Piston assembly having a piston face with retainers

Abstract

Pistons, and assemblies thereof, are provided herein with piston faces and lands including different features and geometries. The piston faces described herewith have a central portion (110) and a plurality of retainers (114). Each retainer of the plurality of retainers (114) extends radially outward relative to the central portion (110). At least one pair of adjacent retainers of the plurality of retainers (114) are disconnected at respective radially outward ends (116) of the at least one pair of adjacent retainers (114).

Description

Docket No.: 000102-0043 -WO 1PISTON ASSEMBLY HAVING A PISTON FACE WITH RETAINERSCross-Reference to Related Applications

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 700,213 filed September 27, 2024, the disclosure of which is hereby incorporated by reference herein in its entirety.Field of Disclosure

[0002] The present disclosure is directed to a piston having a plurality of ring retainers and, more particularly, to piston assemblies with sealing ring segments retained in a circumferential region of a piston land using a plurality of radially extending retainers.Summary

[0003] Generators include various moving components for generating energy. Some generators, for example, rely on the motion of piston assemblies and an electromagnetic interaction between translators coupled thereto and stationary stators that at least partially form a bore of a cylinder along which the piston assemblies move. Preferably, the piston assemblies are optimized in terms of how much material is included (e.g., the mass may be reduced) as compared to the expected material stresses as caused by the conditions in the cylinders as a generator with these piston assemblies is operated. Additionally, these piston assemblies can incorporate sealing ring assemblies which maintain alignment of the piston assemblies as they move along the cylinder bore while providing a sealing surface that contacts the bore to separate a high pressure region (e.g., as generated by reacting reactants in a reaction section) that is in contact with a face of the piston assemblies from a back end low pressure region (e.g., to prevent propagation of a reaction behind a sealing interface between a sealing ring assembly in a circumference groove of a piston of the piston assembly and a cylinder bore along which the piston assembly translates).

[0004] During operation of a device (e.g., a generator) with piston assemblies that include sealing ring segments, the sealing ring segments are subjected to wear based on contact with a bore of the cylinder and the relative motion of the segments based on motion of the piston assembly along the bore. Additionally, the ring segments can be subjected to forces that cause relative motion as compared to the piston assembly. Preferably, a piston assembly isprovided with retaining features such that, as sealing ring segments wear or have relative motion caused by contact and friction, the segments remain in a position for continued piston assembly movement along the bore (e.g., for a desired operational lifetime of a generator with the ring segments).

[0005] As an example piston assembly reciprocates within a cylinder (e.g., axially along the bore of the cylinder), gas mixtures are compressed and expanded. The gas mixtures may be various mixtures of fuel and air (e.g., reactants for causing a reaction to occur in a reaction section of the cylinder that is in contact with a face of a piston of the piston assembly). Under certain operational circumstances, fuel and air mixture can occupy one or more volumes between the piston and the bore of the cylinder or between a piston surface and a sealing ring segment surface (e.g., of a sealing ring assembly arranged in a circumferential groove of the piston). These volumes may be referred to as “crevice volumes.”

[0006] When a mixture of fuel and air occupies one of the mentioned crevice volumes, the mixture may cool to a low enough temperature such that the mixture may not react enough to achieve all intended chemical reactions thereby preventing all, or enough, fuel of the mixture from reacting during a reaction (e.g., compression) phase of motion of a piston assembly along a bore. One contributing factor for this cooling effect when mixtures of fuel and air occupy one or more described crevice volumes is the amount of surface area that forms, or encloses, the crevice volume as compared to the volume of the space defining the crevice volume. Unreacted fuel resulting from fuel and air mixtures being cooled in the crevice volumes propagates from the reaction section of the cylinder towards exhaust ports, resulting in emissions that fail to comply with target content levels while also resulting in an overall loss of efficiency of the device (e.g., generator) relying on propagation of the piston assembly based on reactions.

[0007] Described herein are pistons and piston assemblies with a plurality of retainers (e.g., retaining features) that are configured to maintain positioning of ring segments relative to a piston assembly as the piston assembly translates along a bore of a cylinder. The pistons and piston assemblies of this disclosure include a piston face with a central portion and a plurality of retainers that extend radially outward relative to the central portion. At least one pair of adjacent retainers of the plurality of retainers are disconnected at respective radially outward ends of the at least one pair of adjacent retainers.

