EP1751398A1

EP1751398A1 - Rotary engine

Info

Publication number: EP1751398A1
Application number: EP05742445A
Authority: EP
Inventors: Anthony Osborne Dye
Original assignee: Epicam Ltd
Current assignee: Epicam Ltd
Priority date: 2004-05-11
Filing date: 2005-05-11
Publication date: 2007-02-14
Also published as: JP2007537395A; WO2005108745A1; GB0410491D0

Abstract

The present invention relates to a rotary device, comprising a first rotor rotatabe about a first axis and having at its periphery at least one recess bounded by a curved surface; a stator about which the first rotor is arranged for rotation; a second rotor counter-rotatable to said first rotor about a second axis, parallel to said first axis, and having at least one radial lobe bounded by a curved surface; the first and second rotors being coupled for inter-meshing rotation to produce a transient chamber of progressively increasing or decreasing volume defined between said curved recess and lobe surfaces of said first and second rotors; a housing in which the rotors are enclosed, said housing having end surfaces abutting end surfaces of said inter-meshing rotors; and a rotor port arranged to enable a flow of a gas into or out of said at least one recess in the recess rotor, the port having dimensions at least one of which is greater than the distance between the outermost extent of the stator and the minimum radius of the recess in the recess rotor.

Description

ROTARY ENGINE

The present invention relates to a rotary device for expansion and/or compression of gaseous fluid and to an engine including such a rotary device. By the term gaseous fluid is meant any compressible fluid, including a fuel and air mixture in an internal combustion engine.

In WO-A-91/06747, US 6,168,385B and US 6,176,695B, there is disclosed a rotary device for expansion and/or compression of gaseous fluid. The rotary device has first and second rotors coupled for counter rotation and intermeshed such that, for a part of the rotation of the rotors, there is defined between the first and second rotors a transient chamber of volume which progressively decreases or increases on rotation of the rotors. Valved ports allow flow of the compressed gaseous fluid. The rotary device has two main forms, first an internal combustion engine having separate rotary compression and expansion sections, and secondly a gas compressor. In the first form, a combustion chamber has valved inlet and outlet ports communicating with the compression and expansion chambers respectively. Each section is a rotary device comprising a first rotor rotatable about a first axis and having at its periphery a recess bounded by a curved surface; and a second rotor counter-rotatable to the first rotor about a second axis, parallel to the first axis, and having a radial lobe bounded by a curved surface, the rotors intermeshing whereby, on rotation thereof.

A transient chamber of progressively increasing (expansion section) or decreasing (compression section) volume is defined between them. The rotors are rotatable at a relative speed ratio, preferably 2:3 and are contoured such that during passage of the lobe through the recess, the recess surface is continuously swept, by both a tip of the lobe and a movable location on the lobe which progresses along the lobe surface, to define the transient chamber.

The second form relates to a fluid compressor in which a pair of rotors serve to compress and deliver compressible fluids into receivers in which the receiver pressure is substantially greater than that of the fluid source. Power is supplied by an external prime mover in order to drive the rotor pair and thus to compress the fluid, raising its pressure from that of the supply source to that of the receiver. In both forms of the prior art devices, the interaction of the rotors takes place between a pair of close-fitting side walls. One of the side walls contains a port for delivery of the fluid charge either to or from the rotors depending on whether they are effecting compression or expansion of the charge. Provision is made for mechanical or liquid seals between rotor/rotor and rotor/stator elements to reduce or virtually eliminate gas leakage during the operation of these machines. However, it is difficult to ensure that such seals remain in position and are capable of effective operation over a useful life because of the nature of the interaction between the rotors. There are, in any event, considerable disadvantages in the use of such seals due to the mechanical friction to which they give rise.

In a fluid compressor, the rotor pairs serve to compress and deliver compressible fluids into receivers in which the receiver pressure is substantially greater than that of the fluid source. Power is supplied by an external prime mover in order to drive the rotor pair and thus to compress the fluid, raising its pressure from that of the supply source to that of the receiver. For efficient operation of a positive displacement compressor, it is desirable to raise the pressure of the fluid charge to a level equal to that of the receiver before beginning to deliver the charge into the receiver. In the rotor system disclosed in WO-A-91/06747 there is a port in a side wall which communicates with a transfer passage in the recess rotor, as the transfer passage passes over the port.

This arrangement provides desirable means to control the timing of the start of delivery tlirough the port but it limits the maximum size of the port which it is possible to provide. This is because the area which is available for communication, adjacent to the end face of the recess rotor, necessarily lies at a smaller radius to the rotor than that of the minimum reached by the recess in the rotor. Thus, the area available for the port is limited because of its location at a small distance from the centre of the recess rotor, where it is clear of the sweep of the lobe. It is desirable that the operating speed of the compressor should not be unduly limited because of restricted flow capacity at the port. It is therefore desirable to provide means for locating both the port and its communication. In a rotary internal combustion engine having rotor systems as disclosed in WO-

