A TOGNUM GROUP BRAND Engine technology Common Rail Fuel Injection: Key technology for clean and economical combustion Head of Development Turbocharging, Fuel Pre-development, L'Orange GmbH Team Leader, Engine concepts, Components Engine concepts, Components and Systems With common rail fuel injection, the combustion process can be optimized to achieve low pollutant levels combined with lower fuel consumption. Fuel is injected into the combus- tion chamber from a common rail under high pressure. The electronic control system ensures that the start of injection, the quantity and time are independent of the engine speed. In 1996, with the Series 4000 engine, MTU was the first manufacturer of large diesel engines to introduce common rail fuel injection as a standard feature. Pioneer of the common rail fuel injection system The emissions regulations for diesel engines in applications such as ships, trains and heavy- duty off-road vehicles and gensets worldwide are becoming more stringent and make exten- sive modifications to the power units necessary. At the same time, customers are constantly call- ing for more economical engines. Exhaust after treatment systems such as SCR catalytic con- verters (selective catalytic reduction, short: SCR) or diesel particulate filters are one way of lowering emissions, but also have a greater space requirement and potentially increase the engine's maintenance needs. For these reasons, MTU primarily pursues a policy of reducing emis- sions by internal engine enhancements. Fuel com- bustion inside the engine is improved so that, if at all possible, emissions are not produced in the first place. If necessary, MTU introduces a

second phase of emission control whereby re- maining harmful emissions are removed by ex- haust aftertreatment systems. Fig. 1 : Common rail system for Series 4000 The performance and flexibility of the CR system create the prerequisites for clean and efficient combustion. As part of the internal engine enhancements, one of the major means of control for obtaining clean fuel combustion, besides exhaust gas recirculation, is the fuel injection system. It is designed to inject the fuel at high pressure at precisely the right moment, while also accu- rately metering the quantity of fuel injected...

Comparison of injector sizes for engines with different cylinder capacities, inclu- ding injectors for the current MTU Series 1 600, 2000, 4000 and 8000 engines. (light grey: non-MTU engines) Passenger Series Series Series Series Series Ship injector injection phase initiates advance combustion to provide controlled combustion of the fuel in the main injection phase. This reduces nitrogen oxide emissions, because the abrupt combus- tion prevents high peak temperatures. A post injection phase shortly after the main injection phase reduces particulate emissions. It im- proves the mixing of fuel...

Fig. 4: Injector with integrated fuel reservoir The use of injectors with an integrated fuel reservoir prevents pressure fluctuations in the common rail system and, therefore, a momentary undersupply or oversupply of fuel to the injectors. @ Limiting valve @ Actuator solenoid © Nozzle element made of resistant steel @ Electrical connection version of the system as described is also wel suited for use in small capacity industrial en- gines. In the case of engines with larger cylinder capacities, however, the conventional common rail system is now revealing its limitations, since these require...