Optimized energy recovery device

Abstract

A Roots device may include a housing assembly having a first opening and a second opening in fluid communication with an interior cavity; a pair of identical rotors oppositely disposed within the housing interior cavity, each rotor of the pair having a longitudinal axis and a plurality of lobes, each lobe defining an end face extending between a first longitudinal side of the rotor lobe and a second longitudinal side of the rotor lobe; and a recessed port defined within the housing assembly and axially spaced from an end face of the rotor lobes, the recessed port in fluid communication with a first longitudinal side of one of the rotor lobes with a second longitudinal side of the rotor lobes such that the housing first opening is in fluid communication with the housing second opening. The apparatus may also be provided with an inlet nozzle structure in fluid communication with the first opening, the inlet nozzle tapering toward the first opening and configured such that a nozzle rate of working fluid through the nozzle is at least equal to a rotor engagement axial directing rate.

Description

[0001] Related Applications

[0002] This application was filed as a PCT international patent application on April 14, 2023, and claims the benefit and priority of U.S. Provisional Application No. 63 / 363,024 filed on April 14, 2022, U.S. Provisional Application No. 63 / 336,483 filed on April 29, 2022, and U.S. Provisional Application No. 63 / 493,606 filed on March 31, 2023, the entire contents of each of these applications are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to Roots-type devices used in expander and compressor applications. Background Art

[0004] Roots expanders use the energy in the fluid flow applied to the rotor surface to produce rotational work. By increasing the time in the device, the pressure difference applied to the rotor can improve the efficiency of the device. One way to increase this "time" is to make the rotor twist beyond the ideal twist. However, the traditional method of designing Roots expander rotors is limited by hardware constraints. Improvements are desired. Summary of the invention

[0005] In general, the present disclosure relates to a positive displacement fluid expander. The present disclosure describes various aspects, including but not limited to the following aspects.

[0006] In one aspect of the present disclosure, a volumetric fluid expander is provided for producing useful work by expanding a working fluid. In one application, the volumetric fluid expander can be used to recover waste energy from a power plant, such as waste heat energy from a fuel cell or an internal combustion engine. The power plant can be arranged in a vehicle, or can be arranged in a stationary application, such as when the power plant is used as a generator. In one possible configuration and by way of non-limiting example, the volumetric fluid expander is used in an exhaust gas recirculation system of an internal combustion engine.

[0007] In one example, the working fluid is all or part of an exhaust stream from an internal combustion engine or a fuel cell. In another example, the working fluid is separated from and heated by a waste heat stream from an internal combustion engine or a fuel cell, as disclosed in International Publication No. WO 2013 / 130774, which is incorporated herein by reference. WO 2013 / 130774 discloses that the working fluid can be used in a Rankine cycle, wherein the working fluid can be a solvent, such as ethanol, n-pentane, or toluene.

[0008] A Roots-type device may include: a housing assembly having a first opening and a second opening in fluid communication with an internal cavity; a pair of identical rotors, the pair of rotors being relatively arranged in the housing internal cavity, each of the pair of rotors having a longitudinal axis and a plurality of lobes, each of the lobes defining an end surface extending between a first longitudinal side of the rotor lobe and a second longitudinal side of the rotor lobe; and a recessed port defined in the housing assembly and axially spaced from the end surfaces of the rotor lobes, the recessed port fluidically communicating the first longitudinal side of one of the rotor lobes with the second longitudinal side of the rotor lobe, so that the first housing opening is in fluid communication with the second housing opening.

[0009] In some examples, the housing assembly includes a main housing and a support plate secured to the main housing, wherein the recessed port is defined within the support plate.

[0010] In some examples, an end surface of at least one rotor lobe faces the recessed port at all rotational angles of the rotor.

[0011] In some examples, the twist angle of each rotor of the pair of rotors is less than or equal to an ideal twist angle of the rotor defined without the recessed port.

[0012] In some examples, each rotor in the pair of rotors has three lobes.

[0013] In some examples, the rotor is axially located between the housing first opening and the recessed port.

[0014] In some examples, the pair of rotors are each supported by a rotatable shaft located between the second opening of the housing and the recessed port.

[0015] In some examples, the pair of rotors are each supported by a shaft having a longitudinal axis aligned along a first longitudinal plane, wherein the housing outlet is located on a first side of the first longitudinal plane, and wherein the recessed port is located on a second side of the first longitudinal plane.

[0016] In some examples, the first opening is orthogonal to the longitudinal axis of the rotor.

[0017] In some examples, the second opening is parallel to the longitudinal axis of the rotor.

[0018] A Roots-type device may include a pair of rotors and a housing assembly in which the rotors are disposed, the housing assembly having a first opening and a second opening, and a recessed port that fluidly connects the first housing opening to the second housing opening.

[0019] In some examples, the recessed port is located at a first axial end of the pair of rotors.

[0020] In some examples, the recessed port defines a leakage path about an axial end of at least one lobe of the pair of rotors at least some rotational positions of the pair of rotors.

[0021] In some examples, the recessed port fluidly connects a first longitudinal side of one of the rotor lobes with a second longitudinal side of the rotor lobe.

[0022] In some examples, the housing assembly includes a main housing and a support plate secured to the main housing, and wherein the recessed port is defined within the support plate.

[0023] In some examples, an end surface of at least one lobe of the pair of rotors faces the recessed port at all rotation angles of the rotors.

[0024] In some examples, the twist angle of each rotor of the pair of rotors is less than or equal to an ideal twist angle of the rotor defined without the recessed port.

[0025] In some examples, each rotor in the pair of rotors has three lobes.

[0026] In some examples, the rotor is axially located between the housing first opening and the recessed port.

[0027] In some examples, the pair of rotors are each supported by a rotatable shaft located between the second opening of the housing and the recessed port.

[0028] In some examples, the pair of rotors are each supported by a shaft having a longitudinal axis aligned along a first longitudinal plane, wherein the housing outlet is located on a first side of the first longitudinal plane and the recessed port is located on a second side of the first longitudinal plane.

