A method for rapid evaluation of overall performance of rotating detonation engine

Abstract

The application discloses a kind of quick evaluation methods of rotating detonation ramjet overall performance, the calculation method is smoothly started, and the input parameters such as flight condition, engine key geometric parameter and inlet characteristic parameter are used as pre-constraint condition to ram intake, flow matching, engine stable work, based on chemical reaction dynamics calculation airflow along the way variation and detonation combustion process. Through the iteration calculation of combustion chamber entrance choke ratio, combustion chamber and isolation section pressure matching, realize the conservation of aerodynamic parameter and thermodynamic parameter, and there is loss factor correction calculation result. Finally, engine overall performance parameters (thrust, specific impulse) can be obtained, and detailed aerodynamic parameters and thermodynamic parameters of main internal flow section. The application is fast and reliable in calculation, and can obtain engine component performance parameters, which is helpful for engineering application of rotating detonation ramjet, and provides technical support for hypersonic vehicle and its propulsion technology performance analysis.

Description

Technical Field

[0001] The present invention belongs to the technical field of engine design, and in particular relates to a method for quickly evaluating the overall performance of a rotating detonation ramjet engine. Background Art

[0002] Hypersonic aircraft are the future development direction of military and civilian aircraft. In the speed range of Mach>2, the advantages of traditional turbine aircraft engines are gradually declining. Currently, ramjet engines are the primary key technology for realizing hypersonic aircraft and are also one of the cutting-edge technology fields that countries around the world have been competing to develop since the 21st century.

[0003] Compared to traditional ramjets, rotating detonation combustion offers a wider operating range and greater stability due to its wide adaptability to incoming flows. Unlike ramjets, which use bulk combustion, rotating detonation engines utilize surface combustion, allowing complete combustion and heat release within a very short combustion chamber. Furthermore, dynamic propagation along a circumferential direction perpendicular to the flow direction enhances combustion stability, effectively broadening the operating range of ramjets employing rotating detonation combustion chambers. Furthermore, detonation combustion offers the advantages of self-pressurization and a high heat release rate, enabling complete heat release within a simpler combustion chamber. This significantly mitigates the pressure loss caused by complex internal flow fields and offers advantages for lightweight engine designs. Replacing the existing ramjets' combustion mode with rotating detonation may be the future direction of ramjets. Currently, research on air-breathing detonation engines focuses primarily on oblique detonation engines, while relatively little research has been conducted on rotating detonation engines.

[0004] For engine development tasks, quickly and effectively carrying out conceptual design and determining the corresponding technical indicators and sub-component configurations in the preliminary design demonstration stage can greatly shorten the development cycle and reduce development risks. Therefore, it is very necessary to establish a convenient and reliable method for rapid evaluation of the overall performance parameters of rotating detonation ramjet engines for the development of rotating detonation ramjet engines. Summary of the Invention

[0005] To support the design and development of rotating detonation ramjet engines, this paper presents a rapid evaluation method for the overall performance of rotating detonation ramjet engines, taking into account the complex flow processes within them and the issue of inlet-exit flow matching. This rapid evaluation method considers the variable specific heat ratio characteristics of the high-speed incoming flow (air), fuel, and combustion products, as well as the freezing / equilibrium state of the fuel / air mixture during mixing and ignition, during the engine's axial flow. It also accounts for actual flow losses at the engine subcomponent level, modifying the calculated flow cross-sections within the engine by setting loss factors to ensure that the calculated overall engine performance parameters are closer to reality.

[0006] The technical solution to achieve the present invention is: a method for rapidly evaluating the overall performance of a rotating detonation ramjet engine, comprising the following steps:

[0007] Step 1: Input initial parameters according to design requirements.

[0008] Step 2: Based on the initial parameters, calculate the incoming gas parameters and the inlet outlet gas parameters.

[0009] Step 3: Based on the inlet duct outlet gas parameters and the first simplified assumption, calculate the isolation section outlet gas parameters.

[0010] Step 4: Based on the gas parameters at the isolation section outlet and the initial fuel state, calculate the gas parameters at the fuel injection and mixing section outlet.

[0011] Step 5: Based on the third simplified assumption, a rotating detonation combustion chamber model is constructed, and the combustion chamber outlet gas parameters under the conditions of stable rotating detonation and forward matching are calculated from the mixing section outlet gas parameters.

[0012] Step 6: Establish a tail nozzle adaptive working model and calculate the tail nozzle outlet gas parameters based on the combustion chamber outlet gas parameters.

[0013] Step 7: Calculate the overall engine performance parameters based on the inlet inlet related parameters, tail nozzle outlet related parameters and fuel flow rate.

[0014] Compared with the prior art, the present invention has the following significant advantages: (1) the present invention only needs to use the flight conditions of the rotating detonation ramjet engine, the engine geometric parameters and the inlet duct characteristic parameters as input parameters to quickly estimate the overall performance parameters of the engine; at the same time, the present invention fully considers the variable specific heat of the flow field in the engine and can correct the calculation results in combination with the flow loss of the sub-components, so that the calculated flow parameters of the engine internal flow section are more reliable and can be used as one of the preliminary indicators for the development of engine sub-components.

[0015] (2) Compared with traditional constant specific heat ratio calculation models and empirical formula calculation models, the present invention establishes a calculation and analysis method for the performance of rotating detonation ramjet engine components and the overall performance. The calculation process is simple and does not rely on complex mathematical derivations. It is suitable for parameter selection and iterative optimization in the early stages of rotating detonation ramjet engine design, as well as preliminary engineering estimates. In addition, the loss factor can be corrected based on the results of sub-component experiments and numerical simulations, making it possible to quickly, conveniently and reliably obtain more realistic overall engine performance parameter estimates, which can provide support for the performance analysis of hypersonic vehicles and their propulsion technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the key cross section of the engine involved in the present invention.

[0017] Figure 2 It is a schematic diagram of the flow in the isolation section of the engine involved in the present invention.

[0018] Figure 3 It is a calculation flow chart of the present invention.

[0019] Figure 4 Schematic diagram for comparing calculation results of the sub-component model of the present invention.

