Abstract
For an air-cooled engine, designers must choose the number of fins required for cooling, then arrange them along the cylinder at a suitable fin pitch. Most motorbikes mount their air-cooled engines at a slant, with their cylinder centralaxis not perpendicular to the air flow. This study investigated the cooling characteristics of air-cooled experimental cylinders, with various fin pitches and number of fins, mounted at tilt angles between 0°(vertical) and 90°(horizontal),in a wind tunnel at air velocities of 20km/h (5.6m/s) and 60km/h (16.7m/s). Heat release from the cylinder was measured, air flow between fins was observed using the smoke wire method, and air flow over fin surfaces wasobserved using the oil film method. Results indicated that, except at 20km/h (5.6m/s) and a pitch of 7.5mm, cylinder cooling increased as tilt angle increased from 0° to 40°, then decreased when the cylinder tilt angle exceeded 40°. Only at 20km/h (5.6m/s) and a pitch of 7.5mm, cylinder cooling increased as tilt angle increased from 0° to 30°, then decreased when the cylinder tilt angle exceeded 30°. Cylinder cooling was maximized with 7 fins pitched at 10mm.
