) one or more auxiliary rotor-associated leakage paths, each extending in a general axial direction and formed between one of the auxiliary rotors and congruent surfaces of the first part, and (ii) a generally radially extending section of a second part-associated leakage path formed between a member of said second part and congruent surfaces of said first part.

[0094] 1A. The apparatus of embodiment 1, configured for operation as an expander and / or a compressor.Embodiment (1)2. An apparatus comprising:

[0096] a first part and a second part, one or both rotatable against one another about a main axis, defining axial and radial direction, with one or more auxiliary rotors fitted in said first part and rotatable about auxiliary axes parallel to said main axis, the rotations function jointly to compress, expand or pump a fluid within a confined annular space formed between the first and second parts; and comprising

[0097] fluid leakage paths that are formed between congruent opposite faces between each two of the first part, the one or more auxiliary rotor and the second part; wherein

[0098] said confined annular space has two circumferential side walls extending from said second part with an arcuated peripheral surface and said fluid leakage path has a proximal section of the leakage path that extends from within the confined annular space and is formed between the arcuated peripheral surface and congruent surface of the first part.

[0099] 3. The apparatus of embodiment 2, wherein said proximal section branching into two distal sections, consisting of:

[0100] an auxiliary rotor-associated leakage paths, each extending in a general axial direction and formed between one of the auxiliary rotors and congruent surfaces of the first part;

[0101] a generally radially directed section of a second part-associated leakage path.

[0102] 4. The apparatus of embodiment 3, wherein said radially directed section is linked at its distal end to a distal section of the second part-associated leakage path that extends from said distal end in a general axial direction.

[0103] 4A. The apparatus of embodiment 4, wherein the auxiliary rotor-associated leakage paths and the distal section of the second part-associated leakage path are radially separated with respect to the main axis.

[0104] 5. The apparatus of any one of embodiments 2 to 4A, wherein said annular members have an inner, generally radially oriented face defining side walls of the confined annular space, an outer face longer than the inner face extending in a generally radial direction defining said radially directed section.

[0105] 6. The apparatus of any one of embodiments 3 to 5, comprising at least one circumferential radial projection, radially extending from a rotating element into and rotatable within a congruent receiving recess of another element, defining a tortuous fluid leakage path with sections thereof extending in a general radial direction and linked to one another by a section extending over a rim of the at least one circumferential radial projection.

[0106] 7. The apparatus of embodiment 6, comprising two or more of such circumferential radial projections extending from the rotating element.

[0107] 8. The apparatus of embodiment 7, wherein the two or more circumferential radial projections comprise at least one which has a radial span different than at least one other circumferential radial projection.

[0108] 9. The apparatus of any one of embodiments 6 to 8, comprising at least one circumferential radial projection extending from the second part and rotatable within a congruent receiving recess of said first part, defining a second part-associated fluid leakage path with sections thereof defined about the circumferential projections.

[0109] 10. The apparatus of any one of embodiments 6 to 9, comprising at least one circumferential radial projection extending from the auxiliary rotor and rotatable within a congruent receiving recess of the first part, defining a tortuous auxiliary fluid leakage path with sections thereof defined about the circumferential projections.

[0110] 11. The apparatus of any one of embodiments 6 to 10, wherein one or more of the circumferential radial projections have a tapering cross section extending from their base to a rounded rim.

[0111] 12. The apparatus of any one of embodiments 6 to 11, wherein centrifugal forces caused by rotation of the rotating element, causes accumulation of liquid droplets at the rim of the circumferential radial projections.

[0112] 13. The apparatus of any one of embodiments 2 to 12, wherein the auxiliary rotors have an annular recess with a complementary curvature to that of said arcuated peripheral surface.

[0113] 14. The apparatus of any one of embodiments 2 to 13, wherein said generally radially directed section has a trajectory that the difference in heat-induced radial to axial expansion will cause a minimal change in the width of the gap between opposite congruent surfaces of said section.

[0114] 15. The apparatus of embodiment 14, wherein said general radially directed section is angled at about 80-81° with respect to the axis.

[0115] 16. The apparatus of any one of embodiments 3 to 15, wherein the auxiliary rotor-associated fluid leakage path has a proximal segment extending from said branching that defines a general trajectory away from the auxiliary axis.

[0116] 17. The apparatus of embodiment 16, wherein the angle between said segment and said second leg is about 90°.

[0117] 18. The apparatus of any one of embodiments 6 to 17, wherein axial centrifugal forces, caused by increasing rotational speed at the rim of a radial projection causes fluid-carried components and / or fluid condensation to accumulate at an apex of such segments.

[0118] 19. The apparatus of embodiment 18, wherein said fluid-carried components are droplets, mist or particles that generate a film at said sections.

[0119] 20. The apparatus of any one of embodiments 6 to 19, wherein the leakage paths are configured such that the flow time of fluid from the annular confined space has a travel time through the leakage path that is longer than the time intervals between pressure changes in any angular portions of the confined annular space in consequence of rotation of the projecting elements in said space.

[0120] 21. The apparatus of any one of embodiments 8 to 20, wherein the fluid leakage path has an enlarged cross-section at a portion thereof opposite the rim of a circumferential protruding member.

[0121] 22. The apparatus of any one of embodiments 2 to 21, wherein one or more of the leakage paths are configured to have one or more section with a width different than other sections.

[0122] 23. The apparatus of embodiment 22, wherein the leakage paths are configured to have one or more section with a width wider than other sections.

[0123] 24. The apparatus of embodiment 23, wherein a change in width is configured to cause reduction of pressure of fluid flowing in the leakage path and a resulting condensation of fluid at such section.

[0124] 25. The apparatus of any one of embodiments 3 to 24, wherein said branching is configured to cause reduction of pressure and a resulting slow-down in travel speed of fluid in said distal sections.

[0125] 26. The apparatus of embodiment 26, wherein a portion of one or both of the two distal sections has a three-dimensional surface structure that is configured to increase friction of the fluid flowing in such section.

[0126] 27. The apparatus of embodiment 26, wherein said surface structure comprises a surface imperfection.

[0127] 28. The apparatus of any one of embodiments 3 to 27, comprising one or more fluid seals in respective one or more of the distal sections of the fluid leakage paths.

[0128] 29. The apparatus of embodiment 28, wherein said seal comprises a rotary sealing element fitted at an end of a fluid leakage path.

[0129] 30. The apparatus of embodiment 28, wherein said rotary sealing comprises encapsulated ball bearings.

[0130] 31. The apparatus of any one of embodiments 2 to 30, configured to operate as a compressor and / or an expander.