[0020] Figure 1 、 Figure 2 The key sections of the engine internal flow are marked as follows: 0—incoming atmosphere, 1—inlet duct inlet, 2—inlet duct outlet / isolator inlet, 32—normal shock wave front, 34—normal shock wave back, 4—isolator outlet, 4mix—fuel mixing / combustion chamber inlet, 5pre—detonation wave front, shock—detonation wave back, 6—combustion chamber outlet, 7—tail nozzle outlet. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0023] In addition, the terms "first," "second," and so on, used in this disclosure are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features being referenced. Thus, features specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this disclosure, "plurality" means at least two, such as two or three, unless otherwise specifically defined.

[0024] In the present invention, unless otherwise specified or limited, the terms "connection" and "fixation" should be understood in a broad sense. For example, "fixation" can refer to fixed connection, detachable connection, or integration; "connection" can refer to mechanical connection or electrical connection. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0025] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in this field can implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0026] The following will further introduce the specific implementation methods, as well as the technical difficulties and inventive points of this invention in combination with this design example.

[0027] Combine Figures 1 to 4 The method for rapidly evaluating the overall performance of a rotating detonation ramjet engine according to the present invention comprises the following steps:

[0028] Step 1: Input initial parameters according to design requirements.

[0029] The initial parameters include: flight conditions (including flight altitude H, flight Mach number Ma0), key engine geometric parameters (including inlet capture area A1, isolation section expansion ratio a, annular combustion chamber inner diameter d1, annular combustion chamber outer diameter d2, annular combustion chamber length l, tail nozzle outlet area A7), inlet characteristic parameters (including inlet pressure ratio π, inlet total pressure recovery coefficient σ, inlet temperature rise ratio Ψ, inlet flow coefficient Mach number at the inlet exit ex ), equivalence ratio (φ) and initial fuel state (including fuel injection pressure P f , fuel injection temperature T f ).

[0030] Step 2: Calculate the incoming gas parameters and the inlet and outlet gas parameters based on the initial parameters:

[0031] The incoming gas parameters include incoming gas flow parameters, incoming gas physical parameters and incoming gas state parameters. The inlet duct outlet gas parameters include inlet duct outlet gas flow parameters, inlet duct outlet gas physical parameters and inlet duct outlet gas state parameters.

[0032] According to the flight altitude H and the flight Mach number Ma0, the flow parameters of the incoming gas (including the total temperature T t0 , total incoming flow pressure P t0 ), physical properties of incoming gas (i.e., specific heat ratio γ0 of incoming gas) and state parameters of incoming gas (including static temperature T0 of incoming gas, static pressure P0 of incoming gas, and density ρ0 of incoming gas).

[0033] The intake duct capture flow rate can be calculated based on the intake duct capture area A1

[0034] Combined with the inlet characteristic parameters, the inlet outlet gas flow parameters (including the inlet outlet Mach number Ma2 (Ma2=Maex ) The sonic velocity c2 at the inlet duct outlet, the total temperature T at the inlet duct outlet t2 , and the total pressure P at the inlet duct outlet t2 ) The gas physical property parameters at the inlet duct outlet (i.e., the specific heat ratio γ2 at the inlet duct outlet), the gas state parameters at the inlet duct outlet (including the static temperature T2 at the inlet duct outlet, the static pressure P2 at the inlet duct outlet, and the density ρ2 at the inlet duct outlet), and the actual capture flow rate of the inlet duct Based on the mass conservation, further calculate the flow area A2 at the inlet duct outlet.

[0035] Step 3: According to the gas parameters at the inlet duct outlet, combined with the first simplified assumption, calculate the gas parameters at the outlet of the isolator.

[0036] The gas parameters at the outlet of the isolator include the gas flow parameters at the outlet of the isolator, the gas physical property parameters at the outlet of the isolator, and the gas state parameters at the outlet of the isolator.

[0037] It is recorded in the article "Numerical Simulation of the Influence of Ram Rotating Detonation on the Incoming Flow" that inside the isolator, under the interaction of the reverse pressure of the rotating detonation wave and the incoming flow, the shock wave train structure is complex, consisting of multiple oblique shock waves, the reflection wave system, and the trailing normal shock wave. The specific content of the first simplified assumption is as follows: The losses caused by a normal shock wave and the entropy loss between adjacent aerodynamic cross-sections to the shock wave train are comprehensively equivalent, and the loss factor η iso Generally takes values from 0 to 0.15. And based on this, the flow inside the isolator is divided into two parts: before the normal shock wave and after the normal shock wave.

[0038] Step 3.1: According to the gas parameters at the inlet duct outlet, combined with the initial value A' of the position of the normal shock wave 32 , calculate the gas parameters of the flow before the normal shock wave inside the isolator.

[0039] Randomly set the initial value A' of the position of the normal shock wave 32 (A2 < A' 32 < A4, = a·A2), where A2 is the outlet area of the inlet duct, A4 is the outlet area of the isolator, and a is the area expansion ratio of the isolator. Combining the gas parameters at the inlet duct outlet obtained in Step 2 as the input parameters of the isolator, calculate the acceleration and expansion of the supersonic incoming flow to the gas parameters before the normal shock wave, specifically including: the gas flow parameters before the normal shock wave (including the Mach number Ma before the normal shock wave 32 , the sonic velocity c before the normal shock wave 32 , the total temperature T before the normal shock wave t32 , the total pressure P before the normal shock wave t32 ), the gas physical property parameters before the normal shock wave (i.e., the specific heat ratio γ before the normal shock wave 32 ), and the gas state parameters before the normal shock wave (including the static temperature T before the normal shock wave 32 , the static pressure P before the normal shock wave 32 , and the density ρ before the normal shock wave 32 ).

[0040] The main calculation process is as follows:

[0041]

[0042]

[0043]

[0044]

[0045] Step 3.2: Based on the gas parameters before the normal shock wave in the isolation section, combined with the normal shock wave relationship and the isentropic expansion flow calculation formula, the gas parameters at the isolation section outlet are finally calculated.

