Abstract
The need to reduce NOx- and particulate emissions becomes more important for the development of modern diesel engines because of future exhaust emission standards. Furthermore current European legislations for CO2 emission and the increasing shortage of fossil energy sources make it important to reduce the fuel consumption.
Engine modifications, like the increasing of injection pressure can improve mixture formation and lead to an increasing homogenization of air/fuel mixture. The consequence can be a better combustion of air/fuel mixture and an increasing reduction of CO2 emissions of diesel engines. A more homogeneous air/fuel mixture in combination with an exhaust gas recirculation reduces the particulate matter emissions and simultaneously the nitrogen oxide emissions. Furthermore the use of alternative fuels, extracted from biomass, has a high potential to reduce CO2 emissions from their production up to combustion in the engine.
So the employment of alternative fuels with simultaneous optimizing the mixture formation presents an important mean to reduce the emissions and the fuel consumption of modern diesel engines.
In the project “Ultra High Pressure Injection of Alternative Diesel Fuels”, an injection system was build up which is able to inject alternative fuels with an injection pressure up to pInjection = 3,000 bar. Simultaneously a pressure chamber was used for diesel operation in which a chamber pressure and temperature level can be realized up to pChamber = 60 bar respectively TChamber = 200 °C.
The paper presents results of the spray behaviour, which were measured in a pressure chamber with optical measuring devices (high-speed camera and Phase-Doppler-Anemometry, PDA) and conditions like an engine. To characterize the spray more detailed, optical laser measurement devices will be used to investigate the geometrical size of discrete droplets. A simultaneously carried out Computation Fluid Dynamics (CFD) simulation completes these investigations.
The mean droplet size, which is derived from the laser optical investigations, gives information about the quality of the mixture formation and the involved combustion and emission formation.
The paper presents the main results of the investigations and concludes with an outlook to ongoing research activities.
KEYWORDS: ulra-high pressure injection, alternative diesel fuels, spray visualization, Phase-Doppler-Anemometry