Rarefaction and Temperature Gradient Effect on the Performance of the Knudsen Pump  

作　　者：YE Jianjun YANG Jian ZHENG Jinyang DING Xianting WONG Ieong LI Weizhong CHEN Cong 

机构地区：[1]Institute of Process Equipment, Zhejiang University, Hangzhou 310027, China [2]Engineering Research Center of High Pressure Process Equipment and SaJety oJ Mini'~try oJ l~ctucatton, Zhejiang University, Hangzhou 310027, China [3]Department of Mechanical andAerospace Engineering, University of California, Los Angeles 90095, U.S.A [4]School of Energy and Power Engineering, Dalian University of Technology, Dalian 116024, China

出　　处：《Chinese Journal of Mechanical Engineering》2012年第4期745-752,共8页中国机械工程学报（英文版）

基　　金：supported by National Hi-tech Research and Development Program of China (863 Program,Grant Nos.2009AA05Z118,2009AA044801);National Natural Science Foundation of China (Grant Nos. 50475100,51106137);China Postdoctoral Science Foundation (Grant No. 2010047172);Zhejiang Provincial Natural Science Foundation of China (Grant No. Z1100221);Fundamental Research Funds for the Central Universities of China (Grant No. 2009QNA4031)

摘　　要：The prediction of the multiscale flow in the Knudsen pump is important for understanding its pumping mechanism.However,there is little research on such interesting multiscale phenomenon in the Knudsen pumps.In this paper,a novel numerical analysis method combining the direct simulation Monte Carlo（DSMC） method with the smoothed particle hydrodynamics（SPH） method is presented for simulating the multiscale flow,which is often encountered in the application of the Knudsen pumps.Validity and accuracy of the new method are given by comparing its results with that of the previous research.Using the coupled multiscale approach,the rarefaction and the temperature drive are studied,which are two main factors on the performance of the Knudsen pumps.To investigate the effect of rarefaction on the performance of the Knudsen pump,various pump operation pressures are compared.The flow characteristics and pumping ability at different rarefaction are analyzed,and the phenomenon of the multiscale flow is also discussed.Several cases with different linear or nonlinear temperature gradients are set to investigate the effect of temperature gradient on the performance of the Knudsen pump.The flow characteristics of the Knudsen pump such as the velocity,pressure increase,and the mass flowrate are presented.A unique phenomenon,the reverse transpiration effect caused by the nonlinear temperature gradient is studied,and the reason of the significant pressure increase in the pump channel is also analyzed.Since the multiscale gas flow is widely encountered in the microflow systems,the above method and its results can also be greatly beneficial and provide significant insights for the design of the MEMS devices.The prediction of the multiscale flow in the Knudsen pump is important for understanding its pumping mechanism.However,there is little research on such interesting multiscale phenomenon in the Knudsen pumps.In this paper,a novel numerical analysis method combining the direct simulation Monte Carlo（DSMC） method with the smoothed particle hydrodynamics（SPH） method is presented for simulating the multiscale flow,which is often encountered in the application of the Knudsen pumps.Validity and accuracy of the new method are given by comparing its results with that of the previous research.Using the coupled multiscale approach,the rarefaction and the temperature drive are studied,which are two main factors on the performance of the Knudsen pumps.To investigate the effect of rarefaction on the performance of the Knudsen pump,various pump operation pressures are compared.The flow characteristics and pumping ability at different rarefaction are analyzed,and the phenomenon of the multiscale flow is also discussed.Several cases with different linear or nonlinear temperature gradients are set to investigate the effect of temperature gradient on the performance of the Knudsen pump.The flow characteristics of the Knudsen pump such as the velocity,pressure increase,and the mass flowrate are presented.A unique phenomenon,the reverse transpiration effect caused by the nonlinear temperature gradient is studied,and the reason of the significant pressure increase in the pump channel is also analyzed.Since the multiscale gas flow is widely encountered in the microflow systems,the above method and its results can also be greatly beneficial and provide significant insights for the design of the MEMS devices.

关 键 词：thermal transpiration Knudsen pump mass flowrate RAREFACTION temperature gradient-driven 

分 类 号：O781[理学—晶体学] TD43[矿业工程—矿山机电]