Sustainable Combustion


Laminar pulsating flame jet

Topics of Interest

For the past fifteen years, the Fluid Mechanics Group has been involved in research activities related to reactive flows of technological applicability. Many different problems have been investigated, often in close collaboration with the groups of Amable Liñán (ETSI Aeronáuticos, Madrid) and Forman Williams (Dept. of Mechanical and Applied Engineering, UCSD). Some of the problems addressed in the past include:

Efficient combustion of biofuels with application to portable power generation

Spanish MINECO
Duration: 2016-2019
Contract # ENE2015-65852-C2-1-R
PI: Mario Sánchez Sanz, Eduardo Fernandez Tarrazo

Other Participants: Antonio L. Sánchez, Carlos Fernández-Pello, Daniel Murphy

The aim of this project is contributing to the global objective imposed by the European Union to reduce CO2 emissions by using renewable fuels and improving the efficiency of energy conversion systems. To do so, we will study in detail the combustion of gaseous (biomethane) and liquid (ethanol, methanol and blends) biofuels in portable power devices to assess and recommend designs that improve the global energy conversion process that takes place within engines, small combustors and newly created widgets (drones, wearables...). This project, Efficient combustion of biofuels with application to portable power (℮-BIOCOMB), aims to contribute through a collaborative research between Carlos III and CIEMAT in the following themes: 

  • Development and implementation of accurate, multipurpose, reduced combustion chemistries (RCC)
  • Fundamental efficiency-related aspects of biofuel combustion
  • Experimental and numerical analyses of confined flames.

Propane flame

Development and implementation of RCC: Biofuels are liquid or gaseous fuels derived from biomass or waste. Unlike conventional fuels, they are considered as CO2-neutral fuels and they are considered as one of the most strategically important sustainable fuel sources. Their use in design and modeling has been hampered by the difficulty of implementing detailed combustion chemistry models, of the order of hundreds of species and reactions, in computational codes. To facilitate the use of the biofuels, we will develop short, accurate combustion chemistries of easy implementation in the computational codes of designers and researchers. 

Fundamental aspects of biofuels combustion: In this task we intend to assess the use of liquid biofuels in portable power generation. For full scale engines (with a size of the order of a car engine) biofuels have been used successfully in the past. Unfortunately, as the size of the device is diminished, so does its performance as a consequence of an increase in heat losses, shorter residence times, large emissions of noise and pollutants and the size of the fuel and air delivery systems. The availability of liquid biofuels will contribute to reduce the size of the delivery system but to achieve better efficiency it is required an extensive research to reduce the effect of heat losses and the emissions of noise and pollutants. With that objective in mind, we will tackle these specific problems of small device combustion by studying, in detail, the flame structure, ignition, extinction and stability properties of specific biofuel flames, using the reduced chemistries developed within this project, in geometries that mimic the conditions found in portable power devices. 

Experimental and numerical analyses of confined flames: The difficulty to carry out experiments in small combustion devices and the lack of numerical and theoretical models has led designers to build portable power devices by trial and error. We intend to cover that gap by designing, building and experimenting with simplified configurations to acquire a knowledge that should contribute to improve future designs. Technologically-relevant magnitudes will be determined in confined combustion chambers under variable conditions of temperature, composition and size of the combustion chamber that are typical of engines working under stable conditions. The Reduced Combustion Chemistries developed in previous tasks will be numerically tested in a 3D geometry that mimics the experimental setup.  

