| Summary: | 碩士 === 國立成功大學 === 機械工程學系碩博士班 === 97 === This study utilizes heat transfer and computational fluid dynamics theory to numerically analyze the 3-D thermal-hydraulic characteristic for motorcycle engines with air-cooling and water-cooling, respectively.
For air-cooling motorcycle engine, the finite element method has been used to solve the temperature field and heat transfer rate for each component (intake valves, exhaust valves, piston, piston rings, cylinder head and cylinder) of motorcycle engine when the piston is in the Top Dead Center (TDC) and Bottom Dead Center (BDC), respectively. For water-cooling motorcycle engine, the flow field and the velocity distribution for air flow over the space between the grille, tire, the mud cover and radiator of the motorcycle were analyzed for different motorcycle speed and grill angles. In addition, the heat transfer performances of the radiator were examined in conduction with the radiator computer-aided design radiator software.
The results showed that the fraction of heat transfer rate for each component are as follows: intake valves 11％, exhaust valves 8％, cylinder head 21％, the piston 35％ and the cylinder 25％. The average velocity inside the radiator is only about 20% to 22% of inlet velocity when the inlet velocity is varied from 2 m/s to 20 m/s. When the grille angle is decreased α=-10°,the radiator average velocity and the heat transfer rate are increased 10.2% and 8.4 %, respectively, while the grille angle is increased α=+10°,the radiator average velocity and the heat transfer rate are decreased 3.7% and 3.1%, respectively. The numerical prediction is in good agreement with experimental data within 17%.
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