A vertically distributed strut based oblique detonation engine
By employing a vertically distributed support plate design and numerical simulation optimization in the oblique detonation engine, the problem of difficult fuel diffusion under the horizontal support plate injection structure was solved, achieving uniform fuel distribution and stable detonation in the vertical direction, and shortening the detonation distance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
- Filing Date
- 2023-11-21
- Publication Date
- 2026-06-05
Smart Images
Figure CN122148428A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of engine technology, and in particular to a slant detonation engine based on vertically distributed support plates. Background Technology
[0002] The oblique detonation engine is a novel air-breathing propulsion system with a structure similar to a scramjet engine, offering significant advantages in hypersonic flight above Mach 9. However, the internal injection configuration of the oblique detonation engine faces challenges such as short fuel residence time and uneven mixing due to the high Mach number of the incoming flow. Therefore, achieving efficient and low-drag mixing of fuel in the combustion chamber of the oblique detonation engine within a very short time and achieving stable initiation has become a critical problem to be solved in its design. It utilizes oblique detonation to achieve efficient combustion in supersonic airflow. Because oblique detonation combustion approximates isochoric combustion, it offers a series of advantages compared to deflagration combustion, including faster energy release rate, self-pressurization, high thermal cycle efficiency, and low entropy increase. Furthermore, the oblique detonation engine possesses unique advantages in terms of overall size, wind resistance, thermal protection, and performance control. In hypersonic aerospace flight, the net thrust of traditional scramjet engines drops significantly after reaching a certain Mach number threshold. The oblique detonation engine, however, holds the potential to break through the Mach number limit of existing hydrocarbon-fueled scramjet engines, thus possessing broad development prospects. Depending on the fuel injection location, oblique detonation engines can be divided into two configurations: internal injection and external injection. One of the key technologies for internal injection oblique detonation engines is to achieve efficient and low-resistance mixing of fuel over an ultra-short distance and to achieve stable initiation on the wedge surface. This invention focuses on the mixing and initiation characteristics within the combustion chamber of a novel support plate-configured oblique detonation engine.
[0003] There are relatively few inventions of mixing sections for oblique detonation engines, both domestically and internationally, but many inventions of mixing sections for scramjet engines. Because oblique detonation and scramjet engines share a high degree of similarity in their inlet and combustion chamber designs, referencing the fuel mixing methods of scramjet engines can greatly assist in the design of the mixing section of the scramjet engine combustion chamber. Numerous inventions have been made both domestically and internationally regarding scramjet engine mixing, and these mixing methods can be broadly categorized into two main types: passive mixing enhancement and active mixing enhancement. Bracket injection, as a type of passive mixing enhancement, was proposed by the Langley Invention Center in the United States in the 1970s. This mixing method, due to its excellent mixing performance and combustion enhancement effect, has become one of the hot topics in scramjet engine inventions. Currently, the two mainstream configurations of scramjet engine combustion chambers internationally are the German Aerospace Center (DLR) configuration and the NAL configuration.
[0004] Building upon this, regarding strut injection, Sujith et al. experimentally and computationally investigated the effect of strut angle on fuel mixing under high-speed flow conditions, observing that increasing the strut angle improves fuel mixing within the scramjet combustion chamber. Rahul KS et al. developed methods for evaluating the effects of straight and conical struts on fuel mixing and flow field characteristics in scramjet engines. Their results showed that, given a strut shape, hydrogen exhibits superior mixing efficiency and diffusion rate, and for a given fuel type, straight struts provide better fuel mixing compared to conical struts.
[0005] Choubey G et al. discovered in an invention that adding two supports inside the combustion chamber accelerates fuel mixing and enhances combustion intensity within a scramjet engine combustion chamber compared to single-support injection. Therefore, based on the invention of single-support injection, they proposed an injection strategy that combines multiple supports with wall injection, concluding that collaborative injection can improve fuel penetration depth and enhance mixing. Kummitha et al. improved upon ordinary supports, inventing two heterogeneous support types—rocket-shaped and double-arrow-shaped—and their impact on scramjet combustion chamber mixing. They also adjusted the structure of the original support tail injection by adding inclined injection in the vertical direction, resulting in better mixing and a larger combustion zone.