[0008] These retainers provide a benefit of reducing mass of a piston by having less material extending from a piston land, for example, as would be employed for forming a ring groove for arranging the aforementioned sealing ring segments. Additionally, these retainerscan, in some embodiments, be structured such that adjacent pairs of retainers overlap a single ring segment such that each ring segment has two points of contact by two distinct retainers for enhanced securing of a sealing ring assembly having a plurality of different segments within a ring groove embedded in a land of a piston.

[0009] In some embodiments, the piston face comprises a surface profile comprised of the central portion and the plurality of retainers. Additionally, or alternatively, the plurality of retainers comprises at least one tine.

[0010] In some embodiments, the plurality of retainers forms a front land. Additionally, or alternatively, the piston further includes a rear land and a circumferential groove between the front land and the rear land. The front land has a first radial length. The rear land has a second radial length. In some embodiments, the first radial length is less than the second radial length.

[0011] In some embodiments, the plurality of retainers includes at least one tapered retainer. Additionally, or alternatively, the plurality of retainers comprises at least one retainer of a trapezoidal geometry.

[0012] In some embodiments, the disclosure is directed to a piston assembly with a sealing ring assembly and a piston. The piston includes a circumferential groove (e.g., that accommodates the sealing ring assembly) and a piston face. The piston face includes a central portion and a plurality of retainers (e.g., projections) that extend radially outward relative to the central portion, wherein at least one pair of adjacent retainers of the plurality of retainers are disconnected at respective ends of the at least one pair of adjacent retainers.

[0013] In some embodiments, the sealing ring assembly includes a plurality of segments. Additionally, or alternatively, each respective segment of the plurality of ring segments is at least axially retained by at least two adjacent retainers of the plurality of retainers.

[0014] In some embodiments, the disclosure is directed to a device (e.g., a generator or linear generator). The generator has a reaction section and a piston configured to interface with the reaction section. The piston includes a piston face with a central portion and a plurality of retainers that extend radially outward relative to the central portion, wherein at least one pair of adjacent retainers of the plurality of retainers are disconnected at respective ends of the at least one pair of adjacent retainers.

[0015] In some embodiments, the reaction section is axially adjacent to the central portion. Additionally, or alternatively, the piston includes a circumferential groove configured to accommodate a sealing ring assembly. In some embodiments, the device enables a reaction to propagate from the reaction section into the circumferential groove. The device may, forexample, be a generator that relies of propagation of one or more piston assemblies of this disclosure that have the pistons including retainers. In some embodiments, the spacing between retainers may be wide enough to enable reaction gases (e.g., fuel and air mixtures) to flow in between the retainers and reside while still being subjected to at least a propagation of a reaction thereby reducing the number, or overall presence of, the aforementioned crevice volumes (e.g., relatively small volumes between surfaces as compared to the space between retainers than can cool and trap reactants, thereby preventing reaction of the cooled and trapped reactants).

[0016] In some embodiments, the sealing ring assembly comprises a plurality of segments. Additionally, or alternatively, each respective segment of the plurality of ring segments is at least axially retained by at least two adjacent retainers of the plurality of retainers. In some embodiments, the plurality of retainers includes at least one tine.Brief Descriptions of the Drawings

[0017] The present disclosure, in accordance with one or more various embodiments, is described in detail with reference to the following figures. The above and other objects and advantages of the disclosure may be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which:

[0018] FIG. 1 illustrates a perspective view of a portion of an illustrative piston assembly, in accordance with some embodiments of the disclosure;

[0019] FIG. 2 illustrates a perspective view of a portion of an illustrative piston, in accordance with some embodiments of the disclosure;

[0020] FIG. 3 A illustrates perspective view of a portion of an illustrative piston, in accordance with some embodiments of the disclosure;

[0021] FIG. 3B illustrates a portion of the illustrative piston of FIG. 3 A, in accordance with some embodiments of the disclosure;

[0022] FIG. 4 illustrates a planar view of an illustrative piston face of a piston assembly, in accordance with some embodiments of the disclosure;

[0023] FIG. 5 illustrates a planar view of an illustrative piston face of a piston, in accordance with some embodiments of the disclosure;

