The experimental characterization of the dynamics of a reciprocating freon compressor system

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Virginia Tech


This thesis discusses the experimental modal analysis work done on a reciprocating Freon compressor. The primary goal of this work was to aid in the development of a dynamic finite element model for the compressor. The crankcase, the compressor shell, and the entire compressor were each studied individually so that the characteristics of each component could be determined separately.

For each of the tested elements, a modal survey was done followed by the determination, with the use of a laser, of the forced frequency response shapes associated with each resonance. These shapes, along with the associated frequencies, were compared with the results from the finite element analysis model to determine if the model needed to be updated. The crankcase was also tested to determine if a rigid-body assumption would be valid for the purpose of force analysis.

This study resulted in the experimental data that could be used for comparison with the finite element model results. In general, the forced frequency response shapes could be matched to the finite element mode shapes up to 1400 Hz for the empty shell and assembled compressor, 2000 for the crankcase. Also, there were several conclusions that resulted from this study. These included acceptance of the rigid-body assumption for purposes of the force analysis, the need for a further look at the dynamic variations between individual compressors, and a suggestion to move the suspension mounts to the narrow side from the broad side.