[0006] In China, Zhang and Han et al. invented a slant-detonation engine using an external injection configuration, employing three parallel support plates at the front of the inlet as the fuel injection method. Numerical simulations showed that the compression of the slant shock wave, the initial expansion of the fuel jet, and the momentum exchange of the lateral jet can enhance fuel-air mixing. Zhang and Han also conducted wind tunnel tests with this injection configuration using hydrogen and aviation kerosene as fuels, successfully achieving slant-detonation initiation and stabilization on the wedge surface. Yu invented wall injection and support plate injection methods to study the combustion performance of hydrogen fuel in a combustion chamber. Results showed that using support plates as the fuel injection device improved fuel penetration depth and mixing efficiency. Hou conducted numerical simulations and mainly analyzed the flow and combustion characteristics within a scramjet combustion chamber. The conclusion showed that the location of hydrogen fuel injection significantly affects combustion performance. Huang used Large Eddy Simulation (LES) to discuss the flow characteristics around the support plates in a scramjet combustion chamber and revealed the relevant laws governing drag performance, mixing enhancement mechanisms, and the interaction between flow and combustion.
[0007] As can be seen from the above literature, both the external-injection oblique detonation engine and the scramjet engine tested by Zhang and Han currently employ horizontal support plates. Because the fuel mixing distance in the internal-injection oblique detonation engine is shorter than that in the external-injection configuration, using horizontal support plates under high Mach flow conditions makes vertical fuel diffusion extremely difficult, significantly increasing the difficulty of stable initiation on the wedge surface. Furthermore, compared to scramjet engines, oblique detonation engines have different flame stabilization mechanisms due to their different combustion organization. Therefore, the above analysis indicates that using horizontal support plates as the injection structure for internal-injection oblique detonation engines has certain drawbacks. Summary of the Invention
[0008] The purpose of this invention is to address the shortcomings of the prior art by providing a slant detonation engine based on vertically distributed support plates, thereby solving the problem that the injection structure of slant detonation engines with horizontal support plates as internal injection configurations has certain defects.
[0009] This invention specifically provides the following technical solution: a tilting detonation engine based on vertically distributed support plates, comprising:
[0010] The air intake section is used to compress the supersonic incoming air;
[0011] The mixing section is connected to the air intake section. A support plate perpendicular to the bottom of the mixing section is provided inside the section. The front end of the support plate is pointed. A fuel injection structure is formed by the support plate and the inner wall of the mixing section. The fuel injection structure is used to inject fuel.
[0012] The initiation section, connected to the rear end of the mixing section, is used to compress the supersonic flow after mixing in the fuel injection structure, forming a slanted detonation shock wave during ignition and detonation.
[0013] Preferably, the mixing section is meshed using a polyhedral mesh in unstructured processing.
[0014] Preferably, the fuel injection structure includes two support plates arranged in parallel, with each support plate 27mm away from the sidewall of its nearest mixing section. ， Used to generate fuel distribution in the vertical direction.
[0015] Preferably, each of the support plates has a length of 75 mm, and the distance from the pointed front end of the support plate to the inlet of the mixing section is 75 mm, so as to provide sufficient inflow distance.
[0016] Preferably, the mixing section has a total length of 573 mm, a width of 81 mm, and a height of 50 mm.
[0017] Preferably, the detonation section is composed of a combination of a cuboid and a wedge-shaped body.
[0018] Preferably, the length of the detonation section is 81mm, the width of the detonation section is 32.5mm, and the height of the detonation section is 5mm.
[0019] Preferably, the cuboid of the detonation section has a width of 5 mm, the wedge-shaped part has a height of 10 mm, and the inclination angle of one wall of the wedge-shaped part is 20°.
[0020] Preferably, the mixing section is solved based on the Reynolds-averaged steady-state Navier-Stokes equations, the turbulence model adopts the k-ωSST two-equation turbulence model, and the AUSM+AUSM vector flux splitting scheme is used in the simulation calculation to capture the shock wave structure.
[0021] Preferably, the wall surface of the mixing section is a non-slip constant temperature cold wall surface with a wall temperature of 300K.
