Hybrid fuel multi-working condition oblique knock engine performance analysis method and device

Abstract

The application discloses a performance analysis method of a mixed fuel multi-working condition oblique detonation engine, and the oblique detonation engine comprises an air inlet channel section, a fuel mixing section, a combustion chamber section and a tail nozzle section, and the method comprises the following steps: according to the sequential characteristics of the working process of the oblique detonation engine, sequentially performing parameter solving of an oblique shock wave compression module of the air inlet channel section, parameter solving of a mixing module of the fuel mixing section, parameter solving of an oblique detonation module of the combustion chamber section and parameter solving of an isentropic expansion module of the tail nozzle section; and combining corresponding parameters of the solving processes, including temperature, pressure and velocity, performing theoretical thrust calculation of the oblique detonation engine, and calculating thrust performance including specific impulse. The method sets fuel composition, air inlet working condition, mixing working condition, combustion working condition and expansion working condition of the oblique detonation engine, and can quickly calculate specific impulse of the oblique detonation engine and each physical quantity along the way.

Description

Technical Field

[0001] This invention relates to the field of hypersonic engine technology, and in particular to a method and apparatus for performance analysis of a mixed-fuel multi-condition oblique detonation engine. Background Technology

[0002] Scramjet engines reduce the inlet compression to maintain supersonic airflow while simultaneously injecting fuel through simultaneous mixing and combustion within the supersonic airflow, giving them a performance advantage in hypersonic flight. However, as flight Mach numbers further increase ( Due to the constraints of aircraft size, the length of an engine is limited. As the Mach number of the incoming flow increases, the residence time of air within the engine decreases, easily leading to uneven mixing and a significant drop in combustion efficiency. To ensure thorough mixing and combustion of fuel and air, the length of the combustion chamber must be increased, which in turn significantly increases the weight of the aircraft, resulting in a substantial increase in drag. Therefore, the time required for traditional simultaneous mixing and combustion is no longer effectively matched with the residence time of the airflow within the ramjet engine's internal channels. To address this issue, the oblique detonation engine pre-injects fuel into the intake (or forebody), pre-mixing it with air to a certain extent before it enters the combustion chamber. Oblique detonation waves, which can remain stationary in hypersonic airflow, are induced by devices such as oblique detonation waves. Because combustion organized through oblique detonation waves is closer to isochoric combustion, it has advantages such as a fast heat release rate and high thermal cycle efficiency. Therefore, it can significantly shorten the combustion chamber length and reduce the heat release area, making it an ideal combustion mode applicable to high Mach number air-breathing engines. As a type of ramjet engine, the oblique detonation engine directly utilizes atmospheric oxygen as an oxidizer without requiring a separate oxidizer. Furthermore, the detonation wave is a supersonic combustion wave with a short combustion time on the order of microseconds, much faster than the diffusion combustion of a scramjet engine. Oblique detonation engines have attracted widespread attention due to their simple structure, small size, light weight, and high specific impulse. Rapid and efficient evaluation of engine performance is an important direction in oblique detonation research, necessitating analysis of its working process, establishment of simplified models and theoretical calculation methods for the working processes of each component, and ultimately, a theoretical evaluation method for the overall engine performance. However, existing performance evaluation methods are limited to single fuels, mostly hydrogen, and cover very few operating conditions. Summary of the Invention

[0003] This invention provides a method for performance analysis of a mixed-fuel, multi-condition oblique detonation engine. The method sets the fuel composition, intake conditions, mixing conditions, combustion conditions, and expansion conditions of the oblique detonation engine, and quickly calculates the specific impulse of the oblique detonation engine and various physical quantities of its working process. Intake conditions include: incoming air temperature, pressure, velocity (unit: Mach number), intake duct oblique shock wave compression angle (also known as compression angle), and setting one or more oblique shock wave compressions; Mixing conditions include: adjusting the fuel-oxidizer ratio to control lean and rich combustion. Lean and rich combustion are achieved through the fuel-oxidizer ratio. Less fuel relative to oxidizer results in lean combustion, and more fuel relative to oxidizer results in rich combustion. For example, if the molar ratio of hydrogen to oxygen is 2:1, they react completely to form water. If the molar ratio of hydrogen to oxygen becomes 3:1, then there is more hydrogen, which is called rich combustion, and the same applies to lean combustion; Combustion conditions include: the angle of the combustion chamber (also known as the angle of the combustion chamber slope, i.e., the oblique detonation angle), and the oblique detonation wave angle; Expansion conditions include: expanding to a specified area and expanding to a specified pressure.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] In a first aspect, embodiments of the present invention provide a method for performance analysis of a mixed-fuel, multi-condition oblique detonation engine, wherein the oblique detonation engine includes an intake section, a fuel mixing section, a combustion chamber section, and a tailpipe section, and the method includes:

[0006] Based on the sequential characteristics of the working process of the oblique detonation engine, the parameters of the oblique shock wave compression module in the intake section, the mixing module in the fuel mixing section, the oblique detonation module in the combustion chamber section, and the isentropic expansion module in the tail nozzle section are solved in sequence.

