Improvement of a High-Performance Diesel-Engine by means of Investigation on different Injection Strategies

Test bench investigations on a high-performance diesel engine equipped by regulation with an air- restrictor have shown, among other things, that different injection strategies have a remarkable influence on the engine performance and exhaust emissions. A part of these investigations is reported in this paper. In particular the attention here is directed to the following two topics:

• comparison between two different injector types (solenoid vs. piezo)
• comparison among different injection timings (only main injection vs. pre-injection).

Looking for a continuous increasing of engine performance a detailed understanding of the injection and combustion processes is mandatory. For this task a fast response 3D-CFD-simulation-tool has been applied to the engine development process. This tool acts as a virtual eye inside the combustion chamber which permits to have a look beyond the test bench. So it was possible to find explanations for the occurring phenomena and then virtually test new approaches to improve the engine performance (virtual engine development). The results show, e.g., that against the expectations the piezo-injector is not overall more performing than the solenoid injector and the setting of a pre-injection under particular circumstances permits to increase the engine performance in the speed range above the choking line of the air restrictor. All the presented investigations take into account the FIA (Fédération Internationale de l'Automobile) general regulations and Volkswagen self-limitation on the smoke emissions for race engines.