Method and device for predicting ignition delay time in self-ignition process of compressible flow field

Abstract

The invention provides a method and device for predicting ignition delay time in the self-ignition process of a compressible flow field, and relates to the technical field of aircraft ignition prediction.The method comprises the steps that the initial local temperature of the interior of a hypersonic aircraft engine before self-ignition operation is monitored in real time; self-ignition simulation is carried out through pre-selected combustion characteristic parameters of a high-compressibility combustion field, and in the self-ignition simulation process, the ignition delay time of the hypersonic aircraft is predicted based on the initial local temperature and the pre-selected combustion characteristic parameters of the high-compressibility combustion field. According to the method, the ignition delay time can be accurately predicted before ignition, so that the combustion process after ignition is better controlled, and the problems of unstable combustion and the like are reduced.

Description

Technical Field

[0001] The present application relates to the technical field of aircraft ignition prediction, and in particular to a method and device for predicting the ignition delay time of a compressible flow field self-ignition process. Background Art

[0002] In order to deal with key issues such as combustion stability and combustion efficiency in hypersonic vehicles, it is necessary to study and predict the self-ignition process in hypersonic vehicles. The main physical quantity that affects the self-ignition process due to high compressibility and turbulence is the ignition delay time. Accurately predicting the ignition delay time can better control this unstable factor.

[0003] In the related technology, some ignition delay time prediction methods do not consider the impact of turbulence on the self-ignition process, and there are problems with the applicability of this method in the hypersonic turbulent combustion process; secondly, some current results obtain the impact of turbulence on the ignition delay time by analyzing changes in scalar dissipation rate, etc., which makes it difficult to accurately predict the ignition delay time. Summary of the invention

[0004] The purpose of the present application is to provide a method and device for predicting the ignition delay time in a compressible flow field self-ignition process, so as to alleviate the above-mentioned technical problems existing in the prior art.

[0005] In a first aspect, the present invention provides a method for predicting the ignition delay time of a compressible flow field self-ignition process, comprising:

[0006] Real-time monitoring of the initial local temperature inside a hypersonic vehicle engine before auto-ignition operation;

[0007] An auto-ignition simulation is performed using pre-selected combustion characteristic parameters of a highly compressible combustion field. During the auto-ignition simulation, an ignition delay time of the hypersonic vehicle is predicted based on the initial local temperature and the pre-selected combustion characteristic parameters of the highly compressible combustion field.

[0008] In an optional embodiment, the preselected combustion characteristic parameter of the high compressibility combustion field includes a first combustion characteristic parameter;

[0009] The first combustion characteristic parameters include at least: characteristic length scale of flame diffusion, turbulence scale, activation energy, gas constant, Taylor Reynolds number, specific heat capacity, heat released per unit mass of fuel, frequency factor, oxidant mass fraction, fuel density, oxidant molar mass and Mach number related parameters.

[0010] In an optional embodiment, during the auto-ignition simulation process, predicting the ignition delay time of the hypersonic vehicle based on the initial local temperature and the combustion characteristic parameters of the pre-selected high compressibility combustion field includes:

[0011] During the self-ignition simulation, determining a target relative scale based on the characteristic length scale of the flame spread and the turbulence scale;

[0012] A first prediction model is constructed based on the initial local temperature, temperature change rate, target relative scale and gas constant, Taylor Reynolds number, specific heat capacity, heat released per unit mass of fuel, frequency factor, oxidant mass fraction, fuel density, oxidant molar mass and Mach number related parameters. The first prediction model is Among them, l FD is the characteristic length scale of flame diffusion; η is the turbulence scale; T0 is the local temperature at the initial moment; E A is the activation energy, R 0 is the gas constant; T const Re is the temperature change rate; λ is the Taylor Reynolds number; C V is the specific heat capacity; q F , A is the frequency factor, Y O is the mass fraction of oxidant, ρ F Indicates the density of the fuel, W O is the molar mass of the oxidizer; β and γ (M) are parameters and functions related to the Mach number;

[0013] The ignition delay time of the hypersonic aircraft is predicted by the first prediction model.

[0014] In an optional embodiment, the method further comprises:

[0015] According to the initial Damker number Da before ignition is successful t and the corresponding Reynolds number Re t The target relative scale is determined.

[0016] In an optional embodiment, the target relative scale is determined according to the initial Damker number and the target Reynolds number before successful ignition, and is calculated by the following formula:

[0017]

[0018] Among them, k FD is the target relative scale, Da t is the initial Damker number, Re t is the Reynolds number.

