An experimental device for an oblique detonation engine combustion chamber with variable wedge angle and starting point

Abstract

The present invention discloses an oblique detonation engine combustion chamber experimental device with variable oblique wedge angle and starting point, comprising a front connecting part, a rear connecting part, and a combustion chamber arranged between the front connecting part and the rear connecting part; the combustion chamber is processed with an oblique wedge, and the oblique wedge angle and starting point position can be adjusted according to the pressure, temperature, equivalence ratio and mixing uniformity of the incoming combustible gas; fuel injection holes are distributed on the surface of the oblique wedge, and fuel can be injected into the rear area of ​​the oblique detonation wave front to change the wave system structure in the combustion chamber or the thrust of the oblique detonation engine; the left wall surface and the right wall surface of the combustion chamber are installed with observation windows to observe the initiation and stationary process of the oblique detonation wave in the test.

Description

Technical Field

[0001] The invention belongs to the field of scramjet engine combustion chambers, in particular to an oblique detonation engine combustion chamber experimental device with variable oblique wedge angles and starting points. Background Art

[0002] Scramjets are currently the most effective propulsion system for aircraft achieving hypersonic flight within the atmosphere. They consist of an inlet, a combustion chamber, and a single-sided expansion nozzle. The inlet, through its converging walls, generates shock waves that decelerate and pressurize the hypersonic air to a state suitable for combustion. The air then mixes with fuel in the combustion chamber, burning to release heat and transforming it into high-temperature, high-pressure gas that expands through the nozzle to generate thrust. High-performance propulsion technology based on scramjets is a key technology for achieving hypersonic propulsion. Conventional scramjets employ deflagration combustion, which approximates an isobaric cycle, as a combustion mechanism. However, currently, optimizing the combustion chamber configuration and fuel mixing alone has proven difficult to significantly increase engine thrust. However, adopting detonation combustion, which approximates a constant-volume cycle, as a combustion mechanism could theoretically increase scramjets' thrust performance by 30%. Therefore, detonation combustion, as a more efficient combustion mechanism, holds great promise for optimizing scramjets' thrust performance.

[0003] In an oblique detonation ramjet, combustible gas flows through an oblique wedge, inducing an oblique shock wave, which in turn triggers an oblique detonation. Under suitable flow conditions and slope angles, the oblique detonation wave can become lodged on the slope surface after initiation, and chemical reactions occur near the oblique detonation wave, completing within microseconds. The high-temperature fuel then expands and is discharged through the nozzle, generating thrust. In addition to its advantages in combustion cycle efficiency, oblique detonation-driven scramjets also boast shorter, lighter, and simpler engines due to the smaller detonation reaction zone. Furthermore, oblique detonation as a propulsion method can achieve lower specific fuel consumption at high Mach numbers, further enhancing engine performance.

[0004] The successful initiation and stationary of oblique detonation waves are essential for the proper operation of oblique detonation engines. The initiation of oblique detonation waves is closely related to the angle and starting point of the oblique wedge. Currently, the mechanisms of initiation and stationary of oblique detonation waves in a real oblique detonation engine combustion chamber with wall constraints remain unclear. Therefore, to advance the engineering application of oblique detonation engines, it is particularly important to conduct multi-condition testing of oblique detonation engine combustion chambers in conjunction with supersonic shock tunnels. Summary of the Invention

[0005] The purpose of the present invention is to provide an oblique detonation engine combustion chamber experimental device with variable oblique wedge angle and starting point, so as to achieve matching of the combustion chamber oblique wedge angle and starting point position with the incoming flow conditions, thereby detonating the oblique detonation wave and making it stably stationed in the combustion chamber, and a fuel replenishing hole is provided on the combustion chamber oblique wedge to achieve increased detonation probability, changed wave system structure, and afterburner combustion during the experiment.

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

[0007] An oblique detonation engine experimental device with variable wedge angle and starting point includes a front connecting portion, a rear connecting portion, and a combustion chamber disposed between the front connecting portion and the rear connecting portion. The lower wall of the combustion chamber is a detachable structure to replace the lower wall of the combustion chamber with different specifications, that is, different wedge angles and wedge starting points.

