A method for the spatial dynamic simulation of reciprocating compressors using the digital computer

Abstract

This thesis introduces the application of computer-aided engineering techniques to the dynamic analysis of reciprocating compressor designs. The analysis process is detailed in three steps.

The first step, an interactive pre-processor, develops the shaking forces and torques acting on the machine. The second step is a batch processed program that performs a dynamic simulation of the compressor in operation. The compressor and mounting are simulated as a rigid body with six degrees-of-freedom (X, Y, and Z translations and roll, pitch, and yaw) mounted to the ground with up to 25 arbitrarily oriented springs and dampers. Additionally, an eigenanalysis is performed that returns the natural frequencies and modes for the machine. The final step is an interactive postprocessor where the user may examine the results of the eigenanalysis as well as the operating orbit of the machine.

A series of programs that implement the analysis process was developed. The specialized formulations for the six coupled, non-linear equations of motion are presented. Color computer graphics and animation are used for visual output displays. The dynamic simulation program is designed to function on many computer systems, from low-cost personal computers to large mainframes, while the pre- and post-processing programs are designed for the personal computer.

The programs were tested by comparing the predicted results with those of an Ingersoll-Rand model 242 two piston, two stage, 3 hp compressor. The correlation between the experimental and predicted results show that the programs can accurately simulate the dynamics of a reciprocating compressor operating at steady-state. Typically, the acceleration results agree for the six degrees-of-freedom in both the time and frequency domain to within 8%.