EP2847430A2

EP2847430A2 - Rotary-piston engine1

Info

Publication number: EP2847430A2
Application number: EP13728443.6A
Authority: EP
Inventors: William Gruet
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-05-10
Filing date: 2013-05-07
Publication date: 2015-03-18
Anticipated expiration: 2033-05-07
Also published as: US9771934B2; US20150093278A1; CN104302872B; IN2014DN09527A; WO2013167843A2; WO2013167843A3; EP2847430B1; CN104302872A

Abstract

The present invention relates to a so-called rotary piston engine or pump, which includes a shape F that is rotationally symmetrical relative to a delta axis, and which is rotatably movable about said delta axis relative to a casing V, wherein n cavities are distributed along the perimeter of F. A rotating roller is accommodated in each cavity, characterised in that the angle formed by at least one roller with the centre is determined so as to form the closed spaces defined thereby such that they are as large as possible.

Description

Rotary piston engine

The present invention relates to engines and pumps called rotary piston.

Current combustion engines consist of a piston that moves in the same direction, and this momentary movement is transformed into circular motion by a connecting rod and a crankshaft. This movement that changes meaning several tens or hundreds of times a second is a real problem, well known, on which we will not return. From this comes the idea of trying to design a motor with a piston that would have a circular motion. There is no real answer to this so far, although the interest and the stakes are considerable

The only rotary piston engine that has been built in series is the "Wankel" engine. But its shortcomings, which are complex, have meant that it has never really happened, despite the massive investment in research and development it has been the subject of time and again.

Engines of the same category as that which will be presented here have been the subject of patents: US Pat. No. 1,003,263A (191), GB 570,776 (1945), FR 1,489,283 (1967), US Pat. 188,602 B1 (2007), and US 5,819,699 A (1998).

None of these engines were manufactured or gave away. None of these patents mention a fluid passage from one side of the piston to the other.

Furthermore, in US Pat. No. 1,003,263A, US Pat. No. 7,188,602 B1 and US Pat. No. 5,819,699 A, the secondary piston, or roller, has a flat elliptical shape in contrast to the shape of the motor roller presented here. In patent FR 1 489 283 A, the roller remains parallel to itself, whereas this particular case is excluded here, considered as ineffective. The closest concept would be that described in the provisional specification ("provisional specifications") of GB 570 776 A. The final description proper ("complete specifications"), to transform the idea of the provisional description into a motor, results in a result different from the motor presented here for at least two reasons: the piston and the roller do not rotate at proportional speeds (a system of gearing to 2 d iameters changes the speed ratio during the cycle) and the main piston has a different shape.

In this rather brief provisional description, no indication is given on how to obtain the desired geometry, does not demonstrate the existence of a geometric solution to the problem, which is far from obvious, especially when the tip of the rotary piston is enlarged as is the case. Furthermore, the roller has an angle at the center of 180 °, unlike the solution presented here, in which this angle is less than 180. It is shown that if this angle is not less than 180 °, the order from 100 to 160, the engine has diminished characteristics. ⁰

Recall that a mechanical system to obtain a variable volume, can create pumps, motors if it is sufficiently rigid. The engine may be internal explosion, or moved by a fluid under pressure.

We will use from now on the term engine, but it will be necessary to understand engine thermal or moved by a fluid under pressure (steam, oil, air, ... etc.), Or pump (suction, repressing, ...).

To do this, the present invention relates to an engine comprising mainly:

a form of revolution F with respect to a delta axis and mobile in rotation about said delta axis relative to a V envelope. This means that this form F can be mobile, and in this case has a movement of rotation around its delta axis. It can also be fixed, and in this case, it is the envelope V which revolves around delta. F and V can both rotate around delta, and it is the relative rotation that will be taken into account.

- F has n (n being an integer) cells A_i (i being the ith, and i <= n) which are forms of revolution of axis β_ί. They are distributed around the perimeter of F. The intersections of each cell A_i with the form F are: T_i and U_i.

