The Influence of Dynamic Engine Model Parameters on Crankshaft Instantaneous Angular Speed - Sensitivity and Error Analysis

Abstract

Most frequently used approach to describe combustion process in IC engines is based on Wiebe function. Its parameters are strongly influenced by geometric and in-cylinder gas- and thermodynamic processes and can’t be predicted easily and with sufficient accuracy using available empirical relations. Along with deterministic methods lacking in systematic approach, indirect analysis methods based on minimization of error between simulated and measured in-cylinder pressure have been successfully demonstrated. In this paper the same concept is introduced to identify combustion model parameters of a multi-cylinder SI engine based on box constrained Levenberg-Marquardt minimization of nonlinear Least Squares (LSQ) given for measured and simulated instantaneous crankshaft angular speed determined from the solution of the engine dynamics torque balance equation. For predictions of gas pressure and engine torque, a nonlinear, detailed, angle resolved twozone, zero-dimensional multi-cylinder SI engine combustion model has been developed as well as a detailed analytical component model of engine friction and mechanical losses. The models are used to analyse the influences of engine combustion and dynamics model parameters on instantaneous crankshaft speed and to investigate biases in measurement in order to recognize and establish the constraints in process of combustion model parameters identification.