Development of Air-Cooled Cylinder by Utilizing Natural Convection

An air-cooled engine with a finned cylinder may have residual heat between the fins. Residual heat decreases heat release from the cylinder when cooling air is not forced over the engine. In order to induce natural convection in the cylinder, cooling ports were drilled in the fins parallel to the cylinder axis to determine if residual heat could be decreased and additional cylinder cooling could be developed. The effects of the fin configurations on air-cooling were investigated to utilize the cooling ports for a stationary engine and a non-moving motorbike engine.

The experimental cylinder design permitted variation in the number of fins and fin pitch. Numbers of fins that had various port sizes and port positions were investigated; in addition, the temperature inside of the cylinder and in the space between the fins was measured. Results indicated that heat release from the cylinder was increased by utilizing the fins with ports as compared to the fins without ports. It was also found that fin pitch, number of fins, port size, port position, and number of ports have significant effects on cylinder temperature. These results can be utilized to improve the design of an air-cooled cylinder by utilizing natural convection.