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A mean value model is presented for the transient operation of a 1.6 liter turbocharged indirect injection diesel engine. The model consists of a series of sub-models for the compressor, turbine and engine which result in a number of coupled, non-linear algebraic and differential equations. The equations are solved using a standard numerical solution package on a personal computer. The initial model calibration was performed using manufacturer supplied data and experimental data from steady state operation. Additional refinements of the model and its associated parameters were obtained through comparison with dynamic measurements on the engine. A comparison between simulated and experimental performance parameters is presented for both steady state and dynamic operation.

Mathematical models of large diesel engines traditionally include detailed models of the internal processes in the engine. Though such constructs may be very useful for detailed laboratory analysis of engine performance and may be very accurate, they require mainframe computers for their implementation, long computing times and large numbers of fitting parameters. This article shows that the results of a detailed large engine simulation program may be compressed with equations of basic engine physics to obtain a compact dynamic mean value model which can run on a microcomputer. The model is physically based and includes the main engine nonlinearities. Besides being small enough to run on-line this model uses very few fitting parameters but is nevertheless very accurate, even for large and rapid changes in the engine operating point.

The dynamic nonlinear models of engines which are studied in this paper are models of reciprocating engines which predict the time development of the time averaged mean values of the engine states rather than their instantaneous values. Such models can be made quite compact and relatively simple. Recent work indicates that they can also be made quite accurate. Thus they are attractive subjects for descriptive analysis using the theory of nonlinear differential equations and frequency analysis (of the linearized model). Such a study is carried out here for a mean value engine model of a large turbocharged two-stroke diesel engine.