Key words:  Portable power, alternative fuels, clean energy, biofuels, reduced chemistry, efficiency    

Sustainable Combustion Research (SCORE)
Funding Agency: Spanish MICINN
Duration: 2011-2015
Contract # CSD2010-00011 (Consolider-Ingenio 2010)
PI: Antonio L. Sánchez


This Project, Sustainable COmbustion REsearch (SCORE), aims at contributing through a systematic collaboration to the development of advanced and sustainable combustion systems via the use and improvement of predictive tools, experimental techniques, as well as measurement methods and control. SCORE integrates six internationally known research groups with complementary skills on theory, computation and experimental work. The proposed Work-Packages, and the corresponding Tasks configure well coordinated activities, where the integration of the different participating teams adds a very important value to their collaboration. The technological themes that are being addressed are:

  1. Coal/oxygen/CO2 combustion: Oxy-fuel combustion is a technique to obtain effluent streams with a very high CO2 concentration, which can be directly compressed and stored. At present, oxy-fuel combustion is at the demonstration stage. However, coal flame stability and combustion control in a stream of recirculated gases (FGR) and oxygen, the effects of high CO2 concentrations upon steady combustion, and of SO2 on materials corrosion of heat exchangers surface walls, as well as the difficulties resulting from slugging and fouling, are, among others, problems to be investigated in depth in order to provide scientific and technical support to large scale demonstration projects.
  2. Hydrogen and hydrogen/syn-gas gas turbine combustors: Hydrogen can be generated from coal, biomass or organic waste gasification processes, or, via electrolysis, using the electricity surplus, not manageable in the grid, produced by renewable energies. Due to its high difussivity, large reactivity and low molecular weight, hydrogen possesses limits of flame stability, autoignition, flash-back, flame anchoring, propagation of combustion fronts and of triple flames, which are substantially different from those of hydrocarbon combustion. The technologically-relevant magnitudes will be determined under pressure, temperature and composition conditions typical of gas-turbine combustion-chambers in stable operation. Chemical kinetics and transport basic mechanisms for both premixed and non-premixed combustions will be investigated, for a complete range of flammability conditions, aiming at the development of simple reduced mechanisms. These models will be coupled to direct numerical simulation (DNS) codes; they will also be integrated together with turbulent transport andmicro-mixing models in large eddy simulation (LES) and Reynolds averaged Navier-Stokes (RANS) approaches. A new gas turbine model combustor, operating both at atmospheric and at higher pressures, will be designed, built and run. Measurements will be made through a combination of conventional and advanced (PIV, PLIF) techniques.
  3. Biomass combustion and co-combustion with coal or waste: The life cycle assessment of biomass, integrating its combustion directly or after its previous gasification, yields a CO2 zero-emissions balance. The coal-biomass co-combustion contributes to emissions reductions. The
    main technological challenges in this fields are related to the development of particle combustion models adapted to biomasses (millimeter-sized, very high volatiles), the optimal design of combustion and co-firing applications and the problems associated with the inorganic matter (formation of fine aerosols, ash deposition, corrosion). All these issues will be addressed in the project, using and improving different modeling and test methods specifically conceived for the study of biomass combustion.

Ongoing Research Projects

Fundamental combustion research in ultra-compact rotary engines
Spanish MICINN
Duration: 2013-2016
Contract # ENE2012-33213
PI: Mario Sánchez Sanz

Laminar pulsating flame jet

This project focuses on the modelization of the combustion chamber of a rotary, ultra-compact Wankel engine with characteristic size of the order of the flame thickness. We propose a fundamental study of the combustion inside a small device with large velocity gradient, with the objective of improving the
efficiencies obtained in present experimental developments.
The large gravimetric and volumetric energy density of liquid fossil fuels and the high efficiencies obtained in large-scale power systems, encourages the development of miniaturized power-generation devices using combustion. These small devices could be considered as an alternative to batteries as a portable energy supplier if the efficiency of the process reaches values close to 2-3 %.
In this framework, the rotary engine emerges as a perfect candidate due to its large power/weight ratio. Even though it is possible to find in the literature examples of such engines with rotor diameters around 10 mm, their efficiencies are around 0.2%, still far from the viability threshold. The reduction from the macro to the mini or micro scale of these engines introduces changes in the combustion process that should be addressed from a fundamental point of view. The conclusions derived
from that analysis should be used as design recommendations towards the obtaining of better efficiencies.
The previous analysis of the systems has identified the competition between processes that takes place at three different characteristic times: fuel ignition time, residence time and time needed to burn completely the combustible mixture enclosed in the combustion chamber.
This project aims at investigating the variables that affect every of the above-described characteristic times.The relationship between them will determine the volume of unburned hydrocarbons in the combustion chamber which, in turn, will affect directly the efficiency and the engine output power. Preliminary analysis suggests a limit in the engine velocity above which the combustion stage cannot be
successfully completed.

