Thermal jet ignition device of wide-range scramjet engine

Abstract

The invention discloses a thermal jet ignition device of a wide-area scramjet engine. The thermal jet ignition device comprises a premixing section, a combustion section and a jet section which are coaxially arranged and sequentially communicated. The premixing section comprises a main body, a spoiler and a rotational flow air channel; one end of the main body away from the combustion section is a fuel inlet; the spoiler is provided with a plurality of spoiler holes and is arranged in the main body in a manner of being perpendicular to the axial direction; the swirl gas channel is annularly arranged outside the main body of the premixing section and is communicated with the main body through at least three gas inlet channels, and the gas inlet channels are respectively tangent to the side wall of the main body and are positioned between the fuel inlet and the spoiler; gas enters the thermal jet ignition device through the self-spinning gas channel and then enters the main body through the gas inlet channel. A spark plug is arranged on the side wall of the combustion section, a center cone is arranged at the communication position of the premixing section and the combustion section, the section of the center cone is round, and the radius of the section of the center cone is gradually increased in the direction from the premixing section to the combustion section. The inner diameter of the jet flow section is smaller than that of the combustion section.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of engine ignition device, and particularly relates to a hot jet ignition device of a wide-range scramjet engine. BACKGROUND

[0002] The wide-range scramjet engine can operate in a dual-mode manner (subsonic combustion mode and supersonic combustion mode). Typical ignition technologies for the subsonic-super combustion mixed combustion mode and the pure supersonic combustion mode at a flight Mach number of Ma=4 or more include traditional high-energy igniter direct ignition, pioneer hydrogen ignition, and air throttling ignition. The high-energy spark ignition has the advantages of small size, simple structure, low energy consumption, reliable control, good repeatability, and relatively low cost. However, it is difficult to achieve reliable ignition at a low flight Mach number.

[0003] Under the condition of low Mach number flight (Ma<4), even if the kerosene is used for regenerative cooling, the heat absorption in the cooling channel is not much, and the kerosene is still injected in a liquid state into the combustion chamber. At this time, the total temperature of the incoming flow is lower than 1000K, and the liquid kerosene cannot be self-ignited. Moreover, the inlet velocity of the combustion chamber is much greater than the flame propagation velocity, and it is difficult to organize stable combustion; the low total temperature and total pressure of the incoming flow result in poor evaporation and mixing effect of the liquid hydrocarbon fuel, which is not conducive to ignition and flame propagation. SUMMARY

[0004] The purpose of the present application is to provide a hot jet ignition device of a wide-range scramjet engine, which still has good mixing effect, combustion efficiency and stability under low Mach number environment.

[0005] The technical solution of the present application is as follows:

[0006] A hot jet ignition device of a wide-range scramjet engine, comprising a premixing section, a combustion section and a jet section which are coaxially arranged and sequentially communicated;

[0007] The premixing section comprises a main body, a spoiler and a swirl air duct. The main body is provided with a fuel inlet at an end away from the combustion section. The spoiler is provided with a plurality of spoiler holes and is arranged vertically to the axial direction in the main body. The swirl air duct is annularly arranged outside the main body of the premixing section and is communicated with the main body through at least two center-symmetric air inlet channels. The air inlet channels are respectively tangent to the side walls of the main body and are located between the fuel inlet and the spoiler. The gas enters the hot jet ignition device from the swirl air duct and then enters the main body through the air inlet channels;

[0008] The side wall of the combustion section is provided with a spark plug, and the communication part between the premixing section and the combustion section is provided with a center cone. The cross section of the center cone is circular, and the cross section radius of the center cone gradually increases in the direction from the premixing section to the combustion section. The inner diameter of the jet section is smaller than that of the combustion section.

[0009] In some preferred embodiments, a conical transition section is formed between the combustion section and the jet section.

[0010] In some preferred embodiments, the angle between the conical transition section and the inner wall of the combustion section is 120°.

[0011] In some preferred embodiments, the blockage ratio of the central cone to the combustion zone is 65-70%.

[0012] In some preferred embodiments, the spoiler is circular, and the outer diameter of the spoiler is equal to the inner diameter of the premixing section.