[0022] Compared with the prior art, the present invention has the following significant advantages:
[0023] The fuel distribution in the detonation section spatial structure provided by this invention is highly uniform in the vertical direction, which can better achieve stable detonation. The increased angle of the sharp corner at the front end of the support plate can enhance the diffusion and mixing of hydrogen at the outlet of the mixing section, and at the same time cause the hydrogen distribution structure to bend. The angle of the front end of the support plate causes the detonation structure to tilt and shortens the detonation distance within a certain range. At the same time, the angle of the front end of the support plate enhances the mixing of hydrogen and reduces the detonation distance within a certain range, so as to achieve early detonation on the wedge surface, thereby forming a stable oblique detonation shock wave earlier. Attached Figure Description
[0024] Figure 1 The tilt detonation engines have different support plates, where: (a) is a tilt detonation engine with horizontal support plate injection, and (b) is a tilt detonation engine with vertical support plate injection.
[0025] Figure 2 The diagrams show the mixing section under different support plate fuel injection structures, where: (a) is a model diagram of the mixing section under a horizontal support plate fuel injection structure, and (b) is a model diagram of the mixing section under a vertical support plate fuel injection structure.
[0026] Figure 3 The diagram shows the model of the detonation section, where: (a) is the cross-sectional model of the basic detonation section. Figure 3 (b) is a mesh model diagram of the detonation section;
[0027] Figure 4 Pressure contour maps of different grid initiation sections provided for this invention;
[0028] Figure 5 The present invention provides curves showing the variation of temperature and OH density near the wall surface under different mesh accuracies.
[0029] Figure 6 Temperature contour maps of the outlet section of the detonation section under the horizontal (upper) and vertical (lower) support plate injection, provided for the present invention;
[0030] Figure 7 A schematic diagram of a two-dimensional ODW (oblique detonation wave) provided by the present invention;
[0031] Figure 8 Hydrogen contour lines and flow field structure diagrams under different vertical support plate angles provided by the present invention;
[0032] Figure 9 Hydrogen mass fraction diagrams at the outlet of the vertical support plate injection mixing section at different angles provided by the present invention;
[0033] Figure 10 The contour maps of the outlet pressure (top) and temperature (bottom) of the detonation section under vertical support plate injection at different angles provided by the present invention;
[0034] Figure 11 Contour maps of the outlet pressure (top) and temperature (bottom) of the lower initiation section injected by vertical support plates at different angles, provided for the present invention;
[0035] Figure 12 The present invention provides temperature contour maps of the detonation section under vertical support plate injection at different angles.
[0036] Figure 13 Isosurface diagrams of detonation temperature under vertical support plate injection at different angles provided by the present invention;
[0037] Figure 14 The present invention provides contour maps of detonation temperature and curves showing the variation of detonation distance under vertical support plate injection at different angles.
[0038] Figure 15 The following are different perspective views of the support plate: (a) is a two-dimensional cross-section of the vertical support plate, (b) is a schematic diagram of the arrangement of the injection nozzles at the tail of the horizontal support plate, and (c) is a schematic diagram of the arrangement of the injection nozzles at the tail of the vertical support plate. Detailed Implementation
[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.
[0040] This invention uses hydrogen as fuel and divides the oblique detonation combustion chamber into two parts: a mixing section and an initiation section. First, the superiority of vertical support plate injection over the traditional horizontal support plate injection structure in achieving stable oblique detonation initiation performance was analyzed, revealing the importance of uniform vertical fuel distribution for stable initiation. Based on this, the influence of the vertical support plate angle on mixing and initiation was analyzed. Observations showed that increasing the vertical support plate angle leads to a decrease in the hydrogen mass fraction at the mixing section outlet and causes bending of the hydrogen distribution structure. In the initiation section, this results in tilting of the initiation area and a reduction in the initiation distance within a certain range. Therefore, increasing the vertical support plate angle enhances hydrogen mixing while reducing the initiation distance to a certain extent, achieving earlier initiation on the wedge surface and thus forming a stable oblique detonation wave earlier.
[0041] Specifically, this invention provides a slant detonation engine based on vertically distributed support plates, comprising: an intake section, a mixing section, and an initiation section. Specifically, it includes:
[0042] The intake section is used to compress the supersonic incoming flow. The mixing section is connected to the intake section and contains a support plate perpendicular to the bottom of the mixing section. The front end of the support plate is pointed, and a fuel injection structure is constructed by the support plate and the inner wall of the mixing section. The fuel injection structure is used to inject fuel, thereby forming a relatively uniform fuel distribution in the vertical direction to match the vertically stable detonation structure in the three-dimensional direction of the oblique detonation. The detonation section is located at the rear end of the mixing section and is connected to the rear end of the mixing section. It is used to compress the supersonic incoming flow after mixing by the fuel injection structure, thereby forming an oblique detonation shock wave during ignition and detonation. At the same time, the detonation area and distance can be changed by changing the angle of the pointed end of the vertical support plate.