[0019] In an optional embodiment, the preselected combustion characteristic parameter of the high compressibility combustion field includes a second combustion characteristic parameter;

[0020] The second combustion characteristic parameter includes at least: flame propagation speed, Taylor Reynolds number, turbulence scale, activation energy, gas constant, specific heat capacity, heat released per unit mass of fuel, frequency factor, oxidant mass fraction, fuel density and oxidant molar mass.

[0021] In an optional embodiment, during the auto-ignition simulation process, predicting the ignition delay time of the hypersonic vehicle based on the initial local temperature and the combustion characteristic parameters of the pre-selected high compressibility combustion field includes:

[0022] A second prediction model is constructed based on the initial local temperature, temperature fluctuation parameter, flame propagation speed, Taylor Reynolds number, turbulence scale, activation energy, gas constant, specific heat capacity, heat released per unit mass of fuel, frequency factor, oxidant mass fraction, fuel density and oxidant molar mass. The second prediction model is Among them, U FD represents the flame propagation speed, T' represents the temperature fluctuation, Re λ is the Taylor Reynolds number; η is the Kolmogorov scale, T0 is the local temperature at the initial moment; E A is the activation energy, R 0 is the gas constant; C V is the specific heat capacity; q F , A is the frequency factor, Y O is the mass fraction of oxidant, ρ F Indicates the density of the fuel, W O is the molar mass of the oxidant;

[0023] The ignition delay time of the hypersonic vehicle is predicted by the second prediction model.

[0024] In a second aspect, the present invention provides an ignition delay time prediction device for a compressible flow field self-ignition process, comprising:

[0025] A pre-ignition temperature monitoring module is used to monitor in real time the initial local temperature inside the hypersonic vehicle engine before the self-ignition operation;

[0026] The ignition delay time prediction module is used to perform self-ignition simulation through pre-selected combustion characteristic parameters of a highly compressible combustion field. During the self-ignition simulation process, the ignition delay time of the hypersonic aircraft is predicted based on the initial local temperature and the pre-selected combustion characteristic parameters of the highly compressible combustion field.

[0027] In a third aspect, the present invention provides an electronic device comprising a processor and a memory, wherein the memory stores computer executable instructions that can be executed by the processor, and the processor executes the computer executable instructions to implement the method for predicting the ignition delay time of a compressible flow field self-ignition process as described in any one of the aforementioned embodiments.

[0028] In a fourth aspect, the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions. When the computer-executable instructions are called and executed by a processor, the computer-executable instructions prompt the processor to implement the method for predicting the ignition delay time of a compressible flow field self-ignition process as described in any one of the aforementioned embodiments.

[0029] The beneficial effects of the method and device for predicting the ignition delay time of the compressible flow field self-ignition process provided by the present application are as follows:

[0030] The original method of calculating the ignition delay time at low Mach numbers without considering the influence of turbulence was expanded and improved, the influence of turbulence on the process was increased, and it was simplified and organized into specific parameters; a theoretical calculation method for the relative scale of turbulence was given, and the relative scale could be reasonably estimated by the Damker number and the corresponding Reynolds number in the initial state, so as to facilitate the prediction of the final ignition delay time; a method of predicting the ignition delay time at higher Mach numbers by using low Mach number results was proposed, which further simplified the calculation process and cost of the Mach number ignition delay time. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 A flow chart of a method for predicting the ignition delay time of a compressible flow field self-ignition process provided in an embodiment of the present application;

[0033] Figure 2 A structural diagram of an ignition delay time prediction device for a compressible flow field self-ignition process provided in an embodiment of the present application;

[0034] Figure 3 A structural diagram of another device for predicting ignition delay time in a compressible flow field self-ignition process provided in an embodiment of the present application;

[0035] Figure 4 A structural diagram of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0037] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0038] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0039] The gas environment around a hypersonic vehicle is composed of extreme temperatures and ultra-high flow rates caused by air friction and shock waves. Strong aerodynamic heat loads and combustion instabilities constantly endanger the structure and thrust performance of the vehicle. The most obvious of these is the ignition and combustion process inside the engine. The combustion system of hypersonic propulsion will face a lot of difficulties related to high flow rates. High flow rates limit the residence time of chemical reactions in the combustion chamber, which will seriously affect the flame propagation process. Therefore, in the propulsion system of a hypersonic vehicle, in addition to the supersonic turbulent combustion caused by forced ignition, the stability of the combustion in the system will inevitably rely on the self-ignition process of the fuel-air mixture. The self-ignition time of most fuel-air mixtures depends largely on the temperature. In supersonic turbulent combustion, in addition to the initial high temperature of the incoming flow, it will also be affected by the local heating caused by viscous dissipation in the highly compressible turbulent field and the local compression caused by the shock wave. Since both the local dissipation and the shock wave's influence on the self-ignition are strongly nonlinear coupling problems, not only are the mechanisms of action complex, but they will also eventually affect the instability of the entire combustion system. This high-temperature and high-compressibility self-ignition problem has a non-negligible impact on the hypersonic propulsion system. Therefore, in order to address key issues such as combustion stability and combustion efficiency in hypersonic vehicles, it is necessary to conduct a detailed study of the self-ignition process in hypersonic vehicles and analyze the impact of this high compressibility and turbulence on the self-ignition process. The main physical quantity that reflects this influence is the ignition delay time. Accurately predicting the ignition delay time can better control this unstable factor.