A-91/06747, the rotors serve as positive and negative displacement systems, thereby effecting the volume changes which take place in the working fluid throughout the fheπnodynamic cycle of the engine. It is desirable in such internal combustion engines that the operating speed of the engine is not unduly limited by restricted flow capacity at the combustion chamber ports which communicate respectively with the compressor and expander transient chambers. It is therefore desirable to provide means for improving the flow capacity for both of the combustion chamber ports and their respective means of communication with transient compression and expansion chambers. According to a first aspect of the present invention, there is provided a rotary device, comprising: a first rotor rotatable about a first axis and having at its periphery at least one recess bounded by a curved surface; a stator about which the first rotor is arranged for rotation, the stator having a radius large enough such that it is capable of defining a passage for the flow of a gas; a second rotor counter-rotatable to said first rotor about a second axis, parallel to said first axis, and having at least one radial lobe bounded by a curved surface; the first and second rotors being coupled for inter-meshing rotation to produce a transient chamber of progressively increasing or decreasing volume defined between said curved recess and lobe surfaces of said first and second rotors; a housing in which the rotors are enclosed, said housing having end surfaces abutting said end surfaces of said inter-meshing rotors; a rotor port for communicating with said at least one recess in the recess rotor, the port having dimensions at least one of which is greater than the length of the distance between an outermost extent of the stator of the recess rotor and the minimum radius of the recess in the recess rotor. Preferably, the first and second rotors each have respective end surfaces spaced along their respective axes, said rotor port being provided in one of said end surfaces and one of said end surfaces of said housing has at least one associated port for communication with said at least one rotor port, the ports of the recessed rotor and the housing being valved by the action of abutting end surfaces of the recessed rotor and the housing during rotation of the rotors; and wherein said recessed rotor includes a valving portion defining said at least one port of the recessed rotor and a main portion defining said at least one recess, with said valving portion and said main portion being located side by side along the axis of the recessed rotor, and in which the said at least one port on the recessed rotor and the said at least one port on the housing each extends radially outwardly from the axis of the recessed rotor at least to some extent beyond the innermost extent of the recess in the recessed rotor.

Preferably, the stator is a stator cylinder comprising a port. A corresponding rotor port is provided on the at least one recess wherein upon rotation of the rotor relative to the stator cylinder the port on the stator cylinder and the port on the rotor are intermittently aligned, the recess being valved by interaction between the stator cylinder and an inner cylindrical surface of the first rotor arranged in rotatable slidable engagement with the stator cylinder.

According to a second aspect of the present invention, there is provided a rotary device, comprising: a first rotor rotatable about a first axis and having at its periphery at least one recess bounded by a curved surface; a second rotor counter-rotatable to said first rotor about a second axis, parallel to said first axis, and having at least one radial lobe bounded by a curved surface; the first and second rotors being coupled for inter-meshing rotation to produce a transient chamber of progressively increasing or decreasing volume defined between said curved recess and lobe surfaces of said first and second rotors; a housing in which the rotors are enclosed, said housing having end surfaces abutting said end surfaces of said inter-meshing rotors; the first axis comprising a hollow cylindrical member, the hollow cylindrical members being mounted within a correspondingly sized hollow cylindrical bore within the first rotor and having a port arranged thereon to enable communication between an interior of the axis and an exterior thereof through said port; the recess in the first rotor having at least one port for enabling communication between the central bore within the rotor and the recess, the port on the first axis and the port on the rotor each being configured such that upon rotation of the rotor with respect to the first axis the ports are intermittently aligned.

According to a third aspect of the present invention there is provided a rotary device, comprising: a first rotor rotatable about a first axis and having at its periphery at least one recess bounded by a curved surface, the first rotor having end surfaces spaced apart along its axis; a second rotor counter-rotatable to said first rotor about a second axis, parallel to said first axis, and having at least one radial lobe bounded by a curved surface, the second rotor having end surfaces spaced apart along its axis; the first and second rotors being coupled for inter-meshing rotation to produce a transient chamber of progressively increasing or decreasing volume defined between said curved recess and lobe surfaces of said first and second rotors; a housing in which the rotors are enclosed, said housing having end surfaces abutting said end surfaces of said inter-meshing rotors; one of said end surfaces of said first, recessed, rotor having at least one port communicating with said at least one recess of the rotor, and one of said end surfaces of said housing having at least one associated port for communication with said at least one rotor port, the ports of the recessed rotor and the housing being valved by the action of abutting end surfaces of the recessed rotor and the housing during rotation of the rotors; in which said recessed rotor includes a valving portion defining said at least one port of the recessed rotor and a main portion defining said at least one recess, with said valving portion and said main portion being located side by side along the axis of the recessed rotor, and in which the said at least one port on the recessed rotor and the said at least one port on the housing each extends radially outwardly from the axis of the recessed rotor at least to some extent beyond the innermost extent of the recess in the recessed rotor. It is much preferred that the said at least one port on the recessed rotor and said at least one port on the housing are each positioned so as to be located only at a position radially outwardly of the said innermost extent of the recess in the recessed rotor.

In a convenient form of construction of a device according to the invention, said valving portion of said recessed rotor comprises an end wall extending perpendicular to the axis of the recessed rotor and arranged to close off part of one end of the rotor recess. The other end of the rotor recess may be closed off by a further end wall of the housing. Conveniently the said at least one port of the recessed rotor is a port through the first said end wall of the recessed rotor. Conveniently the said valving portion comprises a disc perpendicular to and coaxial with the first axis and arranged to rotate with the said main portion of the first, recessed, rotor. It is particularly preferred that said curved surfaces are contoured such that during passage of said lobe through said recess, said recess surface is continuously swept by both a tip of said lobe and a movable location on said lobe which location progresses along said lobe surface, to define said transient chamber. Although it may be arranged that the rotors are axially uniform, with the recess and the lobe extending uniformly in the axial direction, it is much preferred that said at least one recess and at least one lobe each extends helically in the axial direction.

Preferably the speed of rotation of the first, recessed, rotor is lower than the speed of rotation of the second, lobed rotor of the device by a ratio, less than 1 : 1 of whole numbers.

Also preferably the first and second rotors have respectively equi-angularly spaced recesses and lobes in the same ratio of number of recesses to number of lobes as the speed ratio, of the lobed rotor to the recessed rotor. In some arrangements, the first rotor has three equiangularly disposed recesses and the second rotor has two diametrically opposed lobes, the ratio of their speeds of rotation being 2:3. In some arrangements it may be arranged that two or more of said second lobed rotors intermesh with the same first recessed rotor.

It is preferred that the rotors are enclosed in a housing having first and second arcuate recesses which are coaxial respectively with the first and second rotors and which form a sliding seal therewith, such that for a portion of a turn before and/or after the lobe passes through the recess in the first rotor, there is defined between the rotors and the housing an additional transient chamber of progressively increasing or decreasing volume which communicates with the transient chamber between the rotors.

