To meet the demand for miniaturized,compact,high-reliability,and long-life cryocoolers in small satellite platforms,the development of a linear Stirling cryocooler has been undertaken.Computational Fluid Dynamics(CFD)...To meet the demand for miniaturized,compact,high-reliability,and long-life cryocoolers in small satellite platforms,the development of a linear Stirling cryocooler has been undertaken.Computational Fluid Dynamics(CFD)numerical simulation software was used to conduct simulation analyses,verifying the impact of porous media channel layout,eccentricity,viscous resistance coefficient of the porous media,and piston position on the designed aerostatic bearing piston employing self-supplied gas bearing technology.The calculation results indicate that both the aerostatic force and leakage increase synchronously with eccentricity,while the two designed gas lift channel layouts are capable of providing sufficient load-bearing capacity while ensuring minimal leakage.Through calculations,it was determined that the viscous resistance coefficient of the porous media material,used as a throttling mechanism,is most suitable within the range of 81011 to 810131/m2.When studying the piston position,it was found that××due to the influence of the gas film length,the aerostatic force gradually increases as the piston moves from the maximum compression stroke state to the maximum low-pressure stroke state.To validate combining simulation with experimental platform testing,a support fixture platform for testing the load-bearing capacity of the gas bearings was independently constructed.The development of the aerostatic bearing piston prototype was completed,and performance tests were conducted,confirming that the trend of aerostatic force variation with gas film length is consistent with calculations.Additionally,it was verified that under the two aerostatic channel layouts,the aerostatic force closely matches the calculated values.展开更多
The acoustic field of a linear compressor serves to deliver the compression work to the load, such as the connected cold head of a cryocooler; it plays an equivalently important role as the electrical and mechanical p...The acoustic field of a linear compressor serves to deliver the compression work to the load, such as the connected cold head of a cryocooler; it plays an equivalently important role as the electrical and mechanical parts, especially in the impedance match issue. This paper studies the acoustic impedance characteristics of a linear compressor. The parameters including the current, the piston displacement, the pressure amplitude, the electrical power dissipation, the power factor, the pressure-volumetric (PV) power delivered, and the efficiency are theoretically and experimentally investigated. Different from previous theoretical studies, optimization for the operations away from the resonance is also included. More general optimization results imply relevance between thermoacoustic engines and linear compressors. The predicted results are validated by the experiments performed on a linear compressor with an adjustable resistive-capacitive (RC) acoustic load. The comparisons between the calculations and the measurements are presented and analyzed. The results provide deeper insight into the mechanism of the linear compressor and the impedance match in a cryocooler system.展开更多
Large-eddy simulation（LES） is compared with experiment and Reynolds-averaged Navier-Stokes（RANS）, and LES is shown to be superior to RANS in reproducing corner separation in the LMFA-NACA65 linear compressor casca...Large-eddy simulation（LES） is compared with experiment and Reynolds-averaged Navier-Stokes（RANS）, and LES is shown to be superior to RANS in reproducing corner separation in the LMFA-NACA65 linear compressor cascade, in terms of surface limiting streamlines,blade pressure coefficient, total pressure losses and blade suction side boundary layer profiles. However, LES is too expensive to conduct an influencing parameter study of the corner separation.RANS approach, despite over-predicting the corner separation, gives reasonable descriptions of the corner separated flow, and is thus selected to conduct a parametric study in this paper. Two kinds of influencing parameters on corner separation, numerical and physical parameters, are analyzed and discussed： second order spatial scheme is necessary for a RANS simulation; incidence angle and inflow boundary layer thickness are found to show the most significant influences on the corner separation among the parameters studied; unsteady RANS with the imposed inflow unsteadiness（inflow angle varying sinusoidally with fluctuating amplitude of 0.92°） does not show any non-linear effect on the corner separation.展开更多
A valveless linear compressor was built up to drive a self-made two-stage pulse tube cryocooler. With a designed maximum swept volume of 60 cm3, the compressor can provide the cryocooler with a pressure volume (PV) po...A valveless linear compressor was built up to drive a self-made two-stage pulse tube cryocooler. With a designed maximum swept volume of 60 cm3, the compressor can provide the cryocooler with a pressure volume (PV) power of 400 W. Preliminary measurements of the compressor indicated that both an efficiency of 35%～55% and a pressure ratio of 1.3～1.4 could be obtained. The two-stage pulse tube cryocooler driven by this compressor achieved the lowest temperature of 14.2 K.展开更多