[0040] According to previous research results, there are two main problems in the analysis of ignition delay time. On the one hand, the simplified ignition process does not consider the influence of turbulence on the ignition process, and only considers the influence of parameters such as initial temperature and pressure on the ignition process. The more common ignition delay time prediction formula obtained by thermal ignition theory. Assuming that the fuel mass fraction, temperature, etc. are almost unchanged, the influence of turbulence on the formation and propagation of the flame core is not considered. This is more applicable in premixed low-speed conditions, and a more detailed analysis is required for hypersonic turbulent combustion processes. On the other hand, since turbulence does not have a monotonous linear effect on the self-ignition process, the ignition delay time has uncertainty with changes in turbulence intensity, etc. At present, some results attribute the difference in the final ignition delay time to changes in scalar dissipation rate, etc., without a detailed analysis of the physical mechanism of turbulence affecting the self-ignition process, and a feasible method for predicting the ignition delay time in such a highly compressible flow field.

[0041] In summary, the shortcomings of the existing research methods are mainly in two parts. First, some existing simplified methods do not consider the influence of turbulence on the self-ignition process, and the applicability of this method in the hypersonic turbulent combustion process is problematic; second, some current results obtain the influence of turbulence on the ignition delay time by analyzing the changes in scalar dissipation rate, etc., which makes it difficult to accurately predict the ignition delay time.

[0042] Based on this, the embodiments of the present application provide a method and device for predicting the ignition delay time in the self-ignition process of a compressible flow field, which can accurately predict the ignition delay time before ignition, so as to better control the combustion process after ignition and reduce the occurrence of problems such as unstable combustion.

[0043] The present application embodiment provides a method for predicting the ignition delay time of a compressible flow field self-ignition process, see Figure 1 As shown, the method mainly includes the following steps:

[0044] Step S110, real-time monitoring of the initial local temperature inside the hypersonic aircraft engine before the self-ignition operation.

[0045] The above-mentioned initial local temperature may include the local temperature of the internal ignition device of the hypersonic aircraft engine, and the local temperature may be measured by a temperature sensor or other temperature measuring device arranged at a corresponding position of the internal ignition device of the hypersonic aircraft engine.

[0046] In one embodiment, real-time monitoring may be monitoring of a preset period of time before the self-ignition operation. For example, a certain time interval may be selected as the monitoring period, and the local temperature of the internal ignition device of the hypersonic aircraft engine before ignition may be accurately obtained by periodically performing temperature monitoring.

[0047] Step S120, performing a self-ignition simulation using pre-selected combustion characteristic parameters of a highly compressible combustion field. During the self-ignition simulation, the ignition delay time of the hypersonic vehicle is predicted based on the initial local temperature and the pre-selected combustion characteristic parameters of the highly compressible combustion field.

[0048] In one embodiment, in order to accurately simulate the self-ignition, the combustion field can be analyzed locally in advance. Based on the hot ignition theory, assuming a single-step irreversible reaction:

[0049]

[0050] Among them, F represents fuel, O represents oxidant, P represents reaction product, k F is the reaction rate constant. Combined with the component equation, we know that:

[0051]

[0052] where ω F is the fuel reaction rate, w O is the oxidant reaction rate, C F is the fuel concentration, C O is the oxidant concentration. A is the frequency factor, E A is the activation energy, R 0 is the gas constant, T is the temperature. Parameter ρ is the density of the mixed gas, Y F is the fuel mass fraction, Y O is the mass fraction of oxidant, W F is the fuel molar mass, W O is the molar mass of the oxidant.