[0131] 32. The apparatus of any one of embodiments 2 to 31, wherein said auxiliary rotor is a female rotor.

[0132] 33. The apparatus of embodiment 32, wherein the female rotor is disposed in an outer of the two first and second parts.

[0133] 34. The apparatus of any one of embodiments 2 to 33, wherein said first part is a stator and said second part is a main rotor.

[0134] 35. The apparatus of embodiment 34, wherein the stator comprises a frame that encompasses the main rotor.

[0135] 36. The apparatus of embodiment 34 or 35, wherein the main rotor comprises projecting elements that extend therefrom into the confined annular space that define in their rotation, jointly with portions of the one or more auxiliary rotors that adjacently project into said space, two or more chambers within said annular space that either expand, as the projecting elements recede in their rotation away from said portions or shrink as the projecting elements advance in their rotation towards said portions.

[0136] 37. The apparatus of embodiment 36, wherein

[0137] each of said portions comprises one or more recesses that are configured to receive said projecting elements, and

[0138] the rotations of the main and auxiliary rotors are synched to permit such reception as the projecting elements rotate transit such portion.

[0139] 38. An apparatus comprising:

[0140] a main rotor and a stator, the main rotor being rotatable about a main axis, the main rotor and the stator having respective annular rotor face and annular stator face that face one another and define between them a confined annular space;

[0141] two or more auxiliary rotors embedded in form-matching receiving spaces within the stator radially disposed about and each engaging the main rotor at a radial engagement sector, each being axially rotatable about an auxiliary axis parallel to the main axis and configured to rotate in synchrony with the main rotor and having an engaging portion with an engaging abutment that abuts into the annular confined space and is configured to roll at sealing fitness over the annular rotor face;

[0142] a plurality of projecting elements disposed on said annular rotor face and extend therefrom into said confined annular space and rotatable with the main rotor within the confine annular space, the projecting elements being configured to adjacently engage said annular stator face and to be adjacently received in an engaging groove formed on said engaging abutment, the projecting elements defining in their rotation, jointly with said engaging portions, transient and volume-changing compartments for fluid intake, compression, expansion or discharge;

[0143] the rotor having two annular members on two sides of the confined annular space, each with an inner face defining side walls of the confined annular space and outer face longer than the inner face extending to a generally axially extending base, the two walls connected by and arcuated section; and

[0144] fluid leakage paths that are formed between congruent opposite faces of each two of the main rotors, the auxiliary rotor and the stator; wherein

[0145] each of the fluid leakage paths comprise a proximal section extending in a general axial direction and formed between a generally arcuated face of one of the annular members and congruent surfaces of the stator.

[0146] 39. The apparatus of embodiment 38, wherein said proximal section branching into two distal sections, consisting of:

[0147] an auxiliary rotor-associated leakage paths, each extending in a general axial direction and formed between one of the auxiliary rotors and congruent surfaces of the stator; and

[0148] a generally radially directed section of a main rotor-associated leakage path.

[0149] 40. The apparatus of embodiment 39, wherein said radially directed section is linked at its distal end to a distal section of the main rotor-associated leakage path that extends from said distal end in a general axial direction.

[0150] 40A. The apparatus of embodiment 40, wherein the auxiliary rotor-associated leakage paths and the distal section of the main rotor-associated leakage path are radially separated with respect to the main axis.

[0151] 41. The apparatus of embodiment 39 or 40, wherein said branching giving rise to backing-up leakage losses and build-up sealing of the fluid leakage paths.

[0152] 42. The apparatus of any one of embodiments 39 to 41, comprising at least one main rotor projection, being a circumferential radial projection, radially extending from the main rotor into and rotatable within a congruent receiving recess of the stator, defining a tortuous distal section the main rotor-associated fluid leakage path extending in a general radial direction and linked to one another by a section extending over a rim the at least one circumferential radial projection.

[0153] 43. The apparatus of any one of embodiments 39 to 42, comprising at least one auxiliary rotor projection, being a circumferential radial projection extending from the auxiliary rotor and rotatable within a congruent receiving recess of the stator, defining a tortuous auxiliary fluid leakage path with sections thereof defined about the circumferential radial projections.

[0154] 43A. The apparatus of embodiment 43, comprising at least one of said main rotor projection and at least one of said auxiliary rotor projection.

[0155] 44. The apparatus of embodiment 42 or 43, comprising two or more circumferential radial projections extending from the main rotor into and rotatable within congruent receiving recesses of the stator.

[0156] 45. The apparatus of embodiment 44, wherein the two or more circumferential radial projections comprise at least one which has a radial span different than at least one other circumferential radial projection.

[0157] 46. The apparatus of any one of embodiments 39 to 45, comprising at least one circumferential radial projection extending from the auxiliary rotor and rotatable within a congruent receiving recess of the stator, defining a tortuous auxiliary fluid leakage path with sections thereof extending in a general radial direction and linked to one another by a section extending over a rim the main circumferential radial projections.

[0158] 47. The apparatus of embodiment 46, comprising two or more such circumferential radial projections extending from the auxiliary rotor into and rotatable within congruent receiving recesses of the stator.

[0159] 48. The apparatus of embodiment 47, wherein the two or more circumferential radial projections comprise at least one which has a radial span different than at least one other circumferential radial projection.

[0160] 49. The apparatus of any one of embodiments 42 to 48, wherein one or more of the circumferential radial projections have a tapering cross section extending from their base to a rounded tip.

[0161] 50. The apparatus of any one of embodiments 42 to 49, wherein centrifugal forces caused by rotor rotation, causes accumulation of liquid droplets at a rim of the circumferential radial projections.

[0162] 51. The apparatus of any one of embodiments 42 to 50, wherein the auxiliary rotors have an annular recess with a complementary curvature to that of said arcuated peripheral surface the main rotor's annular members.

[0163] 52. The apparatus of any one of embodiments 43 to 52, wherein said radially directed section has a trajectory such that the difference in heat-induced radial to axial expansion will cause a minimal change in the width of the gap between opposite congruent surfaces of said section.

[0164] 53. The apparatus of embodiment 52, wherein the outer face of the main rotor's annular member has a general trajectory angled at about 80-81° with respect to the axis.

[0165] 54. The apparatus of any one of embodiments 43 to 53, wherein the auxiliary rotor-associated fluid leakage path has a proximal segment at said branching that defines a general trajectory away from the auxiliary axis.

[0166] 55. The apparatus of embodiment 54, wherein the angle between said segment and said outer face is about 90°.

