INFLUENCE OF THE COMPRESSION RATIO ON COMBUSTION AND EMISSIONS PARAMETERS OF THE DIESEL ENGINE

Abstract

This paper is based on experimental research of the impact in automatic variable compression ratio on working process parameters in diesel engine. The possibilities of operating a direct injection diesel engine with lower geometric compression ratios were investigated. This is why the geometric compression ratio was changed in the range from (17.5 to 12.1). The differences in compression ratio were provided by interchangeable pistons, in addition to modification in piston chamber diameter. Variable compression ratio diesel engines are more advantageous in terms of fuel efficiency and reduced emissions over conventional diesel engines. Compared to conventional diesel engines, the NOx and particle emissions were significantly reduced. The amount of the fuel burned at the first stage (premixed combustion) significantly increases with the decrease of the compression ratio at constant amount of the injected fuel and constant engine speed. Optimal compression ratio value is a compromise between fuel consumption and particle emission, at optimal injection advance angle. Summarily, we suggest the diesel engines with variable compression ratio that could improve cold start-ability, low load operation, enable multi-fuel capability, increase fuel economy and reduce emission.