[0043] The blending section is meshed using a polyhedral mesh in unstructured programming. The fuel injection structure includes two support plates, which are arranged parallel to each other, with each support plate 27mm away from the nearest sidewall of the blending section. ， This is used to generate vertical fuel distribution. Each support plate is 75mm long, and the distance from the pointed tip of the support plate to the inlet of the blending section is 75mm, to provide sufficient inflow distance. The total length of the blending section is 573mm, the width is 81mm, and the height is 50mm.
[0044] The detonation section is composed of a cuboid and a wedge-shaped body. The detonation section is 81 mm long, 32.5 mm wide, and 5 mm high. The cuboid of the detonation section is 5 mm wide, the wedge-shaped body is 10 mm high, and one wall of the wedge-shaped body has an inclination angle of 20°.
[0045] The mixing section is solved based on the Reynolds-averaged steady-state Navier-Stokes equations. The turbulence model adopts the k-ωSST two-equation turbulence model, and the AUSM+AUSM vector flux splitting scheme is used in the simulation to capture the shock wave structure. The walls of the mixing section are all non-slip isothermal cold walls with a wall temperature of 300K. Example 1:
[0046] Among them, such as Figure 1 Figures (a) and (b) show the flow field diagrams of the internal injection configuration of the oblique detonation engine under horizontal and vertical support plate structures, respectively. After being compressed by a forebody shock wave and a lip-reflecting shock wave, the incoming flow enters the combustion chamber and mixes with the hydrogen injected by the support plate. Initiation combustion occurs at the tail wedge surface, and the combustion products generated in this process expand at the nozzle location, thus generating thrust. This invention uses the parameters (static pressure: 61004 Pa, static temperature: 857.7 K) after compression through the two-stage inlet at a flight altitude of 25 km (static pressure: 2549 Pa, static temperature: 221.6 K) and a flight speed of Mach 9 as the inlet parameters for the combustion chamber section. This invention only simulates the oblique detonation combustion chamber section and does not consider the inlet section. Furthermore, considering that global calculation of the combustion chamber section would increase the computational load, this invention divides the oblique detonation engine combustion chamber model into two parts: a mixing section and an initiation section, and performs separate simulation calculations for each part.
[0047] Table 1 Boundary conditions of the mixed section
[0048]
[0049] The mixing section is meshed using a polyhedral mesh in unstructured programming. (See figure.) Figure 2 (a) and (b) show the mixing section models under horizontal and vertical support plate fuel injection structures, respectively. The total length of the mixing section is approximately 573 mm, the width is 81 mm, and the height is 50 mm. The length of both types of supports is 75 mm, and the distance from the front sharp corner to the mixing section inlet is also the same, 75 mm. The horizontal support plate is located at the center of the upper and lower walls, while the vertical support plate is a double-row support plate structure, with each support plate 27 mm from its nearest sidewall. The mixing section is solved based on the Reynolds-averaged steady-state Navier-Stokes equations, and the turbulence model adopts the k-ωSST two-equation turbulence model. The simulation calculation uses the AUSM+AUSM (AdvectionUpstream Splitting Method) vector flux splitting scheme, which has high resolution, good stability, and can clearly capture the shock wave structure. The inlet boundary of the mixing section is shown in Table 1. The wall surface is a non-slip isothermal cold wall with a wall temperature of 300 K.
[0050] The detonation stage model is as follows:
[0051] The inlet of the detonation section is connected to the outlet of the mixing section, such as... Figure 3As shown in (a), the model consists of a straight rectangular section and a wedge-shaped section. The length of the detonation section corresponds to the width of the mixing section, which is 81 mm, approximately 32.5 mm wide, and 50 mm high. The straight section is 5 mm wide, and the wedge-shaped section is 10 mm high with an angle of 20°. Figure 3 (b) is the mesh model for the detonation section. A structured mesh is used globally, and the boundary layer mesh is refined to ensure that y+ is less than 10. The reaction mechanism of the detonation section model adopts the 19-step reaction mechanism of hydrogen with 9 components proposed by Jachimowski. Since the inlet of the detonation section is the outlet of the mixing section, the boundary parameters of the mixing section outlet are used as the boundary parameters of the detonation section inlet for initialization.
