چكيده به لاتين
Abstract:
Nowadays, heat transfer and cooling of internal combustion engines are important topics. The study of valve cover heat transfer with surroundings is important in air-cooled engines. Rocker arms, valve springs and valves are located between valve cover and cylinder head of the engine. Heat stresses should not exceed the specific level which will lead to fatigue cracks. Thus heat transfer and valve cover heat flux are investigated in this study. For this research, an air-cooled single cylinder spark ignition engine with gearbox is used. This engine is manufactured by HONDA company and its volume is 125cc. In order to do experiments, the engine is installed on a designed chassis and temperature measurement is conducted in different spots of cylinder head cover. Thermocouples were installed on valve cover near intake valve and exhaust valve. Then temperatures were measured by a thermometer in different RPMs. Temperature measurement progressed until the valve cover temperature reached the steady state. In order to simulate a real operation condition, different braking loads were applied. Afterwards the braking torque is calculated with gear equations of the gearbox. In the next step, heat flux of the valve cover around the intake valve and exhaust valve is calculated and results indicate that increase of the engine RPM and braking torque will cause higher temperature in different spots. Also polynomial regression of results is done to predict other states by means of diagrams slope. In addition, in order to improve the heat transfer of the valve cover, assessment of other alloys of aluminum is considered.Error analysis and calibration of measuring instruments is also conducted. Investigating heat flux figures in steady state shows that, in fixed braking load, changes of heat flux in higher RPMs are more than changes in lower RPMS.
Keywords: Heat Transfer, Valve Cover, Honda Motorcycle, Thermocouple and Thermometer, Braking Torque
