Analysis and calculation method of cooling performance index of attitude control engine high-altitude simulation test system

Abstract

The present application relates to a kind of attitude control engine high-altitude simulation test system cooling performance index analysis and calculation method, mainly solve the technical problems that existing analysis method is prone to cause the large deviation between test result and actual situation.The method first analyzes the basic relationship between cooling water evaporation and gas cooling in cooling process, then sets the gas cooling target value, then in turn calculates the mass fraction of each gas component, the average constant-pressure heat capacity of gas inlet and outlet, the total heat exchange of gas cooling process, the heat absorbed by cooling water in cooling process, the theoretical water injection of cooling water in cooling process, finally, the actual water injection of cooling water in cooling process is obtained by combining safety factor calculation, so as to complete the analysis and calculation of attitude control engine high-altitude simulation test system cooling performance index, ensure the inlet temperature requirement of injection system, and the stability and reliability of test system.

Description

TECHNICAL FIELD

[0001] The present application relates to a liquid rocket engine environment simulation test method, in particular to a cooling performance index analysis and calculation method of an attitude control engine high-altitude simulation test system. BACKGROUND

[0002] The attitude control engine is mainly used for controlling the attitude of the aircraft, and can also be used for speed correction, orbit adjustment, position maintenance, etc. of the aircraft. It is an indispensable power device for the orbit vehicle into orbit, reentry, final correction, etc. The performance of the attitude control engine is crucial to the hit accuracy of the aircraft.

[0003] At present, the performance of the attitude control engine is usually evaluated by using a high-altitude simulation test system (hereinafter referred to as "test system"). The gas temperature of the combustion chamber of the test system can be as high as 3400K or more, which is quite different from the temperature requirement of 300℃ or less at the inlet of the test system ejector device, thereby affecting the suction performance of the test system and the high-altitude simulation capability, and ultimately failing to meet the requirements of the ground ignition test of the attitude control engine. In addition, the temperature of the high-speed and high-temperature gas exceeds the heat resistance limit of the materials of the devices of the test system, thereby easily causing serious ablation and even damage to the test system.

[0004] To solve the above problems, the high-temperature gas generated by the test system is usually cooled by water injection and spraying. Therefore, the feasibility of the cooling scheme is particularly important. The prior art first calculates the heat exchange of the cooling water and the high-temperature gas, and then adjusts the injection amount of the cooling water in real time during the cooling process based on working experience. This method can achieve good cooling effect, but since the injection amount is adjusted by the operator based on experience, it lacks theoretical basis, resulting in deviation between the calculation result and the actual situation, so the injection amount of the cooling water needs to be adjusted constantly. At the same time, due to the constant adjustment of the injection amount of the cooling water, the instability of the test system increases, and the test system presents dynamic changes, thereby easily leading to a large deviation between the test result and the actual situation, and ultimately leading to the inconsistency between the performance evaluation of the engine and the actual situation. SUMMARY

[0005] The purpose of the present application is to solve the technical problem that the existing analysis method easily leads to a large deviation between the test result and the actual situation, and to provide a cooling performance index analysis and calculation method of an attitude control engine high-altitude simulation test system.

[0006] To achieve the above purpose, the technical solution provided by the present application is as follows:

[0007] A cooling performance index analysis and calculation method of an attitude control engine high-altitude simulation test system, characterized in that it comprises the following steps:

[0008] Step 1, based on the evaporation characteristics of the cooling water in the cooling device of the attitude control engine high-altitude simulation test system, and the molar mass and gas temperature of the fuel gas, the basic relationship between the evaporation of the cooling water and the cooling of the fuel gas in the cooling process is analyzed;

[0009] Step 2, on the basis of step 1, according to the properties of the combustion medium, the gas parameters are determined, and according to the environmental simulation requirements of the engine, the target value of the gas cooling is set; the gas parameters include the gas mass flow of the combustion medium, the gas composition and the molar mass of each gas component, the gas inlet temperature;

[0010] Step 3, according to the molar mass of each gas component, the mass fraction of each gas component is calculated, and then the average constant-pressure heat capacity of the gas inlet and the average constant-pressure heat capacity of the gas outlet are calculated;

[0011] Step 4, on the basis of step 3, combined with the gas mass flow of the combustion medium, the gas inlet temperature and the gas cooling target value set in step 2, the total heat exchange amount of the gas cooling process is further calculated;

[0012] Step 5, based on the mass flow of the cooling water injection and the initial temperature before the injection, the heat absorbed by the cooling water in the cooling process is calculated;

[0013] Step 6, the total heat exchange amount obtained in step 4 and the heat absorbed by the cooling water obtained in step 5 are calculated to obtain the theoretical water injection amount of the cooling water in the cooling process;

[0014] Step 7, according to the material properties of the cooling device, the safety factor is determined, and combined with the theoretical water injection amount, the actual water injection amount of the cooling water in the cooling process is calculated, so as to complete the analysis and calculation of the cooling performance index of the attitude control engine high-altitude simulation test system.

