Laminar Burning Velocities Of Hydrogen Research Articles

Quenching characteristics and mechanism of hydrogen-air mixtures by corrugated plate flame arrester under inert conditions

In this study, the flame quenching performance of flame arresters under the inerting conditions for existing pipeline of hydrogen refueling station is investigated. The critical concentration of inert gas and the critical flame quenching velocity of hydrogen explosion are obtained. The results show that hydrogen explosion overpressure decreases significantly with the increase in flame arrester thickness or decrease in porosity. Furthermore, the presence of flame arresters significantly reduces the inert gas concentration required to achieve the flame quenching effect. For the same flame quenching effect, the amount of CO2 used is less than that of N2. The laminar burning velocity of hydrogen at different inert gas concentrations is calculated and the sensitivity analysis is performed. It is found that the poor combustion state is more sensitive to N2 inerting. Considering the inerting effect of inert gas on hydrogen explosion, the flame quenching criterion is modified. The flame quenching temperature of hydrogen under different critical concentrations of inert gas and parameters of corrugated plate of flame arrester is calculated. It is found that the quenching temperature of hydrogen is approximately 1500 K. The moderation effect of inert gas and corrugated plate flame arresters on hydrogen explosion are mutually enhancing. In summary, smaller porosity leads to higher fluid–solid heat transfer efficiency; smaller critical concentration of inert gas, and higher quenching temperature.

Study on the inhibition of hydrogen explosion pressure and flame propagation by trifluoroiodomethane

A 20L spherical device and a schlieren system were used to study the suppression effect of CF3I on the hydrogen explosion pressure and flame characteristics. The results show that CF3I can promote and inhibit the pressure parameters of hydrogen under lean fuel, but only inhibit the pressure parameters of hydrogen under equivalence ratios and rich fuel. Such as, φ = 0.6, adding 10 % CF3I, the maximum explosion pressure increased by 8.8 %. φ = 1, adding 5 % CF3I, the maximum explosion pressure decreased by 25 %. Different from the explosion pressure, the laminar burning velocity of hydrogen with different equivalence ratio decreases gradually with the increase of CF3I concentration. Numerical simulation was used to reveal the mechanism of CF3I inhibiting hydrogen. The results show that the concentration of active free radicals(H, O, OH) decreases with the increase of trifluoroiodomethane concentration. Further analysis on the rate of production and sensitivity of H free radicals found that R822 and R839 are the main generation reactions of H free radicals in the fluorine- and iodine-containing elemental reactions, and R1397, R1396, R1391 and R859 are the main consumption of H free radicals reaction. The elementary reaction with the greatest inhibitory effect on H free radicals is R1391, and the elementary reaction with the greatest promoting effect is R850.

Flameless venting characteristics of hydrogen explosion under the coupling of carbon dioxide and metal foam

To avoid the hazards of vented flame and external explosion caused by hydrogen-air explosion venting, the effects of metal foam and carbon dioxide on the characteristics of vented flame, reduced overpressure, and external pressure are investigated. The results indicate that a combination of inerting (such as adding CO2) and venting technology is recommended to achieve the quenching of vented flames without increasing the reduced overpressure of hydrogen explosions. The effect of the thickness of metal foam and the concentration of CO2 on the length of vented flame is significant, but it only has a minor impact on the width. The laminar burning velocity of hydrogen decreases with the increase of the volume ratio of CO2, which weakened the chemical reaction and reduced overpressure and explosion severity (KG). The characteristics of the external explosion are revealed with the assistance of BOS images. When the venting diameter is 80 mm, the flameless venting efficiency is approximately at 53.33%. Finally, the criterion for heat transfer quenching of vented flames is discussed. The quenching mechanism during flameless venting of hydrogen explosions is analyzed, providing a basic reference for the safety design of hydrogen explosion protection.

Manipulating hydrogen oxy-combustion through carbon dioxide addition

Hydrogen (H2) is increasingly viewed as an attractive carbon-free fuel due to its potential compatibility with the existing transportation and conversion infrastructure. However, one of the major challenges facing large-scale deployment is the fundamentally different combustion properties it has in comparison to commonplace hydrocarbon fuels such as natural gas. For example, the laminar burning velocity (LBV) of a combustible mixture has a direct impact on how it can be used in internal combustion engine or gas turbines; the LBV of hydrogen is over 7 times greater than that of natural gas when combusted in air. Carbon dioxide (CO2) can be used as a working fluid, as opposed to nitrogen (in air), to reduce the flame speed of hydrogen combustion. A mixture of hydrogen, oxygen, and carbon dioxide as a working fluid can provide LBVs comparable to natural gas in air, which potentially enables existing conversion architectures. Furthermore, by replacing nitrogen (N2) with CO2 in the mixture, NOx emissions are avoided and opportunities for carbon sequestration or closed-cycle processes are possible. This study experimentally explores fundamental premixed oxy-combustion properties of H2-CO2 mixtures in a constant volume combustion chamber (CVCC) across a range of initial pressures (1, 1.5, and 2bar) and equivalence ratios (0.4, 0.6, 0.8, and 1). The spherically expanding flames are examined to determine the flame speed, LBV, and lower flammability limits (LFL) with respect to different CO2 concentrations (40%, 60%, 65%). Furthermore, at an initial pressure of 1bar and stoichiometric conditions, it was found that the flame speed of the 65% CO2 case was lower than that of CH4-air combustion.

