Fundamental understanding of turbulent flame propagation in droplet-laden reactant mixture based on experimental and numerical investigations

This project aims to investigate the statistical behaviour of turbulent flame propagation in a droplet-laden mixture using both experiments and Direct Numerical Simulations (DNS). The effects of turbulence intensity, integral length scale of turbulence, group number, volatility, droplet diameter, and equivalence ratio (both overall and gaseous phase) on turbu-lent flame propagation in droplet-laden mixtures will be analysed in detail by carrying out extensive parametric studies to obtain fundamental physical understanding of the influences of these parameters on the flame propagation statistics, burning rate and pollutant formation (e.g. NOx generation rate). Although addressed to a limited extent by experimental studies in the past, an extensive DNS based investigation of this problem, supported by, and directly compared with, experimentation is yet to be reported in the existing literature. In this project, the fundamental physical understanding from both DNS and experimental data will be used to develop models in the context of the flamelets and Conditional Moment Closure (CMC) based reaction rate closures. Fundamental understanding of flame propagation into droplet-laden mixtures and its modelling will provide a robust cost-effective Computational Fluid Dynamics (CFD) based design tool for reliable, energy-efficient and cleaner combustion devices involving droplet-laden mixtures (e.g. Direct Injection (DI) engines, Compression Ignition (CI) engines, Aero gas turbines etc.).

The major impacts of this research endeavour are summarised as follows:
(i)Development of fundamental understanding and modelling of flame propagation in turbulent droplet-laden mixtures: The research outcomes will be disseminated through participation in international conferences (e.g. Int. Combust. Symp., Eur. Combust. Meeting, Numer. Combust. Conf. etc.) and publication in reputed scientific journals (e.g. Combust. Flame, Phys. Fluids, Combust. Sci. Tech., Combust. Theo. Modell. etc.). Moreover, the models developed during the course of this project will enhance the knowledge-base of turbulent reacting flows and predictive capability of engineering simulations, which in turn will play a key role in the design-cycle of next generation energy-efficient and environment friendly combustors. The DNS and experimental databases resulting from the proposed research programme will be made available to other interested researchers upon request. The Research Associates (RA) will manage a website for data-exchange and documentation, and important results will be made available for public download. A workshop on flame propagation in droplet-laden mixtures will be organised at the conclusion of the project to maximise the chances of technical dissemination, and to attract the attention of relevant industrial sectors.
(ii)IC-engine and gas turbine manufacturers: Improving the predictive abilities of flame propagation in droplet-laden mixtures will be of great benefit to these industries for the development of new generation energy-efficient and environment friendly combustors especially in the UK. Industrial colleagues will be invited to attend half-yearly progress meetings and the planned workshop so that they remain aware of the new research developments and their feedback will be taken on board during the course of the proposed research programme. A website will be maintained throughout the proposed work with information on data-exchange and documentation, and specific results will be made available for public download along with the latest findings in open literature. It will therefore serve as an important source of information for CFD practitioners both in academia and industry.
(iii) RAs who will be engaged in this research programme: In the proposed research programme, both RAs will learn advanced techniques for CFD simulations and experimental measurements which will 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 well-rounded researchers during the course of this research programme. Moreover, the RAs will need to present their work periodically in progress review meetings and maintain a project website, which will also be beneficial for them in terms of developing project management and presentation skills. These will also help them in developing a range of transferable skills such as communication, teamwork and project management. This, in turn, will give rise to development of highly-skilled technical personnel which will be essential for the UK's financial growth.
(iv) Research group at NU and CUED: The collaboration between NU and CUED is one of the major strengths of this project which will lead to broadening of research capabilities of all the investigators. Moreover it is expected that this project will give rise to open questions which form the basis of further investigations by the investigators, 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 UK industry in future, which will also ensure effective assimilation of this project's outcome in the relevant industrial sectors.