Rapid estimation method for specific thrust and specific impulse performance of air suction type ramjet

Abstract

The invention belongs to the field of aerospace air-breathing type ramjet engine design, and particularly relates to a rapid estimation method for specific thrust and specific impulse performance of an air-breathing type ramjet engine. The total temperature ratio of a combustion system is calculated according to the incoming flow condition, the combustion frequency of a combustion chamber, the fuel heat value and the oil-gas ratio, and finally estimated values of the specific thrust and specific impulse of the air-breathing engine are calculated according to the total kinetic energy efficiency of the engine and the total temperature ratio of the combustion system. Based on the total kinetic energy efficiency, the specific thrust and specific impulse performance of the air-breathing ramjet engine can be conveniently predicted. The method has the advantages of simple operation, accurate calculation, wide application range and the like. Through the method, research and development personnel can quickly and accurately estimate the specific thrust and specific impulse performance of the air suction type ramjet engine, and therefore engine design and optimization can be better guided. In addition, the method can also reduce the cost and time of the experimental test, and improve the research and development efficiency.

Description

Technical Field

[0001] The present application belongs to the field of aerospace air-breathing ramjet engine design, and in particular to a method for quickly estimating the specific thrust and specific impulse performance of an air-breathing ramjet engine. Background Art

[0002] Air-breathing ramjet is an advanced aircraft engine with the advantages of high speed, high efficiency and simple structure, and is widely used in the aerospace field. In the design and optimization process of air-breathing ramjet, specific thrust and specific impulse performance are very important performance indicators. However, the performance of existing air-breathing ramjet engines is affected by many factors, such as inlet design, combustion chamber design, nozzle design, etc., which often involve complex numerical simulation and experimental testing, which not only increases the R&D cost, but also affects the R&D efficiency. Therefore, it is very necessary to develop a method for estimating the specific thrust and specific impulse performance of air-breathing ramjet engines. Summary of the invention

[0003] The purpose of this application is to provide a method for quickly estimating the specific thrust and specific impulse performance of an air-breathing ramjet engine, so as to solve the problems of high cost and low research and development efficiency of existing methods for estimating the specific thrust and specific impulse performance of air-breathing ramjet engines.

[0004] The technical solution of the present application is: a method for quickly estimating the specific thrust and specific impulse performance of an air-breathing ramjet engine, comprising:

[0005] The engine is divided into three parts: compression system, combustion system and expansion system. The corresponding efficiencies of the three systems are compression kinetic energy efficiency, combustion kinetic energy efficiency and expansion kinetic energy efficiency respectively. The compression kinetic energy efficiency, combustion kinetic energy efficiency and expansion kinetic energy efficiency of the engine are calculated according to the simulation or test characteristics of the air-breathing ramjet engine, and the total kinetic energy efficiency η of the engine is calculated according to the total kinetic energy efficiency formula. KEO ;

[0006] Determine the engine fuel type and give the fuel calorific value h of the fuel PR and oil-gas ratio f;

[0007] Given the compression system of the engine, the Mach number M0 is obtained;

[0008] According to the flow condition η b 、Combustion chamber combustion frequency C p , fuel calorific value h PR and the oil-gas ratio f to determine the preset items The calculated value of the combustion system is then calculated based on the preset items. b , where T to The total temperature of the compressed components;

[0009] Finally, according to the total kinetic energy efficiency η of the engineKEO and the total temperature ratio of the combustion system τ b Calculate estimates of specific thrust and specific impulse for an air-breathing engine.

[0010] Preferably, the total kinetic energy efficiency η KEO The calculation method is:

[0011] The compression system kinetic efficiency η KE，c for:

[0012]

[0013] The combustion system kinetic efficiency η KE，b for:

[0014]

[0015] The combustion system kinetic efficiency η KE，e for:

[0016]

[0017] The total kinetic energy efficiency of the air-breathing ramjet engine is KEO It is expressed as:

[0018] η KEO =η KE，c ·η KE，b ·η KE，e

[0019] Where V x is the outlet velocity of the compression component, V0 is the free flow velocity, V y is the exit velocity of the combustion component, V 10 is the outlet velocity of the expansion component, T t3 is the total temperature at the inlet of the combustion component, T t4 is the total temperature at the outlet of the combustion component.

