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The present paper describes a CAE analysis approach to evaluate the design of exhaust manifold of a turbo charged gasoline engine. It allows design engineers to identify structural weakness at the early stage or to find the root cause of exhaust manifold failures. A transient none-linear finite element method is used to calculate the plastic deformation and thermal mechanical behaviors of the exhaust manifold assembly during thermal shock cycles, which include rated speed full load, rated speed motored and idle speed conditions. A transient heat transfer simulation is performed to provide thermal boundary conditions for the nonlinear stress/strain analysis. The finite element model includes a part of cylinder head, exhaust manifold, gaskets, turbo charger housing, catalytic converter, brackets, bolts and nuts. The results show that plastic deformation is the main cause of manifold cracking and the manifold flange distortion causes the exhaust leakage.

In order to predict more accurately the cracking failure of cylinder head during the durability test of turbocharged engine in the development, a comprehensive evaluation method of cylinder head durability is established. In this method, both high cycle and low cycle fatigue performance are calculated to provide failure assessment. The method is then applied to investigate the root cause of cracking of cylinder head and assess design optimizations. Multidisciplinary approach is adopted to optimize high cycle fatigue and low cycle fatigue performance simultaneously to achieve the best comprehensive performance. In this paper, the details of the method development are described. First, the high cycle and low cycle fatigue properties of cylinder head material were measured at different temperature condition, and the fatigue life and high temperature creep properties of materials under thermo-mechanical fatigue cycle were also tested.

The present paper describes a CAE analysis approach to evaluate the thermal-mechanical fatigue (TMF) of the cylinder head of a turbo charged GDI engine with integrated exhaust manifold. It allows design engineers to identify structural weakness at the early stage or to find the root cause of cylinder head TMF failures. At SAIC Motor, in test validation phase a newly developed engine must pass a strict durability test on test bed under thermal cycling conditions so that the durability characteristics can be evaluated. The accelerated dynamometer test is so designed that it gives equivalent cumulative damage as what would occur in the field. The duty cycle includes rated speed full load, rated speed motored and idle speed conditions. A transient none-linear finite element method is used to calculate the plastic deformation and thermal mechanical behaviors of the cylinder head assembly during thermal cycling.

This paper describes the application of CFD tools in the design optimization of intake ports, combustion chamber and injector of SAIC Motor's 2.0L turbo charged direct injection gasoline engine. For a more realistic simulation of spray processes, detailed investigations of mesh dependency, wall impingement models were conducted. The validation of the spray simulation was carried out by comparison between the experimental data and calculation results. To investigate the droplet-wall interactions, a comparison between the results from Bai's model and the instantaneous evaporation model was made. With the Star-CD code, the in-cylinder air motion, fuel injection and air/fuel mixing in the combustion system with central injector were evaluated, at different engine operation conditions and start of injection timings. Several proposed intake port options, with different tumble levels, were numerically investigated and compared.