[0046] According to the normal shock wave relationship, the gas parameters after the normal shock wave (including the Mach number Ma 34 , the speed of sound after the normal shock wave c 34 , total temperature after normal shock wave T t34 , total pressure after the positive shock wave P t34 , specific heat ratio γ after normal shock wave 34 , static temperature after normal shock wave T 34 , static pressure after normal shock wave P 34 , density after normal shock wave ρ 34 Then, according to the isentropic flow relationship, the gas parameters at the isolation section outlet (including the isolation section outlet Mach number Ma4, isolation section outlet sound velocity c4, isolation section outlet flow velocity u4, isolation section outlet total temperature T) are calculated from the gas parameters after the normal shock wave. t4 , total pressure at the outlet of the isolation section P t4 , specific heat ratio at the isolation section outlet γ4, specific enthalpy at the isolation section outlet h4, static temperature at the isolation section outlet T4, static pressure at the isolation section outlet P4, density at the isolation section outlet ρ4).

[0047] Step 4: Based on the gas parameters at the isolation section outlet and the initial fuel state, calculate the gas parameters at the fuel injection and mixing section outlet.

[0048] The gas parameters at the mixing section outlet include gas flow parameters at the mixing section outlet, gas physical property parameters at the mixing section outlet, and gas state parameters at the mixing section outlet.

[0049] Step 4.1: Calculate the gas velocity u at the outlet of the mixing section based on the gas parameters at the outlet of the isolation section and the law of momentum conservation. 4mix .

[0050] The fuel is injected in a manner perpendicular to the air flow direction, and the actual flow captured by the equivalence ratio and the intake port is Calculating fuel flow The gas velocity at the outlet of the mixing section after fuel-air mixing is calculated based on the conservation of momentum as follows:

[0051]

[0052] In the above formula,

[0053] Step 4.2: Calculate the specific enthalpy of the gas at the mixing section outlet h based on the initial state of the fuel and the law of energy conservation 4mix , and the gas parameters at the outlet of the mixing section are calculated based on the second simplified assumption.

[0054] The second simplified assumption is that the gas flow rate at the outlet of the isolation section is relatively fast, the mixing process of the fuel and the incoming flow is completed in a very short time, and the gas pressure does not change much before and after mixing. Therefore, the mixing process is simplified to an isobaric process.

[0055] Based on the chemical reaction kinetics software Cantera, according to the fuel type, fuel injection pressure P f , fuel injection temperature T f Calculate the fuel specific enthalpy h f Finally, the specific enthalpy of the gas at the outlet of the mixing section after mixing is calculated by combining the gas parameters at the outlet of the isolation section with the energy conservation principle: 4mix , as follows:

[0056]

[0057] Based on the second simplified assumption, the gas properties at the outlet of the mixing section (the specific heat ratio γ at the outlet of the mixing section) were calculated by the chemical reaction kinetics software Canetra. 4mix ), gas state parameters at the outlet of the mixing section (static temperature T 4mix , static pressure at the outlet of mixing section P 4mix , density at the outlet of the mixing section ρ 4mix ), combined with the velocity term, the gas flow parameters at the mixing section outlet (Mach number Ma 4mix , the sound velocity c at the outlet of the mixing section 4mix , Total temperature at the outlet of mixing section T t4mix , total pressure at the outlet of mixing section P t4mix ). In addition, the outlet area of ​​the mixing section A 4mix It is the same size as the outlet area A4 of the isolation section.

[0058] Step 5: Based on the third simplified assumption, a rotating detonation combustion chamber model is constructed, and the combustion chamber outlet gas parameters under the conditions of stable rotating detonation and forward matching are calculated from the mixing section outlet gas parameters.

[0059] The combustion chamber outlet gas parameters include combustion chamber outlet gas flow parameters, combustion chamber outlet gas physical property parameters and combustion chamber outlet gas state parameters.

[0060] The third simplified assumption is that due to the influence of the rotating back pressure, the incoming flow forms a blockage at the inlet of the rotating detonation combustion chamber, and the blockage ratio B is introduced to define the flow channel blockage ratio at the inlet of the combustion chamber.

[0061] Step 5.1: Set the initial value of the congestion ratio B' and calculate the detonation wave front parameters from the gas parameters at the mixing section outlet.

[0062] The initial value of the congestion ratio B' is randomly given, and the flow of the gas at the outlet of the mixing section in the congested part is regarded as an isentropic flow with channel convergence (the area of ​​the congested section is (1-B)A 4mix ), and the detonation front gas parameters (detonation front Mach number Ma 5pre , detonation front speed of sound c 5pre , total temperature of detonation front Tt 5Pre , total pressure of detonation front P t5Pre , detonation front specific heat ratio γ 5pre , detonation wave front static temperature T 5pre , detonation front static pressure P 5pre , detonation front density ρ 5pre ).

[0063] Step 5.2: Calculate the detonation parameters from the detonation front gas parameters, and calculate the detonation wave front height H based on the combustion chamber geometric parameters.

[0064] Calculation of the detonation Chapman-Jouguet wave velocity D using gas phase detonation theory CJ and gas parameters after detonation wave (Mach number Ma CJ , speed of sound after detonation wave c CJ , total temperature after detonation wave T tCJ , total pressure after detonation wave P tCJ , specific heat ratio γ after detonation wave CJ , static temperature after detonation wave T CJ , static pressure after detonation wave P CJ , post-detonation density ρ CJ ), and the detonation wave front height H is calculated based on the mass conservation law as follows:

[0065]

[0066] Step 5.3: Establish a one-dimensional isentropic flow field after the detonation wave, calculate the circumferential distribution curve of the gas parameters after the rotating detonation wave based on the gas parameters after the detonation wave, and obtain the stable rotating detonation flow field through iterative solution in combination with the congestion ratio B.

[0067] The one-dimensional isentropic flow field behind the detonation wave is established with the detonation wave front as a reference system, the direction behind the detonation wave is positive, and the detonation products are discharged downstream in the form of isentropic expansion.

[0068] The circumferential distribution curves of gas parameters after the rotating detonation wave include: a circumferential distribution curve of pressure after the detonation wave P(x), a circumferential distribution curve of temperature after the detonation wave T(x), and a circumferential distribution curve of specific enthalpy after the detonation wave h(x).

