Optimization of Crankshaft Offset to Design Crank Slider Mechanism with Improved Power Transmission Efficiency

Abstract

Increasing consumption and depleting reserve of the petroleum fuel calls for further improvement in the efficiency of internal combustion (IC) engines. Ensuring maximum piston effort and its efficient transmission to the crankshaft are the two major factors governing the efficiency of an IC engine. A major challenge in designing an IC engine is the poor transmission efficiency of crank slider mechanism at the time of peak pressure. An analysis made in the crank slider mechanism having connecting rod to crank ratio as 4 shows that at the time of peak pressure, the mechanism produces only 33.18% of the maximum attainable crankshaft torque. The solution realized through this work is an attempt to improve the transmission efficiency of the crank slider mechanism by slightly offsetting the crankshaft. Offset in the crankshaft was optimized so as to achieve a crank slider mechanism with maximum transmission efficiency. An improvement of 0.74% in the crankshaft torque results by shifting its crank center through 23.028 mm horizontally rightward and 6.663 mm vertically upward. 

Keywords: Crank slider mechanism, IC engine, offset crankshaft, stroke length