Injector nozzle design and injection strategy for fuel economy in a light-duty diesel engine

Abstract

In this study, the effects of the orifice diameter and hole numbers and the multi-stage split injection strategy on efficiency and exhaust emissions in a diesel engine were investigated. Several injectors with orifice diameters of 117, 110, 100 μm and hole numbers of 8 to 12 were examined. An experiment involving a 0.5L single-cylinder diesel engine under low-load conditions was conducted. In a constant-volume combustion chamber, flame and OH chemiluminescence imaging were employed for measuring the flame penetration, lift-off length, and spray-to-spray interference after wall impingement. The efficiency and emissions characteristics were improved as the orifice diameter decreased from 117 μm to 100 μm. For the injectors with an orifice diameter of 117 μm, as the number of holes increased from 8 to 10, the exhaust characteristics and efficiency were improved due to the higher injection rate, divided fuel quantity per nozzle hole, and wider fuel distribution. However, the injectors with an orifice diameter of 110 μm resulted in the opposite tendency

when the number of holes increased from 8 to 12, the exhaust emissions and efficiency deteriorated due to flame interference. The injector with a smaller orifice diameter and larger hole number, maintaining the hydraulic flow rate, resulted in improved efficiency and reduced emissions. The multi-stage split injection strategy with five injection events was developed to minimize the maximum pressure rise rate in the cylinder. Compared with the conventional two pilot and single main injection, the heat release process split and reduced the maximum heat release rate and heat transfer loss. This work will provide the effects to be considered on the optimization of injector nozzle parameter and injection strategy for improving fuel economy and emissions characteristics in a light-duty diesel engine.