[0069] According to the structural characteristics of the rotating detonation wave flow field, the contact gap angle β is defined and calculated as follows:

[0070]

[0071] The pressure attenuation factor α after refining the detonation wave is as follows:

[0072]

[0073] satisfy:

[0074]

[0075]

[0076] Among them, C represents the circumference of the combustion chamber, d1 is the outer diameter of the annular combustion chamber, d2 is the outer diameter of the annular combustion chamber, and x0 represents the influence domain of the high-pressure area after the detonation wave.

[0077] Combined with the empirical formula of Sichel et al. (M SICHEL, JC FOSTER. The ground impulse generated by a plane fuel-air explosion with side relief [J]. Acta Astronautica, 1979, 6 (3-4): 243-256.), the pressure circumferential distribution curve P (x) behind the detonation wave head is calculated as shown below:

[0078]

[0079] In the above formula, x represents the distance from the detonation wave front.

[0080] The temperature circumferential distribution curve T(x) after the detonation wave is calculated according to the isentropic relationship (see formula (13)), and the gas state is defined by the chemical reaction kinetics combined with the combustion product components after the detonation wave to solve the gas specific enthalpy circumferential distribution curve h(x) after the detonation wave (see formula (14)).

[0081]

[0082] h(x)=f(P(x),T(x)) (14)

[0083] The current congestion ratio B can be calculated based on the corrected post-detonation pressure distribution curve p(x). This is then iterated with the initial congestion ratio value B' in step 5.1 until the numerical error between the two meets the accuracy requirement. This confirms that the rotating detonation combustion chamber is in a stable operating state. The details are as follows:

[0084]

[0085] Step 5.4: Based on the self-similarity of the rotating detonation flow field, the circumferential distribution curve of the gas parameters after the detonation wave is calculated from the circumferential distribution curve of the gas parameters after the oblique shock wave, and finally the average pressure P in the rotating detonation combustion chamber is obtained. ave and combustion chamber outlet gas parameters.

[0086] The circumferential distribution curve of gas parameters after the oblique shock wave includes: the circumferential distribution curve of pressure after the oblique shock wave P s2 (x), circumferential temperature distribution curve T after the oblique shock wave s2 (x).

[0087] The combustion chamber outlet gas parameters include: combustion chamber outlet gas flow parameters, combustion chamber outlet gas physical property parameters, and combustion chamber outlet gas state parameters.

[0088] The expansion flow process of the combustion products after the detonation wave in the rotating detonation combustion chamber is regarded as an adiabatic isentropic process. The velocity distribution u(x) of the combustion products after the detonation wave is calculated by combining the circumferential distribution curve h(x) of the specific enthalpy after the detonation wave in step 5.3. The sound velocity c of the oblique shock wave is obtained by combining the circumferential distribution curve P(x) and the circumferential distribution curve T(x) of the temperature after the detonation wave with the chemical reaction kinetics. 5s1 =f(P(x=C),T(x=C)), and then combined with the velocity distribution u(x) of the combustion products after the detonation wave to obtain the relative Mach number Ma of the oblique shock wave front s1 .

[0089]

[0090] In the above formula, Δu(x) represents the velocity increment of the combustion products along the detonation wave.

[0091] The oblique shock wave angle θ is solved based on the contact discontinuity angle β calculated in step 5.3, as follows:

[0092]

[0093] The static pressure P behind the oblique shock wave can be obtained from the shock wave relationship s2 , static temperature after oblique shock wave T s2 and the specific heat ratio γ after the oblique shock wave s2Based on the structural characteristics of the rotating detonation flow field, the fresh combustion products on both sides of the contact discontinuity and the combustion products after the oblique shock wave have a self-similar solution with consistent static pressure and consistent airflow deflection angle. The circumferential distribution curve of the gas parameters after the detonation wave can be obtained by combining the isentropic relationship (the circumferential distribution curve of the pressure after the oblique shock wave P s2 (x), circumferential temperature distribution curve T after the oblique shock wave s2 (x)), satisfying the following formula:

[0094] P s2 (x 2+ )=P(x2),P s2 (x 2- )=P(C) (18)

[0095] In the above formula, x2 represents the equivalent position of the oblique shock wave head found by the self-similar solution, and x 2+ is the rear position of the oblique shock wave, x 2- is the position of the oblique shock wave front.

[0096] The circumference weighted average method is used to solve the circumferential distribution curve of the gas parameters after the oblique shock wave to obtain the combustion chamber outlet gas state parameters (combustion chamber outlet static pressure Combustion chamber outlet static temperature Combustion chamber outlet density ).

[0097]

[0098] Combining chemical reaction kinetics and combustion chamber outlet gas composition, the gas physical properties (specific heat ratio Then, based on the conservation of mass, the combustion chamber outlet gas flow parameters (combustion chamber outlet flow rate Combustion chamber exit Mach number Combustion chamber outlet sound speed Total temperature at combustion chamber outlet Total pressure at combustion chamber outlet ); the circumferential distribution curve of the pressure after the detonation wave P(x) is solved by the circumference weighted average method to obtain the average pressure after the detonation wave Finally, the average pressure P of the rotating detonation combustion chamber can be calculated by using the flow weighting method. ave , as shown below:

[0099]

[0100]

[0101] Step 5.5: Gas static pressure at the combustion chamber outlet and the static pressure P at the outlet of the mixing section 4mixThe cyclic iteration realizes the engine's forward matching and updates the combustion chamber outlet gas parameters.

[0102] At the current positive shock wave position initial value A' 32 The static pressure P at the outlet of the mixing section is calculated under the condition 4mix The average pressure P in the rotating detonation combustion chamber ave The values ​​should be consistent, otherwise return to step 3 through the sequential quadratic programming algorithm to re-iterate the calculation, and finally find the correct normal shock wave position A that can resist the influence of the rotating detonation back pressure and achieve forward matching. 32 At the same time, the combustion chamber outlet gas parameters (combustion chamber outlet Mach number Combustion chamber outlet sound speed Total temperature at combustion chamber outlet Total pressure at combustion chamber outlet Combustion chamber outlet specific heat ratio Combustion chamber outlet static pressure Combustion chamber outlet static temperature Combustion chamber outlet density ). In addition, the outlet area of ​​the rotating detonation combustion chamber is A6=A 4mix .

