In-cylinder air flow structures are known to strongly impact on the performance and combustion of internal combustion engines (ICE). Therefore, the main objective of this study is to analyze the in-cylinder flow field characteristics of a single-cylinder small engine to see the effect of intake port inclination at equivalent rated engine speed using simulation model under various intake valve lift conditions. The variation of intake port inclination is -15˚, 0˚, 11.5˚, 15˚, 30˚ and 45˚. The engine geometry was created using SolidWorks, then exported and analyzed using commercial CFD method, CONVERGE. The result shows that the change of intake port inclination give effect to swirl ratio to be irregular shape. The bigger the inclination of intake port the smaller the irregular shape of swirl ratio. The change of intake port inclination also give effect to tumble ratio where the maximum tumble ratio occurs at -15˚. The bigger the inclination of intake port the smaller of the tumble ratio. The result shows that the in-cylinder flow structure is greatly influenced by the intake port inclinations irrespective of intake valve lift. Maximum Turbulent Kinetic Energy (TKE) was highest at full intake valve lift irrespective of the inclination. Also, the maximum TKE was the highest for -15˚ intake port inclination compared to other inclinations irrespective of the intake valve lift at equivalent rated engine speed. Based on the visualization of air flow in-cylinder engine, the air flow has the same tendency where vortices formation occurs below the intake valve. However, the change in the intake port inclination give effect to the change of the velocity magnitude. The bigger the inclination of the intake port the smaller the velocity flow at the in-cylinder engine will be. The maximum velocity occurs at the middle of in-cylinder engine. Finally, it is concluding that the analysis carried in this work is useful in predicting the flow and in-turn optimizing combustion chamber of modern internal combustion engines.
Keywords intake port inclination, in-cylinder flow, small engine, motorcycles, converge