A support plate type fuel mixing device for oblique detonation engine

Abstract

The present invention discloses a support plate fuel mixing device for an oblique detonation engine, comprising a mixing section and a central injection support plate. The mixing section is divided into a connected front mixing section and a rear mixing section, so that the length of the entire mixing section is adjustable to adjust the uniformity of the fuel perpendicular to the airflow direction and the fuel mass fraction in the boundary layer. The central injection support plate is arranged in the front mixing section to inject fuel into the mixing section perpendicular to the airflow direction. The front end of the central injection support plate is provided with a guide wedge surface to suppress the intensity of shock waves in the mixing flow channel. The rear end of the central injection support plate is provided with a guide wedge surface to generate a recirculation zone, into which the fuel is drawn for mixing. The present invention can achieve uniform fuel mixing and prevent premature combustion of the fuel in the mixing section.

Description

Technical Field

[0001] The invention belongs to the technical field of scramjet engines, and in particular to a support plate type fuel mixing test device for an oblique detonation engine. Background Art

[0002] Scramjet engines are currently an important and feasible means of achieving hypersonic propulsion. In the combustion chamber of a scramjet engine, the fuel burns at supersonic speeds. Due to the limited size of the combustion chamber, the fuel's residence time in the combustion chamber is very short, and supersonic combustion is mostly a diffusion flame. The effect of fuel mixing directly affects the combustion performance of the combustion chamber, and thus affects the thrust performance of the entire scramjet engine. Therefore, fuel injection and mixing technology is one of the key technologies of scramjet engines.

[0003] Since the successful initiation and stable stationing of oblique detonation waves have very stringent requirements on the incoming flow conditions, there is currently little research on the fuel injection and mixing of oblique detonation engines, and there are still many key technologies to be solved, such as: 1) The problem of fuel mixing in hypersonic incoming air: the fuel mixing effect directly affects the initiation, stability and combustion efficiency of the oblique detonation wave; 2) The problem of suppressing premature combustion: since the mixing of fuel and air needs to be completed in advance before the formation of the oblique detonation wave, if premature combustion occurs during the mixing process, it will directly affect the energy utilization efficiency and the detonation wave initiation characteristics; 4) The problem of stationing of oblique detonation waves in the combustion chamber: in order to achieve the stationing of the detonation wave in the combustion chamber, a higher mixed gas incoming flow velocity (greater than 2km / s) is required to avoid the situation where the detonation wave is forward transmitted and causes engine failure.

[0004] In scramjet engines, especially oblique detonation engines, in order to meet the requirements of flow field uniformity in the combustion chamber, it is appropriate to use a support plate to inject fuel from the center of the flow field into the mainstream. Therefore, in order to study the influence of the fuel mixing effect of the oblique detonation engine on the initiation and stationary characteristics of the oblique detonation wave, it is particularly important to design a multifunctional modular center support plate mixing test device in combination with a supersonic shock wave wind tunnel. Summary of the Invention

[0005] The object of the present invention is to provide a support plate type fuel mixing test device for an oblique detonation engine, so as to achieve uniform fuel mixing and avoid premature combustion of the fuel in the mixing section.

[0006] The technical solutions for achieving the purpose of the present invention are:

[0007] A support plate fuel mixing device for an oblique detonation engine includes a mixing section and a central injection support plate. The mixing section is divided into a front mixing section and a rear mixing section that are connected to each other. The length of the entire mixing section is adjustable to adjust the uniformity of the fuel in the direction perpendicular to the airflow direction and the fuel mass fraction in the boundary layer.

[0008] A circular observation window is installed on the wall of the mixing section to use a high-speed camera to capture the flow conditions in the mixing section and determine whether premature combustion occurs.

