Study of Interacting Turbulent Flames Using Direct Numerical Simulation and Laser Diagnostics

Lead Research Organisation: University of Cambridge
Department Name: Engineering

Abstract

Emissions legislation is becoming ever more stringent and the conventional combustion technologies are incapable of meeting the low ppm levels set by the new legislation. Thus, alternative technologies need to be found and the lean burn concepts have the ability to meet the standards but the ignitability and flame stability of lean premixtures need to be understood clearly. However, lean premixed flames are prone to thermo--acoustic instabilities, because of their high sensitivity to even small scale variations in the fluid dynamic and thermo--chemical state of the mixture. It is becoming clear that interacting flames are a dominant mechanism for creating thermo--acoustic oscillations in lean premixed combustion. Premixed combustion is often more difficult to simulate than nonpremixed combustion, because of the propagation of reacting surfaces in premixtures, with the consequence that engineering models for turbulent premixed combustion are significantly less well developed than those for nonpremixed combustion. A major unsolved problem is to provide a satisfactory description of the small scale interactions between reacting surfaces, within a flame brush, which form the major mechanism for limiting the growth of reacting surface area. Because of this fundamental limitation, existing models are not well adapted to describe the large scale flame-flame interactions that give rise to pressure variations and thermo-acoustic instabilities in combustion chambers.In the present work, we propose to investigate the mutual interaction between flames at a fundamental level using direct numerical simulation and laser diagnostics. In the configuration of twin ``V'' flames considered here the interaction process is controlled by the upstream turbulence and yields a sufficiently long interaction time for statistical sampling in experiments. This geometry is akin to burner--to--burner interaction process inthe annular combustor of a gas turbine engine, and the interaction process to be simulated is considered to be a valid representation of behaviour in turbulent flames. The expected outcome from this work is a close understanding of processes occurring during interaction between flames, leading to development of a revised model for premixed turbulent combustion, containing a physically valid description of processes limiting growth of flame surface area, and with a capability to simulate large scale flame-flame interactions.
 
Description Different types of flame-flame interactions and frequency of their occurrence. These information, specifically the frequency, has be found for the first time.
Exploitation Route The knowledge gather can be translated into a mathematical model which can then be implemented in to existing or a new computer code to study sound emissions from flames.
Sectors Aerospace, Defence and Marine,Education,Energy,Transport

 
Description Yet to be used in relevant industries
First Year Of Impact 2014
Sector Aerospace, Defence and Marine,Education,Energy,Transport
Impact Types Economic

 
Description Rolls-Royce Plc
Amount £115,990 (GBP)
Funding ID NMZA/778 
Organisation Rolls Royce Group Plc 
Sector Private
Country United Kingdom
Start  
 
Description Rolls-Royce Plc
Amount £115,990 (GBP)
Funding ID NMZA/778 
Organisation Rolls Royce Group Plc 
Sector Private
Country United Kingdom
Start 05/2011 
End 12/2012
 
Title DNS of single and double oblique flames 
Description A collection of numerical data from high fidelity simulations of single and twin "Vee" flames. 
Type Of Material Database/Collection of data 
Year Produced 2014 
Provided To Others? Yes  
Impact Improved knowledge and understanding of flame-flame interaction, helping us to build better mathematical models for turbulent lean combustion. 
 
Title Models for interacting flames 
Description A mathematical model to explore the interactions of flamelets 
Type Of Material Computer model/algorithm 
Year Produced 2013 
Provided To Others? Yes  
Impact None yet 
 
Description Research Collaboration with TokyoTech 
Organisation Tokyo Institute of Technology
Department Furui-Lab
Country Japan 
Sector Academic/University 
PI Contribution Because of the initial collaboration with Tokyo Tech through this project, the PI has been invited to collaborate with TokyoTech on a number of research and educational projects. The PI has been invited to be a co-investigator on two research projects (2010-13, 2011-15) on turbulent combustion with a combined total value of about £2.7M, awarded to Tokyo Tech by JSPS and MEXT. The PI has been invited to be an international co-operative partner in their 6 year educational programme with a value of about £25M awarded to Tokyo Tech by MEXT. The initial interaction through this project has evolved into a strong and successful collaboration.
Collaborator Contribution The partner allowed us to use their numerical simulation data to get insights required for model development in this project
Impact the papers resulted from this collaboration are listed in the publication list.
Start Year 2006