Simulation of an Intake Manifold Preheater for Cold Engine Startup

Abstract

Ensuring consistent, reliable diesel engine startups in cold temperatures is of utmost importance in a number of applications. Under extreme temperatures, the use of glow plugs is complemented by intake manifold heaters. In these, the energy released from combustion increases the intake air temperature before the air enters the main combustion chamber. Since the process also alters the stoichiometry of the fuelair mixture at the intake ports, the preheater operation must be optimized in order to guarantee successful and reliable incylinder combustion during engine startups. This paper describes the development of an intake manifold model incorporating an air preheater for application in a diesel engine. The model was created using a commercial, onedimensional simulation tool and its default heat transfer model was modified inhouse for the present application. The model was validated against experimental data and subsequently used to quantify the concentration of combustion product species at the intake runners, as well as intake charge dilution. The experimental and predicted intake runner gas temperatures agreed within 15%. Results showed that the effective equivalence ratio might increase up to 2.6 after the first 15 s of cranking, with 12.5% reduction of the O2 concentration in the intake charge.