[0103] Step 6: Establish a tail nozzle adaptive working model and calculate the tail nozzle outlet gas parameters based on the combustion chamber outlet gas parameters.

[0104] The tail nozzle outlet gas parameters include: tail nozzle outlet static pressure P7, tail nozzle outlet static temperature T7, tail nozzle outlet flow rate u7.

[0105] Calculate the expansion acceleration process of the airflow in the tail nozzle, using the tail nozzle loss factor η ex (0<η ex <0.1) represents the flow loss during the airflow expansion and acceleration process. The specific process is as follows:

[0106]

[0107]

[0108]

[0109] In the above formula, Ma'7 is the Mach number at the tail nozzle outlet before the tail nozzle working state is not determined, T'7 is the Mach number at the tail nozzle outlet before the tail nozzle working state is not determined, and P'7 is the Mach number at the tail nozzle outlet before the tail nozzle working state is not determined.

[0110] According to the above calculation, the initial parameters of the tail nozzle outlet airflow are combined with the ambient back pressure P b (P b=P0) to determine the current working state of the tail nozzle (overexpansion, underexpansion, full expansion), and calculate and update the final gas flow parameters at the tail nozzle outlet using the following formula.

[0111]

[0112] When the tail nozzle is over-expanded (P'7 <P b ) Due to the excessive back pressure, there is a backflow near the outlet of the tail nozzle, which then interacts with the accelerated expansion of the exhaust airflow to form a complex wave system structure. It is simplified to be equivalent to a normal shock wave, and the initial value of the normal shock wave position in the tail nozzle is set to A' s , the normal shock wave relationship and the expansion acceleration flow relationship (see equations (22)-(24)) are iterated cyclically until the tail nozzle outlet pressure P7=P b Then, the tail nozzle outlet velocity u7 is solved according to the tail nozzle outlet gas state parameters (tail nozzle outlet static pressure P7, tail nozzle outlet static temperature T7) and the tail nozzle outlet Mach number Ma7. In addition, the tail nozzle outlet flow rate can be obtained from the conservation of mass

[0113] Step 7: Calculate the overall engine performance parameters based on the inlet inlet related parameters, tail nozzle outlet related parameters and fuel flow rate.

[0114] The inlet inlet related parameters include: inlet inlet flow rate u7, inlet inlet static pressure P7, inlet inlet area A7. The tail nozzle outlet related parameters include: tail nozzle outlet flow rate u7, tail nozzle outlet static pressure P7, tail nozzle outlet area A7.

[0115] The overall performance parameters of the rotating detonation ramjet engine are calculated by combining the tail nozzle outlet gas parameters in step 6 and the inlet inlet gas parameters in step 2 with the corresponding geometric parameters (see equations (26)-(27)). All the calculation results of the previous steps can be summarized to output the gas parameters of each internal flow section of the engine.

[0116]

[0117]

[0118] F is the engine thrust, Isp is the specific impulse, and g is the acceleration due to gravity.

[0119] In the above steps, the chemical reaction kinetics software Cantera is used in combination with relevant mechanism files to calculate the relevant chemical reaction processes, and physical properties such as the gas specific heat ratio γ in the gas freezing / equilibrium state can be calculated based on the gas state parameters (static pressure P, static temperature T, specific enthalpy h) of the flow section within the engine.

[0120] The isolation section in step 3 is an expansion type isolation section, the rotating detonation combustion chamber in step 5 is an annular combustion chamber, and the tail nozzle in step 6 is a convergent-divergent nozzle.

[0121] Example 1:

[0122] The reliability of the rotating detonation combustion chamber model, as the core component of the rotating detonation ramjet engine, will directly affect the accuracy of the calculation results of the overall engine performance model. Taking the ethylene-air detonation result data of Shepherd et al. as an example (JESHEPHERD, J.KASAHARA.Analytical Models for the Thrust of a RotatingDetonation Engine[J].2017.), the corresponding parameters were input into the rotating detonation combustion chamber subcomponent for calculation and comparison. The results are shown in the attached figure. Figure 4 shown.

[0123] In order to intuitively characterize the difference between the model calculation method and the experimental results, the average difference AD ​​is introduced, which is defined as:

[0124]

[0125] where X i 、X i0 The experimental and model calculation results for this example are shown in the table below, with N representing the number of comparison points. While some individual comparison points exhibit significant deviations, the overall average difference is approximately 5.73%. This indicates that the model calculation results for this subcomponent closely match the experimental results, demonstrating the model's reliability.

[0126]

[0127] The above describes the specific implementation methods of the present invention in detail with reference to the accompanying drawings and specific implementation processes, but the present invention is not limited to the above implementation methods. Those skilled in the art can make various changes and optimizations to the above methods without departing from the principles of the present invention.

