Reciprocating compressors, optimization, balancing, resultant force, resultant moment
The industrial air compressor market has been growing fast, thereby compelling the manufacturers to produce competitive products with less vibration and noise, which also better meet the customers’ expectations and related regulations. Both mechanical and hydrodynamical factors induce vibrations which have substantial negative effects in the maintenance periods and the lifetime of certain components. This study focuses on the balancing of the crankshaft by modifying the geometry of the counterweights. It aims at reducing the overall vibration of a compressor with the outputs of an analytical model which investigates the dynamics of the crankshaft of a W-type reciprocating compressor. The model predicts the entire motion of the compressor. An interface is created on MATLAB to ease the use of the model. The theoretical results are validated by both a series of tests and rigid body dynamics, RBD, simulations on Ansys Workbench. The tests encompass the progressive change of the outer diameter of the counterweights on the crankshaft. The RMS (root mean square) velocities on several locations on the compressor head are obtained with a piezoelectric triaxial accelerometer for each outer diameter. The analytical model, RBD model and experimental results match each other with a maximum deviation of 5%. The conclusion of the study is that not only the optimization of the resultant forces acting on the crankshaft take a role in reducing the overall vibration on the compressor head but also the moments on the crankcase bearings alter the vibrational amplitude. The reciprocating and the centrifugal motions of the crank mechanism, the geometry of the crankshaft in axial direction and gyroscopic effect due to the crankshaft inertia tensor are considered in the calculation of the resultant moments on the bearings.