Dynamic behaviors of the crankshafts in single-cylinder and twin-cylinder rotary compressors

• A numerical method is presented to analyze the dynamic behavior of crankshaft in rotary compressor.
• The vulnerable sections of crankshaft vary with the rotational speed.
• 80% of dynamic balance is an optimum solution for rotary compressor.

Refrigeration rotary compressors are widely used in air-conditioners. A rotary compressor has a special rotor-bearing system, since the elastic cantilevered crankshaft is under dynamic transverse forces on different planes. The large deformation of the crankshaft would affect the thickness of the oil film, wear the bearings down or even induce the rotor-to-stator rubs. It is considered as a non-linear fluid–structure interaction problem. To ensure the compressor operating well, the dynamic behaviors of both single-cylinder and twin-cylinder compressors' crankshafts at various speeds are analyzed. The influence of configuration of balancers on the reliability of rotor system is investigated for the further. Calculation results suggest that the vulnerable sections of crankshaft vary with the rotational speed. It is also found that 80% of the dynamic balance is the optimum design condition to reduce the transverse forces on crankshaft and the wear-out of journal bearings.