Patent ID: 12196154

DETAILED DESCRIPTION

Referring toFIG.1, a rotary internal combustion engine, referred to simply as a rotary engine below, which may be a Wankel engine, is schematically shown at10. The rotary engine10comprises an outer body also referred to as a housing assembly12having axially-spaced side housings11, which each includes a side wall14and a side plate16mounted to the side wall14, with a rotor housing18extending from one of the side housings11to the other, to form a rotor cavity20. The rotor housing18has a first side and a second side opposite to the first side. The side housings11include a first side housing secured to the first side and a second side housing secured to the second side. The rotor cavity20is defined axially between the side housings11and circumscribed by the rotor housing18. InFIG.1, the side wall14is indicated with a dashed line because it sits below the side plate16. The inner surface of the rotor housing18has a profile defining two lobes, which may be an epitrochoid. In some alternate embodiments, the side housings11include solely the side wall, that is, the side wall and the side plate may be combined into a single element.

The housing assembly12includes a coolant circuit12A, which may include a plurality of coolant conduits18B defined within the rotor housing18. As shown more clearly inFIG.5, the coolant conduits18B extends from one of the side housings11to the other. The coolant circuit12A is used for circulating a coolant, such as water or any suitable coolant, to cool the housing assembly12during operation of the rotary engine10. Although only two coolant conduits18B are shown, it is understood that more than two coolant conduits18B may be used without departing from the scope of the present disclosure.

An inner body or rotor24is received within the rotor cavity20. The rotor24has axially spaced end faces26adjacent to the side walls14, and a peripheral face28extending there between. The peripheral face28defines three circumferentially-spaced apex portions30, and a generally triangular profile with outwardly arched sides36. The apex portions30are in sealing engagement with the inner surface of rotor housing18to form three rotating combustion chambers32between the rotor24and housing assembly12. The combustion chambers32vary in volume with rotation of the rotor24within the housing assembly12. The geometrical axis of the rotor24is offset from and parallel to the axis of the housing assembly12. In some embodiments, more or less than three rotating combustion chambers may be provided with other shapes of the rotor.

The combustion chambers32are sealed. In the embodiment shown, each rotor apex portion30has an apex seal52extending from one end face26to the other and biased radially outwardly against the rotor housing18. An end seal54engages each end of each apex seal52and is biased against the respective side wall14. Each end face26of the rotor24has at least one arc-shaped face seal60running from each apex portion30to each adjacent apex portion30, adjacent to but inwardly of the rotor periphery throughout its length, in sealing engagement with the end seal54adjacent each end thereof and biased into sealing engagement with the adjacent side plates16of the side housings11. Alternate sealing arrangements are also possible.

Although not shown in the Figures, the rotor24is journaled on an eccentric portion of a shaft such that the shaft rotates the rotor24to perform orbital revolutions within the rotor cavity20. The shaft may rotate three times for each complete rotation of the rotor24as it moves around the rotor cavity20. Oil seals are provided around the eccentric to impede leakage flow of lubricating oil radially outwardly thereof between the respective rotor end face26and side housings11. During each rotation of the rotor24, each chamber32varies in volumes and moves around the rotor cavity20to undergo the four phases of intake, compression, expansion and exhaust, these phases being similar to the strokes in a reciprocating-type internal combustion engine having a four-stroke cycle.

The engine includes a primary inlet port40in communication with a source of air and an exhaust port44In the embodiment shown, the ports40,44are defined in the rotor housing18. Alternate configurations are possible.

In a particular embodiment, fuel such as kerosene (jet fuel) or other suitable fuel is delivered into the chamber32through a fuel port (not shown) such that the chamber32is stratified with a rich fuel-air mixture near the ignition source and a leaner mixture elsewhere, and the fuel-air mixture may be ignited within the housing using any suitable ignition system known in the art (e.g. spark plug, glow plug). In a particular embodiment, the rotary engine10operates under the principle of the Miller or Atkinson cycle, with its compression ratio lower than its expansion ratio, through appropriate relative location of the primary inlet port40and exhaust port44.

Referring now toFIGS.2-5, one of two side housings11of the housing assembly12is illustrated. As briefly introduced above, the side housings11include the side walls14that are secured to the rotor housing18. Each of the side walls14has a portion located proximate an outer perimeter P (FIG.4) of the side wall14and configured to be in abutment against the rotor housing18for defining the rotor cavity20.

