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Method for Hydraulic Flow Characterization of Idi Diesel Fuel Injectors
Published September 28, 1995 by Institution of Mechanical Engineers in United Kingdom
The main challenge for the optimization and tuning of Diesel engines will be to meet the future emissions standards. The increasing difficulty is due to the standards level itself as well as the tendency to higher vehicle mass and downsizing of the engines. A major step in the right direction can be made by applying electronic control to timing and fueling combined with closed loop EGR in order to improve the emissions level, the fuel consumption and the driveability.
Meanwhile, there is still a major effort to be made on the basic hydraulic parameters of the chosen injection system in order to optimize the air-fuel mixing and thus the combustion. While optimizing the injection parameters regarding the exhaust emissions, one may learn to choose an injection system avoiding local and axial spray impingement as well as spray recirculation, all responsible for soot emissions. Typical parameters may be pumping and injection rate, which have to fit for best compromise between high engine power output and low load emissions level. But even injection systems with comparable pumping rates may produce different results in soot emissions, due to differences in spray development and air-fuel mixing. This shows the need of a global characterization and the definition of more parameters.
The paper describes a characterization method for an IDI diesel fuel injection system with different pintle nozzle injectors. The method is based on the stationary characterization of the injectors by measuring the hydraulic flow and the spray impact force for different values of needle lift and cavitation ratio. The results of this characterization are then used for quasi-static flow calculation integrated in a fuel system model. These calculations tend then to give information about the spray opening and penetration behavior, which can also be found by measurement and visualization.