Dynamic analyses for the rotor-journal bearing system of a variable speed rotary compressor

• Natural frequencies and vibration modes of the system have been obtained.
• The time-varying stresses of the system have been calculated.
• Deformation and oil film thickness of the journal bearings have been simulated.
• Axis orbits of the journal bearings and the motor rotor have been obtained.
• Influences of oil holes on the crankshaft stress have been analyzed.

In the rotary compressor, the rolling piston and the contacted rotor-journal bearing system are main moving components. They suffer very large periodically varying loads introduced by the inertia force, the contact force and the gas force. These loads change rapidly with speed variation of the compressor. They always lead to serious vibration of the system, and then result in abrasion and performance reduction. In this paper, the dynamic behavior of the rotor-journal bearing system were calculated by solving three-dimensional numerical model using finite element method, and the vibration characteristics of the system were investigated according to the calculation results. The natural frequencies and vibration modes were obtained. The stress, displacement and axis orbit of the rotor center were calculated considering the speed variation of the motor. Via the established numerical model, vibration characteristics of a newly designed compressor can be predicted, and optimization can be done to reduce the vibration.