Although it is to be appreciated that an embodiment of the present invention may consist merely of a rotary device for compressing gaseous fluid, or a rotary device for accepting compressed gaseous fluid which drives the rotary device in rotation, the invention finds particular application in an internal combustion engine consisting of both rotary compression and rotary expansion sections. In such an arrangement there is provided an internal combustion engine comprising separate rotary compression and expansion sections and a combustion chamber having inlet and outlet ports communicating with said compression and expansion sections respectively, in which each of said compression and expansion sections is a rotary device according to any form set out in the preceding paragraphs.

According to a fourth aspect of the present invention, there is provided an internal combustion engine comprising separate rotary compression and expansion sections and a combustion chamber having inlet and outlet ports communicating with said compression and expansion sections respectively, in which each of said compression and expansion sections is a rotary device according to any of the first to third aspects of the present invention.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:- Figure 1 is a schematic longitudinal section of part of an internal combustion engine embodying the present invention, taken on a plane passing through respective axes of the rotors of compression and expansion sections thereof, each of which sections comprises a rotary device embodying the present invention;

Figure la shows an enlargement of a combustion chamber shown in Figure 1;

Figure lb is a diagrammatic side view partly in perspective, of the compression section of the internal combustion engine of Figure 1, showing a housing surrounding the compression rotors;

Figures 2a, 2b and 2c are respectively schematic cross sections of the interacting rotors of the compression section showing successive stages in the compression cycle of the engine;

Figures 3a, 3b and 3c are respectively schematic cross sections of the interacting rotors of the expansion section showing successive stages in the expansion cycle of the engine. Figure 4a shows an end surface of a valving portion of a recessed rotor shown in the embodiment of Figure 1;

Figure 4b shows a side view of a wall of the housing of the embodiment shown in the embodiment of Figure 1; and

Figure 5 is a diagrammatic representation of a section through the two compression rotors forming part of the embodiment shown in Figure 1, viewed from the compression rotors looking towards a centre wall of the embodiment; Figure 6 is a diagrammatic representation of a section through the two rotors of

Figure 5 viewed from the centre wall looking towards the rotors; Figure 7 is a view, corresponding to that of Figures 2a, 2b, 2c, of a housing surrounding the compression rotors shaped to coact with the rotors in the compression cycle; Figure 8 is a similar view to that of Figure 7 but corresponding to Figures 3 a, 3b and 3 c showing the housing surrounding the expansion rotors to coact with the rotors in the expansion cycle; and

Figures 9a to 9f show respectively schematic cross sections of the interacting rotors of the compression section of the embodiment of Figure 1 showing successive stages in the compression cycles of the engine, and provide further explanation of the stages shown in Figures 2a, 2b, and 2c.

Figure 10 is a diagramatic side view partly in perspective of an example of a rotor for use in the present invention;

Figures 11 to 13 show examples of the rotor of figure 10 in various configurations during a rotation cycle; Figures 14A to 14H show respectively schematic cross sections of the interacting rotors of an expander showing successive stages in an expansion cycle;

Figures 15A to 15H show respectively schematic cross sections of the interacting rotors of a compressor showing successive stages in a compression cycle; and,

Figure 16 shows a two-dimensional end view of a rotor pair with provision for both radial and axial ports.

Referring to Figure 1, an internal combustion engine embodying the present invention comprises a pair of outer walls 1 and 2, and a parallel intermediate wall 3 all secured in a fixed assembly. In each of the outer walls 1, 2 there are roller bearings 8, and in the intermediate wall 3 there are ball bearings 9, to carry parallel shafts 10 and 11. The shaft 10 carries at one end a keyed gear pinion 12, and the shaft 11 carries at the same end a keyed pinion 13, the two pinions meshing and having a speed ratio of 2:3 as between pinion 13 and pinion 12. Each of the shafts 10 and 11 carries respective keyed compression rotors 14a, 14b

(shown further in Figures 2a to 2c) and keyed expansion rotors 15a, 15b (shown further in Figures 3a to 3c). Each rotor has end surfaces spaced apart along its axis, each rotor forming a substantially gas-tight sliding fit between the walls 1 and 3, and 2 and 3 respectively. A housing 25 (shown in Figures lb, 7 and 8 and to be described hereinafter) is disposed about the assembly so as to provide an intake chamber about the compression rotors, and an exhaust chamber about the expansion rotors. In the intermediate wall 3, and communicating with both end faces thereof, is a combustion chamber 16, the shape of which is explained in more detail below with reference to Figure la. As shown in Figures 2a, b and c, the first compression rotor 14b has at its periphery three recesses R, S, T, each bounded by a curved surface and the second compression rotor 14a has two radial lobes P, Q, each bounded by a curved surface. As shown in Figures 3a, b and c, the first expansion rotor 15b has at its periphery three recesses W, X, Y, each bounded by a curved surface, and the second expansion rotor 15a has two radial lobes V, U, each bounded by a curved surface.

The compression rotor 14b and the expansion rotor 15b each has ports communicating respectively with the recesses therein and with the combustion chamber, as will be described in detail hereinafter, particularly with reference to Figures 9a to 9f. However, the overall structure will first be described with reference to Figures 1 and la, and Figures 4a, 4b, 5 and 6. In Figures 5 and 6, the diagrammatic representation takes the form of diagrammatic thin slices of the rotors and a representative portion of the stationary wall 3.

Considering first the compression section, the recessed rotor 14b has a main portion 19a defining the recesses and a valved portion 19 in the form of a disc coaxial with and fixedly mounted to the main portion 19a. The disc 19 closes off part of one end of each rotor recess, the other end of each rotor recess being closed off by the end wall 1. The disc 19 includes three ports 20 which give communication between the respective recesses of the rotor 14b, and the combustion chamber 16 during that time when a rotor port 20 overlaps with an inlet port 21 of the combustion chamber 16. Thus the size and shape and location of the ports 20 in the disc 19 determines the extent and timing of the communication between the recesses of the rotor 14b, and the combustion chamber 16.

