Numerical exploration and modelling of novel environmentally friendly combustion technique: droplet-laden MILD combustion

Lead Research Organisation: Newcastle University
Department Name: Sch of Engineering

Abstract

A small reduction in NOx emission per kilo-watt of generated power will have a significant reduction in environmental impact of combustion used for power generation. The MILD (Moderate or Intense Low-Oxygen Dilution) combustion technique offers an opportunity to drastically reduce emissions while improving thermal efficiency of furnaces and boil-ers. In gas turbines, though overall fuel-air mixture is fuel-lean and MILD combustion is not directly applicable, fuel-rich regions in the primary zone of the combustor exhibit localised MILD regimes, particularly for liquid fuel operation How-ever, the physical and chemical intricacies of this novel technique are not well understood and thus identifying key con-trol parameters for using this technique for power generation and industrial processes over wide range of conditions is challenging. This project aims to provide a step change in physical understanding and modelling of this combustion technique and to identify key control parameters. The aim is to investigate MILD combustion of high calorific value gaseous and liquid fuels for practical application using Direct Numerical Simulations (DNS) and Large Eddy Simula-tions (LES), with high-fidelity mathematical description for physical and chemical processes involved. The droplets of liquid fuel spray will be tracked using the Lagrangian approach while the gas phase is treated using the Eulerian ap-proach for the simulations.
The effects of droplet diameter, equivalence ratio (both for gaseous and liquid fuels), extent of dilution by combustion products, volatility (by considering different fuels), turbulence intensity and its length scale on the burning rate, flame structure (in terms of chemical reaction pathways analysis and flame and flow topologies) and pollutants formation will be analysed based on a judicious parametric analysis based on three-dimensional detailed chemistry DNS data. In this project, the fundamental physical understanding extracted from DNS data will be utilised to develop high-fidelity models for engineering Computational Fluid Dynamics (CFD)-based simulations to identify key control parameters using LES after validating these models against the available experimental results. This project will provide (1) a ro-bust modelling framework for MILD combustion technique, which would be a cost-effective reliable tool for designing energy-efficient and clean gas turbines and industrial furnaces and (2) the key control parameters identified can help to design retro-fit "greener" combustion systems.

Planned Impact

The major impacts of this research endeavour are summarised as follows:
(i) Development of fundamental understanding and modelling of turbulent droplet-laden MILD combustion:
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. Technol., Combust. Theor. 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 LES 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 MILD combustion 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 MILD combustion of droplet-laden mixtures will be of great benefit to these industries for the development of new generation energy-efficient and environment friendly combustors. Industrial colleagues will be invited to attend half-yearly progress meetings and the planned workshop so that they remain aware of the development of the proposed research programme 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 an edge to the RAs in current competitive job market.
(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 (i.e. both PIs and CI). 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 industry in future, which will also ensure effective assimilation of this project's outcome in the relevant industrial sectors.
 