- In each cell A_i is housed a roller G_i which rotates about the axis β_ί, and has at least 2 faces, G_i_1 and G_i_2. The first of these faces G_i_1 is able to seal with the cell A_i at certain times of the system cycle when this face is inside the cell Aj. The section by a plane perpendicular to β_ί is an arc of circle (R_i, S_i) centered on β_ί in P_i, of ends R_i and S_i, of angle in the center (R_i, P_i, S_i), which could also be called angle in the center (G_i_1). We can locate the position of Gj by the position of the center P_i and the rotation angle Θ of the axis of symmetry (P_i, z) of the arc (R_i, S_i) with respect to an initial position.

a mechanical means (such as a set of gears, preferably toothed belts, transmission shafts, etc.), which makes the rotation of each Gj around β_ί proportional to the relative rotation of delta axis of the form F with respect to the envelope V.

Thus, suppose that we have defined: an orthonormal coordinate system Ox, Ow an initial position of the system: Pos_0 at a time tO, the angle ω (ί) to identify the relative rotation of the form F with respect to the envelope V thus, when the form F makes a turn (ω = 360 °) with respect to the envelope V, each G_i is made m revolutions with respect to its initial position, m being an integer, positive or negative in the direction.

In other words, at any moment t, θ (t) = m ^* ω (t), t being the time We exclude m for 2 particular cases: a) m = 1, because the wheel turns then as if it were fixed at F, and b) m = 0, because in this case P_iy is always parallel to Ox, and this case is considered to be of no interest.

of the envelope V which, if it is mobile, rotates about the delta axis, and which is the envelope generated by the rollers G_i in their rotational movement around the β_ί themselves driven by F, and the rotation relative delta axis of the form F with respect to the envelope V.

the face G_i_2 of Gj is the envelope generated by the envelope V at the level of Gj. Thus the seal between Gj and the envelope V is ensured, the assembly is made so that, if we consider a section by a plane perpendicular to delta, the envelope V, the shape F and one of the ends of the arc G_i_1 of G_i: either Rj or Sj, are in contact in one place, at a particular moment of the cycle.

The first position such as this one, relative to G_1, is the position Pos_1, obtained for an angle ω = ω1 (called limit angle), the place: common to V, F and G_1: C1.

- Of side walls or cheeks J1 and J2 on which rest the shape F, the rollers Li, and the envelope V,

The envelope V, the shape F, the rollers Gj, the cheeks J1 and J2 delimit closed and variable volumes at different moments of the cycle of the relative rotation of F with respect to V. To ensure the tightness of the closed volume, the various parts may be provided with seals, segments or any other sealing means

The whole will henceforth be called engine.

Advantageously, at least one roller G_i has its angle in the center (G_i_1) determined so as to obtain the closed volumes that it delimits, as large as possible, taking into account the other parameters of the system, constraints such as contra intes of real and design (manufacturing constraints, material resistance, sealing problems, etc.). Advantageously, at least one roller G_i has its angle in the center (G_i_1) less than 180 °.

In fact, if we consider the maximum closed volume as a function of the angle at re (G_i_ 1), although the neck is devoid of d efferen geometric characteristics of the system, there is a maximum for an angle less than 180 ° , often much lower, around 130 °.

The envelope V has tips, or ends Qa, Qb or even Qc, according to the values of m. If we take, for example Qa, this end delimits, at a time of the cycle, a variable volume on each of its faces, on one side with G_i-1 and on the other, with G_i. Advantageously, the angle at the center (G_i_1) of at least one roller Gj is determined so as to close the previous volume to start the compression in this volume, at the same time that it opens the next closed volume to allow the evacuation of burnt gas.

The ends Q of the envelope V, according to the basic geometric design, have an angular shape. They can be widened for reasons of resistance of the materials subjected to strong constraints, sealing, manufacturing, ... etc. It has not been specified so far, which of the form of revolution F and the envelope V is inside the other.

Advantageously, in a first implementation, the form of revolution F is outside with respect to the envelope V (and consequently, the envelope V, is inside with respect to the form of revolution F).

We can say that in this case, we have a rotary piston inside the set, of which V is the outer surface. Outside the assembly, we have a frame that can be fixed whose inner surface is the F shape and the cells. This frame carries the axes β_ί, and on its inner surface are extruded the cells A_i.

Advantageously, in a second implementation, the revolution form F is inside with respect to the envelope V (and consequently, the envelope V, is outside with respect to the revolution form F).

We can say that in the latter case, we have a rotary piston inside the set of which F and the cells form the outer surface. This piston carries axes β_ί. On the outside of the set, we have a frame that can be fixed whose inner surface is the envelope V.

