Linear and nonlinear dynamics of reciprocating engines

Abstract

In the first part of this study, dynamic models of single- and multi-cylinder reciprocating machines are presented, which may involve torsional flexibility in the crankshaft. These models take into account the dependence of the engine moment of inertia on the crankshaft rotation. In addition, both the driving and the resisting moments are expressed as functions of the crankshaft motion. This leads to dynamic models with equations of motion appearing in a strongly nonlinear form. Initially, an approximate analytical solution is presented for a linearized version of the equations of motion, by applying a suitable asymptotic method. This provides valuable insight into some aspects of the system dynamics. In the second part, numerical results are presented for linear and nonlinear engine models by applying appropriate methodologies, leading to direct determination of complete branches of steady-state response. These results illustrate the effect of the system parameters on its dynamics. Finally, some results are also presented in an effort to investigate the effect of engine misfire.