Description A small reduction in NOx emission per kilo-watt of generated power will have a significant reduction in environmental impact of combustion used for power generation. The MILD (Moderate or Intense Low-Oxygen Dilution) combustion technique offers an opportunity to drastically reduce emissions while improving thermal efficiency of furnaces and boilers. In gas turbines, though overall fuel-air mixture is fuel-lean and MILD combustion is not directly applicable, fuel-rich regions in the primary zone of the combustor exhibit localised MILD regimes, particularly for liquid fuel operation How-ever, the physical and chemical intricacies of this novel technique are not well understood and thus identifying key control parameters for using this technique for power generation and industrial processes over wide range of conditions is challenging. This project aims to provide a step change in physical understanding and modelling of this combustion technique and to identify key control parameters. The aim is to investigate MILD combustion of high calorific value gaseous and liquid fuels for practical application using Direct Numerical Simulations (DNS) , with high-fidelity mathematical description for physical and chemical processes involved. The droplets of liquid fuel spray will be tracked using the Lagrangian approach while the gas phase is treated using the Eulerian approach for the simulations.
The effects of droplet diameter, equivalence ratio (both for gaseous and liquid fuels), extent of dilution by combustion products, volatility (by considering different fuels), turbulence intensity and its length scale on the burning rate, flame structure (in terms of chemical reaction pathways analysis and flame and flow topologies) and pollutants formation will be analysed based on a judicious parametric analysis based on three-dimensional detailed chemistry DNS data. In this project, the fundamental physical understanding extracted from DNS data will be utilised to develop high-fidelity models for engineering Computational Fluid Dynamics (CFD)-based simulations to identify key control parameters using LES after validating these models against the available experimental results. This project will provide (1) a robust modelling framework for MILD combustion technique, which would be a cost-effective reliable tool for designing energy-efficient and clean gas turbines and industrial furnaces and (2) the key control parameters identified can help to design retro-fit "greener" combustion systems. The DNS code is currently functional and production level simulations are currently under way. We are in the process of obtaining fundamental physical insights into the MILD combustion process which will be used for the development of high-fidelity models.
Exploitation Route (i) Development of fundamental understanding and modelling of turbulent droplet-laden MILD combustion: 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. Technol., Combust. Theor. 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 LES 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 MILD combustion 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 MILD combustion of droplet-laden mixtures will be of great benefit to these industries for the development of new generation energy-efficient and environment friendly combustors. Industrial colleagues will be invited to attend half-yearly progress meetings and the planned workshop so that they remain aware of the development of the proposed research programme 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 an edge to the RAs in current competitive job market.
(iv) Research group: The collaboration between Newcastle University and Cambridge University is one of the major strengths of this project which will lead to broadening of research capabilities of all the investigators (i.e. both PIs). 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 industry in future, which will also ensure effective assimilation of this project's outcome in the relevant industrial sectors.
Sectors Aerospace