Numerical analysis of laminar burning velocity of hydrogen and carbon monoxide-enriched natural gas (HyCONG) blends

Numerical analysis of laminar burning velocity of hydrogen and carbon monoxide-enriched natural gas (HyCONG) blends

Laminar burning velocity of hydrogen, methane, ethane, ethylene, and propane flames at near-cryogenic temperatures

The primary objective of this study is to measure the laminar burning velocity of perfectly premixed hydrogen-air, methane-air, ethane-air, ethylene-air, and propane-air flames, at near-cryogenic temperatures and atmospheric pressure. Initial fuel-air mixture temperatures as low as 160 K were investigated. The experimental methodology was validated by comparing the results obtained with those from previous studies available in the literature and with numerical simulations using five different chemical mechanisms. First, for all fuels, the laminar burning velocity evolution as a function of the equivalence ratio followed the same trend at 295 K and 240 K. Regardless of the equivalence ratio and mixture composition, the laminar burning velocity decreased by 22 to 44% for hydrogen, methane, ethane, ethylene, and propane flames when the temperature was decreased from 295 K to 240 K. Second, for stoichiometric conditions, the laminar burning velocity decreased by about 50% for all fuels, when the temperature was decreased by 100 K, from 295 to 195 K. These experimental results were in excellent agreement with laminar burning velocities calculated by a power law of the ratio of unburned gas temperature to ambient temperature, with exponent values from the literature, obtained for temperatures above the ambient. All five chemical mechanisms provided a very good agreement, within or near experimental uncertainties, for most of the fuels and conditions investigated, even at low temperatures. Overall, this study provides valuable information on the laminar burning velocities of various hydrocarbon and hydrogen fuels at near-cryogenic temperatures, which can be useful for the design of cryogenic storage systems and the validation of chemical kinetic models for conditions below ambient temperatures.

Development of a CFD-Suitable Deep Neural Network Model for Laminar Burning Velocity

Hydrogen is a valued resource for today’s industry. As a fuel, it produces large amounts of energy and creates water during the process, unlike most other polluting energy sources. However, the safe use of hydrogen requires reliable tools able to accurately predict combustion. This study presents the implementation of a deep neural network of laminar burning velocity of hydrogen into an open-source CFD solver flameFoam. DNN was developed based on a previously created larger DNN, which was too large for CFD applications since the calculations took around 40 times longer compared to the Malet correlation. Therefore, based on the original model, a faster, but still accurate, DNN was developed and implemented into flameFoam starting with version 0.10. The paper presents the adaptation of the original DNN into a CFD-applicable version and the initial test results of the CFD–DNN simulation.

Laminar Burning Velocity of Hydrogen, Methane, Ethane, Ethylene, and Propane Flames at Near-Cryogenic Temperatures

Laminar Burning Velocity of Hydrogen, Methane, Ethane, Ethylene, and Propane Flames at Near-Cryogenic Temperatures

Laminar burning velocity of hydrogen and carbon-monoxide enriched natural gas (HyCONG): An experimental and artificial neural network study

