A New Design to Achieve Variable Compression Ratio in a Spark Ignition Engine

Abstract

Spark ignition engines are known to have low part load efficiencies which contribute in increasing fuel consumptions. Compression ratio plays a significant role in deciding the performance of an engine at different load conditions. For this reason, the variable compression ratio (VCR) engine has, since long, been considered as an effective solution to the problems encountered while operating an engine at varying load conditions. There has been a significant amount of effort by researchers as well as OEMs for developing efficient and optimum designs of the VCR engine. The design makes use of a cylinder head which is equipped with a movable ram for varying the clearance volume. Actuators have been used to actuate the movement of the ram which facilitates to vary the compression ratio. The whole system has been designed keeping the potential challenges in mind and means have been sought to negate them. VCR engines give more flexibility to the user and at the same time, improve performance characteristics such as brake power, brake thermal efficiency, and torque while decreasing emissions and lowering specific fuel consumption.