[0053] From the fuel concentration formula, we can know that:

[0054]

[0055] Therefore, combining the above formulas, we can get:

[0056]

[0057] Combining the energy equation, we know that:

[0058]

[0059] Among them, q F It represents the heat released per unit mass of fuel. Combining Formula 2 and Formula 6, we can get:

[0060]

[0061] Parameter ρ F Indicates the density of the fuel, specific heat capacity CV is a constant. In the initial stage of ignition, since the temperature change is small, it can be assumed that:

[0062] T=T0(1-εy),ε<<1,y~O(1) (8)

[0063] Where T0 is the local temperature at the initial moment. Therefore, it can be concluded that:

[0064]

[0065] Combined with the initial condition (y(t=0)=0), the ignition time τ can be derived i The solution is:

[0066]

[0067] The local fuel density ρ in the turbulent combustion field F Dimensional analysis is carried out, and the physical processes involved mainly include thermodynamics, chemical reaction kinetics, mass transfer and fluid dynamics, etc. These processes are significantly affected by the interaction between chemical reactions and turbulence. Local small flames consume fuel and release heat, changing the thermodynamic state, which in turn affects turbulence. The turbulent vortex structure affects flame propagation and local mass transport processes, resulting in changes in local chemical reaction kinetics. Since the focus is on analyzing local fuel density, the results of local chemical reaction kinetics and flame diffusion are all related to the process of fuel consumption through chemical reactions, the complex chemical reaction kinetics parameters are simplified to characterize the flame diffusion process. By comprehensively analyzing the characteristic parameters related to the turbulent vortex structure, the dimensional analysis expression of the local fuel density can be obtained. The main physical processes are analyzed and the characteristic parameters are selected as follows:

[0068] (a) Diffusion effect: temperature-dependent diffusion coefficient D and local temperature T;

[0069] (b) Flame diffusion effect: characteristic length scale of flame diffusion l FD ;

[0070] (c) Turbulence effects: turbulent pulsation velocity u′, turbulent dissipation rate ε, turbulence integral scale L, kinematic viscosity coefficient v;

[0071] (d) Initial conditions: density ρ0 and temperature T0 at the initial moment.

[0072] ρ F =f(D, T, l FD ,u′,ε,L,ρ0,T0,ν) (11)

[0073] Select ε, L, ρ0, T as characteristic parameters:

[0074]

[0075] Some parameters also satisfy the following relationship:

[0076]

[0077] ρ=ρ0+dρ,T=T0+dT (14)

[0078]

[0079] In the formula, η is the Kolmogorov scale. According to Barenblatt's incomplete similarity theory, it is assumed that in compressible turbulence, the local fuel density and the parameter Not exactly similar, but similar to the Mach number M or Taylor Reynolds number Re λ Not similar:

[0080]

[0081] Where β and γ (M) are parameters and functions related to the Mach number. It can be inferred that in a turbulent field with relatively high compressibility, due to the interaction between turbulence and chemical reactions, the parameter A′ is affected not only by the Mach number, but also by the turbulence scale and flame diffusion scale:

[0082]

[0083] In addition, from the Zeldovich relationship before ignition, we know that:

[0084]

[0085] Where U FD represents the flame propagation speed, and ξ is the normal spatial coordinate of the reaction front. In addition, the above formula can be equivalently expressed as The relationship between ignition delay time and temperature is:

[0086]

[0087] According to the temperature derivative approximation method, it can be obtained that:

[0088]

[0089] Among them, l λ represents the Taylor scale of turbulence, and T′ represents the temperature fluctuation. Combining these two equations, we can get:

[0090]

[0091] The denominator can be converted to Since the temperature change is small before successful ignition, the rate of change over time can be expressed as a relatively small constant T const To approximate.

[0092] The expression of the final ignition delay time is as follows:

[0093]

[0094] This result shows that, unlike the simple thermal ignition theory, in a highly compressible combustion field, the ignition delay time is affected not only by the initial temperature but also by the relative scale. impact.

[0095] The dimensionless parameter Damke number Da that characterizes the relative size of the flame diffusion characteristic time and the turbulent flow characteristic time during the ignition process t and the corresponding Reynolds number Re t (Inertial force and viscous force in flow field) It can be known that:

[0096] Da t =τ t / τ c =(L ∈ / u rms ) / (l FD / U FD ) (twenty four)

[0097] Re t =u rms L ∈ / ν=(u rms / U FD )(L ∈ / l FD ) (25)

[0098] where τ t is the characteristic time of turbulent flow, τ c Flame spread characteristic time. L ∈ is the turbulence integral scale, u rms is the root mean square of the turbulent velocity, where v is the kinematic viscosity, and satisfies l FD =v / U FD Combining (24) and (25), we can know that:

[0099]

[0100] In addition, the relationship between the various scales of turbulence shows that:

[0101]

[0102] Set relative scale From formula (26), we can know:

[0103]

[0104] So the relative scale The initial Damker number Da before ignition is successful t and the corresponding Reynolds number Re t To make a theoretical estimate:

[0105]

[0106] Therefore, all variables involved in the final ignition delay time can be estimated by the initial parameters.