In the embodiment shown, each of the side walls14is configured to be secured to a respective one of opposed ends of the rotor housing18. The side housings11further include side plates16located on inner sides of the side walls14. The side plates16define rotor-engaging faces16A on which the side seals60and the corner seals54of the rotor24are in abutment during rotation of the rotor24. The side plates16further define back faces opposite the rotor-engaging faces16A. The back faces of the side plates16face the side walls14.

The side walls14may be made of aluminum, more specifically an aluminum alloy, due to its light weight and high thermal conductivity. However, it may be required that the surfaces of the side walls14in contact with the seals54,60be coated to provide a wear-resistance surface. In the embodiment shown, the side plates16are made of aluminum and coated with a hard material such as silicon carbide, aluminum nitride, chromium carbide, tungsten carbide, and so on. Any suitable wear resistant coating applied by thermal spray or any other suitable method may be used. The side walls14and the side plates16will be described in more details below. Although the text below uses the singular form, the description may be applied to both of the side walls14and to both of the side plates16. The side plates16may however be entirely made of the hard material, such as silicon carbide. The side plates16may be made of aluminum, steal, or any suitable ceramic.

Referring more particularly toFIG.4, the side wall14includes a peripheral section14A, which is in abutment with the rotor housing18, and a center section14B, which is circumferentially surrounded by the peripheral section14A. In the disclosed embodiment, the peripheral section14A of the side wall14is secured to the rotor housing18. The center section14B of one of the side walls14faces the center section14B of the other of the side walls14. The side walls14are secured to the rotor housing18with any suitable means known in the art. As shown, a sealing member19is located between the rotor housing18and the peripheral sections14A of the side walls14for limiting coolant and combustion gases from leaking out. The sealing member19may be an O-ring. The sealing member19may be received within an annular recess, which may be defined by one or more of the rotor housing18and the side wall14.

The side wall14defines a recess14C for receiving the side plate16. The peripheral section14A of the side wall14extends from the outer perimeter P to the recess14C. As shown, a surface14D of the peripheral section14A of the side wall14that faces the rotor housing18is axially offset from a surface14E of the center section14B of the side wall14. A magnitude of the offset corresponds to a depth of the recess14C and may correspond to a thickness t of the side plate16plus any axial gap defined between a rotor-engaging face of the side plate16and the rotor housing18. The side plate16is therefore in abutment with the surface14E of the center section14B of the side wall14. In other words, a sealing surface of the side plate16, located on a side of the side plate16that faces the rotor cavity, may be aligned with the peripheral section14A of the side wall14.

The side wall14defines an abutment surface14F. The abutment surface14F is defined by a shoulder created by the offset of the surfaces14D,14E of the peripheral and central sections14A,14B of the side wall14. The side wall14, via its abutment surface14F, limits radial movements of the side plate16relative to the axis of rotation of the rotor24. The side plate16may be supported by a housing in the center to limit the movement of the side plate16.

In a particular embodiment, a gap may remain between a peripheral section of the side plate16and the abutment surface14F of the side wall14. In other words, and in the embodiment shown, the side plate16may be spaced apart from the abutment surface14F. A size of the gap may change during operation of the rotary engine10as the side wall14and the side plate16may expand at different rates with an increase of a temperature in the rotor cavity20. In other words, the space between the side plate16and the abutment surface14F of the side wall14may allow relative thermal expansion between the side plate16and the side wall14so that thermal stress transferred from the side plate16to the rotor housing18and the side wall14might be minimized.

To limit axial movements of the side plate16relative to the axis of rotation of the rotor24(FIG.1), a periphery of the side plate16is contained axially between the rotor housing18and the side wall14. In other words, the periphery of the side plate16is sandwiched between the side wall14and the rotor housing18. A seal70is located at the periphery of the side plate16for limiting the combustion gases to leak out of the rotor cavity20and for limiting the cooling fluid from leaking into the combustion chamber32(FIG.1). As shown more specifically inFIGS.4-5, the seal70is contained within a groove16B defined by the side plate16. The seal70is described in detail below.

In a particular embodiment, the seal70and the abutment surface14F of the side wall14allows the side plate16to move radially relative to the side wall14. Such a movement, along a radial direction relative to the axis of rotation of the rotor24, may be required in a configuration in which the side wall14is made of a material having a coefficient of thermal expansion different than that of the side plate16and/or because the different components may be exposed to different temperatures and, thus may exhibit different thermal expansion.