[0007] By combining the corresponding parameters of each solution process, including temperature, pressure and velocity, the theoretical thrust of the oblique detonation engine is calculated, and the thrust performance including specific impulse is calculated.

[0008] In some possible implementations, the parameter solving of the inlet section oblique shock wave compression module includes...

[0009] Construct the oblique shock wave compression module, set the flight altitude and flight speed of the aircraft, and input the corresponding incoming air temperature, incoming air pressure, and incoming air velocity (Mach number) according to the required flight altitude and flight speed.

[0010] The incoming air is compressed by one or more oblique shock waves, and the angle of compression of each oblique shock wave is set. The parameters of the compressed air after the wave are solved, including the first temperature, the first pressure and the first velocity.

[0011] In some possible implementations, the parameter solving of the fuel blending section includes:

[0012] The mixing module is constructed, and the parameters of the mixed fuel are set, including the composition and ratio of the fuel, the temperature and injection speed of the fuel, and the ratio of fuel to oxidant (air) (lean and rich fuel). Combined with the parameters of the compressed air after the wave, the parameters of the mixed mixture are solved, including the second temperature, the second pressure and the second speed.

[0013] In some possible implementations, the parameter solving for the combustion chamber section oblique detonation module includes:

[0014] The oblique detonation module is constructed by setting the angle of the combustion chamber slope or the oblique detonation wave angle, and combining the parameters of the mixed mixture to calculate the parameters after the oblique detonation wave, including the third temperature, the third pressure and the third velocity.

[0015] In some possible implementations, the solution of the isentropic expansion module parameters for the tailpipe section includes:

[0016] The isentropic expansion module is constructed, and expansion to a specified pressure or area is set. Combined with the parameters after the oblique detonation shock wave, the parameters of the expanded gas are solved, including the fourth temperature, the fourth pressure, and the fourth velocity.

[0017] In some possible implementations, the calculation of the theoretical thrust of the oblique detonation engine, which calculates the thrust performance including specific impulse, includes:

[0018] The momentum method is used to estimate the parameters of the engine. The momentum increments flowing into and out of the engine are calculated, and the thrust of the engine is calculated according to the momentum theorem.

[0019] In some possible implementations, the design of the tailpipe section is also included, prior to the calculation of the theoretical thrust of the oblique detonation engine, specifically including:

[0020] Assuming the gas expands to a specified area after a slant detonation wave, a convergent-divergent (CD) nozzle is designed. During the design process, the throat cross-sectional area A is determined using gas properties and isentropic relationships. t For the expansion section, a feature line MOC is used to shorten its length to design the nozzle profile; the exit area after the isentropic expansion module is A4, and the exit Mach number is... .

[0021] Secondly, embodiments of the present invention provide a performance analysis device for a mixed-fuel multi-condition oblique detonation engine, the device comprising: an oblique shock wave compression module, a mixing module, an oblique detonation module, an isentropic expansion module, and a theoretical thrust calculation module;

[0022] The oblique shock wave compression module sets the flight altitude and speed of the aircraft, and inputs the corresponding incoming air temperature, incoming air pressure, and incoming air velocity (Mach number) according to the required flight altitude and speed.

[0023] The incoming flow is set to pass through one or more oblique shock waves, and the angle of compression of each oblique shock wave is set. The wave back parameters of the air, including the first temperature, the first pressure and the first velocity, are solved.

[0024] The mixing module sets the parameters of the mixed fuel, including the composition and ratio of the fuel, the temperature and injection speed of the fuel, and the ratio of fuel to oxidant. Combined with the wave back parameters of the air, it solves the parameters of the mixed mixture, including the second temperature, the second pressure and the second speed.

[0025] The oblique detonation module sets the angle of the combustion chamber slope or the oblique detonation wave angle, and calculates the parameters after the oblique detonation wave, including the third temperature, the third pressure and the third velocity, in combination with the parameters of the mixed mixture.

