Abstract:

A fully hydraulic variable valve actuation was developed and mounted on a SD2100 diesel engine to optimize combustion process. Early intake valve closing (EIVC) mode was utilized to achieve continuous adjustment of intake valve closing (IVC) and effective compression ratio (ECR). Gasoline was blended with diesel at volume fractions of 30% and 50%, and the combustion characteristics of blended fuels were investigated. The experimental results show that: both EIVC and increasing gasoline blended ratio prolong ignition delay; With the advance of IVC, peak rate of heat release increases firstly and then decreases, exhaust gas temperature is enhanced, and cyclic variation is increased; With the increase of gasoline blended ratio, peak rate of heat release is increased, exhaust gas temperature is reduced, and cyclic variation is nearly unchanged while IVC is close to that of the baseline. When IVC after bottom dead center (ABDC) crank angle (CA) is advanced to -58° and gasoline blended ratio is fixed at 50%, combustion process similar to cool flame is observed.

Key words: diesel engine, early intake valve closing, gasoline and diesel blended fuel, rate of heat release, variable effective compression ratio