Similar arrangements are made at the expansion rotors 15b and 15a. A corresponding disc 19b is fixedly mounted relative to a main portion 19a of the rotor 15b, and includes three corresponding ports (not shown in Figure 1) to allow the expanding combustion gases to pass from the combustion chamber 16 into the recesses of the expansion rotor 15b, as will be described in detail hereinafter.

The thickness of the disc 19 (in the axial direction) forming the valving portion of the recessed rotor 14b may be restricted to the minimum necessary for structural support but its thickness represents an addition to the axial length of the first rotor 14b. Each member of the rotor pair (14b, 14a) is the same length, apart from the disc 19. Thus the interaction of a lobe as it passes through a recess, takes place with a minimal clearance between the end face of the lobe and the inner face of the disc. A circular recess is provided in the wall 3 of the engine to allow the disc 19 to fit into the circular recess, leaving only a small clearance between the disc 19 and the port 21. This also allows a small clearance to be maintained between the end face of the lobe rotor 14a and the wall 3 of the device. Thus leakage from the transient chamber and combustion chamber 16 may be controlled by the limited clearances between rotor/rotor and rotor/stator components throughout the interactions of the rotor and port components which occur during each cycle of operation of the device.

In the arrangement described above, in which a disc 19 is provided having a port to enable the gas flow into and out of a transient chamber defined between a recess and lobe of rotor pair 14a and 14b, it will be appreciated that a port of any desired size may be provided so long as it may be defined within the disc 19. The port may have dimensions at least one of which is greater than the distance between the central axis of the recess rotor and the minimum radius of the recess in the recess rotor. In other words, the port has or may have at least one dimension that is greater than the length of the radial dimension of the largest port which it is possible to locate within the minimum radius of the recess for a given rotor size.

This contrasts with the port provided in the known rotary device described in WO-A-91/06747. Accordingly, the porting arrangement provided in examples of embodiments of the present invention enables improved and/or increased gas flow into or out of the transient chamber to be achieved and consequently enables faster rotational speeds of the rotary device to be achieved.

Prior to the detailed description of the valving, there will be given a general description of the operating cycle of the engine, which is generally the same as the prior art disclosure in WO-A-91/06747. First, the compression rotors 14a, 14b, and compression phase will be described in detail with reference to Figures 2a, 2b and 2c. In Figure 2a, lobed rotor 14a is the faster rotor, and recessed rotor 14b is the slower rotor. These rotors together constitute a rotary device embodying the invention. Rotor 14a has radial lobes "P" and "Q" which are identical in shape and which are shaped in a computer-determined manner to fit into and co-operate with recesses "R", "S" and "T" of rotor 14b. A gaseous working fluid, e.g. a fuel/air mixture, or air alone when a fuel injection system is used, is provided in the housing surrounding the rotor 14b and fills the recesses "R", "S" and "T" therein. The compression cycle of the rotor recess commences when the two rotors 14a and 14b are in the position shown in Figure 2a. In this position, a charge of the working fluid is entrapped between the rotors, between the clearances at a tip 17 and a heel 18 of the rotor 14a within the recess "R".

Compression of the charge in the recess "R", is effected as the rotors proceed to the position of Figure 2b, when the entrapped volume between the rotors has been diminished by the displacement action of the moving rotors. As the charge of working gaseous fluid is compressed it is delivered via the rotor port 20 disposed in a side surface of the rotor 14b which faces the internal wall 3. During the whole of the compression phase, this rotor port 20 communicates with the inlet port 21 of the combustion chamber 16, in the intermediate wall 3. The compression phase is completed at the position of Figure 2c, when the entrapment volume has been reduced to solely the clearance volume between the respective parts of the two rotors. At this position, the rotor port 20 ceases to communicate with the stationary entry port 21, thus trapping the compressed charge in the combustion chamber 16.

The combustion chamber 16 has at its other end an outlet port 22. During the whole of the combustion phase, the outlet port 22 is closed off by an adjacent wall of the expansion rotor 15b described in greater detail below. Thus, during the combustion phase both the inlet port 21 and the outlet port 22 of the combustion chamber are effectively closed by the adjacent end surfaces of the respective rotors 14b and 15b, and in this way the compressed charge of gaseous fluid has its volume constrained to remain constant during the combustion phase. Assuming that a fuel/air mixture is used, ignition is obtained by means of a spark plug 23 which has its tip exposed in or to the interior of the combustion chamber 16. It will be known to those skilled in the art of internal combustion engines that fuel injection with heat-ignition can be substituted for spark ignition to provide a compression ignition version of the engine. The release of heat by the combustion of the fuel causes a substantial pressure rise to occur in the combustion chamber. The expansion rotors and the expansion phase will now be described with reference to Figures 3a, 3b and 3c. In Figure 3a, lobed rotor 15a is the higher speed rotor and recessed rotor 15b is the lower speed rotor. These rotors together also constitute a rotary device embodying the invention. Rotor 15a has radial lobes "U" and "V" which are identical in shape and which are shaped in a computer-determined manner to fit into and co-operate with recesses " ", "X" and "Y" of rotor 15b.

The expansion phase commences when the two rotors reach the position of Figure 3a. In this position, a rotor port (not shown) on the recessed rotor comes into communication with the delivery port 22 of the combustion chamber 16. The volume defined between the respective portions of the two rotors 15a, 15b is then placed in communication with the combustion chamber 16 which is full of "gaseous fluid under very high pressure following combustion. The gaseous fluid under pressure in the volume defined between the two rotors urges the rotors to rotate into the position of Figure 3b, and the process of expansion is continuous, with a resultant application of moments of force to both of the rotors to urge them to continue their rotation in the same direction. The rotors eventually reach the position of Figure 3 c wherein the rotors reach the limit of entrapment of the fluid, and after further rotation the exhaust gases leave the entrapment zone by the continuing displacement action of the rotors.

