Fully Coupled Rigid Internal Combustion Engine Dynamics and Vibration—Part II: Model-Experiment Comparisons

Abstract

In internal combustion engine vibration modeling, it is typically assumed that the vibratory state of the engine does not influence the loads transmitted to the engine block from its moving internal components. This one-way-coupling assumption leads to energy conservation problems and does not account for Coriolis and gyroscopic interactions between the engine block and its rotating and reciprocating internal components. A new seven-degree-of-freedom engine vibration model has been developed that does not utilize this assumption and properly conserves energy. This paper presents time and frequency-domain comparisons of this model to experimental measurements made on an inline six-cylinder heavy-duty Diesel engine running at full load at peak-torque (1200 rpm) and rated (2100 rpm) speeds. The model successfully predicts the overall features of the engine’s vibratory output with model-experiment correlation coefficients as high as 70 percent for vibration frequencies up through third engine order. The results are robust to variations in the model parameters. Predictions are less successful at the detail level and at higher frequencies because of uncertainties in the actual imperfections of the test engine, and because of the influence of unmodeled engine components.