Accurate prediction and control method for liquid oxygen filling inlet temperature of low-temperature carrier rocket

Abstract

A low-temperature carrier rocket liquid oxygen filling inlet temperature accurate prediction and control method is characterized in that the method is applied to a low-temperature carrier rocket liquid oxygen filling pipeline, and the method comprises the steps that 1, a liquid oxygen inlet temperature prediction model is constructed; step 2, constructing a liquid oxygen rocket inlet temperature accurate control model; the model is designed as a smart application of a smart launch site. On-site operation filling system parameters are read in real time to serve as input conditions, real-time prediction of the inlet rocket temperature is conducted, and control strategy guidance is provided according to the target temperature requirement of the storage tank.

Description

Technical Field

[0001] The present invention belongs to the field of rocket launch, and relates to a method for predicting and precisely controlling the temperature of liquid oxygen filled into a rocket. Background Art

[0002] Propellant filling is a process of delivering propellant to the rocket tank on time, in accurate quantity, and safely. As the only oxidizer in the propellant combinations of cryogenic launch vehicle engines in modern space missions, such as liquid oxygen-kerosene, liquid oxygen-methane, and liquid oxygen-liquid hydrogen, liquid oxygen plays an important role in cryogenic rockets. Liquid oxygen filling participates in the rocket test launch process and ends with subcooled topping-up near the launch time. Therefore, the safety and control accuracy of its filling process directly affect the success or failure of the launch.

[0003] Currently, although foreign cryogenic rockets such as Falcon 9 and Starship have adopted the deep subcooled liquid oxygen filling process to achieve multi-component parallel autonomous filling, most domestic active rockets use the conventional oxygen filling - parking - subcooled topping-up filling mode. During the conventional oxygen parking stage, the evaporation loss of liquid oxygen is relatively large, and the loss amount is greatly related to the local air pressure, ambient temperature, and the temperature of liquid oxygen entering the rocket. Among these factors, the temperature of liquid oxygen entering the rocket plays a dominant role. Therefore, it is of great practical significance to study the precise prediction and control method of the temperature of liquid oxygen entering the rocket.

[0004] Domestic scholars have shown extensive concern for the liquid oxygen filling process flow and control technology. Jiang Dongling, Yang Ying, etc. have carried out research on the influence of liquid oxygen temperature on the performance of a certain liquid oxygen-liquid hydrogen engine [1] , and proposed that the performance of cryogenic liquid rocket engines is affected by various interference factors. Among them, the liquid oxygen temperature first affects the engine performance as an external factor. For the same engine, there will be significant differences in performance under different inlet propellant temperature conditions. Ma Yuan, etc. have carried out the analysis and experimental research on the subcooling degree of liquid oxygen propellant [2] . Gao Wanli, Zheng Pingjun, etc. have carried out preliminary simulation calculations and explorations on the control of propellant temperature [3][4] . Ren Jianhua, Lei Gang, Xie Fushou, etc. have carried out a comparative analysis of large-flow deep subcooling schemes for liquid oxygen [5] . Sun Qiang, Ma Yuan, etc. have carried out a comparative analysis and experimental research on cryogenic liquid oxygen subcooling schemes [6] . Zhang Qing, etc. have carried out preliminary research on the mixing of conventional oxygen and subcooled oxygen [7] . This method aims to reduce the filling temperature of conventional oxygen by naturally mixing conventional oxygen and subcooled oxygen, but it cannot achieve precise control of the liquid oxygen temperature. The mixing temperature largely depends on the flow rate of subcooled oxygen and the saturation temperature of conventional oxygen, with great uncertainty. Dai Huaping, etc. have published a liquid oxygen full subcooling filling system for rockets, which can subcool liquid oxygen to about 78K through double liquid nitrogen subcooling, realizing the deep subcooling filling of liquid oxygen.

[0005] There is a significant influence relationship between the temperature of cryogenic propellant and its density. The density of propellant affects the calculation results of rocket filling parameters, which in turn affects the accuracy of the rocket entering the predetermined orbit. During the conventional oxygen filling and parking of a certain cryogenic rocket, due to its slow exhaust speed, the temperature of liquid oxygen is difficult to drop to the boiling point temperature corresponding to the local saturated atmospheric pressure. The conventional oxygen temperature is greatly affected by the temperature of liquid oxygen entering the rocket, which brings great difficulties to the accurate prediction of the liquid oxygen filling temperature in the calculation of filling parameters.