[0107] Based on the research process of the above inventors, the embodiments of the present application provide two embodiments for determining the ignition delay time, which are described below respectively.

[0108] In one embodiment, the preselected combustion characteristic parameters of the high compressibility combustion field include first combustion characteristic parameters;

[0109] The first combustion characteristic parameters include at least: characteristic length scale of flame diffusion, turbulence scale, activation energy, gas constant, Taylor Reynolds number, specific heat capacity, heat released per unit mass of fuel, frequency factor, oxidant mass fraction, fuel density, oxidant molar mass and Mach number related parameters.

[0110] Corresponding to the first combustion characteristic parameter, in the auto-ignition simulation process, predicting the ignition delay time of the hypersonic vehicle based on the initial local temperature and the pre-selected combustion characteristic parameter of the high compressibility combustion field may include the following steps 1-1 to 1-3:

[0111] Step 1-1, during the self-ignition simulation, determining the target relative scale based on the characteristic length scale of flame diffusion and the turbulence scale;

[0112] Step 1-2, constructing a first prediction model based on initial local temperature, temperature change rate, target relative scale and gas constant, Taylor Reynolds number, specific heat capacity, heat released per unit mass of fuel, frequency factor, oxidant mass fraction, fuel density, oxidant molar mass and Mach number related parameters. The first prediction model is Among them, l FD is the characteristic length scale of flame diffusion; η is the turbulence scale; T0 is the local temperature at the initial moment; E A is the activation energy, R 0 is the gas constant; T const Re is the temperature change rate; λ is the Taylor Reynolds number; C V is the specific heat capacity; q F , A is the frequency factor, Y Ois the mass fraction of oxidant, ρ F Indicates the density of the fuel, W O is the molar mass of the oxidizer; β and γ (M) are parameters and functions related to the Mach number;

[0113] Step 1-3, predicting the ignition delay time of the hypersonic vehicle by using a first prediction model.

[0114] In an optional embodiment, the method further comprises:

[0115] According to the initial Damker number Da before ignition is successful t and the corresponding Reynolds number Re t Determine the relative size of the target.

[0116] In an optional embodiment, the target relative scale is determined according to the initial Damker number and the target Reynolds number before successful ignition, and is calculated by the following formula:

[0117]

[0118] Among them, k FD is the target relative scale, Da t is the initial Damker number, Re t is the Reynolds number.

[0119] In summary, since the above-mentioned method of calculating the ignition delay time is mainly affected by temperature, relative scale, Mach number, etc., in order to further simplify the prediction process and calculation cost, the self-ignition of a relatively simple low Mach number can be experimentally or numerically simulated to ensure that the parameters such as temperature and equivalence ratio in the initial conditions remain unchanged, and only the initial Mach number is changed. It can be seen from the first prediction model that the parameters affected by temperature are basically unchanged, and the main influence is the relative scale. Therefore, the ignition delay time of a higher Mach number can be predicted by combining the low Mach number ignition delay time with different relative scales, which can further simplify the calculation process of the ignition delay time prediction.

[0120] In another embodiment, the combustion characteristic parameters of the pre-selected high compressibility combustion field include second combustion characteristic parameters; the second combustion characteristic parameters include at least: flame propagation speed, Taylor Reynolds number, turbulence scale, activation energy, gas constant, specific heat capacity, heat released per unit mass of fuel, frequency factor, oxidizer mass fraction, fuel density and oxidizer molar mass.

[0121] Corresponding to the above-mentioned second combustion characteristic parameter, in the self-ignition simulation process, predicting the ignition delay time of the hypersonic aircraft based on the initial local temperature and the pre-selected combustion characteristic parameter of the high compressibility combustion field may include the following steps 2-1 and 2-2:

[0122] Step 2-1, constructing a second prediction model based on the initial local temperature, temperature fluctuation parameter, flame propagation speed, Taylor Reynolds number, turbulence scale, activation energy, gas constant, specific heat capacity, heat released per unit mass of fuel, frequency factor, oxidant mass fraction, fuel density and oxidant molar mass. The second prediction model is Among them, U FD represents the flame propagation speed, T' represents the temperature fluctuation, Re λ is the Taylor Reynolds number; η is the Kolmogorov scale, T0 is the local temperature at the initial moment; E A is the activation energy, R 0 is the gas constant; C V is the specific heat capacity; q F , A is the frequency factor, Y o is the mass fraction of oxidant, ρ F Indicates the density of the fuel, W o is the molar mass of the oxidant;

[0123] Step 2-2, predicting the ignition delay time of the hypersonic vehicle by using a second prediction model.