[0029] In some examples, the first opening is orthogonal to the longitudinal axis of the rotor.

[0030] In some examples, the second opening is parallel to the longitudinal axis of the rotor.

[0031] A support plate for a Roots-type device may include: a body extending from a first side to a second side along a longitudinal axis; a pair of cavities for supporting a bearing and a seal assembly, the cavities extending between the first side and the second side of the body; a major surface at least partially defining the first side and being orthogonal to the longitudinal axis; and a recessed area at least partially defining the first side and being axially recessed from the major surface in a direction toward the second side, the recessed area being configured to provide a leakage path for the Roots-type device.

[0032] In some examples, the recessed area is located entirely on a first side of a plane centered through the pair of cavities and extending parallel to the longitudinal axis.

[0033] In some examples, the recessed area extends to an outer edge of the body.

[0034] In some examples, the body includes a second recessed region that at least partially defines the first side and is axially recessed from the major surface in a direction toward the second side, the second recessed region being completely located on the second side of the plane.

[0035] In some examples, the recessed area is V-shaped.

[0036] A method of retrofitting a supercharger for an expander application may include providing a supercharger having a pair of rotors and a housing assembly in which the rotors are disposed, the housing assembly having a first opening and a second opening; removing a first support plate of the supercharger; and installing a second support plate to the supercharger, the second support plate including a recessed port that fluidically connects the first housing opening to the second housing opening.

[0037] A Roots-type device may include: a housing assembly having a first opening and a second opening in fluid communication with an internal cavity; a pair of identical rotors arranged relative to each other in the internal cavity, each rotor of the pair of rotors having a longitudinal axis and a plurality of lobes, wherein the rotors mesh with each other and define a rotor meshing axial lead velocity when rotated; and an inlet nozzle structure in fluid communication with the first opening, the inlet nozzle structure tapering toward the first opening and configured such that a nozzle velocity of a working fluid passing through the inlet nozzle structure is at least equal to the rotor meshing axial lead velocity.

[0038] In some examples, the inlet nozzle structure is oriented substantially parallel to the longitudinal axis.

[0039] In some examples, the inlet nozzle structure is oriented at an oblique angle to the longitudinal axis.

[0040] In some examples, the cross-sectional area of ​​the nozzle structure is reduced by at least 20%.

[0041] In some examples, the volumetric flow rate through the inlet nozzle structure is increased by at least a factor of two.

[0042] In some examples, each rotor includes four lobes.

[0043] In some examples, the nozzle velocity is greater than the rotor engagement axial lead velocity.

[0044] In some examples, the nozzle velocity is at least 1.1 times the rotor mesh axial lead velocity.

[0045] In some examples, the nozzle velocity is at least 1.6 times the rotor mesh axial lead velocity.

[0046] Additional objects and advantages will be set forth in part in the description that follows and in part will be apparent from the description or may be learned by practicing the teachings presented herein. These objects and advantages will also be realized and obtained by means of the elements and combinations particularly pointed out in the appended claims. It should be understood that the foregoing general description and the following detailed description are merely exemplary and illustrative and do not limit the claimed invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a perspective view of a Roots-type device having various features exemplifying aspects in accordance with principles of the present disclosure.

[0048] Figure 2 yes Figure 1 A second perspective view of a Roots-type device is shown.

[0049] Figure 3 yes Figure 1 A top view of a Roots-type device is shown.

[0050] Figure 4 yes Figure 1 A bottom view of a Roots-type device is shown.

[0051] Figure 5 yes Figure 1 A first side elevation view of a Roots-type device is shown.

[0052] Figure 6 yes Figure 1 A second side view of a Roots-type device is shown.

[0053] Figure 7 yes Figure 1 A first end view of a Roots-type device is shown.

[0054] Figure 8 yes Figure 1 A second end view of a Roots-type device is shown.

[0055] Fig. 9 It is along Figure 7 The line 9-9 in the Figure 1 A first cross-sectional view of a Roots-type device is shown.

[0056] Fig.10 It is along Figure 7 The line 10-10 in Figure 1 A second cross-sectional view of a Roots-type device is shown.

[0057] Fig.11 It is along Figure 5 The line 11-11 in Figure 1 A third cross-sectional view of a Roots-type device is shown.

[0058] Fig.12 yes Figure 1 A partial perspective view of a Roots-type device is shown, illustrating the leakage path within the device.

[0059] Fig.13 yes Figure 1 A perspective view of a support plate of a Roots-type device is shown.

[0060] Fig.14 yes Fig.13 A second perspective view of the support plate is shown.

[0061] Fig.15 yes Fig.13 A first end view of a support plate is shown.

[0062] Fig.16 yes Fig.13 A second end view of the support plate is shown.

[0063] Fig.17 It is along Fig.16 The line 17-17 in Fig.13 A cross-sectional view of the support plate is shown.

[0064] Fig.18 yes Figure 1 A perspective view of the rotor of a Roots-type device is shown.

[0065] Fig.19 yes Fig.18 An end view of the rotor is shown.

[0066] Fig. 20 It is available with Figure 1 A perspective view of a second example of a rotor for use with a Roots-type device is shown.

[0067] Fig.21 yes Fig. 20 An end view of the rotor is shown.

[0068] Fig. 22 yes Figure 1 A schematic cross-sectional view of a Roots-type expander is shown.

[0069] Fig.23 yes Figure 1 A schematic perspective view of a variant of a Roots-type expander is shown.

[0070] Fig.24 yes Figure 1 A schematic cross-sectional side view of a variation of a Roots-type expander is shown.

[0071] Fig.25is a side view of a second embodiment of a positive displacement fluid expander having various features exemplifying aspects in accordance with principles of the present disclosure.

[0072] Fig.26 yes Fig.25 A cut-away side view of a positive displacement fluid expander is shown.

[0073] Fig. 27 yes Fig.25 A cut-away side view of a portion of a fluid expander is shown.

[0074] Fig.28 yes Fig. 27 A top view of a fluid expander section is shown.