To optimize the efficiency of the linear compressor,its operating frequency must be controlled equal to the system resonant frequency.The traditional resonant frequency tracking control algorithm relies on the steady ...To optimize the efficiency of the linear compressor,its operating frequency must be controlled equal to the system resonant frequency.The traditional resonant frequency tracking control algorithm relies on the steady state characteristics of the system,which suffers from slow convergence speed,low accuracy and slow system response.In order to solve these problems,a novel resonant frequency tracking control for linear compressor based on model reference adaptive system(MRAS)is proposed in this paper,and the parameter adaptive rate is derived by the Popov's hyperstability theory,so that the system resonant frequency can be directly calculated through the parameter adaptive rate.Furthermore,the traditional algorithm needs to calculate the piston stroke signal by integrating the back-EMF,which has the problem of integral drift.The algorithm proposed in this paper only needs the velocity signal,and the accuracy of the velocity calculation can be ensured by utilizing the self-adaptive band-pass filter(SABPF),thereby greatly improving the accuracy of the resonance frequency calculation.Simulation results verify the effectiveness of the proposed algorithm.展开更多
This work investigates the start-up characteristics of linear compressors in a refrigeration system through experiment and simulation.Experiments are carried out by a refrigeration test system with a linear compressor...This work investigates the start-up characteristics of linear compressors in a refrigeration system through experiment and simulation.Experiments are carried out by a refrigeration test system with a linear compressor controlled by a LabVIEW platform.A simulation model that considers the nonlinear process of gas force is set up on the basis of Runge-Kutta method for linear compressors.Compared with the experimental results,the simulation errors are within 15%,including the unstable state.The influences of ambient temperature and power frequency on linear compressors are studied through experiments.Unstable phenomena exist at 25℃ ambient temperature compared with the designed ambient temperature of 35℃.The unsteadiness mechanism is analyzed by simulation.Simulation analysis indicated that two sensitive stages of linear compressors,namely,starting to pump and touching top dead center,are unstable.Furthermore,properly increasing equivalent mass (approximately 3%) or spring stiffness doring the design stage can be a practical method to improve the stability of linear compressors.展开更多
The inertance tube is one of the key components of a pulse tube cryocooler. It has great influence not only on the efficiency of the pulse tube cryocooler, but also on the efficiency of the linear compressor. Meanwhil...The inertance tube is one of the key components of a pulse tube cryocooler. It has great influence not only on the efficiency of the pulse tube cryocooler, but also on the efficiency of the linear compressor. Meanwhile, it is very difficult to predict the impedance of an inertance tube because of the turbulent flow. In this paper, using a quasi-turbulent model, the inertance tube is optimized to match a linear compressor driven pulse tube cryocooler. Experimental results show that this model can predict the impedance quite well. With 127 W input electric power, the pulse tube cryocooler obtains 9.4 W cooling power at a temperature of 77 K. The relative Carnot efficiency of the whole system reaches 19.8%.展开更多
文摘To meet the demand for miniaturized,compact,high-reliability,and long-life cryocoolers in small satellite platforms,the development of a linear Stirling cryocooler has been undertaken.Computational Fluid Dynamics(CFD)numerical simulation software was used to conduct simulation analyses,verifying the impact of porous media channel layout,eccentricity,viscous resistance coefficient of the porous media,and piston position on the designed aerostatic bearing piston employing self-supplied gas bearing technology.The calculation results indicate that both the aerostatic force and leakage increase synchronously with eccentricity,while the two designed gas lift channel layouts are capable of providing sufficient load-bearing capacity while ensuring minimal leakage.Through calculations,it was determined that the viscous resistance coefficient of the porous media material,used as a throttling mechanism,is most suitable within the range of 81011 to 810131/m2.When studying the piston position,it was found that××due to the influence of the gas film length,the aerostatic force gradually increases as the piston moves from the maximum compression stroke state to the maximum low-pressure stroke state.To validate combining simulation with experimental platform testing,a support fixture platform for testing the load-bearing capacity of the gas bearings was independently constructed.The development of the aerostatic bearing piston prototype was completed,and performance tests were conducted,confirming that the trend of aerostatic force variation with gas film length is consistent with calculations.Additionally,it was verified that under the two aerostatic channel layouts,the aerostatic force closely matches the calculated values.
基金supported by the National Natural Science Foundation of China (No. 51176165)the Open Project Program of the Key Laboratory of Infrared Imaging Materials and Detectors (No. IIMDKFJJ-11-07), China
文摘The acoustic field of a linear compressor serves to deliver the compression work to the load, such as the connected cold head of a cryocooler; it plays an equivalently important role as the electrical and mechanical parts, especially in the impedance match issue. This paper studies the acoustic impedance characteristics of a linear compressor. The parameters including the current, the piston displacement, the pressure amplitude, the electrical power dissipation, the power factor, the pressure-volumetric (PV) power delivered, and the efficiency are theoretically and experimentally investigated. Different from previous theoretical studies, optimization for the operations away from the resonance is also included. More general optimization results imply relevance between thermoacoustic engines and linear compressors. The predicted results are validated by the experiments performed on a linear compressor with an adjustable resistive-capacitive (RC) acoustic load. The comparisons between the calculations and the measurements are presented and analyzed. The results provide deeper insight into the mechanism of the linear compressor and the impedance match in a cryocooler system.
