Local double-channel stamping rotary detonation engine

Abstract

The invention relates to a local double-channel stamping rotating detonation engine which comprises an engine body and a cylinder arranged in the engine body. The cylinder is used for constructing local double channels in the engine main body and shunting fluid entering the engine main body, one part of the fluid flows through a flow channel formed between the inner wall of the engine main body and the outer wall of the cylinder, and the other part of the fluid flows through a flow channel defined by the cylinder; the engine main body comprises an isolation section, a combustion chamber, an equal straight section and an expansion section which are connected in sequence; part of the cylinder is arranged in the isolation section, a gap is formed between the cylinder and the isolation section, the rest part of the cylinder extends into the combustion chamber, and the axial length of the part, extending into the combustion chamber, of the cylinder is smaller than that of the combustion chamber. Through the cylinder arranged inside, the local double-channel design is achieved, the compact structure of detonation waves can be achieved, and the size of an engine is reduced, and the thrust-weight ratio is increased.

Description

Technical Field

[0001] The invention relates to the field of aerospace, and in particular to a local dual-channel ramjet rotating detonation engine. Background Art

[0002] Ramjet is one of the ideal power devices for air-breathing aircraft. In recent years, the research on supersonic detonation combustion in ramjet has gradually increased. First, detonation combustion has higher thermodynamic efficiency, and the reaction front moves at supersonic speed, providing higher energy release power; second, the shock wave generated by detonation combustion will cause instability in the upstream injection mixing, which is conducive to the atomization of liquid fuel injection / the mixing of gas fuel jet and turbulent molecules of air, and the lateral expansion of the detonation wave may also strengthen the downstream secondary combustion; third, detonation combustion only produces local high back pressure in space or time.

[0003] At present, there are still some outstanding problems in the development of ramjet rotating detonation engines: First, whether detonation combustion can improve the performance of the engine and the reliability of detonation combustion needs further study; second, the design of ramjet engines using detonation combustion mode is still relatively lacking and is still in the preliminary stage; third, there is a lack of robust solutions for the stable working state of detonation combustion.

[0004] One of the key technologies of ramjet rotating detonation engines is the controlled combustion of rotating detonation waves in the combustion chamber, which enables it to operate stably within the design range of operating conditions and has high robustness. It is generally believed that detonation waves shorten the induction time of chemical reactions by compressing the fuel / air mixture through shock waves, making the process similar to isochoric combustion, and the explosion reacts on the reaction front to continue to maintain the supersonic motion of the reaction front. Although these characteristics make detonation combustion have the outstanding ability to release energy quickly and achieve high mass flow consumption in a compact space, they also give the detonation wave structure an unstable characteristic, making it more demanding on the explosive mixture and its working environment.

[0005] At present, the rotating detonation combustion scheme can be roughly divided into three categories: annular combustion chamber, empty barrel combustion chamber and disc combustion chamber. Among them, the annular scheme is the most widely studied, and both the empty barrel configuration are suitable for organizing ramjet mode combustion. From the 1950s to today, the research has gradually clarified the influence of configuration geometry parameters, fuel type, outlet profile, equivalence ratio, flow rate, injection scheme and other factors on the propagation characteristics of rotating detonation waves, and pointed out that the strong coupling relationship between the various factors seriously hinders the stable self-sustaining of rotating detonation waves. For example, the detonation wave structure of the explosive mixture will be essentially different due to the different types of fuel and oxidizer, and will show a strong geometric dependence. For example, hydrogen can achieve stable rotational detonation in a narrow channel, while ethylene and liquid kerosene require a wider channel to better maintain the detonation wave. The local high temperature and high pressure state generated by the detonation wave will not only block the flow of the upstream premixed gas, but also form an upward spiral shock wave due to the circumferential motion of the rotating detonation wave, so that the detonation wave structure is closely related to the upstream injection mixing process. Similarly, under different equivalence ratios, flow rates and injection schemes, the propagation characteristics of the detonation wave show significantly different propagation characteristics. These factors are mixed together to determine the reliability of detonation combustion.

