Detailed combustion chemical mechanism for surrogates of representative jet fuels

Surrogate fuels are useful for computational fluid dynamics (CFD) simulations. However, there are two main challenges in surrogate fuel: defining an appropriate surrogate and designing compact and reliable kinetic models. Many works of defining an appropriate surrogate have been done in our previous work. In this study, we focus on obtaining compact and reliable kinetic models for jet surrogate fuels. A detailed mechanism was developed by combining n-dodecane, 2,5-dimethylhexane and toluene sub-mechanisms with AramcoMech 2.0 C₀–C₄ mechanism to mimic the combustion properties of three representative jet fuels. Extensive validation of the component mechanisms in surrogate is performed using abundant experimental data sets. Thereafter, various combustion properties of three jet fuels like ignition delay times, species concentrations in flow reactor and laminar flame speeds are simulated by using this surrogate kinetic mechanism and previous surrogate formulations. The simulations are compared with other well-known surrogate models and a wide range of experimental data. The comparisons show that the developed mechanism is substantially improved prediction accuracy of most considered combustion properties for different jet fuels in a wide range of conditions.     

MILD combustion of hydrogenated biogas under several operating conditions in an opposed jet configuration

MILD combustion of biogas takes its importance firstly from the combustion process that diminishes significantly fuel consumption and reduces emissions and secondly from the use of biogas which is a renewable fuel. In this paper, the influence of several operating conditions (namely biogas composition, hydrogen enrichment and oxidizer dilution) is studied on flame structure and emissions. The investigation is conducted in MILD regime with a special focus on chemical effects of CO₂ in the oxidizer. Opposed jet diffusion combustion configuration is adopted. The combustion kinetics is described by the Gri 3.0 mechanism and the Chemkin code is used to solve the problem.It is found that oxygen reduction has a significant effect on flame temperature and emissions while less sensitivity corresponds to hydrogen enrichment in MILD combustion regime. Temperature and species are considerably reduced by oxygen decrease in the oxidizer and augmented by hydrogen addition to the fuel. The maximum values of temperature and species are not influenced by the composition of the biogas in MILD regime. Blending biogas with hydrogen can be used to sustain MILD combustion at very low oxygen concentration in the fuel.In MILD combustion regime, the chemical effect of CO₂ in the oxidizer stream reduces considerably the flame temperature and species production, except CO which is enhanced. For high amounts of CO₂ in the oxidizer, the chemical effect of CO₂ becomes negligible.     

Hydrogen-enriched non-premixed jet flames: Compositional structures with near-wall effects

The species concentrations of non-premixed hydrogen and syngas flames were examined using results obtained from direct numerical simulation technique with flamelet generated manifold chemistry. Flames with pure H₂ and H₂/CO mixtures are discussed for an impinging jet flame configuration. Single-point data analyses are presented illustrating the effects of fuel composition on species concentrations. In general, scatterplots of all species show the effects of fuel variability on the flame compositional structures. The behaviours of major combustion products and key radicals species indicate the effects of CO concentration on the 2/CO syngas combustion. In particular, high concentration of CO tends to induce local extinction in the 2/CO flames in which critical chemical reactions of the fuel mixture such as CO + OH become important. The unsteady fluctuations of species profiles in the wall jet region characterise the complexity of the distributions of compositional structures in the near-wall region with respect to the effects of CO concentration on the combustion of hydrogen-enriched fuels.     

Hydrogen-enriched non-premixed jet flames: Analysis of the flame surface,flame normal,flame index and Wobbe index

A non-premixed impinging jet flame is studied using three-dimensional direct numerical simulation with detailed chemical kinetics in order to investigate the influence of fuel variability on flame surface, flame normal, flame index and Wobbe index for hydrogen-enriched combustion. Analyses indicate that the fuel composition greatly influences the H₂/CO syngas combustion, not only on the important local stoichiometric iso-mixture fraction surface distribution but also on the vortical structures in the flow field. As a result of CO addition to hydrogen-rich combustion, changes of the reaction zone in the flammable layer, shift of peak flame surface density distribution, shift of non-premixed regions, formation of widely populated scalar dissipation distribution rate with respect to tangential strain and reduction of global heat release are all found to appear. In particular, the CO addition induces a micromixing process which appears to be an important factor for the modelling investigation of turbulence/chemistry interaction especially for combustion modelling of H₂-rich syngas fuels.     