[0008] The lower wall of the combustion chamber is provided with an oblique wedge, which is used to adjust the angle according to the incoming flow conditions to ensure that the oblique detonation wave can be detonated, and adjust the position of the oblique wedge according to the heat release conditions of the combustion chamber to ensure that the oblique detonation wave is stably stationed: a suitable oblique wedge angle is selected to induce a sufficiently strong leading oblique shock, so that the leading oblique shock wave and the compression wave generated by the shock wave-induced combustion produce a mutual reinforcement effect, and finally the oblique shock wave and the combustion wave are coupled to form an oblique detonation wave; a suitable oblique wedge position is selected to form a flow channel area of ​​appropriate size with the upper wall of the combustion chamber, so that the oblique detonation wave after detonation will not be thermally congested due to the excessively fast heat release efficiency of the chemical reaction, thereby propagating upstream.

[0009] The inclined wedge is provided with a fuel replenishing hole for replenishing fuel into the combustion zone of shock wave induced combustion or the chemical reaction zone behind the wavefront of the oblique detonation wave, thereby increasing the fuel mass fraction in the combustion zone, increasing the intensity of the combustion wave, and improving the probability of the transition from shock wave induced combustion to detonation; increasing the combustion mass fraction in the chemical reaction zone and utilizing the high temperature and high pressure characteristics of the chemical reaction zone can achieve rapid combustion of the fuel, thereby increasing the thrust of the combustion chamber.

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

[0011] (1) The present invention is applied to a super-enthalpy shock wave wind tunnel test platform, and successfully realizes the initiation of oblique detonation waves by the incoming mixed gas on the oblique wedge and the stable stationing of the oblique detonation waves, verifying the feasibility of applying the oblique detonation ramjet engine to the ultra-high-speed propulsion system.

[0012] (2) Under the condition of a small equivalence ratio, the oblique detonation wave may not be able to detonate and settle on the oblique wedge, while under the condition of a large equivalence ratio, the oblique detonation wave may detonate and propagate upstream. By replenishing fuel through the fuel replenishing hole on the oblique wedge, the present invention can explore the feasibility of replenishing fuel behind the wavefront for the transition from shock wave-induced combustion to detonation, and can also change the wave system structure of the oblique detonation wave and study the influence of the changing equivalence ratio on the settling characteristics and wave system structure of the oblique detonation wave. For a stably settled oblique detonation wave, the fuel replenishing hole can be used to replenish fuel behind its wavefront, and the thrust can also be changed to achieve afterburning combustion of the oblique detonation engine.

[0013] (3) The present invention realizes the adjustment of the angle and position of the oblique wedge, which can explore and summarize the matching relationship between the oblique wedge angle and the engine throat area and the incoming flow conditions during the operation of the oblique detonation engine, that is, during the initiation and stationary process of the oblique detonation wave, and provide a certain reference for the engineering application of the oblique detonation engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 (a) is a cross-sectional view of an oblique detonation engine combustion chamber assembly with variable wedge angle and position according to the present invention.

[0015] Figure 1 (b) is a schematic diagram of the installation of the fuel supply device of the present invention and the lower wall of the combustion chamber.

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

[0017] Figure 3 It is a cross-sectional view of the front flange of the present invention.

[0018] Figure 4 This is the front flange front view of the present invention.

[0019] Figure 5 A top view of the upper wall of the combustion chamber of the present invention

[0020] Figure 6 It is a bottom view of the assembly of the present invention.

[0021] Figure 7 It is a front view of the right wall of the combustion chamber of the present invention.

[0022] Figure 8 This is an isometric view of the combustion chamber observation window cover of the present invention.

[0023] Figure 9 This is an isometric view of the square glass of the combustion chamber observation window of the present invention.

[0024] Figure 10 This is a cross-sectional view of the observation window assembly of the present invention.

[0025] Figure 11It is a cross-sectional view of the lower wall of the present invention.

[0026] Figure 12 It is the isometric drawing of the lower wall of the present invention.

[0027] Figure 13 This is a cross-sectional view of the rear flange of the present invention.

[0028] Figure 14 This is the front view of the rear flange of the present invention.

[0029] Figure 15 This is a cross-sectional view of the fuel supply device of the present invention.