[0075] Fig.29 yes Fig. 27 A perspective view of a portion of a fluid expander is shown.

[0076] Fig.30 yes Fig.25 A perspective view of the rotor of a fluid expander is shown.

[0077] Fig.31 yes Fig.25 A schematic perspective view of a positive displacement fluid expander is shown.

[0078] Fig.32 It shows Figure 1 , 23 24 are schematic diagrams of the geometric parameters of the rotor of the positive displacement fluid expander. DETAILED DESCRIPTION

[0079] The present disclosure relates to energy recovery devices for use in a variety of applications. In one application, the disclosed energy recovery device can be used in a vehicle power plant application, where waste heat energy from the vehicle power plant is captured and returned to the power plant. In some examples, the working fluid used by the expander is a compressible fluid, such as air. The disclosed energy recovery device can also be used in other applications, such as marine and agricultural industries.

[0080] refer to Figure 1-12 and 23-25, show a Roots-type device 20, also referred to as an energy recovery device, in accordance with the present teachings. Figure 1-12 The Roots-type device 20 is presented in a physical embodiment, and Figure 23-25 A Roots-type device 20 is shown in schematic cross-section.

[0081] In one aspect, the Roots-type device 20 includes a main housing 102 defining an interior cavity or first working fluid passage 106 extending between a first opening 108 and a second opening 110. A pair of intermeshing rotors 30, 32 are disposed within the working fluid passage 106 and extend between end surfaces 30a, 30b and 32a, 32b. In the example presented, the rotors 30, 32 are three-lobed rotors having lobes 30-1, 30-2, 30-3 and 32-1, 32-2, 32-3, for example Fig.18 and 19 , rotors 30, 32 are shown separately in the figure. As presented, each rotor 30 and 32 has the same number of lobes. This is in contrast to the construction of typical rotary screw devices and other similarly configured rotary equipment having different numbers of lobes (e.g., a male rotor having "n" lobes and a female rotor having "n+1" lobes). In addition, one of the notable features of the Roots-type device 20 is that the rotors 30 and 32 are identical, with the rotors 30, 32 being relatively arranged so that, when viewed from one axial end, the lobes of one rotor twist clockwise, while the lobes of the meshing rotor twist counterclockwise. Other configurations are also possible, such as Fig. 20 and 21 The four-lobed rotors 30 , 32 are schematically shown in FIG.

[0082] In the example presented, the first opening 108 is arranged substantially parallel to the longitudinal axis X of the energy recovery device, and the second opening 110 is arranged substantially orthogonal to the longitudinal axis X. Other opening configurations are also possible. In one example, the Roots-type device 20 is configured so that the working fluid 12 flows from the first opening 108 (which can be characterized as the inlet 108) to the second opening 110 (which can be characterized as the outlet 110). The Roots-type device 20 can be operated or configured so that the flow can also occur in the opposite direction. In some examples, the working fluid is a compressible fluid, such as the atmosphere or engine exhaust. In some applications, the Roots-type device 20 works as an expander, wherein the working fluid flows through the channel 106 to impart rotational energy to the rotors 30, 32, which can then be output by the device 20. In some applications, the Roots-type device 20 works as a compressor, such as in a supercharger application, wherein the rotors 30, 32 are rotated to generate and deliver a working fluid flow. In some applications, the same Roots-type device 20 can selectively work in both expander mode and compressor mode.

[0083] On the one hand, and as Fig. 9 and 10 As is most easily seen, each rotor 30, 32 is mounted to a rotor shaft 38, 40, respectively. In the example shown, the shaft 38 has an extension 38a so that power can be transmitted to and / or from the Roots-type device 20 via attached pulleys, gears, etc. Fig.25 In the illustrated schematic example, a pulley or gear 200 is mounted on shaft 38 and is operatively connected to input / output location 16 via a belt, chain, or gear set 202 (e.g., a planetary gear set). Input / output location 16 may be any machine, device, or system capable of receiving, transmitting, or generating energy, such as an electric motor / generator or an internal combustion engine.

[0084] In one aspect, timing gears 42, 44 are mounted on each shaft 38, 40, respectively. The timing gears 42, 44 mesh with each other to ensure that the rotors 30, 32 rotate synchronously, thereby avoiding interference between the rotors 30, 32. Bearings and seal assemblies 46, 48 and 50, 52 of known types are also provided on each shaft 38, 40 on opposite sides of the rotors 30, 32 to rotatably support each shaft 38, 40 and to ensure that the working fluid in the housing passage 106 does not leak through the shaft 38, 40 when leaving the passage 106. In the example shown, the bearing assemblies 46, 48 are supported in cavities 70, 72 of a support plate (bearing plate) 60 mounted on the housing 102. The support plate 60 forms the end surface of the internal cavity of the housing and the passage 106. The bearing assemblies 50, 52 are shown as being supported in a recessed or cavity portion of the housing 102.