[0124] In summary, the above-mentioned ignition delay time prediction method adopted in the embodiment of the present application combines dimensional analysis with similarity theory, expands and improves the original low Mach number ignition delay time method that does not consider the influence of turbulence, increases the influence of turbulence on the process, and simplifies it into specific parameters; a theoretical calculation method for the relative scale of turbulence is given, and the relative scale can be reasonably estimated by the Damkel number and the corresponding Reynolds number in the initial state, so as to facilitate the prediction of the final ignition delay time; a method for predicting the ignition delay time of a higher Mach number by using the low Mach number results is proposed, which further simplifies the Mach number ignition delay time calculation process and calculation cost.

[0125] Based on the above method embodiment, the present application embodiment also provides a compressible flow field self-ignition process ignition delay time prediction device, see Figure 2 As shown, the device mainly includes the following parts:

[0126] The pre-ignition temperature monitoring module 210 is used to monitor in real time the initial local temperature inside the hypersonic aircraft engine before the self-ignition operation;

[0127] The ignition delay time prediction module 220 is used to perform auto-ignition simulation using pre-selected combustion characteristic parameters of a highly compressible combustion field. During the auto-ignition simulation, the ignition delay time of the hypersonic vehicle is predicted based on the initial local temperature and the pre-selected combustion characteristic parameters of the highly compressible combustion field.

[0128] In a feasible embodiment, the preselected combustion characteristic parameters of the high compressibility combustion field include first combustion characteristic parameters;

[0129] The first combustion characteristic parameters include at least: characteristic length scale of flame diffusion, turbulence scale, activation energy, gas constant, Taylor Reynolds number, specific heat capacity, heat released per unit mass of fuel, frequency factor, oxidant mass fraction, fuel density, oxidant molar mass and Mach number related parameters.

[0130] In a feasible implementation manner, the ignition delay time prediction module 220 is used to:

[0131] During the self-ignition simulation, the target relative scale is determined based on the characteristic length scale of flame spread and the turbulence scale;

[0132] The first prediction model is constructed based on the initial local temperature, temperature change rate, target relative scale and gas constant, Taylor Reynolds number, specific heat capacity, heat released per unit mass of fuel, frequency factor, oxidizer mass fraction, fuel density, oxidizer molar mass and Mach number related parameters. The first prediction model is Among them, l FD is the characteristic length scale of flame diffusion; η is the turbulence scale; T0 is the local temperature at the initial moment; E A is the activation energy, R 0 is the gas constant; T const Re is the temperature change rate; λ is the Taylor Reynolds number; C V is the specific heat capacity; q F , A is the frequency factor, Y O is the mass fraction of oxidant, ρ F Indicates the density of the fuel, W O is the molar mass of the oxidizer; β and γ (M) are parameters and functions related to the Mach number;

[0133] The ignition delay time of the hypersonic vehicle is predicted by the first prediction model.

[0134] In one possible implementation, see Figure 3 As shown, the above device also includes: a relative scale determination module, which is used to:

[0135] According to the initial Damker number Da before ignition is successful t and the corresponding Reynolds number Re t Determine the relative size of the target.

[0136] In a feasible implementation manner, the relative scale determination module is used to calculate using the following formula:

[0137]

[0138] Among them, k FD is the target relative scale, Da t is the initial Damker number, Re t is the Reynolds number.

[0139] In a feasible embodiment, the preselected combustion characteristic parameters of the high compressibility combustion field include a second combustion characteristic parameter;

[0140] The second combustion characteristic parameter includes at least: flame propagation speed, Taylor Reynolds number, turbulence scale, activation energy, gas constant, specific heat capacity, heat released per unit mass of fuel, frequency factor, oxidant mass fraction, fuel density and oxidant molar mass.

[0141] In a feasible implementation manner, the ignition delay time prediction module 220 is used to:

[0142] The second prediction model is constructed based on the initial local temperature, temperature fluctuation parameters, flame propagation speed, Taylor Reynolds number, turbulence scale, activation energy, gas constant, specific heat capacity, heat released per unit mass of fuel, frequency factor, oxidant mass fraction, fuel density and oxidant molar mass. The second prediction model is Among them, U FD represents the flame propagation speed, T' represents the temperature fluctuation, Re λ is the Taylor Reynolds number; η is the Kolmogorov scale, T0 is the local temperature at the initial moment; E A is the activation energy, R 0 is the gas constant; C V is the specific heat capacity; q F , A is the frequency factor, Y O is the mass fraction of oxidant, ρ F Indicates the density of the fuel, W O is the molar mass of the oxidant;

[0143] The ignition delay time of the hypersonic vehicle is predicted by the second prediction model.