[0020] Preferably, the total temperature ratio τ of the combustion system b The calculation formula is:

[0021]

[0022] Preferably, the calculation formula of the specific thrust of the air-breathing engine is:

[0023] According to the expansion principle of air-breathing ramjet, calculate the outlet velocity V of the expansion component 10 ;

[0024] According to the outlet velocity V of the expansion component 10 Determine the engine thrust F;

[0025] Combined with the engine's total kinetic energy efficiency ηKEO and the total temperature ratio of the combustion system τ b ;

[0026] Combined with the engine's total kinetic energy efficiency η KEO and the total temperature ratio of the combustion system τ b Calculate specific thrust of air-breathing engines;

[0027] Combined with the total temperature ratio of the combustion system τ b The calculation formula is used to obtain the expression of the specific thrust of the air-breathing engine based on the total kinetic energy efficiency.

[0028] Preferably, the specific thrust of the air-breathing engine is expressed based on the total kinetic energy efficiency as follows:

[0029]

[0030] Where, T to The total temperature of the compressed components; is the air flow of the compression component.

[0031] Preferably, the calculation formula of the specific impulse of the air-breathing engine is:

[0032]

[0033] Then the specific impulse of the air-breathing ramjet engine based on the total kinetic energy efficiency is expressed as:

[0034]

[0035] The method for quickly estimating the specific thrust and specific impulse performance of an air-breathing ramjet engine of the present application can conveniently predict the specific thrust and specific impulse performance of an air-breathing ramjet engine based on the total kinetic energy efficiency. It has the advantages of simple operation, accurate calculation, and wide application range. Through this method, researchers can quickly and accurately estimate the specific thrust and specific impulse performance of an air-breathing ramjet engine, thereby better guiding engine design and optimization. In addition, this method can also reduce the cost and time of experimental testing and improve research and development efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solution provided by the present application, the following is a brief introduction to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present application.

[0037] Figure 1 This is the overall flow chart of this application;

[0038] Figure 2 It is a cross-sectional schematic diagram of the air-breathing ramjet engine of the present application, wherein ① is a subsonic ramjet engine, and ② is a scramjet engine;

[0039] Figure 3 The specific thrust estimation curve of the air-breathing ramjet engine for this application;

[0040] Figure 4 This is a graph of specific impulse estimation for an air-breathing ramjet engine for this application. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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.

[0042] The invention discloses a rapid estimation method for specific thrust and specific impulse performance of an air-breathing ramjet engine, which can realize accurate prediction of specific thrust and specific impulse by comprehensively considering the aerodynamic performance and thermodynamic performance of the air-breathing ramjet engine.

[0043] The steps include:

[0044] Step S100, for example Figure 2 For the air-breathing ramjet engine shown in the figure, the ramjet engine includes two modes: subsonic ramjet engine and scramjet engine. The engine can be divided into three parts: compression system, combustion system and expansion system. The corresponding efficiencies of the three systems are compression kinetic energy efficiency, combustion kinetic energy efficiency and expansion kinetic energy efficiency respectively.

[0045] Calculate the compression kinetic energy efficiency, combustion kinetic energy efficiency and expansion kinetic energy efficiency of the engine according to the simulation or test characteristics of the air-breathing ramjet engine, and calculate the total kinetic energy efficiency of the engine according to the total kinetic energy efficiency formula;

[0046] The total kinetic energy efficiency is calculated as:

[0047] The kinetic efficiency of a compression system is defined as the ratio of the square of the compression component outlet velocity to the square of the free flow velocity and is represented by the symbol η KE，c The kinetic energy efficiency of the compression system is expressed as KE，c for:

[0048]