Effect of hydrogen on hydrogen–methane turbulent non-premixed flame under MILD condition

Energy crises and the preservation of the global environment are placed man in a dilemma. To deal with these problems, finding new sources of fuel and developing efficient and environmentally friendly energy utilization technologies are essential. Hydrogen containing fuels and combustion under condition of the moderate or intense low-oxygen dilution (MILD) are good choices to replace the traditional ones. In this numerical study, the turbulent non-premixed CH₄+H₂ jet flame issuing into a hot and diluted co-flow air is considered to emulate the combustion of hydrogen containing fuels under MILD conditions. This flame is related to the experimental condition of Dally et al. [Proc. Combust. Inst. 29 (2002) 1147–1154]. In general, the modelling is carried out using the EDC model, to describe turbulence–chemistry interaction, and the DRM-22 reduced mechanism and the GRI2.11 full mechanism to represent the chemical reactions of H₂/methane jet flame. The effect of hydrogen content of fuel on flame structure for two co-flow oxygen levels is studied by considering three fuel mixtures, 5%H₂+95%CH₄, 10%H₂+90%CH₄ and 20% H₂+80%CH₄(by mass). In this study, distribution of species concentrations, mixture fraction, strain rate, flame entrainment, turbulent kinetic energy decay and temperature are investigated. Results show that the hydrogen addition to methane leads to improve mixing, increase in turbulent kinetic energy decay along the flame axis, increase in flame entrainment, higher reaction intensities and increase in mixture ignitability and rate of heat release.     

Comprehensive chemical kinetic modeling of the oxidation of 2-methylalkanes from C7 to C20

Conventional petroleum jet and diesel fuels, as well as alternative Fischer–Tropsch (FT) fuels and hydrotreated renewable jet (HRJ) fuels, contain high molecular weight lightly branched alkanes (i.e., methylalkanes) and straight chain alkanes (n-alkanes). Improving the combustion of these fuels in practical applications requires a fundamental understanding of large hydrocarbon combustion chemistry. This research project presents a detailed and reduced chemical kinetic mechanism for singly methylated iso-alkanes (i.e., 2-methylalkanes) ranging from C₇ to C₂₀. The mechanism also includes an updated version of our previously published C₈–C₁₆n-alkanes model. The complete detailed mechanism contains approximately 7200 species 31400 reactions. The proposed model is validated against new experimental data from a variety of fundamental combustion devices including premixed and non-premixed flames, perfectly stirred reactors and shock tubes. This new model is used to show how the presence of a methyl branch affects important combustion properties such as laminar flame propagation, ignition, and species formation.     

An experimental and kinetic modeling study of n-octane and 2-methylheptane in an opposed-flow diffusion flame

Fischer–Tropsch (FT) fuels derived from biomass syngas are renewable fuels that can replace conventional petroleum fuels in jet engine and diesel engine applications. FT fuels typically contain a high concentration of lightly methylated iso-alkanes, whereas petroleum derived jet and diesel fuels contain large fractions of n-alkanes, cycloalkanes, and aromatics plus some lightly methylated iso-alkanes. In order to better understand the combustion characteristics of FT and petroleum fuels, this study presents new experimental data for 2-methylheptane and n-octane in an opposed-flow diffusion flame. The high temperature oxidation of 2-methylheptane and n-octane has been modeled using an extended transport database and a reaction mechanism consisting of 3401 reactions involving 714 species. The proposed model shows good qualitative and quantitative agreement with the experimental data. The measured and predicted concentrations of 1-alkenes and ethylene are higher in the n-octane flame, while the concentrations of iso-alkenes (especially iso-butene) and propene are higher in the 2-methylheptane flame. The proposed chemical kinetic model is used to delineate the reactions pathways leading to these observed differences in product species concentrations. An uncertainty analysis was conducted to assess experimental and modeling uncertainties. The results indicate that the simulations are sensitive to the transport parameters used to calculate fuel diffusion.     

