A flameholder for use in combination with ramjet flowpath ignition

Abstract

The application discloses a kind of for combination engine ram flow passage ignition flame stabilizer, comprising: flame stabilizer body, flame stabilizer body is columnar body, and is axially opened with a two-end open prechamber along its axis;Multiple secondary flow channels are arranged on the flame stabilizer body and are spaced around the prechamber, each secondary flow channel is axially through the flame stabilizer body, the straight line segment of the front part is parallel to the axis, the straight line segment of the rear part is inclined to the axis side from front to back, the number of secondary flow channels is even, the included angle of adjacent two secondary flow channels with the axis is not the same;Fuel or oxidant is used in each secondary flow channel to flow into it from the front end, and is injected into different positions in the ram flow channel from the rear end, and the fuel gas at the rear end of the prechamber realizes different position rich or oxygen-rich secondary combustion. By using the flame stabilizer, low mixing ratio combustion is arranged in the prechamber, which avoids the adiabatic combustion temperature being too high and reduces the requirement for material heat resistance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of engine, and particularly relates to a flame stabilizing device for ramjet flow channel ignition of combined engine. BACKGROUND

[0002] Rocket ramjet combined engine integrating the advantages of rocket engine and ramjet engine is one of the most promising high supersonic vehicle power devices, which has the advantages of reducing the launch cost of spacecraft or realizing horizontal take-off and landing of high supersonic vehicle. It is difficult for high Mach number air flow in the flow channel of a scramjet engine to ensure reliable ignition and stable combustion in a short time. In order to solve the above problems, a variety of solutions have been successfully applied, mainly including reducing the flow velocity and high-energy guided ignition. The latter is commonly a hot jet, and the design of the hot jet igniter can be independent of the ramjet engine and is convenient for repeated ignition, which has great application advantages. At present, many scholars in China have proved the feasibility of hot jet ignition by using experimental simulation and other methods, and have studied the ignition and flame stabilization effects of different ignition fuels. However, since the physical property parameters of the ramjet engine air flow will change with factors such as flight altitude and cruising speed, the ignition and flame stabilization device needs to have the functions of adjusting the oxygen-fuel ratio and the external heat release length according to different flow conditions. The tail end heat release length of the traditional hot jet auxiliary ignition device is limited, and it does not have the function of adjusting the heat release length, which cannot meet the adjustment requirements of the change of air flow conditions. In addition, single-stage combustion in the jet device will cause the fuel temperature to be too high, which cannot work for a long time, and has high requirements for the heat resistance of the material. SUMMARY

[0003] The purpose of the present application is to provide a flame stabilizing device for ramjet flow channel ignition of combined engine, which sets up low-mixing-ratio combustion in the pre-chamber to avoid high adiabatic combustion temperature, reduce the requirement for material heat resistance, and increase the working time limit of the flame stabilizing device.

[0004] The present application adopts the following technical scheme: a flame stabilizing device for ramjet flow channel ignition of combined engine, which is coaxially placed in the combustion chamber ramjet flow channel, comprising: a flame stabilizing device body, which is a columnar body, and a pre-chamber with two open ends in front and back is axially arranged on the central axis of the columnar body;

[0005] A plurality of secondary flow channels are arranged on the flame stabilizing device body and around the pre-chamber at intervals, each secondary flow channel penetrates the flame stabilizing device body axially, is composed of two straight segments connected in front and back, the straight segment in front is parallel to the axis, and the straight segment in back is inclined to the axis from front to back, forming an acute angle with the axis, the number of secondary flow channels is even, and the included angles of adjacent two secondary flow channels with the axis are different;

[0006] Different positions of the secondary flow channels for fuel or oxidant flowing into the channels from the front end and jetting into the combustion chamber ram flow channel, and the different positions of the secondary combustion of the fuel gas from the rear end outlet of the pre-chamber.

[0007] Further, the four secondary flow channels are divided into two groups, and the two secondary flow channels in each group are spaced apart; the angle between the straight line segment at the rear of each secondary flow channel and the axis of the ram flow channel is less than 5°; and the two groups of secondary flow channels are used to inject fuel or oxidant into two different positions of the ram flow channel at the rear of the pre-chamber.

[0008] Further, in the two groups of secondary flow channels, the angle between the straight line segment at the rear of each secondary flow channel and the axis of the ram flow channel is 3.6° and 1.5°.

[0009] Further, the shape of the opening at the front end of the pre-chamber is that of two annular channels coaxially sleeved together, wherein the outer annular channel is a fuel nozzle, and the inner annular channel is an oxidant nozzle, each nozzle is used to inject corresponding fuel or oxidant into the pre-chamber, and the fuel and oxidant are combusted in the pre-chamber.

