RATE-CONTROLLED CONSTRAINED EQUILIBRIUM: A BASIS FOR EFFECTIVE COUPLING OF COMPREHENSIVE CHEMICAL KINETICS AND CFD
Lead Research Organisation:
Imperial College London
Department Name: Mechanical Engineering
Abstract
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Organisations
People |
ORCID iD |
| William Jones (Principal Investigator) |
Publications
Akridis P
(2016)
Modelling of soot formation in laminar diffusion flames using a comprehensive CFD-PBE model with detailed gas-phase chemistry
in Combustion Theory and Modelling
Akridis P
(2015)
Modelling of Soot Formation in a Laminar Coflow Non-premixed Flame with a Detailed CFD-Population Balance Model
in Procedia Engineering
Almeida Y
(2019)
Large Eddy Simulation of a supersonic lifted flame using the Eulerian stochastic fields method
in Proceedings of the Combustion Institute
Almeida Y
(2019)
Large Eddy Simulation of Supersonic Combustion Using the Eulerian Stochastic Fields Method
in Flow, Turbulence and Combustion
Alzwayi A
(2014)
Large eddy simulation of transition of free convection flow over an inclined upward facing heated plate
in International Communications in Heat and Mass Transfer
Brauner T
(2016)
LES of the Cambridge Stratified Swirl Burner using a Sub-grid pdf Approach
in Flow, Turbulence and Combustion
Bulat G
(2014)
NO and CO formation in an industrial gas-turbine combustion chamber using LES with the Eulerian sub-grid PDF method
in Combustion and Flame
Bulat G
(2015)
Large eddy simulations of isothermal confined swirling flow in an industrial gas-turbine
in International Journal of Heat and Fluid Flow
Dodoulas I
(2015)
Analysis of extinction in a non-premixed turbulent flame using large eddy simulation and the chemical explosion mode analysis
in Combustion Theory and Modelling
| Description | Modelling of combustion processes is an outstanding technical problem with wide implications, both scientific and practical. In excess of 90% of our energy is produced via the combustion of hydrocarbon fuels in such equipment as internal combustion engines for cars, gas-turbine engines for aircraft, industrial gas-turbines for power generation and furnaces for cement production and electrical power generation, a situation that is likely to prevail for the foreseeable future. Combustion processes also account for the generation of a wide variety of pollutants, such as oxides of Nitrogen and soot, as well as for the generation of greenhouse gases. It is widely acknowledged that there is large potential for the improvement of combustion processes, resulting in great environmental benefits. Mathematical modelling of Combustion requires coupling of equations describing fluid motion together with a comprehensive description of chemical reaction, with the resulting system of partial differential equations being solved numerically with a Computational Fluid Dynamics (CFD) package. Combustion processes are invariably turbulent, and their prediction requires a turbulence-chemistry interaction model. Coupling all of these elements results in a formidable computational problem, in which the main cause of the bottleneck is the chemical kinetics part of the calculation, where a very large numbers of species and reactions are involved, each species requiring an extra differential equation to be solved. This project has resulted in significant steps towards the renationalisation of the long-term aim of developing a methodology for computer modelling of reactive flows and pollutant production in realistic turbulent flow conditions. Central to this methodology is the concept of Rate-Controlled Constrained Equilibrium (RCCE) for deriving the low-dimensional models on the basis of time-scale separation. RCCE allows us to describe combustion using a model that, although derived from a comprehensive and detailed chemical mechanism, consists of much fewer variables. An important parameter in RCCE is the choice of the reduced variables, and for this reason we explored the potential of a synergy between RCCE and Computational Singular Perturbation (CSP) - a method for investigating the time scales associated with various chemical species and determining which ones should be retained in the RCCE-derived reduced mechanism. The concept proved fruitful, and good results were obtained for the simulation of laminar premixed flames, an ideal test case to prove the value of the concept. Even the reduced model requires a significant amount of time to be integrated, however, and for this purpose we developed an approach based on Artificial Neural Networks (ANNs) for replacing the real-time integration of the RCCE differential equations with an algebraic model, trained with results from model computations. The development of a methodology for generating training sets for ANNs and the generation and training of them in an appropriate way for predicting the conditions encountered in turbulent flames was a major outcome of the project. The ANN approach was tested and excellent results were obtained. The method has been incorporated into a Combustion Large Eddy Simulation method utilizing a state-of-the-art stochastic fields method for describing sub-grid scale turbulence-chemistry interactions. This was a collaborative project involving Imperial College, EP/G05679X/1 and Manchester University, Dr S Rigopoulos, EP/G057311/1. Dr Rigopoulos subsequently moved to Imperial College, EP/G057311/2 |
| Exploitation Route | Combustion Large Eddy Simulation based on the sub-grid probability equation/stochastic fields method is currently being used by several European gas turbine manufacturers and there is a strong need for accurate and detailed, but simplified chemistry. The research on RCCE provides a means of incorporating this. The method is also of potential value to the manufacturers of reciprocating engines and furnaces. An important long-term aspiration of the Combustion industry is to be able to predict, at the design stage, the performance and reliability of new combustion chambers, the achievement of which is likely to lead to appreciable improvements in design. The practical benefits this would bring are large and include reduction of carbon dioxide emissions released to the environment, significant reductions in costs for many industries, such as those involved in transport, power generation and chemical processing, because of their ability to meet emission targets and reduce their Carbon Tax liability and more economical manufacturing through elimination of over-design. The life cycle cost analysis and reliability and availability of power plants is becoming a key issue in the quest for a sustainable global environment. Currently the design of combustors is carried out essentially by empirical means usually followed by extensive experimental testing and the ability of computer models to assist the design is limited. Although, computer based simulation methods are an integral part of the design approach for other parts of power plants (e.g. turbines, compressors, heat exchangers etc.), their inability to predict combusting flows has not allowed a similar confidence to be developed in this area. A major reason for this has been related to an inability to provide a sufficiently detailed description of chemical reaction. The research conducted has provided a means of overcoming this difficulty and thus allows the development of accurate and reliable simulation methods to be used as an important aid to the design of efficient and low emissions combustion systems. |
| Sectors | Aerospace, Defence and Marine,Energy,Transport |
| Description | Clear Skies: Dreamcode |
| Amount | £250,000 (GBP) |
| Funding ID | SP1-JTI-CS-2013-01-620143 |
| Organisation | European Commission |
| Sector | Public |
| Country | European Union (EU) |
| Start | 10/2013 |
| End | 09/2017 |
| Description | Clear Skies: Dreamcode |
| Amount | £250,000 (GBP) |
| Funding ID | SP1-JTI-CS-2013-01-620143 |
| Organisation | European Commission |
| Sector | Public |
| Country | European Union (EU) |
| Start | 11/2014 |
| End | 11/2016 |
| Description | LES of industrial gas turbines |
| Amount | £200,000 (GBP) |
| Organisation | Siemens AG |
| Department | Siemens Industrial Turbomachinery Ltd |
| Sector | Private |
| Country | United Kingdom |
| Start | 11/2011 |
| End | 10/2015 |
| Description | LES of industrial gas turbines |
| Amount | £200,000 (GBP) |
| Organisation | Siemens AG |
| Sector | Private |
| Country | Germany |
| Start | 11/2011 |
| End | 10/2015 |