[0085] The support plate 60, when removed, provides an opening through which the rotors 30, 32 can be installed into and removed from the interior of the housing 102. Figures 13 to 17106 and the second opening 110. The first recessed area 66 is shown as including an inner face 62 facing the interior of the housing 102 and the passage 106. The inner face 62 includes a main surface 64, a first recessed area 66, and a recessed port 68. The main surface 64 is located adjacent to the end faces 30a, 32b of the rotors 30, 32, so that leakage between the main surface 64 and the rotors 30, 32 is minimized as much as possible. The first recessed area 66 is recessed in the axial direction away from the end faces 30a, 32b of the rotors 30, 32, and also leads to the second opening 110. Therefore, the first recessed area 66 expands the area or volume available for the working fluid to enter or leave the passage 106 and the rotors 30, 32. A recessed port 68, located opposite the first recessed area 66 and the opening 110 and including a first wall 68a parallel to the end faces 30a, 32a of the rotors 30, 32, is also recessed in an axial direction away from the end faces 30a, 32b of the rotors to form a gap 69 that is relatively larger than the gap between the end faces 30a, 32b and the support plate major surface 64. The recessed port 68 also includes a second wall 68b extending from the major surface 64 to the first wall 68a. Thus, the second wall 68b extends in a direction generally orthogonal to the end faces 39a, 32b and parallel to the length of the rotors 30, 32. In one aspect, the second wall 68b can be characterized as having a V-shape or V-shaped shape with a center closer to the longitudinal axis X than the ends of the second wall 68b. This shape is advantageous because the leakage path formed by the recessed port (discussed in more detail below) is more consistently maintained as the height of the rotor lobes necessarily changes as they rotate across the recessed port 68. Although the recessed port 68 is shown as being integrated into the support plate 60, other configurations are also possible. For example, the recessed port 68 can be incorporated into the surface of the housing 102. On the one hand, the support plate 60 and the main housing 102 can be characterized as a housing assembly, and the recessed port 68 can be characterized as being formed in the housing assembly. On the one hand, the recessed port 68 can be characterized as a metering port or an orifice device. On the one hand, the recessed port 68 of the housing 102, the rotor 30, 32 and the support plate 60 jointly define a cross-sectional area or an orifice area that defines a leakage path. The area should be considered as the area perpendicular to the fluid flow through the port, and the port should be parallel to the end face of the rotor. The shape and size of the recessed port 68 can be determined or optimized for a specific application. For example, the depth of the recessed port 68 (i.e., the distance between the first wall 38a and the end face 30a, 32b and defined by the width of the second wall 68b) can be adjusted to produce a desired orifice area. For example, if it is desired that the device 20 have a compressor mode and an expander mode, and the expander efficiency mode is more favorable, the formation of the leakage path will favor this mode, and the recessed port 68 can be designed to be larger to achieve optimized leakage. If the compressor mode is favorable, the recessed port 68 and the resulting leakage path will be minimized to favor the compressor mode. In addition, the pressure ratio and speed of the device 20 will also affect the cross-sectional area of ​​the port.

[0086] During operation, as each rotor lobe 30-1, 30-2, 30-3 and 32-1, 32-2, 32-3 rotates across the recessed port 68, a passage 107 is formed that extends from one longitudinal side of the lobe (e.g., side A) around the end faces 30a, 32b of the lobe and into the recessed port 68 and to the other longitudinal side of the lobe (e.g., side B). Fig.25 is schematically shown in Fig.12 A partial view is provided in FIG. The use of the term "cross" refers to the end face of the cam being exposed to and facing the recessed port, so that there is fluid communication between at least one side of the cam and the recessed port. The use of the term "completely across" refers to the end face of the cam being exposed to and facing the recessed port, so that there is fluid communication between both sides of the cam and the recessed port. When the rotor cam completely passes through the recessed port 68, one side of the cam is in fluid communication with the opening 108, while the other side of the cam is in fluid communication with the opening 110. In this way, the recessed port is used to form an orifice or channel 107 extending between the openings 108, 110. In the example shown, the recessed port 68 is shaped so that at least one rotor cam 30-1, 30-2, 30-3 and 32-1, 32-2, 32-3 of one of the rotors 30, 32 completely passes through the recessed port 68 at all rotation angles, thereby continuously maintaining the channel 107. Therefore, the channel 107 can be characterized as an orifice or a strategic leakage path. At some rotational angles, at least one lobe 30-1, 30-2, 30-3 of the rotor 30 and at least one lobe 32-1, 32-2, 32-3 of the rotor 32 simultaneously pass through the recessed port 68. At some rotational angles of the rotor 30, none of the lobes 30-1, 30-2, 30-3 of the rotor 30 pass through the recessed port 68. At some rotational angles of the rotor 32, none of the lobes 32-1, 32-2, 32-3 of the rotor 32 pass through the recessed port 68. Other configurations are also possible.

[0087] When the device 20 operates as an expander, it is advantageous to form a strategic leakage path 107 because the time or duration of exposure of the working fluid to the rotors 30, 32 is increased. This allows additional working fluid to expand within the outlet to produce a greater pressure drop, which causes additional rotational work to be applied to the rotors 30, 32. In other words, the disclosed design advantageously allows the fluid velocity (i.e., fluid kinetic energy) of the working fluid to remain high and produce rotation within the energy recovery device. The increased fluid velocity helps convert the energy in the fluid flow into rotation of the rotor by applying additional torque on the rotor shaft. The strategic leakage path 107 enabled by the recessed port 68 also ensures that additional expansion occurs in the outlet, thereby ensuring that the working fluid 12 continues to be transmitted out of the device.

[0088] Another advantage is that the recessed ports 68 allow for the formation of strategic leak paths 107 without increasing the twist angle of the rotors 30, 32 above the ideal twist angle that would otherwise have to be increased to ensure that the openings 108, 110 remain in fluid communication with each other without the recessed ports 68. For reference, those skilled in the art know that the twist angle is the angular displacement of the lobe, in degrees, that occurs when "traveling" the length L of the lobe from the rear end of the rotor to the front end of the rotor. Further discussion of the concept of twist angle can be found in U.S. Patent 7,488,164, the entire contents of which are incorporated herein by reference. Fig.32 A diagram of the torsion angle and related parameters is also provided. "Ideal torsion" is the maximum torsion angle at which the rotors 30, 32 can be twisted without causing leakage between the inlet and the outlet. Therefore, by providing a recessed port 68 in the support plate 60 or the modified housing 102, a rotor with an ideal torsion angle or a smaller torsion angle designed for a supercharger application can be easily adapted for an expander application. In one example, a supercharger can be modified for expander operation by replacing an existing support plate 60 with a support plate 60 of the type disclosed herein with a recessed port 68. Even in the case where the rotors 30, 32 are provided with a torsion angle that deviates from the ideal torsion angle, the recessed port 68 will reduce the incremental deviation of the torsion angle that can be expected in the absence of the recessed port 68, because when the fluid 12 is allowed to expand, the fluid will advantageously remain in contact with the rotors 30, 32 in the outlet for a longer time.

