Cooling performance index analysis and calculation method of attitude control engine high-altitude simulation test system

Abstract

The invention relates to a cooling performance index analysis and calculation method of an attitude control engine high-altitude simulation test system, and mainly solves the technical problem that the existing analysis method easily causes large deviation between a test result and an actual situation. The method comprises the following steps: firstly analyzing a basic relationship between cooling water evaporation and gas cooling in a cooling process, then setting a cooling target value of gas, and then sequentially calculating the mass fraction of each gas component, the average constant pressure heat capacity of a gas inlet and a gas outlet, the total heat exchange amount in the gas cooling process and the heat absorbed by cooling water in the cooling process; finally, the actual water spraying amount of the cooling water in the cooling process is calculated in combination with a safety coefficient, so that analysis and calculation of cooling performance indexes of the attitude control engine high-altitude simulation test system are completed, and the inlet temperature requirement of an injection system and the stability and reliability of the test system are guaranteed.

Description

Technical Field

[0001] The invention relates to a liquid rocket engine environment simulation test method, and in particular to a cooling performance index analysis and calculation method for an attitude control engine high-altitude simulation test system. Background Art

[0002] The attitude control engine is mainly used to control the attitude of the spacecraft. It can also be used for speed correction, orbit adjustment, position maintenance, etc. It is an indispensable power device for the process of spacecraft orbiter entry, re-entry, and terminal repair. The performance of the attitude control engine is crucial to the accuracy of the spacecraft's hit.

[0003] At present, the performance of attitude control engines is usually evaluated by using a high-altitude simulation test system (hereinafter referred to as the "test system"). The gas temperature in the combustion chamber of the test system can usually reach more than 3400K, which is very different from the temperature requirement of 300℃ at the inlet of the test system's ejector, thus affecting the ejection and 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 various equipment in the test system, which can easily cause serious ablation or even damage to the test system.

[0004] In order to solve the above problems, water injection and spraying are usually used to cool down the high-temperature gas generated by the test system. Therefore, the feasibility of the cooling scheme is particularly important. The existing technology first calculates the heat exchange between cooling water and high-temperature gas, and then adjusts the injection amount of cooling water in real time during the cooling process based on work experience. This method can achieve a good cooling effect, but since the operator lacks a theoretical basis for adjusting the injection amount based on experience, there is a deviation between the calculated results and the actual situation, so the injection amount of cooling water needs to be adjusted continuously. At the same time, due to the continuous adjustment of the cooling water injection amount, the instability of the test system increases, and the test system presents dynamic changes, which can easily lead to a large deviation between the test results and the actual situation, and ultimately cause the engine performance evaluation to be inconsistent with the actual situation. Summary of the invention

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

[0006] To achieve the above objectives, the technical solutions provided by the present invention are:

[0007] A method for analyzing and calculating a cooling index of an attitude control engine high-altitude simulation test system, which is special in that it includes the following steps:

[0008] 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 of the gas components and the gas temperature, the basic relationship between the evaporation of cooling water and the cooling of the gas during the cooling process is analyzed;

[0009] Step 2: Based on step 1, determine the gas parameters according to the properties of the combustion medium, and set the gas temperature reduction target value according to the environmental simulation requirements of the engine; the gas parameters include the gas mass flow rate of the combustion medium, the gas components and the molar mass of each gas component, and the gas inlet temperature;

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

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

[0012] Step 5: Based on the mass flow rate of cooling water during injection and its initial temperature before injection, the heat absorbed by the cooling water during the cooling process is calculated;

[0013] Step 6, calculating the theoretical spraying amount of cooling water in the cooling process by the total heat exchange obtained in step 4 and the heat absorbed by the cooling water obtained in step 5;

[0014] Step 7: Determine the safety factor based on the material properties of the cooling device, and calculate the actual water spray volume of the cooling water in the cooling process in combination with the theoretical water spray volume, thereby completing the analysis and calculation of the cooling performance indicators of the attitude control engine high-altitude simulation test system.

[0015] Further, in step 4, the total heat exchange Q z 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 rate of the combustion medium, C pgi is the average constant-pressure heat capacity of the gas inlet, i represents the i-th gas component, i≥1, C poi is the average constant pressure heat capacity of the gas outlet, T i is the gas inlet temperature, T o It is the target value for gas temperature reduction.