[0026] The isentropic expansion module is set to expand to a specified pressure or a specified area. Combined with the parameters after the oblique detonation wave, the parameters of the expanded gas are solved, including the fourth temperature, the fourth pressure, and the fourth velocity.

[0027] The module for calculating the theoretical thrust of a slant-detonation engine uses the momentum method to estimate the engine parameters. It calculates the momentum increments flowing into and out of the engine and then calculates the engine thrust based on the momentum theorem.

[0028] Thirdly, embodiments of the present invention provide an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the mixed-fuel multi-condition oblique detonation engine performance analysis method as described in the first aspect.

[0029] Fourthly, embodiments of the present invention provide a computer-readable storage medium storing computer instructions that cause a processor to execute the mixed-fuel multi-condition oblique detonation engine performance analysis method as described in the first aspect.

[0030] The advantages of this invention are:

[0031] 1. This invention comprehensively considers the influence of factors such as the aircraft's flight speed and altitude, the oblique shock wave compression angle, the number of shock channels through which the incoming flow undergoes oblique shock wave compression, fuel mixing parameters (fuel composition, ratio, temperature, injection rate), fuel-oxidizer ratio, the angle of the combustion chamber ramp (i.e., the oblique detonation angle) or oblique detonation wave angle, and expansion to a specified area / pressure on the performance of the oblique detonation engine. Compared to other models, the number of parameters that can be changed is greatly increased, which means it is more likely to find superior theoretical performance parameters for the oblique detonation engine.

[0032] 2. Because the performance analysis framework of this invention is calculated in modules, each module yields corresponding parameters such as temperature, pressure, and velocity. By analyzing the parameters obtained from solving each module, the maximum operating pressure and temperature in each section—the intake section, fuel mixing section, combustion chamber section, and exhaust nozzle section—can be obtained, providing a basis for the structural design and material selection of each engine section. Furthermore, this invention considers chemical equilibrium during the isentropic expansion stage, which is more consistent with the actual working process of a tilt-knock engine.

[0033] 3. This invention calculates the performance of the tilt detonation engine by setting various parameters, allowing designers to quickly make a basic judgment on the performance parameters of the tilt detonation engine, thereby effectively reducing the economic and time costs of tilt detonation engine optimization design. Attached Figure Description

[0034] Figure 1 A schematic diagram of the frame structure of the oblique detonation engine according to an embodiment of the present invention;

[0035] Figure 2 A schematic diagram of the first oblique shock wave compression angle θ1 and the second oblique shock wave compression angle θ2 in the oblique detonation engine frame structure of this embodiment of the invention;

[0036] Figure 3 Flowchart of the performance analysis of the oblique detonation engine according to an embodiment of the present invention;

[0037] Figure 4 A flowchart illustrating the compression of incoming flow by two oblique shock waves according to an embodiment of the present invention;

[0038] Figure 5 Flowchart of parameter solving for the fuel blending module in this embodiment of the invention;

[0039] Figure 6 Flowchart of the isentropic expansion solution module for the oblique detonation engine according to an embodiment of the present invention;

[0040] Figure 7 A schematic diagram of the expansion section wall contour according to an embodiment of the present invention;

[0041] Figure 8A schematic diagram illustrating the specific impulse of the oblique detonation engine of this invention as a function of flight altitude and Mach number.

[0042] In this diagram, 1 – Region 1 – is a triangular region, and its parameters are calculated using the oblique shock wave compression module; 2 – Region 2 – is a triangular region, and its parameters are calculated using the fuel mixing module; 3 – Region 3 – is a quadrilateral region, and its parameters are calculated using the oblique detonation solution module; 4 – Region 4 – is a horn-shaped region, and its parameters are calculated using the isentropic expansion module; 5 – the region enclosed by three solid lines represents the cowling of the oblique detonation engine; 6 – the region enclosed by five solid lines represents the fuselage of the aircraft; the dashed line a represents the outer contour of the air intake corresponding to the generation of a shock wave c; the solid lines a1 and a2… Line b represents the outer contour of the intake corresponding to the generation of the first shock wave c and the second shock wave d; dashed line b represents the outer contour of the intake corresponding to the generation of three shock waves (where the first shock wave is also the first shock wave c, and the corresponding second and third shock waves are not shown); c - first shock wave; d - second shock wave; e - oblique detonation wave (also the boundary between region 2 and region 3); f - boundary between region 3 and region 4; θ1 - compression angle of the first oblique shock wave; θ2 - compression angle of the second oblique shock wave; β - oblique detonation wave angle; δ - angle of the combustion chamber, also known as the angle of the combustion chamber slope, i.e., oblique detonation angle θ3. Detailed Implementation

