Design and Dynamic Analysis of Different Balancing Mechanisms for Development of a Small Direct-Injection Spark-Ignition Optical Engine

Abstract Improving the performance of small engines, which have widespread use in two- and three-wheeled vehicles in several countries, is vital. Recently, direct-injection spark-ignition (DISI) technology, used on moderate- to large-sized engines, offers improved fuel economy, better transient response and reduced emissions. When applied to small-bore engines, DISI, however, further complicates the fuel impingement on in-cylinder surfaces and inhomogeneity in fuel-air mixture formation. Hence there is a growing demand for a comprehensive examination of in-cylinder processes to address these challenges using optical engines. Optical engines, incorporated with elongated piston and a transparent window therein for direct monitoring of in-cylinder events, give rise to increased unbalanced forces and thus lead to increased vibrations. Therefore, it becomes imperative to implement a suitable balancing mechanism to reduce the unbalanced forces within the space constraints of small engines. In the present study, three different balancing mechanisms, i.e., (i) crankshaft with counterweights, (ii) crankshaft with counterweights and primary balancer shaft, and (iii) crankshaft with counterweights and primary and secondary balancer shafts, are designed in solidworks. Subsequently, a dynamic analysis of these mechanisms is conducted using ADAMS/View to investigate the unbalanced forces. The resultant unbalanced forces are compared for different balancing mechanisms. The analysis revealed that the crankshaft with counterweights and primary balancer shaft (i.e., balancing mechanism-II) is suitable for the balancing of the small DISI optical engine (displacement volume of 200 cm3) under investigation. The methodology is helpful in designing and analyzing various balancing mechanisms for optical engines, particularly for small optical engines with space constraints.