[0089] The Roots-type device 20 may also have other configurations. Fig.23 As schematically shown in FIG. 1 , the device 20 may be provided with different configurations of recessed ports, which may also be characterized as metering devices 68 spanning the inlet end and the outlet end. As shown, there is a metering port 68 at the inlet end and a metering port 68 at the opposite end of the inlet, wherein the two metering ports 68 form an intersection of the inlet and the outlet, and are configured such that the recessed ports 68 connecting the inlet 108 and the outlet 110 extend along the length of the rotors 30, 32. Fig.23 As shown, each rotor 30, 32 is provided with four lobes having a 220 degree twist.

[0090] Fig.24 A further variation of the Roots-type device 20 is shown, wherein a nozzle section 24d is provided at the inlet 108, the nozzle section tapering from a first dimension w2 defining a first cross-sectional area to a second dimension w3 at least partially defining a second cross-sectional area smaller than the first cross-sectional area. Figures 25 to 32 The embodiment shown in FIG. 1 is described in more detail for accelerating the velocity of the fluid 12 so that additional efficiency of the Roots-type device 20 can be achieved. Fig.24As shown, incorporating the recessed port 68 and nozzle segment 24d into the same Roots-type device 20 may produce additional operating efficiencies and power output.

[0091] Figures 25 to 32 Another example of a Roots-type device 20 is presented, with Figures 1 to 24 Compared to the device shown in FIG. 2 , this device also includes a nozzle section 24d which is a housing configuration with a modified inlet and outlet. Figures 25 to 32 24d, but the Roots-type device 20 in these figures may be provided with a recessed port forming a bypass passage around the end of the rotor to interconnect the device inlet and outlet. As previously mentioned, the following description of the nozzle section 24d applies to Fig.24 The nozzle section 24d is schematically shown in FIG.

[0092] Continue to refer Figures 24 to 32 , the Roots-type device 20 has a housing 22 with a fluid inlet structure 24 and a fluid outlet structure 26, through which the working fluid 12 generates a pressure drop to transfer energy to an output shaft 38. The inlet structure 24 is configured to receive the working fluid 12-1 at a first pressure, and the outlet structure 26 is configured to discharge the working fluid 12-2 at a second pressure lower than the first pressure. The output shaft 38 is driven by first and second staggered counter-rotating rotors 30, 32 that are synchronously connected and disposed in a cavity 28 of the housing 22. Each of the rotors 30, 32 has a lobed angle that is twisted or spirally disposed along the length of the rotor 30, 32. When the rotors 30, 32 rotate, the lobes at least partially seal the fluid 12-1 inside the housing, and expansion of the fluid 12-1 occurs only to the extent allowed by leakage that represents inefficiency in the system. In contrast to some Roots-type devices, which change the volume of the fluid as it is sealed, the volume defined between the lobes and the inside of the housing 22 of the device 20 is constant as the fluid 12-1 traverses the length of the rotors 30, 32. Thus, the Roots-type device 20 is referred to as a "positive displacement device" because the volume of the fluid that is sealed or partially sealed does not change.

[0093] like Fig.31As further schematically shown in the figure, each rotor 30, 32 has four lobes, 30-1, 30-2, 30-3 and 30-4 for rotor 30, and 32-1, 32-2, 32-3 and 32-4 for rotor 32. Although four lobes are shown for each rotor 30 and 32, each of the two rotors can have any number of lobes equal to or greater than two, such as three lobes. In addition, the number of lobes of each rotor 30 and 32 is the same. This is in contrast to the construction of typical rotary screw devices and other similarly configured rotating devices with different numbers of lobes (e.g., a male rotor with "n" lobes and a female rotor with "n+1" lobes). In addition, one of the notable features of the Roots-type device 20 is that the rotors 30 and 32 are identical, wherein the rotors 30, 32 are arranged relative to each other so that, viewed from one axial end, the lobes of one rotor twist clockwise, while the lobes of the meshing rotor twist counterclockwise. Thus, when one lobe of rotor 30 (eg, lobe 30 - 1 ) leads relative to inlet structure 24 , one lobe of rotor 32 (eg, lobe 30 - 2 ) lags relative to inlet structure 24 , and therefore relative to high pressure fluid flow 12 - 1 .

[0094] As shown, the first rotor 30 and the second rotor 32 are fixed to respective rotor shafts, the first rotor being fixed to the output shaft 38 and the second rotor being fixed to the shaft 40. Each of the rotor shafts 38, 40 is mounted on a bearing set 43, 45 in a manner rotatable about axes X1, X2, respectively. It is worth noting that axes X1 and X2 are substantially parallel to each other.

[0095] The first rotor 30 and the second rotor 32 are interlaced and continuously meshed with each other to rotate together. Figure 1 , the expander 20 also includes meshing timing gears 42 and 44, wherein the timing gear 42 is fixed to rotate with the rotor 30 and the timing gear 44 is fixed to rotate with the rotor 32. The timing gears 42, 44 are also configured to maintain the relative position of the rotors 30, 32, thereby completely preventing contact between the rotors, which may cause serious damage to the rotors 30, 32. Instead, during rotation, the timing gears 42, 44 maintain close tolerances between the rotors 30, 32. Because the rotors 30, 32 are non-contacting, the operation of the Roots-type device 20 does not require lubricant in the fluid 12, compared to typical rotary screw devices and other similarly constructed rotary devices having rotor lobes that contact each other.

[0096] As the working fluid 12 undergoes expansion from the higher first pressure working fluid 12-1 to the lower second pressure working fluid 12-2, the working fluid 12 causes the output shaft 38 to rotate. Figure 1 , 2As can be additionally seen in FIGS. 7 and 8 , the output shaft 38 extends beyond the boundaries of the housing 22. Thus, the output shaft 38 is configured to capture the work or power generated by the expander 20 during the expansion of the fluid 12 (which expansion occurs in the rotor cavity 28 between the inlet structure 24 and the outlet structure 26) and transmit the work as an output torque from the expander 20. Although the output shaft 38 is shown as being operatively connected to the first rotor 30, in the alternative, the output shaft 38 may be operatively connected to the second rotor 32. The output shaft 38 may be coupled to the engine so that energy from the exhaust gas may be recaptured.

