Computer simulation of the Bristol compressor suspension system dynamics

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Virginia Tech


The objective of this research is the computer simulation of the vibrations of the suspension system of a two-cylinder reciprocating compressor. A theoretical model is developed to describe the various steps undertaken to calculate the response of this six-degree-of-freedom rigid system. The response, which is in the form of a displacement vector, serves as the input to a computer animation of the motion of the orbit of the compressor with respect to the four suspension system springs.

The theoretical model is developed by calculating (1) the System Mass and Inertial Matrix, (2) the Gyroscopic Matrix, (3) the Total Assembly Stiffness Matrix, and (4) the Shaking Forces and Moments Matrix. Experimental and finite element methods used to evaluate the parameters required to calculate these matrices are also discussed.

An eigenanalysis is performed to calculate the eigenvalue frequencies and eigenvectors for the system. The force analysis is performed to calculate the forcing function in the time domain for the first 40 harmonics. The Fast Fourier Transform method is used to transform the forcing function from the time domain to the frequency domain. The validity of the results are checked by simultaneously developing another model using IMP (Integrated Mechanisms Program). The response is then calculated in original coordinates, after performing a modal transformation.

Finally, the response, which is a displacement vector, is utilized by an animation program in PHIGS (Programmer's Hierarchical Interactive Graphics Standard) to animate the motion of the orbit of the compressor.