[0009] The central injection support plate is arranged in the front mixing section to inject fuel into the mixing section perpendicular to the flow direction of the airflow; the front end of the central injection support plate is provided with a guide wedge surface to suppress the shock wave intensity in the mixing flow channel, and the rear end of the central injection support plate is provided with a guide wedge surface to generate a recirculation zone, and the fuel is drawn into the recirculation zone for mixing.

[0010] Compared with the prior art, the present invention has the following significant advantages:

[0011] (1) The present invention successfully achieves rapid fuel mixing in an oblique detonation engine under high Mach number inflow conditions. The support plate adopts a reasonable flow wedge angle design to avoid premature combustion under high total enthalpy inflow conditions, laying the foundation for the combustion organization of the oblique detonation engine combustion chamber.

[0012] (2) In an oblique detonation engine, changing the length of the mixing section can change the mixing effect, that is, the uniformity of the fuel perpendicular to the direction of the airflow, and the mass fraction of the fuel in the boundary layer. The mixing effect of the fuel can determine whether the oblique detonation wave can be detonated, and also has a great influence on the stability of the oblique detonation wave. The present invention adopts a design of a combination of front and rear mixing sections to explore the influence of the mixing distance on the detonation and stable operation of the oblique detonation engine.

[0013] (3) The present invention is a support plate type fuel mixing device for an oblique detonation engine, which is suitable for a super enthalpy shock wave wind tunnel. The super enthalpy shock wave wind tunnel can simulate a stable air flow for a long time. Using the support plate type fuel mixing test device designed by the present invention, the fuel mixing effect under real flow conditions can be experimented and observed.

[0014] (4) In the experimental research on the detonation and stationary characteristics of the oblique detonation engine, the wave system structures formed by the combustion of gaseous and liquid fuels in the combustion chamber are quite different, so it is also necessary to study the mixing effect of different types of fuels. The injection support plate designed in the present invention is a replaceable structure, which can achieve the purpose of injecting different types of fuels without changing the mixing method and the engine geometric configuration. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1This is a cross-sectional view of an assembly of a support plate type fuel mixing test device for an oblique detonation engine according to the present invention;

[0016] Figure 2 It is an isometric drawing of the assembly of the present invention;

[0017] Figure 3 (a) is a cross-sectional view of the front end flange of the present invention;

[0018] Figure 3 (b) is a front view of the front flange of the present invention;

[0019] Figure 4 (a) is a cross-sectional view of the left side wall of the mixing section of the present invention;

[0020] Figure 4 (b) is a front view of the left side wall of the mixing section of the present invention;

[0021] Figure 5 (a) is a structural diagram of the right wall of the mixing section of the present invention;

[0022] Figure 5 (b) is a cross-sectional view of the right wall of the mixing section of the present invention;

[0023] Figure 6 This is a top view of the upper wall of the mixing section of the present invention;

[0024] Figure 7 This is an isometric view of the central injection support plate of the present invention;

[0025] Figure 8 (a) is a cross-sectional view of the gas fuel central injection support plate of the present invention;

[0026] Figure 8 (b) is a cross-sectional view of the liquid fuel center injection support plate of the present invention

[0027] Figure 9 This is a cross-sectional view of the central injection support plate of the present invention;

[0028] Figure 10 This is a schematic diagram of the installation of the central injection support plate of the present invention;

[0029] Figure 11 This is a cross-sectional view of the observation window cover of the present invention;

[0030] Figure 12 This is a cross-sectional view of the observation window glass assembly of the present invention;

[0031] Figure 13 (a) is a cross-sectional view of the flange after the mixing front section of the present invention;

[0032] Figure 13 (b) is a front view of the flange behind the mixing front section of the present invention;

[0033] Figure 14 (a) is a cross-sectional view of the front flange of the mixing rear section of the present invention;

[0034] Figure 14 (b) is a front view of the flange of the mixing rear section of the present invention;

[0035] Figure 15 This is a schlieren photograph of the present invention in a test after being assembled with a combustion chamber;

[0036] Figure 16 is the pressure curve measured by the pressure sensor during the test process of the present invention;