[0049] The kinetic efficiency of the combustion system is defined as the ratio of the square of the combustion component outlet velocity to the square of the combustion component inlet velocity divided by the total temperature ratio, where the combustion component inlet velocity is the same as the compression component outlet velocity and is represented by the symbol η KE，b The kinetic energy efficiency of the combustion system is expressed as KE，b for:

[0050]

[0051] The kinetic efficiency of the expansion system is defined as the ratio of the square of the outlet velocity of the expansion component to the square of the inlet velocity of the expansion component and is represented by the symbol η KE，e The kinetic energy efficiency of the combustion system is expressed as KE，e for:

[0052]

[0053] The total kinetic energy efficiency of the air-breathing ramjet engine is KEO It is expressed as:

[0054] η KEO =η KE，c ·η KE，b ·η KE，e .

[0055] Where V x is the outlet velocity of the compression component, V0 is the free flow velocity, V y is the exit velocity of the combustion component, V 10 is the outlet velocity of the expansion component, T t3 is the total temperature at the inlet of the combustion component, T t4 is the total temperature at the outlet of the combustion component.

[0056] Step S200, determine the engine fuel type and give the fuel calorific value h PR And oil and gas ratio f. Such as using hydrocarbon fuel or liquid hydrogen.

[0057] Step S300, providing the compression system flow Mach number M0 of the engine.

[0058] Step S400, according to the incoming flow condition η b 、Combustion chamber combustion frequency C p , fuel calorific value h PR and oil-gas ratio f to determine the preset items The calculated value of the combustion system is then calculated based on the preset items. b Where, T to is the total temperature at the inlet of the compression component;

[0059] The expression obtained by analyzing the first law of adiabatic combustion process is used to replace the total temperature ratio τ of the combustion system. b , the performance of the air-breathing engine can be studied more deeply, and the total temperature of the combustion system is τ b The calculation formula is:

[0060]

[0061] Step S500, finally, according to the total kinetic energy efficiency of the engine and the total temperature ratio τ of the combustion system b Calculate estimates of specific thrust and specific impulse for an air-breathing engine.

[0062] Preferably, if Figure 3 , liquid hydrogen is selected as the fuel, the oil-gas ratio f is 0.0291, r is 1.28, and the speed of sound is 299m / s; the calculation method for the estimated value of the specific thrust of the air-breathing engine is:

[0063] According to the expansion principle of air-breathing ramjet, calculate the outlet velocity V of the expansion component 10 , the outlet velocity of the expansion part is V 10 It can be expressed as:

[0064]

[0065] According to the outlet velocity V of the expansion component 10 Determine the engine thrust F, the expression of engine thrust F is:

[0066]

[0067] Combined with the engine's total kinetic energy efficiency η KEO and the total temperature ratio of the combustion system τ b Calculate the specific thrust of an air-breathing engine using the following formula:

[0068]

[0069] Right now:

[0070]

[0071] In the formula, is the air flow rate of the compression system, is the fuel flow rate.

[0072] Combined with the total temperature ratio of the combustion system τ b The specific thrust of an air-breathing engine is Can be transformed into:

[0073]

[0074] Right now:

[0075]

[0076] Since V0 = aM0, where a is the local speed of sound, the specific thrust of the air-breathing engine is based on the expression of the total kinetic energy efficiency, which is:

[0077]

[0078] Preferably, if Figure 4, liquid hydrogen is selected as the fuel, the oil-gas ratio f is 0.0291, r is 1.28, the speed of sound is 299m / s, and the calculation formula for the specific impulse of the air-breathing engine is:

[0079]

[0080] Then the specific impulse of the air-breathing ramjet engine based on the total kinetic energy efficiency is expressed as:

[0081]

[0082] Through the above design, based on the total kinetic energy efficiency, the specific thrust and specific impulse performance of the air-breathing ramjet engine can be easily predicted. It has the advantages of simple operation, accurate calculation, and wide application range. Through this method, researchers can quickly and accurately estimate the specific thrust and specific impulse performance of the air-breathing ramjet engine, thereby better guiding engine design and optimization. In addition, this method can also reduce the cost and time of experimental testing and improve research and development efficiency.

