Vibration reduction of a single cylinder reciprocating compressor based on multi-stage balancing

Basically, a reciprocating compressor consists of three main mechanical subsets: the hermetic housing, the crankcase and the rotor-crankshaft assembly. The counterweight mass located on the rotor-crankshaft is designed to balance the eccentric masses of the slider-crank mechanism which predominate in comparison to the residual distributed unbalance masses due to manufacturing. However, excessive vibration levels can be observed. The objective of the study is to perform a reliable finite element model for balancing the compressor by taking into account the dynamic behavior of the three subsets. The rotor-crankshaft assembly is considered as a flexible body, while the crankcase and the housing are assumed to be rigid. The rotor-crankshaft model is updated by using experimental modal analysis at rest. The characteristics of the fluid film bearings are speed of rotation dependant. The forces of the pressure and of the slider-crank mechanism are expanded by using Fourier transformation. The Influence Coefficient Method is used to investigate several balancing solutions to reduce the vibratory levels of the target plane located on the three main subsets. The experiments carried out show that this multi-stage balancing procedure is rather more efficient than a classical approach based only on the dynamic balancing of the rotor crankshaft assembly.