Diesel Injection Analysis for New Premium Fuel Research and Emission Reduction.
[Tesi di dottorato]
The objective of this study was to bring a scientific contribute in the problem of reducing diesel in-cylinder emissions, and releasing the diesel engine from its dependence on petroleum. The first two introductory chapters of this dissertation contain an overview of these two issues and the techniques used nowadays to address them respectively. In this context, the emphasis is on the injection system parameters and the most interesting petroleum-diesel alternatives. Improvements of the injection system parameters help to meet future more stringent exhaust gas limits and seem to become the decisive factor to reach further emission targets. The search for alternatives to petroleum-based fuels is probably the only solution which, at the same time, may help to reduce the harmful exhaust emissions and to diversify energy sources, thus improving security of supply.
The first part of this work was dedicated to the design and implementation of a test bench for investigating the hydraulic injection behaviour of large diesel injectors (up to 1000 mg per stroke). This task was motivated by the need to develop the diagnostics for a new experimental 4-litres, single cylinder diesel engine. The test bench consists of an injection rate measuring system of the Bosch tube type that is able to completely define all injector characteristics as: Injection time (hydraulic start, end and corresponding delay from electric signal), injection rate and injected quantity. In the third chapter of this dissertation, first a brief overview is given of the state of the art of the injection system technology and of the physical measurement principle of the injection analyzer. Then, the design of the new injection meter is described. The implementation of the measurement setup with the data acquisition system and the development and implementation of the data processing algorithm are also presented. Some measurement results are shown to demonstrate the performances of the new injection analyzer.
The second part of this work aimed at contributing to a research project named “Future Fuels for Diesel Engines” and promoted by the FVV (Research Association for Combustion Engines), with partners the LAV and the Institute for Internal Combustion Engines and Automotive Engineering (Institut für Verbrennungsmotoren und Kraftfahrwesen, IVK). This project aimed on clarifying the influences of chemical and physical properties of synthetic fuels on combustion and emission behaviour at conventional diesel engine operation in order to define the basis for premium synthetic fuels. Therefore seven synthetic blends of components with different chemical structures and with a common matrix obtained by the Fischer-Tropsch (FT) process, were defined and investigated. Results were then compared to a reference diesel fuel following the requirements of EN 590. In last chapter of this dissertation an overview of the entire project is given. The main topic is, however, the investigation of these fuels’ behaviour with regard to injection through a commercial diesel injector. A study to identify dependencies of the injection rate profile on the fuel’s physical properties was conducted comparing the injection rate profiles obtained with the different fuels. This research was conducted using an injection test bench featuring a commercially available injection analyzer. Therefore a detailed description of this test rig, the experimental approach and the results obtained with this investigation are presented in chapter four.
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