[0043] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. At the same time, in the description of the embodiments of this application, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0044] Example 1

[0045] This invention provides a method for performance analysis of a mixed-fuel, multi-condition oblique detonation engine. First, refer to... Figure 1A frame structure for a slant detonation engine includes four parts: an intake section compressed by two slant shock waves (the first shock wave and the second shock wave), a fuel mixing section, a slant detonation combustion section, and a tail nozzle section. Parameters are solved for the four working processes corresponding to these four parts: parameter solving for the slant shock wave compression module of the intake section, parameter solving for the mixing module of the fuel mixing section, parameter solving for the slant detonation module of the combustion chamber section, and parameter solving for the isentropic expansion module of the tail nozzle section. The pre-set parameters are used to obtain the required performance parameters through these four module parameter solutions.

[0046] Reference Figure 3 This paper provides a performance analysis method for a mixed-fuel multi-condition oblique detonation engine with incoming air compressed by two oblique shock waves, including the following steps:

[0047] Set the aircraft's flight altitude and speed;

[0048] The required flight altitude and speed are converted into the incoming air temperature, pressure, and velocity (unit: Mach number). , is the parameter input to the inlet of the oblique shock compression section or before the oblique shock compression or at the engine inlet;

[0049] Set the number of channels through which the incoming airflow is compressed by the oblique shock wave, and the angle of each compression angle;

[0050] Steps The parameters are input into the oblique shock wave compression module to obtain the gas parameters after the oblique shock wave, including the first temperature, the first pressure, and the first velocity. These are the parameters after compression by the oblique shock wave, which need to be input into the inlet of the fuel mixing section;

[0051] Set the composition and ratio of fuel, temperature and injection speed, fuel and oxidant (air) ratio to make lean or rich fuel, and the ratio of fuel area to flow channel area; the fuel area is the area of ​​the fuel injection port, and the flow channel area is the cross-sectional area of ​​the fuel mixing section.

[0052] Steps The obtained or set parameters are input into the fuel blending module to obtain the parameters of the blended gas mixture, including the second temperature, the second pressure, and the second velocity. These are the mixed parameters, which need to be input into the inlet of the oblique detonation combustion.

[0053] Set the angle δ of the combustion chamber ramp or set the angle β of the oblique detonation wave to be formed;

[0054] Steps The obtained or set parameters are input into the oblique detonation solution module to obtain the gas parameters after the detonation wave, including the third temperature, the third pressure, and the third velocity. , which are the parameters after oblique detonation combustion, are input into the inlet of isentropic expansion;

[0055] Setting the gas after the detonation wave to expand to a specified pressure or a specified area means that it can expand to a specified pressure or a specified area in the isentropic expansion section.

[0056] Steps The settings are applied to the isentropic expansion module to calculate the parameters of the gas after expansion, including the fourth temperature, the fourth pressure, and the fourth velocity, i.e. , is the parameter after isentropic expansion, which is also the parameter of the airflow at the engine outlet;

[0057] Combining steps The obtained parameters are used to design the tail nozzle section;

[0058] The theoretical thrust of the engine can be calculated from the parameters in the above steps.

[0059] Based on the specific data in this embodiment, the following description is provided. ~ The content is as follows:

[0060] Set the aircraft's flight altitude and speed;

[0061] Based on the airspace and speed range of the oblique detonation engine, appropriate flight altitude and speed are set. In this embodiment, the flight altitude is selected as 25, 30, and 35 kilometers, and the flight speed is 10-17 Mach.

[0062] The required flight altitude and speed are converted into the temperature, pressure, and Mach number of the incoming airflow.

[0063] The speed of an aircraft corresponds to the Mach number of the incoming airflow. Knowing the aircraft's altitude allows us to calculate the temperature and pressure of the incoming airflow at that altitude.

[0064] Set the number of channels through which the incoming airflow is compressed by the oblique shock wave, and the angle of each compression angle;

[0065] Reference Figure 2 As shown, in this embodiment, the incoming air is compressed by two oblique shock waves in the intake section: the first shock wave c and the second shock wave d. The compression angle of each intake section is θ1=θ2=6°. In another embodiment, the incoming air is compressed by one oblique shock wave in the intake section, namely the first shock wave c. The dashed line a represents the outer contour of the intake corresponding to the generation of the first shock wave c. In yet another embodiment, the incoming air is compressed by three oblique shock waves in the intake section: the first shock wave c and two other shock waves (the corresponding second and third shock waves are not shown). The dashed line b represents the outer contour of the intake corresponding to the generation of the three shock waves.

