A Nonlinear, Transient, Single-Cylinder Diesel Engine Simulation for Predictions of Instantaneous Engine Speed and Torque

Abstract

A non-linear, transient, single-cylinder diesel engine simulation has been developed for predictions of instantaneous engine speed and torque. The foundation of our model is a physically based, thermodynamic, steady-state diesel engine simulation (Assanis, D. N., and Heywood, J. B., 1986, “Development and Use of a Computer Simulation of the Turbocompounded Diesel System for Engine Performance and Component Heat Transfer Studies,” SAE Paper 860329), which has been comprehensively validated for various engine designs. The transient extension of the parent model represents the diesel engine as a non-linear, dynamic system. The instantaneous crank-shaft speed is determined from the solution of the engine-external load dynamics equation, where the engine torque is tracked on a crank-angle basis. Validation of the transient model during rapid engine acceleration shows that both the cyclic fluctuations in the instantaneous crank-shaft speed line and the overall engine response are in good agreement with experimental measurements. Predictions of single-cylinder engine starting reveals the importance of selecting the proper value of the engine moment of inertia in order to control the amplitude of angular velocity fluctuations and ensure stable engine operation. It is further shown that the variation in the inertial forces on the reciprocating components with speed has a dramatic impact on the instantaneous torque profile, and consequently on angular velocity fluctuations.