Investigation on the response time of a self-regulation variable compression ratio engine

Abstract

Today, the greenhouse gas (GHG) emissions (specifically, CO2) represent the greatest challenge of the internal combustion (IC) engine and consequently, now, more than ever, the passenger car industry is looking for technologies meant to address this issue. Since CO2 emission is related to the combustion process occurring inside the engine, its reduction is inherently connected to lowering the fuel consumption, meaning that the only way to reduce it in the IC engine is to increase its overall efficiency. One solution to do this over the whole operating area is to fit the engine with a variable compression ratio (VCR) system, which may be advantageously combined with other enhancing-efficiency technologies. However, to avoid knocking and pre-ignition, such an engine should feature an adequate response time during the transition from the maximum compression ratio to the minimum one. Consequently, this paper describes a theoretical investigation on the kinematics and dynamics of a hinged VCR engine’s upper block tilting motion, aiming to show that this engine, as an automatic system with self-regulation of compression ratio, can respond adequately when the operating conditions change fast. This is paramount for the passenger car road mobility, which means anything but steady operation.