[0037] Figure 17 This is a schlieren photograph of a stationary oblique detonation wave in a combustion chamber during the test of the present invention;

[0038] Figure 18 This is a photo of the schlieren in the combustion chamber after the length of the mixing section is shortened in the present invention; DETAILED DESCRIPTION

[0039] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0040] like Figure 1 and Figure 2 As shown, a support plate type fuel mixing device of an oblique detonation engine includes a front mixing section consisting of a flange 1, a flange 8, an upper wall 2 of the mixing section, a lower wall 3 of the mixing section, a left wall 4 of the mixing section, and a right wall 5 of the mixing section, and a rear mixing section consisting of a flange 9, a flange 12 and four walls. The total length of the mixing section is 1128 mm, of which the length of the front mixing section is 786 mm. The central support plate 6 is located near the flange 1 and is connected to the left wall 4 of the front mixing section by screws.

[0041] like Figure 3 As shown, in this embodiment, a concave step surface is machined on the front end surface of the front flange 1 to ensure airtightness when connected to the rear flange of the shock tunnel nozzle. The front flange 1 has 12 through holes for bolt connection evenly distributed along the circumference, and the through hole diameter is

[0042] like Figure 4 (a) Figure 4 As shown in (b), in this embodiment, a through hole 4-1 having the same longitudinal cross-sectional shape as the central injection support plate 6 is processed on the left wall surface 4 of the mixing section, and the number of the through hole 4-1 is 1. A circular through hole 4-2 for an observation window is processed on the left wall surface 4 of the mixing section, and the through holes 4-2 are evenly distributed along the flow direction. The number of the through holes 4-2 is 3, and the distance between the centers of the through holes is 300 mm.

[0043] like Figure 5 (a) Figure 5As shown in (b), in this embodiment, a blind hole 5-1 having the same longitudinal cross-sectional shape as the central injection support plate 6 is processed on the inner side of the right wall surface 5 of the mixing section to support the central support plate 6.

[0044] like Figure 6 As shown, in this embodiment, a stepped pressure measuring hole 2-1 is processed on the upper wall 2 of the mixing section. The stepped pressure measuring hole 2-1 is located on the symmetry axis (center line) of the upper wall 2 of the mixing section and is distributed along the direction of airflow. The number of the stepped pressure measuring holes 2-1 is 14, and the spacing between the stepped pressure measuring holes is x, 50mm≤x≤140mm. In the present invention, the distribution spacing of the pressure measuring holes 2-1 on the upper wall 2 of the mixing section is not limited to Figure 6 shown.

[0045] like Figure 7-10 As shown, the central injection support plate 6 is connected to the left wall 4 of the mixing section with screws and can be replaced. Figure 8 The central injection support plate 6 in (a) is used to inject gas fuel. The upper and lower walls of the central injection support plate 6 are processed with injection holes 6-1. The diameter of the injection hole is There are 28 holes, 14 on the upper wall and 14 on the lower wall, and the 14 injection holes 6-1 are arranged in two rows. The spacing of the injection holes 6-1 along the airflow direction is y, y = 22 mm, and the spacing perpendicular to the airflow direction is x, x = 16 mm. In particular, the central injection support plate in the present invention has another different structure. Figure 8 The central injection support plate 6 in (b) is used to inject liquid fuel. Figure 8 The difference in (a) is that the spacing x of the first row of injection holes 6-1 is 16 mm, and the hole diameter is The spacing of the second row of injection holes 6-1 is x=8mm, and the hole diameter is Different central injection support plates can be used to inject different fuels. When the required fuel concentration is low, a single fuel supply line is used to supply fuel, using a single row of injection holes. When the required fuel concentration is high, two fuel supply lines are used to supply fuel simultaneously, and two rows of injection holes are used for injection.

