This paper presents a method of thermal state calculation of combustion chamber in small thrust liquid rocket engine. The goal is to predict the thermal state of chamber wall by using basic parameters of engine: thrus...This paper presents a method of thermal state calculation of combustion chamber in small thrust liquid rocket engine. The goal is to predict the thermal state of chamber wall by using basic parameters of engine: thrust level, propellants, chamber pressure, injection pattern, film cooling parameters, material of wall and their coating, etc. The difficulties in modeling the startup and shutdown processes of thrusters lie in the fact that there are the conjugated physical processes occurring at various parameters for non-design conditions. A mathematical model to predict the thermal state of the combustion chamber for different engine operation modes is developed. To simulate the startup and shutdown processes, a quasi-steady approach is applied by replacing the transient process with time-variant operating parameters of steady-state processes. The mathematical model is based on several principles and data commonly used for heat transfer modeling: geometry of flow part, gas dynamics of flow, thermodynamics of propellants and combustion spices, convective and radiation heat flows, conjugated heat transfer between hot gas and wall, and transient approach for calculation of thermal state of construction. Calculations of the thermal state of the combustion chamber in single-turn-on mode show good convergence with the experimental results. The results of pulsed modes indicate a large temperature gradient on the internal wall surface of the chamber between pulses and the thermal state of the wall strongly depends on the pulse duration and the interval.展开更多
Objective A vacuum sample chamber for SAXS measurement of solutions was developed to improve the signal-to-noise ratio of the instrument at Beijing Synchrotron Radiation Facility(BSRF).Methods We developed a vacuum sa...Objective A vacuum sample chamber for SAXS measurement of solutions was developed to improve the signal-to-noise ratio of the instrument at Beijing Synchrotron Radiation Facility(BSRF).Methods We developed a vacuum sample chamber which could be connected to the upstream and the downstream vacuum tubes by bellows.Horizontal and vertical linear slides were mounted in the vacuum chamber to adjust the sample position by 35 mm in the horizontal and vertical directions to align the sample in the light path.The liquid sample holder of the chamber was sealed with polyimide film by squeezing instead of gluing to avoid the potential influence of sealant on the solution.Results The chamber had been used for SAXS measurements of water and bovine serum albumin solution at BSRF.The results showed that the background scattering intensity in air was much higher than that in vacuum,especially in the smallangle area near the beamstop.When the q value is 0.142 nm−1,1.01 nm−1 and 1.25 nm−1,the background scattering intensity in air is 45,6.8 and 4.6 times of that in vacuum,respectively.And the background-subtracted scattering curves of bovine serum albumin solution(10 mg/ml)in air and vacuum differ in intensity by a factor of about 2.When the q value is 2 nm−1,the signal-to-noise ratios of scattering intensity of BSA in air and vacuum are 0.79 and 8.51,respectively.Conclusion We designed a simple vacuum sample chamber to be used on the SAXS instrument at 1W2A station of BSRF.The scattering of the background and protein solution in air and vacuum was tested and compared,and the signal-to-noise ratio was clearly improved.展开更多
文摘This paper presents a method of thermal state calculation of combustion chamber in small thrust liquid rocket engine. The goal is to predict the thermal state of chamber wall by using basic parameters of engine: thrust level, propellants, chamber pressure, injection pattern, film cooling parameters, material of wall and their coating, etc. The difficulties in modeling the startup and shutdown processes of thrusters lie in the fact that there are the conjugated physical processes occurring at various parameters for non-design conditions. A mathematical model to predict the thermal state of the combustion chamber for different engine operation modes is developed. To simulate the startup and shutdown processes, a quasi-steady approach is applied by replacing the transient process with time-variant operating parameters of steady-state processes. The mathematical model is based on several principles and data commonly used for heat transfer modeling: geometry of flow part, gas dynamics of flow, thermodynamics of propellants and combustion spices, convective and radiation heat flows, conjugated heat transfer between hot gas and wall, and transient approach for calculation of thermal state of construction. Calculations of the thermal state of the combustion chamber in single-turn-on mode show good convergence with the experimental results. The results of pulsed modes indicate a large temperature gradient on the internal wall surface of the chamber between pulses and the thermal state of the wall strongly depends on the pulse duration and the interval.
基金National Key R&D Program of China(Grant No.2017YFA0403000the National Natural Science Foundation of China(Grant Nos.31600597,U1532105,21576005,21878006)the Foundation of State Key Laboratory of Coal Conversion(Grant No.J19-20-604).
文摘Objective A vacuum sample chamber for SAXS measurement of solutions was developed to improve the signal-to-noise ratio of the instrument at Beijing Synchrotron Radiation Facility(BSRF).Methods We developed a vacuum sample chamber which could be connected to the upstream and the downstream vacuum tubes by bellows.Horizontal and vertical linear slides were mounted in the vacuum chamber to adjust the sample position by 35 mm in the horizontal and vertical directions to align the sample in the light path.The liquid sample holder of the chamber was sealed with polyimide film by squeezing instead of gluing to avoid the potential influence of sealant on the solution.Results The chamber had been used for SAXS measurements of water and bovine serum albumin solution at BSRF.The results showed that the background scattering intensity in air was much higher than that in vacuum,especially in the smallangle area near the beamstop.When the q value is 0.142 nm−1,1.01 nm−1 and 1.25 nm−1,the background scattering intensity in air is 45,6.8 and 4.6 times of that in vacuum,respectively.And the background-subtracted scattering curves of bovine serum albumin solution(10 mg/ml)in air and vacuum differ in intensity by a factor of about 2.When the q value is 2 nm−1,the signal-to-noise ratios of scattering intensity of BSA in air and vacuum are 0.79 and 8.51,respectively.Conclusion We designed a simple vacuum sample chamber to be used on the SAXS instrument at 1W2A station of BSRF.The scattering of the background and protein solution in air and vacuum was tested and compared,and the signal-to-noise ratio was clearly improved.
