State Key Laboratory of Technologies in Space Cryogenic Propellants

Beijing, China

State Key Laboratory of Technologies in Space Cryogenic Propellants

Beijing, China
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Liu Z.,Xi'an Jiaotong University | Li Y.,Xi'an Jiaotong University | Li Y.,State Key Laboratory of Technologies in Space Cryogenic Propellants
Refrigeration Science and Technology | Year: 2015

The self-pressurization process of cryogenic liquid hydrogen tank considering the phase change, liquid thermal stratum and surface tension is investigated with a computational fluid dynamic (CFD) model. Validated by the experiment data obtained from the flight test, the improved CFD model is selected to research the influences of reduced gravity on tank pressurization process. In order to recognize the tank pressurization and thermal stratification performance clearly, four gravity levels (1g0, 10-1g0, 10-2g0 and 10-3g0) are considered and compared with each other. The results indicate that the gravity level has a great effect on pressure increasing process. Some valuable conclusions are listed as: (1) Comparing with the pressure difference of 1g0, the pressure differences in reduced gravity varying from 10-1g0 to 10-3g0 are increased by 10.7%, 16.7% and 27.6%, respectively. Opposite to the change tendency of pressure differences, evaporation losses are 1.593kg, 0.637kg, 0.332kg and 0.232kg with the gravity level ranging from 1g0 to 10-3g0. In addition, the phase change form at the beginning of the pressurization process is condensation, with the time continuing, evaporation would become the leading phase change form. Heat leakage through tank wall plays a leading role in tank pressure rising, the effects of evaporation quality are not appeared in short time. (2) With the increasing of gravity levels, the temperature distributions in the ullage region become more uniform, and the liquid stratum layers develop faster. Calculated with CFD model and compared with two theoretical models, it turns out that the relative errors of stratum thickness between CFD model and Tellep model are always smaller than that of stratum thickness between CFD model and Reynolds model. However, it is opposite for the comparison of stratum temperature. (3) Different direction stream cycles are forming in the upper part of the ullage. Many large and small vortex or loops are developing between two slosh baffles. The streamline distribution in the liquid stratum like a plume and forms circulate loop between the tank wall and axis. (4) Influenced by surface tension, liquid close to the tank wall moves up along the wall in reduced gravity. The interface in the gravity level of 10-1g0 is still flat as same as that of 1g0, while others are becoming curved with the interface area increasing.

Li Y.,Zhejiang University | Wu S.,Zhejiang University | Jin T.,Zhejiang University | Lei G.,State Key Laboratory of Technologies in Space Cryogenic Propellants
Experimental Thermal and Fluid Science | Year: 2017

Slush nitrogen, a cryogenic fluid with solid particles suspended in liquid, is considered a potential coolant for high temperature superconductors. In this study, the capacitance-type meters, which are adopted for measuring the density, liquid level and flow velocity of slush nitrogen, are improved with their accuracy and reliability by optimizing the measurement components and mechanical structure. For density measurement, a capacitance-to-digital converter with high accuracy and resolution is used. The liquid level meter is equipped with a coaxial shielding tube, which is earth grounded to protect the electrodes from mechanical disturbance and electromagnetic interference, to strengthen the mechanical support and to improve the stability. The capacitors with double-circular curved-plate electrodes are adopted in the flowmeter to improve its sensitivity. According to the calibration results, the densimeter and the liquid level meter have high sensitivity and good linearity, with the improved accuracy of ±0.16% and ±1.0%, respectively. Besides, the flow velocity can be calculated from the capacitors’ mounting spacing and the delay time of density fluctuation analyzed by cross-correlation function, which turns out to have a relative error within ±7.5% compared with that calculated by the measured variation of liquid level. © 2017 Elsevier Inc.

He K.,University of Science and Technology Beijing | Zhu H.,Hanbao Steel Energy Center | Wang L.,University of Science and Technology Beijing | Wang L.,State Key Laboratory of Technologies in Space Cryogenic Propellants
Applied Energy | Year: 2015

Inspired by energy storage systems for peak load shifting (PLS), this study proposes a PLS utilization mode of electricity-generating coal gas resources for the steel industry in China. The proposed mode can help the steel industry save electricity bills (2.4%) through the introduction of a time-of-use tariff. Data of a steel enterprise are used to prove the economic benefit of the coal gas utilization mode. Given that China produces more than half of converter steel of the total production worldwide, their coal gas resources are abundant. The PLS utilization mode will have a great effect on balancing the power grid. A simulated operation model for PLS coal-fired power units is used to calculate the energy conservation and emission reduction effect of coal-fired power plants under different scenarios. The annual coal savings are 1.7-3.1%, and the annual SO2 and NOX emission reductions are 2.9-12.4% and 44.6-14.1% of the total reduction amount of the steel industry in China, respectively. © 2015 Elsevier Ltd.