Advantageously, at least 2 cells A_i and A_i + 1 are contiguous, that is to say that they are as close as possible. They remain separate, but the separations between them have a thickness reduced to a minimum, taking into account the constraints of resistance of the materials, sealing, and design: as will be explained further, close together means nevertheless a small distance between 2 cells consecutive, to be able to arrange a fluid passage from one side to the other side of the envelope V. Moreover, if the ends of the envelope V are not spikes, but widened, this also helps to widen the separation .

If the number of cells is odd, the explosions occur one at a time, and the operation is more regular. For this type of rotary engine, it is essential to be able to pass, in one way or another, the compressed fluid on one side of one end Q of the envelope V, to the closed volume of the other side of this end Q. The fluid remains compressed because it is trapped between two rollers in their respective respective cells, the form F and the envelope V. In a heat engine, the explosion takes place at this time, and thus, the pressure on that other side of Q makes the envelope turn in the right direction.

Advantageously, between at least two consecutive cells A_i and A_i + 1, a passage is arranged so that, when a Q end of the envelope V is between these 2 cells, the fluid compressed by one of the faces of the Q end of the envelope V, can pass on the other side (on which the fluid, after explosion, will relax).

With the passage can be arranged a pre-combustion chamber.

Advantageously, the axes β_ί are parallel to delta and located at the same delta distance d = distance (OP).

Advantageously, the forms F, A_i, G_i, and V, are cylindrical generatrices parallel to delta.

In this case, the rollers G_i have their section along a plane passing through beta_i which is a rectangle, and the section of V along a plane passing through delta is a rectangle too. It may be interesting to be able to round the angles of the rectangles.

Advantageously, the rollers are such that the section of G_i along a plane passing through beta_i is a non-rectangular surface. The envelope V is drawn accordingly. The new design of the rollers and V also allows to integrate the joints

(or segments) sealing.

The engine (or pump) can still operate with various valves or valves, but it may be best to avoid them when you can, and have intake and / or exhaust openings open permanently.

For this, advantageously, admission of the fresh gases passes through the inside of the central rotary piston. For the same reasons, advantageously, the escape of the burnt gases passes through the inside of the central rotary piston.

The following figures and descriptions of some particular implementations will provide a better understanding. Figures 1 to 23ter relate to embodiments according to the

1st implementation, that is to say, the form F is outside, the envelope V inside. The form F is fixed, and the envelope V rotates. The envelope V is the central rotary piston.

Figures 1 to 5 show different stages of the design of a first embodiment of an engine according to the invention for obtaining the geometric shapes of said engine.

Figures 6 to 1 1 illustrate the various stages of an operating cycle of an engine according to the invention.

Figures 12 to 16 show motors for rollers having different center angle values.

FIG. 17 shows the value of the limit angle ω1 and the length OQ as a function of the value of the half angle at the center of the rollers (μ).

Figures 18 and 18a show a motor without valve.

Figures 19 to 22 show some examples with different coefficients m and different values of the number of cells. Figures 23 and 23a show an example of drive with gears. Figure 23b shows non-rectangular sections of G_i.

Figures 24 to 31 bis show a second embodiment of an engine according to the invention.

In these examples, the axes β_ί are parallel to delta and located at the same distance d of delta.

The shape F and its cells A_i, the rollers G_i, the envelope V are cylindrical generatrices parallel to delta. The side walls J1 and J2 are perpendicular to delta.

Under these conditions, it is preferable, for the sake of understanding, to represent the system by a section BB by a plane perpendicular to the delta axis (FIG. 23).

To avoid overloading the scriptures in the drawings, on ¹ G_1 roller, the P_1 point the cell A_1, they will be graded G, P, A, and for other G_1 elements. For other rollers, the elements G_i, P_i, A_i, ... etc. will be noted Gi, Pi, Ai on the figures.

Figure 1: the system is in the initial position Pos_0, in which a horizontal axis Ox, is an axis of symmetry of the set. The piston F is positioned in such a way that the cell A_1 is on this axis Ox, the first face G_1_1 is in its cell.

In this figure, we distinguish:

O, the intersection of the cutting plane with the delta axis,

- P, and P2 the intersection of the cutting plane with the axes beta_1 and beta_2. They are the centers of the cells A and A2, and the centers of rotation of the rollers

G and G2. - The form F,

- The envelope V, its end Qa towards the cell A1 (in the position Pos_0), and the other end Qb.

