Investigation of discharge valve in ultra-high-speed rotary compressors: An experimental and FSI simulation-based study

Abstract

The rotary compressors are currently witnessing a trend towards high-speed operation, resulting in an increased frequency of valve motion and a higher mass flow rate through the discharge valve. Consequently, high-speed operation leads to intensified impact between the valve and both the valve stopper and valve seat, thereby posing challenges to the reliability of the valve. Simultaneously, the dynamic characteristics of the valve at high operating speeds exert a significant influence on the compressor's performance. This paper develops a three-dimensional fluid-structure interaction (FSI) model to investigate the dynamic characteristics and reliability of the valve in a high-speed rotary compressor while considering heat transfer during the flow process within the cylinder. The proposed model shows better agreement with the experiment. The study revealed that as the rotational speed increases, there is an obvious rise in over-compression loss and a pronounced valve closure delay, which increases the impact velocity of the valve. The valve experiences two peaks of equivalent stress within one cycle, rendering it susceptible to fail at high speeds. The adoption of a double-valve structure at a rotational speed of 12,000 rpm leads to a significant reduction in over-compression loss by 62.9 %, an increase in volumetric efficiency by 6.7 %, a maximum decrease in impact velocity by 54.5 %, and a maximum decrease in equivalent stress by 25.6 %. The reliability of the double-valve structure under 12,000 rpm was proved by an endurance experiment. Besides, the asymmetry in the opening process of the two valves has been unveiled for the first time.