Effect of Geometrical Parameters on the Performance of Linear Motor for a Stirling Cooler

Abstract

Stirling coolers are becoming more popular in the area of remote sensing and space applications because of their inherent characteristics, viz., long life, high reliability, less weight, etc. In order to have a good onboard performance, the selection of the compressor drive system is crucial. The current development is to replace the conventional crank-driven compressor with a linear motor-driven compressor. Linear motors are simple devices in which axial forces are generated by current flowing in a magnetic field. This paper explores the possibility of employing various combinations of components and their materials for the design of linear drive system. The analysis includes material selection, electromagnetic design and comparison of different configurations in order to meet the stringent operating requirements of the cooler. The compactness of the Stirling cooler is influenced by the available permanent magnet dimensions, the coil winding and the shape of the outer core. Various material combinations were simulated and compared before finalizing the motor geometry. The effect of an increase in magnet height on the flux density of the air gap was studied and the magnetic saturation levels of the inner and outer core were analyzed. The influence of radial air gap on the thrust force was compared for the different configurations. The present study helps in choosing a linear motor with appropriate materials and geometry in the development of a Stirling cooler.