Claims

1. A method for rapidly evaluating the overall performance of a rotating detonation ramjet engine, characterized in that: Here are the steps: Step 1: Input initial parameters according to design requirements; Step 2: Calculate the incoming gas parameters and the inlet outlet gas parameters based on the initial parameters; Step 3: Based on the gas parameters at the inlet duct outlet and the first simplified assumption, calculate the gas parameters at the isolation section outlet as follows: Step 3.1: Based on the gas parameters at the inlet outlet and the initial value of the normal shock wave position A' 32 , calculate the gas parameters of the normal shock front in the isolation section; Randomly set the initial value A' of the position of the normal shock wave 32 , A2 < A' 32 <A4, = a · A2, where A2 is the outlet area of the inlet, A4 is the outlet area of the isolator, and a is the area expansion ratio of the isolator; Combine the inlet outlet gas parameters obtained in step 2 as input parameters of the isolation section to calculate the gas parameters of the supersonic incoming flow accelerated expansion to the normal shock front, including: normal shock front gas flow parameters, normal shock front gas physical parameters, and normal shock front gas state parameters; The gas flow parameters before the normal shock wave include the Mach number Ma 32 , normal shock front speed c 32 , total temperature before normal shock wave T t32 , total pressure before the normal shock wave P t32 ; Normal shock front gas physical parameters, namely the normal shock front specific heat ratio γ 32 ; The gas state parameters before the normal shock wave include the static temperature T 32 , static pressure P before the normal shock wave 32 , normal shock front density ρ 32 ; Step 3.2: Based on the gas parameters before the normal shock wave in the isolation section, combined with the normal shock wave relationship and the isentropic expansion flow calculation formula, the gas parameters at the isolation section outlet are finally calculated: According to the normal shock wave relationship, the gas parameters after the normal shock wave are calculated; The gas parameters after the normal shock wave include the Mach number after the normal shock wave 34 , the speed of sound after the normal shock wave c 34 , total temperature after normal shock wave T t34 , total pressure after the positive shock wave P t34 , specific heat ratio γ after normal shock wave 34 , static temperature after normal shock wave T 34 , static pressure after normal shock wave P 34 , density after normal shock wave ρ 34 ; Then, according to the isentropic flow relationship, the gas parameters at the outlet of the isolation section are calculated from the gas parameters after the normal shock wave; The gas parameters at the isolation section outlet include the isolation section outlet Mach number Ma4, isolation section outlet sound velocity c4, isolation section outlet flow velocity u4, isolation section outlet total temperature T t4 , total pressure at the outlet of the isolation section P t4 , specific heat ratio γ4 at the isolation section outlet, specific enthalpy h4 at the isolation section outlet, static temperature T4 at the isolation section outlet, static pressure P4 at the isolation section outlet, density ρ4 at the isolation section outlet; Step 4: Calculate the gas parameters at the fuel injection and mixing section outlet based on the gas parameters at the isolation section outlet and the initial fuel state; Step 5: Based on the third simplified assumption, a rotating detonation combustion chamber model is constructed, and the combustion chamber outlet gas parameters are calculated from the mixing section outlet gas parameters under the conditions of stable rotating detonation and forward matching; Step 6: Establish a tail nozzle adaptive working model and calculate the tail nozzle outlet gas parameters based on the combustion chamber outlet gas parameters; Step 7: Calculate the overall engine performance parameters based on the inlet inlet related parameters, tail nozzle outlet related parameters and fuel flow rate.

2. The method for rapid evaluation of the overall performance of a rotating detonation ramjet engine according to claim 1, characterized in that: In step 1, the initial parameters include: flight conditions, key engine geometric parameters, inlet characteristic parameters, equivalence ratio φ, and initial fuel state; Flight conditions include flight altitude H and flight Mach number Ma0; The key geometric parameters of the engine include the inlet capture area A1, the expansion ratio of the isolation section a, the annular combustion chamber inner diameter d1, the annular combustion chamber outer diameter d2, the annular combustion chamber length l, and the tail nozzle outlet area A7; The intake duct characteristic parameters include intake duct boost ratio π, intake duct total pressure recovery coefficient σ, intake duct temperature rise ratio Ψ, intake duct flow coefficient Mach number at the inlet exit ex ; The initial fuel state includes the fuel injection pressure P f , fuel injection temperature T f .

3. The method for rapid evaluation of overall performance of a rotating detonation ramjet engine according to claim 1, characterized in that: In step 2, the incoming gas parameters include incoming gas flow parameters, incoming gas physical property parameters and incoming gas state parameters; the inlet duct outlet gas parameters include inlet duct outlet gas flow parameters, inlet duct outlet gas physical property parameters and inlet duct outlet gas state parameters; According to the flight altitude H and the flight Mach number Ma0, the flow parameters, physical properties and state parameters of the incoming gas are calculated; The intake duct capture flow rate can be calculated based on the intake duct capture area A1 Combined with the intake duct characteristic parameters, the intake duct outlet gas flow parameters, intake duct outlet gas physical parameters, intake duct outlet gas state parameters and the actual intake duct capture flow are calculated. Based on the conservation of mass, the inlet outlet flow area A2 is further calculated; in, The incoming gas flow parameters include the total temperature T t0 , total incoming flow pressure P t0 ; The physical property parameters of the incoming gas are the incoming specific heat ratio γ0; The incoming gas state parameters include the incoming static temperature T0, the incoming static pressure P0, and the incoming density ρ0; The gas flow parameters at the inlet outlet include the inlet outlet Mach number Ma2, the inlet outlet sound velocity c2, the inlet outlet total temperature T t2 , total pressure at the inlet duct outlet P t2 , Ma2=Ma ex ; The physical property parameter of the gas at the inlet duct outlet is the inlet duct outlet specific heat ratio γ2; The gas state parameters at the inlet duct outlet include the inlet duct outlet static temperature T2, the inlet duct outlet static pressure P2, and the inlet duct outlet density ρ2.

4. The method for rapid evaluation of the overall performance of a rotating detonation ramjet engine according to claim 2, characterized in that: In step 3, the gas parameters at the isolation section outlet include the gas flow parameters at the isolation section outlet, the gas physical property parameters at the isolation section outlet, and the gas state parameters at the isolation section outlet; The first simplified assumption is as follows: the losses caused by a normal shock wave and the entropy loss between adjacent aerodynamic sections are comprehensively equivalent, and the flow in the isolation section is divided into two parts: before the normal shock wave and after the normal shock wave.

5. The method for rapid evaluation of overall performance of a rotating detonation ramjet engine according to claim 4, characterized in that: In step 4, the gas parameters at the fuel injection and mixing section outlet are calculated based on the gas parameters at the isolation section outlet and the initial fuel state. The gas parameters at the mixing section outlet include the gas flow parameters at the mixing section outlet, the gas physical property parameters at the mixing section outlet, and the gas state parameters at the mixing section outlet, as follows: Step 4.1: Calculate the gas velocity u at the outlet of the mixing section based on the gas parameters at the outlet of the isolation section and the law of momentum conservation. 4mix ; Step 4.2: Calculate the specific enthalpy of the gas at the mixing section outlet h based on the initial state of the fuel and the law of energy conservation 4mix , and based on the second simplified assumption, the gas parameters at the mixing section outlet are calculated as follows: The second simplified assumption is that the gas velocity at the outlet of the isolation section is relatively high, the mixing process of the fuel and the incoming gas is completed in a very short time, and the gas pressure change before and after mixing is not large. Therefore, the mixing process is simplified to be an isobaric process. Based on the second simplified assumption, the physical properties and state parameters of the gas at the mixing section outlet were calculated using the chemical reaction kinetics software Canetra in combination with the gas composition at the mixing section outlet. The flow parameters of the gas at the mixing section outlet were further calculated in combination with the velocity term. Physical properties of the gas at the outlet of the mixing section, namely the specific heat ratio γ at the outlet of the mixing section 4mix ; The gas state parameters at the mixing section outlet include the static temperature T at the mixing section outlet 4mix , static pressure at the outlet of mixing section P 4mix , density at the outlet of the mixing section ρ 4mix ; The gas flow parameters at the mixing section outlet include the Mach number Ma at the mixing section outlet 4mix , the sound velocity c at the outlet of the mixing section 4mix , Total temperature at the outlet of mixing section T t4mix , total pressure at the outlet of mixing section P t4mix ; Among them, the outlet area of ​​the mixing section is A 4mix It is the same size as the outlet area A4 of the isolation section.

