Fully coupled rigid internal combustion engine dynamics and vibration - Part II: Model-experiment comparisons

In internal combustion engine vibration modeling, it is typically assumed t hat the vibratory state of the engine does not influence the loads transmit ted to the engine block from its moving internal components. This one-way-c oupling assumption leads to energy conservation problems and does not accou nt for Coriolis and gyroscopic interactions between the engine block and it s rotating and reciprocating internal components. A new seven-degree-of-fre edom engine vibration model has been developed that does not utilize this a ssumption and properly conserves energy. This paper presents time and frequ ency-domain comparisons of this model to experimental measurements made on an inline six-cylinder heavy-duty Diesel engine running at full load at pea k-torque (1200 rpm) and rated (2100 rpm) speeds. The model successfully pre dicts the overall features of the engine's vibratory output with model-expe riment col-relation coefficients as high as 70 percent for vibration freque ncies up through third engine order. The results are robust to variations i n the model parameters. Predictions are less successful at the detail level and at higher frequencies because of uncertainties in the actual imperfect ions of the test engine, and because of the influence of unmodeled engine c omponents.