[0018] Furthermore, in step 5, the heat absorbed by the cooling water during the cooling process Calculated by the following formula:

[0019]

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

[0021] Furthermore, in step 6, the theoretical spraying amount of the cooling water is Calculated by the following formula:

[0022]

[0023] Furthermore, in step 7, the safety factor is 1.1 to 1.25.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The present invention analyzes the relationship between cooling water evaporation and gas cooling during the cooling process, and calculates the core parameters in the heat exchange process between gas and cooling water in combination with the properties of the combustion medium, thereby obtaining the actual spray volume of cooling water during the cooling process. This method can accurately analyze the cooling process of the test system, thereby ensuring that the test environment is consistent with the actual environment of the engine, and ultimately accurately evaluating the actual performance of the engine.

[0026] 2. The calculation process of the present invention is carried out according to the specific parameters of the fuel gas, so that the actual spraying amount of cooling water can be accurately obtained to ensure the stability of the working of the test system.

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

[0028] Figure 1 Schematic diagram of a flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, advantages and features of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

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

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

[0032] This embodiment first analyzes the heat balance of the active cooling process of vacuum injection combustion gas. According to the evaporation characteristics of the cooling water in the cooling device of the attitude control engine high-altitude simulation test system, combined with the test system parameters and the working environment conditions, the surface of the cooling water droplets and the radiation heat transfer process are analyzed to obtain the heat balance equation for the combustion gas water spray cooling. The subsequent calculation and analysis are then carried out based on this heat balance equation.

[0033] First, the continuous phase flow field of the gas in the test system is calculated. After the continuous phase flow field of the gas is stable, the physical processes of the discrete phase flow, injection, evaporation, and heat exchange of the cooling water droplets are calculated. Under the premise of considering the evaporation characteristics of cooling water, this embodiment simplifies the analysis process of high-temperature gas water spray cooling. For the heat balance in the process of active cooling of vacuum-injected gas, when the cooling water temperature is lower than its evaporation temperature T vap , the laws for heating or cooling of droplets (liquid cooling water) apply, in which case:

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

[0035] Where: 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 begins to evaporate, the diffusion of droplets into the gas phase is mainly related to the concentration between the two, namely:

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

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

[0039] As the cooling water continues to evaporate, the mass of the droplets will also be consumed. The mass consumption of the droplets is:

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

[0041] Where: 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 is the gas temperature, and Δt is the change in gas temperature.

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

[0043]

[0044] Where: c p is the constant pressure specific heat of the drop; 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; p is the particle blackness; σ is the Stephens-Boltzmann constant; θ R is the radiation temperature, T R is the absorption temperature.

[0045] Based on the heat balance equation of the gas water spray cooling process obtained from the above analysis, the basic relationship between cooling water evaporation and temperature reduction in the water spray cooling process can be obtained, thereby providing a theoretical basis for the analysis and calculation of cooling indicators under the premise of considering the cooling water evaporation rate.

[0046] Step 2: Based on step 1, determine the gas parameters according to the properties of the combustion medium, and set the gas temperature reduction target value according to the engine environmental simulation requirements, which is the gas outlet temperature.

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

[0048] Step 3: Calculate the mass fraction of each gas component based on the molar mass of each gas component, and then calculate the average constant-pressure heat capacity of the gas inlet and the average constant-pressure heat capacity of the gas outlet.

[0049] First, assume that the gas mass flow rate of the gas medium is Q r Taking hydrazine, a common combustion medium in attitude control engines, as an example, its fuel gas components are mainly CO, H2O, H2, N2, and CO2. The molar masses of each fuel gas component are Y CO , The average molecular weight u of the fuel gas is calculated, namely:

[0050]

[0051] In the formula, u CO , are the molecular weights of each fuel gas component.

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

[0053]

[0054] At this time, assuming that t1 is the gas inlet temperature, the linear relationship between 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 of the gas inlet can be calculated pgi for:

[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 that t2 is the outlet temperature of the gas after cooling, that is, the cooling target value, the linear relationship between the constant pressure heat capacity of each gas component is as follows:

[0064] CO2:C po1 =872.5+0.2406×t2

[0065] H2O:C po2 =1833+0.3111×t2

[0066] H2: C po3 =14330+0.5945×t2

[0067] N2:C po4 =1032+0.08955×t2

[0068] CO:C po5 =1035+0.09681×t2

[0069] From this, the average constant pressure heat capacity C of the gas outlet can be obtained pgo for:

[0070]

[0071] Where: C poi is the constant-pressure heat capacity of the ith gas component at the outlet of the cooling device (J / (kgK)).

