Stress Analysis of a Compressor Vane-Spring

A simple analytical model is developed for the design of a particular compressor vane-spring in this paper. The model permits the calculation of the stresses due to both static and fatigue loads, and also checks for possible material failure. In addition, a :finite element analysis, using a commercially available finite element method (FEM) computer software, was carried out to determine the spring stiffness and to provide a source for comparison with the analytical modeL FEM stresses obtained agreed reasonably well with the results obtained using the simple analytical modeL The analytical procedure presented itself for a possible optimisation of the vane-spring design. INTRODUCTION In rolling piston compressors, there exists two working chambers: the suction chamber and the compression chamber. These chambers are separated by the roller-cylinder contact and the vane tip-roller contact. The vane tip-roller contact is maintained by the vane-spring, see Figure 1. Two design criteria are important in the selection of this vane spring: the correct value of spring stiffness and the working life of the spring. The correct value of stiffness ensures good sealing at the vane tip contact and reduces leakage of gas through this contact. It also reduces possible vane chattering. The right value of spring stiffness is also important :in minimising frictional losses. The properly designed working life of the spring prevents the premature spring failure. This paper presents static and fatigue analyses for a vane-spring configuration .. The analyses however, may be extended to any vane spring design for rolling piston compressor with similar configuration. A FEM was also used to analyse the spring's behaviour and to locate the region of maximilln stresses. It is also serves as a guide for finding the spring stiffness as well as provides comparison with bending theory solution. The exercise show that the calculation procedure together with spring constant from the FEM analysis, present itself for a possible optimisation of vane-spring design. Expansion chamber Alternating motion of spring Cylinder Compression chamber Figure 1 Schematic of a vane-spring and in a rolling piston compressor STRESS ANALYSIS The section lays out the stress analysis of the vane-spring. The calculation procedure will be shown and illustrated below.