[0024] FIG. 6 illustrates a portion of a planar view of an illustrative piston face of a piston assembly, in accordance with some embodiments of the disclosure; and

[0025] FIG. 7 illustrates a cross-sectional view of an illustrative device, including a piston and cylinder assembly, in accordance with some embodiments of the disclosure.Detailed Description

[0026] The present disclosure is directed to a piston having a plurality of ring retainers and, more particularly, to piston assemblies with sealing ring segments retained in a circumferential region of a piston land using a plurality of radially extending retainers. The present disclosure, in accordance with one or more embodiments described herein, is described in detail with reference to the following figures. The drawings are provided for purposes of illustration only and merely depict typical or example embodiments. These drawings are provided to facilitate an understanding of the concepts disclosed herein and shall not be considered limiting of the breadth, scope, or applicability of these concepts. It should be noted that for clarity and ease of illustration, these drawings are not necessarily made to scale.

[0027] FIG. 1 shows piston assembly 100, in accordance with some embodiments of the disclosure. Piston assembly 100 may incorporate, or be incorporated into, any or all of the pistons and piston assemblies shown and described in reference to FIGS. 2-6. Additionally, or alternatively, piston assembly 100 may be incorporated, in whole or in part, into device 700 of FIG. 7. For example, piston assembly 100, or any feature thereof, may be incorporated into any or all of the pistons and piston assemblies shown and described in reference to FIGS. 2-7.

[0028] Piston assembly 100 includes sealing ring assembly 102 and piston 104. Sealing ring assembly 102 is shown with multiple segments. In some embodiments, sealing ring assembly 102 may include fewer than the depicted segments or more than the depicted segments. In some embodiments, at least one ring segment of the multiple segments may be sufficiently short in circumferential, or azimuthal, length such that a single retainer of retainers 114 (e.g., tines) is configured to suitably retain the at least one ring segment in the circumferential groove for an operational lifetime of the at least one ring segment. Sealing ring assembly 102 is configured to seal against a bore of a cylinder (not shown) along which piston assembly 100 translates. A radially outward surface of sealing ring assembly 102 is configured to form the seal by contacting the bore responsive to a radially inward surface of sealing ring assembly 102 receiving radially outward forces through circumferential groove 106 based at least in part on a reaction in a reaction section that is axially adjacent to, or contacting piston face 108.

[0029] Piston 104 includes circumferential groove 106, which accommodates sealing ring assembly 102. Piston 104 is shown with piston face 108. Piston face 108 includes central portion 110 and radially outward portion 112. Central portion 110 may, in someembodiments, at least partially define a reaction section of a device (e.g., device 700 of FIG. 7), may be axially adjacent to a reaction section of a device, or may contact a reaction section of a device. Radially outward portion 112 may, in some embodiments, at least partially form a land of piston 104. Radially outward portion 112 is shown with a plurality of retainers 114. Each of retainers 114 extend radially outward relative to central portion 110. As shown in FIG. 1, at least one pair of adjacent retainers of retainers 114 is disconnected at respective ends of the at least one pair of adjacent retainers. For example, ends 116 are depicted in FIG. 1 as being azimuthally separated.

[0030] Piston face 108 has a surface profile that includes retainers 114 and central portion 110. Retainers 114 may, in some embodiments, be any suitable geometry for retaining sealing ring assembly 102 within circumferential groove 106. For example, at least one of retainers 114 may be formed as a tine (e.g., a prong, or extension including a tapered or pointed end). Additionally, or alternatively, at least one of retainers 114 may have a tapered profile (e.g., one or more of radially tapered, axially tapers, or azimuthally tapered).

[0031] Although retainers 114 of FIG. 1 and other retainers of this disclosure (e.g., as shown at least in FIGS. 2-5) may be perceived as having a uniform distance, or pitch, between adjacent retainers for the entire circumference of radially outward portion 112, the distance, or pitch, need not be uniform to adequately retain sealing ring segments within circumferential groove 106. For example, sealing ring assembly 102, or any described sealing ring assembly of this disclosure, may include a plurality of ring segments of different, or varying, azimuthal, or circumferential, lengths. Additionally, or alternatively, these plurality of ring segments of varying geometries may contact, or overlap, with different end portions of adjacent ring segments in varying, or different, manners throughout the sealing ring assembly. Accordingly, retainers 114, or any of the retainers of this disclosure, may be one or more of azimuthally spaced, or azimuthally arranged, according to one or more of the spacing, the sizing, or the geometry (e.g., overlapping or otherwise) of any suitable sealing ring assembly for forming a seal against a bore of a cylinder such that at least one retainer (e.g., including two or more retainers) are arranged over each respective sealing ring segment such that each respective sealing ring segment (e.g., regardless of spacing, sizing, or geometry) has at least one corresponding retainer to maintain positioning of the at least one respective sealing ring segment in a circumferential groove of a piston (e.g., during operation of a device that includes one or more of the pistons and the piston assemblies of this disclosure such as a generator).

