A method for simulating lateral hot methane / air plume interference

Abstract

The application discloses a side heat jet flow interference simulation method based on methane / air gas, and the method comprises the following steps: obtaining the jet flow and the flow momentum ratio, the RT ratio and the jet flow specific heat ratio according to the real flow conditions and the real gas engine jet flow conditions; simulating the momentum ratio and the RT ratio according to the ground flow conditions, and determining the momentum and the RT parameters of the methane gas jet flow under the condition of meeting the geometric similarity; determining the methane / air mixing ratio according to the RT and the specific heat ratio parameters of the methane gas jet flow, and determining the total pressure of the required gas and the methane and air flow according to the momentum of the methane gas jet flow; and obtaining the force interference factor and the orbit control offset of the jet flow interference by using the ground wind tunnel test or the numerical simulation method. The application can be used for the ground heat jet flow interference wind tunnel test or the numerical simulation.

Description

Technical Field

[0001] This invention relates to the field of ground simulation of thermal jet interference, and specifically to a method for simulating the interference force and torque of lateral thermal jets based on methane / air combustion gas. Background Technology

[0002] Lateral jet control technology uses a side-mounted gas turbine to generate direct force for attitude or trajectory control of an aircraft. This direct force jet control technology can supplement aerodynamic control surface capabilities at high altitudes, rapidly change the aircraft's trajectory and attitude, and can be used for various control purposes such as braking and separation. Lateral jet control technology is widely used in hypersonic / hypersonic aircraft. When the jet engine operates, the gas jet and the high-speed incoming flow generate complex disturbance flows involving shock waves / boundary layer interference, shock waves / shock wave interference, flow separation / reattachment, and vortices. These disturbances are accompanied by high-temperature jet, multi-medium, and secondary combustion effects, altering the aircraft's aerodynamic / thermal environment and generating disturbance forces / torques. Previously, ground-based studies used ambient-temperature air jets with similar pressure and momentum ratios to simulate gas jets, obtaining jet disturbance forces / torques. The simulation accuracy was generally sufficient for engineering applications. However, with the development of hypersonic vehicles, especially near-space hypersonic offensive and defensive weapons, the jet flow rate and thrust used have increased further, and the flight speed has increased further. The difference between cold and hot jet interference forces / torques is large. The interference force / torque results obtained by ground-based cold jet simulations have large errors and are difficult to meet the needs of engineering applications. Therefore, it is necessary to carry out research on hot jet interference methods.

[0003] Previously, ground-based thermal spray simulation methods typically used solid rocket motors or Ludwig tubes to provide high-temperature gas flow for thermal spray interference simulation studies. However, due to the unclear gas composition, complex chemical mechanism, and poor adjustability of solid rocket motors, and the short test time and large test error of Ludwig tubes, the simulation results could not meet the needs of engineering applications, and the thermal spray simulation method was not mature. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a method for simulating lateral thermal jet interference based on methane / air fuel gas. By ensuring the jet momentum ratio, RT ratio and approximate jet specific heat ratio, the methane fuel gas jet parameters for ground studies are obtained. The method simulates the total pressure ratio while simulating the momentum ratio, and approximates the mass flow ratio while simulating the RT ratio and approximate jet specific heat ratio. This allows ground thermal jet tests to obtain force interference factors and orbital control offsets, and provides high simulation accuracy for lateral thermal jet interference results of different propellant types under real flight conditions.

[0005] The technical solution of this invention is:

[0006] A method for simulating lateral thermal jet interference based on methane / air fuel gas includes the following steps:

[0007] Step 1: Obtain the jet flow to incoming flow ratio, RT ratio, and jet specific heat ratio based on the actual incoming flow conditions and the actual gas engine jet flow conditions;

[0008] Step 2: Combine the momentum ratio, RT ratio, and approximate specific heat ratio of the surface inflow conditions to determine the momentum, RT, and specific heat ratio of the methane gas jet used for simulation;

[0009] Step 3: Determine the methane / air mixing ratio based on the methane fuel jet RT and specific heat ratio parameters determined in Step 2, and determine the total pressure of the methane fuel jet and the flow rates of methane and air based on the methane fuel jet flow rate determined in Step 2.

[0010] Step 4: Use ground wind tunnel tests or numerical simulation methods to obtain the force interference factor and track control offset of the jet flow interference.

[0011] Preferably, the momentum ratio is the ratio of the jet nozzle exit momentum to the incoming momentum, and the incoming momentum reference area is the geometric feature area of ​​the model.

[0012] Preferably, RT is the product of the gas constant R and the local static temperature T, and the RT ratio is the ratio of the RT at the nozzle outlet to the RT of the incoming flow.

[0013] Preferably, the specific heat ratio of the jet is the specific heat ratio at the nozzle outlet of the jet.

[0014] Preferably, in step two, the surface inflow conditions should be consistent with the inflow Mach number and flow regime of the object under study.

[0015] Preferably, in step two, the specific heat ratio of the simulated methane gas jet is approximately the same as that of the actual jet, with an error of less than 5%.