[0072] Step 4: Based on step 3, further calculate the total heat exchange Q of the gas cooling process z ,Right now:

[0073]

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

[0075] Step 5: Based on the gas inlet temperature and the gas cooling target value set in step 2, combined with the mass flow rate of cooling water injection and its initial temperature before injection, calculate the heat absorbed by the cooling water during the cooling process.

[0076]

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

[0078] Step 6: Calculate the theoretical spray volume of cooling water during the cooling process by using the total heat exchange obtained in step 4 and the heat absorbed by the cooling water obtained in step 5. Right now:

[0079]

[0080] The theoretical water spray volume calculated by this method Corresponding to the inlet and outlet temperatures of the gas in the cooling device, therefore, in practical applications, the inlet and outlet temperatures can be adjusted according to the calculated theoretical water spray volume, especially the outlet cooling temperature value, and the appropriate water spray volume can be iteratively calculated. For example, if a large amount of water spray is provided, the temperature value of the gas outlet can be appropriately reduced; if a small amount of water spray is provided, the temperature value of the gas outlet can be appropriately increased. After the temperature value is adjusted, the constant pressure heat capacity of the gas component and subsequent calculations need to be recalculated until the adjusted water spray volume is obtained.

[0081] Step 7: In this embodiment, according to the material properties of the cooling device, a safety factor of 1.1 to 1.25 is taken, and combined with the theoretical water spraying volume, the actual water spraying volume Q of the cooling water in the cooling process is calculated. lw for:

[0082]

[0083] This completes the analysis and calculation of the cooling performance indicators of the attitude control engine high-altitude simulation test system.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A cooling performance index analysis and calculation method for an attitude control engine high-altitude simulation test system, characterized in that: The following steps are involved: 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 of the gas components and the gas temperature, the basic relationship between the evaporation of cooling water and the cooling of the gas 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 gas temperature reduction target value according to the environmental simulation requirements of the engine; the gas parameters include the gas mass flow rate of the combustion medium, the gas components and the molar mass of each gas component, and the gas inlet temperature; Step 3: Calculate the mass fraction of each gas component according to the molar mass of each gas component, and then calculate the average constant-pressure heat capacity of the gas inlet and the average constant-pressure heat capacity of the gas outlet; Step 4: Based on step 3, the total heat exchange amount of the gas cooling process is further calculated by combining the gas mass flow rate of the combustion medium, the gas inlet temperature and the gas cooling target value set in step 2; Step 5: Based on the mass flow rate of cooling water during injection and its initial temperature before injection, the heat absorbed by the cooling water during the cooling process is calculated; Step 6, calculating the theoretical spraying amount of cooling water in the cooling process by 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 water spray volume of the cooling water in the cooling process in combination with 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 cooling performance index analysis and calculation method of the attitude control engine high-altitude simulation test system according to claim 1 is characterized by: In step 4, the total heat exchange Q z Calculated by the following formula: Q z =Q r ×(C pgi T i -C poi T o ) In the formula, Q r is the gas mass flow rate of the combustion medium, C pgi is the average constant-pressure heat capacity of the gas inlet, i represents the i-th gas component, i≥1, C poi is the average constant pressure heat capacity of the gas outlet, T i is the gas inlet temperature, T o It is the target value for gas temperature reduction.

3. The cooling performance index analysis and calculation method of the attitude control engine high-altitude simulation test system according to claim 2 is characterized by: In step 5, the heat absorbed by the cooling water during the cooling process Calculated by the following formula: In the formula, is the mass flow rate of sprayed atomized water, is the specific heat of liquid water at constant pressure, is the saturation temperature of water, is the initial temperature of the sprayed atomized water, is the latent heat of vaporization of water, is the specific heat of water vapor at constant pressure.

4. The cooling performance index analysis and calculation method of the attitude control engine high-altitude simulation test system according to claim 3 is characterized by: In step 6, the theoretical spraying amount of the cooling water is Calculated by the following formula:

5. The cooling performance index analysis and calculation method of the attitude control engine high-altitude simulation test system according to claim 1 is characterized by: In step 7, the safety factor is 1.1 to 1.25.

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