In this position Pos_0, V and G are in contact in Q.

This point Q in the fixed reference Ox, Ow, is Q0 (the 0 for Pos_0).

Qa is a point of V, which we will call QaO, and a point of G, which we will call qaO.

- The rollers G, half-angle at the center μ whose ends are R and S, axis of symmetry Py, and the roller G2, whose ends are R2, and S2,

In the other figures:

- ω is the angle of rotation (Ox, Oy) of the piston V,

- Θ is the angle of rotation (Ox, Oz) of the roller G. Here, Θ = 2 ^* ω (m = 2).

The initial data are:

- n equal to 2

- m equal to 2

- Distance d, equal distance (OP)

- the radius r of the angle in the center (R, P, S)

the half-angle μ of the center angle (R, P, S) of the roller G,

From these data, we will draw the rest of the system. Figure 2 corresponds to the position Pos_1, where the points Q, S and U meet.

This figure makes it possible to determine ω1, and the radius R of the form F. Indeed, by observing the triangles, one finds that: d ^* sin (ω1) = r ^* sin (μ + (m-1) ^* ω1), and

R = d ^* cos (ω1) + r ^* cos (μ + (m-1) ^* ω1)

Figure 3: it is a question of determining the arc of curve G_1_2 of G.

For that, let's go back to Pos_0. qaO is a ^1st point of G_1_2. Let's grow ω from 0 to ω1. At each moment t and each value of ω (ί), Qa is the point of V in contact with G in qa (qa being a point of G). The half curve G_1_2 of G is the set of points qa.

The last point is S. The other half curve is obtained by symmetry.

Figure 4: This is to determine the 1 ^st part of the envelope V.

For that, let's start from Pos_1. Q is the ^1st point of the desired envelope arc. Let ω grow from ω1 until (P, S) is aligned with Ox. At each moment t and each value of ω (ί), S is the point of G in contact with V in s, s being a point of V.

The 1 ^st part of the envelope V is the set of points s.

Figure 5, the position is Pos_2: (P, S) is aligned with Ox and ω = ω2. Let's grow ω from ω2 up to 90 °. This portion of the envelope V is an arc of circle of center O, radius d - r.

The rest of the piston is obtained, in this case, by 2 symmetries.

We therefore saw that G_1_2 and the envelope V were obtained independently. Curve G_1_2 was "machined" by Qa ("machining" in the sense that Qa is a cutting tool which usinerait material to give shape to G_1 _2, Qa and G_1_2 being driven in their respective rotary movements as defined above), and the 1 ^st part of the envelope has been "machined V By S. These curves were obtained step by step to contribute to understanding. They can be obtained analytically as well.

This is a way of doing things. There are others, for example, suppose that it is necessary to consider that the ends Q of the piston must be wider, for example, for reasons of sealing, of manufacture, or because the considerable pressure at the time of the explosion, leads to widen the ends Q of the piston.

The "improved piston" is then drawn, then it is this piston that will "machine" the rollers. This "improved piston" may not be symmetrical; in this case, the curve arc G_l_2 is no longer symmetrical. For example, the shape of the Q-piston can be rounded at its ends

Qa and Qb, to be easier to machine (a round mill is less expensive than tools for machining more complex shapes). The principle remains the same is that Qa "will cut" the 1 ^st part of the G_1_2 arc.

Another example, if the ends of Q are no longer a point, but 2 points Qaa, and Qab (for Qa) separated by a small distance compatible with the resistance constraints of the material, and such that OQaa = OQab = d, to simplify , do not take into account the shape of the piston between these two points, which Qaa "will cut" the 1 ^st parties arc G_1 _2 (2 ^eme by Qab, which will be symmetrical). In a more general way, any modification with respect to the basic drawing is possible, provided that the rollers G and the envelope V remain in contact at all times, that is to say that one is the envelope each other in their respective movements. Figures 6 to 1 1 show the operation of an engine according to the invention with four rollers.

Figure 6: the volume v2 has just been closed by the roller G2. It contains fresh air to compress. In this example, the angle at the center μ = 90 ° - ω1, so that the roller G2 closes v2, at the same time as the roller G4 opens the volume v1.

Figure 7: ω = ω1, the volume of air v2 has been compressed and occupies volume v3.