Wang B.,Shanghai JiaoTong University | Huang Y.,Shanghai JiaoTong University | Wu J.,Shanghai JiaoTong University | Wang T.,State Key Laboratory of Technologies in Space Cryogenic Propellants | Lei G.,State Key Laboratory of Technologies in Space Cryogenic Propellants
Applied Thermal Engineering | Year: 2017

Long-term storage of cryogenic propellants on orbit as the replenishing fuel for spacecraft and energy supply source for space station is a crucial part of future space exploration. Thermodynamic vent system (TVS) was proposed as an effective technology to maintain the propellant tank pressure and reduce the mass loss of liquid propellant. This study presents an experimental investigation on the pressure control effect of a TVS installed in a 1.36 m3 liquid nitrogen (LN2) tank of the testing facility named Efficient Cryogenic Fluid Storage Test Platform (ECFSTP). Two operation modes, namely the mixing-only mode and the mixing-venting mode of TVS were compared and analyzed. The degree of superheat of the ullage dropped more rapidly and significantly under the mixing-venting mode, which produces the cooling effect by the venting stream from the throttling valve in addition to venting itself. The effects of different pressure control bands on the performance of the TVS have also been comparatively investigated. The results confirmed the feasibility and effectiveness of the TVS to control the tank pressure within the range of 220–260 kPa for long time running, with 50% fill level and 9.31 W m−2 leaking heat flux. © 2017 Elsevier Ltd

Chang H.,State Key Laboratory of Technologies in Space Cryogenic Propellants | Chang H.,Huazhong University of Science and Technology | Xie X.,Huazhong University of Science and Technology | Zheng Y.,Huazhong University of Science and Technology | Shu S.,Huazhong University of Science and Technology
International Journal of Hydrogen Energy | Year: 2017

Cavitation is usually caused by the pressure difference between the static pressure and the saturated vapor pressure under the local temperature and may result in huge damage to the pipelines. This paper developed a simplified cavitation model based on Rayleigh-Plesset bubble equation and Zwart cavitation model, and conducted a series of numerical simulations with the process of phase change and latent heat added to the solver by UDFs (User Defined Functions). The aim of the paper is to study the affecting factors on the cavitation process of liquid hydrogen in elbow pipes. The results show that the thermal effect can suppress the occurrence and development of cavitation. As the process of cavitation goes on, the suppression of thermal effect is more remarkable. Before the cavitating flow reaches its steady state, cavitation process is very sensitive to the changes of inlet velocity and outlet pressure. Increasing the inlet velocity or decreasing the outlet pressure can both strengthen the cavitation process. The turbulent viscosity ratio has little effects on cavitation process of liquid hydrogen, but the increase of turbulent viscosity ratio can enhance the thermal effect and lower the temperature gradient in the cavity. In addition, the structure of the cavity is found to be related to the bend angles. The cavitation process is enhanced with the decrease of the angles since the duration of centrifugal force is longer. © 2017 Hydrogen Energy Publications LLC.

Liu Z.,Xi'an Jiaotong University | Li Y.,Xi'an Jiaotong University | Li Y.,State Key Laboratory of Technologies in Space Cryogenic Propellants | Jin Y.,Xi'an Jiaotong University
Applied Thermal Engineering | Year: 2016

One CFD model is established to investigate the pressurization performance and thermal stratification in the final stage cryogenic liquid oxygen (LOX) tank, which is subjected to aerodynamic heat and space radiations during launch. Iterative calculation with variable physical properties in each time step, both aerodynamic heat and space radiation have been considered by compiling one UDF and implanting it into the CFD model. It turns out that aerodynamic heat has caused large influence on tank pressurization performance, while the effect of space radiation on tank pressurization is not obviously reflected. Influenced by the injection gas, tank pressure fluctuates between the minimum and the maximum pressure limit and the ullage mass decreases due to condensation during the active-pressurization. Meanwhile, the basic parallel advance trend of temperature distribution is roughly formed. During the pressurized discharge, tank pressure experiences a sharp decline at first, then decreases linearly, finally reduces with a larger rate. The liquid temperature increases gradually to the direction of advance as liquid height declines. Moreover, the residual liquid temperature increases obviously. With the heat continuous transferring from the ullage to the liquid, the ullage is under condensation during the whole process. © 2016 Elsevier Ltd

Liu Z.,Xi'an Jiaotong University | Li Y.,Xi'an Jiaotong University | Li Y.,State Key Laboratory of Technologies in Space Cryogenic Propellants | Zhou K.,Xi'an Jiaotong University
Energy Conversion and Management | Year: 2016

Full use and effective management of cold capacity are significant for improving the performance of heat exchanger in the thermodynamic vent system (TVS). To understand the operation principle of TVS easily, the thermodynamic analysis, based on the ideal gas state equation and energy conservation equation, is detailed introduced. Some key operation parameters are optimized and suggested. As the low mass flow rate and low heat fluxes are involved in flow boiling of the annular pipe fluid, the Kandlikar's boiling heat transfer correlation is selected to predict the flow boiling process, after validated with the related experimental results. One quasi-steady state model is established to investigate the heat transfer performance of double-pipe heat exchanger in normal gravity, with the bulk fluid natural convection, annular pipe two-phase boiling and inner pipe forced convection coupled from outside to inside. Determined by the local pressure and temperature, the fluid thermophysical properties are variable with the pipe length and time. With the variable fluid thermophysical properties, both the static analysis and the transient thermal performance of TVS heat exchanger are investigated respectively. Meanwhile, effects of the external natural convection and the pipe sizes on the thermal and flow performance of heat exchanger are detailed researched and analyzed. Some valuable conclusions are obtained and significant to optimize the TVS heat exchanger design. © 2016 Elsevier Ltd