[0167] 56. The apparatus of any one of embodiments 43 to 55, wherein axial centrifugal forces, caused by increasing rotational speed at the rim of a radial projection causes fluid-carried components and / or fluid condensation to accumulate at region of said rim.

[0168] 57. The apparatus of embodiment 56, wherein said fluid-carried components are droplets, mist or particles that generate a film at said sections.

[0169] 58. The apparatus of any one of embodiments 39 to 57, wherein the leakage paths are configured such that the flow time of fluid from the annular confined space has a travel time through the leakage path that is longer than the time intervals between pressure change in any angular portions of the confined annular space in consequence of rotation of the projecting elements in said space.

[0170] 59. The apparatus of any one of embodiments 39 to 58, wherein the fluid leakage path has an enlarged cross-section at a portion thereof opposite the ridge.

[0171] 60. The apparatus of any one of embodiments 39 to 59, wherein one or more of leakage paths are configured to have one or more section with a width different than other sections.

[0172] 61. The apparatus of embodiment 61, wherein the leakage paths are configured to have one or more section with a width wider than other sections.

[0173] 62. The apparatus of embodiment 61, wherein a change in width is configured to cause reduction of pressure of fluid flowing in the leakage path and a resulting slow-down in travel speed of fluid in the fluid leakage path.

[0174] 63. The apparatus of any one of embodiments 39 to 62, wherein said branching is configured to cause reduction of pressure and a resulting slow-down in travel speed of fluid in said distal section.

[0175] 64. The apparatus of embodiment 63, wherein a portion of one or both of the two distal sections has a three-dimensional surface structure that is configured to increase friction of the fluid flowing in such section.

[0176] 65. The apparatus of embodiment 64, wherein said surface structure comprises one or more of abrasions, indentations, and protrusions.

[0177] 66. The apparatus of any one of embodiments 39 to 65, comprising one or more fluid seals in respective one or more of the distal sections of the fluid leakage paths.

[0178] 67. The apparatus of embodiment 66, wherein said seal comprises a rotary sealing element fitted at an end of a fluid leakage path.

[0179] 68. The apparatus of any one of embodiments 39 to 67, configured to operate as a compressor and / or expander.

[0180] 69. The apparatus of any one of embodiments 39 to 68, wherein the stator comprises a frame that encompasses the main rotor.Embodiment (2 )70. An apparatus comprising:

[0182] a first part and a second part, one or both rotatable against one another about a main axis, defining axial and radial direction, with one or more auxiliary rotors fitted in said first part and rotatable about auxiliary axes parallel to said main axis, the rotations being synchronized and function jointly to compress, expand or pump a fluid within a confined annular space formed between the first and second parts; and

[0183] fluid leakage paths that are formed between congruent opposite faces formed between each two of the first part, the auxiliary rotor, and the second part; wherein

[0184] the fluid leakage path is configured with an interrupted leakage path in which a proximal section of the fluid leakage path extending from within the confined annular space is branching into two distal sections including (i) one or more auxiliary rotor-associated leakage paths, each extending in a general axial direction and formed between one of the auxiliary rotors and congruent surfaces of the first part, and (ii) a generally radially extending section of a second part-associated leakage path formed between a member of said second part and congruent surfaces of said first part.

[0185] 71. The apparatus of embodiment 70, wherein said radially directed section is linked at its distal end to a distal section of the second part-associated leakage path that extends from said distal end in a general axial direction.

[0186] 71A. The apparatus of embodiment 71, wherein the auxiliary rotor-associated leakage paths and the distal section of the second part-associated leakage path are radially separated with respect to the main axis.

[0187] 72. The apparatus of any one of embodiments 70 to 71A, wherein said annular members have an inner, generally radially oriented face defining side walls of the confined annular space, an outer face longer than the inner face extending in a generally radial direction defining said radially directed section.

[0188] 73. The apparatus of any one of embodiments 70 to 72, comprising at least one circumferential radial projection, radially extending from a rotating element into and rotatable within a congruent receiving recess of another element, defining a tortuous fluid leakage path with sections thereof extending in a general radial direction and linked to one another by a section extending over a rim the at least one circumferential radial projection.

[0189] 74. The apparatus of embodiment 73, comprising two or more of such circumferential radial projections extending from the rotating element.

[0190] 75. The apparatus of embodiment 74, wherein the two or more circumferential radial projections comprise at least one which has a radial span different than at least one other circumferential radial projection.

[0191] 76. The apparatus of any one of embodiments 73 to 75, comprising at least one circumferential radial projection extending from the second part and rotatable within a congruent receiving recess of said first part, defining a second part-associated tortuous fluid leakage path with sections thereof defined about the circumferential projections.

[0192] 77. The apparatus of any one of embodiments 73 to 76, comprising at least one circumferential radial projection extending from the auxiliary rotor and rotatable within a congruent receiving recess of the first part, defining a tortuous auxiliary fluid leakage path with sections thereof defined about the circumferential projections.

[0193] 78. The apparatus of any one of embodiments 73 to 77, wherein one or more of the circumferential radial projections have a tapering cross-section extending from their base to a rounded rim.

[0194] 79. The apparatus of any one of embodiments 73 78, wherein centrifugal forces caused by rotation of the rotating element, causes accumulation of liquid droplets at the rim of the circumferential radial projections.

[0195] 80. The apparatus of any one of embodiments 70 to 79, wherein the auxiliary rotors have an annular recess with a complementary curvature to that of said arcuated peripheral surface.

[0196] 81. The apparatus of any one of embodiments 70 to 79, wherein said generally radially directed section has a trajectory such that the difference in heat-induced radial to axial expansion will cause a minimal change in the width of the gap between opposite congruent surfaces of said section.

[0197] 82. The apparatus of embodiment 81, wherein said general radially directed section is angled at about 80-81° with respect to the axis.

[0198] 83. The apparatus of any one of embodiments 70 to 82, wherein the auxiliary rotor-associated fluid leakage path has a proximal segment extending from said branching that defines a general trajectory away from the auxiliary axis.

[0199] 84. The apparatus of embodiment 83, wherein the angle between said segment and said second leg is about 90°.

[0200] 85. The apparatus of any one of embodiments 73 to 84, wherein axial centrifugal forces, caused by increasing rotational speed at the rim of a radial projection causes fluid-carried components and / or fluid condensation to accumulate at an apex of such segments.

[0201] 86. The apparatus of embodiment 85, wherein said fluid-carried components are droplets, mist or particles that generate a film at said sections.