Numerical investigations on tri-fuel chemical kinetics of hydrogen + Methane +LPG/air mixtures using reduced skeletal mechanism

The combustion and ignition characteristics of three fuels with different reactivities have been investigated by a reduced chemical kinetic model. In the present work, the chemical kinetics of conventional single fuel and binary fuel, relevant to gas-turbine engines, are extended and attempted to explore in the tri-fuel (TF) context, with the help of TF blends of LPG + CH₄+H₂ at the pressure and temperature range of 1–20 atm and 900–2000 K, respectively. The blending of hydrogen with hydrocarbon fuels improves flame propagation, reduces emissions, and increases the combustion performance of the engine. A detailed study is conducted to explore the characteristics of TF mixture over a wide range of operating conditions by considering eight different test mixtures (M1-M8). The test mixtures (M2 to M4) contain higher hydrogen content and thus hydrogen kinetics will tend to dominate, while test mixtures (M6 to M8) contain a higher concentration of hydrocarbons, thus the methyl radical chemistry plays a prominent role in the oxidation process. Such contrasting trends were further explored by extensive chemical kinetic modeling with the help of the reduced USC Mech_50 species model from our previous work [1] to analyze the ignition delay time, laminar flame speed, flame temperature, and heat release rate characteristics. In addition, the reaction pathway analysis through sensitivity analysis of OH and CO radical, and flow rate sensitivity analysis has also been conducted to highlight the essential chemical reactions which play a crucial role in auto-ignition, combustion, and emissions characteristics of TF blends.     

Characteristics of oxy-fuel combustion in gas turbines

This paper reports on a numerical study of the thermodynamic and basic combustion characteristics of oxy-fuel combustion in gas turbine related conditions using detailed chemical kinetic and thermodynamic calculations. The oxy-fuels considered are mixtures of CH₄, O₂, CO₂ and H₂O, representing natural gas combustion under nitrogen free gas turbine conditions. The GRI Mech 3.0 chemical kinetic mechanism, consisting of 53 species and 325 reactions, is used in the chemical kinetic calculations. Two mixing conditions in the combustion chambers are considered; a high intensity turbulence mixing condition where the combustion chamber is assumed to be a well-stirred reactor, and a typical non-premixed flame condition where chemical reactions occur in thin flamelets. The required residence time in the well-stirred reactor for the oxidation of fuels is simulated and compared with typical gas turbine operation. The flame temperature and extinction conditions are determined for non-premixed flames under various oxidizer inlet temperature and oxidizer compositions. It is shown that most oxy-fuel combustion conditions may not be feasible if the fuel, oxygen and diluent are not supplied properly to the combustors. The numerical calculations suggest that for oxy-fuel combustion there is a range of oxygen/diluent ratio within which the flames can be not only stable, but also with low remaining oxygen and low emission of unburned intermediates in the flue gas.     

Effect of the addition of H2 and H2O on the polluting species in a counter-flow diffusion flame of biogas in flameless regime

Biogas is obtained by fermentation of biomass, it is a renewable fuel and practically CO₂ neutral, offers a significant advantage compared to other fuels for its low carbon/hydrogen ratio (1 atom of carbon and 4 hydrogen atoms). Thus, the level of CO₂ emissions from biogas is lower than that of the other fuels. Biogas is a biodegradable and renewable fuel; its benefits are conjugated especially in a flameless combustion process that significantly reduces fuel consumption and polluting emissions. In this paper, we study the effects of the dilution of a mixture of the biogas BG75 (75% CH₄ and 25% CO₂) – hydrogen by a volume of water vapor ranging from 10% to 50%. The configuration of an opposed jet flame is used with a constant strain rate of 120 s^?1. The chemical kinetics is described by the Gri3.0 mechanism. It has been found that the combustion structure is very sensitive to the various parameters.     

Cool flame partial oxidation and its role in combustion and reforming of fuels for fuel cell systems

