Methanol Flames Research Articles

Measurements and a new correlation of methanol laminar flame speeds at temperatures up to 916 K and elevated pressures behind reflected shock waves

A side-wall-imaging shock tube was utilized to measure the laminar flame speed of methanol in 21% O2/79% Ar (airgon) behind reflected shock waves. The flames, initiated via laser-induced spark ignition, were tracked through schlieren imaging, which allowed the extraction of unstretched methanol flame speeds using an area-averaged linear curvature model. Methanol/airgon flame speeds were measured at atmospheric pressure at four equivalence ratios (0.8, 1, 1.2, and 1.4) and at temperatures between 640 K and 916 K; elevated-pressure measurements at pressures up to 2.6 atm were performed at 750 K for three equivalence ratios (0.8, 1, and 1.2) and at pressures up to 2 atm at 820 K for the stoichiometric mixture. Four Kinetic models, NUIG 1.3, Aramco 3.0, FFCM-2, and Zhang 2017, were used to compare with the present measurements. The model-simulated flame speeds are observed to diverge at temperatures above 650 K, with the Zhang 2017 and NUIG 1.3 models showing the best agreement with experimental data. The Aramco 3.0 model is shown to consistently underpredict methanol laminar flame speeds at high temperatures and elevated pressures, whereas the FFCM-2 model shows overprediction at temperatures under 750 K, particularly at rich conditions. The methanol/airgon flame speed data were then mixture-scaled to obtain the equivalent methanol/air results, which trend closely with lower-temperature flame speed measurements reported in the literature. The first methanol/air laminar flame speed correlation validated at temperatures up to 916 K was constructed by fitting mixture-scaled methanol/air data and available literature values using a non-Arrhenius form.

Coherent Structures Analysis of Methanol and Hydrogen Flames Using the Scale-Adaptive Simulation Model

Computational fluid dynamics techniques were applied to reproduce the characteristics of the liquid methanol burner described in a previous paper by Guevara et al. In this work, the unstable Reynolds-averaged Navier–Stokes (U-RANS) approach known as the Scale-Adaptive Simulation (SAS) model was employed, together with the steady nonadiabatic flamelets combustion model, to characterize and compare methanol and hydrogen flames. These flames were compared to determine whether this model can reproduce the coherent dynamic structures previously obtained using the LES model in other investigations. The LES turbulence model still entails a very high computational cost for many research centers. Conversely, the SAS model allows for local activation and amplification, promoting the transitions of momentum equations from the stationary to the transient mode and leading to a dramatic reduction in computational time. It was found that the global temperature contour of the hydrogen flame was higher than that of methanol. The air velocity profile peaks in the methanol flame were higher than those in hydrogen due to the coherent structures formed in the near field of atomization. Both flames presented coherent structures in the form of PVC; however, in the case of hydrogen, a ring-type vortex surrounding the flame was also developed. The axial, tangential, and radial velocity profiles of the coherent structures along the axial axis of the combustion chamber were analyzed at a criterion of Q = 0.003. The investigation revealed that the radial and tangential components had similar behaviors, while the axial velocity components differed. Finally, it was found that, using the SAS model, the coherent dynamic structures of the methanol flame were different from those obtained in previous works using the LES model.

From inherent correlation to constrained measurement: Model-assisted calibration in MBMS experiments

