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A flow model is developed by a finite difference method to analyze the flow in the chamber type intake manifold. The model is based on one dimensional compressible unsteady flow. To obtain stable and accurate solutions, the appropriate boundary conditions for the intake chamber, intake ports and cylinder are formulated. In order to verify the simulation results for the flow model, the calculated results are compared with the experimental measurements. By analyzing pressure waves in the intake system, the optimum intake chamber volume, intake pipe length, at various engine speeds are presented. Finally, the optimum valve timings at different engine operating conditions are sought by this model.

A flow model is a convenient tool for developing the engine intake system. Two flow models for the branched engine intake were developed by the finite difference method and the method of characteristics. The results from the models were compared with the experimental data and the appropriate boundary conditions were established for each model. Modeling the flow at the intake and exhaust valves with a cylinder and at the pipe branches were the most critical part of the flow models affecting the accuracy of the solutions. From two models, it was found that the finite difference model was simpler than the characteristic model in formulation with the better accuracy. The effects of valve timings and intake geometry were studied by the flow models to design the optimum intake system.

To design an optimum engine intake system, a flow model for the intake manifold was developed by the method of characteristics. The flow in the intake manifold was one-dimensional, and finite difference equations were derived from the governing equations of flow. The thermodynamic properties inside a cylinder were found by the first law of thermodynamics, and the boundary conditions were formulated using a steady flow model. By comparing the calculated results with experimental data, the appropriate boundary conditions and convergence limits for a flow model were established. From this model, design variables for the intake system were investigated. The optimum manifold length became shorter when the engine speed were increased. The effect of intake valve timings on inlet air mass was also studied by this model. Advancing intake valve opening decreased inlet air mass slightly, and the optimum intake valve closing was found.

A new rotary type carburetor was developed for a gasoline engine. It has a rotor which feeds fuel into an engine proportionally to the inlet air flowrate. Comparing with a conventional venturi type carburetor it was simple in design with less parts. The rotary type carburetor was tested on an engine dynamometer for the various engine operating conditions. During acceleration and deceleration, the rotary type carburetor could not supply the fuel adequately, resulted in unstable engine operation. Under steady running conditions the rotary type carburetor was superior to venturi type in power and fuel economy. It was concluded from the experimental study that the rotary type carburetor is more suitable for the steady running gasoline engines especially at high speeds.

A computer model is developed to predict engine performance and exhaust emissions in a spark-ignition engine. In the model, combustion phenomenon is analyzed by the turbulent combustion model which considers the effect of the turbulence and the combustion chamber on combustion. The gas exchange process is calculated by one dimensional isentropic flow through a nozzle. During combustion, 13 products are obtained by chemical equilibrium, and nitric oxide (NO) formation is calculated by the extended Zeldovich mechanism. The results of the computer model are compared with the experimental results. The calculated values for pressure and NO emission show good agreement “with the experimental data. The effects of the engine speed, spark timing, air fuel ratio, and EGR are studied by the model.