Defence and Marine

Energy

Environment

 
Description Impact through communication and engagement of beneficiaries: The design-cycle of modern gas turbine and industrial furnaces depends heavily on the accurate predictive capability of engineering Computational Fluid Dynamics (CFD) calculations. The fundamental physical insight and the high-fidelity methodology for analysing turbulent MILD combustion, which has been developed in this project, will have maximum benefit for the manufacturers of new generation gas turbines and industrial furnaces, who are engaged in developing new low-pollution and high-efficiency combustion devices. In the UK, EDF and Renuda, are interested in the outcome of this work, though the benefits are not limited to the UK (e.g. GE) as important findings have already been disseminated through peer-reviewed journals and international conference publications. Furthermore, the participating institutions (CUED and NU) have obtained new tools for the analysis of turbulent reacting flows, helping the PIs to attract industrial funding. Finally, the CFD software community, who use state-of-the-art combustion models extensively, are also interested in this work. In order to maximise the impact of the project, the PIs and RAs worked actively to publicise the results by attending reputed international conferences (e.g. International Combustion Symposium, European Combustion Meeting) and important UK combustion meetings organised by the British Section of Combustion Institute (BS-CI), UK Consortium on Turbulent Reacting Flows (UKCTRF), Combustion Science and Technology Special Interests Group (SIG) of the UK-Fluids Network and Institute of Physics. Given the long-term nature of the design-cycle of gas turbines and industrial furnaces, and the time required to build up enough confidence in the community, it is likely that the impact in terms of new product and wealth creation will be felt in a time scale of 10-20 years after the completion of the project. The technological advancements of this project will also help in designing energy efficient and environment friendly combustors, which will also bring long-term benefits (in a time scale of 10-20 years) for society. The impact of this project in terms of proving a competent CFD software tool is likely to be felt in about 5-10 years' time after the completion of the project. The PIs have existing collaborations with several international research laboratories (e.g. Kyoto University, Kyushu University, Tokyo Institute of Technology, Sandia National Laboratory, University of Sydney, Bergen University, ETH-Zurich, University of Duisburg, University of Bundeswehr Munich, etc.) and the results of this project have been publicised during mutual research visits. The simulation database resulting from the project will also be made available to other interested researchers upon request. Impact through collaboration: The collaboration between CUED and NU on complementary aspects and skill sets is one of the major strengths of this project. On completion of this project, the PIs have DNS and LES databases which can be used for further analyses. This will lead to the broadening of research capabilities of the PIs. Moreover, academic and industrial contacts will be shared by the PIs during the project period, which will be beneficial to disseminate research outcomes in both academia and industry. The collaboration with research groups will add new dimensions to the academic developments of the RAs who worked in this project. They had opportunities to interact with experts from both academia and industrial sectors, which immensely helped their academic development, and provided a range of transferable skills such as communication, teamwork and project management. This, in turn, gave an edge to the RAs in the current competitive job market. Furthermore, the RAs presented their work periodically in progress review meetings, annual meetings of UKCTRF, Combustion and Science and Technology SIG meetings, which was beneficial in developing their project management and presentation skills. The project outcomes were disseminated through participation in international academic conferences (e.g. Int. Comb. Symp., Eur. Comb. Meeting) and publication in reputed scientific journals (e.g. Comb. Flame, Flow, Turb. Combust. etc.). Much of the benefit of the modelling activity will not only be limited to turbulent MILD combustion, but also contribute to the modelling of turbulent reacting flows in general. This project will provide information on the validity of Partially Stirred Reactors (PaSR), flamelets (e.g. Flame Surface Density and Scalar Dissipation Rate), Conditional Moment Closure (CMC) and Probability Density Function (PDF) modelling methodologies in the case of MILD combustion in droplet-laden mixtures. The high fidelity and robust models to be developed in this project will lead to improved prediction from CFD simulations, which can help in the economical design of gas turbines and industrial furnaces for better efficiency and environment friendliness. This suggests that the findings of this research endeavour are of particular interest to industrial process heating and gas turbine sectors of the industry (e.g. EDF,GE and Renuda, to name a few). This is especially important as the world-wide demand for natural oil would increase by 45% by 2030 and thus improved physical understanding and modelling methodology for turbulent MILD combustion are not only timely but also essential for addressing the challenges of energy-efficiency and pollution control. Given the fundamental nature of this project, the proposed investigation has given rise to some open questions, which will then form the basis for further investigations by the applicants. The useful outcomes of this project are expected to attract funding from industries and other sources for future follow-ups. Impact through capability development and knowledge exchange: The proposed project is based on the collaboration between two research groups, which ensured an extensive knowledge exchange between PIs and the RAs working in this project. This project not only provided opportunities to broaden the investigators' research horizon but will also be highly valuable for the RAs for their academic and career development. The RAs also received extensive training on a variety of topics such as advanced high-performance computing techniques, fluid turbulence, chemical kinetics and combustion model development. They also learnt advanced techniques for high performance computing, which improved their analytical and mathematical skills. The regular presentations in various meetings (e.g. annual progress meetings, annual meetings of UKCTRF, Combustion and Science and Technology SIG meetings), managing the project website and close interaction between several research groups also improved the presentation and communication skills of the RAs. This project laid substantial emphasis on the transferable skills of the RAs and increased the chances of their employability. As a result, this project gave rise to the development of two well-rounded researchers who will eventually carry the expertise gained during this project period in their future roles irrespective of academic or industrial nature. It was noted earlier that project outcomes will be presented in front of various academic and industrial colleagues at different stages of the project to disseminate its findings to the maximum extent, which will ensure knowledge exchange from participating institutions to interested parties in the industrial sector. Moreover, the expertise generated in this project will also be helpful in expanding PIs' research groups in their respective institutions. The impact through capability development will be felt immediately through the RAs (in a timescale of 2-4 years), and the expertise developed in the project is likely to bring long term benefits to the investigators and their respective institutions in terms of future funding and expansion of the respective research groups.
First Year Of Impact 2023
Sector Aerospace, Defence and Marine,Energy,Environment
Impact Types Societal