[0032] In some embodiments, a sealing ring assembly with at least one varied sealing ring segment (e.g., a segment that is of a different size or geometry than other sealing ring segments of the sealing ring assembly) may be clocked within a circumference groove of this disclosure such that at least one varied retainer (e.g., a tine, or at least two tines, of a suitable geometry for retaining the varied sealing ring segment in the circumferential groove) is circumferentially, or azimuthally, aligned with the at least one varied sealing ring segment.

[0033] As shown in FIG. 1, retainers 114 form axially front land 118 of piston 104. Piston 104 also includes axially rear land 120 which, in some embodiments, supports an axially rearward surface of sealing ring assembly 102. Circumferential groove 106 is positioned, or at least partially formed, between front land 118 and rear land 120.

[0034] FIG. 2 shows piston 200, in accordance with some embodiments of the disclosure. Piston 200 may incorporate, or be incorporated into, any or all of the pistons and piston assemblies shown and described in reference to FIGS. 1 and 3A-6. Additionally, or alternatively, piston 200 may be incorporated, in whole or in part, into device 700 of FIG. 7. For example, piston 200, or any feature thereof, may be incorporated into any or all of the pistons and piston assemblies shown and described in reference to FIGS. 1 and 3A-7.

[0035] Piston 200 includes piston face 202 and circumferential groove 204. Piston face 202 includes central portion 206 and radially outward portion 208. Central portion 206 may, in some embodiments, at least partially define a reaction section of a device (e.g., device 700 of FIG. 7), may be axially adjacent to a reaction section of a device, or may contact a reaction section of a device. Radially outward portion 208 includes retainers 210, which extend radially outward relative to central portion 206. As shown in FIG. 2, ends 212 of an adjacent pair of retainers 210 are disconnected, thereby forming an azimuthal gap between ends 212.

[0036] Piston 200 includes front land 214 (e.g., as formed at least in part by retainers 210) and rear land 216. Circumferential groove 204 is formed at least in part by, or axially between, front land 214 and rear land 216. In some embodiments, circumferential groove 204 may be utilized to accommodate a sealing ring assembly (e.g., sealing ring assembly 102 of FIG. 1). Front land 214 has first radial length 218. Rear land 216 has second radial length 220. In some embodiments, first radial length 218 is less than second radial length 220 (e.g., as shown in FIG. 2). Additionally, or alternatively, first radial length 218 may correspond to a radial length that a fully worn sealing ring segment has after completing an operational lifecycle post use in a device including piston 200 (e.g., device 700 of FIG. 7).

[0037] A sealing ring assembly configured for installation in circumferential groove 204 may, in some embodiments, have a radial length that extends beyond second radial length220 (e.g., as shown by sealing ring assembly 102 of FIG. 1 at least partially over rear land 120). The radial length of a sealing ring assembly described herein may, in some embodiments, be initially compressed radially inward when in an installation state such that the radial length of the sealing ring assembly is the same as, or substantially similar to, second radial length 220. This may, for example, assist with installing a piston assembly with a sealing ring assembly arranged in a circumferential groove into a bore of a cylinder such that the sealing ring assembly expands radially outward to contact the bore of the cylinder (e.g., to maintain a sealing interface during operation of a device that relies on propagation of a piston assembly along a bore of a cylinder for producing energy).

