ID 93

Split Injection Spray Characterization of three Different Types of GDI Injectors at Various Fuel Temperatures

 

Abstract:

Split injection strategies has been experimentally and numerically proven to reduce exhaust PM/PN emissions of Spark Ignition Direct Injection engines due to less fuel impingement on the cylinder wall or piston. In this study, various closely coupled split injection strategies are investigated on three different types of GDI injectors by using high speed Mie-scattering and schlieren methods. Three different injectors are a multi-hole injector, a four slot injector and a one slot injector. Various split injection strategies, including single injection, double injection, triple injection and quadruple injection were investigated. Fuel pressure was set at 100 bar, and ambient pressure was maintained at 50 kPa (abs.). n-Heptane was chosen as test fuel, and fuel temperature ranged from 20 °C to 140 °C. For different split injections, dwell time between injections was set at 0.4 ms, and each injection duration was set to the same for each injection event. Total injection mass was kept at 24.55mg of the multi-hole injector (fuel temperature at 20 °C). Results show that split injection strategy can reduce the liquid spray penetration, which is more obvious when using quadruple injection strategy. However, by using split injection strategy, fuel delivered later evaporated slower than the fuel delivered at the beginning of the injection. Fuel distribution was mainly governed by injector configuration when fuel temperature was lower than 90 °C. However, the fuel plumes of the three injectors collapsed to the central line of spray when fuel temperature was higher than 120 °C regardless of split injection strategy. Collapsed fuel spray resulted in longer fuel penetration of single injection. By using triple or quadruple injection strategies, the penetration of collapsed fuel spray was shorter than that of fuel spray at fuel temperature of 20 °C when using single injection.