[0006] The research on ramjet rotating detonation mainly verifies the feasibility of the ramjet mode of annular isolation section annular combustion chamber or annular isolation section empty barrel combustion chamber. The annular isolation section structure has high requirements for the uniformity of the incoming flow and the integrated design of the intake duct. The use of a cylindrical isolation section may reduce the sensitivity of the detonation combustion process to these problems. From the currently publicly reported literature, there are few studies on ramjet rotating detonation with a cylindrical isolation section, and there is a lack of corresponding mature solutions. Summary of the invention

[0007] The object of the present invention is to provide a local dual-channel ramjet rotating detonation engine.

[0008] To achieve the above-mentioned object of the invention, the present invention provides a local dual-channel ramjet rotating detonation engine, comprising: an engine body and a cylinder arranged in the engine body;

[0009] The cylinder is used to construct a local double channel in the engine body to split the fluid entering the engine body, wherein a part of the fluid flows through the flow channel formed between the inner wall of the engine body and the outer wall of the cylinder, and another part of the fluid flows through the flow channel surrounded by the cylinder;

[0010] The engine body comprises: an isolation section, a combustion chamber, an equal straight section and an expansion section connected in sequence;

[0011] Part of the cylinder is disposed in the isolation section with a gap therebetween, the rest of the cylinder extends into the combustion chamber, and an axial length of the part of the cylinder extending into the combustion chamber is smaller than the axial length of the combustion chamber.

[0012] According to one aspect of the present invention, the axial length of the portion of the cylinder located in the isolation section is greater than the axial length of the portion of the cylinder located in the combustion chamber.

[0013] According to one aspect of the present invention, the wall thickness of the cylinder is gradually increased along the direction from the isolation section to the combustion chamber.

[0014] According to one aspect of the present invention, the inner diameter of the cylinder is constant.

[0015] According to one aspect of the present invention, along the direction from the isolation section to the combustion chamber, the wall thickness of the cylinder increases linearly, and the inclination angle of the thickness increase is between 0° and 1.5°.

[0016] According to one aspect of the present invention, along the direction from the isolation section to the combustion chamber, the combustion chamber comprises: a combustion chamber inlet section and an expansion cavity section;

[0017] The combustion chamber inlet section and the expansion cavity section are coaxially arranged;

[0018] Along the direction from the isolation section to the combustion chamber, the end of the cylinder extends into the expansion cavity section.

[0019] According to one aspect of the present invention, the engine body is a hollow cylindrical structure.

[0020] According to one aspect of the present invention, the axial length of the cylinder is 1 / 4 to 1 of the axial length of the isolation segment;

[0021] The cylinder comprises: a first cylinder part and a second cylinder part which are coaxially arranged, wherein the first cylinder part is located in the isolation section, and the second cylinder part is located in the combustion chamber;

[0022] The axial length of the first cylindrical portion is 9 / 10 to 10 / 11 of the length of the cylinder.

[0023] According to one aspect of the present invention, the length of the second cylindrical portion extending into the expansion cavity section is 1 / 11 to 1 / 10 of the length of the second cylindrical portion.

[0024] According to one aspect of the present invention, a first fuel nozzle is provided on the isolation segment, and a plurality of the first fuel nozzles are provided at intervals along the circumference of the isolation segment;

[0025] A second fuel nozzle is arranged on the cylinder, and a plurality of the second fuel nozzles are arranged at intervals along the circumference of the cylinder;

[0026] The first fuel nozzle is disposed opposite to the cylinder;

[0027] The second fuel nozzles are arranged in multiple rows along the axial direction of the cylinder, and at least some of the second fuel nozzles are arranged opposite to the isolation section;

[0028] The axial length of the straight section is 0 to 1 / 3 of the axial length of the combustion chamber.

[0029] According to one embodiment of the present invention, the present invention has a compact structure, wherein a local dual-channel design is achieved by an internally arranged cylinder, thereby facilitating a compact structure of the detonation wave, which has a positive effect on reducing the size of the engine and improving the thrust-to-weight ratio.

[0030] According to one scheme of the present invention, the present invention realizes stable rotating detonation combustion in the engine through a cylinder to form an upward rotating shock wave, and relies on huge transient shear force to break up the injection mixing, thereby improving the mixing efficiency and the combustion environment. The local dual-channel design is expected to further improve the combustion efficiency and achieve higher thermal energy conversion.