[0202] 87. The apparatus of any one of embodiments 70 to 86, wherein the leakage paths are configured such that the flow time of fluid from the annular confined space has a travel time through the leakage path that is longer than the time interval between pressure changes in any angular portions of the confined annular space in consequence of rotation of the projecting elements in said space.

[0203] 88. The apparatus of any one of embodiments 70 to 87, wherein the fluid leakage path has an enlarged cross-section at a portion thereof opposite the apex of a circumferential protruding member.

[0204] 89. The apparatus of any one of embodiments 70 to 88, wherein one or more of the leakage paths are configured to have one or more section with a width different than other sections.

[0205] 90. The apparatus of embodiment 89, wherein the leakage paths are configured to have one or more section with a width wider than other sections.

[0206] 91. The apparatus of embodiment 90, wherein a change in width is configured to cause reduction of pressure of fluid flowing in the leakage path and a resulting condensation of fluid at such section.

[0207] 92. The apparatus of any one of embodiments 70 to 92, wherein said branching is configured to cause reduction of pressure and a resulting slow-down in travel speed of fluid in said distal sections.

[0208] 93. The apparatus of embodiment 92, wherein a portion of one or both of the two distal sections has a three-dimensional surface structure that is configured to increase friction of the fluid flowing in such section.

[0209] 94. The apparatus of embodiment 93, wherein said surface structure comprises a surface imperfection.

[0210] 95. The apparatus of any one of embodiments 70 to 94, comprising one or more fluid seals in respective one or more of the distal sections of the fluid leakage paths.

[0211] 96. The apparatus of embodiment 95, wherein said seal comprises a rotary sealing element fitted at an end of a fluid leakage path.

[0212] 97. The apparatus of embodiment 96, wherein said rotary sealing comprises encapsulated ball bearings.

[0213] 98. The apparatus of any one of embodiments 70 to 97, configured to operate as a compressor and / or an expander.

[0214] 99. An apparatus comprising:

[0215] a main rotor and a stator, the main rotor being rotatable about a main axis, the main rotor and the stator having respective annular rotor face and annular stator face that face one another and define between them a confined annular space;

[0216] two or more auxiliary rotors embedded in form-matching receiving spaces within the stator radially disposed about and each engaging the main rotor at a radial engagement sector, each being axially rotatable about an auxiliary axis parallel to the main axis and configured to rotate in synchrony with the main rotor and having an engaging portion with an engaging abutment that abuts into the annular confined space and is configured to roll at sealing fitness over the annular rotor face;

[0217] a plurality of projecting elements disposed on said annular rotor face and extend therefrom into said confined annular space and rotatable with the main rotor within the confine annular space, the projecting elements being configured to adjacently engage said annular stator face and to be adjacently received in an engaging groove formed on said engaging abutment, the projecting elements defining in their rotation, jointly with said engaging portions, transient and volume-changing compartments for fluid intake, compression, expansion or discharge;

[0218] the rotor having two annular members on two sides of the confined annular space, each with an inner face defining side walls of the confined annular space and outer face longer than the inner face extending to a generally axially extending base, the two walls connected by and arcuated section; and

[0219] fluid leakage paths that are formed between congruent opposite faces of each two of the main rotors, the auxiliary rotor and the stator; wherein

[0220] each of the fluid leakage paths comprise a proximal section extending in a general axial direction and formed between a generally arcuated face of one of the annular members and congruent surfaces of the stator; and wherein

[0221] said proximal section is branching into two distal sections including (i) one or more auxiliary rotor-associated leakage paths, each extending in a general axial direction and formed between one of the auxiliary rotors and congruent surfaces of the first part, and (ii) a generally radially extending section of a second part-associated leakage path formed between a member of said second part and congruent surfaces of said first part.

[0222] 100. The apparatus of embodiment 99, wherein said radially directed section is linked at its distal end to a distal section of the second part-associated leakage path that extends from said distal end in a general axial direction.

[0223] 100A. The apparatus of embodiment 100, wherein the auxiliary rotor-associated leakage paths and the distal section of the second part-associated leakage path are radially separated with respect to the main axis.

[0224] 101. The apparatus of any one of embodiments 99 to 100A, wherein said branching giving rise to backing-up leakage losses and build-up sealing of the fluid leakage paths.

[0225] 102. The apparatus of any one of embodiments 99 to 102, comprising at least one circumferential radial projection, radially extending from the main rotor into and rotatable within a congruent receiving recess of the stator, defining a tortuous distal section the main rotor-associated fluid leakage path extending in a general radial direction and linked to one another by a section extending over a rim the at least one circumferential radial projection.

[0226] 103. The apparatus of any one of embodiments 99 to 102, comprising at least one circumferential radial projection extending from the auxiliary rotor and rotatable within a congruent receiving recess of the stator, defining a tortuous auxiliary fluid leakage path with sections thereof defined about the circumferential radial projections.

[0227] 104. The apparatus of embodiment 102 or 103, comprising two or more circumferential radial projections extending from the main rotor into and rotatable within congruent receiving recesses of the stator.

[0228] 105. The apparatus of embodiment 104, wherein the two or more circumferential radial projections comprise at least one which has a radial span different than at least one other circumferential radial projection.

[0229] 106. The apparatus of embodiment 105, comprising two or more such circumferential radial projections extending from at least one of the rotors into and rotatable within congruent receiving recesses of the stator.

[0230] 107. The apparatus of embodiment 106, wherein the two or more circumferential radial projections comprise at least one which has a radial span different than at least one other circumferential radial projection.

[0231] 108. The apparatus of any one of embodiments 102 to 107, wherein one or more of the circumferential radial projections have a tapering cross section extending from their base to a rounded tip.

[0232] 109. The apparatus of any one of embodiments 102 to 108, wherein centrifugal forces caused by rotor rotation, causes accumulation of liquid droplets at a rim of the circumferential radial projections.

[0233] 110. The apparatus of any one of embodiments 102 to 109, wherein the auxiliary rotors have an annular recess with a complementary curvature to that of said arcuated peripheral surface the main rotor's annular members.

[0234] 111. The apparatus of any one of embodiments 99 to 110, wherein said radially directed section has a trajectory such that the difference in heat-induced radial to axial expansion will cause a minimal change in the width of the gap between opposite congruent surfaces of said section.

[0235] 112. The apparatus of embodiment 111, wherein the outer face of the main rotor's annular member has a general trajectory angled at about 80-81° with respect to the axis.

[0236] 113. The apparatus of any one of embodiments 99 to 112, wherein the auxiliary rotor-associated fluid leakage path has a proximal segment at said branching that defines a general trajectory away from the auxiliary axis.

