Development of scalar dissipation rate based reaction rate models for the large eddy simulations of premixed flames

This project aims to develop an efficient Scalar Dissipation Rate (SDR) based reaction rate closure for the Large Eddy Simulation (LES) of turbulent premixed flames. Although SDR based closures are well established for Reynolds Averaged Navier Stokes (RANS) simulations of non-premixed flames, they are rare for RANS and LES of turbulent premixed flames, and no detailed evaluation of their performance in LES is available so far. In this project, the SDR based reaction rate closures will be developed and simultaneously assessed by a-priori analyses of explicitly filtered Direct Numerical Simulation (DNS) data, and a-posteriori evaluations of model performances in LES calculations, in a configuration for which experimental data is available. Based on the simultaneous a-priori and a-posteriori analyses, new models will be developed and their performance will subsequently be assessed. The best models will then be implemented in a LES code for turbulent premixed flame modelling. An efficient SDR-based reaction rate closure will provide a robust CFD based design tool for reliable, cleaner and cost-effective combustion devices operating in lean premixed mode (e.g. Spark Ignition engines, Lean Premixed Pre-vaporised (LPP) industrial gas turbine combustors).

The major impacts of this project can be summarised as follows: (i) Development of a high-fidelity alternative scalar dissipation rate (SDR) based LES modelling of turbulent premixed flames: The project outcomes will be disseminated through participation in international conferences (e.g. International Combustion Symposium, European Combustion Meeting, Society of Automotive Engineers meeting, ASME Gas Turbine meetings) and publication in scientific journals (e.g. Combustion and Flame, Physics of Fluids etc.). The DNS database resulting from the project will be made available to other interested researchers upon request. The project-students will manage a website for data-exchange and documentation, and specific results will be made available for public download. A one-day workshop on SDR based premixed combustion modelling for LES at CUED at the end of the project to maximise the chances of technical dissemination and to attract attentions of relevant industrial sectors. (ii) IC-engine and gas turbine users and manufacturers: Improving the prediction abilities of models for turbulent premixed combustion will be of great benefit to the aforementioned industries for the development of new generation energy-efficient and environment friendly combustors. The supporting letters attached with the Case for Support indicate that Ford, ESR network, Rolls-Royce in the UK will be interested in the outcome of this work. The industrial colleagues will be invited to attend half-yearly progress meetings and the planned workshop at the end of this project so that they remain aware of the project development and their feedback is taken on board during the course of the project. In interactive website will be maintained throughout the project with information on data-exchange, documentation, and specific results will be made available for public download along with the latest findings in the open literature. It will therefore serve as an important source of information for combustion modellers both in academia and industry. (iii)PhD students who will be engaged in this project: The PhD students will receive significant training on a variety of topics (DNS, LES, reduced chemistry, combustion model development). In the project, both students will learn advanced computational techniques for simulation (LES, DNS) and improve their analytical and mathematical skills. It is hoped that the experience of presenting their research in the form of peer-reviewed papers and conference presentations will make them a well-rounded researcher during the course of this project. Moreover, the PhD students need to present their work periodically in project review meetings and maintain the project website, which will also be beneficial for them in terms of developing project management and presentation skills. They will also have opportunities to interact with the academic and industrial contacts of the PIs, which will help their academic development, and also help them to develop a range of transferable skills such as communication, teamwork and project management. This, in turn, will give an edge to the students in current competitive job markets. (iv) Research groups of UL and CUED: The collaboration between UL and CUED is one of the major strengths of this project which will lead to broadening of research capabilities of both the PIs. Moreover it is expected that this project will certainly give rise to open questions which form the basis of further investigations by the PIs, and the usefulness of the present project will be exploited to attract industrial and research grant funding for its future follow-ups. It is likely that the understanding gained from this project will subsequently be applied to engineering combustion applications, possibly through the Knowledge Transfer Partnership (KTP) scheme in collaboration with industry in future, which will also ensure effective assimilation of this project's outcome in the relevant industrial sectors.