Effects of Local Premixing on Direct-Injection Stratified-Charge Combustion in a Constant Volume Bomb

The direct-injection stratified-charge engine is considered to be a promising alternative to conventional spark-ignition engines. It has the favourable features of high thermal efficiency, low carbon monoxide and nitric oxide emission levels as well as multifuel capability. It has, however the unfavourable feature of a high unbumed hydrocarbon emission level, especially during light-l'oad operations In order to conquer this problem, the locally near-premixed direct-injection stratified-charge combustion system was examined in this study, using a pancake type constant volume bomb. A mixing promoting projection was attached to the inner circumference of the bomb to make locally near-premixed mixture. Experimental analyses were made on combustion pressure histories and on stratification processes. Some improvements on the maximum combustion pressure, combustion duration and unbumed hydrocarbon emission level were obtained by this new system compared to the basic direct-injection stratified-charge combustion.