Development of capacity modulation compressor based on a two stage rotary compressor – part I: Modeling and simulation of compressor performance

•A capacity modulation compressor based on a 2-stage rotary compressor is developed.•Working principle of the model and a numerical model is developed for analysis.•Cycle efficiency is numerically investigated at operating conditions.•The optimum efficiency of the CMCTR is obtained for the modulation for these modes.

Two-stage rotary compressors are gaining popularity because of their ability to reduce operating and energy costs over the entire compressor life cycle. In this work, a capacity modulation compressor based on a two-stage rotary compressor (CMCTR) is developed to improve the performance of the rotary compressor system. The working principle of the CMCTR is presented and the cycle efficiency of the compressor through two-stage compression is numerically investigated. The CMCTR model considers mass and energy balance for a control volume, the internal leakage condition for all leakage paths, the discharge valve motion, and the force and moment balance. For simulation results, the motor efficiency is estimated with respect to shaft power and the pressure during an entire cycle is obtained with respect to the compression volume for saving mode and power mode. The optimum efficiency of the CMCTR is obtained for the modulation for these modes.