[0031] According to one solution of the present invention, the present invention optimizes the guiding effect on the airflow and realizes a local diversion design, thereby helping to improve the stability of the detonation wave under different working conditions and enhance the robustness of the engine.

[0032] According to one scheme of the present invention, the local dual-channel design of the present invention provides more adjustment means for optimizing the distribution of the incoming flow and the combustion process. On the one hand, the incoming flow is diverted to control the injection mixing process and further control the combustion mode. On the other hand, complex shock waves and shear layer features are constructed at the head of the combustion chamber based on the cylindrical structure, which makes it easy to form hot spots and contributes to the stable formation of the combustion mode, thereby adapting to different flight conditions and performance requirements.

[0033] According to one solution of the present invention, the design concept of the partial dual-channel empty barrel type rotating detonation combustion chamber of the present invention not only provides a feasible solution to the existing technical challenges, but also provides new ideas and advantages for the design of the power system of the aircraft. With further research and technological development, this combustion chamber is expected to play an important role in the aerospace field.

[0034] According to one solution of the present invention, the design of the local dual-channel empty barrel type rotating detonation combustion chamber of the present invention is intended to enhance the stability and compactness of the detonation wave through the local dual-channel configuration. This design can restrain the detonation wave head to a certain extent, and enhance the mixing efficiency of the combustible premixed gas through local diversion, thereby creating a more favorable explosion environment. In addition, the local optimization design helps to enhance the guiding effect of the rotating detonation wave in the cylindrical isolation section ramjet engine and improve the robustness during the working process. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematically shows the structure of a local dual-channel ramjet rotating detonation engine according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0037] When describing the embodiments of the present invention, the orientation or positional relationship expressed by the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or positional relationship shown in the relevant drawings and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0038] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments cannot be described one by one here, but the embodiments of the present invention are not therefore limited to the following embodiments.

[0039] like Figure 1As shown, according to one embodiment of the present invention, a local dual-channel ramjet rotary detonation engine of the present invention comprises: an engine body 1 and a cylinder 2 disposed in the engine body 1; wherein the cylinder 2 is used to construct a local dual-channel in the engine body 1 to divert the fluid entering the engine body 1, wherein a part of the fluid flows through the flow channel formed between the inner wall of the engine body 1 and the outer wall of the cylinder 2, and another part of the fluid flows through the flow channel surrounded by the cylinder 2. In this embodiment, the engine body 1 comprises: an isolation section 11, a combustion chamber 12, an equal straight section 13 and an expansion section 14 connected in sequence; wherein a part of the cylinder 2 is disposed in the isolation section 11, and there is a gap between the isolation section 11, and the rest of the cylinder 2 extends into the combustion chamber 12, and the axial length of the part of the cylinder 2 extending into the combustion chamber 12 is less than the axial length of the combustion chamber 12.

[0040] Through the above-mentioned arrangement, the present invention effectively realizes the distribution of the incoming flow into the combustion chamber 12 by arranging the cylinder 2 in the engine body 1, so as to realize the fuel injection for part of the incoming flow, realize the separation of the injection mixing process in the incoming flow, thereby further improving the combustion mode. In addition, by partially extending the cylinder 2 into the combustion chamber 12, the incoming flow in the middle part is stably input into the combustion chamber 12 under the restriction inside the cylinder 2, and the incoming flow of the mixed fuel between the cylinder 2 and the engine body 1 can generate complex shock waves and shear layer characteristics based on the change of the cross section in the conveying direction, so that hot spots are easy to form, which is conducive to the stable formation of the combustion mode, and further mixes with the incoming flow passing through the cylinder 2 in the combustion chamber and more stably maintains the shear layer combustion / explosion combustion at the mixing position, so that the entire combustion process is stable and reliable.

[0041] In the present embodiment, the engine body 1 is a hollow cylindrical structure, thereby forming a circular hollow passage between the cylinder 2 and the engine body 1 .

