Riassunto analitico
The actual state of the automotive industry is that of an extremely fast-changing environment. Uncertainty is the key word which best describes the current situation in both production and research and development stages. On one side, the way seems to be already well-directed by external factors towards a fully electric world, to become reality in the close future. On the other side, anyway, there are still a lot of unclear matters about the leading technologies of this change, in terms of raw materials, primary processes, safety and recycling/after-life issues. At the same time, other technologies are growing importance and may possibly become valid alternatives. Hydrogen´s potentials are extremely high, both in its application as fuel cell and as primary fuel for new internal combustion engines. Anyway, both these applications have as a main limit the challenging and costly implementation of the storing system for such a material.
On this scenario, the idea of alternative fuels is still present since many years now with always new concepts, but they never became strong candidates to replace the traditional fuel. Among them, E-Fuels are becoming popular in the very last years. Yet, they still need that technological breakthrough to show themselves as valid source of energy for light-duty vehicles´ propulsion.
Inside this uncertain world, the most solid certainty is the fact that simulation, digital development, and digital testing are playing one of the most important roles in all the stages of the product development. The concept of CAE tools is for many years now a strong reality in the automotive industry. Digital mock-ups are the center of gravity of the whole process, thanks to their fast and cheaper respond to product modifications, development, analysis, and optimization when compared to their physical counterparts. Furthermore, the availability of data in the nowadays industry is so vast that real-world testing and assessment will become of secondary importance.
The thesis work here presented places itself between these two concepts. One of the tools available in the CAE world, that is 3D-CFD, is exploited to investigate and analyze a rediscovered concept of combustion (TJI) for a high-performance propulsion system. A 3D CFD model is established, together with a methodology for speeding-up future analysis, to support the early stage of development of a Porsche engine.
The software employed to carry out the numerical simulation is the new plug-in for STARCCM+, In-Cylinder, developed by Siemens PLM.
Being the status of this engine in the very early stage, the numerical model is tuned and calibrated against experimental data measured at the test bench, where a single-cylinder configuration is tested. After building up the model, two operating points have been analyzed, naming full load/max speed (FL) and catalyst heating (KH) partial load condition. Multicycle analyses have been performed for both and a heat transfer model has also been implemented for the first working condition. Further analyses have been carried out to enrich the model and its capabilities. A deeper analysis of the jets ejection phase from the pre-chamber has been performed and two different ignition models have been tested to better replicate the early stages of combustion. Before the implementation inside the full cycle in-cylinder simulation, the spray has been addressed in detail, trying different modeling techniques. In addition to that, two more complex multi-component fuels have been introduced in the FL model.
Regarding the KH operating point, two different injection philosophy have been tested, together with two different ignition strategies.
The work is structured into two main parts. A first introductory one, where general concepts about pre-chamber combustors and the 3D-CFD approach employed are reviewed and fixed. Then, the results obtained for the analyzed engine and built model are presented.
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