[0066] See Figure 4 , the steps The parameters are input into the oblique shock wave compression module to obtain the gas parameters after the oblique shock wave;

[0067] The following are The oblique shock wave compression module will be explained as follows:

[0068] First, the density, pressure, enthalpy, and velocity in front of the normal shock wave are expressed as follows: The corresponding density, pressure, enthalpy, and velocity of the gas after the shock wave are expressed as follows. Rankin-Ugogno (used to describe pressure and enthalpy changes) The formula is:

[0069]

[0070] in These are the components perpendicular to the shock wave, respectively. These are the oblique shock wave compression angle and the oblique detonation wave angle, respectively. Including θ1 and θ2, =θ1=θ2=6°, which is specified manually. Then it is possible that:

[0071]

[0072] Using the ideal gas law thermal state equation Pair To be sealed off, among which The average molecular mass of the gas. Given the molar number and molar enthalpy of each component of a gas, its fundamental physical properties are as follows: Direct database access.

[0073] The solution process uses the Newton-Raphson (Newton-Raphson) method. The method is used to determine the roots of the equations governing reactivity and freezing shock waves. The steps are as follows: To solve for the freezing shock wave, the solution for the reactive shock wave is as follows: This is evident in the fact that reactive shock waves are shock waves involving chemical reactions, while freezing shock waves are the compression phase of oblique shock waves, which is a physical process.

[0074] Set the composition and ratio of fuel, temperature and injection speed, fuel-oxidant ratio, and fuel area to flow channel area ratio;

[0075] In this embodiment, the composition of the fuel is set as follows: The ratio is 1:9, and the initial temperature of the mixed fuel is... for The injection speed is The fuel and oxidizer are mixed in a ratio that ensures complete reaction. The ratio of fuel area to channel area during the mixing process... Set to 0.02.

[0076] See Figure 5 , the steps The obtained parameters are input into the fuel blending module to obtain the parameters of the blended gas mixture.

[0077] The following are The fuel blending module will be explained as follows:

[0078] First, the static temperature of the fuel is obtained from the initial temperature of the mixed fuel. (Actual temperature at the current speed):

[0079]

[0080] In the formula γ is the dimensionless temperature ratio, and γ is the specific heat ratio.

[0081] In this embodiment, the mixing process is constant cross-sectional mixing, meaning the flow cross-sectional area remains constant in the fuel mixing section. The governing equations are:

[0082] Momentum equation:

[0083]

[0084] Energy equation:

[0085]

[0086] Continuity equation:

[0087]

[0088] Using the ideal gas law Closed, in The ratio of fuel area to flow channel area is the ratio of the cross-sectional area of ​​the fuel injection port to the cross-sectional area of ​​the fuel mixing section. It is a variable parameter that affects engine performance.

[0089] Joint With the following formula:

[0090]

[0091] At this time, the formula It can be transformed into:

[0092]

[0093] The formula Combining the ideal gas law After sorting, we get:

[0094]

[0095] The formula Resubstitution After sorting, we can obtain:

[0096]

[0097] Mode The Newton-Raphson iterative method can be used to solve this problem.

[0098]

[0099] The main flowchart for solving this embodiment is referenced. Figure 5 , initial velocity Assign to Finally, the temperature of the mixed gas was obtained. With speed .

[0100] Set the angle of the combustion chamber ramp or set the angle of the oblique detonation wave to be formed;

[0101] In this embodiment, the angle of the combustion chamber ramp is set to 26°. Although a large ramp angle will slightly reduce the performance of the ramp detonation engine, it is enough to enable the air-fuel mixture to detonate at a lower Mach number.

[0102] Steps The obtained parameters are input into the oblique detonation solution module to obtain the gas parameters after the detonation wave, including the third temperature, the third pressure and the third velocity;

[0103] The oblique detonation solution module can calculate the temperature before detonation. ,pressure ,speed Oblique detonation angle Input the temperature after the detonation wave and solve for the temperature. ,pressure ,speed .

[0104] The oblique detonation solution module is based on ( The oblique shock wave compression module, combined with chemical equilibrium, adopts the same ( The solution method is used to determine the roots of the equations governing the reactive shock wave. The following explains the chemical equilibrium module:

[0105] This module adopts Free energy minimization method To calculate a closed system A mixture of substances Under given pressure and temperature molar composition :

[0106]

[0107] in These are the number of moles and the chemical potential of the substance, respectively. Components The molecular formula contains elements The number of atoms; For elements The total number of moles.