[0042] Through the above arrangement, the engine body 1 is set as a cylindrical structure, so that the cross-sectional variation of the annular channel formed by the cylinder 2 in the circumferential direction can be kept consistent, so that the entire combustion process can be more easily controlled and maintained.

[0043] like Figure 1 As shown, according to one embodiment of the present invention, the axial length of the portion of the cylinder 2 located in the isolation section 11 is greater than the axial length of the portion of the cylinder 2 located in the combustion chamber 12 .

[0044] Through the above-mentioned arrangement, by arranging most of the cylinder 2 in the isolation section 11, the axial length of the double channels formed by the cylinder 2 and the isolation section 11 can be made larger, thereby making it easier to achieve stable distribution and transportation of the incoming flow, so that the divided incoming flow can flow over a long distance in its respective channel to achieve stability and smoothness, thereby effectively eliminating the disturbance caused by the dividing position.

[0045] like Figure 1 As shown, according to one embodiment of the present invention, the wall thickness of the cylinder 2 is gradually increased along the direction from the isolation section 11 to the combustion chamber 12.

[0046] Through the above-mentioned arrangement, the wall thickness of the cylinder 2 is set to be gradually thickened, so that the cross-section of the annular hollow channel between the cylinder 2 and the engine body 1 presents a variable cross-section. In particular, when the internal radial dimension of the isolation section 11 is constant, the annular hollow channel can be made to present a form of a smaller cross-section, thereby slowing down the incoming flow that needs to flow through the annular hollow channel and improving the mixing effect of the incoming flow and the fuel. At the same time, most of the incoming flow entering the isolation section is not slowed down, thereby reducing the overall total pressure loss.

[0047] In this embodiment, the wall thickness of the cylinder 2 increases linearly along the direction from the isolation section 11 to the combustion chamber 12, and the inclination angle of the thickness increase is between 0° and 1.5°.

[0048] Through the above configuration, the wall thickness of the cylinder 2 is set to increase linearly, so that the cross section of the annular flow channel between the cylinder 2 and the engine body 1 can be in the form of a linear variable cross section, which is more beneficial to maintaining the smooth and stable flow of the fluid. In addition, setting the inclination angle of the wall thickness change of the cylinder 2 between 0° and 1.5° can fully realize the subsonic flow in the annular flow channel, providing a strong guarantee for jet mixing.

[0049] like Figure 1 As shown, according to one embodiment of the present invention, the inner diameter of the cylinder 2 is constant.

[0050] Through the above arrangement, by setting the interior of the cylinder 2 to a constant cross-section, the incoming flow can be kept stable, ensuring that the incoming flow entering the rear combustion chamber 12 still maintains supersonic flow, and forms Kelvin-Helmholtz instability with the combustible mixture in the subsonic annular flow channel at the end of the cylinder 2, inducing the generation of vortices, and further enhancing the mixing effect and improving the combustion quality.

[0051] like Figure 1As shown, according to an embodiment of the present invention, along the direction from the isolation section 11 to the combustion chamber 12, the combustion chamber 12 includes: a combustion chamber inlet section 121 and an expansion concave section 122; wherein the combustion chamber inlet section 121 and the expansion concave section 122 are coaxially arranged. In this embodiment, along the direction from the isolation section 11 to the combustion chamber 12, the end of the cylinder 2 extends into the expansion concave section 122.

[0052] Through the above-mentioned arrangement, the end of the cylinder 2 is extended into the expansion cavity section 122, which effectively ensures that the incoming flow between the cylinder 2 and the combustion chamber inlet section 121 can be effectively restricted and still maintains the direction of flowing toward the wall of the expansion cavity section 122. Further combined with the sudden change in the radial size of the expansion cavity section 122, it is easier to induce complex shock waves and shear layer characteristics, thereby making it easier to produce shear layer combustion / detonation combustion between the incoming flow passing through the cylinder 2.

[0053] like Figure 1 As shown, according to one embodiment of the present invention, the axial length of the cylinder 2 is 1 / 4 to 1 of the axial length of the isolation section 11; wherein the cylinder 2 comprises: a first cylinder portion and a second cylinder portion coaxially arranged, wherein the first cylinder portion is in the isolation section 11, and the second cylinder portion is in the combustion chamber 12. In this embodiment, the axial length of the first cylinder portion is 9 / 10 to 10 / 11 of the cylinder 2.