[0052] Perform mesh independence verification:
[0053] Because mesh precision has a significant impact on the simulation results of oblique detonation shock waves, this invention selected three mesh precisions (0.2 mm, 0.3 mm, and 0.4 mm) to verify the mesh independence of the initiation section. A cross-section was created at Z = 0.0135 m in the initiation section under different mesh precisions, and temperature and OH density data were collected at a distance of 0.001 m above the wall on this cross-section to plot the corresponding curves. The results are as follows: Figure 4 Pressure contour maps of different sizes shown in (a)-(c) and Figure 5 The temperature and OH density comparison curves are shown. Analysis reveals that the simulation results for detonation waves at grid precisions of 0.2 mm and 0.3 mm are not significantly different, while the simulation results at a grid precision of 0.4 mm deviate significantly from the above two. Therefore, a 0.4 mm grid precision does not meet the simulation requirements. To meet the accuracy requirements while reducing computational load, this invention uses a 0.3 mm grid precision in subsequent detonation stage designs.
[0054] A comparison of the detonation effects of horizontal and vertical support plates:
[0055] To compare the advantages and disadvantages of horizontal and vertical support plate distributions in oblique detonation initiation, this invention modifies both horizontal and vertical support plates by fixing basic parameters and changing only the support plate distribution. In the comparative invention, the support plate angle is always 4°, while other parameters remain constant. By analyzing the oblique detonation initiation phenomenon on the wedge surface, the differences between horizontal and vertical support plates are determined, thus selecting a support plate distribution method more favorable for oblique detonation initiation. Figure 6 As shown, by comparing levels ( Figure 6 (a)) and vertical support plate ( Figure 6 (b) The temperature cloud map at the outlet of the detonation section clearly shows that no obvious detonation phenomenon occurred on the lower wedge surface of the horizontal support plate, while obvious detonation phenomenon occurred in the vertical support plate. Therefore, it can be concluded that under the same incoming flow and injection conditions, the vertically distributed support plate has a greater advantage in achieving stable detonation of oblique detonation.
[0056] In previous inventions of oblique detonation shock waves, the incoming flow was generally assumed to be a homogeneous premixed gas, thus allowing the following to be obtained: Figure 7 The diagram illustrates a two-dimensional oblique detonation shock wave initiation structure. Applying this assumption to a three-dimensional initiation model results in the uniformity of fuel distribution along the vertical direction of a certain cross-section in the three-dimensional model. This conclusion is referred to as the uniformity of vertical fuel distribution satisfying stable three-dimensional initiation of oblique detonation shock waves. In the three-dimensional model, since ODW initiation gradually develops from the tip of the wedge, the horizontal support plate injection method cannot guarantee a continuous fuel supply along the Y-direction at the bottom of the wedge. The vertically arranged support plate injection structure, due to its better fuel uniformity in the vertical direction, better meets the three-dimensional initiation requirements of oblique detonation shock waves than the horizontal support plate.
[0057] Among them, the influence of the vertical support plate angle on the mixing effect is as follows:
[0058] To more precisely investigate the influence of vertical support plates on the three-dimensional oblique detonation initiation characteristics, this invention introduces the variable of support plate angle. By changing the angle of the vertical support plate, the influence of angle changes on mixing and oblique detonation initiation can be obtained.
[0059] Table 2 shows the different angles.