[0237] 114. The apparatus of embodiment 113, wherein the angle between said segment and said outer face is about 90°.

[0238] 115. The apparatus of any one of embodiments 102 to 114, wherein axial centrifugal forces, caused by increasing rotational speed at the rim of a radial projection causes fluid-carried components and / or fluid condensation to accumulate at region of said rim.

[0239] 116. The apparatus of embodiment 115, wherein said fluid-carried components are droplets, mist or particles that generate a film at said sections.

[0240] 117. The apparatus of any one of embodiments 99 to 116, wherein the leakage paths are configured such that the flow time of fluid from the annular confined space has a travel time through the leakage path that is longer than the time interval between pressure changes in any angular portions of the confined annular space in consequence of rotation of the projecting elements in said space.

[0241] 118. The apparatus of any one of embodiments 99 to 117, wherein the fluid leakage path has an enlarged cross-section at a portion thereof opposite the ridge.

[0242] 119. The apparatus of any one of embodiments 99 to 118, wherein one or more of leakage paths are configured to have one or more section with a width different than other sections.

[0243] 120. The apparatus of embodiment 119, wherein the leakage paths are configured to have one or more section with a width wider than other sections.

[0244] 121. The apparatus of embodiment 120, wherein a change in width is configured to cause reduction of pressure of fluid flowing in the leakage path and a resulting slow-down in travel speed of fluid in the fluid leakage path.

[0245] 122. The apparatus of any one of embodiments 99 to 121, wherein said branching is configured to cause reduction of pressure and a resulting slow-down in travel speed of fluid in said distal section.

[0246] 123. The apparatus of embodiment 122, wherein a portion of one or both of the two distal sections has a three-dimensional surface structure that is configured to increase friction of the fluid flowing in such section.

[0247] 124. The apparatus of embodiment 123, wherein said surface structure comprises one or more of abrasions, indentations, and protrusions.

[0248] 125. The apparatus of any one of embodiments 99 to 124, comprising one or more fluid seals in respective one or more of the distal sections of the fluid leakage paths.

[0249] 126. The apparatus of embodiment 125, wherein said seal comprises a rotary sealing element fitted at an end of a fluid leakage path.

[0250] 127. The apparatus of any one of embodiments 99 to 126, configured to operate as a compressor and / or expander.

[0251] 128. The apparatus of any one of embodiments 99 to 127, wherein the stator comprises a frame that encompasses the main rotor.Embodiment (3)129. An apparatus comprising:

[0253] a first part and a second part, one or both rotatable against one another about a main axis, defining axial and radial direction, with one or more auxiliary rotors fitted in said first part and rotatable about auxiliary axes parallel to said main axis, the rotations being synchronized and function jointly to compress, expand or pump a fluid within a confined annular space formed between the first and second parts; and

[0254] fluid leakage paths that are formed between congruent opposite faces formed between each two of the first part, the auxiliary rotor, and the second part; wherein

[0255] the fluid leakage path comprises one or more sections that extend in the general radial direction and has a trajectory such that the difference in heat-induced radial to axial expansion will cause a minimal change in the width of said section.

[0256] 130. The apparatus of embodiment 129, wherein the one or more general radially directed sections is angled at about 80-81° with respect to the axis.

[0257] 131. The apparatus of embodiment 129 or 130, wherein one of said radially directed sections is a distal branch extending from a branching of a proximal section extending in a general axial direction into two distal sections including (i) one or more auxiliary rotor-associated leakage paths, each extending in a general axial direction and formed between one of the auxiliary rotors and congruent surfaces of the first part, and (ii) said a generally radially extending section that is formed between a member of said second part and congruent surfaces of said first part.

[0258] 132. The apparatus of any one of embodiments 129 to 131, wherein one of said radially directed sections is a radially directed section defined by at least one circumferential radial projection, radially extending from a rotating element into and rotatable within a congruent receiving recess of another element, defining a tortuous fluid leakage path with sections thereof extending in a general radial direction and linked to one another by a section extending over a rim the at least one circumferential radial projection

[0259] 133. An apparatus comprising:

[0260] a main rotor and a stator, the main rotor being rotatable about a main axis, the main rotor and the stator having respective annular rotor face and annular stator face that face one another and define between them a confined annular space;

[0261] two or more auxiliary rotors embedded in form-matching receiving spaces within the stator radially disposed about and each engaging the main rotor at a radial engagement sector, each being axially rotatable about an auxiliary axis parallel to the main axis and configured to rotate in synchrony with the main rotor and having an engaging portion with an engaging abutment that abuts into the annular confined space and is configured to roll at sealing fitness over the annular rotor face;

[0262] a plurality of projecting elements disposed on said annular rotor face and extend therefrom into said confined annular space and rotatable with the main rotor within the confine annular space, the projecting elements being configured to adjacently engage said annular stator face and to be adjacently received in an engaging groove formed on said engaging abutment, the projecting elements defining in their rotation, jointly with said engaging portions, transient and volume-changing compartments for fluid intake, compression, expansion or discharge;

[0263] the rotor having two annular members on two sides of the confined annular space, each with an inner face defining side walls of the confined annular space and outer face longer than the inner face extending to a generally axially extending base, the two walls connected by and arcuated section; and

[0264] fluid leakage paths that are formed between congruent opposite faces of each two of the main rotors, the auxiliary rotor and the stator; wherein

[0265] each of the fluid leakage paths comprise a proximal section extending in a general axial direction and formed between a generally arcuated face of one of the annular members and congruent surfaces of the stator; and wherein

[0266] the fluid leakage path comprises one or more sections that extend in the general radial direction and has a trajectory such that the difference in heat-induced radial to axial expansion will cause a minimal change in the width of said section.

[0267] 134. The apparatus of embodiment 133, wherein the one or more general radially directed sections is angled at about 80-81° with respect to the axis.

[0268] 135. The apparatus of embodiment 133 or 134, wherein one of said radially directed sections is a distal branch extending from a branching of a proximal section that extends in a general axial direction into two distal sections including (i) one or more auxiliary rotor-associated leakage paths, each extending in a general axial direction and formed between one of the auxiliary rotors and congruent surfaces of the first part, and (ii) said a generally radially extending section that is formed between a member of said second part and congruent surfaces of said first part.

