Sensitivity analysis of transient diesel engine simulation

Abstract

:An experimentally validated simulation code is used to study the errors induced by various, usually applied, modelling simplifications in the prediction of diesel engine operation under transient conditions after a ramp increase in load. The following simulation cases are investigated: multicylinder engine modelling, with the equations of each cylinder solved separately during each transient cycle; cylinder wall temperature modelling, with the analytical heat convection-conduction scheme compared with the usual constant wall temperature approach; in-cylinder radiation temperature correction to compensate for the underestimation of maximum temperatures from single-zone modelling; mathematical fuel pump modelling in contrast to steady state fuel injection curves; friction modelling during a transient event simulated using equations per degree crank angle as opposed to the ‘mean’ f.m.e.p. approach; and ‘deterioration’ scenarios applied to both friction and combustion rates to compensate for the peculiarities of transient operation. It is revealed that the multicylinder, analytical friction, and detailed fuel pump modelling can have an important effect on the prediction of diesel engine transient operation and thus should not be excluded from a complete transient model. The cylinder wall temperature simulation used only marginally affects the prediction of transients, whereas the friction and combustion deterioration can have quite dramatic results but need further experimental validation.