[0097] In one aspect of the geometry of the expander 20, each of the rotor lobes 30-1 to 30-4 and 32-1 to 32-4 has a lobe geometry in which the twist of each of the first rotor 30 and the second rotor 32 is constant along their substantially matched lengths L. Figure 8 As schematically shown in FIG. 1 , one parameter of the lobe geometry is the helix angle HA. By definition, it should be understood that the "helix angle" of the rotor lobes referred to below refers to the helix angle at the pitch diameter PD (or pitch circle) of the rotors 30 and 32. The term pitch diameter and its identification are well understood by those skilled in the art of gears and rotors and will not be discussed further herein. As used herein, the helix angle HA can be calculated as follows: Helix angle (HA) = (180 / .π.*arctan(PD / Lead)), where: PD = the pitch diameter of the rotor lobe; Lead = the length of the lobe required for the lobe to complete a 360-degree twist. It should be noted that Lead is a function of the twist angle and length LI, L2 of the lobes 30, 32, respectively. It is known to those skilled in the art that the twist angle is the angular displacement of the lobe, in degrees, which occurs when the length of the lobe is "traveled" from the rear end of the rotor to the front end of the rotor. In some examples, the twist angle is about 120 degrees, although the twist angle can be larger or smaller degrees.

[0098] In another aspect of the expander geometry, the inlet configuration 24 includes an inlet angle 24-1, such as Fig.26 In one example, the inlet angle 24-1 is defined as the general or average angle of the inner surface 24a (e.g., the front inner surface) of the inlet structure 24. In one example, the inlet angle 24-1 is defined as the angle of the general centerline CL-1 of the inlet structure 24, such as Figure 2 In one example, the inlet angle 24-1 is defined as the general direction of the fluid 12-1 entering the rotor 30, 32 due to contact with the front inner surface 24a, as shown in FIG. Fig.26As shown, the inlet angle 24-1 is neither perpendicular nor parallel to the rotational axes X1, X2 of the rotors 30, 32. Therefore, the front inner surface 24a of the inlet structure 24 causes a large portion of the fluid 12-1 to be formed in a direction that is oblique to the rotational axes X1, X2 of the rotors 30, 32 and is therefore generally parallel to the inlet angle 24-1.

[0099] In addition, if Figures 26 to 29 As shown, the inlet structure 24 can be shaped so that the fluid 12-1 is directed to the first axial end of the rotor 30, 32 and is directed from the lateral direction to the rotor lobe leading and trailing edge surfaces (discussed below). However, it should be understood that the inlet angle 24-1 can be generally parallel or generally perpendicular to the axis X1, X2, although efficiency losses may be expected for certain rotor configurations. For example, Fig.24 As shown, the inlet angle 24-1 is generally parallel to the axes X1, X2. The term "generally parallel" is used to refer to angles that are within 10 to 15 degrees of each other. In addition, as discussed in more detail later, it is worth noting that the inlet structure 24 can be shaped to narrow toward the inlet opening 24b, such as Fig.26 and 28 shown.

[0100] In another aspect of the expander geometry, the outlet configuration 26 includes an outlet angle 26-1, such as Fig.26 In one example, the outlet angle 26-1 is defined as the general or average angle of the inner surface 26a of the outlet structure 26. In one example, the outlet angle 26-1 is defined as the angle of the general centerline CL-2 of the outlet structure 26, such as Fig.26 and 27 In one example, the exit angle 26-1 is defined as the general direction of the fluid 12-2 exiting the rotors 30, 32 due to contact with the inner surface 26a, as shown in FIG. Fig.26 As shown. As shown, the outlet angle 26-1 is neither perpendicular nor parallel to the rotational axes X1, X2 of the rotors 30, 32. Therefore, the inner surface 26a of the outlet structure 26 receives the fluid 12-2 exiting from the rotors 30, 32 at an inclined angle, which can reduce the back pressure at the outlet structure 26. In one example, the inlet angle 24-1 and the outlet angle 26-1 are skewed relative to each other, as shown in the figure. In an alternative arrangement, the inlet angle 24-1 and the outlet angle 26-1 can be substantially equal or parallel. It should be understood that the outlet angle 26-1 can be substantially perpendicular to the axes X1, X2, as shown in FIG. Fig.24As configured, the orientation and size of the outlet structure 26-1 are set so that the exiting fluid 12-2 can be discharged from each rotor cavity 28 as easily and quickly as possible, thereby reducing back pressure as much as possible. The output power of the shaft 38 is maximized so that the back pressure caused by the outlet can be minimized, thereby enabling rapid discharge of the fluid.

[0101] The efficiency of the expander 20 can be optimized by coordinating the geometry of the inlet angle 24-1 and the geometry of the rotors 30, 32. For example, the helix angle HA and the inlet angle 24-1 of the rotors 30, 32 can be configured together in a complementary manner. Since the inlet structure 24 introduces the fluid 12-1 to both the leading edge and trailing edge faces of each rotor 30, 32, the fluid 12-1 performs both positive and negative work on the expander 20.

[0102] To illustrate, Fig.31 It is shown that the lobes 30-1, 30-4, 32-1 and 32-2 are all exposed to the fluid 12-1 through the inlet structure opening 24b. Each lobe has a leading edge surface and a trailing edge surface, and the leading edge surface and the trailing edge surface are exposed to the fluid at various rotation points of the associated rotor. The leading edge surface is the side of the lobe that is most forward when the rotor rotates in directions R1, R2, and the trailing edge surface is the side of the lobe opposite to the leading edge surface. For example, the rotor 30 rotates in the direction R1, thereby causing the side 30-1a to become the leading edge surface of the lobe 30-1, and the side 30-1b to become the trailing edge surface. When the rotor 32 rotates in the direction R2 opposite to the direction R1, the leading edge surface and the trailing edge surface are in a mirror image relationship, so that the side 32-2a is the leading edge surface of the lobe 32-2, and the side 32-2b is the trailing edge surface.