The side wall14further defines a pocket14G that may circumferentially extend a full circumference of the side wall14. In other words, the pocket14G is annular. More than one pocket may be used. The pocket14G may not cover an entirety of the center section14B of the side wall14. The pocket14G is configured for circulating a liquid coolant, such as water for cooling the side plate16. The pocket14G may be part of the coolant circuit12A and is in fluid flow communication with the coolant conduits18B that are defined in the rotor housing18. The pocket14G extends from the surface14E of the center section14B and away from the rotor cavity20. A depth D (FIG.5) of the pocket14G is defined by a distance along the axis of rotation of the rotor24between the surface14E of the center section14B and a bottom surface14H of the pocket14G.

As shown inFIGS.2-3, the peripheral section14A of the side wall14defines a plurality of ribs14I that are circumferentially distributed around the rotor cavity20. The ribs14I defines the abutment surface14F and a portion of the surface14E of the center section14B of the side wall14. Consequently, and in the depicted embodiment, the abutment surface14F is defined by a plurality of surfaces defined by the ribs14I. The ribs14I may be configured to support a pressure load imparted by a combustion of a mixture of air and fuel within the combustion chambers32.

Cavities or spaces14J are defined between the ribs14I. More specifically, each pair of two consecutive ones of the ribs14I defines a space14J therebetween. The spaces14J are in fluid communication with the pocket14G and with the coolant conduits18B of the rotor housing18. Stated otherwise, the coolant conduits18B are in fluid communication with the pocket14G via the spaces14J between the ribs14I. The spaces14J may allow the liquid coolant to flow from the pocket14G to the coolant conduits18B of the rotor housing18. It is understood that the liquid coolant may be circulated in closed loop and through a heat exchanger. The heat exchanger may be used to dissipate heat to an environment outside the engine; the heat transferred from the engine to the liquid coolant.

As shown inFIGS.2and5, a flow F1of the liquid coolant circulates within the pocket14G. The flow F1is divided in sub-flows F2; each of the sub-flows F2circulating within a respective one of the spaces14J and within a respective one of the coolant conduits18B of the coolant circuit12A. The liquid coolant may be circulated out of the housing assembly12and within a heat exchanger for extracting the heat. The liquid coolant may then be reinjected in the coolant circuit12A for further heat extraction.

Referring now toFIG.6, another embodiment of the outer body, more specifically of the side housing111and rotor housing118, is generally shown. For the sake of conciseness, only elements that differ from the housing assembly12ofFIGS.2-5are described. In the embodiment shown, the rotor housing118defines a groove118C that receives the seal70.

The description below refers more particularly to the embodiment ofFIG.7in which the rotor housing118defines a groove annularly extending around the axis of the housing assembly12. It will however be appreciated that the principles of the present disclosure apply equally to the embodiment ofFIG.4in which the seal70is received within a recess or a groove defined by the side plate116. In some embodiments, the seal70maybe received within a groove or recess defined conjointly by both the rotor housing18and the side plate116. The seal70may thus be located outwardly of the inner face of the rotor housing18and overlaps a peripheral section of the side housing111. This peripheral section corresponds to the section of the side housing111or side plate116that is overlapped by the rotor housing118. Herein, since the side housing111includes a side wall14secured to the rotor housing118and a side plate116, the peripheral section corresponds to a section of the side plate116that is dispose axially between, or sandwiched, between the rotor housing118and the side wall14.

Referring now toFIG.7, the seal70is used to prevent leakage of the combustion gases out of the rotor cavity20and to prevent the liquid coolant from leaking out of the coolant circuit12A. However, there is a gap G defined axially between the side plate116and the rotor housing118. This gap G is present to ensure that the side plate116is not within the engine clamping stack and thus to avoid transmitting axial load generated by fastening the rotor housing118to the side housings111. The coolant flowing within the coolant circuit12A is used to maintain the metal temperatures around the seal70within an acceptable level. However, in the embodiment shown, the gap G has a dimension of about 0.004″±0.0007. Other dimensions are contemplated. The gap G is sized to reduce the loading of the side plates116due to thermal expansions. As a result, the gap G may remain open at some circumferential locations during operation of the engine. This may allow hot combustion gases to impinge on the seal70. The seal70of the present disclosure may be designed to withstand these harsh operating conditions. The seal70may adequately seal the rotor cavity20from the coolant circuit12A and limit axial clamping load on the side plates116to less than 5000 lbs.

In the embodiment shown, the seal70includes an elastomeric member71and a metallic member72, also referred to as a metallic seal. The elastomeric member71is compressed between the peripheral section of the side housing111and the rotor housing118. More specifically, the elastomeric member71is compressed between the peripheral section of the side plate116and the rotor housing118, herein within the groove118C. The elastomeric member71may be made of any suitable material such as, for instance, Viton™, silicone, perfluoroelastomer, fluorocarbon-based fluoroelastomer, and so on.

