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A combustion model for a spark-ignition engine has been developed in order to study the effect of combustion chamber geometry. The model is based on the two-zone quasi-dimensional analysis. For this model, flame front area is calculated from engine geometry and the spark location. Also, a turbulent entrainment model is used to find burning rate. The model has been calibrated and validated by the experimental data for a pentroof type engine. It has been shown that the model is successful in predicting combustion characteristics at the stoichiometric air/fuel ratio. From this model, the effects of bowl in a piston have been investigated and the optimum bowl size for the combustion is determined. Finally, the effects of the spark plug location, cylinder head type, and piston head shape on combustion process have been examined by the model.

The engine combustion is one of the most important processes affecting performance and emissions of a SI engine. As the flame propagation slows down due to EGR or lean mixture operation the fast burn system is getting more attention to improve engine performance. One effective way to achieve the fast burn is to control the motion of the charge inside a cylinder by means of optimum intake port design. Various intake ports were designed and tested in this study under several strengths of swirl levels measured by a swirl meter or LDV. Also the swirl and turbulence characteristics influenced by piston motion during intake process were analyzed by measuring cylinder gas motion under engine motoring. The mashed shroud head (MSH) out of five intake ports tested in this study was proved to be the highest swirl generating port while maintaining satisfactory volumetric efficiency.

The objective of this study is to find the effect of the dynamic pressure wave on the volumetric efficiency by analyzing the fluid flow in the intake and exhaust manifolds, and to get the optimal design criteria for the intake manifold. This study showed that five to ten percent of volumetric efficiency could be increased by the optimum design of the intake manifold without modification of the engine main body. A finite difference model was developed using two-step Lax-Wendroff method to solve the governing equations of air flow in the intake and exhaust manifolds. The results of this study are summarized as follows: 1. The optimum length of intake manifold for the maximum volumetric efficiency can exist for each specified engine speed and manifold diameter. 2.

This paper presents the experimental and analytical study on the temperature distribution and thermal deformation of the piston in diesel and gasoline engines. In order to predict temperature distribution and thermal deformation of piston, a finite element analysis has been carried out. The thermal boundary conditions around the pistion were assigned from analytical and empirical relation. The validity of the boundary conditions has been checked by the electric analogy method. Experimentally the piston temperatures for the running engine were measured by thermocouples using a mechanical linkage system and spring system. The predicted temperature distribution by a finite element method shows satisfactory agreement with the measured data. Also, for thermal deformation, steel strut and slot in piston have been analyzed by axi-symmetric 2-dimensionai finite element method using the virtual element addition method and experimental method.

Air motion in one cylinder of a Detroit Diesel 6V-92 two stroke diesel engine was studied under steady flow bench test conditions by a laser Doppler anemometer and an axisymmetric finite difference fluid dynamic model. The effects of four different exhaust opening geometries were explored. Measurements and calculations showed that the swirl induced by the 18 angled inlet ports produced non-uniform axial velocity profiles and large peaks in the mid-radius region (between cylinder center and wall). The exhaust opening geometry in the head of the cylinder influenced these axial velocity fields especially in the upper region of the cylinder. The study concluded that more uniform flow, which is favorable to the scavenging process, can be achieved by an exhaust opening located close to the cylinder periphery.