Analysis of thermal loads in air cooled SI engine

In the spark ignition engines with air cooling system the thermal loads of the cylinders and cylinder heads are much bigger than in the water-cooled engines and the loads are not uniform on the whole surface of these elements. Recently most of the cylinders and cylinder heads of the two-wheel vehicles had long ribs that caused a bigger noise and an increase of the mass of the elements. The paper includes the modelling process of the thermal loads and temperature distribution of the cylinder and cylinder head of the two-stroke engine 115 cm3 capacity cooled by air at mean engine load. The results of simulation carried out in ANSYS program with creation of the mesh in CATIA were verified by the experiment on the real engine. The results obtained in the tests and the simulation show, that long ribs have not an effect on the decrease of thermal loads of the cooling elements. The paper includes the colour graphs with deviation of the parts, temperature on the surfaces and thermal stresses. Maun work results allow finding that the cooling heat in the air-cooled two-stroke engine increases with the engine speed and cooling energy, boundary condition enables determine the convection coefficient for heat exchange calculations and FEM enables the prediction of the surface temperatures of the walls, the accuracy of temperature depends on the determination of the outflow temperature of the air.