[0010] The beneficial effects of the present application are: 1. Multiple secondary flow channels are added to achieve afterburning in the ram flow channel, extend the heat release distance, the secondary flow channels have two different angles with the overall axis of the engine, each accounting for half of the total number of flow channels, and different lengths of high-temperature plume are formed externally; when supplying oxidant to the secondary flow channel, high-temperature gas can be provided, and when supplying fuel, mixed combustion can be formed, and at the same time, external blowing agents can be blown to ensure the safety of the working environment when changing the medium. 2. The angle between the secondary flow channel and the overall axis of the engine can be set as needed to change the position of the secondary fuel or oxidant injection into the ram flow channel to obtain different lengths of heat release area, achieving the adjustment function of heat release length. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a front view and a left view of a flame stabilizing device;

[0012] Figure 2 is a schematic diagram of the flame length of a jet flame stabilizing device;

[0013] Figure 3 is a temperature cloud diagram of the working simulation of a flame stabilizing device

[0014] Wherein: 1. fuel nozzle; 2. oxidant nozzle; 3. secondary flow channel. DETAILED DESCRIPTION

[0015] The present application will be described in detail below in conjunction with the drawings and specific embodiments.

[0016] The present application is a kind of for combined engine ram flow channel ignition flame stabilizing device, as shown inFigure 1 As shown, for coaxial placement in the combustion chamber ram flow channel, comprising: a flame holder body, the flame holder body is a columnar body, along the axis of a front and rear open pre-chamber.

[0017] On the flame holder body, and around the pre-chamber is provided with a plurality of secondary flow channels 3, each secondary flow channel 3 is axially through the flame holder body, composed of two straight segments connected front and rear, the front straight segment is parallel to the axis, the rear straight segment is inclined to the axis from front to back, and the angle between the axis and the rear straight segment is an acute angle, the number of secondary flow channels 3 is even, the angle between the adjacent two secondary flow channels 3 and the axis is not the same.

[0018] Each secondary flow channel 3 is used for fuel or oxidant to flow into it from the front end, and to be injected into the combustion chamber ram flow channel at different positions from the rear end, and the fuel gas from the rear end of the pre-chamber realizes different position rich or oxygen-rich secondary combustion.

[0019] The above-mentioned secondary flow channel 3 is preferably four, two by two into a group, and the interval of two secondary flow channels 3 is a group; and the angle between the rear straight segment of the four secondary flow channels 3 and the axis of the ram flow channel is less than 5°. In each group of secondary flow channels 3, the angle between the rear straight segment of the secondary flow channel 3 and the axis of the ram flow channel is 3.6° and 1.5°, and the angle can be changed according to the required heat release length.

[0020] The above-mentioned pre-chamber front end opening shape is: two coaxially sleeved annular channels, wherein: the outer annular channel is a fuel nozzle 1, and the inner annular channel is an oxidant nozzle 2, each nozzle is used to inject corresponding fuel or oxidant into the pre-chamber, and the fuel and oxidant are burned in the pre-chamber. The coaxial nozzle structure is simple, and the contact area of the fuel and the oxidant is large.

[0021] The above-mentioned flame holder adopts GH3128 nickel-based alloy material, which can work for a long time at about 1000K. When the flame holder works, the oxidant and the fuel enter the pre-chamber coaxially from the oxidant nozzle 2 and the fuel nozzle 1 at a low mixing ratio, at the same time, the secondary fuel, such as methane fuel, will flow into the secondary flow channel 3 from the front end, and be injected into the ram flow channel from the rear end. Because the angle between the rear straight segment of the secondary flow channel 3 and the axis is different, such as the angle between the axis of the first secondary flow channel and the second secondary flow channel and the axis of the flame holder is 3.6° and 1.5° respectively, the secondary fuel injected from the rear end will be sprayed to different combustion positions in the ram flow channel. According to the calculation, the distance between the two positions and the rear end of the pre-chamber is 400mm and 1000mm respectively, and the two combustion positions are determined according to the length of the combustion chamber of the ramjet engine. The angle between the axis of the secondary flow channel and the axis of the flame holder is different, and the secondary fuel injected by it realizes different position rich secondary combustion with the fuel gas from the rear end of the pre-chamber. The specific combustion organization of the secondary flow channel 3 is as follows: Figure 2As shown, because the secondary flow channel 3 has two angles with the combustion chamber axis, the secondary combustion with the gas occurs at different positions in the ramjet flow channel outside the device. The secondary combustion ensures the rich combustion in the pre-chamber and reduces the temperature in the pre-chamber, and makes the oxidant in the secondary flow channel 3 burn with the rich gas to reduce the waste of fuel.