[0103] In summary, the fluid 12-1 strikes the trailing edge surfaces of the lobes as they pass through the inlet structural opening 24b and performs positive work on each rotor 30, 32. The use of the term "positive work" means that the fluid 12-1 causes the rotors to rotate in the desired direction: direction R1 for rotor 30 and direction R2 for rotor 32. As shown, the fluid 12-1 will operate to perform positive work on the trailing edge surface 32-2b (e.g., surface portion 47) of the lobe 32-2. The fluid 12-1 also performs positive work on the trailing edge surface 30-1b (e.g., surface portion 46) of the lobe 30-1. However, the fluid 12-1 also strikes the leading edge surfaces of the lobes, such as surfaces 30-1a and 32-1a, as the lobes pass through the inlet structural opening 24b, thereby performing negative work on each rotor 30, 32. The use of the term "negative work" means that the fluid 12-1 causes the rotors to rotate in a direction opposite to the desired direction R1, R2.

[0104] Therefore, it is desirable to shape and orient the rotors 30 , 32 and inlet structure 24 so that as much fluid 12 - 1 as possible strikes the trailing edge surfaces of the lobes while as little fluid 12 - 1 as possible strikes the leading edge surfaces of the lobes so that the expander 20 can perform the highest net positive work.

[0105] In the example shown, the inlet structure 24 includes a first inlet section 24c and a nozzle section 24d located between the rotors 30, 32 and the first inlet section 24c. In the example shown, the inlet section 24c has a generally constant diameter or dimension w1. In some examples, the inlet section 24c may be tapered. In the example shown, the transition section 24e is located between the first inlet section 24c and the nozzle section 24d and includes a rounded or tapered section that transitions to a diameter or dimension w2.

[0106] As shown, the nozzle segment 24d tapers from a diameter or dimension w2 adjacent to the first inlet segment 24c to a diameter or dimension w3 adjacent to the rotors 30, 32. In some examples, the taper between w2 and w3 results in a reduction in the cross-sectional area of ​​the nozzle segment 24d of at least ten percent. In the example shown, the nozzle segment 24d includes a truncated cone such that the sidewalls of the nozzle segment 24d are straight and define a continuous, tapered cone, as shown. However, the nozzle segment 24d may be provided with a cone that is curved in cross section. In the example shown, and as in Figures 27 to 29 As best seen in the drawings, the first inlet section 24c and the nozzle section 24d each have a circular cross-sectional shape. However, other cross-sectional shapes are possible, such as oval, elliptical, rectangular, and oblong. The nozzle section 24d may also be tapered in an asymmetrical manner, for example, where only one side of the nozzle section 24d forms a tapered cross section, such as Fig.24 , where the nozzle segment 24d is also arranged to direct the fluid flow 12 - 1 into the ends of the rotors 30 , 32 .

[0107] In one aspect, the inlet velocity VN of the fluid 12-1 exiting the nozzle section 24d and entering the rotors 30, 32 should be at least equal to the rotor mesh axial lead velocity of the rotors 30, 32 to achieve optimal energy conversion. Figure 4As schematically shown in , the axial lead rate VL is a well-known parameter in Roots-type devices and may also be referred to as the linear rate of cam engagement. This parameter represents the speed at which the V-shape defined between the overlapping cams of the mutually meshing rotors 30, 32 travels in the longitudinal direction (i.e., parallel to the longitudinal axis X). The axial lead rate is further described and illustrated in U.S. Patent 7,788,164, which is incorporated herein by reference. In some applications, increasing the torsion angle of the rotors 30, 32 results in further performance gains. In one example, as summarized in Table 1 below, an expander is provided having a displacement of 644cc (cubic centimeters) and a rotor lead of 200m, such that dimension w1 is 89mm, dimension w2 is 76mm, and dimension w3 is 60mm. Therefore, the cross-sectional area of ​​the nozzle section 24d is reduced by more than 20%, and the fluid rate is increased accordingly.

[0108]

[0109] Table 1

[0110] As can be seen in Table 1, nozzle section 24d more than doubles the rotor axial lead velocity at all operating speeds of the rotor, thereby improving the overall efficiency of the expander. As a result, the port velocity value (V N ) ranges from 7.59m / s to 53.15m / s and always exceeds the rotor axial guide velocity (V L ), rotor axial guide speed (V L ) ranges from 6.67 m / s to 46.67 m / s over the entire operating range of 2,000 to 14,000 rpm of the rotor. In the particular example shown, the nozzle velocity V N Approximately the rotor axial guide speed V L However, in some applications, such as low pressure applications, the nozzle velocity V N The rotor axial guide speed V L For example, the nozzle velocity V N It can be the rotor axial guide speed V L About 1.6 times, or more.

[0111] Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the examples and teachings presented herein.The specification and examples are to be considered exemplary only, with the true scope of the invention being indicated by the following claims.

Claims

1. A Roots-type device, comprising: a) a housing assembly having a first opening and a second opening in fluid communication with the interior cavity; b) a pair of identical rotors, the pair of rotors being oppositely disposed within the interior cavity, each of the pair of rotors having a longitudinal axis and a plurality of lobes, each of the lobes defining an end surface extending between a first longitudinal side of the lobe and a second longitudinal side of the lobe; and c) a recessed port defined within the housing assembly and axially spaced from an end face of the cam, the recessed port fluidly connecting a first longitudinal side of one of the cams to a second longitudinal side of the cam such that the first opening is in fluid communication with the second opening.

2. The Roots-type device according to claim 1, wherein: The housing assembly includes a main housing and a support plate secured to the main housing, and the recessed port is defined within the support plate.

3. The Roots-type device according to claim 1, wherein: An end surface of at least one lobe faces the recessed port at all rotational angles of the rotor.

4. The Roots-type device according to claim 1, wherein: The twist angle of each rotor of the pair of rotors is less than or equal to an ideal twist angle of the rotor defined in the absence of the recessed port.