[0054] Through the above arrangement, the axial length of the cylinder 2 is set within the range of 1 / 4 to 1 of the axial length of the isolation section 11. On the one hand, it is easier to flexibly arrange the length of the cylinder 2. On the other hand, the cylinder 2 can have a sufficient length to maintain the axial length of the dual channels to optimize the segmentation and stable delivery of the incoming flow.

[0055] Through the above-mentioned arrangement, the 9 / 10 to 10 / 11 parts of the cylinder 2 are arranged in the isolation section 11 so that the cylinder 2 has a sufficient length so that the thickness extends toward the wall of the engine body 1, thereby achieving the restraint of the detonation combustion wave head, making the detonation wave propagation more robust, and at the same time reducing the disturbance of the detonation combustion to the central flow at the entrance of the combustion chamber.

[0056] like Figure 1 As shown, according to one embodiment of the present invention, the length of the second cylindrical portion extending into the expansion cavity section 122 is 1 / 11 to 1 / 10 of the second cylindrical portion.

[0057] Through the above arrangement, the manner in which 1 / 11 to 1 / 10 of the second barrel portion of the cylinder 2 extends into the expansion cavity section 122 can conveniently and stably guide the mixture of the incoming flow and the fuel into the expansion cavity section 122, so as to fully realize the complex shock wave. At the same time, it can also effectively avoid the excessively long structure causing the shear combustion or deflagration combustion position of the dual-channel incoming flow when they converge, which is more beneficial to ensuring the working performance of the present invention.

[0058] like Figure 1 As shown, according to one embodiment of the present invention, a first fuel nozzle 11a is provided on the isolation segment 11, and a plurality of first fuel nozzles 11a are provided at intervals along the circumference of the isolation segment 11; wherein the first fuel nozzle 11a is provided opposite to the cylinder 2.

[0059] Furthermore, a second fuel nozzle 2a is arranged on the cylinder 2, and a plurality of second fuel nozzles 2a are arranged at intervals along the circumference of the cylinder 2; in addition, a plurality of rows of second fuel nozzles 2a are arranged along the axial direction of the cylinder 2, and at least some of the second fuel nozzles 2a are arranged opposite to the isolation section 11; wherein, along the axial direction of the cylinder 2, the distance between the second fuel nozzle 2a and the end of the cylinder 2 extending into the combustion chamber 12 is smaller than the distance between the second fuel nozzle 2a and the end of the cylinder 2 in the isolation section 11, thereby making the second fuel nozzle 2a closer to the downstream of the cylinder 2, so that the combustion will not be too close to the upstream, thereby improving the ability of the isolation section 11 to withstand the high back pressure of the combustion.

[0060] In addition, in the present application, if part of the second fuel nozzles 2a are arranged opposite to the isolation section 11, the remaining second fuel nozzles 2a can also be arranged toward the inside of the cylinder 2 to achieve the injection of fuel on both sides of the cylinder 2, so as to flexibly set the combustion process.

[0061] like Figure 1 As shown, according to one embodiment of the present invention, the axial length of the straight section 13 is 0 to 1 / 3 of the axial length of the combustion chamber 12 .

[0062] Through the above arrangement, the axial length of the straight section 13 is set to 0 to 1 / 3 of the axial length of the combustion chamber 12, which increases the combustion chamber pressure to a certain extent, reduces the axial velocity, and improves the self-sustaining robustness of the detonation wave.

[0063] Through the above-mentioned settings, by adopting a local dual-channel configuration to constrain the detonation wave head to a certain extent, it is expected to make the detonation wave structure more compact, and at the same time enhance the mixing efficiency of the combustible mixture through local shunt deceleration, and control the strong interference of high back pressure on the injection mixing process within a certain area, thereby strengthening the geometric flow state of the combustible premixed gas and creating a good explosion environment.

[0064] Through the above arrangement, the present invention enhances the guiding effect of the rotating detonation wave in the cylindrical isolation section ramjet engine through local optimization design, thereby improving the robustness during the working process.