[0060] Case 1 2 3 4 angle / ° 4 6 8 10
[0061] Table 2 shows examples corresponding to different angles. This invention, while keeping the incoming flow and nozzle injection parameters constant, investigates the influence of the vertical support plate angle on the hydrogen mixing and diffusion in the mixing section, as well as the temperature and pressure changes after the support plate, by changing the angle of the double-row vertical support plates. For example... Figure 8 As shown in (a)-(d), this invention simulated the mixing section under four different vertical support plate angles, and corresponding cross-sections were created at five locations: X = 0.15m, 0.25m, 0.35m, 0.45m, and 0.55m. X = 0.15m corresponds to the location of the hydrogen nozzle at the tail of the support plate. The large image on the left represents the flow field structure of hydrogen flow and diffusion in the mixing section, while the four smaller images on the right, from top to bottom, are the hydrogen mass fraction cloud maps at four cross-sections from X = 0.25m to X = 0.55m under the same vertical support plate angle. Figure 8 It can be seen that, at the same angle, as the mixing distance increases, the hydrogen mass fraction decreases while the distribution range gradually expands. Along the path of this expanded hydrogen distribution range, the hydrogen distribution structure also begins to bend to both sides from its original vertical structure, and this phenomenon becomes increasingly pronounced with increasing angle.
[0062] Analysis reveals that because the airflow passing through the middle of the two support plates undergoes compression by an additional oblique shock wave compared to the airflow on either side, the airflow in the middle expands to both sides due to the higher pressure in the subsequent flow after the support plates, causing it to bend. When the angle is small, the pressure difference is small, and the hydrogen distribution bends, but the phenomenon is not obvious. As the angle increases, the pressure difference gradually increases, and the hydrogen distribution therefore exhibits a more pronounced bending phenomenon.
[0063] Data from the mixing section outlet under different vertical support plate angles were extracted and analyzed for comparison. For example... Figure 9 As shown, Cases 1-4 (i.e. Figure 9 (a)-(d) are cloud maps showing the hydrogen mass fraction distribution at the outlet of the mixing section under vertical support angles ranging from 4° to 10°. The outlet hydrogen distribution exhibits a double-column symmetrical structure. Observing one column reveals that the hydrogen distribution in the horizontal Z-direction follows a Gaussian function pattern. In the vertical Y-direction, the hydrogen mass fraction at the center tends to be uniform, and the value gradually decreases as the angle increases. The hydrogen mass fraction near the wall is less affected by the angle and remains stable within a certain range.
[0064] Among them, the influence of the vertical support plate angle on the detonation effect is as follows:
[0065] Based on the calculations for the blending section, the boundary parameters at the outlet of the blending section are extracted as the boundary conditions at the inlet of the detonation section. Due to the symmetrical structure of the hydrogen distribution in the blending section, this invention employs a symmetrical plane structure for simplification in the detonation section. The result is as follows: Figure 10 (a)-(h) show the pressure and temperature contour maps at the Z-axis outlet of the detonation section of the vertical support plate at different angles. Figure 10 (a) and (e) are respectively the pressure and temperature cloud diagrams at the Z-axis outlet of the vertical support plate detonation section at the same angle; Figure 10 (b) and (f) are respectively the pressure and temperature cloud diagrams at the Z-axis outlet of the vertical support plate detonation section at the same angle; Figure 10 (c) and (g) are respectively the pressure and temperature cloud diagrams at the Z-axis outlet of the vertical support plate detonation section at the same angle; Figure 10 (d) and (h) are respectively the pressure and temperature cloud diagrams at the Z-axis outlet of the vertical support plate detonation section at the same angle.
[0066] Analysis of pressure contour maps for different cases reveals that in Case 1, a high-pressure zone forms above the Z=0m position. This is a result of the interference between the oblique detonation waves from the two initiation zones. As the angle of the vertical support plate in the mixing section increases, the high-pressure zone above the Z=0m position in the initiation section gradually disappears. (Comparison) Figure 9 The hydrogen mass fraction cloud map at the outlet of the mixing section shows that this is a result of the hydrogen distribution structure gradually bending as the angle increases. In the analysis... Figure 10Temperature contour plots from different cases show that the difference in the mass fraction of hydrogen at the inlet of the detonation section at different vertical support angles has little impact on the maximum temperature at the outlet surface of the detonation section. Further investigation reveals that the oblique detonation initiation structure is affected by the inlet hydrogen distribution structure, evolving from the approximately three-dimensional vertical initiation in Case 1 to the three-dimensional inclined initiation at an angle of nearly 60° to one side plane in Case 4. Figure 10 A faint dividing line (indicated by the black arrow) appeared at the exit of the detonation section in different cases, along which a temperature step occurred. According to the two-dimensional detonation model, this is the three-dimensional representation of the two-dimensional oblique detonation slip line, specifically a surface. This line also bends when the hydrogen distribution structure bends. This indicates that the oblique detonation slip surface is a bendable plane affected by the inlet hydrogen distribution structure.