[0016] Preferably, in step four, the force interference factor K of the jet interference... y satisfy

[0017]

[0018] In the formula, ΔC y It is the additional interference, C jet It is the jet thrust coefficient, C y,jeton C y,jetoff These are the aerodynamic coefficient components under conditions of spraying and no spraying;

[0019] Track control offset

[0020] In the formula, ΔS is the offset distance of the jet thrust application point, L is the projectile length, and C is the distance of the projectile body. mz,jeton C mz,jetoffPitch component of aerodynamic moment coefficient under both jet and non-jet conditions, C jet It is the jet thrust coefficient.

[0021] Preferably, a negative ΔS value represents forward movement, generating a head-down torque; a positive value represents backward movement, generating a head-up torque.

[0022] The advantages of this invention compared to existing technologies are:

[0023] (1) Compared with the original cold spray simulation, the present invention simulates more parameters. Methane gas significantly increases the jet temperature compared with room temperature air. Since the main components of methane gas are CO2, CO, H2O, N2, O2, H2, etc., it can simulate the main components of most real engine gas. Therefore, the jet temperature and gas medium properties are closer to those of real gas engines. The total pressure ratio, RT ratio, and approximate jet specific heat ratio and approximate mass flow ratio are further simulated. Compared with the original cold spray simulation, the methane / air gas can adjust the jet temperature and main gas components by adjusting the mixing ratio. It has stronger applicability to the simulation of different propellant gas jets. The simulation results of force interference factor / orbit control offset are closer to the real flight interference results, and the simulation accuracy is higher. Compared with the original hot spray simulation, the methane gas jet is more stable, has a longer test time, better repeatability, and a clearer chemical mechanism, which is conducive to ground research.

[0024] (2) This invention can be used as a supplement to the original air cold spray simulation method, solid gas hot spray simulation method, and Ludwig tube hot spray simulation method. Attached image description:

[0025] Figure 1 This is a flowchart of a lateral thermal jet interference simulation method based on methane-air combustion gas according to the present invention;

[0026] Figure 2 This is a schematic diagram of a typical lateral thermal jet nozzle layout provided in an embodiment of the present invention;

[0027] Figure 3 This is a schematic diagram of the lateral thermal jet interference flow field provided in an embodiment of the present invention;

[0028] Figure 4 This is a diagram showing the results of the lateral jet force interference factor and orbital control offset under the simulation method provided in this embodiment of the invention. The force interference factor and orbital control offset obtained by the simulation method under numerical simulation are closer to the results of hot jet interference under flight conditions than those obtained by cold jetting in the past. Detailed implementation method:

[0029] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] Methane fuel gas has the clearest chemical mechanism among hydrocarbon fuels and can burn stably with air over a wide range of mixing ratios, which is beneficial for simulating thermal injection interference. This invention develops a method for simulating methane fuel gas thermal injection, providing a technical foundation for ground-based thermal injection simulation.

[0031] Figure 1 This is a flowchart of the lateral thermal jet interference simulation method based on methane-air combustion provided by the present invention. Figure 1 As shown, the method includes the following steps:

[0032] Step 1: Determine the momentum ratio, RT ratio, and specific heat ratio of the jet stream to the incoming stream based on the actual incoming flow conditions and the actual gas engine jet flow conditions.

[0033] The momentum ratio is the ratio of the jet nozzle exit momentum to the incoming momentum, with the incoming momentum reference area being the geometric feature area of ​​the model. RT is the product of the gas constant R and the local static temperature T, and the RT ratio is the ratio of the jet nozzle exit RT to the incoming RT. The jet specific heat ratio is the jet nozzle exit specific heat ratio.

[0034] Step 2: Based on the ground research conditions, simulate the momentum ratio, RT ratio, and approximate jet specific heat ratio to determine the gas jet momentum, RT, and specific heat ratio parameters;

[0035] Momentum ratio:

[0036] RT ratio:

[0037] Approximate jet specific heat ratio: γ 真实燃气 ≈γ 甲烷燃气

[0038] A j It is the nozzle exit area, A ∞ is the reference area of ​​the incoming flow (the cross-sectional area of ​​the projectile at the position of the nozzle axis), P is the static pressure, γ is the specific heat ratio, M is the Mach number, R is the gas constant, T is the gas temperature, the subscript j represents the jet, and the subscript ∞ represents the incoming flow.

[0039] The simulated ground-based inflow conditions should match the Mach number and flow regime of the inflow to the object under study. The specific heat ratio of the simulated methane gas jet should be approximately the same as that of the actual jet, with an error of less than 5%.

[0040] Step 3: Determine the methane / air mixing ratio based on the methane fuel jet RT and specific heat ratio, and determine the total methane fuel pressure and methane and air flow rates based on the methane fuel jet flow rate;

[0041] Step 4: Use wind tunnel tests or numerical simulation methods to obtain the force interference factor and track control offset of the lateral jet interference.