[0015] Further, in step 4, the total heat exchange amount Q z is calculated by the following formula:

[0016] Q z = Q r ×(C pgi T i -C poi T o )

[0017] In the formula, Q r is the gas mass flow of the combustion medium, C pgi is the average constant-pressure heat capacity of the gas inlet, i represents i kinds of gas components, i≥1, C poi is the average constant-pressure heat capacity of the gas outlet, T i is the gas inlet temperature, and T o is the target value of the gas cooling.

[0018] Further, in step 5, the cooling water absorbs heat in the cooling process The calculation is made by the following formula:

[0019]

[0020] In the formula, is the mass flow of the sprayed atomized water, is the specific heat capacity of the liquid water at constant pressure, is the saturation temperature of the water, is the initial temperature of the sprayed atomized water, is the latent heat of vaporization of the water, is the specific heat capacity of the water vapor at constant pressure.

[0021] Further, in step 6, the theoretical water spraying amount of the cooling water The calculation is made by the following formula:

[0022]

[0023] Further, in step 7, the safety factor is taken as 1.1-1.25.

[0024] Compared with the prior art, the present application has the following advantages:

[0025] 1. The present application calculates the core parameters in the heat exchange process between the gas and the cooling water by analyzing the relationship between the evaporation of the cooling water and the cooling of the gas in the cooling process, and combining the properties of the combustion medium, so as to obtain the actual water spraying amount of the cooling water in the cooling process. The method can accurately analyze the cooling process of the test system, so as to ensure that the test environment is consistent with the real environment of the engine, and finally accurately evaluate the real performance of the engine.

[0026] 2. The calculation process of the present application is based on the specific parameters of the gas, so as to accurately obtain the actual water spraying amount of the cooling water, and ensure the stability of the test system.

[0027] 3. The present application is applicable to the combustion and heat exchange process of the gas generated by different combustion media. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is the flowchart of the embodiment of the present application. DETAILED DESCRIPTION

[0029] In order to make the purpose, advantages and characteristics of the present application clearer, the present application is further described in detail below in combination with the drawings and specific embodiments. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present application, and the purpose is not to limit the protection scope of the present application.

[0030] As Figure 1 shown, the embodiment provides a cooling performance index analysis and calculation method of a high-altitude simulation test system of an attitude control engine, comprising the following steps:

[0031] Step 1, based on the evaporation characteristics of cooling water in the cooling device of the high-altitude simulation test system of the attitude control engine, the basic relationship between cooling water evaporation and gas cooling in the cooling process is analyzed.

[0032] Firstly, the heat balance of the vacuum-induced gas active cooling process is analyzed, and according to the evaporation characteristics of the cooling water in the cooling device of the high-altitude simulation test system of the attitude control engine, the heat transfer process of the cooling water droplet particle surface is analyzed in combination with the test system parameters and the working environment state, so as to obtain the heat balance equation of the gas water spray cooling, and then based on the heat balance equation, the subsequent calculation and analysis are carried out.

[0033] Firstly, the continuous phase flow field of the test system is calculated, and after the continuous phase flow field of the gas is stable, the calculation of the discrete phase flow, injection, evaporation and heat exchange of the cooling water droplet particles is carried out. Under the premise of considering the evaporation characteristics of the cooling water, the analysis process of the water spray cooling of the high-temperature gas is simplified, and for the heat balance in the vacuum-induced gas active cooling process, when the cooling water temperature is lower than the evaporation temperature T vap , the heating or cooling law of the droplet (liquid cooling water) can be applied, and in this case:

[0034] T p <T vap , m p ≤(1-f v,o )m p,o

[0035] In the formula: T p is the current temperature of the droplet, m p is the initial mass of the droplet, m p,o is the current mass of the droplet, f v,o is the evaporation rate.

[0036] When the cooling water temperature reaches the evaporation temperature and starts to evaporate, the diffusion of the droplet to the gas phase is mainly related to the concentration between the two, that is:

[0037] N i =k i (C i,s -C i,R )

[0038] In the formula: N i is the molar flow rate of the vapor; k i is the mass transfer coefficient; C i,sis the vapor concentration of the droplet surface; C i,R is the vapor concentration of the gas phase mainstream.