Reference is now made to Figures 7 and 8 which show how the housings of the compression and expansion sections act to extend the compression and expansion cycles of the engine. The housing 25 is shaped so as to mate with "sliding", (i.e. minimal), clearance with the two rotors over a part of their rotating movement. Figure 7 shows the commencement of entrapment of a volume "J" which diminishes as rotation proceeds until the gaseous fluid is reduced in volume to that shown between lobe "P" and the surface bounding recess "R" in Figure 2a, so that overall a greater compression is achieved than would be the case with the recess in the rotor alone.

Figure 8 shows that the exhaust gases escaping finally from between the rotor lobe and rotor recess as shown in Figure 3c, remain confined in the space "K" so that further work is extracted from the expanding gases until both rotors have moved a considerable further distance in rotation, whereafter the gases are released into the remainder of the housing.

The description so far has referred only to a cross section through each rotor and is applicable either to a simple cylindrical rotor, or to a more complex shape. A preferred arrangement has each rotor of helical configuration and this is shown schematically by way of example in Figure lb for the compression section of the engine of Figure 1. For simplicity, the valving disc 19 is omitted from Figure lb.

The rotors 14b, 14a are enclosed by the housing 25. Indeed, one or both of the end walls 1, 2 may be a part of the housing 25. The housing 25 is shaped to have a first arcuate recess 31 which is shaped so that the trailing edge 42 of each recess of the first rotor 14b is a sliding fit with the first arcuate recess 31. The housing 25 is also shaped to have a second arcuate recess 32 which is shaped so that the leading edge 62 of a lobe of the second rotor 14a is a sliding fit with the second arcuate recess 32 of the housing 25.

A transient chamber J (which is shaded in Figure 7) is formed between a recess of the first rotor 14b, a lobe of the second rotor 14a and the arcuate recesses 31, 32 of the housing 25 when the trailing and leading edges 42, 62 of a recess and lobe respectively enter the arcuate recesses 31, 32. The transient chamber J is used to compress a working gaseous fluid. The volume of the transient chamber J decreases as rotation of the rotors 14b, 14a proceeds from the position shown in Figure lb at which the leading edge 62 of a lobe of the second rotor 14a is just about to enter the second arcuate recess 32 of the housing 25 and the trailing edge 42 of a recess of the rotor 14b is just about to enter the first arcuate recess 31. As can be seen in Figure lb, the rotors extend helically parallel to their respective axes. The helix angles of the rotors match their respective rotational speeds so that the ratio of the helix angles is the same as the ratio of the rotational speeds of the rotors. For example, the helix angle for the first, recessed rotor 14b may be 20° and the helix angle for the second, lobed rotor 14a may be 30°. The arcuate recesses 31, 32 are helically shaped to match the helical shapes of the recesses and lobes.

The description so far has referred to the overall compression and expansion cycles without reference to the particular kind of valving provided. This will now be described in detail with reference to Figures 9a to 9f, and Figures 4a, 4b, 5 and 6. Figure 4a shows an end surface of the valving portion 19 of the recessed rotor 14b shown in the embodiment of Figure 1, and Figure 4b shows a side view of the wall 3 of the housing 25 of the embodiment shown in Figure 1. Figures 9a to 9f show respectively schematic diametral sections of the interacting rotors of the compression section of an internal combustion engine according to the invention. They show successive stages in the compression cycle of the engine.

Figure 9a shows the position just after the start of compression. The tip 17 of the lobe P of the second rotor 14a and the trailing edge of the recess R of the first rotor 14b, have formed a transient chamber within the volume contained by the close fitting housing 25 (not shown in Figure 9a), within which they have trapped a gaseous charge. The lobe P is about to enter the recess R, with the end face of the lobe P closely adjacent to the disc 19. The leading edge of the aperture 20 in the disc 19 has already passed the opening edge of the port 21 in the end wall, thus establishing communication between the recess R and the port 21 leading into the combustion chamber 16 (not shown in Figure 9a).

Figure 9b shows the position slightly later, when further compression of the charge has taken place and the leading edge of the aperture 20 has traversed further across the port 21, thus increasing the flow area through which the increasingly compressed charge is being delivered.

Figure 9c shows the position at which the flow area has passed a maximum as the curved end face of the lobe P reduces the available flow area.

Figures 9d and 9e show the position towards the end of compression, where the remaining volume of the compressed charge is small and the remaining flow area is likewise small.

Figure 9f shows the position shortly after the end of compression where the trailing edge of the aperture 20 has passed the closing edge of the port 21, thus sealing the charge in the combustion chamber. As has been mentioned, it is important to realise that embodiments of the invention may be constructed for use as a simple compressor of gaseous fluid. In such a case, the construction consists of only the compression section of the internal combustion engine shown in the preceding figures, and the shafts of the rotors are driven by an external source of power. Where the device is a compressor, the leading edge of the aperture and the approach edge of the port can be suitably located so that the opening of the port can be timed to coincide with pressure equalisation between the transient chamber and a receiver. Furthermore, in other modifications, the compression of the gaseous material may be limited to the interaction between the lobe of the lobed rotor and the recess of the recessed rotor, rather than having additional compression due to the interaction between the lobed rotor and the recessed rotor, and with the surrounding housing, as shown in Figure lb. Finally it should be appreciated that the lobed rotor may include a single lobe or a plurality of lobes, and similarly the recessed rotor may include a single recess or a plurality of recesses.