Synchrotron-based molecular-beam mass spectrometry (MBMS) can provide detailed species-resolved information to help develop, validate and optimize combustion kinetic models. While quantification of stable species can be achieved within 30% uncertainty, the measured mole fractions of reactive intermediates often have large systematic errors, mainly due to the large uncertainties associated with estimated photoionization cross sections. These measurements are therefore less effective in improving the model accuracy, and it remains a challenge to make full use of those data for important reactive intermediates with relatively large uncertainties. In the present work, we propose a model-assisted calibration method to reduce the uncertainty of the measurements for those reactive species in the MBMS experiments. The method takes advantage of the inherent correlation of the systematic uncertainty in the MBMS measurements and uses the accurate model predictions to calibrate the correlated experimental data. By global uncertainty analysis, the kinetic model for the methanol/O2 flame was analyzed to select the optimal experimental conditions for which the model prediction of the hydroxymethyl radical (CH2OH) has the smallest uncertainty. Then the correlation factor for the systematic uncertainty is determined by analyzing the new measurement and the model prediction under the designed condition. The correlation factor determined has been successfully used to calibrate the peak mole fraction of the CH2OH radical in a laminar premixed methanol flame, reported earlier.

Combustion Chemistry of Rich Methanol–Air Mixtures

Chain branching and heat release processes and their influence on the burning velocity of premixed rich and near-stoichiometric methanol–air flames were studied by numerical simulation and sensitivity analysis. The phenomenon of superadiabatic temperatures in these flames due to the kinetic mechanism of methanol combustion was first detected. Comparison of the simulation results of the structure of methanol and formaldehyde flames shows that the formation of water in superequilibrium concentrations in flames does not necessarily lead to superadiabatic temperatures, as believed earlier. It was first found that decreasing the dilution of the CH3OH/O2/N2combustible mixture with nitrogen at a constant equivalence ratio enhances the superadiabatic temperature effect. According to simulation results, in a rich near-limit methanol flame, the role of the chain branching reactions H + O2 = O + OH and O + H2 = H + OH is negligible due to their low rate. At relatively low temperatures, branching occurs mainly in reactions involving HO2and H2O2peroxide compounds, whose concentration is orders of magnitude higher than the concentration of the main chain carriers H, O, and OH. From the sensitivity analysis, it follows that the burning velocity of methanol flames is positively influenced mainly by the reactions of formation of chain carriers and is negatively influenced by the reactions of consumption of chain carriers. reactions having a major contribution to heat release but are not involved in the formation and consumption of radicals have small sensitivity coefficients.

Experimental and modeling study of nitric oxide formation in premixed methanol + air flames

Validation and further development of models for alcohol combustion requires accurate experimental data obtained under well-controlled conditions. To this end, measurements of nitric oxide, NO, mole fractions in premixed laminar methanol + air flames have been performed using saturated laser-induced fluorescence, LIF. The methanol flames have been stabilized at atmospheric pressure and initial gas temperature of 318 K at equivalence ratios ɸ = 0.7–1.5 using the heat flux method that allows for simultaneous determination of their laminar burning velocity. The LIF signal is converted into NO mole fraction via calibration measurements, which have been performed in flames of methane, methanol and syngas seeded with known amounts of NO. The experimental approach is verified by the measurements of NO mole fractions in the post flame zone of methane flames, investigated in previous studies at similar conditions. Data on the NO formation together with burning velocities for methanol and methane obtained under adiabatic flame conditions provide highly valuable input for model validation. They have been compared with predictions of six different chemical kinetic mechanisms. Summarizing the behavior of all models tested with respect to burning velocities and NO formation in flames of methane and methanol, the mechanism of Glarborg et al. (2018) and the San Diego mechanism (2019) demonstrate uniformly satisfactory performance.

Numerical study of methanol flames in laminar forced convective environment using short chemical kinetics mechanism

Due to recent interest in methanol economy, it is seen that a numerical study of combustion of methanol in a comprehensive manner is necessary. Motivated from this interest and based on the studies from literature, a numerical study on prediction of structures of non-premixed methanol-air flames in laminar forced convective environment is reported. Two-dimensional, planar and axisymmetric, computational domains are considered. Corresponding governing equations for conservation of mass, momentum, species and energy have been solved using Ansys FLUENT. The numerical model incorporates multi-component diffusion, variable thermal and physical properties, a short chemical kinetics mechanism with 18 species and 38 elementary reactions, and a non-luminous thermal radiation model. Homogeneous flames in opposed flow and heterogeneous flames in cross-flow and co-flow configurations are studied. For heterogeneous flames, interface conditions at the liquid methanol surface are defined systematically using a user-defined function. Numerical results are validated against the experimental results available in literature. Results in terms of mass burning rates, flow, species and temperature fields have been presented to describe the flame characteristics.

