Future and Potential of Diesel Injection Systems

Abstract

Heavy duty diesel engines are in conflict between the goals of emission reduction and optimization of fuel consumption.To fulfill future more stringent exhaust gas limits further developments on diesel engine technology are necessary. The diesel injection system assists this development and becomes the decisive factor to reach the emission targets. In the last 30 years a trend to high pressure fuel injection systems with an increase of maximum injection pressure from 800 up to 2000 bar is visible. In future very flexible high pressure fuel injection systems are necessary with multiple injection and rate shaping capabilities and a maximum injection pressure beyond 2000 bar. Very important is a high efficiency of the fuel injection system itself to reach low fuel consumption. New product engineering like new nozzle design (k-factor, vario nozzle,..) or new developed actuators are key factors for the fuel injection development. With a flexible diesel injection system in each point of the engine map the optimum rate shaping, injection timing and multiple injection is possible to get the best compromise between emission trade off and fuel consumption. For example with exhaust gas recirculation (EGR) a rectangular type main injection with high injection pressures at full load is recommended. On the other hand without EGR in this point of the engine map a boot or ramp shape injection leads to the best emission results at constant or improved fuel consumption. With a coupled post injection the soot emission could be reduced. The late post injection is assisting the exhaust gas aftertreatment systems. The regeneration of the diesel particulate filter is for example because of too low exhaust gas temperature without the support of the injection system not under all circumstances possible. The exhaust gas temperature management by late post injection is a measure to improve the efficiency of catalyst systems at low exhaust gas temperatures. Very important in future is the capability of the electronic control unit (ECU) of the diesel injection system to control air management, exhaust gas emission management, tolerance reduction, diagnosis, vehicle functions and combustion process by the fuel injection system.