[0108] Applying the ideal gas law to the chemical potential:

[0109]

[0110] in It is the material under reference pressure and the chemical potential at a specified temperature.

[0111] By introducing slack variables, these expressions are reformulated as a set of equality constraints, resulting in:

[0112]

[0113] in A constant used to ensure numerical stability.

[0114] From the formula Equality constraint problem Solving using the Lagrange multiplier method, we introduce the Lagrange function:

[0115]

[0116] in The variables introduced for the relaxation iteration are α, which is the multiplier vector, and q and r, which are the aforementioned qi and ri.

[0117] Using the formula, we can obtain Differential ,Right now:

[0118]

[0119] Later, the multidimensional Newton-Rafson method was adopted. The method is used to solve this system of equations.

[0120] Set the gas after the detonation wave to expand to a specified pressure or to a specified area;

[0121] In this embodiment, for ease of understanding The tail nozzle is designed to expand to a specified area. Although the calculated performance of the oblique detonation engine may decrease slightly, its dimensions are more accurate than those of expanding to a specified pressure. Steps The settings are applied to the isentropic expansion module to calculate the parameters of the gas after expansion;

[0122] The following are The isentropic expansion module will be explained as follows:

[0123] The gas composition after solving the oblique detonation combustion problem is known. Given relevant parameters, calculate isentropic expansion. The flow parameters at that time. The governing equation for this problem is:

[0124] Continuity equation:

[0125]

[0126] Energy equation:

[0127]

[0128] Isoentropy condition:

[0129]

[0130] Using ideal state equations In the closed loop, S represents entropy, S3 is the entropy of the airflow before isentropic expansion, that is, after oblique detonation combustion, and S4 is the entropy of the airflow after isentropic expansion.

[0131] From the equation:

[0132]

[0133] Where yi is the number of moles of component i in the gas mixture, T and p are the temperature and pressure of the gas mixture, and Ru is the universal gas constant with a value of 8.314 J / (mol·K). It is the entropy of the gas mixture at temperature T and pressure p.

[0134] After simplification, the temperature after expansion is obtained. Nonlinear equations:

[0135]

[0136] Where T3 and P3 are the temperature and pressure of the gas before isentropic expansion, and T4 and T4 are the temperature and pressure of the gas after isentropic expansion; denoted as the isobaric molar entropy of component i (i = 1, …, ns, where ns is the number of components in the mixture) at standard pressure and temperature T3.

[0137] Combination Chemical equilibrium, change The value will change slightly. (Refer to...) Figure 6 Using Newton-Raphson The method is used to solve the problem, and the expanded temperature is obtained. Then, based on the expansion area ratio According to the ideal gas law, energy equation, and continuity equation:

[0138]

[0139] Where h is the enthalpy, Cp is the specific heat capacity, used to calculate the pressure after expansion. density and speed .

[0140] Combining steps The obtained parameters are used to design the tail nozzle section.

[0141] This invention covers the design of the exhaust nozzle of a slant-detonation engine, and the entire design is convergent-divergent. In the nozzle design process, the throat cross-sectional area is determined using gas properties and isentropic relationships. Characteristic lines are used for the expansion segment. To shorten the length for nozzle profile design. The exit area after the isentropic expansion module is... The export Mach number is That is, it corresponds to the fourth velocity.

[0142] Determined theoretically Given the cross-sectional area of ​​the nozzle throat, the mass flow rate at each section of the nozzle is known to be constant, and it is assumed that the airflow at the throat is at the speed of sound. Then, the continuity equation between the throat and the exit is written:

[0143]

[0144] because The equation can be simplified to:

[0145]

[0146] Based on the isentropic flow assumption:

[0147]

[0148] in .

[0149] according to Definition:

[0150]

[0151] The formula Japanese style By combining the equations, we can obtain:

[0152]

[0153] By rearranging the above equations, the area of ​​the nozzle throat can be obtained:

[0154]

[0155] In the design of the expansion section, the method of characteristics is gradually adopted to design the expansion section of the nozzle with the minimum length. Based on the known export Mach number Calculate Prandtl-Mayer at the exit horn :

[0156]

[0157] according to Calculate the maximum rotation angle of the wall Select 20 feature lines and choose the initial turning angle at the throat. and increment Increment Increase the turning angles gradually, and calculate the turning angles point by point using formulas. Angle, Mach number Mach angle The average angle is calculated, and the slope of the characteristic line and the coordinates of the points are determined based on the inlet coordinates and the centerline. Finally, a fifth-order polynomial is used for curve fitting to determine the nozzle wall profile. The expansion section wall profile under the parameters set in the embodiment is referenced. Figure 7 The resulting expansion segment is more consistent with the actual situation.

