Design And Experimental Study On A Valved Linear Compressor For Space Application

With the development of science and technology, the cryogenics technology has been widely used in aeronautics and astronautics fields. Different refrigeration temperatures are needed for different detectors. To extend the wave length and improve the detection precision, some infrared detectors are necessary to work at4-6K temperature range. In early times, the liquid helium dewar or superfluid helium dewar was used. Recently, more and more mechanical refrigerators have been used in space detection. When compared with Stirling cryocoolers or Stirling type pulse tubes, Joule-Thomson cryocoolers have a higher efficiency and a more flexible design, thus achieve wide attention and application.The valved linear compressor is one of the crucial techniques for J-T cryocoolers. Based on clearance seal and lubricant-free technology, linear compressor has the advantages of high efficiency, long life and high reliability. When combined with reed valves, a high pressure ratio is obtained thus realizes the system circulation. When compared with moving coil type, moving magnet type linear compressor can have a higher efficiency, a larger specific electromagnetic force and a more compact structure with no flying leads. Therefore, moving magnet type linear compressor has the enormous advantages for J-T cryocoolers that working at liquid helium temperature. To valved linear compressor, some work has been carried out as following:1. The literature review of linear compressor is described from advantage, application field, linear motor, suspension, valve, loss analysis, vibration reduction, new structure and new material.2. The basic mathematical model and non-linear model of valved linear compressor are established and solved as well as a single piston valved linear compressor with a counterbalancer. The loss and efficiency of linear compressor are also analyzed. For flexure spring, the ratio of radial stiffness to axial stiffness and the ratio of maximal stress to axial stiffness are proposed to optimize the design of flexures.3. Based on above theory analysis and finite element method, a moving magnet type linear compressor is designed, including the piston, cylinder, linear motor, flexure spring, valve and so on.4. The axial stiffness of flexure spring measured from experiment is very close to the value from finite element method and the mean error is about11.6%. The linear compressor with valves is tested and a single-stage pressure ratio of3is obtained. Therefore the optimization condition of two-stage compression are decided to achieve the pressure ratio of9, that is to say, the low pressure helium of0.1MPa can be compressed to0.9MPa.