Impact of Selected Electrical Cables Slope on Flame Out Time and Flame Spread

Abstract The aim of the research described in this paper was to study the impact of the electrical cables slope on the flame out time and the flame spread rate. Measured cables were thermally loaded by methanol flame (diameter of the container was 106 mm) at seven different slopes with respect to the horizontal plane (the slopes were 0° – horizontal orientation, 15°, 30°, 45°, 60°, 75° and 90° - vertical orientation). The first tested electrical cable was a copper three-core power one resistant to the flame spread with circuit integrity of the cable system during 30 minutes under fire (cross-section of each core was 1.5 mm2). The second tested electrical cable was a copper two-core signal one resistant to the flame spread with circuit integrity of the cable system during 30 minutes under fire (cross-section of each core was 0.5 mm2). The first electrical cable did not show reaction to fire class. The reaction to fire class of the second tested cable was B2ca, s1, d1, a1. The obtained results proved that slope had virtually no impact on the flame out time and the flame spread over the tested cable surface (tested cables of all slopes stopped burning after 1 to 5 seconds after methanol flame burned out). Likewise, the flame spread was only negligibly beyond the border of flame action for each cable slope.

Experimental investigation on methanol auto-ignition in a compression ignition engine under DMDF mode

At high loads, Diesel-Methanol Dual Fuel (DMDF) engines strongly rely on high methanol substitution for diesel proportion (MSP) to achieve high efficiency combustion and reduce nitrogen oxides (NOx) and soot emissions. However, high MSP is limited by the probability of methanol auto-ignition. The experimental study was conducted to investigate into the influence factors of methanol auto-ignition under diesel engine conditions at 50% of full load. Meanwhile the testing results concerning combustion characteristics and emissions have been analyzed. Experimental results showed that if there was apparent heat release before TDC, which was earlier than diesel fuel injection, it indicated that methanol auto-ignition occurred. In order to avoid methanol auto-ignition which is very easily to cause knock or rapid pressure rise, the in-cylinder mean temperature should be less than 990 K (at this case, the intake temperature was 338 K) before diesel injection timing. As intake temperature increased, methanol heat release timing was advanced and the heat release rate (HRR) was gradually accelerated. If the injection timing of diesel was later than that of methanol auto-ignition, almost all diesel fuel would be burned in the form of diffusion combustion in the methanol flame, leading to the increase of soot emissions. Methanol auto-ignition would be inhibited by EGR gas. The EGR and MSP had a great impact on both the ignition timing and the peak HRR of methanol auto-ignition. As EGR ratio increased, so did the incomplete combustion loss of methanol. As long as methanol auto-ignition occurred, the increase of MSP would result in a decrease in NOx emissions, but soot emissions were increased instead.

Investigation on the oxidation chemistry of methanol in laminar premixed flames

In this work, oxidation chemistry of methanol was investigated in laminar premixed flames. Laminar burning velocities of methanol/air mixtures at 423K and 1–10atm were measured in a spherical combustion vessel, extending the range of equivalence ratio up to 2.1. A stoichiometric premixed flat flame of methanol/O2/Ar at 0.04atm was also conducted using synchrotron VUV photoionization mass spectrometry (SVUV-PIMS) to obtain more detailed kinetic information. Particularly, fuel-derived radicals including methoxy radical and hydroxymethyl radical were observed, while formaldehyde (CH2O) and formic acid (HOCHO) were identified as the abundantly produced intermediates in methanol flame. A methanol model was developed and validated against the experimental data obtained in this work, as well as in literature. In the predictions of laminar burning velocities, HO2 radical plays an important role under very rich conditions. Besides, the measurement of formaldehyde and formic acid in methanol flame is helpful to constrain the rate constant of CH2OH+O2=CH2O+HO2, which presents large uncertainties at high temperatures.