It is a particular advantage, at least of the preferred embodiments of the invention, that it is possible to provide significantly larger flow areas through the ports of the recessed rotor and the housing side wall, by arranging for these to extend radially outwardly beyond the innermost extent of the recess in the rotor. In previous known arrangements as discussed in WO-A-91/06747, it was only possible to provide ports which were positioned inwardly of the innermost extent of the recess on the recessed rotor. Such ports necessarily were of small area, and this limited the speed of rotation of an internal combustion engine embodying the invention. In a typical example the speed of rotation was limited to about 3000 rpm. The present invention finds particular use in internal combustion engines operating at relatively high speeds, for example greater than 6000 rpm and preferably in the range 10000 to 15000 rpm. In both rotary devices of the type disclosed in WO-A-91/06747, the means for gaseous communication between the transient chambers and the fixed ports was provided by a chamfered groove or passage in the recess rotor which communicated with a port fixed in the stationary wall of the device. As the recess rotor rotated, the communication between the chamfered groove or passage in the rotor and the fixed port in the stationary wall necessarily took place in a restricted area close to the centre of the recess rotor. This limited the maximum flow area which was available for such communication. It is desirable to have a port of larger dimensions such that its flow capacity does not unduly limit the performance of the rotary devices. Also, the volume of the chamfered groove represented a significantly large "dead" volume, whereas in the present invention, this "dead" volume is restricted to that of the area of the transfer port 20 and the thickness of the disk 19. Figure 10 shows a schematic representation of a rotor for use in an example of an alternative embodiment of the present invention. The arrangement of figure 10 comprises a rotor 40 and a stator cylinder 42 about the axis of rotation of the rotor 40. The stator cylinder has a radius large enough such that it is capable of defining a passage through which a gas can flow. The rotor 40 and stator cylinder 42 are shown in exploded view although it will be appreciated that in use the stator cylinder 42 is arranged within a central bore 44 within the rotor 40 to enable rotation of the rotor 40 with respect to the stator cylinder 42. The stator cylinder 42 has a substantially hollow centre defining a passage so that it is able to function as a conduit for a gas.

The stator cylinder 42 is provided with a port 46 and the rotor 40 is provided with a port 48 that in combination enable communication via a passage 47 from within the recess of the rotor 40 to the passage within stator cylinder 42 or vice versa in dependence on whether the device is operating as an expander or a compressor. The ports 46 and 48 are sized and positioned such that on rotation of the rotor 40 relative to the stator cylinder 42 the ports 46 and 48 will become aligned for a period of time during each cycle of rotation of the rotor 40.

Figures 11 to 13 show respective views of the rotor 40 and stator cylinder 42 during various stages of the rotation of the rotor 40 relative to the stator cylinder 42.

Referring to figure 11, at this point of the cycle of rotation of the rotor 40 with respect to stator cylinder 42 the port 46 within the stator cylinder 42 is not visible. Referring to figure 12, as the rotor continues to rotate relative to the stator cylinder 42 the port 46 within stator cylinder 42 becomes visible through the port 48 in rotor 40.

Once the port 46 becomes visible through port 48, communication between the passage within the stator cylinder 42 and the recess in rotor 40 becomes possible.

Referring now to figure 13, the rotor 40 has continued to rotate and so a larger proportion of the port 46 is now visible through port 48 in the recess of rotor 40. As the rotor 40 continues to rotate relative to the stator cylinder 42 there will come a point at which the overlap between the ports 48 and 46 are such that the cross section of a passage between the recess of the rotor 40 and the interior of the stator cylinder 42 becomes a maximum. Further rotation will then start to decrease the cross section of the overlap area. In other words, the port 46 will be closed by the rotor 40. In the example shown in Figures 10 to 13 it will be appreciated that the size of the ports in the rotor (and on the stator cylinder) may be selected such that sufficient flow of gas may be achieved between the recess in the rotor and the interior region of the stator cylinder 42. The ports extend axially with respect to the longitudinal axes of the stator cylinder 42 and of the rotor 40. In other words, at least in the axial direction, the ports are not limited by the radial distance between the stator cylinder 42 and the innermost extent of the recess.

Figures 14A to 14H show rotor end profiles at stages through a cycle for the rotary device when used as an expander. Referring to Figure 14 A, a cycle of an expander begins when a lobe surface U and a recess surface W of a pair of engaging rotors pass the point of maximum penetration of the lobe, i.e. as the tip of the lobe passes the point of minimum radius of the recess surface W. At this stage, the leading edge of the recess rotor passage 47 approaches an opening edge of the port 46 within the stator cylinder 42, to which a pressurised fluid supply has access. Referring to figure 14B, as the port 46 opens, pressurised fluid passes into the recess rotor passage 47 and into a newly foπning transient volume between the lobe and recess.

Referring to figure 14C, the port 46 is now fully open, providing maximum flow capacity for the pressurised fluid to pass through into the transient volume defined between lobe surface U and recess surface W. This minimises any pressure differential between that of the fluid supply and that occurring in the transient volume. The pressure of the pressurised fluid acts on the surfaces U of the lobe and W of the recess, thus urging the rotors into further action in the direction of rotation. In Figure 14D, a trailing edge of the recess rotor passage 47 approaches the closing edge of the port 46 which starts to shut off the supply of pressurised fluid to the chamber defined between the lobe and recess. Referring to Figure 14E, the trailing edge of the recess rotor passage 47 reaches the closing edge of the port 46, thus closing off the supply of pressurised fluid and isolating the fluid which has already passed into the transient volume. As can be seen in Figure 14F, rotation of the rotors causes the transient volume to increase, thus allowing the trapped fluid to expand whilst maintaining some pressure on the surface of the lobe U and recess W and continuing to energise the rotation of the rotors and any shafts to which they may be connected.

Referring to Figure 14G, the transient volume reaches its maximum capacity and the fluid reaches ambient pressure. At this point the fluid ceases to exert any net pressure on the lobe U and recess W surfaces prior to its release to the housing surrounding the rotor pair.

Last, in Figure 14H, the fully expanded fluid is released from the transient volume and may be released to an exhaust system under the natural pumping action of the rotor pair within their housing.

Figures 15 A to 15H show rotor end profiles at stages through a cycle for the rotary device when used as a compressor. Each one of Figures 15A to 15H shows a profile section through the lobe and pocket rotors and a moveable containment wall at a point close to an air intake end of the rotary device. In the examples shown, the lobe rotor shaft allows passage for intake air, which is released into a central region of the compressor plenum via radially directed passages. The recess rotor also has a hollow centre which rotates about a close-fitting stator cylinder. The stator cylinder has a port 46 and each of the recesses of the pocket rotor has a passage 47 for communication with a respective port 46 in the stator cylinder.