[0022] The secondary flow channel 3 can flow the secondary fuel and the oxidant. When the secondary flow channel 3 is replaced with the oxidant, the fuel supply is closed first, then the purge valve is opened to ensure that there is no residual fuel in the secondary flow channel 3, then the purge valve is closed and the secondary oxidant valve is opened to realize the replacement of the medium in the secondary flow channel 3. When the oxidant is replaced, the replacement can be performed during the engine operation. The secondary flow channel 3 can flow the fuel and the oxidant, which ensures that the pre-chamber is at a lower combustion temperature and realizes the wide range adjustment of the overall oxygen-fuel ratio (oxygen-rich or fuel-rich) of the device. Therefore, the mixing ratio of the oxidant and the fuel in the pre-chamber does not change before and after the replacement.

[0023] To verify the stable flame device for combined engine ramjet channel ignition in the application, the following test is performed. Specifically, methane is used as the fuel, oxygen is used as the oxidant, the total flow is set to 0.5 kg / s, the pre-chamber pressure is set to 2 MPa, the back pressure of the ramjet channel 3 is set to 0.3 MPa, the overall oxygen-fuel ratio of the stable flame device body is set to 4, the pre-chamber oxygen-fuel ratio is set to 1, and the case where the secondary flow channel 3 is connected with the oxidant is taken as an example.

[0024] According to the above implementation working condition, the structure parameters of the stable flame device are calculated by theoretical calculation, as shown in Table 1.

[0025] Table 1 Structure parameters of stable flame device

[0026]

[0027] According to the structure parameters in Table 1, the working parameters of the stable flame device are calculated, and the calculation results are shown in Table 2.

[0028] Table 2 Working parameters of stable flame device

[0029]

[0030] The fuel and the oxidant in the pre-chamber are combusted at a mixing ratio of 1.0, the oxidant in the secondary flow channel 3 is combusted with the rich gas at a temperature of about 2990.4 K in the environment of the ramjet channel 0.3 MPa, and the afterburning is performed at positions 400 mm and 1000 mm away from the outlet position of the stable flame device. The use of the multi-stage afterburning torch jet stable flame device realizes the staged combustion, thereby maintaining the overall oxygen-fuel ratio equal to the stoichiometric ratio. The simulation temperature cloud map is as follows: Figure 3As shown, it can be seen that the secondary combustion of the fuel gas and the oxidant is realized in the ramjet flow passage, and a long-distance heat release region appears. When the temperature and dynamic pressure of the incoming airflow are low, it is difficult to realize ignition and stable combustion, and the generation of the long-distance heat release region facilitates the subsequent combustion organization in the ramjet flow passage, thereby improving the ignition and stable flame performance.

Claims

1. A flameholder for use in combination with engine ram inlet ignition, characterized by, The application relates to a flame stabilizer which is coaxially arranged in a combustion chamber, comprising a flame stabilizer body which is a columnar body and is provided with a precombustion chamber with two open ends along an axial line of the body; A plurality of secondary flow channels (3) are arranged on the flame stabilizer body and are spaced apart around the precombustion chamber, each of the secondary flow channels (3) is axially through the flame stabilizer body and is composed of two straight sections which are connected in front and back, the straight section in front is parallel to the axial line, and the straight section in back is inclined to the axial line from front to back and forms an acute angle with the axial line, the number of the secondary flow channels (3) is even, the included angles of two adjacent secondary flow channels (3) with the axial line are different; Fuel or oxidant flows into each of the secondary flow channels (3) from the front end and is injected into different positions in the combustion chamber from the back end, and the fuel or oxidant realizes different position secondary combustion with the fuel gas from the back end of the precombustion chamber; The number of the secondary flow channels (3) is four, two of the secondary flow channels (3) form a group, and the other two of the secondary flow channels (3) form another group; the included angles of the straight sections in back of the four secondary flow channels (3) with the axial line of the combustion chamber are all less than 5 DEG; two groups of the secondary flow channels (3) are used for injecting fuel or oxidant into two different positions in the precombustion chamber, and the distances between the two positions and the back end of the precombustion chamber are 400 mm and 1000 mm respectively; In the two groups of the secondary flow channels (3), the included angles of the straight sections in back of the secondary flow channels (3) with the axial line of the combustion chamber are 3.6 DEG and 1.5 DEG; The shape of the opening in front of the precombustion chamber is that two annular channels are coaxially arranged, wherein an outer annular channel is a fuel nozzle (1), and an inner annular channel is an oxidant nozzle (2), each of the nozzles is used for injecting corresponding fuel or oxidant into the precombustion chamber, and the fuel and the oxidant are combusted in the precombustion chamber.

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