[0269] 136. The apparatus of any one of embodiments 133 to 135, wherein one of said radially directed sections is a radially directed section defined by at least one circumferential radial projection, radially extending from a rotating element into and rotatable within a congruent receiving recess of another element, defining a tortuous fluid leakage path with sections thereof extending in a general radial direction and linked to one another by a section extending over a rim the at least one circumferential radial projectionBRIEF DESCRIPTION OF THE DRAWINGS

[0270] In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying schematic drawings, in which:

[0271] FIG. 1 is a partial isometric view of an apparatus in accordance with an embodiment of this disclosure with some portions of the stator being cut out for better view of the main rotor and two auxiliary rotors.

[0272] FIG. 2 is a cross-section through the auxiliary rotor with partial isometric view of the apparatus of FIG. 1.

[0273] FIG. 3 is an isometric view with a radial cut through the center of the recess that accommodates the auxiliary rotor of the apparatus of FIG. 1.

[0274] FIG. 4 shows the same isometric view after fitting of the auxiliary rotor.

[0275] FIG. 5 shows a radial cut through the apparatus of FIG. 1 at a portion between consecutive auxiliary rotors.

[0276] FIG. 6 is a similar view to that of FIG. 5 of an apparatus according to another embodiment.

[0277] FIG. 7 shows an apparatus according to another embodiment of this disclosure in an isometric and partial axial cut-out view.

[0278] FIG. 8 shows and isometric and partial axial cut-of view of apparatus according to another embodiment of this disclosure.

[0279] FIG. 9 shows and isometric and partial axial cut-of view of apparatus according to another embodiment of this disclosure.

[0280] FIG. 10 is an isometric and partial radial and axial cut-out view of an apparatus according to yet another embodiment of this disclosure.

[0281] FIG. 11 is an isometric view of an apparatus according to yet another embodiment of this disclosure, illustrating the gearing system.DETAILED DESCRIPTION OF EMBODIMENTS

[0282] In the following description some illustrative and non-limiting embodiments will be described with reference to the annexed drawings.

[0283] In describing the different embodiments, use will be made with reference numerals where the first digit is an indicator of the consecutive number of the embodiment and the subsequent reference numerals relate to the element number. Thus, for example, element 102 relates to the stator of the apparatus of the first embodiment illustrated in FIGS. 1-5, while element 302 relates to the stator of the second embodiment illustrated in FIG. 6. In other words, elements that are numbered by the same reference numeral save for the first digit serve the same function. In describing the different embodiments, the description may skip elements that have already been described in connection with other embodiments and the reader is referred to the description of previously described embodiment for an understanding of the structure and / or function of such elements.

[0284] Reference is first made to FIGS. 1-5, where an apparatus 100 according to an embodiment of this disclosure is schematically illustrated in several views. Apparatus 100 includes a stator 102, a main rotor 104 and a plurality of auxiliary rotors 106 (6 auxiliary rotors in this exemplary embodiment; however the number of auxiliary rotors may be any number dictated by design and engineering considerations). The rotor is rotatable about a main axis, represented, in FIG. 1, by a dashed line 108. In this embodiment the rotor is encompassed within the stator. In other embodiments this may be reversed as illustrated below in FIG. 10. The stator 102 is illustrated in the drawing schematically as an annular ring. However, as can be appreciated the stator may also be embodied as a larger frame having any shape as dictated by engineering or other considerations. Similarly, the main rotor 104 is shown schematically as a rotating ring-like element. However, as can also be appreciated, this rotor may have a variety of other configurations, for example the hollow space within the rotor may be filled or the rotor may have an integral structure for connecting to an axle, etc.

[0285] In general, the apparatus may be configured to operate as a compressor, in which case the main rotor 104 may be coupled to a motor, e.g. an electric motor, or may be configured to operate as an expander, in which case the main rotor 104 may be coupled to an energy generator, e.g. an electric generator.

[0286] The stator 102 and the rotor 104 have respective annular stator face 110 and annular rotor face 112 that face one another and define between them a confined annular space 114 (best seen in FIGS. 3 and 5).

[0287] The plurality of auxiliary rotors 106 are embedded in a form-matching receiving recesses 116 (seen in FIG. 3) within the stator 102 that define a radial engagement sector between the auxiliary rotors and the main rotor. Each of the auxiliary rotors 106 is axially rotatable about an auxiliary axis, represented by a dashed line 118 in FIG. 4, that is parallel to the main axis 108 and configured to rotate in synchrony with the main rotor 102. The synchrony may be achieved through a gearing system, such as that shown in FIG. 11. The auxiliary rotors 106 have each an engaging portion 120 with an engaging abutment 122 that abuts into the confined annular space 114 and is configured to roll at close engagement over the annular rotor face 112, flanked by two annular recesses 123A,123B that are configured to closely engage with annular members 124A,124B that are formed on the two sides and define side walls of the confined annular space 114.

[0288] A plurality of projecting elements 126 (one of which is seen in FIG. 1) are disposed on said annular rotor face 112 and extend therefrom into the confined annular space 114 and rotatable with the main rotor 104 within the confine annular space. The projecting elements 126 are configured to closely engage the annular stator face 110 and to be closely received in an engaging groove 128 formed on the engaging abutment 122 of the auxiliary rotor 106. The projecting elements 126 define in their rotation, jointly with the engaging portions 120, transient and volume-changing compartments for fluid intake, compression, expansion or discharge, as known per se. As also known per se, the confined annular apace has ingress ports for introducing fluid into the confined annular apace and has egress ports for fluid discharge out of the confined annular apace; and has a valving arrangement to permit timely fluid charge and fluid discharge into and out of the confined annular apace through the respective ingress and egress ports.

[0289] Each of two annular members 124A,124B has a respective inner face 128A,128B defining side walls of the confined annular space 114. The outer faces 130A, 130B of respective annular members 124A,124B are longer than the inner faces and extend in a generally radial direction to face bases 132A,132B. The annular members 124A, 124B have peripheral arcuated faces 141A,141B, that, as generally explained above, exert, during their rotations centrifugal forces that lead to the deposit of a film at an apex thereof providing a seal that hinders and reduces leakage losses of fluid from within the confined annular chamber. This arcuated section is presented to be one having a semi-circular cross-section, but it may also have a cross section that defines part of an ellipse, a polygonal cross-sectional shape or generally the arcuated section may trace any kind of spline.

[0290] The bases 132A,132B are a first portion of a generally axially oriented fluid leakage path, which in this exemplary embodiment, is a tortuous path with generally radial sections defined by annular radial projections 134A,134B.