The metallic member72is disposed inwardly of the elastomeric member71relative to the axis of rotation of the rotor24(FIG.1). The metallic member72is therefore located radially between the inner face of the rotor housing118and the elastomeric member71; the inner face of the rotor housing118being in sealing contact with the rotor24. The metallic member72is in contact with both of the peripheral section of the side housing111and the rotor housing118, herein in contact with both of the rotor housing118within the groove118C and with the side plate116. The elastomeric member17and metallic member72contact both of the rotor housing118and the side plate116and may be compressed therebetween. The metallic member72is made of a material having a melting point above a temperature of combustion gases inside the rotor cavity20. Thus, the metallic member72may be able to protect the elastomeric member71from impingement with hot combustion gases exiting the rotor cavity20via the gap G.

The elastomeric member71may have a substantially round shape when not received in the groove118C of the rotor housing118. However, this groove118C typically extends annularly all around the rotor cavity20and may have a shape matching that of the housing assembly12. Thus, the elastomeric member71may have an epitrochoid, ellipsoid, or oval shape when inserted into the groove118C. As illustrated, the elastomeric member71is disposed radially outwardly of the metallic member72. The metallic member72axially overlaps an entirety of the elastomeric member71to avoid leaving exposed a portion of the elastomeric member71. The elastomeric member71and the metallic member72axially overlap one another relative to a central axis thereof. Both of the elastomeric member71and the metallic member72may be continuous along a full circumference. However, in some embodiments, the metallic member72may include a plurality of shield segments circumferentially distributed and secured to one another.

Referring toFIG.8, the seal70is shown. The elastomeric member71may have a rounded shape, but may be sufficiently compliant to adopt an oval, ellipsoid, or epitrochoid shape when received within the groove. The metallic member72may be less compliant due to its stiffness. Hence, the metallic member72may be manufactured with the epitrochoid, ellipsoid or oval shape corresponding to that of the groove since it may be less compliant.

As aforementioned, the axial force exerted by the metallic member72is preferably high enough to seal, but not too high in order to still permit movements of the side plate116due to thermal growth. The metallic member72of the present disclosure may satisfy these requirements.

Referring now toFIG.9, the metallic member72is shown in greater details. The metallic member72has a cross-section defining an E-shape. In other words, the metallic member72has a cross-section that includes at least two crests72A and a valley72B disposed between the at least two crests72A. The metallic member72may have more than two crests72A and more than one valley72B. The metallic member72is compressible in a direction being parallel to the axis. In other words, the metallic member72is compressible by decreasing a distance between the two crests72A. Put differently, the metallic member72may have a sinusoidal shape defining a plurality of U-shaped sections interconnected to one another. The metallic member72may thus have W-shape. As shown inFIG.11, the metallic member72may include two flanges each abutting a respective one of the side plate116and the rotor housing118. The two flanges may be movable towards one another upon compression of the metallic member72in a direction parallel to the axis. The two flanges may end at tips. The tips may face the rotor cavity.

The metallic member72has a thickness t, a height c, a width M, and a number of crests72A and valley(s)72B that are selected such that a pressure force generated by the metallic member72on the side plate116is at most about 150 pounds by inch of length of the metallic member72during operation (e.g., hot) of the rotary engine10. Preferably, the pressure force generated by the metallic member72is at most 100 pounds by inch of length of the metallic member72during operation of the rotary engine10. The thickness t, the height c, the width M, and the number of crests72A and valley(s)72B are also selected such that the pressure force generated by the metallic member72on the side plate116is at least 25 pounds by inch of length when the rotary engine10is non-operating (e.g., cold). Any seals able to withstand the temperature of the combustion gases and able to generate at least 25 pounds by inch and at most from 100 to 150 pounds by inch of pressure are contemplated.

Referring now toFIGS.10-11, in a default, or at-rest shape of the seal70, both of the elastomeric member71and the metallic member72have a height that is greater than a depth D (FIG.11) of the groove118C.FIG.10illustrates that, with the side plate116removed, the metallic member72and the elastomeric member71protrude out of the groove118C while being abutted against a bottom wall of the groove118C. Thus, once the side plate116is installed, the elastomeric member71and the metallic member72are biased in a compressed shape in which they exert an axial force on both of the rotor housing118and the side plate116. This force may effectively seal the combustion chamber from the coolant passages.

In an alternate embodiment, the metallic member72may be a W-seal, or any other suitable metallic member made of a material able to withstand the harsh temperatures of the combustion gases. This material may be, for instance, Inconel™ or Titanium. These metallic members may not be able to provide sufficient sealing, thus the use of the elastomeric material. However, if a metallic member were able to provide adequate sealing, it may also exert too high of an axial load on the side plate116, which is undesirable.