Laminar flame characteristics and kinetic modeling study of methanol-isooctane blends at elevated temperatures

Laminar flame speeds of methanol-isooctane blends were experimentally determined using the spherically propagating flame in a constant volume chamber at two initial temperatures (363 and 393K), different blending ratios of methanol in liquid volume (0%, 20%, 40%, 80%, 100%), and over equivalence ratios of 0.7–1.6. Nonlinear methodology was employed to remove the stretch effect in the data processing. Results indicate that laminar flame speeds of methanol flame reach the peak at equivalence ratio around 1.2 and that of isooctane at equivalence ratio around 1.1. For the mixtures with less than 40% methanol, laminar flame speeds show moderate increase at all equivalence ratios. However, further increasing methanol addition will greatly accelerate laminar flame speeds at rich mixture sides but give slight change at lean mixture sides. Markstein length shows an increase tendency with the methanol addition at the equivalence ratios larger than a critical value while Markstein length gives a decrease tendency at the equivalence ratios smaller than the critical value. The critical equivalence ratio is between 1.2 and 1.3. Among the thermal effect, diffusive effect and kinetic effect, the kinetic effect was found to be the major factor bringing the variation of laminar flame speed with the variation of blending ratio. A kinetic model (IM model) was developed on the basis of the isooctane model of Chaos et al. (2007). The IM model shows good prediction on measured laminar flame speeds under all conditions. Reaction pathway reveals that the HCO and H productions are promoted while the productions of stable species are inhibited in the case of methanol addition into the isooctane at rich mixture sides, resulting in the laminar flame speed enhancement. These behaviors are verified from the sensitivity analysis and the concentrations of the reactive radicals.

Application of Conditional Source-term Estimation to two turbulent non-premixed methanol flames

Conditional Source-term Estimation (CSE) is a turbulent combustion model that uses conditional averages to close the chemical source term. Previous CSE studies have shown that the model is able to predict the flame characteristics successfully; however, these studies have only focused on simple hydrocarbon fuels mostly composed of methane. The objective of the present paper is to evaluate the capabilities of CSE applied to turbulent non-premixed methanol flames, which has never been done previously. The current study investigates two different types of methanol flames: piloted and bluff-body flames. For the piloted flame, the standard k–ε model is used for turbulence modelling, while the Shear Stress Transport (SST) k–ω model is applied to the bluff-body case. Different values of empirical constants within the turbulence models were tested, and it was found that Cε1 = 1.7 for the piloted flame and γ2 = 0.66 for the bluff-body flame provided the best agreement with experimental measurements for the mixing field. Detailed chemistry is included in tabulated form using the Trajectory Generated Low-Dimensional Manifold (TGLDM) method. The predictions including both the Favre-averaged and conditional mass fraction of reactive species and temperature are compared with available experimental data and previous numerical results. Overall, the CSE predictions of conditional and unconditional quantities are in good agreement with the experimental data except for hydrogen. Sources of discrepancies are identified such as the chemical kinetics and neglect of differential diffusion. Large eddy simulations may also help to improve the velocity and mixing field predictions.

Large-Scale Experimental Investigation of the Fire Characteristics Parameters of Methanol in Coal Chemical Industry

A steel channel with the size of 30×2×1.2 m was made to simulate the full surface fire of 50000 m3methanol tank in coal-to-olefins industry. Some fire characteristic parameters of methanol were investigated, including flame spread rate, flame height, temperature distribution and radiation heat flux distribution. It is found that the flame spread rate of methanol is 1.98 m/s and the flame height could reach to 3.2 m. The temperature of methanol flame is first up and then down with the increase of height, while the highest temperature is 768oC. It is also found that the radiation heat flux of methanol flame is in the changes between 4.4 kW/m2and 12.2 kW/m2. The feature of methanol fire is different from the normal oil fire, which is worth for us to pay more attention.