  • M. Sánchez-Sanz, D Fernández-Galisteo, VN Kurdyumov, “ Effect of the equivalence ratio, Damköhler number, Lewis number and heat release on the stability of laminar premixed flames in microchannels”, Combustion and Flame, Volume 161, Issue 5, May 2014, Pages 1282–1293.PDF
  • D. Fernández-Galisteo, C. Jiménez, V. N. Kurdyumov, M. Sánchez-Sanz “The differential diffusion effect of the intermediate species on the stability of premixed flames propagating in microchannels”, Combustion Theory and Modelling, In press, 2014
  • M. Sánchez-Sanz, D. Murphy, C. Fernández-Pello, “Effect of an external electric field on the propagation velocity of a premixed flame.”, Proceedings of the Combustion Institute, In press 2014
Development of predictive tools for hydrogen and syngas combustion in gas-turbine conditions
Funding Agency: Madrid Regional Government
Duration: 2010-2013
Contract # P2009/ENE-1597
PI: Antonio L. Sánchez

This project is a coordinated effort of five different research groups with complementary expertise that aims at contributing to the development of numerical predictive tools for the design of reliable low-emission combustors in advanced gas turbines using hydrogen and syngas as fuels.  Chemical kinetic and transport mechanisms for premixed and nonpremixed combustion within the whole range of flammable conditions will be investigated, the ultimate objective being the development of simple reduced mechanisms to be implemented in numerical codes. Modelling issues concerning the subgrid description of hydrogen turbulent combustion will also be addressed, leading to the development of improved numerical codes. Predictions will be validated by comparisons with experiments. A combustion chamber will be built to operate at atmospheric and high pressures. Local gas velocities and flame displacements will be monitored under controlled conditions by the combined use of PIV (Particle Image Velocimetry) and OH PLIF (Planar Induced Fluorescence of OH radicals). The active participation of two leading engineering companies will enable the use of the increased knowledge and improved numerical tools generated within the project in future gas-turbine designs.

MyPlanet: Massively Parallel Computations of Combustion and Emission Simulations
Funding Agency: European Commission
Duration: 2008-2012
Contract # PITN-GA-2008-210781
PI: Immaculada Iglesias

The MYPLANET collaborative project is one of the first Marie Curie Initial Training Networks (ITN) funded by the European Commission within the 7th Framework Programme. MYPLANET represents a European initiative to train a new generation of engineers in the field of high performance computing applied to the numerical combustion simulation, energy conversion processes and related atmospheric pollution issues. The consortium is composed of 12 high-level partners of four different sectors and 7 different countries covering large parts of Europe; 7 partners contribute to MYPLANET as network contractors (beneficiaries), while Allinea, ALSTOM, Rolls Royce, Turbomeca and the Czestochowa University of Technology act as associated partners.

The project is based on the recognised lack on European level of highly skilled engineers that are equally well-trained in both combustion technologies and high-performance computing (HPC) techniques. The project will contribute to the structuring of existing high-quality initial research training capacities in fluid mechanics and the HPC field through combining both public and private (industrial) sectors.  The research is motivated by the fact that in today's industrial society more than 80% of the energy consumed on Earth is produced by burning fossil fuels, i.e. through combustion. It is widely recognised that important technological progress is required in order to optimize these combustion processes in the context of growing pollution, fuel depletion and global Earth warming. The computer simulation of combustion appears as a prerequisite to a better understanding of the underlying physical and chemical processes.  The main objective is to develop an ambitious training programme in the field of high-performance computations of reacting flows on massively parallel machines. Through the training actions they will learn both the fundamental physics behind combustion processes as well as software implementation aspects of high-performance computing as a prerequisite to the numerical simulation of reacting flows. Such training is necessary for developing future energy- and carbon-efficient devices based on biofuels. Thanks to the industrial partners involved in the project, the trainees will experience the industrial use of these new simulation tools while industry will obtain a first-hand experience with new methodologies.