Some metallic members, such as some configurations of C-seals, may be unsuitable for this application because they would provide an axial pressure greater than the aforementioned threshold. The metallic member72disclosed herein was found to provide the adequate compromise between sealing and axial pressure.

Referring now toFIG.12, another embodiment of a seal is shown at170. In the embodiment shown, the seal170includes the metallic member72and the elastomeric member71described above, but further includes a liner173, which may be made of high-temperature silicone, polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), or any other suitable material. The liner173may be disposed radially (e.g., sandwich) between the elastomeric member71and the metallic member72. The liner173may axially overlap both of the metallic member72and the elastomeric member71.

The liner173may have two functions. The first is to provide a mechanical support by presenting a harder surface for the metallic member72to seat when combustion pressure tries to displace it radially toward the elastomeric member71. The second function is to insulate the elastomeric member71from being in direct contact with the high temperature metal, therefore transferring heat that may degrade its mechanical properties.

Referring now toFIG.13, another embodiment of a seal is shown at270. In this embodiment, the seal270includes the metallic member72described above with an elastomeric member271having a rounded or circular cross-sectional shape instead of a polygonal shape.

Referring now toFIG.14, another embodiment of a seal is shown at370. In the embodiment shown, the seal370includes the elastomeric member271of the embodiment ofFIG.13, although it may alternatively includes the elastomeric member71of the embodiment ofFIG.10, the metallic member72, and a protection ring374. The seal370is received within a groove318of another embodiment. The groove318has two sections, namely a first section318A and a second section318B. A depth of the second section318B is greater than a depth of the first section318A. The “depth” is taken in the axial direction relative to the rotation axis of the rotor24of the rotary engine10. The protection ring374has a L-shape cross-section and has two legs: one of the two legs sits within the second section318B of the groove318and the other of the two legs is disposed radially between the elastomeric member271and the metallic member72. The protection ring374may be made of stainless steel or any other suitable material. The protection ring374may improve wear of the rotor housing118and may isolate the metallic member72from the elastomeric member271.

Since the metallic member72operates at elevated temperature, it may be desirable to isolate the elastomeric member271from the metal seal direct contact. The protection ring374may reduce the heat transfer to the elastomeric member271by preventing a direct contact and by diffusing heat in the protection ring374. In turn, this heat is partially dissipated to the rotor housing118where it contacts the protection ring374at the second section318B of the groove318.

Referring now toFIG.15, another embodiment of a seal is shown at470. In the embodiment shown, the seal470includes the elastomeric member271of the embodiment of FIG.13, although it may alternatively includes the elastomeric member71of the embodiment ofFIG.10, the metallic member72, and a protection ring474, similar to the protection ring374described above with reference toFIG.14. For the sake of conciseness, only features differing from the seal370ofFIG.14are described below.

In this embodiment, the leg of the protection ring474that sits within the second section318B of the groove318has two chamfers474A each located on a respective one of opposite sides of a face474B that abuts the rotor housing118within the groove318.

The chamfers may ensure positive contact at the second section318B of the groove318. This contact may provide more efficient heat flow between the two parts. The chambers474A on the protection ring474may prevent mechanical contact between the protection ring474and the rotor housing118at locations where the groove318defines fillets. In other words, if the chamfers were absent, a contact between an edge of the protection ring474and a fillet may create a gap between the protection ring474and a bottom face of the second section318B of the groove318. The chamfers474A may prevent such a contact.

Referring now toFIG.16, a method of sealing a rotor cavity of a rotary internal combustion engine is shown at1600. The method1600includes: mitigating leakage of combustion gases out of the rotor cavity with the elastomeric member71,271disposed at an interface between the rotor housing18,118and the side housing11secured to the rotor housing18,118at1602; and protecting the elastomeric member71,271from the combustion gases with the metallic member72disposed between the elastomeric member71,271and the rotor cavity at1602.

In the present embodiment, the protecting of the elastomeric member71,271from the combustion gases with the metallic member72includes compressing the metallic member72, which may be an E-seal, between the rotor housing18and the side housing11.

The embodiments described in this document provide non-limiting examples of possible implementations of the present technology. Upon review of the present disclosure, a person of ordinary skill in the art will recognize that changes may be made to the embodiments described herein without departing from the scope of the present technology. Yet further modifications could be implemented by a person of ordinary skill in the art in view of the present disclosure, which modifications would be within the scope of the present technology.