Steady laminar flame characteristics over methanol surface with air co-flow

A numerical investigation of the flame characteristics and mass burning rates of steady laminar diffusion flames established over methanol surface under co-flow configuration is presented. A numerical model that solves the transient, two-dimensional gas-phase governing conservation equations using global single-step reaction kinetics for methanol-air oxidation is employed for the present investigations. The effect of liquid-phase transport is neglected for the present quasi-steady burning process by assuming that the fuel pool is thin and its level is maintained constant by supplying fuel at a rate at which it is being consumed. Since the gas-phase combustion occurs following evaporation from the liquid fuel surface, appropriate interfacial boundary conditions are specified. The model is validated using experimental and numerical temperature profile data across a methanol flame for a particular co-flow configuration reported in literature. Thereafter, parametric investigations are carried out by varying the co-flow air velocity in the range of 0.05–0.75 m/s, keeping the fuel pool length as 20 mm. A detailed discussion of the effect of co-flow air velocity on the thermal and flow fields, as well as on the local and average mass burning rates, is presented. It is observed that as the co-flow air velocity is increased, the mass burning rate attains a minima at an intermediate velocity of around 0.4 m/s for the present configuration. The thermal and flow fields, variation of fuel vapor mass fraction normal to the interface and the diffusion of oxidizer into the flame zone are investigated at various co-flow velocities to explore and explain the flame characteristics.

EXPERIMENTAL STUDY ON INFLUENCE OF STACK EFFECT ON FIRE IN THE COMPARTMENT ADJACENT TO STAIRWELL OF HIGH RISE BUILDING

In this paper, to study the influence of stack effect on fire in the compartment adjacent to a stairwell, a set of experiments were conducted by varying the pool size, top vent state and bottom vent size in a 1/3 scaled 12-layer-stairwell configuration. The phenomenon of methanol flame tilting in the fire room was observed and studied. Results showed that the flame tilt angle increases with an increase of Ri-1. The temperatures of hot gases in the fire room decrease due to the cooling effect of fresh air induced by stack effect. The mass loss rate of methanol fuel is influenced by fresh air flow sucked into fire room due to stack effect. On the basis of the experimental results, we conclude that the velocity of air flow into fire room is proportional to 1/3 power of the heat release rate in the stairwell.

Effects of the ambient temperature and initial diameter in droplet combustion

Results are presented from transient numerical simulations of combustion of an isolated heptane (n-C7H16) droplet in nearly quiescent ambient air. The focus is on the effects of environment temperature and droplet size on the combustion characteristics. Droplet sizes range from 10μm to 1mm, environment temperatures range from 800K to 1600K, and pressure is 1atm.The results show that ignition delay times have a very moderate dependence on droplet diameter. With an increase in droplet diameter, the ignition delay time first decreases near the ignitable diameter and then increases far from the ignitable diameter. The ignition stand-off ratio always decreases with an increase in droplet diameter. A strong but short-lived convection, which is generated following the ignition, is demonstrated for the first time. The convection is caused by gas expansion which ‘pushes’ the droplet toward the incoming flow. At lower temperatures, the transition from the kinetically controlled regime to the diffusion controlled regime is shifted to larger droplet diameters, and a larger range of droplet sizes is affected by the transition. Flame stand-off ratios are higher, and flame temperatures are lower, for small droplets. The transient evolution of heat release rate in droplet flames is presented for the first time. The heat release rate first exhibits thermal runaway (ignition), then decreases once the diffusion flame is established, and finally increases precipitously towards the end of the droplet lifetime due to an increase in strain rate. The heat release rates exhibit a strong dependence on droplet diameter.Finally, a comparison of the combustion characteristics of methanol and heptane droplets is presented, which establishes the differences in the phenomena reported in this paper and those reported for methanol. The increase in flame stand-off ratios and fuel vapor accumulation effects as droplet size is reduced, are qualitatively the same as those reported for methanol. The gasification rates and droplet surface temperatures for heptane exhibit less variation. Heptane flame locations lie in the fuel-rich zone whereas methanol flames are located at near stoichiometric mixture fractions.