[0006] In order to ensure the stability of the temperature of the rocket during conventional oxygen filling, it is necessary to minimize the changes in various influencing factors. However, in actual operating conditions, the temperature of the cryogenic propellant entering the rocket is related to many factors such as the storage temperature, the pressure of the cryogenic storage tank, and the external ambient temperature. Therefore, the liquid oxygen filling temperature cannot be accurately controlled, which often causes the actual filling amount to be close to the safety margin calculated by various parameters.

[0007] Domestic related research only provides that the temperature can be controlled by adjusting the subcooler and the conventional oxygen pipeline regulating valve. There is no related research and patent on how to accurately control the temperature and how to control the filling equipment. A numerical calculation model for accurate prediction and control of liquid oxygen filling temperature has not been established to specifically guide the strategic control of filling system process equipment. The precise control strategy for propellant feeding temperature proposed in this paper has actually verified the accuracy of the model in the launch site cryogenic filling system and further expanded its temperature application range. According to the numerical calculation results, this model is effective for 63.2K (liquid nitrogen triple point) to 77.3K (normal pressure liquid nitrogen saturation temperature) [5] The same applies to the cryogenic temperature range of liquid oxygen. Therefore, the present invention conducts research on the precise prediction and control strategy of the temperature of cryogenic rocket liquid oxygen, which has important practical significance for reducing liquid oxygen filling loss, shortening liquid oxygen filling time, accurately controlling the quality of propellant filling, and accurately controlling the flight process of the carrier rocket.

[0008] At present, the combined process flow of conventional oxygen filling followed by supercooled oxygen replenishment after parking adopted by most cryogenic rockets in China cannot achieve accurate prediction of liquid oxygen filling temperature. Summary of the invention

[0009] The purpose of the present invention is to provide a method for predicting and accurately controlling the temperature of liquid oxygen filling into a rocket. In view of the importance of temperature control of liquid oxygen filling into a rocket on the accuracy of rocket flight into orbit, there is a deviation between the predicted temperature of various parameters and the actual filling temperature. In order to improve the accuracy of liquid oxygen filling temperature matching, the process characteristics of liquid oxygen filling are studied, and an accurate prediction and control model of liquid oxygen filling temperature is established. The correctness of the model is verified by experiments on an actual low-temperature filling system, which provides theoretical support and method guidance for formulating accurate and effective control strategies for temperature control in the liquid oxygen filling process, thereby improving the accuracy and adaptability of liquid oxygen filling guarantee.

[0010] The present invention provides a method for accurately predicting and controlling the temperature of liquid oxygen injected into a cryogenic launch vehicle. The method is characterized in that it is applied to the liquid oxygen injection pipeline of a cryogenic launch vehicle, and the method includes the following steps:

[0011] Step 1, construct a prediction model for the temperature of liquid oxygen entering the rocket;

[0012] Step 2, construct an accurate control model for the temperature of liquid oxygen entering the rocket.

[0013] Preferably, in step 1, through the known normal oxygen temperature T 1 , subcooled oxygen temperature T 2 , normal oxygen pipeline valve opening KD 1 , subcooled oxygen pipeline valve opening and related parameters KD 2 , calculate the temperature T of the mixed liquid oxygen H .

[0014] Preferably, in step 1,

[0015] According to the heat calculation formula,

[0016] Q 1 =cm 1 Δt 1 (1)

[0017] Q 2 =cm 2 Δt 2 (2)

[0018] Q 1 =Q 2 (3)

[0019] Δt 1 =T 1 -T H (4)

[0020] Δt 2 =T H -T 2 (5)

[0021] (4)+(5) gives:

[0022] Δt 1 +Δt 2 =T 1 -T 2 (6)

[0023] Substituting equations (1) and (2) into equation (3), we can get

[0024] cm 1 Δt 1 =cm 2 Δt 2(7)