Figure 8: the volume v3 is passed to v4, on the other side of Qa by a suitable passage (not shown). At this moment can take place the injection then the explosion. The flue gases exert a strong pressure on the central piston which makes it turn.

Figure 9: This is the end of the trigger, the volume v4 has increased to become the maximum volume v5.

Figure 10: A quarter of a turn is available to evacuate the flue gases and replace the exhaust air with air. Intake and exhaust valves are not shown.

Figure 1 1: the volume v7 contains fresh air, and the roller L1 closes the volume. We are in the situation of Figure 10.

The exhaust and intake can be done in different ways and depending on the configuration. For example, here the exhaust can be at f2 (Fig. 9). Admission can be done at e1 level; the bottom of the cell v8 can be filled with fresh air at low pressure in advance, so that it will drive more quickly the remaining burned gas to f2, from the opening at the level of S. It can be seen that, contrary to conventional cylin- der motors, the valves (or valves) are not in a fire zone (where the explosion takes place), which gives more freedom for their implementation. This operation is similar to that of the 2-stroke engine (compression, expansion, and exhaust / intake). An operation similar to that of a 4-stroke engine could be described, the complete cycle then taking place over 2 turns. Figures 12 to 16 show the influence of the center angle on the engine characteristics. These figures show, for different values of μ, the maximum volume v5 for the expanded gases. The length d and the radius r are the same in all these figures.

Figure 12: μ = 90 ° Figure 13: μ = 80: we see, compared to the previous case, that for a difference of only 10 °, the volume v5 is significantly larger, about twice as much.

Figure 14: μ = 66: we see, compared to the previous case, that the volume has almost doubled. Figure 15: μ = 90 ° - ω1 is about 60 ° here. For this value, the pebble

G_1 closes the previous volume v8, and opens the volume v5 at the same time. The volume v5 is little different from the previous case: it caps.

Figure 16: μ = 55 °: we see, compared to the previous case, the volume v5 has changed little. It can be seen that for μ <90 ° - ω1, the volume at the bottom of the cell is never enclosed.

It can be seen that the maximum volume v5 has increased when μ has decreased, up to a ceiling and that the value to be retained is in this neighborhood, taking into account different constraints. Figure 17 shows that ω1 also passes by a maximum, obtained for 65 ° approximately. We also see that the distance OQ increases when μ decreases. Although it is not formally demonstrated here, the maximum of ω1 and the maximum of v5 are in the same neighborhood of values. These results have been explained for a particular value of the ratio r / d, but one could show that they are general.

What is true for gas expansion is also true for compression because there is symmetry.

It is concluded that μ = 90 ° is not an ideal choice. For the motor to be more efficient, μ must preferably be less than 90 °.

Figures 18 and 18bis give an example of valveless operation, the fresh air passing through the interior of the central piston, and passing through the arcuate portion of the piston. The two intake valves fa and fb are shown. Only the exhaust valve f1 on G has been shown; there is one by pebble.

The shaded area upwards (from left to right) corresponds to fresh air to be compressed, the hatched area downwards corresponds to expanding flue gas, the grid area corresponds to flue gas, being replacement by fresh air. In the previous figures, the rotational speed ratio is m = 2.

This rotational speed ratio m may be different. Figures 19 to 22 show some examples with coefficients m ranging from 3 to 5.

Figure 19: m = 3 and 9 cells. Figure 20 m = 4 and 9 cells. Figure 21: m = 5 and 9 cells. Figure 22 m = 5 and 1 1 cells.

Figs. 23 and 23a show an exemplary drive with gears. The wheels G1 to G5 give the direction of rotation and the ratio m.

In FIG. 23a, the section AA, the sections of V and the rollers are here rectangles (hatched) because all the generatrices are parallel to delta. But the pebbles can be other, especially at the level of external angles. The envelope V is modified accordingly. Figure 23a shows chamfered rollers. They could also be rounded. More generally, any modification with respect to the basic drawing is possible, provided that the rollers G and the envelope V remain in contact at all times, that is to say that one is envelope of the other in their respective movements Figures 24 to 31 relate to embodiments according to the

2nd implementation, that is to say, the form F is inside, the envelope V outside. Here, the form F rotates, and the envelope V is fixed. Form F is the central rotary piston.