Coking-free direct-methanol-flame fuel cell with traditional nickel–cermet anode

This paper presents a systematic study of a direct-flame solid oxide fuel cell (DF-SOFC) operating on methanol and ethanol flames by SEM, EIS, I-V polarization and mass spectrometer (MS) characterizations and numerical simulation. The experimental study demonstrated that, by adopting a conventional Ni + Sm 0.2Ce 0.8O 1.9 (SDC) anode, irreversible carbon deposition and a drop of cell performance was observed when running the cell on an ethanol flame, while no carbon was deposited by operating on a methanol flame. Fuel cell stability tests indicated significant degradation in performance after 3 h of operation on an ethanol flame, while no degradation was observed after 30 h of operation on a methanol flame. A simple qualitative explanation of the difference observed in the electrochemical performance for the fuel cell operating on a methanol flame and an ethanol flame is presented based on numerical simulation.

Experimental investigation of methanol and ethanol flames in nonuniform flows

Experimental studies are conducted on extinction and autoignition of methanol and ethanol flames in laminar, nonuniform flows. Two flame types are considered: nonpremixed and premixed. The studies are performed in the counterflow configuration. The burner used in the experiments is made up of two ducts. Studies in the nonpremixed configuration are carried out by injecting a stream comprised of fuel vapors and nitrogen from one duct, and a stream of air from the other duct. In the premixed configuration a premixed-reactant stream made up of fuel vapors, air, and nitrogen, is injected from one duct, and a nitrogen stream from the other duct. Numerical calculations are performed using detailed chemistry at conditions corresponding to those used in the experiments. For the nonpremixed systems considered here, the calculated values of the critical conditions of extinction agree well with experimental data. At given values of the strain rate and temperature of the fuel stream, the calculated temperature of the oxidizer stream at autoignition is found to be higher than the measured values. In the premixed configuration the strain rate at extinction is measured for various values of the equivalence ratio of the mixture in the premixed-reactant stream, ϕ 1. The value of ϕ 1, at which the calculated extinction strain rate is the highest, is found to be larger than the value of ϕ 1 at which the measured extinction strain rate is the highest. Sensitivity analysis is carried out to test the influence of various elementary reactions on critical conditions of extinction. The structure of a nonpremixed methanol flame is investigated. Concentration profiles of stable species and temperature profiles are measured. The flame structure is calculated using detailed chemistry. The results of numerical calculations agree well with experimental data.

The prediction of flame heights and flame shapes of small fire whirls

This paper adds vortex flows around Burke–Schumann diffusion flames to predict the flame heights and the flame shapes of small fire whirls. The resulting model matches the measurements of methanol flames in a previous laboratory experiment and the results of numerical calculations in this paper. Burgers Vortex is assumed inside the vortex core radius, while ideal flow is assumed outside the vortex core radius. The ideal flow is corrected for the viscosity changes inside and outside the flame. If the two vortices are combined, they can be approximated as a Sullivan Vortex. Both the experiments and the numerical calculations show that vortex flows stabilize the flame shape, allowing the flame height as defined in a regular diffusion flame to increase. In fact, regular diffusion flames chop off unburned fuel to form separate plumes. With vortex flow, the flame stretches as if the diffusion rate had been reduced. We adjust Roper’s flame height equation to account for the vortex flow and find that the flame height depends on the volume fuel rate and the vortex core radius. If more flows than that required to stabilize the flame were supplied, the radial flows start reducing the flame diameter near the pan, which in turn is balanced by an increase in the volume fuel rate. In the experiment, a balance between the flame temperature, the volume fuel rate, and the flame shape explains why the flame height stops increasing with vortex flows after a fire whirl is generated. In the numerical calculations, we find that the temperature gradient above the port, which controls the fuel evaporation rate, increases with the vortex flows.

