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The past decade significant research effort has concentrated on the DI diesel engine due to stringent future emission legislation which requires drastic reduction of engine tail pipe pollutant emissions, mainly PM and NOx, without significant deterioration of specific fuel consumption. Towards this effort, the important role of modeling to investigate and understand the impact of various internal measures on combustion and emissions has been widely recognized. Phenomenological models can significantly contribute towards this direction because they have acceptable prediction capability and the advantage of low computational time. This enables the production of results, on a cycle basis, that indicate the effect of various parameters on both engine performance and emissions. Therefore their use can significantly reduce engine development time (i.e. reduction of experimental effort) and cost.

In the present work is presented a detailed evaluation of an advanced diagnostic technique, developed by the authors, for the determination of diesel engine condition and tuning. For this purpose, an extended experimental investigation has been conducted on a prototype test engine installed in the author's laboratory. During the measurements various operating parameters (i.e. torque, fuel consumption, injection pressure, cylinder pressure, peripheral temperatures etc.) have been recorded at various operating conditions (i.e. engine speed and loads). Initially the engine operated at its normal conditions (i.e. reference state). Then, two “virtual” faults (i.e. reduction of injector opening pressure and increase of cylinder mass leakage) were introduced, that affected engine operation.

A difficulty which exists when applying diagnostic techniques on large-scale diesel engines operating on the field, is that usually it is not possible to obtain measurement data at a wide engine operating range due to a number of constraints. In the present work is investigated the possibility to overcome this practical difficulty originating from the test procedure for engines operating on the field (i.e. marine or stationary applications). The main objective is to examine if a diagnosis procedure provides similar results when applied at various engine operating conditions. For this purpose an existing diagnostic technique, developed by the authors, is applied at different operating conditions on a large-scale two-stroke diesel engine used for power generation in a Greek island.

A major challenge for researchers and engineers in the field of diesel engine development is the simultaneous reduction of both NOx and soot emissions from diesel engines to comply with strict future emission legislation. One of the promising internal measures that focus on the reduction of soot emissions is post fuel injection which does not have a serious effect on NOx emissions. The main parameters involved when using this technique are post fuel quantity and dwell angle between the main and the post fuel injection events. In the present work a detailed computational investigation has been conducted to determine the effect of post fuel injection on engine performance and pollutant emissions (NOx and soot). To this scope, a phenomenological multi-zone combustion model has been used, properly modified to take into account the interaction of post and main injected fuel amounts.

Considering future emission legislation and the global thermal problem, two are the main issues that are of specific concern for the future of the diesel engine, specific gaseous pollutants and CO2 emissions. Both parameters are related to engine bsfc consumption directly or indirectly. The last is becoming even more important considering current fuel prices and the projection for the future indicating a trend for increasing fuel prices. The last decade significant improvement have been accomplished in the field of diesel engine efficiency that has resulted to considerable reduction of engine bsfc. It is obvious that despite improvements in diesel engine efficiency still a considerable amount of energy is rejected to the environment through the exhaust gas. Approximately 30-40% of the energy supplied by the fuel is rejected to the ambience.