[0025] Among them, c is the specific heat capacity of liquid oxygen, and the mass of the medium participating in the heat exchange of conventional oxygen is m 1 = ρ 1 V 1 , ρ 1 is the density of the medium participating in the heat exchange. The density of liquid oxygen changes with temperature and is obtained by querying the Nist software; the mass of the medium participating in the heat exchange of subcooled oxygen is m 2 = ρ 2 V 2 , ρ 2 is the density of subcooled oxygen

[0026] Among them

[0027]

[0028] In the formula, KD 1 is the valve opening of the regulating valve in the conventional oxygen pipeline, KD 2 is the valve opening of the conventional oxygen pipeline, and f(KD 1 ), f(KD 2 ) are the functional relationships between the valve opening and the pipeline cross-sectional area; substituting (8) and (9) into equation (7) gives:

[0029] cρ 1 V 1 Δt 1 = cρ 2 V 2 Δt 2 (10)

[0030]

[0031] It can be calculated that the temperature after mixing is:

[0032]

[0033] Let Then

[0034]

[0035] Therefore, the temperature of the liquid oxygen after mixing is predicted according to the above model.

[0036] Preferably, in step 2, according to the heat calculation formula, from (12) we get

[0037]

[0038] From (14), the relationship C between the opening degrees of the subcooled oxygen and conventional oxygen pipelines can be obtained;

[0039]

[0040] When C > 1, set the opening degree of the subcooled oxygen pipeline to KD 2 = 80% - 100%. Since the flow characteristics in the pipeline where the regulating valve is set in this range are better, then Calculate the opening degree of the regulating valve of the conventional oxygen pipeline according to the corresponding relationship between the opening degree of the regulating valve and the actual cross-sectional area, and provide the control basis for the filling equipment;

[0041] If C ≤ 1, set the opening degree of the regulating valve of the conventional oxygen pipeline to the opening degree KD with smaller pipeline flow resistance and better low-temperature flow characteristics 1 = 80% - 100%. If the relationship between the opening degree and the cross-sectional area is linear, then the opening degree of the subcooled oxygen pipeline regulating valve can be obtained as KD 2 = KD 1 × C × 100%. In the application of the model, the relationship between the valve opening degree and the pipeline cross-sectional area depends on the actual system.

[0042] In view of the difficulty in accurately predicting the liquid oxygen filling temperature in the calculation of the conventional oxygen filling parameters, the present invention proposes a method of mixing conventional oxygen and subcooled oxygen in a certain proportion, establishes a numerical calculation heat transfer model, and verifies the accuracy of the model through the actual experimental data of the launch site. Research on the prediction and control strategy of the liquid oxygen temperature after mixing is carried out to achieve the purpose of accurately predicting the liquid oxygen temperature entering the rocket and intelligent regulation. Moreover, this regulation method is also applicable to the accurate prediction and control of the liquid oxygen temperature in the deep subcooled temperature region, which has important practical significance. Description of the Drawings

[0043] Figure 1 It is a schematic diagram of the liquid oxygen filling pipeline for the first stage of a cryogenic rocket;

[0044] Figure 2 It is the temperature change of each measuring point in the pipeline when the first-stage pipeline is set to working condition 1;

[0045] Figure 3 It is the temperature of each measuring point in the pipeline after the temperature is stabilized under the first-stage working condition 1;

[0046] Figure 4 It is the temperature change of each measuring point in the pipeline when the first-stage pipeline is set to working condition 2;

[0047] Figure 5 It is the temperature of each measuring point in the pipeline after the temperature is stabilized under the first-stage working condition 2;

[0048] Figure 6 It is the temperature change of each measuring point in the pipeline when the first-stage pipeline is set to working condition 3;

[0049] Figure 7 It is the temperature of each measuring point in the pipeline after the temperature is stabilized under the first-stage working condition 3;

[0050] Figure 8 The temperature change of each measuring point in the pipeline when the secondary pipeline is set to operating condition 1;

[0051] Figure 9 The temperature of each measuring point in the pipeline after the temperature stabilizes under the secondary operating condition 1;

[0052] Figure 10 The temperature change of each measuring point in the pipeline when the secondary pipeline is set to operating condition 2;

[0053] Figure 11 The temperature change of each measuring point in the pipeline when the secondary pipeline is set to operating condition 3. Specific implementation mode

[0054] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0055] The present invention provides a method for accurately predicting and controlling the temperature of liquid oxygen injected into a cryogenic launch vehicle during injection. The method is applied to the liquid oxygen injection pipeline of a cryogenic launch vehicle.