All that has been said for the 1 ^st implementation and remains valid for the ^2nd is not repeated here.

Figure 24 shows the motor in position Pos_0.

Figure 25 shows how to obtain ω1 and OQ.

Figures 26 to 29 show the operation.

Figure 30 corresponds to Figure 7 of the 1 ^st implementation, with close rollers. The volume v3 of compressed air passes on the other side of the envelope V in v4 by a passage not shown. Figures 31 and 31a show an example of drive with gears.

The rotary piston engine is an intermediate solution between the engine with cylinders and pistons, and the turbine engine. The possible applications are numerous (motors, pumps, compressors, ...).

Compared with cylinder and piston engines, the elimination of this linear reciprocating movement of the piston is very anti-mechanical, the simplicity, the absence of vibration, will allow reliable operations with little wear, and economic.

Compared to turbines (gas, steam, fluids under pressure, ... etc.), the yield will be much higher.

This engine is also conducive to the realization of gas engines, or hydrogen, non-polluting

Claims

Motor or pump, said rotary piston, comprising: a form of revolution F with respect to a delta axis, and rotatable about said delta axis relative to an envelope V, n alveoli A_i which are forms of revolution of axis β_ί , distributed around the circumference of F, in each cell A_i is housed a roller Gj which rotates about the axis β_ί, and has at least 2 faces, G_i_1 and G_i_2, the first of these faces G_i_1 being able to ensure the l sealing with the cell A_i at certain moments of the cycle of the system when this face is inside the cell A_i and whose section by a plane perpendicular to β_ί, is an arc centered on β_ί, d angle in the center (G_i_1) a mechanical means which makes the rotation of each Gj around β_ί proportional to the relative rotation of delta axis of the form F with respect to the envelope V,

the envelope V being the envelope generated by the rollers Gj in their rotational movement around the β_ί themselves driven by F, and the relative rotation of delta axis of the form F with respect to the envelope V,

- The face G_i_2 of Gj is the envelope generated by the envelope V at G_i and thus ensures the seal between G_i and the envelope V, the assembly is made so that, if we consider a section by a plane perpendicular to delta, the envelope V, the form F and one of the ends of the arc G_i_1 of Gj are in contact, in one place, at a particular moment of the cycle, the side walls or cheeks J1 and J2 on which the shape F, the pebbles Li, and the envelope V,

the shape F, the rollers Gj, the envelope V, the cheeks J 1 and J 2, delimiting closed and variable volumes at different moments of the cycle of the relative rotation of F with respect to V, the assembly being characterized in that that at least one roller G_i has its angle in the center (G_i_1) determined so as to obtain the closed volumes which it delimits, as large as possible,

2) Motor or pump according to the preceding claim, characterized in that at least one roller G_i has its center angle (G_i_1) less than 180, 3) Moteu r or pump, according to any one of the preceding claims, characterized in that the angle in the center (G_i_1) of at least one roller G_i is determined so as to close the preceding volume, while it opens the next closed volume,

4) Motor, or pump, according to any one of the preceding claims characterized in that the form of revolution F is outside with respect to the envelope V,

5) Motor, or pump, according to any preceding claim except the previous one, characterized in that the form of revolution F is inside with respect to the envelope V, 6) Motor, or pump, according to the any one of the preceding claims, characterized in that at least 2 cells A_i and A_i + 1 are contiguous, 7) Motor, or pump, according to any one of the preceding claims, characterized in that between at least two consecutive cells A_i and A_i + 1, a passage is arranged so that when one end of the envelope V is located between these 2 cells, the fluid compressed by one of the faces of the end of the envelope V, can pass on the other face,

8) Motor, or pump, according to any one of the preceding claims, characterized in that the axes β_ί are parallel to delta and located at the same delta distance.

9) Motor, or pump, according to any one of the preceding claims, characterized in that the forms F, A_i, G_i, and V, are cylindrical generatrices parallel to delta.

10) Motor, or pump, according to any one of the preceding claims, characterized in that the section of each roller G_i along a plane passing through β_ί is a non-rectangular surface.

1 1) Motor, or pump, according to any one of the preceding claims, characterized in that the admission of fresh gases passes through the inside of the central rotary piston.

12) Motor, or pump, according to any one of the preceding claims, characterized in that the exhaust of the burnt gases passes through the inside of the central rotary piston.