The purpose of this review was to integrate the most recent and relevant investigations on the auto-oxidation of fuel oils and their reforming into hydrogen-rich gas that could serve as a feed for fuel cells and combustion systems. We consider the incorporation of partial oxidation under cool flame conditions to be a significant step in the reforming process for generation of hydrogen-rich gas. Therefore, we have paid particular attention to the partial oxidation of fuels at low temperature in the cool flame region. This is still not a well-understood feature in the oxidation of fuels and can potentially serve as a precursor to low NO_x emissions and low soot formation. Pretreatment, including atomization, vaporization and burner technology are also briefly reviewed. The oxidation of reference fuels (n-heptane C₇H₁₆, iso-octane C₈H₁₈ and to a lesser extent cetane C₁₆H₃₄) in the intermediate and high temperature ranges have been studied extensively and it is examined here to show the significant progress made in modeling the kinetics and mechanisms, and in the evaluation of ignition delay times. However, due to the complex nature of real fuels such as petroleum distillates (diesel and jet fuel) and biofuels, much less is known on the kinetics and mechanisms of their oxidation, as well as on the resulting reaction products formed during partial oxidation. The rich literature on the oxidation of fuels is, hence, limited to the cited main reference fuels. We have also covered recent developments in the catalytic reforming of fuels. In the presence of catalysts, the fuels can be reformed through partial oxidation, steam reforming and autothermal reforming (ATR) to generate hydrogen. But optimum routes to produce cost effective hydrogen fuel from conventional or derivative fuels are still debatable. It is suggested that the use of products emanating from partial oxidation of fuels under cool flame conditions could be attractive in such reforming processes, but this is as yet untested. The exploitation of developments in oxidation, combustion and reforming processes is always impacted by the resulting emission of pollutants, including NO_x, SO_x, CO and soot, which have an impact on the health of the fragile ecosystem. Attention is paid to the progress made in innovative techniques developed to reduce the level of pollutants resulting from oxidation and reforming processes. In the last part, we summarize the present status of the topics covered and present prospects for future research. This information forms the basis for recommended themes that are vital in developing the next generation energy-efficient combustion and fuel cell technologies.     

Hydrogen dual-fuelling of compression ignition engines with emulsified biodiesel as pilot fuel

Dual-fuel compression ignition (CI) engine operation with hydrogen is a promising method of using hydrogen gas in CI engines via high-cetane pilot fuel ignition. However, hydrogen dual-fuel operation with neat pilot fuels typically produce: high NO_x emissions; and high combustion chamber pressure rise rates (leading to increased “Diesel knock” tendencies). While water-in-fuel emulsions have been used during normal CI engine operation to cool the charge and slow combustion rates in an effort to reduce NO_x emissions, these water-in-fuel emulsions have not been tested as pilot fuels during hydrogen dual-fuel combustion. In this work two water-in-biodiesel emulsions are tested as pilot fuels during hydrogen dual-fuel operation. Hydrogen dual-fuel operation generally produces at best comparable thermal efficiencies compared with normal CI engine operation, while the emulsified biodiesel pilot fuels generally increase thermal efficiencies when compared with the neat biodiesel pilot fuel during dual-fuel operation. There is also a clear reduction in NO_x emissions with emulsified pilot fuel use compared with the neat pilot fuel. The thermal efficiency increase is more apparent at higher engine speeds, while the NO_x reduction is more apparent at lower speeds. This is due to two conflicting effects (exclusive to emulsified pilot fuel) that occur in tandem. The first is the cooling effect of water vapourisation on the charge, while the second is the microexplosion phenomenon which enhances fuel-air mixing. The NO_x emission reduction is due to the emulsified pilot fuel lowering pressure rise rates compared with the neat pilot fuel, while the efficiency increase is due to a more homogeneous charge resulting from the violent microexplosion of the emulsified pilot fuel. Smoke, CO, HC and CO₂ emissions remain comparable to neat pilot fuel tests. Overall, emulsified pilot fuels can reduce NO_x emissions and increase thermal efficiencies, however not at the same instance and under different operating conditions. The general trends of reduced power output, reduced CO₂ and increased water vapour emission during hydrogen dual-fuel operation (with neat pilot fuels) are also maintained.     

A new approach for simplifying the calculation of flue gas specific heat and specific exergy value depending on fuel composition

In this paper, a new approach is proposed for simplifying the calculation of flue gas specific heat and specific exergy value in one formulation depending on fuel chemical composition. Combustion products contain different gases such as CO₂, SO₂, N₂, O₂, H₂O and etc., depending on the burning process. Specific heat and exergy of the flue gas differ depending on the chemical composition of fuels, excess air ratio and gas temperature. Through this new approach, specific heat and specific exergy value of combustion products can be estimated accurately in one formulation by entering the chemical composition of fuels, excess air ratio and gas temperature. The present approach can be applied to all carbon based fuels, especially biomass, fossil fuels and fuel mixtures for co-combustion and is so suitable for practical estimation of flue gas specific heat and specific exergy values provided that the fuel chemical composition is given.     