[0013] In some preferred embodiments, the angle between the generatrix of the central cone and the bottom surface is 45-50°.

[0014] In some preferred embodiments, the central cone is a frustum.

[0015] In some preferred embodiments, the inner diameter ratio of the combustion section to the jet section is 10~12:4.

[0016] In some preferred embodiments, the inner diameter of the premixing section is larger than the inner diameter of the jet section but smaller than the inner diameter of the combustion section.

[0017] The present invention has at least the following beneficial effects:

[0018] 1. Gas enters the main body through the air inlet channel, and fuel enters the main body through the fuel inlet and mixes with the gas at the swirling point. In this application, by setting multiple air inlet channels tangent to the main body, the airflow generates a swirling flow after entering the main body, which can effectively improve the mixing effect of gas and fuel.

[0019] 2. A spoiler is installed behind the connection between the main body and the air intake channel, which can improve the fuel atomization effect and the mixing effect of gas and fuel, which is beneficial to the ignition process of the subsequent combustion stage.

[0020] 3. A central cone is installed at the connection between the premixing section and the combustion section. As the mixed gas and fuel flow through the central cone, their velocity increases, forming a low-velocity recirculation zone behind the cone. This low-velocity recirculation zone and the velocity-increased area together form a shear layer. In these regions, the shear layer improves fuel atomization and gas-fuel mixing; the low-velocity recirculation zone increases fuel residence time, thus improving combustion stability; and the high-speed airflow near the central cone prevents the flame from propagating back to the upstream premixing section, effectively preventing backfire and improving the safety and combustion stability of the device while reducing pollutants generated during combustion.

[0021] 4. The inner diameter of the jet section is smaller than that of the combustion section, which is beneficial for increasing the jet velocity. In some preferred embodiments, a conical transition section is formed between the jet section and the combustion section, which can reduce the energy loss caused by the sudden reduction in pipe diameter and further improve the jet velocity. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the hot jet ignition device provided in Example 1;

[0023] Figure 2 A front view of the hot jet ignition device provided in Example 1;

[0024] Figure 3 for Figure 2 A longitudinal sectional view;

[0025] Figure 4 This is a schematic diagram of the spoiler structure in Example 1;

[0026] Figure 5 A bottom view of the thermal jet ignition device provided in Example 1;

[0027] Figure 6 for Figure 5 A cross-sectional view perpendicular to the axis;

[0028] Figure 7 A schematic diagram showing the connection between the hot jet ignition device and the engine provided in Example 1;

[0029] Figure 8 This is a simulated working space for the hot jet ignition device provided in Example 1;

[0030] Figure 9 The simulation results are for the hot jet ignition process of the hot jet ignition device provided in Example 1 in the scramjet combustion chamber, where Ma=2.

[0031] The reference numerals in the figure are as follows: 1-Premixing section, 11-Main body, 111-Fuel inlet, 12-Break plate, 121-Break hole, 13-Swirl channel, 131-Intake channel, 132-Intake port, 2-Combustion section, 21-Center cone, 22-Spark plug, 23-Transition section, 3-Jet section, 31-Flame nozzle, 4-Combustion chamber. Detailed Implementation

[0032] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0033] 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 preferred embodiments of the present invention and should not be considered as excluding other embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0034] Unless otherwise expressly defined, in the claims, description, and accompanying drawings of this invention, the use of directional terms such as "top," "bottom," "inner," "outer," "upper," "lower," "front," and "rear" to indicate orientation or positional relationships is based on the orientation and positional relationships shown in the accompanying drawings and is only for the convenience of describing the invention and simplifying the description. It does not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the specific scope of protection of this invention. In this application, the end closest to the fuel inlet of the premixing section is designated as "front," and the opposite end as "rear" or "tail."

[0035] The gas mentioned in this invention is at least partially a flammable gas (combustion oxidizer or gaseous fuel), which, when mixed with fuel (fuel oil or gaseous fuel), forms a mixed fuel. The specific composition of the gas can be formulated and adjusted by those skilled in the art according to actual conditions.