[0038] As shown in FIG. 2, retainers 210 have a trapezoidal geometry (e.g., a shape having a pair of parallel sides). In some embodiments, any or all of retainers 210 may be of any suitable geometry for at least axially retaining a sealing ring assembly (e.g., sealing ring assembly 102 of FIG. 1) in circumferential groove 204. As shown in at least FIG. 2, retainers of this disclosure (e.g., retainers 210) have first radial length 218 that is shorter than second radial length 220 of rear land 216. In some embodiments, retainers 210 and the retainers of this disclosure may be subjected to thermal expansion based at least in part on material properties of the retainers of this disclosure (e.g., retainers 210) and the operational conditions of the various devices, pistons (e.g., piston 200), and piston assemblies of this disclosure. The retainers of this disclosure, which are described as forming respective front lands, may, in some embodiments, never materially expand (e.g., based on thermal expansion) beyond a radial length (e.g., second radial length 220) of a rear land (e.g., rear land 216).

[0039] FIG. 3A shows piston 300, in accordance with some embodiments of the disclosure. Piston 300 may incorporate, or be incorporated into, any or all of the pistons and piston assemblies shown and described in reference to FIGS. 1, 2, and 4-6. Additionally, or alternatively, piston 300 may be incorporated, in whole or in part, into device 700 of FIG. 7. For example, piston 300, or any feature thereof, may be incorporated into any or all of the pistons and piston assemblies shown and described in reference to FIGS. 1, 2 and 4-7.

[0040] Piston 300 includes piston face 302 and circumferential groove 304. Piston face 302 includes central portion 306 and radially outward portion 308. Central portion 306 may, in some embodiments, at least partially define a reaction section of a device (e.g., device 700 of FIG. 7), may be axially adjacent to a reaction section of a device, or may contact a reaction section of a device. Radially outward portion 308 includes retainers 310, which extend radially outward relative to central portion 306. As shown in FIG. 3, ends 312 of an adjacentpair of retainers 310 are disconnected, thereby forming an azimuthal gap between ends 312. Piston face 302 has a surface profile that includes retainers 310 and central portion 306.

[0041] FIG. 3B shows portion 314 of piston 300 of FIG. 3 A, in accordance with some embodiments of the disclosure. Portion 314 includes retainers 310 which at least partially form circumferential groove 304 with rear land 316. Retainers 310 have axially front surface 318 and axially rear surface 320. Front surface 318 is shown with a curved profile that meets at retainer end 322 with a profile of rear surface 320. In some embodiments, a cross-sectional area between front surface 318 and rear surface 320 may include one or more of a radially tapered geometry, an axially tapered geometry, or an azimuthally tapered geometry such that retainer end 322 has a smaller thickness than a portion of retainer 310 radially closer to central portion 306 (e.g., retainer base 324). Any of the described tapered geometries reduce an overall piston weight, as compared to similar retainers without the described tapered geometries, and also may be configured to reduce a mass of each respective retainer towards a radially outward end of each respective retainer (e.g., which may be subjected to at least one of cantilever sourced stress or strain towards a radially inward base of each respective retainer). The described mass reduction may, in some embodiments, reduce at least one of mechanical stress or material strain at retainer base 324 which, in some embodiments, may be introduced to retainers of this disclosure based on repeated acceleration and deceleration of the pistons and piston assemblies of this disclosure (e.g., as would occur during operation of a device which generates energy based at least in part on movement of the pistons and piston assemblies of this disclosure along a bore of a cylinder).

[0042] FIG. 4 shows piston assembly 400, in accordance with some embodiments of the disclosure. Piston assembly 400 may incorporate, or be incorporated into, any or all of the pistons and piston assemblies shown and described in reference to FIGS. 1-3B, 5, and 6. Additionally, or alternatively, piston assembly 400 may be incorporated, in whole or in part, into device 700 of FIG. 7. For example, piston assembly 400, or any feature thereof, may be incorporated into any or all of the pistons and piston assemblies shown and described in reference to FIGS. 1-3B and 5-7.

[0043] Piston assembly 400 is illustrated from a planar perspective. Piston assembly 400 includes sealing ring assembly 402 arranged in circumferential groove 404, which is arranged axially rearward of piston face 406. Sealing ring assembly 402 may, in some embodiments, include features or segments similar to those depicted in, or described in relation to, FIG. 1. Piston face 406 includes central portion 408 and radially outward portion 410. Radially outward portion 410 includes retainers 412. As shown in FIG. 4, ends 414 of an adjacent pairof retainers 412 are disconnected thereby forming an azimuthal gap between ends 414. Piston face 406 has a surface profile that includes retainers 412 and central portion 408. As shown in FIG. 4, retainers 412 are at least radially angled towards ends 414. Ends 414 may, in some embodiments, include a rounded shape. Additionally, or alternatively, radially inward portions of retainers 412 (e.g., portions radially adjacent to central portion 410) may be azimuthally wider than ends 414.