1080 PUBLICATION Surgical treatment craniofacial malignant tumors

The combustion of methanol was studied in a conical methanol—oxygen flame of fuel-lean composition (equivalence ratio φ = 0.25) burning at atmospheric pressure surrounded by a flowing argon shield. Oxygen bubbled through liquid methanol contained in two gas saturators provided a premixed flame of excellent stability and reproducibility. The flame gas was sampled into a mass spectrometer which was used to detect a variety of naturally occurring ionic species, both positive and negative. Although the maximum level of ionization in this flame had the rather low value of 5 × 108 ions ml−1, nevertheless concentration profiles were drawn as a function of distance along the flame axis at 17 individual mass numbers (m/z) for positive ions and 11 for negative ions; that is, whenever an appreciable signal could be detected below 100 amu. The positive profiles in the reaction zone are dominated by proton transfer processes which indicate that CHO+ is the primary ion. A variety of protonated combustion intermediates and products were detected including both stable molecules (H2O, HCHO, the CH3OH fuel, CH2CO, CH3CHO, HCOOH and possibly CH3OCH3/C2H5OH) and radicals (C, CH, CH2, HCO, CH2OH or CH3O, CH3CO or CH2CHO, and possibly CH3OO). Chemical ionization by charge transfer is certainly operative for two species (O2 and NO as an impurity) and perhaps others (CH3, O). As far as the negative ions are concerned, a number of species can be ionized in the reaction zone by three-body electron attachment and subsequent charge transfer processes (O2 initially, and then O, OH, HO2, HCOO and possibly HCOOO). Some of these negative ions are sufficiently strong bases to abstract protons from other species in proton transfer reactions (CH3OH, possibly H2O2, HCOOH, and perhaps the peroxidic intermediates HCOOO and HCOOOH). The remaining negative ions detected can be interpreted as cluster ions (OH− · H2O, HO2− · O2 or HO2− · CH3OH, CHO3− · H2O). All of this ion chemistry was compared with that observed previously for an analogous fuel-lean methane—oxygen flame. Many similarities were noted, particularly downstream, for both positive and negative ions. However, the combustion path leading to formic acid is more prominent in the methanol flame.

Hydrogen production from rich combustion in porous media

This paper examines rich combustion of methanol, methane, octane and automotive-grade petrol inside inert porous media in an effort to examine the suitability of the concept for hydrogen production. Species concentrations were measured and operating limits were tested of steady rich flames stabilized inside a two-layer alumina foam burner and a two-layer alumina bead burner. Using a conversion efficiency based on lower heating values, up to 56% of the methanol was converted to syngas (H 2, CO) inside the alumina foam burner and 66% inside the alumina bead burner. Using the same efficiency definition, 45% percent of the methane and 36% of the octane and petrol was converted to syngas with a significant portion of the energy remaining trapped in CH 4, C 2H 2 and C 2H 4. For methanol, the highest equivalence ratio observed for stable combustion was 6.1 inside the foam burner and 9.3 inside the bead burner which are higher than the conventional upper flammability limit (UFL) of 4.1. Methane's UFL was increased to 1.9 and, at a minimum, the conventional upper flammability limits of iso-octane and petrol were attained. A wide operating envelope was observed, which allowed for large turndown ratios up to 20:1. The composition of the products of the methanol flames examined here were close to equilibrium for relatively low equivalence ratios, while those of hydrocarbon flames differed significantly from equilibrium for all φ suggesting that finite rate kinetics are important. The high conversion efficiencies, quick startup times, compact size, and the absence of a catalyst make the present burner suitable for consideration as part of a reformer in a fuel cell powered automobile.