[0036] Example 1

[0037] This embodiment provides a hot jet ignition device for a wide-range scramjet engine, such as... Figures 1-6 As shown, it mainly includes a premixing section 1, a combustion section 2, and a jet section 3 that are coaxially arranged and connected in sequence.

[0038] The premixing section 1 includes a main body 11, a spoiler 12, and a swirling air passage 13. The port of the main body 11 furthest from the jet section 3 is the fuel inlet 111, which is connected to the fuel injector. The fuel injector injects fuel into the premixing section 1 through the fuel inlet 111. Figure 3 and Figure 4 As shown, the outer part of the spoiler 12 is a ring that fits the inner diameter of the main body 11, while the inner part is a grid formed by three horizontal and three vertical cylindrical rods with a diameter of 1 mm, with 4*4 turbulence holes 121 on the grid. In this embodiment, the spoiler 12 is arranged perpendicularly to the axial direction inside the main body 11, and the spoiler 12 is bolted to the main body 11. The spoiler 12 can "break up" the mixture of fuel and gas, thereby effectively improving the physicochemical effect of the fuel and the mixing effect of fuel and gas. In this embodiment, the outer diameter of the main body 11 of the premixing section 1 is 20 mm, and the inner diameter is 16 mm.

[0039] See Figure 5 and Figure 6The swirling air passage 13 is arranged around the main body 11 of the premixing section 1 and is connected to the main body 11 through four air intake channels 131. The air intake channels 131 are located between the fuel inlet 111 and the baffle 12. The four air intake channels 131 are symmetrically arranged along the axis center. Each air intake channel 131 is tangent to the side wall of the main body 11. Gas enters through the air inlet 132 of the swirling air passage 13, and then enters the main body 11 after passing through the swirling air passage 13 and the air intake channels 131, and generates swirling flow. This arrangement can effectively improve the mixing effect of gas and fuel.

[0040] A central cone 21 is provided at the connection between the premixing section 1 and the combustion section 2. The cross-section of the central cone 21 perpendicular to the axial direction is circular, and the radius of the cross-section of the central cone 21 gradually increases along the direction from the premixing section 1 to the combustion section 2. In this embodiment, the outer diameter of the combustion section 2 is 30 mm and the inner diameter is 22 mm; the central cone 21 is frustum-shaped, with a top circle diameter of 2 mm, a bottom circle diameter of 18 mm, and a height of 9 mm. The blockage ratio of the central cone 21 to the combustion section 2 is approximately 67%. When the mixed gas and fuel flow through the central cone 21, the flow velocity increases, and a low-velocity recirculation zone is formed behind the central cone 21. A shear layer is formed between the low-velocity recirculation zone and the area where the flow velocity increases. In the aforementioned regions, the shear layer can improve the fuel atomization effect and the mixing effect of gas and fuel; the low-speed recirculation zone can increase the fuel residence time, thereby improving the combustion stability; and the high-speed airflow near the central cone 21 can prevent the flame of combustion section 2 from propagating back to the upstream premixing section 1, effectively preventing backfire, improving the safety of the device, combustion stability, and reducing pollutants generated during the combustion process.

[0041] A spark plug 22 is installed on the side wall of the combustion section 2, and a flame nozzle 31 is located at the tail end of the jet section 3. After the spark plug 22 ignites the mixed gas and fuel, the resulting flame forms a jet that is ejected from the flame nozzle 31. In this embodiment, the outer diameter of the jet section 3 is 16 mm, and the inner diameter is 8 mm. The inner diameter of the jet section 3 is smaller than the inner diameters of the combustion section 2 and the premixing section 1, which can increase the jet velocity of the jet section 3. Furthermore, a conical transition section 23 is formed between the jet section 3 and the combustion section 2, and the angle between the conical transition section 23 and the inner wall of the combustion section 2 is 120°, which can reduce the energy loss caused by the sudden reduction in pipe diameter and increase the jet velocity.

[0042] like Figure 7 As shown, the flame nozzle 31 is connected to the combustion chamber 4 of the wide-range scramjet engine, providing the combustion chamber 4 with a high-temperature, high-speed jet flame, thereby achieving in-situ replacement of the high-energy electric spark igniter.