[0291] The apparatus 100 of this embodiment has a mirror symmetry about a plane normal to the axis 108 and that passes in the middle of the confined annular space 114 in between the two annular members 124A,124B. While a mirror symmetry of all functional elements of the apparatus (the functional elements comprising the rotors, portions of the stator that engage the rotors and the fluid leakage paths defined therebetween) is a typical case for engineering an apparatus according to this disclosure, and indeed all apparatuses exemplified herein have such a mirror symmetric design, such as mirror symmetry is not the exclusive manner of designing an apparatus according to this disclosure. For example, for various design and engineering considerations, the auxiliary rotors may not have a mirror symmetry, whereby the auxiliary rotor-associated leakage path on one side may be different than the other. By another example, the stator may have an overall non-symmetric design, e.g. in view of engineering consideration for coupling the apparatus to other extraneous elements. Additionally, the rotor may be coupled to a motor or a generator at one side which by itself induces an asymmetry (although the auxiliary rotors and the leakage paths, in such a case my still have a mirror-symmetric design).

[0292] In order to permit rotation of the rotating elements, there must be a clearance between the different elements and such clearance, as small as it is, would create a fluid leakage paths between congruent opposite faces formed between the main rotor and each auxiliary rotor, between the main rotor and the stator and between each of the auxiliary rotors and the stator. Such leakage path 140A, 140B are schematically marked by winding arrows in FIG. 5, showing the lateral flow direction of leaking fluid from within the confined annular space 114 towards the two sides 142A,142B of the apparatus. This fluid leakage path has a proximal section 141A,141B that passe over arcuated section 136A,136B. The rotor 104, rotating about the axis 108 generates centrifugal forces that cause fluid droplets and mists to accumulate at the apex of the arcuated section 136A,136B yielding the formation of a film that impedes flow of leaking fluid through the leakage path 140A,140B. The leakage path 140A,140B branches at into two distal sections relative to the branching point 154A,154B, these including a radially directed section 143A,143B that extends along the outer face 130A,130A and is link to a distal, generally axial tortuous section with generally radial section defined by and extending over the rims of annular radial projections 134A,134B. Similarly, as described above in connection with the proximal section 141A,141B, the centrifugal forces cause the generation of a film at the rim of annular radial projections 134A,134B impeding flow of leakage fluid through fluid leakage path 140A,140B. Thus, for fluid leakage path 140A,140B there are several active fluid scaling mechanisms operating together, one defined by the arcuated section 136A,136B, and the other by annular radial projections 134A,134B and one by the branching at branchpoint 154A,154B.

[0293] Auxiliary rotor-associated leakage paths 144A,144B extend in a general axial direction and formed between each one of the auxiliary rotors 106 and congruent surfaces of the stator 102. The auxiliary rotor-associated leakage paths 144A,144B extend along a tortuous path over a circumferential radial projection 146A,146B.

[0294] A main rotor-associated leakage path consisting of the proximal section 141A, 141B a radially directed section 150A,150B and a distal segment 152A,152B. The proximal section 141A,141B extends from the confined annular space 114 (not seen in FIG. 2 given where the cross-section was made) until the branch point 154A,154B in a general axial direction and is formed between said arcuated section 136A,136B and congruent faces of the stator. The radially directed section 150A,150B extends generally radially from the intersection 154A,154B and is defined by said outer face and the congruent surface of the stator. The distal segment 152A,152B extends in a general axial direction along a tortuous path over a circumferential radial projection 134A,134B between faces of the main rotor and congruent faces of the stator.

[0295] It is of note that the congruent face defining said proximal section 140A,140B of the main rotor-associated leakage path, as seen in FIG. 2, is that of recesses 123A,123B but this is only at this radial cross-sectional location where recesses 123A, 123B touch annular sections 136A,136B. In other radial locations the congruent opposite faces are those of the stator. It is also to be noted that in this cross-section the engaging abutment 122 closely engages the annular rotor face 112 while in other locations the engaging abutment 122 there is a clearance between the engaging abutment 122 and the annular rotor face 112, as can be seen, for example, in FIG. 5. This cross-section was chosen for illustrative consideration as it clearly shows all leakage paths. It should be noted, also, that the intersection, occurs along a distance that is defined by shoulders 158A,158B lateral to recesses 123A,123B.

[0296] In the embodiment of FIGS. 1-5 there is one (on each side) main rotor circumferential projection 134A,134B and one auxiliary rotor circumferential projection 146A,146B. In other embodiments there may be 2, 3 or even more such projections, being all of the same radial extension, being different to one another in their radial extension, two being of the same radial span and one being different, etc.

[0297] The main rotor circumferential projection 134A,134B and the auxiliary rotor circumferential projection 146A,146B have each a tapering cross section extending from their base to a rounded tip. While typical, this is not the exclusive configuration for such circumferential projection. Also, the rounded tip of the projections may assume a circular cross-section, an elliptical a polygonal or generally have that shape of any spline.

[0298] The radially directed section 150A,150B extends generally radially, albeit angled in a trajectory towards the main axis that is designed such that the difference in heat-induced radial to axial expansion will cause a minimal change in the width of the radially directed section, e.g. a change in width that is less than about ±25% over the range of operating temperatures of the apparatus. The trajectory of said radially directed section 150A,150B defined by the relatively straight major portion of the outer face 130A,130B of annular member 124A,124B, in this embodiment is about 81°.

[0299] As can be seen, the first segment 158A,158B of the auxiliary rotor-associated fluid leakage path 144A,144B that extends from intersection 154A,154B, defines a general trajectory away from the auxiliary axis 118. The angle between segment 158A,158B and said radially directed section 150A,150B is about 90°.

[0300] As already briefly noted above, axial centrifugal forces, caused by increasing rotational speed at the rim of a circumferential radial projections or at the apex of the arcuated sections arcuated sections 136A,136B causes fluid-carried components, which may be one or more of droplets, mist or other particles carried by the leaking fluid, to accumulate at such apex or rim region. These components may accumulate at such apexes and causer the formation of a film at such locations.

[0301] The leakage paths may be configured such that the flow time of leaking fluid from the annular confined space has a travel time through the leakage path (for example, in consequence of the branching) that is longer than the time for pressure change in an angular portion of the confined annular space in consequence of rotation of the projecting elements in said space. The fluid leakage path may be designed to have an enlarged cross-section at a portion thereof opposite a ridge of a circumferential projection, by designing one or both of the congruent surfaces to have a small deviation from the general trajectory or designing one of the congruent surfaces to have a section that slightly deviates from full congruency. The change in width may cause reduction of pressure of the leaking fluid flowing in the fluid leakage path and a resulting slow-down in travel speed of leaking fluid in the fluid leakage path.