[0056] Such as Figure 1 , the liquid oxygen injection usually boosts through a vaporizer or a cryogenic pump as the injection power to transport the cryogenic propellant in the cryogenic vacuum storage tank into the storage tank. The domestic liquid oxygen injection process usually adopts procedures such as conventional oxygen injection first, then liquid oxygen parking, and finally subcooled supplementary addition to complete the injection task. During the conventional oxygen stage, the cryogenic propellant is transported through the conventional oxygen pipeline. During the subcooled supplementary addition stage, liquid nitrogen in the subcooler is used as a refrigerant to reduce the temperature of the liquid oxygen, and then it is transported into the rocket storage tank. The temperature of the propellant is affected by many factors such as ambient temperature, tank pressure, flow rate, and liquid level. If the deviation between the actual injection temperature and the predicted temperature at the rocket launch time is large, during the injection process, the temperature of the liquid oxygen injected into the rocket can be accurately controlled by mixing oxygen injection, so that the temperature of the propellant in the actual storage tank is closer to the predicted result of the element calculation temperature. T 1 is the temperature of the conventional oxygen in the injection pipeline, T 2 is the temperature of the subcooled oxygen after passing through the subcooler, T H is the temperature of the liquid oxygen after mixing the conventional oxygen and the subcooled oxygen, T Z is the temperature of the injection into the rocket, KD 1 is the opening degree of the regulating valve of the conventional oxygen injection pipeline, KD 2 is the opening degree of the regulating valve of the injection pipeline after passing through the subcooler, P 1 is the pressure of the cryogenic vacuum storage tank, P 2 is the pressure in the rocket storage tank.

[0057] The method includes the steps:

[0058] Step 1, construct a predicted model for the temperature of liquid oxygen entering the rocket.

[0059] Step 2, construct an accurate control model for the temperature of liquid oxygen entering the rocket.

[0060] Design the model as an intelligent application of the intelligent launch site. Read the parameters of the on-site operation filling system in real time as input conditions, perform real-time prediction of the temperature entering the rocket, and provide control strategy guidance according to the target temperature requirements of the storage tank.

[0061] According to an embodiment of the present invention, in Step 1, through the known normal oxygen temperature T 1 , subcooled oxygen temperature T 2 , normal oxygen pipeline valve opening KD 1 , subcooled oxygen pipeline valve opening and related parameters KD 2 , calculate the temperature T of the mixed liquid oxygen H .

[0062] According to an embodiment of the present invention, in Step 1,

[0063] According to the heat calculation formula,

[0064] Q 1 =cm 1 Δt 1 (1)

[0065] Q 2 =cm 2 Δt 2 (2)

[0066] Q 1 =Q 2 (3)

[0067] Δt 1 =T 1 -T H (4)

[0068] Δt 2 =T H -T 2 (5)

[0069] (4)+(5) gives:

[0070] Δt 1 +Δt 2 =T 1 -T 2 (6)

[0071] Substitute equations (1) and (2) into equation (3), and we can get

[0072] cm 1 Δt1 = cm 2 Δt 2 (7)

[0073] Among them, c is the specific heat capacity of liquid oxygen, and the mass of the medium participating in heat exchange of conventional oxygen is m 1 = ρ 1 V 1 ρ 1 is the density of the medium participating in heat exchange. The density of liquid oxygen changes with temperature and is obtained by querying the Nist software; the mass of the medium participating in heat exchange of subcooled oxygen is m 2 = ρ 2 V 2 ρ 2 is the density of subcooled oxygen

[0074] Among them

[0075]

[0076] In the formula, KD 1 is the valve opening of the regulating valve of the conventional oxygen pipeline, KD 2 is the valve opening of the conventional oxygen pipeline, and f(KD 1 ), f(KD 2 ) are the functional relationships between the opening and the pipeline cross-sectional area; substituting (8) and (9) into formula (7) gives:

[0077] cρ 1 V 1 Δt 1 = cρ 2 V 2 Δt 2 (10)

[0078]

[0079] It can be calculated that the temperature after mixing is:

[0080]

[0081] Let Then

[0082]

[0083] Therefore, the temperature of the liquid oxygen after mixing is predicted according to the above model

[0084] According to an embodiment of the present invention, in step 2, according to the heat calculation formula, from (12) we get

[0085]

[0086] From (14), the opening degree relationship C of the subcooled oxygen and conventional oxygen pipelines can be obtained;

[0087]

[0088] When C > 1, set the opening degree of the subcooled oxygen pipeline to KD 2 = 80% - 100%. Since the flow characteristics in the pipeline within this range are better for the regulating valve, then Calculate the opening degree of the regulating valve of the conventional oxygen pipeline according to the corresponding relationship between the opening degree of the regulating valve and the actual cross-sectional area, providing a control basis for the filling equipment;

[0089] If C ≤ 1, set the opening degree of the regulating valve of the conventional oxygen pipeline to the opening degree KD with smaller pipeline flow resistance and better low-temperature flow characteristics 1 = 80% - 100%. If the relationship between the opening degree and the cross-sectional area is linear, then the opening degree of the regulating valve of the subcooled oxygen pipeline can be obtained as KD 2 = KD 1 × C × 100%. In the application of the model, the relationship between the valve opening degree and the pipeline cross-sectional area depends on the actual system.

[0090] The following is illustrated by an example. During a certain liquid oxygen debugging, a mixing experiment of subcooled oxygen and conventional oxygen in a liquid oxygen filling system for a certain cryogenic rocket was carried out, that is, subcooled oxygen and conventional oxygen were combined in different proportions, and the temperature change of the liquid oxygen in the pipeline after mixing was analyzed. The experiment aimed to analyze the temperature change of the mixed oxygen in the pipeline under different working conditions of the liquid oxygen filling system. The liquid oxygen filling system is divided into two levels. The specification of the conventional oxygen pipeline in the first level is DN150, and the subcooler pipeline is DN100; the conventional oxygen pipeline in the second level is DN100, and the subcooler pipeline is DN100. Low-temperature pneumatic regulating valves are respectively set for the conventional oxygen pipeline and the subcooled pipeline, and the ratio of conventional oxygen to subcooled oxygen in the mixed oxygen is controlled by adjusting the valve opening degree.

[0091] Four working conditions were set during the experiment, which were respectively:

[0092] Working condition 1: The regulating valve of the conventional oxygen pipeline is set to 90%, and the regulating valve of the subcooled oxygen pipeline is set to 90%;

[0093] Working condition 2: The regulating valve of the conventional oxygen pipeline is set to 50%, and the regulating valve of the subcooled oxygen pipeline is set to 90%;

[0094] Working condition 3: The regulating valve of the conventional oxygen pipeline is set to 90%, and the regulating valve of the subcooled oxygen pipeline is set to 50%;

[0095] Working condition 4: The regulating valve of the conventional oxygen pipeline is set to 50%, and the regulating valve of the subcooled oxygen pipeline is set to 50%... Data analysis of the experimental results of the primary mixed oxygen:

[0096] 1) Primary working condition 1

[0097] When the primary pipeline is set to operating condition 1, the temperature changes at each measuring point in the filling pipeline are as shown in Figure 2. From Figure 3 It can be seen that when the opening degrees of the regulating valves of the subcooled oxygen and conventional oxygen pipelines are both set to 90%, the temperature of the conventional oxygen is 92.1K, the temperature of the subcooled oxygen is 77.0K. After mixing, the temperature in the pipeline is 88.6K. After about 6 minutes, the temperature at the arrow inlet at the end of the pipeline is 88.6K.

