Dynamic Turbocharged Diesel Engine Simulator for Electronic Control System Development

Abstract

A nonlinear dynamic simulation of a turbocharged diesel engine is presented. The model is designed to be used as an engine simulator to aid development of advanced microelectronic control systems of varying degrees of complexity and performance. The objective is to establish the potential benefit of quite different control system concepts in advance of hardware being constructed and tested on an engine. The detail of the model is governed by the desire to accurately predict fuel economy of new engine designs currently on the drawing board, without empirical input, and respond correctly to changing ambient conditions, design alterations etc. Thus the model treats cylinders and manifolds as thermodynamic control volumes, solving energy and mass conservation equations with subroutines for combustion, heat transfer, turbocharger, dynamic aspects etc. In-cylinder calculations are performed in small engine crank-angle steps so that the correct ignition crank angle is predicted as well as the subsequent fuel burning rate. This enables parameters such as cylinder pressure and diffusion burning factor (which correlates with exhaust smoke) to be predicted. The conflict between accuracy and computer run time and cost is addressed, and it is shown how the run time of a previous model (see SAE 770123) has been reduced by an order of magnitude. The accuracy of the model is illustrated by comparing measured and predicted performance over the complete engine speed and load range under steady conditions and engine response to “full throttle” acceleration and full-load application. The model is then used to show the influence of design parameters such as injection timing and turbocharger characteristics as well as external influence such as fuel cetane number and ambient conditions on steady speed and dynamic performance.