Wang L.,Xi'an Jiaotong University | Li Y.,Xi'an Jiaotong University | Li Y.,State Key Laboratory of Technologies in Space Cryogenic Propellants | Li C.,Xi'an Jiaotong University | Zhao Z.,Xi'an Jiaotong University
Cryogenics | Year: 2013

Predictions of thermal and pressurization performance in a liquid hydrogen (LH2) tank during liquid discharge is of significance to the design and optimization of a rocket pressurization system. In this paper, a computational fluid dynamic (CFD) model is introduced to simulate the pressurized discharge event of LH2 tank. The wall region together with the fluid region is simultaneously considered as the computational domain, and low-Re k-ε model is applied to account for the fluid-wall heat exchange effect. Liquid-vapor phase change effect is also involved in the model. Comparison of the numerical results with existing experimental data suggests that the CFD model has a good adaptability in pressurization computation. Detailed characteristics, such as pressurant gas requirement, pressure altering history, and temperature distribution inside the tank, can be obtained by the model. The difference of pressurant gas, selecting helium or vapor H 2, may result in the variations in pressure and temperature histories. Pressurization by vapor H2 supplies a higher pressure and also a temperature rise, which is significant to consider the selection of pressurant gas. The influences of phase change effect and injector structure on pressurization behaviors are also analyzed. The computational results show that liquid-vapor phase change has a slight influence on the pressurization behaviors. Significant pressure decay at the beginning stage of process may occur in the case of no-diffuser injector application since the incoming gas is excessively cooled by cold LH2. The results show that the present CFD model has a good adaptability in the prediction of pressurization behaviors and is a useful tool for the design and optimization of a pressurization system. © 2013 Published by Elsevier Ltd. All rights reserved.

Wang L.,Xi'an Jiaotong University | Li Y.,Xi'an Jiaotong University | Li Y.,State Key Laboratory of Technologies in Space Cryogenic Propellants | Zhao Z.,Xi'an Jiaotong University | Liu Z.,Xi'an Jiaotong University
International Journal of Heat and Mass Transfer | Year: 2013

A computational fluid dynamic (CFD) model, which can simultaneously account for the heat exchanges inside the tank and outside aerodynamic heating, is constructed to investigate the transient thermal and pressurization performance of cryogenic tank during discharge. Besides the fluid and tank wall regions, the foam region is also considered as the computational domain. Reference enthalpy method is used to account for the outside aerodynamic heating effect. The predictive ability of the CFD model is evaluated on the basis of the comparisons between its results and experimental data and a good agreement is obtained. Then the model is used to predict a pressurized discharge event, and the thermal and pressurization behaviors are obtained and analyzed. The results show that outside aerodynamic heating cannot penetrate the foam layer to facilitate the pressurization performance. Conversely, a certain proportion of energy might be transferred from heated tank wall to foam layer, which exert a negative effect on the pressurization behaviors. The aerodynamic heating effect may not be accounted for in the CFD simulation of a foam-insulated tank, if the thermal performance at outer surface of the tank is not particularly concerned. Generally, this paper supplies an effective way to predict pressurization performance and expresses valid results of the thermal performance inside and outside the cryogenic tank during discharge. It is also stated that the CFD model has a better accuracy in predicting pressurization characteristics.

Zheng J.,Xi'an Jiaotong University | Li Y.,Xi'an Jiaotong University | Li Y.,State Key Laboratory of Technologies in Space Cryogenic Propellants | Wang L.,Xi'an Jiaotong University | Tan H.,Xi'an Jiaotong University
Cryogenics | Year: 2014

Contact heat transfer across mechanically pressed solid/solid contacts with or without interstitial bonding material is an important phenomenon in cryogenic engineering. This paper introduces an improved thermal contact resistance (TCR) model. The model, which considers both plastic and elastic deformation, matches well with the experimental data for pressed stainless steel 304 contacts in the range 110-150 K and 1-7 MPa. A method is also suggested to evaluate the microscopic effects of the TCR for alloyed metals in the range between liquid nitrogen temperature and room temperature. Based on the improved TCR model and the analysis of the heat transfer across the bonded joints, the thermal joint resistance (TJR) is modeled as the sum of the TCR and the bonding material resistance. The solid/liquid contact resistance is obtained by assuming the ideal gas law holds for the trapped air in the micro gaps. The TJR model indicates that the TJR depends on the bonding area, the bond line thickness, thermal conductivity of the bonding material, the initially applied pressure, the surface roughness, and thermal resistance of the bare contacts. The TJR model predictions are in good agreement with experimental data for joints incorporating bonding materials or thermal greases. © 2013 Elsevier Ltd. All rights reserved.

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