Study On Heat Transfer Process In Cylinder Of Diesel Engine (Development Of KIVA-3 Program)

Diesel engine is a kind of thermal machine with high thermal efficiency and wide application in the world.The excellent working performance of the diesel engine makes it the preferred power source.With the world's energy shortage and environmental pollution problems becoming more and more prominent,studying the in-cylinder heat transfer process to obtain improved diesel engine operating indicators has become one of the exploration themes of internal combustion engine researchers around the world.The paper uses the 1105diesel engine as the calculation model to carry out numerical research on the in-cylinder heat transfer process between the intake valve closing and the exhaust valve opening on the calculation platform of the KIVA-3 program.The research results can be summarized as follows.The average heat transfer coefficient of the entire combustion chamber wall during the working process of the diesel engine increases first and then decreases with the crankshaft rotation.The average heat transfer coefficient of the combustion chamber wall at the simulation starting point is 76.23W/m~2·K,and increases to the maximum value of 3692.18W/m~2·K at 10°CA after the top dead center,and is reduced to the end of the exhaust valve opening simulation.105.80W/m~2·K.The wall surface heat transfer coefficient increases from the closing of the intake valve to the injection start point,and the heat transfer coefficient increases rapidly after the fuel injection starts and reaches a peak after the maximum pressure point.In the range of the smaller crank angle after the top dead center,the heat transfer coefficient of the wall surface tends to be flat after the exhaust valve is opened.The local heat transfer coefficient of the combustion chamber wall during the working process of the diesel engine is:(1)The heat transfer coefficient of the top surface of the piston decreases in the radial direction from the opening edge of the W-shaped pit at the top of the piston.The heat transfer coefficient of the sidewall of the W-shaped pit is in the shape of a ring before the injection begins.The top surface of the piston gradually increases,and the high heat transfer coefficient region of the bottom surface of the pit appears in the middle position in the radial direction and gradually decreases toward the both sides in the shape of a ring.(2)The high heat transfer coefficient region of the top surface of the cylinder appears in the middle position in the radial direction and gradually decreases toward the both sides in a ring-like shape.(3)The high heat transfer area of the cylinder wall surface appears in the lower part of the cylinder near the head of the piston,and the heat transfer coefficient gradually increases from the top of the cylinder to the lower end.The heat transfer coefficient of the combustion chamber wall and the corresponding position of the oil bundle increases after the combustible mixed gas pressure in the cylinder is ignited.