[0067] Because three-dimensional initiation involves a spatial structure, a cross-section is obtained by selecting the location within the initiation range that provides stable initiation and the shortest initiation distance, as shown in the figure. Figure 11 (a)-(d) show the pressure (top) and temperature (bottom) contour maps at different angles. Analysis of the contour maps shows that the oblique detonation successfully initiated and stabilized at a certain height on the wedge surface under the four support plate angles. It can be clearly seen that when the flow passes through the wedge surface, it first forms a shock wave. After the shock wave, the airflow heats up and pressurizes, and after traveling a certain distance, it triggers deflagration. The deflagration wave is rapidly formed and interacts with the oblique shock wave, eventually detonating at the three wave points to form the oblique detonation wave. The slip lines can be clearly seen in Cases 1-4, and the reflected transverse wave can also be seen in Case 1-2. To further refine the investigation of the oblique detonation initiation distance under vertical support plate injection at different angles, the initiation distance is defined here as the shortest distance from the deflagration wave front position to the wedge tip. Theoretically, the mixed gas requires a certain ignition delay time to initiate deflagration after the oblique shock wave compression distance. Since the deflagration wave front is also the location where the chemical reaction begins to release heat, the location of the temperature step in the region behind the oblique shock wave and in front of the deflagration wave in the temperature cloud diagram is analyzed to determine the location of the deflagration wave front during detonation, and thus ultimately determine the detonation distance. Figure 12 As shown, Figure 12 ((a), (b), (c), (d)) are temperature contour maps of the initiation section cross-section under vertical support plate injection at different angles (4°, 6°, 8°, 10°).
[0068] Through analysis Figure 13From Cases 1-2 of (a)-(d), it can be seen that when the angle of the vertical support plate is between 4° and 8°, the temperature all exhibits a step at the 1450K isopleth. At an angle of 10°, analysis shows that the temperature steps between 1540K and 1630K; here, 1580K is chosen. To more clearly illustrate the relative relationship between the deflagration wave front temperature at the detonation center and the temperature field of the entire detonation area, isopleths were constructed for the deflagration wave front temperatures at the detonation center of the vertical support plate at the above different angles (4°, 6°, 8°, 10°), as shown below. Figure 13 Temperature isosurface plots shown in (a)-(d).
[0069] Depend on Figure 14 It can be seen that an inwardly concave gap exists in the temperature isosurface of the support plates from 4° to 8°. Moreover, this gap gradually decreases with increasing angle. Analysis of the positive Z-axis reveals that the hydrogen mass fraction at the outlet of the mixing section under the vertical support plate injection exhibits a Gaussian distribution in the Z-direction, i.e., high in the middle and low at the edges. Theoretically, at the same inflow velocity, a higher hydrogen mass fraction per unit area results in a lower Mach number and a weaker oblique shock wave formed on the wedge surface, thus manifesting as a concave shape towards the center on the temperature isosurface. As the angle of the vertical support plate increases, the overall hydrogen mass fraction begins to decrease, thus the concave gap gradually decreases. The 10° support plate, due to its lower hydrogen mass fraction, exhibits a stronger oblique shock wave and does not show a significant concave structure overall. Figure 12 The temperature contour lines corresponding to the deflagration wave fronts in Cases 1-4 (a)-(d) are extracted as follows: Figure 14 The initiation distance comparison curve and the initiation distance variation curve are shown. Figure 15 (a) The length of the support plate is 75mm, and the angle can be changed according to the requirements; Figure 15 (b) and Figure 15 (c) The diameter of each nozzle is 1 mm, and the total number of nozzles is 80.
[0070] Depend on Figure 12 The contour lines of Case 1 and the curves showing the change in detonation distance with the vertical support angle in Case 2 clearly demonstrate that as the angle increases, the detonation distance exhibits a pattern of first slightly increasing and then decreasing. The decrease is particularly pronounced between 6° and 8°. Previous theories have primarily considered the detonation distance of oblique detonation shock waves to be influenced by the temperature and pressure behind the oblique shock wave, as well as the equivalence ratio. Increased temperature and pressure after the oblique shock wave should shorten the detonation distance. Therefore, theoretically, increasing the support angle should gradually shorten the detonation distance, which aligns well with the simulation results for 8° and 10° supports. However, the 6° case appears to be an exception; increasing the angle does not lead to a decrease in the detonation distance, but rather a slight increase.