[0043] The working principle of the hot jet ignition device is explained below:

[0044] Fuel enters the main body 11 of the premixing section 1 axially from the fuel inlet 111. Gas enters the device through the inlet of the swirling air passage 13, flows through the swirling air passage 13 and the inlet passage 131, and forms a swirling flow at the main body 11, then mixes with the fuel to form a mixed fuel. After further mixing by the baffle 12, the mixed fuel flows through the central cone 21 and enters the combustion section 2. In this step, the mixed fuel first passes rapidly through the central cone 21, and then forms a low-speed recirculation zone behind the central cone 21. The spark plug 22 ignites the mixed fuel to produce a flame, which rapidly propagates to the area with a high concentration of mixed fuel until it fills the entire combustion section 2. While the initial ignition core energy is dissipated, it can propagate to the low-speed recirculation zone and form a high-temperature, high-turbulence core in the low-speed recirculation zone, ultimately achieving successful ignition. The flame passes through the jet section 3 and is ejected from the flame nozzle 31, forming a high-temperature, high-speed jet flame.

[0045] The effective working space of the igniter was obtained using numerical simulation with Fluent 2024R2, where oxygen enters the device via the swirl-flow inlet 13 and ethylene enters the device via the fuel inlet. The simulation results are as follows: Figure 8 As shown, the hot jet ignition device has a wide operating range, with oxygen flow rates ranging from a minimum of 10 g / s to a maximum of 80 g / s, and ethylene flow rates ranging from a minimum of 4 g / s to a maximum of 10 g / s. The effective equivalence ratio ranges from 0.3 to 1.3, with oxygen-enriched operation being the primary mode.

[0046] Under simulated conditions of Ma=2, this hot jet ignition device was used for combustion chamber ignition in a scramjet engine, and the results are as follows: Figure 9 As shown, the hot jet ignition device can generate recombination energy to ignite the scramjet engine within 950 μs, indicating that the device can achieve reliable ignition under low flight Mach number (Ma<3.5) incoming flow conditions.

[0047] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A hot jet ignition device for a wide-range scramjet engine, characterized in that, It includes a premixing section, a combustion section, and a jet section that are coaxially arranged and connected in sequence; The premixing section includes a main body, a baffle plate, and a swirling air passage; the end of the main body away from the combustion section is a fuel inlet; the baffle plate has several interference flow holes and is arranged perpendicularly to the axial direction within the main body; the swirling air passage is arranged around the main body of the premixing section and communicates with the main body through at least two centrally symmetrically arranged air intake channels, the air intake channels being tangent to the side walls of the main body and located between the fuel inlet and the baffle plate; gas enters the hot jet ignition device from the swirling air passage and then enters the main body through the air intake channels; A spark plug is provided on the side wall of the combustion section, and a central cone is provided at the connection between the premixing section and the combustion section. The cross-section of the central cone is circular, and the radius of the cross-section of the central cone gradually increases along the direction from the premixing section to the combustion section. The inner diameter of the jet section is smaller than the inner diameter of the combustion section.

2. The hot jet ignition device as described in claim 1, characterized in that, A conical transition section is formed between the combustion section and the jet section.

3. The hot jet ignition device as described in claim 1, characterized in that, The angle between the conical transition section and the inner wall of the combustion section is 120°.

4. The hot jet ignition device as described in claim 1, characterized in that, The blockage ratio between the central cone and the combustion section is 65-70%.

5. The hot jet ignition device as described in claim 1, characterized in that, The spoiler is circular, and its outer diameter is equal to the inner diameter of the premixing section.

6. The hot jet ignition device as described in claim 1, characterized in that, The angle between the generatrix of the central cone and the bottom surface is 45~50°.

7. The hot jet ignition device as described in claim 6, characterized in that, The central cone is a frustum.

8. The hot jet ignition device as described in claim 1, characterized in that, The ratio of the inner diameter of the combustion section to that of the jet section is 10~12:

4.

9. The hot jet ignition device as described in claim 1, characterized in that, The inner diameter of the premixing section is larger than the inner diameter of the jet section but smaller than the inner diameter of the combustion section.

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