[0039] As the continuous evaporation of the cooling water, the mass of the droplet is also consumed, and the mass consumption of the droplet is:

[0040] m p (t+Δt)=m p (t)-N i A p M w,i Δt

[0041] In the formula, M w,i is the molar mass of different gas components; m p is the initial mass of the droplet; A p is the surface area of the droplet, t represents the gas temperature, and Δt represents the change in the gas temperature.

[0042] For the discrete phase evaporation (i.e. droplet particle evaporation), the heat balance equation of the gas water spray cooling process is:

[0043]

[0044] In the formula, c p is the specific heat at constant pressure of the droplet; T p is the droplet temperature (K); h is the convective heat transfer coefficient; T i is the continuous phase temperature; is the evaporation rate; h fg is the latent heat of vaporization; ε p is the particle blackness; σ is the Stefan-Boltzmann constant; θ R is the radiation temperature, T R is the absorption temperature.

[0045] According to the heat balance equation of the gas water spray cooling process obtained by the above analysis, the basic relationship between the evaporation and cooling of the cooling water in the water spray cooling process can be obtained, thereby providing a theoretical basis for the analysis and calculation of the cooling and cooling index under the premise of considering the evaporation rate of the cooling water.

[0046] Step 2, on the basis of step 1, according to the properties of the combustion medium, the gas parameters are determined, and according to the environmental simulation requirements of the engine, the cooling target value of the gas is set, which is the outlet temperature of the gas.

[0047] The gas parameters described in this embodiment include the basic parameters of the gas mass flow of the combustion medium, the gas composition, the molar mass of each gas component, and the inlet temperature of the gas.

[0048] Step 3, according to the molar mass of each gas component, the mass fraction of each gas component is calculated, and then the average constant pressure heat capacity of the gas inlet and the average constant pressure heat capacity of the gas outlet are calculated.

[0049] First, let the gas mass flow of the gas medium be Q r Taking the combustion medium commonly used in attitude control engine, hydrazine, as an example, its gas components are mainly CO, H2O, H2, N2, CO2, and the molar mass of each gas component is Y CO 、 Thus, the average molecular weight u of the gas is calculated, that is:

[0050]

[0051] In the formula, u CO 、 is the molecular weight of each gas component.

[0052] Next, the mass fraction of each gas component is calculated, that is:

[0053]

[0054] At this time, assuming that t1 is the gas inlet temperature, the linear relationship of the constant pressure heat capacity of each gas component is as follows:

[0055] CO2: C pi1 = 872.5 + 0.2406 * t1

[0056] H2O: C pi2 = 1833 + 0.3111 * t1

[0057] H2: C pi3 = 14330 + 0.5945 * t1

[0058] N2: C pi4 = 1032 + 0.08955 * t1

[0059] CO: C pi5 = 1035 + 0.09681 * t1

[0060] From this, the average constant pressure heat capacity C pgi of the gas inlet can be calculated as:

[0061]

[0062] In the formula, C pii is the constant pressure heat capacity of the i-th gas component at the inlet of the cooling device (J / (kgK)), i is 1, 2, 3, 4, 5; X i is the mass fraction of the i-th gas component.

[0063] Similarly, assuming t2 is the outlet temperature of the gas after cooling, i.e. the target value of cooling, the linear relationship of the constant pressure heat capacity of each gas component is as follows:

[0064] CO2: C po1 = 872.5 + 0.2406 x t2

[0065] H2O: C po2 = 1833 + 0.3111 x t2

[0066] H2: C po3 = 14330 + 0.5945 x t2

[0067] N2: C po4 = 1032 + 0.08955 x t2

[0068] CO: C po5 = 1035 + 0.09681 x t2

[0069] Thus, the average constant pressure heat capacity C pgo of the outlet gas can be obtained as:

[0070]

[0071] In the formula, C poi is the constant pressure heat capacity (J / (kg K)) of the i-th gas component at the outlet of the cooling device.

[0072] Step 4, on the basis of step 3, the total heat exchange Q z of the gas cooling process is further calculated, i.e.:

[0073]

[0074] In the formula, Q r is the mass flow of the gas (kg / s), T i is the inlet temperature of the gas (K), and T o is the temperature of the gas after cooling (K), i.e. the target value of the gas cooling.

[0075] Step 5, based on the inlet temperature of the gas and the target value of the gas cooling set in step 2, combined with the mass flow and the initial temperature before the injection of the cooling water, the heat absorbed by the cooling water during the cooling process is calculated as:

[0076]

[0077] In the formula, T i is the inlet temperature of the gas (K), and T o is the temperature of the gas after cooling (K), is the mass flow rate (kg) of the sprayed atomized water, is the specific heat capacity at constant pressure (J / (kg K)) of the liquid water, is the saturation temperature (K) of the water, is the initial temperature (K) of the sprayed atomized water, is the latent heat of vaporization (J / kg) of the water, is the specific heat capacity at constant pressure (J / (kg K)) of the water vapor.