[0098] 2) Primary operating condition 2

[0099] When the primary pipeline is set to operating condition 2, the temperature changes at each measuring point in the filling pipeline are as shown in the figure. From Figure 5 It can be seen that when the opening degree of the regulating valve of the subcooled oxygen pipeline is set to 90% and the opening degree of the regulating valve of the conventional oxygen pipeline is set to 50%, the temperature of the conventional oxygen is 92.2K, the temperature of the subcooled oxygen is 77.4K. After mixing, the temperature in the pipeline is 85.5K. After mixing for about 4 minutes, the temperature at the pre-injection valve at the end of the pipeline drops and stabilizes at 85.7K. The proportion of subcooled oxygen in the mixed oxygen in operating condition 2 is relatively high, and the temperature of the obtained mixed oxygen is lower than that in operating condition 1.

[0100] 3) Primary operating condition 3

[0101] When the primary pipeline is set to operating condition 3, the temperature changes at each measuring point in the filling pipeline are as shown in the figure. From Figure 7 It can be seen that when the opening degree of the regulating valve of the subcooled oxygen pipeline is set to 50% and the opening degree of the regulating valve of the conventional oxygen pipeline is set to 90%, the temperature of the conventional oxygen is 92.4K, the temperature of the subcooled oxygen is 76.9K. After mixing, the temperature in the pipeline is 90.2K. After about 5 minutes, the temperature at the pre-injection valve at the end of the pipeline rises and stabilizes at 90.2K. The proportion of conventional oxygen in the mixed oxygen in operating condition 3 is relatively high, and the temperature of the obtained mixed oxygen is higher than that in operating conditions 1 and 2, which is in line with the actual situation.

[0102] Analysis of the experimental results data of the secondary mixed oxygen:

[0103] 1) Secondary operating condition 1

[0104] When the secondary pipeline is set to operating condition 1, the temperature changes at each measuring point in the pipeline are as shown in the figure. From Figure 9 It can be seen that when the opening degrees of the regulating valves of the subcooled oxygen and conventional oxygen pipelines are both set to 90%, the temperature of the conventional oxygen is 94.8K, the temperature of the subcooled oxygen is 77.1K. After mixing, the temperature in the pipeline is 86.5K. After about 7 minutes, the temperature at the arrow inlet at the end of the pipeline is 86.5K.

[0105] 2) Secondary operating condition 2

[0106] When the secondary pipeline is set to operating condition 2, the temperature changes at each measuring point in the filling pipeline are as Figure 10As shown in the figure. It can be seen from the figure that when the opening degree of the subcooled oxygen pipeline regulating valve is set to 90% and the opening degree of the conventional oxygen pipeline regulating valve is set to 50%, the temperature of the conventional oxygen is 94.2K, the temperature of the subcooled oxygen is 76.8K. After mixing, the temperature in the pipeline is 83.2K. About 4 minutes after mixing, the temperature at the end of the pipeline entering the rocket drops and stabilizes at 83.5K. In condition 2, the proportion of subcooled oxygen in the mixed oxygen is relatively high, and the obtained temperature of the mixed oxygen is lower than that in condition 1, which is in line with the actual situation.

[0107] 3) Secondary condition 3

[0108] When the secondary pipeline is set to condition 3, the temperature change of each measuring point in the filling pipeline is as Figure 1 shown. It can be seen from the figure that when the opening degree of the subcooled oxygen pipeline regulating valve is set to 50% and the opening degree of the conventional oxygen pipeline regulating valve is set to 90%, the temperature of the conventional oxygen is 94.3K, the temperature of the subcooled oxygen is 76.3K. After mixing, the temperature in the pipeline is 88.5K. About 5 minutes after mixing, the temperature at the front of the valve at the end of the pipeline rises and stabilizes at 88.8K. In condition 3, the proportion of conventional oxygen in the mixed oxygen is relatively high, and the obtained temperature of the mixed oxygen is higher than that in condition 1 and condition 2, which is in line with the actual situation.

[0109] The comparative analysis of the model calculation results is as follows:

[0110] Under the four conditions of the primary and secondary levels respectively, the liquid oxygen temperature after mixing is calculated through the conventional oxygen temperature prediction model. The comparison between the calculation results and the experimental data is shown in Table 1.

[0111] The data comparison is shown in Table 1.