[0042] Force interference factor:

[0043] In the formula, ΔC y It is the additional interference, C jet It is the jet thrust coefficient, C y,jeton C y,jetoff These are the aerodynamic coefficient components with and without jet (with jet force excluding jet thrust), where y represents the normal component, jetoff represents without jet, and jeton represents with jet.

[0044] Track control offset:

[0045] In the formula, ΔS is the offset distance of the jet thrust application point, which means the change in the position of the equivalent jet thrust application point caused by jet interference. A negative value represents forward movement, generating a nose-down moment, and a positive value represents backward movement, generating a nose-up moment. L is the projectile length, ΔS / L% is the percentage of the jet thrust application point offset distance to the total projectile length, and C... mz,jeton C mz,jetoff C represents the aerodynamic torque coefficient components under both sprayed and non-sprayed conditions (without jet torque). jet It is the jet thrust coefficient.

[0046] Example:

[0047] In this embodiment, a typical calculation model was selected as the example for the lateral thermal jet layout. The calculation model is a typical track-controlled jet cone-column-skirt shape. The total length of the model is L = 2250 mm, the nozzle exit diameter is d = 69.8 mm, and the nozzle axis is located near the center of mass of the projectile, x = 1177 mm. The torque reference point is the point of action of the track-controlled jet (1177 mm, 0, 0). The jet parameters are shown in Table 1, and the incoming flow parameters are shown in Table 2.

[0048] Table 1: Jet Parameters

[0049]

[0050] Table 2: Incoming Flow Parameters

[0051]

[0052] Figure 2 This is a schematic diagram of a typical lateral thermal jet nozzle layout provided in an embodiment of the present invention. Figure 3 This is a schematic diagram of the lateral thermal jet interference flow field provided in an embodiment of the present invention. Figure 4 This diagram shows the results of the lateral jet force interference factor and orbital control offset under the simulation method provided in this embodiment of the invention. The force interference factor and orbital control offset obtained by this simulation method in numerical simulation are closer to the results of hot jet interference under flight conditions than those obtained by traditional cold jet simulations. The results indicate that, compared with traditional cold jet simulations with similar pressure and momentum ratios, the simulation method described in this invention can significantly improve the simulation accuracy of the jet force interference factor and orbital control offset.

[0053] The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. For those skilled in the art, various modifications or alterations will be readily apparent within the scope of the claims, and these also fall within the technical scope of the present invention.

Claims

1. A method of simulating a lateral hot methane / air gas plume interference, characterized in that, Includes the following steps: Step 1: Obtain the jet flow to incoming flow ratio, RT ratio, and jet specific heat ratio based on the actual incoming flow conditions and the actual gas engine jet flow conditions; Step 2: Combine the momentum ratio, RT ratio, and approximate specific heat ratio of the surface inflow conditions to determine the momentum, RT, and specific heat ratio of the methane gas jet used for simulation; Step 3: Determine the methane / air mixing ratio based on the methane fuel jet RT and specific heat ratio parameters determined in Step 2, and determine the total pressure of the methane fuel jet and the flow rates of methane and air based on the methane fuel jet flow rate determined in Step 2. Step 4: Use ground wind tunnel tests or numerical simulation methods to obtain the force interference factor and track control offset of the jet flow interference.

2. A method of simulating the interference of a lateral hot methane / air gas plume according to claim 1, characterized in that: The momentum ratio is the ratio of the jet nozzle exit momentum to the incoming momentum, and the incoming momentum reference area is the geometric feature area of ​​the model.

3. A method of simulating the interference of a lateral hot methane / air gas plume according to claim 1, characterized in that: RT is the product of the gas constant R and the local static temperature T, and the RT ratio is the ratio of the RT at the nozzle outlet to the RT of the incoming flow.

4. A method of simulating the interference of a lateral hot methane / air gas plume according to claim 1, characterized in that: The specific heat ratio of the jet is the specific heat ratio at the nozzle exit of the jet.

5. A method of simulating the interference of a lateral hot methane / air gas plume according to claim 1, characterized in that: In step two, the surface flow conditions should be consistent with the Mach number and flow regime of the flow to the object under study.

6. A method of simulating the interference of a lateral hot methane / air gas plume according to claim 1, characterized in that: In step two, the specific heat ratio of the simulated methane gas jet is approximately the same as that of the actual jet, with an error of less than 5%.

7. A method of simulating the interference of a lateral hot methane / air gas plume according to claim 1, characterized in that: In step four, the force disturbance factor K of the jet flow interference y satisfies where ΔC y is the additional interference, C jet is the jet thrust coefficient, C y,jeton C y,jetoff is the aerodynamic force coefficient component with and without jet. Track control offset where ΔS is the offset distance of the jet thrust action point, L is the body length, C mz,jeton , C mz,jetoff is the aerodynamic moment coefficient component in the pitch direction with and without jet, C jet is the jet thrust coefficient.

8. A method of simulating the interference of a lateral hot methane / air gas plume according to claim 7, characterized in that: A negative ΔS value indicates forward movement, generating a head-down torque; A positive value indicates a backward movement, generating a head-up torque.

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