[0078] Step 6, the theoretical water spraying amount of the cooling water in the cooling process is calculated by the total heat exchange amount obtained in Step 4 and the heat absorbed by the cooling water obtained in Step 5 i.e.

[0079]

[0080] Since the theoretical water spraying amount obtained by the calculation corresponds to the inlet and outlet temperatures of the gas in the cooling device, in actual application, the inlet and outlet temperatures, especially the outlet temperature value of the cooling device, can be adjusted according to the theoretical water spraying amount obtained by the calculation, and the appropriate water spraying amount can be obtained by iterative calculation. For example, if the provided water spraying amount is relatively large, the outlet temperature value of the gas can be appropriately reduced; if the provided water spraying amount is relatively small, the outlet temperature value of the gas can be appropriately increased. After the temperature value is adjusted, the specific heat capacity at constant pressure of the gas composition and subsequent calculation need to be recalculated until the adjusted water spraying amount is obtained.

[0081] Step 7, the actual water spraying amount Q of the cooling water in the cooling process is calculated according to the material properties of the cooling device, taking the safety factor as 1.1-1.25, and combining the theoretical water spraying amount lw is:

[0082]

[0083] Thus, the analysis and calculation of the cooling performance index of the attitude control engine high-altitude simulation test system are completed.

[0084] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the present application.

Claims

1. A method for analyzing and calculating the cooling performance indicators of an attitude control engine high-altitude simulation test system, characterized in that, Includes the following steps: Step 1: Based on the evaporation characteristics of cooling water in the cooling device of the attitude control engine high-altitude simulation test system, as well as the molar mass and temperature of the combustion gas components, the basic relationship between cooling water evaporation and combustion gas cooling during the cooling process is analyzed. Step 2: Based on Step 1, determine the gas parameters according to the properties of the combustion medium, and set the target cooling value of the gas according to the environmental simulation requirements of the engine; the gas parameters include the gas mass flow rate and gas composition of the combustion medium, as well as the molar mass of each gas component and the gas inlet temperature; Step 3: Based on the molar mass of each gas component, calculate the mass fraction of each gas component, and then calculate the average isobaric heat capacity of the gas inlet and the average isobaric heat capacity of the gas outlet. Step 4: Based on Step 3, and combining the gas mass flow rate of the combustion medium, the gas inlet temperature, and the gas cooling target value set in Step 2, the total heat exchange during the gas cooling process is further calculated. Step 5: Based on the mass flow rate of the cooling water during injection and its initial temperature before injection, calculate the heat absorbed by the cooling water during the cooling process. Step 6: Calculate the theoretical spray volume of cooling water during the cooling process using the total heat exchange obtained in Step 4 and the heat absorbed by the cooling water obtained in Step 5. Step 7: Determine the safety factor based on the material properties of the cooling device, and calculate the actual amount of cooling water sprayed during the cooling process by combining the theoretical water spray volume, thereby completing the analysis and calculation of the cooling index of the attitude control engine high-altitude simulation test system.

2. The method for analyzing and calculating the cooling performance index of the attitude control engine high-altitude simulation test system according to claim 1, characterized in that: In step 4, the total heat exchange Q z Calculated using the following formula: Q z =Q r ×(C pgi T i -C poi T o ) In the formula, Q r C represents the mass flow rate of the combustion medium. pgi Let C be the average isobaric heat capacity of the gas inlet, where i represents the i-th type of gas component, i≥1. poi T is the average isobaric heat capacity of the gas outlet. i T represents the gas inlet temperature. o This is the target value for cooling the gas.

3. The method for analyzing and calculating the cooling performance index of the attitude control engine high-altitude simulation test system according to claim 2, characterized in that: In step 5, the cooling water absorbs heat during the cooling process. Calculated using the following formula: In the formula, The specific heat capacity of liquid water at constant pressure. The saturation temperature of water. The initial temperature at which the atomized water is sprayed. The latent heat of vaporization of water, This is the isobaric specific heat capacity of water vapor.

4. The method for analyzing and calculating the cooling performance index of the attitude control engine high-altitude simulation test system according to claim 3, characterized in that: In step 6, the theoretical spray volume of the cooling water... Calculated using the following formula:

5. The method for analyzing and calculating the cooling performance index of the attitude control engine high-altitude simulation test system according to claim 1, characterized in that: In step 7, the safety factor is taken as 1.1 to 1.25.

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