Abstract
Keywords:
Pilot injection, injection strategy, soot formation, combustion process
Abstract:
The main source for soot formation during the combustion is the interaction of liquid fuel or a very rich air/fuel-mixture with the flame. This effect appears especially in modern direct injection Diesel engines where the injection is often split in a pilot and a main injection due to noise reasons. After the ignition of the pre-injected fuel a part of the main injection can interact with the flame still in liquid phase as the fuel is injected straight towards the already burning cylinder areas. This leads to high amounts of soot.
The injection strategy for this experimental study overcomes this problem by separating the injections spatially and therefore on the one hand reduces the soot formation during the early stages of the combustion and on the other hand increases the soot oxidation later during the combustion. The separation of the different part-injections is proven using an atmospheric pressure chamber to visualise the fuel sprays with global illumination and a CCDcamera.
The effects of the new injection strategy on the combustion process itself was investigated with a single-cylinder heavy-duty research engine in comparison to conventional injection engine operation using cylinder pressure indication and exhaust gas analysis. This allows the assessment of the operating behaviour of the engine and the achievable emission reduction potential.