基金funded by the Sino-French project AXIOOM (funding: NSFC and ANR)the supports from NSFC (Nos. 51420105008, 51376001, 51506121 and 51676007)performed using HPC resources from GENCICINES (No.2014-2a6081)
文摘Large-eddy simulation（LES） is compared with experiment and Reynolds-averaged Navier-Stokes（RANS）, and LES is shown to be superior to RANS in reproducing corner separation in the LMFA-NACA65 linear compressor cascade, in terms of surface limiting streamlines,blade pressure coefficient, total pressure losses and blade suction side boundary layer profiles. However, LES is too expensive to conduct an influencing parameter study of the corner separation.RANS approach, despite over-predicting the corner separation, gives reasonable descriptions of the corner separated flow, and is thus selected to conduct a parametric study in this paper. Two kinds of influencing parameters on corner separation, numerical and physical parameters, are analyzed and discussed： second order spatial scheme is necessary for a RANS simulation; incidence angle and inflow boundary layer thickness are found to show the most significant influences on the corner separation among the parameters studied; unsteady RANS with the imposed inflow unsteadiness（inflow angle varying sinusoidally with fluctuating amplitude of 0.92°） does not show any non-linear effect on the corner separation.
文摘A valveless linear compressor was built up to drive a self-made two-stage pulse tube cryocooler. With a designed maximum swept volume of 60 cm3, the compressor can provide the cryocooler with a pressure volume (PV) power of 400 W. Preliminary measurements of the compressor indicated that both an efficiency of 35%～55% and a pressure ratio of 1.3～1.4 could be obtained. The two-stage pulse tube cryocooler driven by this compressor achieved the lowest temperature of 14.2 K.
基金supported in part by the National Natural Science Foundation of China under Grants 51877093 and 51707079in part by the National Key Research and Development Program of China under Grant 2018YFE0100200in part by the Key Technical Innovation Program of Hubei Province under Grant 2019AAA026.
文摘To optimize the efficiency of the linear compressor,its operating frequency must be controlled equal to the system resonant frequency.The traditional resonant frequency tracking control algorithm relies on the steady state characteristics of the system,which suffers from slow convergence speed,low accuracy and slow system response.In order to solve these problems,a novel resonant frequency tracking control for linear compressor based on model reference adaptive system(MRAS)is proposed in this paper,and the parameter adaptive rate is derived by the Popov's hyperstability theory,so that the system resonant frequency can be directly calculated through the parameter adaptive rate.Furthermore,the traditional algorithm needs to calculate the piston stroke signal by integrating the back-EMF,which has the problem of integral drift.The algorithm proposed in this paper only needs the velocity signal,and the accuracy of the velocity calculation can be ensured by utilizing the self-adaptive band-pass filter(SABPF),thereby greatly improving the accuracy of the resonance frequency calculation.Simulation results verify the effectiveness of the proposed algorithm.
基金We would like to thank the support from the National Natural Science Foundation of China(No.51576203 and No.51976229)this study is also supported by CAS Key Laboratory of Cryogenics,TIPC(No.CRYOQN201908)Dr.Tang M.S.is supported by Youth Innovation Promotion Association,CAS(No.2018032).
文摘This work investigates the start-up characteristics of linear compressors in a refrigeration system through experiment and simulation.Experiments are carried out by a refrigeration test system with a linear compressor controlled by a LabVIEW platform.A simulation model that considers the nonlinear process of gas force is set up on the basis of Runge-Kutta method for linear compressors.Compared with the experimental results,the simulation errors are within 15%,including the unstable state.The influences of ambient temperature and power frequency on linear compressors are studied through experiments.Unstable phenomena exist at 25℃ ambient temperature compared with the designed ambient temperature of 35℃.The unsteadiness mechanism is analyzed by simulation.Simulation analysis indicated that two sensitive stages of linear compressors,namely,starting to pump and touching top dead center,are unstable.Furthermore,properly increasing equivalent mass (approximately 3%) or spring stiffness doring the design stage can be a practical method to improve the stability of linear compressors.
基金Supported by the National Natural Science Foundation of China (Grant No. 10874190)National Science Foundation of China for Distinguished Young Scholars (Grant No. 50625620)
文摘The inertance tube is one of the key components of a pulse tube cryocooler. It has great influence not only on the efficiency of the pulse tube cryocooler, but also on the efficiency of the linear compressor. Meanwhile, it is very difficult to predict the impedance of an inertance tube because of the turbulent flow. In this paper, using a quasi-turbulent model, the inertance tube is optimized to match a linear compressor driven pulse tube cryocooler. Experimental results show that this model can predict the impedance quite well. With 127 W input electric power, the pulse tube cryocooler obtains 9.4 W cooling power at a temperature of 77 K. The relative Carnot efficiency of the whole system reaches 19.8%.