[0071] This invention proposes a vertically arranged support plate injection structure. First, it compares and analyzes the advantages of vertical support plates over horizontal support plates in stable initiation. Based on this, numerical simulations were performed on the mixing and initiation sections under different vertical support plate angles. The numerical simulation results show that increasing the vertical angle enhances hydrogen diffusion and mixing at the outlet of the mixing section, while also causing the hydrogen distribution structure to bend. For the initiation section, increasing the vertical support plate angle causes the initiation structure to tilt and shortens the initiation distance within a certain range.
[0072] The following conclusions can be drawn from summarizing the above patterns:
[0073] (1) The fuel distribution in the vertical direction is relatively uniform in the spatial structure of the detonation section, which can better achieve stable detonation.
[0074] (2) Increasing the angle of the support plate will enhance the diffusion and mixing of hydrogen in the central region of the flow field and cause the hydrogen distribution structure to bend, but it has little effect on the region near the wall.
[0075] (3) Increasing the angle of the vertical support plate will cause the detonation zone of the detonation section to tilt and the high-pressure zone to move to both sides. Increasing the angle has little effect on the temperature behind the oblique detonation shock wave.
[0076] (4) Within a certain accuracy range, as the angle of the vertical support plate increases, the detonation distance first increases slightly and then decreases rapidly.
[0077] The above description, in conjunction with specific preferred embodiments, provides a more detailed explanation of the present invention. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the scope of protection of the present invention.
Claims
1. A tilting detonation engine based on vertically distributed support plates, characterized in that, include: The air intake section is used to compress the supersonic incoming air; The mixing section is connected to the air intake section. A support plate perpendicular to the bottom of the mixing section is provided inside the section. The front end of the support plate is pointed. A fuel injection structure is formed by the support plate and the inner wall of the mixing section. The fuel injection structure is used to inject fuel. The initiation section, connected to the rear end of the mixing section, is used to compress the supersonic flow after mixing in the fuel injection structure, forming a slanted detonation shock wave during ignition and detonation.
2. The oblique detonation engine based on vertically distributed support plates as described in claim 1, characterized in that, The mixing section is meshed using a polyhedral mesh in unstructured processing.
3. The oblique detonation engine based on vertically distributed support plates as described in claim 1, characterized in that, The fuel injection structure includes two support plates arranged in parallel, with each support plate 27mm away from the sidewall of its nearest mixing section. ， Used to generate fuel distribution in the vertical direction.
4. The oblique detonation engine based on vertically distributed support plates as described in claim 3, characterized in that, Each of the support plates is 75mm long, and the distance from the pointed front end of the support plate to the inlet of the mixing section is 75mm, in order to provide sufficient inflow distance.
5. A tilting detonation engine based on vertically distributed support plates as described in claim 1, characterized in that, The mixing section has a total length of 573 mm, a width of 81 mm, and a height of 50 mm.
6. The oblique detonation engine based on vertically distributed support plates as described in claim 1, characterized in that, The detonation section is composed of a combination of cuboids and wedges.
7. A tilting detonation engine based on vertically distributed support plates as described in claim 6, characterized in that, The detonation section is 81mm long, 32.5mm wide, and 5mm high.
8. A tilting detonation engine based on vertically distributed support plates as described in claim 6, characterized in that, The cuboid of the detonation section is 5mm wide, the wedge-shaped part is 10mm high, and one wall of the wedge-shaped part has an inclination angle of 20°.
9. A tilting detonation engine based on vertically distributed support plates as described in claim 1, characterized in that, The mixing section is solved based on the Reynolds-averaged steady-state Navier-Stokes equations. The turbulence model adopts the k-ωSST two-equation turbulence model. In the simulation calculation, the AUSM+AUSM vector flux splitting scheme is used to capture the shock wave structure.
10. A tilting detonation engine based on vertically distributed support plates as described in claim 9, characterized in that, The wall surface of the mixing section is a non-slip constant temperature cold wall surface with a wall temperature of 300K.