Vane Dynamics Analysis of a Tilted Vane Rotary Compressor

An analytical model of vane dynamics in a tilted vane rotary compressor is presented. With the geometric relationship of the vane in a tilted slot, and the roller, the kinetic equations were derived for evaluating the reciprocating inertial force of the vane, and the chamber volume equations were obtained for calculating pressure history inside the compression chamber. The empirical friction coefficients were used to figure out the friction forces between the vane and slot and between the vane tip and roller. The model was compared with a dynamics program for regular rolling piston rotary compressors and displayed enough accuracy to predict vane dynamics for both regular and titled vane rotary compressors. A developed computer program was utilized to predict the effects of vane tilted angle on vane tip normal force and friction energy loss. The calculated results show that with a certain positive vane tilted angle, the vane tip normal force has the minimum value, but the vane friction loss has no significant change. INTRODUCTION Generally, in a rolling piston rotary compressor the centerline of the vane goes through the center of the cylinder bore. In this structure, when the roller pushes the vane into the vane slot, i.e. the crankangle being larger than 180 degrees, the force acted on the vane tip by the roller is not parallel to the vane movement direction, therefore forms a component force perpendicular to vane centerline. This component force increases the friction force between vane and the slot, and also causes vane deflection. In order to raise mechanical efficiency and reduce wear between vane, cylinder and roller, a rolling piston compressor with tilted vane arrangement was figured out. In this compressor, the vane centerline has an angle with the line connecting the bore center and the intersecting point of cylinder bore and vane centerline, shown in Fig. 1 a). In this way, it can be imaged that the friction force between vane and the slot and the possible vane deflection could be reduced. As a fundamental research for this compressor structure, the kinetic and dynamic characteristics, the tip load, and the friction power of the vane have been analyzed based on its new geometric relationship. This paper presents an analytical model of vane dynamics for this tilted vane rolling piston compressor. The model includes vane kinetic, dynamic, and related thermodynamic equations. A computer program was also developed to predict the effects of vane tilted angle on vane tip normal force and friction energy loss. ANALYTICAL MODELS Vane Movement The geometric relationship of a tilted vane rotary compressor is shown in Fig. 1 a). According to the coordinate system used in the figure, the equation of roller outer circle is (I) where r is roller outer radius, x0 and y0 are coordinates of roller center. The position of roller center can be expressed as x 0=esin8, y0=ecos9, where 8 is crankangle and is a function oftime, e is the eccentricity. Assume that the thickness of vane can be neglected at this moment, then the vane equation is y=R+xtan(7ll2-rJ (2) where R is cylinder bore radius, y is vane tilted angle, shown in Fig. I a). The vane tilted angle is defmed as the positive when the vane extending direction is forward the discharge port side.