Fundamental Aspects of Hydrogen Combustion
Funding Agency: Spanish MICINN
Duration: 2009-2011
Contract # ENE2008-06515-C04-01
PI: Antonio L. Sánchez

The design of advanced combustors for hydrogen and hydrogen-containing fuel mixtures requires a deeper knowledge of the associated combustion processes, including the underlying reduced kinetic account that describe the combustion within the whole range of flammable conditions, flame stability, structure and dynamics of flame balls, ignition processes and flame propagation, flash-back, effects of stretch, flame anchoring, triple-flame propagation and turbulent nonpremixed autoignition. Because of its unique characteristics (high diffusivity, high reactivity, low molecular weight), these flame phenomena are poorly understood in the case of hydrogen. This project is a coordinated effort of four research groups, with complementary expertise, that aims at advancing our knowledge of hydrogen combustion by combining numerical integrations with theoretical and experimental analyses. Quantities of practical interest, such as critical conditions for ignition and for flame anchoring, front propagation velocities and flame stability limits will be computed as part of the project for the conditions of pressure, preheat and composition typical of practical applications.

Recent Publications

Hydrogen Combustion
  • A. L. Sánchez, I. Iglesias, A. Liñán, An Asymptotic Analysis of Chain-Branching Ignition in the Laminar Wake of a Splitter Plate Separating Streams of Hydrogen and Oxygen, Combustion Theory and Modeling, 2, 259–271 (1998)
  • G. del Alamo, F. A. Williams, A. L. Sánchez, Hydrogen-Oxygen Induction Times Above Crossover Temperaturas Combust. Sci. Tech., 176 1599-1626 (2004)
  • D. Fernández-Galisteo, A. L. Sánchez, A. Liñán, F. A. Williams, The hydrogen-air burning rate near the lean flammability limit Combust. Theory Modelling, 13 741–761 (2009)
  • D. Fernández-Tarrazo, A. L. Sánchez, A. Liñán, F. A. Williams, The structure of lean hydrogen-air flame balls, Proc. Combust. Institute, 33 1203–1210 (2011)
  • A. L. Sánchez, A. Liñán, F. A. Williams, Chain-Branching Explosions in Mixing Layers, SIAM J. Appl. Math., 59, 1335–1355 (1999)
  • L. L. Bonilla, A. L. Sánchez, M. Carretero, The Description of Homogeneous Branched-Chain Explosions with Slow Radical Recombination by Self-Adjusting Time Scales, SIAM J. Appl. Math., 61, 528–550 (2000)
  • J. D. Mellado, A. L. Sánchez, J. S. Kim, A. Liñán, Branched-Chain Ignition in Strained Mixing Layers, Combust. Theory Modelling, 4, 265–288 (2000)
  • V. Kurdyumov, J. Blasco, A. L. Sánchez, A. Liñan, On the Calculation of the Minimum Ignition Energy, Combust. Flame, 136, 394–397 (2004)
Chemical Kinetics
  • M. Bollig, A. Liñán, A. L. Sánchez, F. A. Williams, A Simplified Approach to the Numerical Description of Methane-Air Difusión Flames, Proceedings of the Combustion Institute, 27, 595–603 (1998)