[0046] like Figure 9 As shown, in this embodiment, a fuel cavity 6-2 is machined in the center of the central injection support plate. There are two fuel cavities 6-2, each 2 mm high and 10 mm wide. To avoid strong oblique shock waves in the mixing channel that affect mixing performance, the front guide wedge surface of the central injection support plate 6 is formed at an angle α with the horizontal direction, and the angle α satisfies the following conditions: 5°≤α≤10°. In this embodiment, the front guide wedge surface of the central injection support plate 6 is formed at an angle α of 6° with the horizontal direction. To create a recirculation zone of appropriate size, the rear guide wedge surface is formed at an angle β of 18° with the horizontal direction. The central support plate 6 is 4 mm thick.

[0047] like Figure 11 As shown, the number of the observation window cover plates 7 is 3, and through holes 7-1 are processed along the circumference of the observation window cover plates 7. The through holes 7-1 are evenly distributed, and the diameter of the through holes is The number of through holes is 8. The observation window cover 7 is processed with a stepped through hole 7-2. The dimensions of the two ends of the through hole are and Used for installing and positioning the observation window optical glass 10.

[0048] like Figure 12 As shown, in this embodiment, the number of observation window optical glasses 10 is 3, the optical glass is made of quartz, the optical glass is stepped, and the maximum diameter is The minimum diameter is The total thickness is 30mm. In order to meet the requirements of high-speed photography, the glass surface processing has higher requirements on surface roughness, refractive index and transmittance.

[0049] like Figure 13-14 As shown, in this embodiment, a concave step surface is machined on the rear end face of the mixing front section rear flange 8, and a sealing groove 1 is machined in the concave step surface for placing a sealing rubber ring. A convex step surface is machined on the front end face of the mixing rear section front flange 9 to ensure airtightness when connected to the mixing rear section front flange 9. The rear end flange 8 is uniformly distributed along the circumference with through holes for bolt connection. The number of through holes is 12, and the diameter is The size, structure and features of the rear flange 12 of the rear mixing section are completely consistent with those of the rear flange 8 of the front mixing section.

[0050] During the test, the mixing device of the present invention was connected to the combustion chamber to form an oblique detonation engine, and photos of the oblique detonation engine in operation were taken using a high-speed camera. Figure 15 As shown, the time period between 17.376ms and 17.710ms is the initial startup period of the superenthalpy shock tunnel. The three observation windows of the present invention light up in sequence along the flow direction, indicating that the driving shock wave generated by the operation of the superenthalpy shock tunnel propagates to the combustion chamber. At 17.843ms, the driving shock wave reaches the combustion chamber and induces an oblique shock wave. It can be observed that the combustion chamber observation window lights up. At 18.176ms, the oblique detonation wave in the combustion chamber detonates. Between 18.176ms and 38.176ms, the superenthalpy shock tunnel enters a stable operation stage. Bright light appears in the combustion chamber, while no bright light is observed in the circular observation window of the mixing device. Figure 16 As shown in the figure, the curves p1 to p13 are the pressure curves measured by 13 pressure sensors installed on the upper wall of the mixing device. Figure 16 Combine Figure 15It can be seen that between 18ms and 34ms, that is, during the stable operation period of the oblique detonation engine, the pressure values ​​at each pressure measuring point of this embodiment are stable, the mixing section fuel does not show the phenomenon of premature combustion chamber, and the combustion chamber flame does not propagate upstream, indicating that the present invention solves the problem of premature combustion of high Mach number incoming flow mixing. In addition, during the test, a schlieren photograph of the stationary oblique detonation wave in the combustion chamber was taken, as shown in the figure. Figure 17 As shown, it is explained that the present invention achieves a better rapid mixing effect.

