CYLINDER’S LINER WEAR CHARACTERISTICS IN TWIN CRANKSHAFT INTERNAL COMBUSTION ENGINES

Abstract

Conventional internal combustion engines have been around for more than a century. Due to its high efficiency and low cost. The overall efficiency of IC engines approaches 50%. This means that only about 50% of the fuel is converted into useful work, and the rest of fuel power is useless energy mainly due to friction between moving parts. Friction is the worst enemy of machinery. It wears out metal, wastes power and generates heat. Friction occurs in all moving parts in the engine, like piston rings, journal bearings, valves and cams. Friction between piston rings, cylinders liner responsible for about half of the usefulness energy (1). Sliding contacts between a piston ring and a cylinder liner leads to a variety of different friction mechanisms during one working cycle of the engine. Owing to the variations in load, speed and counter surface effects, lubrication conditions in a ring/liner contact are strongly transient, which is reflected by variations in the friction and wear behavior. Wear in cylinder liner causes inefficiency seal, and it may result in increased oil consumption, leakage, blow-by, and increasing fuel consumption. Combustion pressure cause a force on piston, the horizontal component is a side thrust force which is normal to liner wall. This force is responsible for the friction between piston ring and wall and then wear of cylinder liner. Beside the minor causes by piston ring surfaces finishing and coating, cylinder liner material, cylinder liner surface finishing and coating and cylinder liner out of roundness. The aim of the present work is to minimize side thrust force as it is major cause of cylinder liner wear. In the present work an arrangement of twin crankshaft model has been manufactured in Sudan University of Science and Technology-College of Engineering as a solution attempt to overcome cylinder friction and then reducing cylinder wear. Twin crankshaft engine uses two contra-rotating crankshafts, geared together, and connected to a piston through two connecting rods driven by one crankshaft. Experimental work was carried out to investigate wear characteristics using three different engines arrangement inline, offset and twin crankshaft engines, for two engine’s speeds. A computer program was used to model the three engines arrangements and to obtain their theoretical performances. A comparison between the experimental results of the three engines arrangement showed that twin crankshaft engine arrangement is a promising solution for reduction of cylinder liner wear. This is in agreement with the predicted results obtained by the computer program.