[0112] Table 1 Comparison of the experimentally approved subcooled temperatures of the mixed oxygen

[0113]

[0114]

[0115] Verified by the measured data, the method of mixing subcooled oxygen and conventional oxygen can achieve different subcooled oxygen filling temperatures, and the system scheme is correct.

[0116] The present invention envisions mixing conventional oxygen and subcooled oxygen to reach the target temperature, establishes an accurate prediction and control model for the temperature of the liquid oxygen filling system entering the rocket in the boiling point temperature range based on the heat transfer calculation formula, analyzes the experimental data, and compares and verifies with the model prediction results. The results show that the model prediction results are in good agreement with the experimental data, and the accuracy is within 1%. It provides data support and technical guidance for formulating the accurate prediction and control strategy of the liquid oxygen filling temperature of a certain cryogenic rocket, and provides an effective way to better ensure the temperature of the liquid oxygen entering the rocket. At the same time, it provides theoretical guidance for optimizing the subsequent filling process.

[0117] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and alternatives to the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A method for accurately predicting and controlling the temperature of liquid oxygen filling into a cryogenic launch vehicle, characterized in that: The method is applied to a liquid oxygen filling pipeline of a cryogenic launch vehicle, and the method comprises the steps of: Step 1, constructing a liquid oxygen feeding temperature prediction model; Step 2: Construct a precise temperature control model for liquid oxygen entering the rocket.

2. The method for accurately predicting and controlling the temperature of liquid oxygen filling into a cryogenic launch vehicle according to claim 1 is characterized in that: In step 1, by knowing the normal oxygen temperature T1, the subcooled oxygen temperature T2, the normal oxygen pipeline valve opening KD1, the subcooled oxygen pipeline valve opening and related parameters KD2, the mixed liquid oxygen temperature T H .

3. The method for accurately predicting and controlling the temperature of liquid oxygen filling into a cryogenic launch vehicle according to claim 1 is characterized in that: In step 1, According to the heat calculation formula, Q1=cm1Δt1(1) Q2=cm2Δt2(2) Q1=Q2(3) Δt1=T1-T H (4) Δt2=T H -T2 (5) (4)+(5) gives: Δt1+Δt2=T1-T2(6) Substituting equations (1) and (2) into equation (3), we can obtain cm1Δt1=cm2Δt2 (7) Where c is the specific heat capacity of liquid oxygen, the mass of the medium participating in heat exchange with conventional oxygen is m1=ρ1V1, ρ is the density of saturated oxygen participating in heat exchange, and the density of liquid oxygen changes with temperature, which is obtained by querying Nist software; the mass of the medium participating in heat exchange with supercooled oxygen is m2=ρ2V2, ρ2 is the density of supercooled oxygen, where Where KD1 is the opening of the conventional oxygen pipeline regulating valve, KD2 is the opening of the conventional oxygen pipeline valve, f(KD1) and f(KD2) are the functional relationships between the opening and the pipeline cross-sectional area. Substituting (8) and (9) into (7), we get: cρ1V1Δt1=cρ2V2Δt2 (10) The temperature after mixing can be calculated as: set up but Therefore, the liquid oxygen temperature after mixing is predicted according to the above model.

4. The method for accurately predicting and controlling the temperature of liquid oxygen filling into a cryogenic launch vehicle according to claim 3 is characterized in that: In step 2, according to the heat calculation formula, (12) is obtained From (14), we can get the relationship between the opening of the subcooled oxygen and conventional oxygen pipelines, C; When C>1, set the opening of the subcooled oxygen pipeline to KD2=80%~100%. Since the low-temperature medium flow characteristics in the pipeline are better when the regulating valve is set within this range, The opening of the conventional oxygen pipeline regulating valve is calculated based on the corresponding relationship between the regulating valve opening and the actual cross-sectional area, providing a basis for the control of the filling equipment. If C≤1, the opening of the conventional oxygen pipeline regulating valve is set to an opening KD1=80%~100% with smaller pipeline flow resistance and better low-temperature flow characteristics. If the opening is linearly related to the cross-sectional area, the opening of the subcooled oxygen pipeline regulating valve can be obtained as KD2=KD1×C×100%. In the model application, the relationship between the valve opening and the pipeline cross-sectional area depends on the actual system.

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