[0044] FIG. 5 shows piston 500, in accordance with some embodiments of the disclosure. Piston 500 may incorporate, or be incorporated into, any or all of the pistons and piston assemblies shown and described in reference to FIGS. 1-4 and 6. Additionally, or alternatively, piston 500 may be incorporated, in whole or in part, into device 700 of FIG. 7. For example, piston 500, or any feature thereof, may be incorporated into any or all of the pistons and piston assemblies shown and described in reference to FIGS. 1-4, 6, and 7.

[0045] Piston 500 includes piston face 502 with central portion 504 and radially outward portion 506. Radially outward portion 506 includes retainers 508. In some embodiments, at least two adjacent retainers of retainers 508 are configured to at least axially retain a respective ring segment of a sealing ring assembly configured to be arranged in circumferential groove 510. Additionally, or alternatively, at least one ring segment of the multiple segments may be sufficiently short in circumferential, or azimuthal, length such that a single retainer of retainers 508 (e.g., tines) is configured to suitably retain the at least one ring segment in the circumferential groove for an operational lifetime of the at least one ring segment. Ends 512 of retainers 508 are disconnected and form an azimuthal gap between radially adjacent retainers of retainers 508. In some embodiments, retainers 508 may collectively form an axially front land that is axially forward of circumferential groove 510. As shown in FIG. 5, retainers 508 are a radial length that is shorter than a radial length of axially rear land 514. Circumferential groove 510 may, in some embodiments, be at least partially formed between retainers 508 and axially rear land 514.

[0046] FIG. 6 shows piston assembly 600, in accordance with some embodiments of the disclosure. Piston assembly 600 may incorporate, or be incorporated into, any or all of the pistons and piston assemblies shown and described in reference to FIGS. 1-5. Additionally, or alternatively, piston assembly 600 may be incorporated, in whole or in part, into device 700 of FIG. 7. For example, piston assembly 600, or any feature thereof, may be incorporated into any or all of the pistons and piston assemblies shown and described in reference to FIGS. 1-5 and 7.

[0047] Piston assembly 600 includes sealing ring segment 602 arranged axially rearward of retainer 604. Retainer 604 has distinct azimuthally separated ends 606. Ends 606 radially extend towards radially outward sealing surface 608 of sealing ring segment 602. Retainer 604 may, in some embodiments, be part of a radially outward portion of a piston face of piston assembly 600. As described in relation to other sealing ring assemblies and sealing ring segments herein, sealing ring segment 602 extends to a radial length that is longer than a radial length of retainer 604 (e.g., to prevent one or more of ends 606 from contacting a cylinder wall of a bore of a cylinder despite being subjected to thermal expansion in view of operation conditions of a device that may generate energy based on actuation of piston assembly 600 along said bore using reactions in a reaction section of the mentioned cylinder, which is not shown in FIG. 6 and may be exemplified in FIG. 7).

[0048] FIG. 7 shows a cross-sectional view of illustrative device 700 (e.g., a generator or linear generator) including two free piston assemblies 710 and 720 that include respective sealing ring assemblies 712 and 722, in accordance with some embodiments of the present disclosure. Free piston assemblies 710 and 720 may, in some embodiments, include any or all of the features shown in and described in reference to FIGS. 1-6. In some embodiments, device 700 may include linear electromagnetic machines 750 and 755 to convert between kinetic energy of respective free piston assemblies 710 and 720 and electrical energy. In some embodiments, device 700 may include gas regions 760 and 762, which may, for example, be at a relatively lower pressure than gas region 770 (e.g., one or more of a high- pressure region or a reaction section) for at least some, if not most, of a cycle (e.g., an operational cycle of a generator that relies on reactions of fuel and air mixtures for operation or an air compression cycle). For example, gas regions 760 and 762 (e.g., low pressure regions) may be open to respective breathing ducting (e.g., an intake manifold, an intake system, an exhaust manifold, an exhaust system). To illustrate, breathing ports 734 and 735 are configured to provide reactants to, and remove exhaust from, bore 732 of cylinder 730. In a further example, gas regions 760 and 762 may be vented at an atmospheric, ambient, or environmental pressure (e.g., at about 1.01 bar absolute pressure). In some embodiments, device 700 may include gas springs 780 and 785, which may be used to store and release energy during a cycle in the form of compressed gas (e.g., a driver section). For example, free piston assemblies 710 and 720 may each include respective pistons 782 and 787, each having respective grooves for accommodating respective sealing ring assemblies 781 and 786, to seal respective gas regions 783 and 788 (e.g., high- pressure regions) from respective gas regions 784 and 789 (e.g., low-pressure regions).

