| The Knudsen compressor based on the the thermal transpiration effect,which is driven by the temperature gradient at wall,is mainly composed of microchannel and connecting channel.Compared with conventional compressor,it can realize the fluid medium transmission without moving parts.It has the advantages of high reliability,long service life,accurate and controllable transmission process.So it has great application prospects in micro machinery and micro flow control system.The key to design and apply the Knudsen compressor is to study the flow field characteristics and the influence laws.Based on the research of Knudsen compressor at home and abroad,combined with the structural characteristics of Knudsen compressor,this paper studies the pressure increase performance and flow field characteristics of the Knudsen compressor.The research contents include the microchannel size,compressor series parallel structure and three-dimensional flow-path condition.And this paper investigates the working characteristics and internal gas flow rules of the Knudsen compressor.The main research contents are as follows:(1)Based on the boundary conditions of velocity slip and temperature jump,the numerical model of the Knudsen compressor is established.Compared with the results of previous experiments and theoretical calculations,the validity of the numerical method used in this paper is verified.And then the pressure,velocity and temperature distribution characteristics of the flow field in Knudsen compressor channel are studied.(2)The influence of microchannel size on the flow mechanism and working characteristics of the two-dimensional Knudsen compressor is studied.At the same time,the effects of the shape,size,number and distribution of obstacles on the compressor performance are discussed.The influence of obstacles on the flow field distribution in microchannel is studied.(3)The effects of multi-stage series connection,multi-channel parallel connection and connecting channel size on the Knudsen compressor performance are studied.The influence of series connection on the distribution of gas Knudsen number,pressure,velocity and temperature in the channel is obtained.The influence of the internal reverse thermal transpiration effect in the connecting channel on the Knudsen compressor performance is investigated.And this paper analyzes the working characteristics and gas flow characteristics of multi-channel parallel Knudsen compressor.(4)A three-dimensional flow-path Knudsen compressor model is built.The pressure rise performance and flow characteristics of two-dimensional and three-dimensional flow-path Knudsen compressors are studied.The influence of different aspect ratios on the performance of the three-dimensional flow-path Knudsen compressor is analyzed.At the same time,when the hydraulic diameter of microchannel is the same,the performances of three-dimensional microchannel Knudsen compressors with different cross-section shapes are studied and compared.The results show that the circular microchannel Knudsen compressor has the best pressure increase performance. |