6. The method for rapid evaluation of overall performance of a rotating detonation ramjet engine according to claim 5, characterized in that: In step 5, the combustion chamber outlet gas parameters include combustion chamber outlet gas flow parameters, combustion chamber outlet gas physical property parameters and combustion chamber outlet gas state parameters; The third simplified assumption is that due to the influence of rotating back pressure, the incoming flow forms congestion at the inlet of the rotating detonation combustion chamber, and the congestion ratio B is introduced to define the congestion ratio of the flow channel at the inlet of the combustion chamber.

7. The method for rapid evaluation of overall performance of a rotating detonation ramjet engine according to claim 6, characterized in that: In step 5, a rotating detonation combustion chamber model is constructed based on the third simplified assumption. The combustion chamber outlet gas parameters under the conditions of stable rotating detonation and forward matching are calculated from the mixing section outlet gas parameters, as follows: Step 5.1: Set the initial value of the congestion ratio B' and calculate the detonation wave front parameters from the gas parameters at the mixing section outlet; The initial value of the congestion ratio B' is randomly given, and the flow of the gas at the outlet of the mixing section in the congested part is regarded as an isentropic flow with channel convergence. The flow area of ​​the congested section is (1-B)A 4mix , and calculate the gas parameters of the detonation front; Detonation front gas parameters include the detonation front Mach number Ma 5pre , detonation front speed of sound c 5pre , total temperature before detonation wave T t5pre , total pressure of detonation front P t5pre , detonation front specific heat ratio γ 5pre , detonation wave front static temperature T 5pre , detonation front static pressure P 5pre , detonation front density ρ 5pre ; Step 5.2: Calculate the detonation parameters from the detonation front gas parameters, and calculate the detonation wave front height H based on the combustion chamber geometric parameters; The detonation parameters include the static pressure P of the detonation wave front. Cj , static temperature of detonation wave front T CJ , detonation wave front speed of sound c CJ , detonation front specific heat ratio γ CJ ; Step 5.3: Establish a one-dimensional isentropic flow field after the detonation wave, calculate the circumferential distribution curve of the gas parameters after the rotating detonation wave based on the gas parameters after the detonation wave, and obtain the stable rotating detonation flow field through iterative solution in combination with the congestion ratio B; The isentropic flow field behind the one-dimensional detonation wave is established with the detonation wave front as the reference system, with the detonation wave front as the positive direction, and the detonation products are discharged downstream in the form of isentropic expansion; The circumferential distribution curves of gas parameters after the rotating detonation wave include: the circumferential distribution curve of pressure after the detonation wave P(x), the circumferential distribution curve of temperature after the detonation wave T(x), and the circumferential distribution curve of specific enthalpy after the detonation wave h(x); According to the structural characteristics of the rotating detonation wave flow field, the contact gap angle β is defined and calculated as follows: The pressure attenuation factor α after refining the detonation wave is as follows: satisfy: Where C represents the circumference of the combustion chamber, d1 is the inner diameter of the annular combustion chamber, d2 is the outer diameter of the annular combustion chamber, and x0 represents the influence domain of the high-pressure area after the detonation wave; The pressure circumferential distribution curve P(x) behind the detonation wave front is calculated as shown in the following formula: In the above formula, x represents the distance from the detonation wave front; Calculate the temperature circumferential distribution curve T(x) after the detonation wave, and then define the gas state by combining the chemical reaction kinetics with the combustion product components after the detonation wave to solve the circumferential distribution curve h(x) of the gas specific enthalpy after the detonation wave: h(x)=f(P(x),T(x)) (14) The current congestion ratio B is calculated based on the corrected post-detonation pressure distribution curve P(x). This is then iterated with the initial congestion ratio value B' in step 5.1 until the numerical error between the two meets the accuracy requirement. This allows the rotating detonation combustion chamber to be determined to be in a stable operating state, as follows: Step 5.4: Based on the self-similarity of the rotating detonation flow field, the circumferential distribution curve of the gas parameters after the detonation wave is calculated from the circumferential distribution curve of the gas parameters after the oblique shock wave, and finally the average pressure P in the rotating detonation combustion chamber is obtained. ave and combustion chamber outlet gas parameters; Step 5.5: Gas static pressure at the combustion chamber outlet and the static pressure P at the outlet of the mixing section 4mix The cyclic iteration realizes the engine's forward matching and updates the combustion chamber outlet gas parameters; At the current positive shock wave position initial value A' 32 The static pressure P at the outlet of the mixing section is calculated under the condition 4mix The average pressure P in the rotating detonation combustion chamber ave The values ​​should be consistent, otherwise return to step 3 through the sequential quadratic programming algorithm to re-iterate the calculation, and finally find the correct normal shock wave position A that can resist the influence of the rotating detonation back pressure and achieve forward matching. 32 ; At the same time, the combustion chamber outlet gas parameters are updated; Combustion chamber outlet gas parameters include combustion chamber outlet Mach number Combustion chamber outlet sound speed Total temperature at combustion chamber outlet Total pressure at combustion chamber outlet Combustion chamber outlet specific heat ratio Combustion chamber outlet static pressure Combustion chamber outlet static temperature Combustion chamber outlet density The outlet area of ​​the rotating detonation combustion chamber is A6 = A 4mix .