[0065] The above contents are merely examples of specific solutions of the present invention. For devices and structures not described in detail therein, it should be understood that they can be implemented by adopting general devices and general methods available in the art.

[0066] The above is only one solution of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A local dual-channel ramjet rotating detonation engine, characterized in that: include: An engine body (1) and a cylinder (2) disposed in the engine body (1); The cylinder (2) is used to construct a local double channel in the engine body (1) to split the fluid entering the engine body (1), wherein a part of the fluid flows through the flow channel formed between the inner wall of the engine body (1) and the outer wall of the cylinder (2), and another part of the fluid flows through the flow channel surrounded by the cylinder (2); The engine body (1) comprises: an isolation section (11), a combustion chamber (12), a straight section (13) and an expansion section (14) which are connected in sequence; Part of the cylinder (2) is arranged in the isolation section (11) and is spaced apart from the isolation section (11); the rest of the cylinder (2) extends into the combustion chamber (12); and the axial length of the part of the cylinder (2) extending into the combustion chamber (12) is smaller than the axial length of the combustion chamber (12).

2. The local dual-channel ramjet rotating detonation engine according to claim 1, characterized in that: The axial length of the portion of the cylinder (2) located in the isolation section (11) is greater than the axial length of the portion of the cylinder (2) located in the combustion chamber (12).

3. The local dual-channel ramjet rotating detonation engine according to claim 2, characterized in that: Along the direction from the isolation section to the combustion chamber, the wall thickness of the cylinder (2) is arranged to gradually increase.

4. The local dual-channel ramjet rotating detonation engine according to claim 3, characterized in that: The inner diameter of the cylinder (2) is constant.

5. The local dual-channel ramjet rotating detonation engine according to claim 4, characterized in that: Along the direction from the isolation section (11) to the combustion chamber (12), the wall thickness of the cylinder (2) increases linearly, and the inclination angle of the thickness increase is between 0° and 1.5°.

6. The local dual-channel ramjet rotating detonation engine according to claim 5, characterized in that: Along the direction from the isolation section (11) to the combustion chamber (12), the combustion chamber (12) comprises: a combustion chamber inlet section (121) and an expansion cavity section (122); The combustion chamber inlet section (121) and the expansion cavity section (122) are coaxially arranged; Along the direction from the isolation section (11) to the combustion chamber (12), the end of the cylinder (2) extends into the expansion cavity section (122).

7. The local dual-channel ramjet rotating detonation engine according to claim 6, characterized in that: The engine body (1) is a hollow cylindrical structure.

8. The local dual-channel ramjet rotating detonation engine according to claim 7, characterized in that: The axial length of the cylinder (2) is 1 / 4 to 1 / 2 of the axial length of the isolation section (11); The cylinder (2) comprises: a first cylinder part and a second cylinder part which are coaxially arranged, wherein the first cylinder part is located in the isolation section (11) and the second cylinder part is located in the combustion chamber (12); The axial length of the first cylindrical portion is 9 / 10 to 10 / 11 of the length of the cylinder (2).

9. The local dual-channel ramjet rotating detonation engine according to claim 8, characterized in that: The length of the second cylindrical portion extending into the expansion cavity section (122) is 1 / 11 to 1 / 10 of the length of the second cylindrical portion.

10. The local dual-channel ramjet rotating detonation engine according to claim 9, characterized in that: A first fuel nozzle (11a) is arranged on the isolation section (11), and a plurality of the first fuel nozzles (11a) are arranged at intervals along the circumference of the isolation section (11); A second fuel nozzle (2a) is arranged on the cylinder (2), and a plurality of the second fuel nozzles (2a) are arranged at intervals along the circumference of the cylinder (2); The first fuel nozzle (11a) is arranged opposite to the cylinder (2); The second fuel nozzles (2a) are arranged in a plurality of rows along the axial direction of the cylinder (2), and at least part of the second fuel nozzles (2a) are arranged opposite to the isolation section (11); The axial length of the straight section (13) is 0 to 1 / 3 of the axial length of the combustion chamber (12).

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