[0144] The ignition delay time prediction device for the self-ignition process of a compressible flow field provided in the embodiment of the present application has the same implementation principle and technical effects as those of the aforementioned method embodiment. For the sake of brief description, for parts not mentioned in the embodiment of the ignition delay time prediction device for the self-ignition process of a compressible flow field, reference may be made to the corresponding contents in the aforementioned method embodiment for predicting the ignition delay time for the self-ignition process of a compressible flow field.

[0145] The present application also provides an electronic device, such as Figure 4As shown, it is a schematic diagram of the structure of the electronic device, wherein the electronic device 100 includes a processor 41 and a memory 40, the memory 40 stores computer executable instructions that can be executed by the processor 41, and the processor 41 executes the computer executable instructions to implement any of the above-mentioned methods for predicting the ignition delay time of the compressible flow field self-ignition process.

[0146] exist Figure 4 In the illustrated embodiment, the electronic device further includes a bus 42 and a communication interface 43 , wherein the processor 41 , the communication interface 43 and the memory 40 are connected via the bus 42 .

[0147] Among them, the memory 40 may include a high-speed random access memory (RAM), and may also include a non-volatile memory (non-volatile memory), such as at least one disk storage. The communication connection between the system network element and at least one other network element is realized through at least one communication interface 43 (which can be wired or wireless), and the Internet, wide area network, local area network, metropolitan area network, etc. can be used. The bus 42 can be an ISA (Industry Standard Architecture) bus, a PCI (Peripheral Component Interconnect) bus or an EISA (Extended Industry Standard Architecture) bus, etc. The bus 42 can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 4 Only one bidirectional arrow is used in the diagram, but this does not mean that there is only one bus or only one type of bus.

[0148] The processor 41 may be an integrated circuit chip with signal processing capabilities. In the implementation process, each step of the above method can be completed by the hardware integrated logic circuit or software instructions in the processor 41. The above processor 41 can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor. The steps of the method disclosed in the embodiment of the present application can be directly embodied as a hardware decoding processor to execute, or the hardware and software modules in the decoding processor can be executed. The software module can be located in a mature storage medium in the field such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory, or an electrically erasable programmable memory, a register, etc. The storage medium is located in the memory, and the processor 41 reads the information in the memory and completes the steps of the ignition delay time prediction method for the compressible flow field self-ignition process in the aforementioned embodiment in combination with its hardware.

[0149] An embodiment of the present application also provides a computer-readable storage medium, which stores computer-executable instructions. When the computer-executable instructions are called and executed by a processor, the computer-executable instructions prompt the processor to implement the above-mentioned method for predicting the ignition delay time of the compressible flow field self-ignition process. The specific implementation can be found in the aforementioned method embodiment, which will not be repeated here.

[0150] The computer program product of the method and device for predicting the ignition delay time of the compressible flow field self-ignition process provided in the embodiments of the present application includes a computer-readable storage medium storing program code. The instructions included in the program code can be used to execute the method in the previous method embodiment. The specific implementation can be found in the method embodiment, which will not be repeated here.

[0151] Unless otherwise specifically stated, the relative steps, numerical expressions and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0152] If the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a non-volatile computer-readable storage medium that is executable by a processor. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the various embodiments of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, and other media that can store program codes.

[0153] In the description of the present application, it should be noted that the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0154] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for predicting the ignition delay time of a compressible flow field self-ignition process, characterized in that: include: Real-time monitoring of the initial local temperature inside a hypersonic vehicle engine before auto-ignition operation; An auto-ignition simulation is performed using pre-selected combustion characteristic parameters of a highly compressible combustion field. During the auto-ignition simulation, an ignition delay time of the hypersonic vehicle is predicted based on the initial local temperature and the pre-selected combustion characteristic parameters of the highly compressible combustion field.

2. The method for predicting the ignition delay time of the compressible flow field self-ignition process according to claim 1, characterized in that: The pre-selected combustion characteristic parameters of the high compressibility combustion field include first combustion characteristic parameters; The first combustion characteristic parameters include at least: characteristic length scale of flame diffusion, turbulence scale, activation energy, gas constant, Taylor Reynolds number, specific heat capacity, heat released per unit mass of fuel, frequency factor, oxidant mass fraction, fuel density, oxidant molar mass and Mach number related parameters.

