A combined experimental and numerical investigation of premixed flame-wall interaction in turbulent boundary layers

The presence of walls alters the thermo-chemical and fluid-dynamical processes associated with turbulent premixed flames. The increasing demands for light-weight combustors make flame-wall interactions (FWI) inevitable, which influence the cooling load, thermal efficiency and pollutant emission in these applications. However, this aspect has not yet been sufficiently analysed in the existing turbulent reacting flow literature because of the challenge this poses for both experimental and numerical investigations in terms of spatial and temporal resolutions among others. Therefore, a thorough physical understanding of the FWI mechanism is necessary to develop and design more energy-efficient and environmentally-friendly combustion devices. In this project, recent advances of both high-performance computing and experimental techniques will be utilised to analyse and model premixed FWI in turbulent boundary layers (TBLs). The proposed analysis will consider different FWI configurations (based on the orientation of the mean flame normal with respect to the wall) in turbulent channel flows and unconfined boundary layers (BLs) using state-of-the-art experiments and high-fidelity Direct Numerical Simulations for different wall boundary conditions. Experiments will utilize a suite of advanced laser diagnostics, providing new simultaneous measurement capabilities. DNS will simulate the turbulent flow without any recourse to physical approximations. The fundamental physical insights obtained from DNS and experimental data will be used to develop a novel hybrid RANS/LES approach for device-scale simulation of FWI, building on expertise in the context of Flame Surface Density (FSD) and Scalar Dissipation Rate (SDR) closures for Reynolds Averaged Navier Stokes (RANS) and Large Eddy Simulations (LES). The newly-developed models will be implemented to carry out hybrid RANS/LES of experimental configurations for the purpose of model validation. The project will offer robust and cost-effective Computational Fluid Dynamics (CFD) design tools for fuel-efficient and low-emission combustion devices (e.g. gas turbines, micro-combustors and automotive engines).

The major impacts of this research endeavour are summarised as follows:

(i) Development of fundamental understanding and modelling of flame-wall interaction:

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 environmentally 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-wall interaction 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) Industrial combustion equipment manufacturers:

Improving the predictive abilities of flame-wall interaction 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 the 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, 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 UoE:

The collaboration between NU and UOE 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 research by the investigators, and the usefulness of the present project will be exploited to attract industrial and research grant funding for future follow-up projects. 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 the new knowledge gained.