Optimization of Injection of Pure Rape Seed Oil in modern Diesel Engines with Direct-Injection 2007-01-2031
Natural vegetable oil like rape seed oil is a potential substitute for regular fuel for diesel engines.
Compared to other biogen fuels like rape seed methyl ester (RME), pure rape seed oil is neutral towards groundwater and it needs considerably less energy and additives for production.
Different physical properties of rape seed oil compared to Diesel fuel are the reason why conventional Diesel engines can hardly be used satisfactorily with rape seed oil without being modified. Poor exhaust-emission behavior is caused by the incomplete combustion. Due to poor spray atomization of vegetable oil, an increased fuel entrainment in the lubricating oil, carbonization in the combustion chamber and deposits at injectors and valves are further drawbacks of injection systems designed for conventional diesel fuel.
The preheating of this fuel can solve some problems. But for optimal operation of a Diesel engine operated with rape seed oil, adjustments of the injection system, the mixture preparation and the combustion are necessary. An optimized injection behavior can reduce the wall wetting of the combustion chamber with fuel due to a long injection spray cone and the corresponding fuel entrainment into the engine oil.
There are hardly any scientific investigations on injection behavior of pure rape seed oil in direct injection Diesel engines. This paper presents results of the precise analysis of the spray propagation of vegetable oil during the unfired operation in a pressure chamber. Different injection pressures, fuel temperatures and the nozzle geometry are the focus of this investigation. The investigations were realized by an injection system with inline injection pump and with a common rail injection system as well.
The results will contribute to define injection systems, which are necessary for the use of pure rape seed oil.