3. The method for predicting the ignition delay time of the compressible flow field self-ignition process according to claim 2, characterized in that: In the auto-ignition simulation process, the ignition delay time of the hypersonic vehicle is predicted based on the initial local temperature and the combustion characteristic parameters of the pre-selected high compressibility combustion field, including: During the self-ignition simulation, determining a target relative scale based on the characteristic length scale of the flame spread and the turbulence scale; A first prediction model is constructed based on the initial local temperature, temperature change rate, target relative scale and gas constant, Taylor Reynolds number, specific heat capacity, heat released per unit mass of fuel, frequency factor, oxidant mass fraction, fuel density, oxidant molar mass and Mach number related parameters. The first prediction model is Among them, l FD is the characteristic length scale of flame diffusion; η is the turbulence scale; T0 is the local temperature at the initial moment; E A is the activation energy, R 0 is the gas constant; T const Re is the temperature change rate; λ is the Taylor Reynolds number; C V is the specific heat capacity; q F It indicates the heat released per unit mass of fuel; A is the frequency factor, Y O is the mass fraction of oxidant, ρ F Indicates the density of the fuel, W O is the molar mass of the oxidizer; β and γ (M) are parameters and functions related to the Mach number; The ignition delay time of the hypersonic aircraft is predicted by the first prediction model.

4. The method for predicting the ignition delay time of the compressible flow field self-ignition process according to claim 3, characterized in that: The method further comprises: According to the initial Damker number Da before ignition is successful t and the corresponding Reynolds number Re t The target relative scale is determined.

5. The method for predicting the ignition delay time of the compressible flow field self-ignition process according to claim 4, characterized in that: The target relative scale is determined based on the initial Damker number and the target Reynolds number before successful ignition, and is calculated using the following formula: Among them, k FD is the target relative scale, Da t is the initial Damker number, Re t is the Reynolds number.

6. The method for predicting the ignition delay time of the compressible flow field self-ignition process according to claim 1, characterized in that: The preselected combustion characteristic parameters of the high compressibility combustion field include second combustion characteristic parameters; The second combustion characteristic parameter includes at least: flame propagation speed, Taylor Reynolds number, turbulence scale, activation energy, gas constant, specific heat capacity, heat released per unit mass of fuel, frequency factor, oxidant mass fraction, fuel density and oxidant molar mass.

7. The method for predicting the ignition delay time of the compressible flow field self-ignition process according to claim 6, characterized in that: In the auto-ignition simulation process, the ignition delay time of the hypersonic vehicle is predicted based on the initial local temperature and the combustion characteristic parameters of the pre-selected high compressibility combustion field, including: A second prediction model is constructed based on the initial local temperature, temperature fluctuation parameter, flame propagation speed, Taylor Reynolds number, turbulence scale, activation energy, gas constant, specific heat capacity, heat released per unit mass of fuel, frequency factor, oxidant mass fraction, fuel density and oxidant molar mass. The second prediction model is Among them, U FD represents the flame propagation speed, T' represents the temperature fluctuation, Re λ is the Taylor Reynolds number; η is the Kolmogorov scale, T0 is the local temperature at the initial moment; E A is the activation energy, R 0 is the gas constant; C V is the specific heat capacity; q F It indicates the heat released per unit mass of fuel; A is the frequency factor, Y O is the mass fraction of oxidant, ρ F Indicates the density of the fuel, W O is the molar mass of the oxidant; The ignition delay time of the hypersonic vehicle is predicted by the second prediction model.

8. A device for predicting ignition delay time in a compressible flow field self-ignition process, characterized in that: include: A pre-ignition temperature monitoring module is used to monitor in real time the initial local temperature inside the hypersonic vehicle engine before the self-ignition operation; The ignition delay time prediction module is used to perform self-ignition simulation through pre-selected combustion characteristic parameters of a highly compressible combustion field. During the self-ignition simulation process, the ignition delay time of the hypersonic aircraft is predicted based on the initial local temperature and the pre-selected combustion characteristic parameters of the highly compressible combustion field.

9. An electronic device, characterized in that: It comprises a processor and a memory, wherein the memory stores computer executable instructions that can be executed by the processor, and the processor executes the computer executable instructions to implement the method for predicting the ignition delay time of a compressible flow field self-ignition process according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions. When the computer-executable instructions are called and executed by the processor, the computer-executable instructions prompt the processor to implement the method for predicting the ignition delay time of the compressible flow field self-ignition process according to any one of claims 1 to 7.

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