8. The method for rapid evaluation of overall performance of a rotating detonation ramjet engine according to claim 7, characterized in that: In step 5.4, the circumferential distribution curve of gas parameters after the oblique shock wave includes the circumferential distribution curve of pressure after the oblique shock wave P s2 (x), circumferential temperature distribution curve after oblique shock wave T s2 (x); The combustion chamber outlet gas parameters include combustion chamber outlet gas flow parameters, combustion chamber outlet gas physical parameters, and combustion chamber outlet gas state parameters; The expansion flow process of the combustion products after the detonation wave in the rotating detonation combustion chamber is regarded as an adiabatic isentropic process. The velocity distribution u(x) of the combustion products after the detonation wave is calculated based on the circumferential distribution curve h(x) of the specific enthalpy after the detonation wave in step 5.

3. The sound velocity c of the oblique shock wave front is obtained based on the circumferential distribution curve P(x) and the circumferential distribution curve T(x) of the temperature after the detonation wave in combination with the chemical reaction kinetics. 5s1 =f(P(x=C),T(x=C)), and then combined with the velocity distribution u(x) of the combustion products after the detonation wave to obtain the relative Mach number Ma of the oblique shock wave front s1 : In the above formula, Δu(x) represents the velocity increment of the combustion products along the detonation wave; The oblique shock wave angle θ is solved based on the contact discontinuity angle β calculated in step 5.3, as follows: The static pressure P behind the oblique shock wave can be obtained from the shock wave relationship s2 , static temperature after oblique shock wave T s2 and the specific heat ratio γ after the oblique shock wave s2 Based on the structural characteristics of the rotating detonation flow field, the fresh combustion products on both sides of the contact discontinuity and the combustion products after the oblique shock wave have a self-similar solution with consistent static pressure and consistent airflow deflection angle. The circumferential distribution curve of the gas parameters after the detonation wave can be obtained by combining the isentropic relationship, which satisfies the following formula: P s2 (x) 2+ )=P(x2),P s2 (x) 2- )=P(C) (18) In the above formula, x2 represents the equivalent position of the oblique shock wave head found by the self-similar solution, and x 2+ is the rear position of the oblique shock wave, x 2- is the position of the oblique shock wave front, P s2 (x) represents the circumferential distribution curve of pressure after the oblique shock wave, T s2 (x) represents the circumferential temperature distribution curve after the oblique shock wave; The circumference weighted average method is used to solve the circumferential distribution curve of the gas parameters after the oblique shock wave to obtain the gas state parameters at the combustion chamber outlet, including the static pressure at the combustion chamber outlet. Combustion chamber outlet static temperature Combustion chamber outlet density Combining the chemical reaction kinetics and the gas composition at the combustion chamber outlet, the gas physical properties, namely the specific heat ratio, are obtained. Solve the combustion chamber outlet gas flow parameters based on mass conservation, including the combustion chamber outlet flow rate Combustion chamber exit Mach number Combustion chamber outlet sound speed Total temperature at combustion chamber outlet Total pressure at combustion chamber outlet The circumferential distribution curve P(x) of the pressure after the detonation wave is solved by the circumference weighted average method to obtain the average pressure after the detonation wave. Finally, the average pressure P of the rotating detonation combustion chamber can be calculated by using the flow weighting method. ave , as shown below:

9. The method for rapidly evaluating the overall performance of a rotating detonation ramjet engine according to claim 8, characterized in that: In step 6, the tail nozzle outlet gas parameters include: tail nozzle outlet static pressure P7, tail nozzle outlet static temperature T7, tail nozzle outlet flow rate u7; Calculate the expansion acceleration process of the airflow in the tail nozzle, using the tail nozzle loss factor η ex Characterize the flow loss during the airflow expansion and acceleration process. The specific process is as follows: In the above formula, Ma'7 is the Mach number at the tail nozzle outlet before the tail nozzle working state is not determined, T'7 is the Mach number at the tail nozzle outlet before the tail nozzle working state is not determined, and P'7 is the Mach number at the tail nozzle outlet before the tail nozzle working state is not determined; According to the above calculation, the initial parameters of the tail nozzle outlet airflow are combined with the ambient back pressure P b , P b = P0, judge the current working state of the tail nozzle, including over-expansion, under-expansion, and full expansion, and calculate and update the final gas flow parameters at the tail nozzle outlet using the following formula: The tail nozzle is over-expanded, that is, P'7 <P b When the back pressure is too high, there is a backflow near the outlet of the tail nozzle, which then interacts with the accelerated expansion and discharged airflow to form a complex wave system structure. Simplify it into a normal shock wave equivalent, and set the initial value of the normal shock wave position in the tail nozzle A' s , the normal shock wave relationship and the expansion acceleration flow relationship, that is, equation (22)-equation (24), are iterated cyclically until the tail nozzle outlet pressure P7=P b ; Then, the tail nozzle outlet flow velocity u7 is solved according to the tail nozzle outlet gas state parameters and the tail nozzle outlet Mach number Ma7. The tail nozzle outlet gas state parameters include the tail nozzle outlet static pressure P7 and the tail nozzle outlet static temperature T7; According to the conservation of mass, the tail nozzle outlet flow rate can be obtained 10. The method for rapid evaluation of overall performance of a rotating detonation ramjet engine according to claim 9, characterized in that: In step 7, the overall engine performance parameters are calculated based on the inlet inlet related parameters, tail nozzle outlet related parameters and fuel flow rate, as follows: The inlet inlet related parameters include the inlet inlet flow rate u7, the inlet inlet static pressure P7, and the inlet inlet area A7; the tail nozzle outlet related parameters include the tail nozzle outlet flow rate u7, the tail nozzle outlet static pressure P7, and the tail nozzle outlet area A7; The overall performance parameters of the rotating detonation ramjet engine are calculated by combining the tail nozzle outlet gas parameters in step 6 and the inlet inlet gas parameters in step 2 with the corresponding geometric parameters, as shown in equations (26)-(27). All the calculation results of the previous steps are summarized to output the gas parameters of each internal flow section of the engine. F is the engine thrust, Isp is the specific impulse, and g is the acceleration due to gravity.

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