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An exhaust manifold undergoing nonlinear thermal deformation was analyzed, using the Thermal Elasto-Plastic finite element model. The creep strain and the temperature-dependent apparent strain as well as nonlinear stress-strain relation are considered in the model for improving the computational accuracy. The stress-strain relation curve was formulated by means of a multi- regression analysis on the experimental data. Three dimensional solid and shell isoparametric elements were used to discretized the geometry of exhaust manifold. The boundary nodes adjacent to the interface of the cylinder head/exhaust manifold are supported by three-way springs allowing those nodes to be moved freely in the three-dimensional coordinates. A number of experiments on the exhaust manifold were also carried out to justify the validity of the finite element model.

Two computer models were used for simulation of the local flow, wall temperature, and heat transfer in combustion chambers of diesel engines. A multidimensional model linked with the conventional k-e turbulence model was employed for the calculation of in-cylinder phenomena. A finite difference procedure with an expanding/contracting grid in axisymmetric and curvilinear representation was used. Fuel injection, accommodated by an empirical formula of spray, was modeled in the form of gaseous jet. Combustion was treated using experimental data of the heat release rate. The temperature distributions of the walls were calculated by another model of thermal analysis, a finite element method, for the cylinder head, cylinder, comet chamber, and piston. Both models were coupled with boundary conditions, namely, wall functions. In DI engine, the flow and temperature fields of cylinder and piston cavity were calculated.