[0158] The theoretical thrust of the engine can be calculated from the parameters in the above steps.

[0159] This invention employs the momentum method to estimate engine parameters. It calculates the momentum increments flowing into and out of the engine and uses the momentum theorem to calculate the engine's thrust. The momentum flowing into and out of the engine within a given time interval is:

[0160]

[0161] Among them, P in P is the momentum of the gas flowing into the engine during time interval Δt; outρ0 is the momentum of the gas flowing out of the engine during time Δt; ρ4 is the density of the gas flowing into the engine, which is the density of the gas before the oblique shock wave compression; u0 is the velocity before the oblique shock wave compression, which is the engine inlet velocity; u4 is the velocity of the airflow after isentropic expansion, which is the velocity of the airflow at the engine outlet; A0 is the intake capture area of ​​the engine; A4 is the exhaust cross-sectional area of ​​the tail nozzle.

[0162] According to the momentum theorem:

[0163]

[0164] Since the airflow direction has changed after the oblique detonation wedge, a correction factor is introduced here. By rearranging the above equation, we can obtain the engine thrust. for:

[0165]

[0166] in The angle of the inclined plane of the combustion chamber is the angle of the detonation. Figure 1 δ in This is the combined angle of the compression angles of the two frozen shock waves in the intake section. .

[0167] Depend on:

[0168]

[0169] in, Let g be the mass flow rate of fuel per unit time, and g be the acceleration due to gravity.

[0170] Engine thrust is expressed as specific impulse. In this embodiment, the specific impulse performance relationship diagram is selected for flight altitudes of 25, 30, and 35 kilometers and flight speeds of Mach 10-17. Figure 8 This demonstrates the superior specific impulse performance of the oblique detonation engine.

[0171] Example 2

[0172] This embodiment provides a performance analysis device for a mixed-fuel multi-condition oblique detonation engine, including: an oblique shock wave compression module, a mixing module, an oblique detonation module, an isentropic expansion module, and a theoretical thrust calculation module;

[0173] The oblique shock wave compression module sets the flight altitude and speed of the aircraft, and inputs the corresponding incoming air temperature, incoming air pressure, and incoming air velocity (Mach number) according to the required flight altitude and speed.

[0174] The incoming flow is set to pass through one or more oblique shock waves, and the angle of compression of each oblique shock wave is set. The wave back parameters of the air, including the first temperature, the first pressure and the first velocity, are solved.

[0175] The mixing module sets the parameters of the mixed fuel, including the composition and ratio of the fuel, the temperature and injection speed of the fuel, and the ratio of fuel to oxidant. Combined with the wave back parameters of the air, it solves the parameters of the mixed mixture, including the second temperature, the second pressure and the second speed.

[0176] The oblique detonation module sets the angle of the combustion chamber slope or the oblique detonation wave angle, and calculates the parameters after the oblique detonation wave, including the third temperature, the third pressure and the third velocity, in combination with the parameters of the mixed mixture.

[0177] The isentropic expansion module is set to expand to a specified pressure or a specified area. Combined with the parameters after the oblique detonation wave, the parameters of the expanded gas are solved, including the fourth temperature, the fourth pressure, and the fourth velocity.

[0178] The module for calculating the theoretical thrust of a slant-detonation engine uses the momentum method to estimate the engine parameters. It calculates the momentum increments flowing into and out of the engine and then calculates the engine thrust based on the momentum theorem.

[0179] Example 3

[0180] This embodiment provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the mixed-fuel multi-condition oblique detonation engine performance analysis method as described in Embodiment 1.

[0181] Example 4

[0182] This embodiment provides a computer-readable storage medium, which includes storing a computer program or instructions that, when run, cause the method of Embodiment 1 to be executed.

