INTAKE VALVE MODELLING AND STUDY OF THE SUCTION AIR PRESSURE AND VOLUMETRIC EFFICIENCY IN A FOUR STROKE INTERNAL COMBUSTION ENGINE
Keywords:
Intake valve, suction air pressure, volumetric efficiencyAbstract
The air pressure inside a cylinder on the suction stroke is the measure of volumetric efficiency and air quantity drawn on the suction stroke of the engine. Intake air pressures inside a cylinder have been computed in each degree of the suction stroke and exhaust stroke with seven different intake valve diameters from 14 mm to 32 mm, with increments of 3 mm in diameter in a four stroke internal combustion engine. The results of the computational work show that cylinder pressure on the suction stroke starts decreasing from the suction valve full opening timing at 200o crank angle after the top dead centre (TDC at 180o) until the middle of the suction stroke at 255o crank angle for all the intake valve diameters, and again cylinder pressure increases until the suction valve starts closing at crank angle 340o. The effects of the intake valve diameter on cylinder pressure on the suction stroke are also found comparable between the suction valve opening and closing period. The increase of intake valve diameter provides a significant decrease of cylinder pressure until middle of the suction stroke at crank angle 255o, when the piston moves downward, but these pressure differences again reduces until the suction valve is completely closed. The air pressures inside the cylinder on the suction stroke with different intake valves become nearly the same when the suction valves completely close. Thus the necessity for increasing the intake valve diameter is not an important factor to increase volumetric efficiency, although the manufacturers are at present considering to increase the number of intake valves as in a 12 or 16 valve engine instead of an 8 valve engine in a four cylinder SI engine.
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