[0302] The branching at branch points 154A, 154B may cause the fluids to flow cyclically in the forward our counter direction between the branches causing the fluid with the leakage path to remain there neither escaping nor entering the confined annular space 114. The branching of the leakage paths at the branch points 154A,154B into the auxiliary rotor-associated leakage path 144A,144B and the radially directed section 150A,150B may also be designed to cause reduction of pressure and a resulting slow-down in travel speed of the leaking fluid in said auxiliary rotor-associated leakage path and said radially directed section. Additionally, a section of the auxiliary rotor-associated leakage path 144A,144B and / or the radially directed section 150A, 150B, typically a section close to the intersection 154A,154B, may have a three-dimensional surface structure that is configured to increase friction of the leaking fluid flowing in such section. This may be in the form of surface irregularities such as surface abrasion, small indentations or small projections. Such surface irregularities are usually at a sub-millimeter level.

[0303] FIG. 6 shows an apparatus 200 according to another embodiment of this disclosure where the fluid leakage path has an enlarged cross-section at a portion thereof 235,235B opposite a ridge of a circumferential projection 234A,234B. These portions of the leakage path with an enlarged cross-section, will cause a local reduction of the pressure of the leaking fluid flowing through the fluid leakage path, causing condensation and deposit of a fluid film at such a portion, that acts as a seal impeding flow of leaking fluid through the fluid leakage path.

[0304] FIG. 7 shows an apparatus 300 according to another embodiment of this disclosure. The main difference between apparatus 300 and apparatus 100 of FIGS. 1-5, being in that (1) rather than a single circumferential radial projection 146A,146B formed on auxiliary rotor 106 in apparatus 100, auxiliary rotor 306 of apparatus 300 has one major circumferential radial projection 346A,346B and three minor ones 347A,347B having a smaller radial span than that of the major circumferential radial projection 346A,346B, with an increasing radial span from that closest to circumferential radial projection 346A,346B to the most lateral one of the three; and in that (2) rather than a single circumferential radial projection 156A,156B formed on main rotor 104 in apparatus 100, main rotor 306 of apparatus 300 has three circumferential radial projections 357A,357B descending in their radial from the largest close to outer face 330A,330B to the more lateral ones.

[0305] FIG. 8 shows an apparatus 400 according to another embodiment of this disclosure. In apparatus 400 there are no circumferential radial projections on both the main rotor 404 and the auxiliary rotor 406. However, the branching of the proximal segment at leakage path at the branchpoint into two distal leakage paths that are distinct from one another, permit to fit a rotary seal 460A,460B at the end of the main rotor-associated leakage path to further seal this leakage path and thereby blocking passage of any remaining leaking fluid. Similarly rotary seals 462A,462B can also be fitted at the end of the auxiliary rotor-associated leakage path and seals this leakage path by impeding flow of any remaining leaking fluid through this leakage path and thereby blocking passage of any remaining leaking fluid.

[0306] FIG. 9 shows an apparatus 500 according to another embodiment of this disclosure. This apparatus has an overall design like that of the apparatus 100 of FIGS. 1-5 with added sealing elements 560A,560B and 562A,562B that are like the sealing elements of apparatus 400.

[0307] FIG. 10 shows an apparatus 600 according to another embodiment of this disclosure. Whereas in all previous embodiments described above the stator was the peripheral member and the rotor was encompassed within the stator, this is reversed in apparatus 600, namely the stator 602 is the inner of these two members and the rotor rotates about the stator.

[0308] Reference is now being made to FIG. 11, showing an apparatus 700 according to another embodiment of this disclosure. Twelve auxiliary rotors 706 are disposed in the stator 702. The main rotor 704 is coupled to a gear wheel 705 that is geared to the cogged end portion 707 of auxiliary rotor 706. Through such gearing the main rotor 704 and the auxiliary rotors 706 may rotate in a synchronous manner.

Claims

1-32. (canceled)33. An apparatus comprising:a main rotor and a stator, the main rotor being rotatable against the stator about a main axis defining axial and radial direction, the main rotor and the stator having respective annular rotor face and annular stator face that face one another and define between them a confined annular space; andone or more auxiliary rotors fitted in said main rotor and rotatable about auxiliary axes parallel to said main axis, the rotations being synchronized and function jointly to compress, expand or pump a fluid within the confined annular space formed between the main rotor and the stator; andfluid leakage paths that are formed between congruent opposite faces of each two of the main rotors, the auxiliary rotor and the stator; characterized in that:physical configuration of at least one of said fluid leakage path is configured with an active sealing element obstructing flow of fluid through said path upon rotation, the active sealing element comprisesan interrupted leakage path in which a proximal section of the fluid leakage path extending from within the confined annular space branches into two distal sections including (i) one or more auxiliary rotor-associated leakage paths, each extending in a general axial direction and formed between one of the auxiliary rotors and congruent surfaces of the first part, and (ii) a generally radially extending section of a stator-associated leakage path formed between a member of said stator and congruent surfaces of said main rotor.

34. The apparatus of claim 33, wherein said radially directed section is linked at its distal end to a distal section of the main rotor-associated leakage path that extends from said distal end in a general axial direction.

35. The apparatus of claim 33, wherein the auxiliary rotor-associated leakage paths and the distal section of the main rotor-associated leakage path are radially separated with respect to the main axis.

36. The apparatus of claim 33, comprising one or both ofat least one of said projecting elements, being a circumferential radial projection, radially extending from the main rotor into and rotatable within a congruent receiving recess of the stator, defining a tortuous distal section the main rotor-associated fluid leakage path extending in a general radial direction and linked to one another by a section extending over a rim the at least one circumferential radial projection, andat least one auxiliary rotor projection, being a circumferential radial projection extending from the auxiliary rotor and rotatable within a congruent receiving recess of the stator, defining a tortuous auxiliary fluid leakage path with sections thereof defined about the circumferential radial projections.

37. The apparatus of claim 36, comprising at least one of said main rotor projection and at least one of said auxiliary rotor projection.

38. The apparatus of claim 36, wherein one or more of the circumferential radial projections have a tapering cross section extending from their base to a rounded tip.

39. The apparatus of claim 33, wherein the outer face of the main rotor's annular member has a general trajectory angled at about 80-81° with respect to the axis.

40. The apparatus of claim 33, wherein the auxiliary rotor-associated fluid leakage path has a proximal segment at said branching that defines a general trajectory away from the auxiliary axis.

41. The apparatus of claim 40, wherein the angle between said segment and said outer face is about 90°.

42. The apparatus of claim 33, comprising one or more fluid seals in respective one or more of the distal sections of the fluid leakage paths.

43. The apparatus of claim 33, for use as one or both of a compressor or an expander.

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