Single-screw compressor, thermodynamic simulation, mechanistic forces
In commercial andindustrial Heating, Ventilating, Air Conditioning & Refrigeration(HVAC&R) applications, single-screw compressors have been widely used and proven to be efficient, reliable and economical in various operating conditionsand capacity ranges. The efficiency of single-screw compressor depends on several factors, includingthe pressure ratio, volume ratio, and leakage flows as well as frictional, heat and mechanical losses. Thus, estimating forcesand momentsplay animportant role with respect to reducingmechanical losses. Itis alsocritical to the reliability and safe operation of the machine. In this paper,a detailed mechanistic model of a 6-11 configuration single-screw compressor is described. The model is used to investigate the impact of design changes on compressor performance. The governing equations of conservation of mass and energy across the multi chambers of the compressor aswell as the overall energy balanceis developed to solve the thermodynamic model to capturethe pressure and volume variation at different crank angles. The energy efficiency, mass flow rate and other compressor performance indices arealso calculated. The simulation results are validated using experimental data obtainedwith a 6-11 screw compressorwith R134a as the working fluid under several different operating conditions.The mechanistic model isachieved by implementation force and momentum balances on both the main rotor and starwheels to analyze the bearing forces,friction forces and rotor forces. The mechanistic model is integrated withthethermodynamic model and implemented in the Python programminglanguagein the opensource simulation package PDSim.