[0051] Shorten the mixing section length, only use the mixing front section of the present invention to conduct the test, the high-speed camera took the schlieren photos in the combustion chamber during the test. Figure 18 As shown in the figure, it can be observed that when the mixing section is shortened to 786mm, the uniformity of the fuel in the direction perpendicular to the mainstream becomes worse, and the fuel mass fraction in the boundary layer decreases, so the oblique detonation wave fails to detonate successfully. Only the high-temperature reaction area formed by the intersection of shock waves is observed in the picture. Figure 17 and Figure 18 It can be seen from the experimental phenomena that the total length of the mixing section designed in the present invention meets the test requirements and has an excellent mixing effect.

[0052] During operation, gaseous or liquid fuel is delivered to the fuel supply line via a gas tank. The fuel is injected into the mixing channel at a predetermined initial velocity from the injection orifice, perpendicular to the main flow direction. Leveraging the mechanism of transverse vortex enhancement (i.e., the large-scale coherent structure induced by the shedding of the support plate boundary layer and the stable recirculation zone at the rear of the support plate), the fuel is drawn into the recirculation zone, achieving low-speed mixing. With the combined effect of a reasonable support plate configuration and an appropriate mixing channel length, the temperature within the mixing section does not exceed the fuel's ignition point, preventing premature combustion. The fuel rapidly diffuses within the main flow, achieving a favorable spatial distribution. Ultimately, the mixed gas detonates in the combustion chamber, forming a stationary oblique detonation wave.

Claims

1. A support plate type fuel mixing device for an oblique detonation engine, comprising a mixing section and a central injection support plate, characterized in that: The mixing section is composed of a first flange, a second flange, an upper wall of the mixing section, a lower wall of the mixing section, a left wall of the mixing section, and a right wall of the mixing section; The left wall of the mixing section is processed with a through hole that is consistent with the longitudinal cross-section shape of the central injection support plate, and the inner side of the right wall of the mixing section is processed with a blind hole that is consistent with the longitudinal cross-section shape of the central injection support plate for supporting the central injection support plate; The mixing section is divided into a front mixing section and a rear mixing section connected to each other, so that the length of the entire mixing section is adjustable to adjust the uniformity of the fuel in the direction perpendicular to the airflow direction and the fuel mass fraction in the boundary layer; The central injection support plate is arranged in the front mixing section to inject fuel into the mixing section perpendicular to the airflow direction; the front end of the central injection support plate is provided with a guide wedge surface to suppress the shock wave intensity in the mixing flow channel and prevent the fuel from burning prematurely after the shock wave surface; the rear end of the central injection support plate is provided with a guide wedge surface to generate a recirculation zone, and the fuel is drawn into the recirculation zone for mixing; A fuel cavity is provided in the central injection support plate for connecting to a fuel supply line to allow fuel to flow into the central injection support plate. A plurality of injection holes are arranged side by side on the upper and lower walls of the central injection support plate, and the arrangement direction of the injection holes is perpendicular to the flow direction of the airflow. A plurality of observation windows are arranged at equal intervals on the side of the mixing section for photographing whether premature combustion occurs in the mixing section.

2. The support plate type fuel mixing device for an oblique detonation engine according to claim 1, characterized in that: The number of the fuel chamber is one or a plurality of fuel chambers arranged side by side.

3. The support plate type fuel mixing device for an oblique detonation engine according to claim 1, characterized in that: The central injection support plate and the mixing front section are detachable structures to replace the central injection support plate for injecting liquid fuel or gas fuel, wherein the size of the injection hole for injecting liquid fuel is smaller than the size of the injection hole for injecting gas fuel.

4. The support plate type fuel mixing device for an oblique detonation engine according to claim 1, characterized in that: The included angle α between the guide wedge surface provided at the front end of the central injection support plate and the horizontal direction satisfies the following: 5°≤α≤10°.

5. The support plate type fuel mixing device for an oblique detonation engine according to claim 1, characterized in that: Pressure measuring holes are arranged at equal intervals on the mixing section.

6. The support plate type fuel mixing device for an oblique detonation engine according to claim 1, characterized in that: The front mixing section and the rear mixing section are connected via a flange.

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