Claims

1. A method for performance analysis of a mixed-fuel, multi-condition oblique detonation engine, wherein the oblique detonation engine comprises an intake section, a fuel mixing section, a combustion chamber section, and a tailpipe section, characterized in that, The method includes: Based on the sequential characteristics of the working process of the oblique detonation engine, the parameters of the oblique shock wave compression module in the intake section, the mixing module in the fuel mixing section, the oblique detonation module in the combustion chamber section, and the isentropic expansion module in the tail nozzle section are solved in sequence. By combining the corresponding parameters of each solution process, including temperature, pressure and velocity, the theoretical thrust of the oblique detonation engine is calculated, and the thrust performance including specific impulse is calculated. The parameter solution for the oblique shock wave compression module in the inlet section includes: Construct the oblique shock wave compression module, set the flight altitude and flight speed of the aircraft, and input the corresponding incoming air temperature, incoming air pressure, and incoming air velocity according to the required flight altitude and flight speed; The incoming flow is set to pass through one or more oblique shock waves, and the angle of compression of each oblique shock wave is set. The wave back parameters of the air, including the first temperature, the first pressure and the first velocity, are solved. The parameter solution for the fuel blending section mixing module includes: The mixing module is constructed, and the parameters of the mixed fuel are set, including the composition and ratio of the fuel, the temperature and injection speed of the fuel, and the ratio of fuel to oxidant. Combined with the wave back parameters of the air, the parameters of the mixed mixture are solved, including the second temperature, the second pressure and the second speed. The parameter solution for the oblique detonation module in the combustion chamber section includes: The oblique detonation module is constructed by setting the angle of the combustion chamber slope or the oblique detonation wave angle, and combining the parameters of the mixed mixture to calculate the parameters after the oblique detonation wave, including the third temperature, the third pressure and the third velocity. The solution for the isentropic expansion module parameters of the tailpipe section includes: The isentropic expansion module is constructed, and expansion to a specified pressure or area is set. Combined with the parameters after the detonation wave, the parameters of the expanded gas are solved, including the fourth temperature, the fourth pressure, and the fourth velocity.

2. The method for analyzing the performance of a mixed-fuel multi-condition oblique detonation engine according to claim 1, characterized in that, The theoretical thrust calculation of the oblique detonation engine is performed, and the thrust performance, including specific impulse, is calculated, including: The momentum method is used to estimate the parameters of the engine. The momentum increments flowing into and out of the engine are calculated, and the thrust of the engine is calculated according to the momentum theorem.

3. The hybrid fuel multi -operating mode oblique detonation engine performance analysis method of any one of claims 1-2, wherein, This also includes designing the tailpipe section, which is performed before the theoretical thrust calculation of the inclined detonation engine, specifically including: The gas after a slant detonation shock wave expands to a specified area, designed as a convergence-expansion process. CD In the design process of a nozzle, the throat cross-sectional area is determined by utilizing gas properties and isentropic relationships. A t Characteristic lines are used for the expansion segment. MOC To shorten the length for nozzle profile design; the exit area after the isentropic expansion module is A 4 The export Mach number is .

4. A performance analysis device for a mixed-fuel multi-condition oblique detonation engine, used in the performance analysis method for a mixed-fuel multi-condition oblique detonation engine as described in any one of claims 1-3, characterized in that, The device includes: a slant shock compression module, a hybrid module, a slant detonation module, an isentropic expansion module, and a theoretical thrust calculation module; The oblique shock wave compression module sets the flight altitude and speed of the aircraft, and inputs the corresponding incoming air temperature, incoming air pressure, and incoming air velocity according to the required flight altitude and speed. The incoming flow is set to pass through one or more oblique shock waves, and the angle of compression of each oblique shock wave is set. The wave back parameters of the air, including the first temperature, the first pressure and the first velocity, are solved. The mixing module sets the parameters of the mixed fuel, including the composition and ratio of the fuel, the temperature and injection speed of the fuel, and the ratio of fuel to oxidant. Combined with the wave back parameters of the air, it solves the parameters of the mixed mixture, including the second temperature, the second pressure and the second speed. The oblique detonation module sets the angle of the combustion chamber slope or the oblique detonation wave angle, and calculates the parameters after the oblique detonation wave, including the third temperature, the third pressure and the third velocity, in combination with the parameters of the mixed mixture. The isentropic expansion module is set to expand to a specified pressure or a specified area, and combined with the parameters after the detonation wave, it solves for the parameters of the expanded gas, including the fourth temperature, the fourth pressure, and the fourth velocity. The theoretical thrust calculation module for the oblique detonation engine uses the momentum method to estimate the engine parameters. It calculates the momentum increments flowing into and out of the engine and calculates the engine thrust based on the momentum theorem.

5. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the mixed-fuel multi-condition oblique detonation engine performance analysis method as described in any one of claims 1-3.

6. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions that cause a processor to execute the mixed-fuel multi-condition oblique detonation engine performance analysis method as described in any one of claims 1-3.

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