Referring to Figure 15 A, as the rotors rotate in the directions indicated (lobe rotor clockwise, recess rotor counter-clockwise) a lobe P and recess R approach each other. Engagement between the lobe P and recess R and moveable containment wall 101 serves to entrap a transient volume J within the moveable wall section 101. Referring now to Figure 15B, the fluid contained in the transient volume J is now entrapped and becomes compressed as the rotors continue to rotate.

Referring now to Figure 15C, the transient volume J has been substantially compressed but the fluid remains trapped as the recess rotor passage 47 has not yet rotated to a position corresponding to the port 46.

In Figure 15D, the transient volume J is now contained entirely by the surfaces of the lobe P and recess R. The leading edge of the recess rotor passage 47 has now reached the opening edge of the port 46 and fluid flow begins to take place through the port. At this stage, the pressure of the trapped fluid has reached that of the receiver and further rotation of the rotors will result in progressive delivery of the charge of gas compressed within the variable volume chamber between the lobe R and recess P. In Figure 15E, the leading edge of the recess rotor passage 47 has now traversed approximately halfway across the port 46, thus increasing the variable flow area at the throat of the port 46. In Figure 15F, the recess rotor passage 47 is now in alignment with the port 46, thus providing maximum flow area for delivery of the charge. In Figure 15G, the trailing edge of the recess rotor passage 47 is now approaching the closing edge of the port 46 and the port is starting to close. The remaining transient volume is very small and thus contains a small mass of charge still to be transferred tlirough the port. Last, in Figure 15H, the transient volume has now been eliminated and only a clearance volume remains between the lobe surface P and that of the recess R. Closure of the port 46 coincides with the completion of the compression action, which occurs when the tip of a lobe reaches the point of minimum radius of the pocket. A new transient volume has now been formed between the next lobe and recess pair.

The size of the port 46 in the stator cylinder and the corresponding port in the rotor may be selected such that sufficient flow of gas may be achieved between the recess in the rotor and the interior region of the stator cylinder 42 as required both when the rotary device functions as an expander and when it functions as a compressor. As explained above with reference to Figures 10 to 13, the ports extend axially with respect to the longitudinal axes of the stator cylinder 42 and of the rotor 40. In other words, at least in the axial direction the ports are not limited by the maximum radial distance between the stator cylinder 42 and the minimum radius of the recess.

Figure 16 shows a two-dimensional end view of a rotor pair with provision for both radial and axial ports. The arrangement shown includes a lobed rotor 14A and a recessed rotor 14B. An end plate 19 is arranged on an end surface of the recessed rotor 14B. The end plate 19 has a number of ports 20 as shown in and described above with reference to Figures 9 A to 9F. In addition, a stator cylinder 42 arranged in the central bore of the recessed rotor 14B has a hollow passage with a port 46. A number of radial passages 47 are provided between the inner cylindrical surface of a bore within the rotor 14B and each of the recesses (shown in dotted lines) of the rotor 14B. An end wall of the housing within which the rotor pair would in use normally be arranged is not shown. However, it will be appreciated that such a housing wall would be provided with a port 21 as shown in and described above with reference to Figure 4B. In use, the rotor pair shown in Figure 16 define a variable volume transient chamber between the curved surfaces of a recess of the recess rotor 14B and a lobe of the lobed rotor 14A. The ports 20 (in the end plate 19) and 46 (in the axis 42) provide two separate means by which a gas flow can be provided to or received from the transient chamber defined between a mating lobe and recess.

The direction of gas flow, i.e. whether it flows into or out of the transient chamber depends on whether the rotary device is operating as a compressor or an expander. In both cases, it is possible to provide parts for communication with the transient chamber both axially and radially as shown in Figure 16.

It will be appreciated that numerous modifications to and departures from the preferred embodiments described above will occur to those having skill in the art. Thus, it is intended that the present invention covers the modifications and variations of the invention, provided they come within the scope of the appended claims and their equivalents.

Claims

1. A rotary device, comprising: a first rotor rotatable about a first axis and having at its periphery at least one recess bounded by a curved surface, a stator about which the first rotor is arranged for rotation; a second rotor counter-rotatable to said first rotor about a second axis, parallel to said first axis, and having at least one radial lobe bounded by a curved surface; the first and second rotors being coupled for inter-meshing rotation to produce a transient chamber of progressively increasing or decreasing volume defined between said curved recess and lobe surfaces of said first and second rotors; a housing in which the rotors are enclosed, said housing having end surfaces abutting end surfaces of said inter-meshing rotors; a rotor port arranged to enable a flow of a gas into or out of said at least one recess in the recess rotor, the port having dimensions at least one of which is greater than the distance between the outermost extent of the stator and the minimum radius of the recess in the recess rotor.

2. A rotary device according to claim 1, in which the first and second rotors each have respective end surfaces spaced along their respective axes, said rotor port being provided in one of said end surfaces and one of said end surfaces of said housing has at least one associated port for communication with said at least one rotor port, the ports of the recessed rotor and the housing being valved by the action of abutting end surfaces of the recessed rotor and the housing during rotation of the rotors; and wherein said recessed rotor includes a valving portion defining said at least one port of the recessed rotor and a main portion defining said at least one recess, with said valving portion and said main portion being located side by side along the axis of the recessed rotor, and in which the said at least one port on the recessed rotor and the said at least one port on the housing each extends radially outwardly from the axis of the recessed rotor at least to some extent beyond the innermost extent of the recess in the recessed rotor.

3. A rotary device according to Claim 2, in which the said at least one rotor port and said at least one port on the housing are each positioned so as to be located only at a position radially outwardly of the said innermost extent of the recess in the recessed rotor.

4. A rotary device according to Claim 2 or 3, in which said valving portion of said recessed rotor comprises an end wall extending peφendicular to the axis of the recessed rotor and arranged to close off part of one end of the rotor recess.