[0083] Finally, it should be noted that: the drawings of the embodiments disclosed in the present invention only involve structures related to the embodiments disclosed in the present invention, and other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of the present invention can be combined with each other;

[0084] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for rapidly estimating the specific thrust and specific impulse performance of an air-breathing ramjet engine, characterized in that: include: The engine is divided into three parts: compression system, combustion system and expansion system. The corresponding efficiencies of the three systems are compression kinetic energy efficiency, combustion kinetic energy efficiency and expansion kinetic energy efficiency respectively. The compression kinetic energy efficiency, combustion kinetic energy efficiency and expansion kinetic energy efficiency of the engine are calculated according to the simulation or test characteristics of the air-breathing ramjet engine, and the total kinetic energy efficiency η of the engine is calculated according to the total kinetic energy efficiency formula. KEO ; Determine the engine fuel type and give the fuel calorific value h of the fuel PR and oil-gas ratio f; Given the compression system of the engine, the Mach number M0 is obtained; According to the flow condition η b 、Combustion chamber combustion frequency C p , fuel calorific value h PR and the oil-gas ratio f to determine the preset items The calculated value of the combustion system is then calculated based on the preset items. b , where T to Total temperature of the flow from the compression system; Finally, according to the total kinetic energy efficiency η of the engine KEO and the total temperature ratio of the combustion system τ b Calculate estimates of specific thrust and specific impulse for an air-breathing engine.

2. The method for rapidly estimating specific thrust and specific impulse performance of an air-breathing ramjet engine according to claim 1, characterized in that: The total kinetic energy efficiency η KEO The calculation method is: The compression system kinetic efficiency η KE，c for: The combustion system kinetic efficiency η KE,b for: The combustion system kinetic efficiency η KE，e for: The total kinetic energy efficiency of the air-breathing ramjet engine is KEO It is expressed as: or KEO =the KE，c ·or KE，b ·or KE，e Where V x is the outlet velocity of the compression component, V0 is the free flow velocity, V y is the exit velocity of the combustion component, V 10 is the outlet velocity of the expansion component, T t3 is the total temperature at the inlet of the combustion component, T t4 is the total temperature at the outlet of the combustion component.

3. The method for rapidly estimating specific thrust and specific impulse performance of an air-breathing ramjet engine according to claim 1, characterized in that: The total temperature ratio τ of the combustion system b The calculation formula is:

4. The method for rapidly estimating specific thrust and specific impulse performance of an air-breathing ramjet engine according to claim 1, characterized in that: The calculation formula of the specific thrust of the air-breathing engine is: According to the expansion principle of air-breathing ramjet, calculate the outlet velocity V of the expansion component 10 ; According to the outlet velocity V of the expansion component 10 Determine the engine thrust F; Combined with the engine's total kinetic energy efficiency η KEO and the total temperature ratio of the combustion system τ b ; Combined with the engine's total kinetic energy efficiency η KEO and the total temperature ratio of the combustion system τ b Calculate specific thrust of air-breathing engines; Combined with the total temperature ratio of the combustion system τ b The calculation formula is used to obtain the expression of the specific thrust of the air-breathing engine based on the total kinetic energy efficiency.

5. The method for rapidly estimating specific thrust and specific impulse performance of an air-breathing ramjet engine according to claim 4, characterized in that: The specific thrust of the air-breathing engine is expressed based on the total kinetic energy efficiency as follows: Where, T to Total temperature of the compressed components; is the air flow of the compression component.

6. The method for rapidly estimating specific thrust and specific impulse performance of an air-breathing ramjet engine according to claim 4, characterized in that: The calculation formula of the specific impulse of the air-breathing engine is: Then the specific impulse of the air-breathing ramjet engine based on the total kinetic energy efficiency is expressed as:

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