[0030] Figure 16 (a) Experimental schlieren photograph using α = 25°, x = 28 mm wedge and ER = 0.32

[0031] Figure 16 (b) Experimental Schlieren photo with α = 25°, x = 28 mm wedge and ER = 0.52

[0032] Figure 16 (c) Experimental Schlieren photo with α = 25°, x = 28 mm wedge and ER = 0.46 + 0.06

[0033] Figure 16 (d) Experimental schlieren photograph using α = 20°, x = 28 mm wedge and ER = 0.52 DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0035] like Figure 1-5 As shown, a test device for an oblique detonation engine combustion chamber with a variable oblique wedge angle and starting point includes a front flange 1, a front welding block 2, an upper wall 3 of the combustion chamber, a left wall 4 of the combustion chamber, a right wall 5 of the combustion chamber, a lower wall 6 of the combustion chamber, an observation window cover 7, a rear welding block 8, a rear flange 9, a square glass for the observation window 10, and a fuel supply device 11, which are connected in sequence along the flow direction of the combustible mixture. The total length of the combustion chamber is 217 mm, and the lower wall 6 and the upper wall 3 of the combustion chamber form a contraction flow channel 3-2 with a flow channel height of 56 mm and a flow channel height of 120 mm.

[0036] like Figure 1, the front welding block 2, the combustion chamber upper wall 3, the combustion chamber left wall 4, the combustion chamber right wall 5, and the rear welding block 8 are first connected together by welding, and the welded whole is then welded to the front flange 1 and the rear flange 9. The front welding block 2, the combustion chamber upper wall 3, the combustion chamber left wall 4, the combustion chamber right wall 5, and the combustion chamber lower wall 6 together constitute the combustion chamber flow channel, and the combustible mixture flows through the flow channel. Under the action of the flow channel profile that contracts along the flow direction, the oblique detonation wave detonates and settles. After the oblique detonation wave detonates, the pressures before and after the wave front can be measured by the pressure sensors installed in the pressure measuring holes 3-1 and the pressure measuring holes 6-1-2. The multiple pressure measuring holes 3-1 are evenly distributed along the flow direction of the combustible mixture, and the pressure measuring hole spacing is 20 mm. In particular, the distribution spacing of the pressure measuring holes 3-1 on the combustion chamber upper wall 3 in the present invention is not limited to Figure 5 shown.

[0037] like Figure 3-4 As shown, in this embodiment, a convex step surface is processed on the front of the front flange 1 to ensure airtightness when connected to the rear flange of the mixing test section. The front flange has 12 through holes for bolt connection evenly distributed along the circumference, and the through hole diameter is The two through holes located on the symmetrical midline of the lower end of the front flange are countersunk with a depth of 15 mm, which are used to place the screw heads when bolting to avoid interference between the bolts and the lower wall 6 of the combustion chamber.

[0038] like Figure 6 As shown, in this embodiment, threaded holes are processed at the bottom of the front welding block 2, the left wall 4 of the combustion chamber, the right wall 5 of the combustion chamber, and the rear welding block 7. The size of the threaded holes is M6×8mm, which is used to connect with the lower wall 6 of the combustion chamber by screws.

[0039] like Figure 7-10 As shown, this embodiment has a stepped hole 5-2 processed on the right wall surface, and a sealing groove is processed on the stepped surface of the stepped hole 5-2 to ensure airtightness when installing the observation window 10. In this embodiment, the square glass of the observation window is made of quartz glass to ensure high temperature tolerance. The observation field size is 88mm×60mm. The observation window glass, the observation window cover and the side wall surface are matched as shown in FIG. Figure 10 As shown, the observation window cover 7 is uniformly distributed with through holes 7-1 along the circumference, and the size of the through holes is Used to connect with the threaded hole 5-3-1 of the side wall boss 5-3. In this embodiment, the left wall size is exactly the same as the right wall, and the left wall screw hole 4-1, stepped hole 4-2, boss 4-3 and its threaded hole 4-3-1 are all on the same side. Figure 10 The position mirrored by plane B.