[0049] Cylinder 730 may include bore 732, centered about axis 772. In some embodiments, free piston assemblies 710 and 720 may translate along axis 772, within bore 732, allowing gas region 770 to compress and expand. For example, gas region 770 may be at relatively high pressure as compared to gas region 760 for at least some of a stroke of free piston assemblies 710 and 720 (e.g., which may translate along axis 772 in opposed piston synchronization). Sealing ring assemblies 712 and 722 may seal gas region 770 from respective gas regions 760 and 762 within bore 732. In some embodiments, free piston assemblies 710 and 720 may include respective pistons 714 and 724, and respective sealing ring assemblies 712 and 722, which may be arranged in respective corresponding grooves of pistons 714 and 724. It will be understood that gas regions 760 and 762, and gas region 770, may change volume as free piston assemblies 710 and 720 move or are otherwise positioned at different locations along axis 772. The portions of respective sealing ring assemblies 712 and 722 nearest gas region 770 are each termed the front, and the portion of sealing ring assemblies 712 and 722 nearest respective gas regions 760 and 762 are each termed the rear. Sealing ring assemblies 712 and 722 may each include a high- pressure boundary, which may each depend on a pressure in gas region 770. For example, a high-pressure boundary of sealing ring assembly 712 may be open to gas region 770, and have a corresponding pressure the same as, or less than, the pressure of gas region 770. Sealing ring assemblies 712 and 722 may each include a low-pressure boundary, which may depend on a gas pressure in respective gas regions 760 and 762. For example, a low-pressure boundary of sealing ring assembly 712 may be open to gas region 760, and have a corresponding pressure about the same as the pressure of gas region 760.

[0050] In some embodiments, pistons 714 and 724 may each include one or more grooves into which one or more respective sealing ring assemblies may be arranged. For example, as shown in FIG. 7, pistons 714 and 724 may each include one groove, into which sealing ring assembly 712 and sealing ring assembly 722 may be installed, respectively. In a further example, although not shown in FIG. 7, piston 714 may include two grooves, in which two respective components of sealing ring assembly 712 may be installed. A sealing ring assembly may be used to seal any suitable high-pressure and low-pressure regions from each other. For example, sealing ring assembly 786 is configured to seal high-pressure region 788 (e.g., a gas spring) from low-pressure region 789. In a further example, sealing ring assembly 781 is configured to seal high-pressure region 783 (e.g., a gas spring) from low-pressure region 784.

[0051] In some embodiments, free piston assemblies 710 and 720 may include respective magnet sections 751 and 756, which interact with respective stators 752 and 757 to form respective linear electromagnetic machines 750 and 755. For example, as free piston assembly 710 translates along axis 772 (e.g., during a stroke of an engine cycle), magnet section 751 may induce current in windings of stator 752. Further, current may be supplied to respective phase windings of stator 752 to generate an electromagnetic force on free piston assembly 710 (e.g., to effect motion of free piston assembly 710).

[0052] In some embodiments, pistons 714 and 724, sealing ring assemblies 712 and 722, and cylinder 730 may be considered a piston and cylinder assembly. In some embodiments, device 700 may be an engine, an air compressor, any other suitable device having a piston and cylinder assembly, or any combination thereof. In some embodiments, device 700 may be configured to operate according to a two-stroke cycle. Additionally, or alternatively, one or more portions of the two-stroke cycle may be completed based on the incorporation of at least one of homogenous charge compression ignition (HCCI) or uniflow scavenging during the one or more portions of the two-stroke cycle. In some embodiments, device 700 need not include two free piston assemblies. For example, cylinder 730 could be closed (e.g., with a cylinder head) , and free piston assembly 710 alone may translate along axis 772.

