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

Lead Research Organisation: University of Cambridge
Department Name: 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.

Publications

10 25 50
 
Description Not yet since this grant started only in Sep. 2019
Exploitation Route yet to be evaluated
Sectors Aerospace, Defence and Marine,Energy,Environment,Transport

 
Description none yet - since the grant is still active and started only in Sep. 2019
 
Title new skeletal mechanism for n-heptane MILD combustion 
Description A chemical kinetic mechanism describing the combustion of n-hetane liquid fuel under MILD condition is developed using a well established computer code/methdology called CARM which used steady state and partial equilibrium approximations for species and reactions with fast time scales. The mechanism developed is suitable for high fidelity simulations of turbulent combustion of practical interest. A manuscript describing the methodology, the mechanism and results are published (under review in journal Combustion and Flame) and thus this information will become available to others. 
Type Of Material Technology assay or reagent 
Year Produced 2021 
Provided To Others? Yes  
Impact An accurate description of chemical kinetics for n-heptable combustion in turbulent flows with large diluent species and this condition is of interest for next generation of combustion systems. 
 
Description Berkeley - JYChen 
Organisation University of California, Berkeley
Country United States 
Sector Academic/University 
PI Contribution Joint research work to develop chemical kinetics mechanism for combustion of n-heptane under MILD conditions. The identification and conceptualization of this work was proposed by my research team.
Collaborator Contribution Executing those tasks through a computer programme available with Prof. J.Y. Chen at UC Berkeley leading a a development a new chemical kinetic mechanism.
Impact A paper is submitted to high impact journal - Combustion and Flame. The manuscript is under peer review.
Start Year 2020
 
Description Norway - Trondheim 
Organisation Norwegian University of Science and Technology (NTNU)
Country Norway 
Sector Academic/University 
PI Contribution Hosted and trained a PhD student from NTNU, Department of Department of Energy and Process Engineering. We developed the research idea conceptualization for joint work.
Collaborator Contribution The research student worked with the researcher employed on this project to execute the required scientific tasks.
Impact A paper is written and published in Proceedings of Combustion Institute based on this joint work. This paper is available at https://doi.org/10.1016/j.proci.2020.06.298
Start Year 2019
 
Description ULB - collaborations 
Organisation University Libre Bruxelles (Université Libre de Bruxelles ULB)
Country Belgium 
Sector Academic/University 
PI Contribution A highly efficient modelling approach is developed to explore a novel combustion concept, which is investigated experimentally at ULB.
Collaborator Contribution Providing experimental data and machine learning algorithms to develop Machine Learning Approach for MILD combustion
Impact None yet
Start Year 2018