[0040] like Figure 11-12As shown, in this embodiment, an inclined wedge 6-1 is machined on the top of the lower wall 6 of the combustion chamber. The angle of the inclined wedge is α, 20°≤α≤30°, and the horizontal section of the inclined wedge 6-1 is x, 18mm≤x≤43mm. The angle and position of the inclined wedge can be adjusted according to the experimental working conditions. There are 5 pressure sensor mounting holes machined at the bottom of the lower wall. The pressure measuring hole 6-1-3 is connected to the flow channel 3-2, and the size of the pressure measuring hole 6-1-3 is In particular, the distribution of the pressure measuring holes on the lower wall 6 of the combustion chamber in the present invention is not limited to Figure 7 In this embodiment, through holes 6-2 are processed along the circumference of the lower wall surface 6 of the combustion chamber. The number of through holes is 22 and the size of the through holes is Used to connect the combustion chamber lower wall 6 and other combustion chamber walls by screws. In this embodiment, a sealing groove is machined around the inclined wedge 6-1 to place a sealing rubber ring, thereby ensuring the airtightness when the combustion chamber lower wall 6 is connected to the other combustion chamber walls. In this embodiment, multiple fuel supply holes 6-1-2-1 are machined above the fuel supply groove 6-1-2, connecting to the flow channel 3-2. There are 6 supply holes, arranged perpendicular to the air flow direction, with a hole spacing of 16mm and a hole size of In particular, the number and diameter of the fuel supply holes in the present invention are not limited to Figure 12 shown.

[0041] like Figure 13-14 As shown, the rear of the rear flange 9 of this embodiment is processed with a concave step surface, and a sealing groove is processed in the concave step surface for placing a sealing rubber ring, thereby ensuring airtightness when connected to the front flange of the vacuum tank. The rear flange 9 has 12 through holes for bolt connection evenly distributed along the circumference, and the through hole diameter is The two through holes located on the symmetrical midline of the lower end of the front flange are countersunk with a depth of 15 mm, which are used to place the screw heads when bolting to avoid interference between the bolts and the lower wall 6 of the combustion chamber.

[0042] like Figure 15 As shown, the fuel supply device 11 of this embodiment includes a fuel supply groove pressure plate 11-1 and a fuel supply pipeline 11-2. The fuel supply groove pressure plate 11-1 is welded to the lower end of the fuel supply groove 6-1-2 of the inclined wedge 6-1 on the lower wall of the combustion chamber to form a sealed cavity structure. A trapezoidal through hole 11-1-1 is machined in the middle of the fuel supply groove pressure plate. The small hole diameter is The diameter of the large hole is The fuel supply pipeline 11-2 is welded below the trapezoidal through hole 11-1-1 of the fuel supply tank pressure plate 11-1 and is coaxial with the trapezoidal through hole 11-1-1. The inner diameter of the fuel supply pipeline 11-2 is An adapter is welded to the lower end of the fuel supply pipeline 11-2 for connecting to the fuel supply bottle.

[0043] The combustion chamber is machined with an inclined wedge to compress the incoming combustible gas to produce a leading oblique shock wave. The gas behind the leading oblique shock wave burns, and the compression wave generated by the combustion strengthens the leading oblique shock wave. The increased intensity of the leading oblique shock wave in turn intensifies the gas combustion. The leading oblique shock wave and the compression wave generated by the combustion mutually reinforce each other, ultimately coupling the oblique shock wave and the combustion wave to form an oblique detonation wave. The angle and starting point of the inclined wedge can be adjusted according to the pressure, temperature, equivalence ratio, and mixing uniformity of the incoming combustible gas. Fuel injection holes are distributed on the surface of the inclined wedge, which can inject fuel into the area behind the oblique detonation wave front to change the wave system structure in the combustion chamber or the thrust of the oblique detonation engine. Observation windows are installed on the left and right walls of the combustion chamber to observe the initiation and stationary process of the oblique detonation wave during the test.