  • A. L. Sánchez, A. Lépinette, M. Bollig, A. Liñán, B. Lázaro The Reduced Kinetic Description of Lean Premixed Combustión, Combust. Flame, 123, 436–464 (2000)
  • A. Lépinette, A. Liñan, B. Lázaro y A. L. Sánchez, Reduced Kinetics and Coupling Functions for Calculating CO and NO Emissions in Gas-Turbine Combustión, Combust. Sci. Tech., 177 907 - 931 (2005)
  • E. Fernández-Tarrazo, A. L. Sánchez, A. Liñan, F. A. Williams, A Simple One-Step Chemistry Model for Partially Premixed Hydrocarbon Combustión, Combust. Flame, 147 32–38 (2006)
  • D. Fernández-Galisteo, A. L. Sánchez, A. Liñán, F. A. Williams, One-step reduced kinetics for lean hydrogen-air deflagration Combust. Flame, 156 985–996 (2009)
  • P. Boivin, C. Jiménez, A. L. Sánchez, F. A. Williams, An explicit reduced mechanism for H2-air combustion, Proc. Combust. Institute, 33 517–523 (2011)
  • P. Boivin, C. Jiménez, A. L. Sánchez, F. A. Williams, A four-step reduced mechanism for syngas combustion, Combust. Flame, in press (2011)
Compressibility Effects in Reacting Flows
  • A. L. Sánchez, M. Carretero, P. Clavin, F. A. Williams, One-Dimensional Overdriven Detonations with Branched-Chain Kinetics, Phys. Fluids, 13, 776–792 (2001)
  • A. L. Sánchez, J. L. Jiménez-Alvarez, A. Liñan, The Coupling of Motion and Conductive Heating of a Gas by Localized Energy Sources, SIAM J. Appl. Math., 63, 937–961 (2003)
  • V. Kurdyumov, A. L. Sánchez, A. Liñan, Heat Propagation from a Concentrated External Energy Source in a Gas J. Fluid Mec., 491, 379–410 (2003)
Flame Stabilization and Flame Propagation
  • E. Fernández-Tarrazo, V. Kurdyumov, A. Liñán, Diffusion Flame Attachment and Lift-Off in the Near Wake of a Fuel Inyector, Proc. Comb. Inst. , 28, 2125-2131 (2000)
  • V. Kurdyumov, E. Fernández-Tarrazo, A. Liñán, Flame Flashback and Propagation of Premixed Flames Near a Wall Proc. Comb. Inst. , 28, 1883-1889 (2000)
  • V. Kurdyumov, E. Fernández-Tarrazo, Lewis number effect on the propagation of premixed flames in narrow open Ducts, Combust. Flame, 128, 382-394 (2001)
  • A. Revuelta, A. L. Sánchez, y A. Liñán, Laminar Mixing in Diluted and Undiluted Fuel Jets Upstream from Lifted Flames, Combust. Flame, 128, 199–210 (2002)
  • E. Fernández-Tarrazo A. Liñán, Flame Spread Over Solid Fuels in Opposite Natural Convection, Proc. Comb. Inst. , 29, 219-225 (2002)
  • V. Kurdyumov, E. Fernández-Tarrazo, A. Liñán, The anchoring of gaseous fuel jet diffusion flames in stagnant air Aerosp. Sci. Tech., 6, 507-516 (2002)
  • A. Liñan, E. Fernández-Tarrazo, M. Vera, A. L. Sánchez, Lifted Laminar Jet Diffusion Flames, Combust. Sci. Tech., 177 933 - 953 (2005)
  • E. Fernández-Tarrazo, M. Vera, A. Liñán, Lift-off and blow-off of a diffusion flame between parallel streams of fuel and air emerging from porous walls, Combust. Flame, 144 (2006) 261-276
  • V. Kurdyumov, E.Fernández-Tarrazo, J-M. Truffaut, J. Quinard, A. Wangher, G. Searby, Experimental and Numerical Study of Premixed Flame Flashback, Proc. Comb. Inst., 31:1275-1282 (2007)