Abstract
At low load operation using heavy fuel oil (HFO) and at engine start-up in a 4-stroke cycle marine diesel engine, a significant amount of smoke is generated. This paper presents results of improvement of combustion in a 4-stroke cycle medium speed marine diesel engine using marine diesel oil (MDO) and heavy fuel oil (HFO). The authors investigated the effect of fuel injection control using a novel fuel injection system (HIS: Hybrid Injection System) composed of a common rail system and a cam drive pump. The findings are the following: (1) At engine start-up using MDO, it is possible to reduce smoke by using low pressure pre-injection of a small amount of fuel. (2) In low engine load conditions using HFO, it is possible to reduce CO and smoke by low pressure pre-injection of a small amount of fuel and after-injection of large amount of fuel. (3) By using HFO as main fuel and MDO as sub fuel, it is possible to reduce CO and smoke significantly by low pressure pre-injection of a small amount of fuel and after-injection of large amount of fuel.