Numerical study of laminar flame properties of diluted methane-hydrogen-air flames at high pressure and temperature using detailed chemistry

Technical limits of high pressure and temperature measurements as well as hydrodynamic and thermo-diffusive instabilities appearing in such conditions prevent the acquisition of reliable results in term of burning velocities, restraining the domain of validity of current laminar flame speed correlations to few bars and hundreds of Kelvin. These limits are even more important when the reactivity of the considered fuel is high. For example, the high-explosive nature of pure hydrogen makes measurements even more tricky and explains why only few correlations are available to describe the laminar flame velocity of high hydrogen blended fuels as CH₄-H₂ mixtures. The motivation of this study is thereby to complement experimental measurements, by extracting laminar flame speeds and thicknesses from complex chemistry one-dimensional simulations of premixed laminar flames. A wide number of conditions are investigated to cover the whole operating range of common practical combustion systems such as piston engines, gas turbines, industrial burners, etc. Equivalence ratio is then varied from 0.6 to 1.3, hydrogen content in the fuel from 0 to 100%, residual burned gas mass ratio from 0 to 30%, temperature of the fresh mixtures from 300 to 950 K, and pressure from 0.1 to 11.0 MPa. Many chemical kinetics mechanisms are available to describe premixed combustion of CH₄-H₂ blends and several of them are tested in this work against an extended database of laminar flame speed measurements from the literature. The GRI 3.0 scheme is finally chosen. New laminar flame speed and thickness correlations are proposed in order to extend the domain of validity of experimental correlations to high proportions of hydrogen in the fuel, high residual burned gas mass ratios as well as high pressures and temperatures. A study of the H₂ addition effect on combustion is also achieved to evaluate the main chemical processes governing the production of H atoms, a key contributor to the dumping of the laminar flame velocity.     

Flame structure and NO emissions in gas combustion of low calorific heating value

Numerical study on addition effects of CO and CO₂ in fuel side (H₂/Ar) on flame structure and NO emission behaviour in counterflow diffusion flame has been conducted with detailed chemistry to fundamentally understand gas combustion of low calorific heating value. A modified Miller–Bowman reaction scheme including a complementary C₂-reaction subset is adopted. The radiative heat loss term, which is based on an optically thin model and it especially important at low strain rates, is included to cover the importance of the temperature dependence on NO emission. Special interest is taken to estimate the roles of added CO and CO₂ in fuel side on flame structure and NO emission characteristics. Increasing CO concentration in fuel side contributes to the enhancement of combustion due to the increase effect of the concentration of reactive species. The increase of added CO₂ concentration in fuel side suppresses overall reaction rate due to the high heat capacity. It is seen that chemical effects due to the breakdown of added CO₂ in fuel side make C₂-branch chemical species be remarkably formed and the prevailing contribution of prompt NO is a direct outcome of these effects. It is found that in the combined forms of H₂/CO/CO₂/Ar fuels the effects of added CO and CO₂ concentrations in fuel side compete contrarily to each other in NO emission behaviour. Particularly the role of added CO is stressed in the side of restraining prompt NO. Copyright © 2003 John Wiley & Sons, Ltd.     

Hydrogen enrichment of methane and syngas for MILD combustion

Moderate or Intense Low-oxygen Dilution (MILD) combustion is a technology with important characteristics such as significant low emission and high-efficiency combustion. The hydrogen enrichment of conventional fuels is also of interest due to its favorable characteristics, such as low carbon-containing pollutants, high reaction intensity, high flammability, and thus fuel usage flexibility. In this study, the effects of adding hydrogen to methane and syngas fuels have been investigated under conditions of MILD combustion through numerical simulation of a well-set-up MILD burner. The Reynolds-Averaged Navier-Stokes (RANS) approach is adopted along the Eddy Dissipation Concept (EDC) combustion model with two different chemical mechanisms. Molecular diffusion is modeled using the differential diffusion approach. The effects of oxidizer dilution and fuel jet Reynolds number on the reactive flow field have been studied. Results show that with an increase in hydrogen portion of the fuel mixtures, the volume of the high-temperature region of combustion field increases whereas a reduction of oxidizer oxygen content leads to more proximity to the MILD condition. Increasing the fuel jet Reynolds number will result in an expansion of the combustion zone and shifting of this region in the axial direction. Predictions revealed that the methane flame is more sensitive to the oxidizer dilution and fuel jet Reynolds number than syngas. Moreover, enrichment of fuel with hydrogen seems to be better for acquiring condition of the MILD combustion for syngas rather than methane. Indeed, syngas shows more sensitivity to hydrogen enrichment than methane, which makes hydrogen a good additive to syngas in terms of MILD condition benefits.     