[0044] Figure 16 The flow and combustion conditions in the flow channel of this embodiment were photographed during the test. Figure 16 (a) to Figure 16 In (c), the wedge α = 25°, x = 28 mm, Figure 16 In (d), the wedge α = 20°, x = 28 mm, as shown in Figure 16 As shown in (a), the equivalence ratio of the incoming mixture is ER=0.32. A clear oblique detonation wave structure was captured in the experiment. In the figure, ODW (Oblique Detonation Engine) represents the oblique detonation wave. During the stable working period of the super-enthalpy shock tunnel, the present invention achieved the successful initiation of the oblique detonation wave and its stable stationing on the oblique wedge; Figure 16 As shown in (b), the equivalence ratio of the incoming mixture is increased to ER = 0.52. During the test, the ODW and the large-scale flow separation area are captured. During the test, due to the increase in the equivalence ratio, the ODW oscillates. Figure 16 (c) The equivalence ratio of the incoming mixture is ER = 0.46, and the equivalence ratio of the fuel added through the lower wall injection hole 6-1-2-1 is ER = 0.06. The total equivalence ratio is Figure 16 (b) The equivalent ratio of the working condition is consistent, compared Figure 16 (b) It can be seen that the structure of the oblique detonation wave system has changed, and the large-scale flow separation zone has disappeared; Figure 16 As shown in (d), in the test, the inflow mixture with ER = 0.52 and the 20° wedge only showed the phenomenon of shock wave induced combustion. Figure 16 The working conditions of (b) illustrate the significant impact of the angle of the wedge on the difficulty of initiating oblique detonation waves. The present invention achieves visual testing of the initiation and stationary state of oblique detonation waves under multiple working conditions and successfully matches the incoming flow conditions with the geometric configuration of the combustion chamber wedge.

Claims

1. An experimental device for an oblique detonation engine combustion chamber with a variable wedge angle and starting point, comprising a front connecting portion for connecting to a mixing section, a rear connecting portion for connecting to a vacuum tank, and a combustion chamber disposed between the front connecting portion and the rear connecting portion and having a convergent-divergent flow passage therein; characterized in that: Also included is a fuel supply device for replenishing fuel to the combustion chamber; The lower wall of the combustion chamber is a detachable structure, which can be replaced with different specifications of the lower wall of the combustion chamber, that is, different wedge angles and positions; An inclined wedge is provided on the lower wall of the combustion chamber for adjusting the angle according to the incoming flow to ensure that the oblique detonation wave can be detonated; A horizontal adjustment section is provided in front of the oblique wedge to adjust the position of the oblique wedge and the minimum flow area of ​​the combustion chamber throat to determine the effect of thermal congestion on the initiation and stationary of the oblique detonation shock wave; The oblique wedge is provided with a plurality of fuel supply holes arranged perpendicular to the airflow direction, which are used to replenish fuel under the working condition where only shock wave induced combustion is achieved but oblique detonation wave initiation does not occur, so as to increase the probability of oblique detonation wave initiation; fuel is replenished under the working condition where oblique detonation wave initiation occurs to change the oblique detonation wave system structure; for the oblique detonation wave that is stably stationary, it is also used to change the thrust to achieve afterburning combustion of the oblique detonation engine; The fuel supply device includes a fuel supply tank pressure plate and a fuel supply pipeline; The fuel supply groove pressure plate is fixed to the lower end of the fuel supply groove on the lower wall of the combustion chamber to form a sealed cavity structure; A through hole is provided in the middle of the fuel supply tank pressure plate; The fuel supply pipeline is fixed below the through hole of the fuel supply tank pressure plate and is coaxial with the through hole; The wedge angle is a , 20°≤ a ≤30°, the length of the horizontal adjustment section is x, 18mm≤x≤43mm.

2. The oblique detonation engine combustion chamber experimental device with variable wedge angle and starting point according to claim 1 is characterized in that: There are multiple pressure measuring holes on the upper wall and the lower wall of the combustion chamber, which are used to detect whether detonation occurs in the combustion chamber; and the pressure measuring holes on the lower wall of the combustion chamber are also used to detect whether stagnation occurs in the combustion chamber.

3. The oblique detonation engine combustion chamber experimental device with variable wedge angle and starting point according to claim 1 is characterized in that: Observation windows are provided on the left wall and the right wall of the combustion chamber.

4. The oblique detonation engine combustion chamber experimental device with variable wedge angle and starting point according to claim 1, characterized in that: Both the front connecting part and the rear connecting part are provided with concave step surfaces, and sealing grooves are processed in the concave step surfaces for placing sealing rubber rings.

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