Research on torsional vibration characteristics of reciprocating compressor shafting and dynamics modification

In this paper, the torsional vibration characteristics of the high-speed and high-power reciprocating compressor shafting is investigated based on the modal superposition method (MSM) and the sensitivity analysis (SA) is implemented for its dynamics modification. Firstly, the torsional vibration system model of the shafting is established by using the finite element method and modern CAD modeling technology. Then, the natural frequencies and mode shapes are solved by transforming the undamped free vibration system into standard eigenvalue problem. The harmonic excitation coefficient matrix is acquired from the periodic non-harmonic excitation by using Fourier expansion. In addition, MSM is used to solve the transient response, and the contribution of each order modal is investigated. Finally, based on SA of natural frequencies relative to structural parameters, a structural dynamics modification is proposed in terms of the actual situation. Results show that the natural frequency of torsional vibration system of the compressor shafting complies with API standard, and resonance hazard will not occur. The major modes that contribute to the torsional vibration response are first three modes, meanwhile the dynamics modification based on SA can effectively suppress the amplitude of torsional vibration.