Sensitivity Analysis of Multi-Zone Modeling for Combustion and Emissions Formation in Diesel Engines 2006-01-1383

In the present work a sensitivity analysis is conducted using a multi-zone phenomenological model developed in the past by the author's, to estimate the effect of model's constants on engine performance and emissions. The constants used for this analysis are those embedded in the semi-empirical relations of the model, regarding air entrainment rate, combustion rate, ignition delay and evaporation rate. The model is applied on a heavy duty supercharged DI diesel engine and the effect of each of these constants on measurable engine parameters is defined. From the sensitivity analysis the relation between model constants and engine output data is derived. These results are used to define a constants determination procedure. The target is to define a limited number of adjustable constants so that the procedure can be of practical use. Following this, the calibration procedure is applied to determine the value of each constant, at various engine speeds and loads for the engine in question. Through this calibration procedure, the required variation of model's constants is determined and a linear correlation of the constant related to air entrainment rate is defined as a function of engine speed. Finally, a comparison is made between the theoretical and experimental values of peak combustion pressure and exhaust tailpipe emissions at all engine operating conditions examined, using the results from the calibration procedure.

Through this sensitivity analysis, a better understanding of the influence of model's constants on engine performance and emissions is obtained. Moreover, the findings from the sensitivity analysis are used to develop a calibration procedure. Calibrating model's constants at one operating condition, an accurate prediction of engine performance is obtained and the effect of engine operating conditions on pollutant emissions is predicted correctly, without any further tuning.