5. The Roots-type device according to claim 1, wherein: Each rotor of the pair of rotors has at least three lobes.

6. The Roots-type device according to claim 1, wherein: The rotor is axially located between the first opening and the recessed port.

7. The Roots-type device according to claim 1, wherein: The pair of rotors are each supported by a rotatable shaft between the second opening and the recessed port.

8. The Roots-type device according to claim 1, wherein: The pair of rotors are each supported by a shaft having a longitudinal axis aligned along a first longitudinal plane, wherein the housing outlet is located on a first side of the first longitudinal plane, and wherein the recessed port is located on a second side of the first longitudinal plane.

9. The Roots-type device according to claim 1, wherein: The first opening is orthogonal to the longitudinal axis of the rotor.

10. The Roots-type device according to claim 1 or 9, wherein: The second opening is parallel to the longitudinal axis of the rotor.

11. A Roots-type device, comprising: a) a pair of rotors; and b) a housing assembly in which the rotor is disposed, the housing assembly having a first opening and a second opening, and having a recessed port that places the first opening in fluid communication with the second opening.

12. The Roots-type device according to claim 11, wherein: The recessed port is located at a first axial end of the pair of rotors.

13. The Roots-type device according to claim 11, wherein: The recessed port defines a leakage path about an axial end of at least one lobe of the pair of rotors at least some rotational positions of the pair of rotors.

14. The Roots-type device according to claim 13, wherein: The recessed port fluidly connects a first longitudinal side of the at least one lobe with a second longitudinal side of the at least one lobe.

15. The Roots-type device according to claim 11, wherein: The housing assembly includes a main housing and a support plate secured to the main housing, and the recessed port is defined within the support plate.

16. The Roots-type device according to claim 11, wherein: An end surface of at least one lobe of the pair of rotors faces the recessed port at all rotation angles of the rotors.

17. The Roots-type device according to claim 11, wherein: The twist angle of each rotor of the pair of rotors is less than or equal to an ideal twist angle of the rotor defined in the absence of the recessed port.

18. The Roots-type device according to claim 11, wherein: Each rotor of the pair of rotors has at least three lobes.

19. The Roots-type device according to claim 11, wherein: The rotor is axially located between the first opening and the recessed port.

20. The Roots-type device according to claim 11, wherein: The pair of rotors are each supported by a rotatable shaft between the second opening and the recessed port.

21. The Roots-type device according to claim 11, wherein: The pair of rotors are each supported by a shaft having a longitudinal axis aligned along a first longitudinal plane, wherein the housing outlet is located on a first side of the first longitudinal plane, and wherein the recessed port is located on a second side of the first longitudinal plane.

22. The Roots-type device according to claim 11, wherein: The first opening is orthogonal to the longitudinal axis of the rotor.

23. A Roots-type device according to claim 11 or 22, wherein: The second opening is parallel to the longitudinal axis of the rotor.

24. A support plate for a Roots-type device, the support plate comprising: a) a body extending from a first side along a longitudinal axis to a second side; b) a pair of cavities for supporting a bearing and a seal assembly, the cavities extending between the first side and the second side of the body; c) a major surface at least partially defining the first side and being orthogonal to the longitudinal axis; and d) a first recessed area at least partially defining the first side and being axially recessed from the major surface in a direction toward the second side, the recessed area being configured to provide a leakage path for the Roots-type device.

25. The support plate according to claim 24, wherein The first recessed area is located entirely on a first side of a plane centrally passing through the pair of cavities and extending parallel to the longitudinal axis.

26. The support plate according to claim 24, wherein The first recessed area extends to an outer edge of the body.

27. The support plate according to claim 25, wherein The body includes a second recessed area that at least partially defines the first side and is axially recessed from the major surface in a direction toward the second side, the second recessed area being completely located on a second side of the plane.

28. The support plate of claim 24, wherein: The first recessed area is V-shaped.

29. A Roots-type device according to any preceding claim, further comprising: a) an inlet nozzle structure in fluid communication with the first opening, the inlet nozzle structure tapering toward the first opening and configured such that a nozzle velocity of a working fluid passing through the inlet nozzle structure is at least equal to a rotor mesh axial lead velocity.

30. A method of retrofitting a supercharger for an expander application, the method comprising: a) providing a supercharger, the supercharger having a pair of rotors and a housing assembly in which the rotors are disposed, the housing assembly having a first opening and a second opening; b) removing the first support plate of the supercharger; c) mounting a second support plate to the supercharger, the second support plate including a recessed port that places the first opening in fluid communication with the second opening.

31. A Roots-type device, comprising: a) a housing assembly having a first opening and a second opening in fluid communication with the interior cavity; b) a pair of identical rotors oppositely disposed within the interior cavity, each rotor of the pair of rotors having a longitudinal axis and a plurality of lobes, wherein the rotors intermesh and define a rotor mesh axial lead rate when rotated; and c) an inlet nozzle structure in fluid communication with the first opening, the inlet nozzle structure tapering toward the first opening and configured such that a nozzle velocity of a working fluid through the inlet nozzle structure is at least equal to the rotor mesh axial lead velocity.

32. A Roots-type device according to claim 31, wherein: The inlet nozzle structure is oriented generally parallel to the longitudinal axis.

33. A Roots-type device according to claim 31, wherein: The inlet nozzle structure is oriented at an oblique angle to the longitudinal axis.

34. A Roots-type device according to claim 31, wherein: The cross-sectional area of ​​the inlet nozzle structure is reduced by at least 20%.

35. A Roots-type device according to claim 31, wherein: The volume flow through the inlet nozzle arrangement is increased at least two-fold.

36. A Roots-type device according to claim 31, wherein: Each of the rotors includes at least three lobes.

37. A Roots-type device according to claim 31, wherein: The nozzle velocity is greater than the rotor engagement axial lead velocity.

38. A Roots-type device according to claim 31, wherein: The nozzle velocity is at least 1.1 times the rotor mesh axial lead velocity.

39. A Roots-type device according to claim 31, wherein: The nozzle velocity is at least 1.6 times the rotor mesh axial lead velocity.

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