5. A rotary device according Claim 4, in which the other end of the rotor recess is closed off by a further end wall of the housing.

6. A rotary device according to Claim 4 or 5, in which the said at least one rotor port is a port through the first of said end walls of the recessed rotor.

7. A rotary device according to any of Claims 4 to 6, in which the said valving portion comprises a disc peφendicular to and coaxial with the first axis and arranged to rotate with the said main portion of the first, recessed rotor.

8. A rotary device according to any preceding claim, in which said curved surfaces are contoured such that during passage of said lobe through said recess, said recess surface is continuously swept by both a tip of said lobe and a movable location on said lobe which location progresses along said lobe surface, to define said transient chamber.

9. A rotary device according to any preceding claim, in which said at least one recess and at least one lobe each extends helically in the axial direction.

10. A rotary device according to any preceding claim, in which the speed of rotation of the first, recessed, rotor is lower than the speed of rotation of the second, lobed rotor of the device by a ratio, less than 1 :1 of whole numbers.

11. A rotary device according to Claim 10, in which the first and second rotors have respectively equiangularly spaced recesses and lobes in the same ratio of number of recesses to number of lobes as the speed ratio, of the lobed rotor to the recessed rotor.

12. A rotary device according to any preceding claim, in which the rotors are enclosed in a housing having first and second arcuate recesses which are coaxial respectively with the first and second rotors and which form a sliding seal therewith, such that for a portion of a turn before and/or after the lobe passes through the recess in the first rotor, there is defined between the rotors and the housing an additional transient chamber of progressively increasing or decreasing volume which communicates with the transient chamber between the rotors.

13. A rotary device according to claim 1, wherein the stator is a cylinder and comprises a port and the rotor port is provided on the at least one recess wherein upon rotation of the rotor relative to the axis the port on the stator cylinder and the rotor port are intermittently aligned, the recess being valved by interaction between the stator cylinder and an imier cylindrical surface of the first rotor arranged in rotatable slidable engagement with the stator cylinder.

14. A rotor according to claim 13, in which the port on each of the stator cylinder and the rotor extend axially with respect to the rotor.

15. A rotary device according to claim 14, in which the ports on each of the stator cylinder and the rotor extend for a length substantially equal to the axial length of the rotor.

16. A rotary device according to any of Claims 13 to 15, in which the rotors are enclosed in a housing having first and second arcuate recesses which are coaxial respectively with the first and second rotors and which form a sliding seal therewith, such that for a portion of a turn before and or after the lobe passes through the recess in the first rotor, there is defined between the rotors and the housing an additional transient chamber of progressively increasing or decreasing volume which communicates with the transient chamber between the rotors.

17. A rotary device, comprising: a first rotor rotatable about a first axis and having at its periphery at least one recess bounded by a curved surface; a second rotor counter-rotatable to said first rotor about a second axis, parallel to said first axis, and having at least one radial lobe bounded by a curved surface; the first and second rotors being coupled for inter-meshing rotation to produce a transient chamber of progressively increasing or decreasing volume defined between said curved recess and lobe surfaces of said first and second rotors; a housing in which the rotors are enclosed, said housing having end surfaces abutting end surfaces of said inter-meshing rotors; a stator cylinder about which the first rotor is arranged for rotation, the stator cylinder being a hollow cylindrical member, the hollow cylindrical member being mounted within a correspondingly sized hollow cylindrical bore within the first rotor and having a port arranged thereon to enable communication between an interior of the stator cylinder and an exterior thereof through said port; the recess in the first rotor having at least one port for enabling communication between the central bore within the rotor and the recess, the port on the stator cylinder and the port on the rotor each being configured such that upon rotation of the rotor with respect to the stator cylinder the ports are intermittently aligned.

18. A rotary device according to claim 17, in which one of said end surfaces of said first, recessed, rotor has at least one rotor port communicating with said at least one recess of the rotor, and one of said end surfaces of said housing has at least one associated port for communication with said at least one rotor port, the ports of the recessed rotor and the housing being valved by the action of abutting end surfaces of the recessed rotor and the housing during rotation of the rotors; in which said recessed rotor includes a valving portion defining said at least one rotor port and a main portion defining said at least one recess, with said valving portion and said main portion are located side by side along the axis of the recessed rotor, and in which the said at least one port on the recessed rotor and the said at least one port on the housing each extends radially outwardly from the axis of the recessed rotor at least to some extent beyond the innermost extent of the recess in the recessed rotor.

19. A rotary device, comprising: a first rotor rotatable about a first axis and having at its periphery at least one recess bounded by a curved surface, the first rotor having end surfaces spaced apart along its axis; a second rotor counter-rotatable to said first rotor about a second axis, parallel to said first axis, and having at least one radial lobe bounded by a curved surface, the second rotor having end surfaces spaced apart along its axis; the first and second rotors being coupled for inter-meshing rotation to produce a transient chamber of progressively increasing or decreasing volume defined between said curved recess and lobe surfaces of said first and second rotors; a housing in which the rotors are enclosed, said housing having end surfaces abutting said end surfaces of said inter-meshing rotors; one of said end surfaces of said first, recessed, rotor having at least one port communicating with said at least one recess of the rotor, and one of said end surfaces of said housing having at least one associated port for communication with said at least one rotor port, the ports of the recessed rotor and the housing being valved by the action of abutting end surfaces of the recessed rotor and the housing during rotation of the rotors; in which said recessed rotor includes a valving portion defining said at least one port of the recessed rotor and a main portion defining said at least one recess, with said valving portion and said main portion being located side by side along the axis of the recessed rotor, and in which the said at least one port on the recessed rotor and the said at least one port on the housing each extends radially outwardly from the axis of the recessed rotor at least to some extent beyond the innermost extent of the recess in the recessed rotor.

20. An internal combustion engine comprising separate rotary compression and expansion sections and a combustion chamber having inlet and outlet ports communicating with said compression and expansion sections respectively, in which each of said compression and expansion sections is a rotary device according to any preceding claim.