Flame flow field interaction in non-premixed CH4/H2 swirling flames

Alternative fuels and stocks like biomass or chemical and refinery waste, may potentially be used in gas turbines and industrial applications after gasification. Thus, understanding the role of hydrogen in these fuels is critical to the broader aim of utilising alternative fuels for power generation. In this work, the interaction between the flame and the flow field was studied in a quarl-stabilised swirl non-premixed flame burning CH₄ and H₂–enriched CH₄. Simultaneous high-speed OH-PLIF/PIV imaging at 5 kHz was carried out on these flames to explore the flame-flow interaction. The instantaneous flow fields in the CH₄ or CH₄+H₂ flames showed a small scale vortical structure near the shear layers, which were not apparent in the time-averaged flow fields. Increasing H₂% in the fuel jet was observed to dampen the velocity fluctuations. The fuel composition affected the spatial location of the reaction zone; in the CH₄ flames, the axial position of the reaction zone is seen to track the relatively large-magnitude axial velocity fluctuations while remaining in locally low-speed regions of the flow. In contrast, in H₂-enriched flames, where the flame is more robust, the reaction zone was able to survive longer, in terms of axial distance, in the vicinity of high swirling jet velocity, with less sensitivity to velocity fluctuations. With increasing the H₂%, the reaction zone steadily leaves the IRZ towards the swirling jet flow and localised between its outer and inner vortices. This acts as a stabilisation factor where the internal vortices convect hot product towards the fresh mixture. Moreover, the flame curvatures, the vorticity and compressive strain fields interactions with the reaction zone are presented and discussed. This article outlines results that yield more in-depth insight into hydrogen-enriched hydrocarbon non-premixed swirling flames' combustion, which is essential to accelerate the fuel switching from hydrocarbons to hydrogen.     

Imaging of diluted turbulent ethylene flames stabilized on a Jet in Hot Coflow (JHC) burner

The spatial distributions of the hydroxyl radical (OH), formaldehyde (H₂CO), and temperature imaged by laser diagnostic techniques are presented using a Jet in Hot Coflow (JHC) burner. The measurements are of turbulent nonpremixed ethylene jet flames, either undiluted or diluted with hydrogen (H₂), air or nitrogen (N₂). The fuel jet issues into a hot and highly diluted coflow at two O₂ levels and a fixed temperature of 1100 K. These conditions emulate those of moderate or intense low oxygen dilution (MILD) combustion. Ethylene is an important species in the oxidation of higher-order hydrocarbon fuels and in the formation of soot. Under the influence of the hot and diluted coflow, soot is seen to be suppressed. At downstream locations, surrounding air is entrained which results in increases in reaction rates and a spatial mismatch between the OH and H₂CO surfaces. In a very low O₂ coflow, a faint outline of the reaction zone is seen to extend to the jet exit plane, whereas at a higher coflow O₂ level, the flames visually appear lifted. In the flames that appear lifted, a continuous OH surface is identified that extends to the jet exit. At the “lift-off” height a transition from weak to strong OH is observed, analogous to a lifted flame. H₂CO is also seen upstream of the transition point, providing further evidence of the occurrence of preignition reactions in the apparent lifted region of these flames. The unique characteristics of these particular cases has led to the term transitional flame.     

Experimental analysis of the effects of hydrogen addition on methane combustion

This paper presents gas emissions from turbulent chemical flow inside a model combustor, for different blending ratios of hydrogen–methane composite fuels. Gas emissions such as CO and O₂ from the combustion reaction were obtained using a gas analyzer. NOx emissions were measured with a NOx analyzer. The previously obtained flame temperature distributions were also presented. As the amount of hydrogen in the mixture increases, more hydrogen is involved in the combustion reaction, and more heat is released, and the higher temperature levels are resulted. The results have shown that the combustion efficiency increases and CO emission decreases when the hydrogen content is increased in blending fuel. It is also shown that the hydrogen–methane blending fuels are efficiently used without any important modification in the natural gas burner. Copyright © 2011 John Wiley & Sons, Ltd.