[0053] The systems and processes discussed above are intended to be illustrative and not limiting. One skilled in the art would appreciate that the actions of the processes discussed herein may be omitted, modified, combined, and / or rearranged, and any additional actions may be performed without departing from the scope of the invention. More generally, the above disclosure is meant to be exemplary and not limiting. Only the claims that follow are meant to set bounds as to what the present disclosure includes. Furthermore, it should be noted that the features and limitations described in any one embodiment may be applied to any other embodiment herein, and flowcharts or examples relating to one embodiment may be combined with any other embodiment in a suitable manner, done in different orders, or done in parallel. In addition, the systems and methods described herein may be performed in real time. It should also be noted that the systems and / or methods described above may be applied to, or used in accordance with, other systems and / or methods.

[0054] While some portions of this disclosure may refer to “convention” or examples, any such reference is merely to provide context to the instant disclosure and does not form any admission as to what constitutes the state of the art.

Claims

What is claimed is:

1. A pi ston compri sing : a piston face comprising: a central portion, and a plurality of retainers that extend radially outward relative to the central portion, wherein at least one pair of adjacent retainers of the plurality of retainers is disconnected at respective radially outward ends of the at least one pair of adjacent retainers.

2. The piston of claim 1, wherein the piston face comprises a surface profile comprised of the central portion and the plurality of retainers.

3. The piston of claim 1, wherein the plurality of retainers comprises at least one tine.

4. The piston of claim 1, wherein the plurality of retainers forms a front land, the piston further comprising: a rear land; and a circumferential groove between the front land and the rear land.

5. The piston of claim 4, wherein: the front land comprises a first radial length; the rear land comprises a second radial length; and the first radial length is less than the second radial length.

6. The piston of claim 1, wherein the plurality of retainers comprises at least one tapered retainer.

7. The piston of claim 1, wherein the plurality of retainers comprises at least one retainer of a trapezoidal geometry.

8. A piston assembly comprising: a sealing ring assembly; and a piston comprising: a circumferential groove that accommodates the sealing ring assembly; and a piston face comprising:a central portion, and a plurality of retainers that extend radially outward relative to the central portion, wherein at least one pair of adjacent retainers of the plurality of retainers is disconnected at respective ends of the at least one pair of adjacent retainers.

9. The piston assembly of claim 8, wherein: the sealing ring assembly comprises a plurality of segments, and each respective segment of the plurality of ring segments is at least axially retained by at least two adjacent retainers of the plurality of retainers.

10. The piston assembly of claim 8, wherein the piston face comprises a surface profile comprised of the central portion and the plurality of retainers.

11. The piston assembly of claim 8, wherein the plurality of retainers comprises at least one tine.

12. The piston assembly of claim 8, wherein the plurality of retainers form a front land, the piston further comprising: a rear land; and a circumferential groove between the front land and the rear land.

13. The piston assembly of claim 12, wherein: the front land comprises a first radial length; the rear land comprises a second radial length; and the first radial length is less than the second radial length.

14. The piston assembly of claim 8, wherein the plurality of retainers comprises at least one tapered retainer.

15. The piston assembly of claim 8, wherein the plurality of retainers comprises at least one retainer of a trapezoidal geometry.

16. A device comprising: a reaction section; anda piston configured to interface with the reaction section, the piston comprising: a piston face comprising: a central portion, and a plurality of retainers that extend radially outward relative to the central portion, wherein at least one pair of adjacent retainers of the plurality of retainers is disconnected at respective ends of the at least one pair of adjacent retainers.

17. The device of claim 16, wherein the reaction section is axially adjacent to the central portion.

18. The device of claim 16, wherein: the piston further comprises a circumferential groove configured to accommodate a sealing ring assembly; and the device is configured to allow a reaction to propagate from the reaction section into the circumferential groove.

19. The device of claim 18, wherein: the sealing ring assembly comprises a plurality of segments, and each respective segment of the plurality of ring segments is at least axially retained by at least two adjacent retainers of the plurality of retainers.

20. The device of claim 16, wherein the plurality of retainers comprises at least one tine.

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