The laminar burning velocity of H2 and CO enriched natural gas (HyCONG) mixtures measured through spherically expanding flames method under three different fuel-air equivalence ratios (0.6, 0.8, and 1.0) at room temperature and atmospheric pressure. Experiments have been conducted into constant volume combustion chamber by using high-speed schlieren photography technique. The five different CO fraction (0%, 20%, 40%, 60%, and 80%) and three HCNG (0%, 20%, and 40%) blends combinations are selected for the experiments. The laminar burning velocity and Markstein length were obtained for 45 operational conditions. The results reveal that the laminar burning velocity increases drastically with an increase of hydrogen and carbon monoxide in HyCONG blends and increasing fuel-air equivalence ratio. The maximum laminar burning velocities are determined as 24.42 cm/s, 45.7 cm/s, and 62.78 cm/s for 20–80 HyCONG at ϕ = 0.6, 40–60 HyCONG at ϕ = 0.8, and 40–60 HyCONG at ϕ = 1.0 respectively. Additionally, the artificial neural network model (ANN) of combustion chamber has been constructed to predict the laminar burning velocity of HyCONG blends. The ANN’s well known backpropagation algorithm is applied in multilayered feedforward networks. The forecasting of laminar burning velocity has been evaluated using four-input and one-output network structure with two different learning algorithm namely: Levenberg-Marquardt (LM) algorithm and Scale Conjugate Gradient (SCG) algorithm. The four-input parameters considered as; fuel-air equivalence ratio, hydrogen fraction, methane fraction, and carbon monoxide fraction while output parameter is laminar burning velocity. The model training has been accomplished using hyperbolic tangent transfer activation function (tansig) and various number of neurons.The maximum and minimum value of correlation coefficient (R) and mean square error (MSE) for validation were obtained for laminar burning velocity. The values of R (max-min) and MSE (max-min) are 0.9987–0.9944 & 2.1305–1.0195 for Levenberg-Marquardt (LM) algorithm and 0.9990–0.9952 & 2.7965–0.9501 for Scale Conjugate Gradient (SCG) algorithm. Presented article not only provides the experimental study of LBV as well as explores the possibility of artificial neural network application in combustion research area.

Effect of inert species on the laminar burning velocity of hydrogen and ethylene

The maximum laminar burning velocity (LBV) of a fuel-air mixture is an important input parameter to vapor cloud explosion (VCE) blast load prediction methods. In particular, the LBV value has a significant impact on the predicted blast loads for high reactivity fuels with the propensity to undergo a deflagration-to-detonation transition (DDT). Published data are available for the maximum LBV of many pure fuel-air mixtures. However, little test data are available for mixtures of fuels, particularly for mixtures of fuels and inert species. Such mixtures are common in the petroleum refining and chemical processing industries. It is therefore of interest to be able to calculate the maximum LBV of a fuel/inert mixture based on the mixture composition and maximum LBV of each component.This paper presents measured test data for the maximum LBV of H2/inert and C2H4/inert mixtures, with both nitrogen and carbon dioxide as the inert species. The LBV values were determined using a constant-volume vessel and the pressure rise method. This paper also provides a comparison of the measured LBV values with simplified LBV prediction methods.

Experimental and Computational Determination of LBV of Hydrogen Enriched Methane Mixtures

One of the major causes of environmental pollution and ozone layer depletion is the emissions coming out of the combustion devices including industrial burners, automobile vehicles and household appliances. Most of the conventional fuels used now days have high GWP and ODP. So the greatest challenges among the combustion researchers and scientists are to develop some sustainable and non conventional sources of energy that possesses capability to replace the conventional ones. One of the important gaseous fuels in non conventional category is hydrogen, which is a cleaner fuel and reduces pollution enormously. In the present work, experimental and computational analysis of laminar burning velocity (LBV) of premixed gaseous fuels (primary focus on Hydrogen enrichment) was carried out. For experimental investigation the experimental set up available in Fuel and pollution lab of Indian Institute of Technology Delhi is used. Experiments were carried out on mixtures of methane- Air and Methane-Hydrogen-Air for wide range of equivalence ratios and compared with the computational results of PREMIX with full GRI-Mech 3.0 mechanism. Most of the experiments available in literature were carried out at 298 K. In the present work it has been tried to relate the effect of low temperatures on laminar burning velocity of mixtures. The experiments have been conducted at 1 bar pressure and around 292 Kelvin with equivalence ratio ranging from 0.8 to 1.2. Methane gas is enriched with hydrogen in varying proportions and the effect of hydrogen enrichment on its laminar burning velocity studied. The objective of the addition of hydrogen to methane was to increase its laminar burning velocity as well as to extend its lean flammability limits at lower ambient temperatures.

A numerical modelling of an influence of CH 4, N 2, CO 2 and steam on a laminar burning velocity of hydrogen in air

The influence of additives of various chemical natures (CH 4, N 2, CO 2, and steam) at a laminar burning velocity S u of hydrogen in air has been studied by numerical modelling of a flat flame propagation in a gaseous mixture. It was found that the additives of methane to hydrogen–air mixtures cause as a rule monotonic reduction in the S u value with the exception of very lean mixtures (fuel equivalence ratio ϕ = 0.4), for which a dependence of the laminar burning velocity on the additive's concentration has a maximum. In the case of the chemically inert additives (N 2, CO 2, H 2O) the laminar burning velocity of rich near-limit hydrogen–air flames drops monotonically with an increase in the additive's content, but no more than 1.5 times, and the adiabatic flame temperature changes slowly in this case. In the case of methane as the additive, the laminar burning velocity is diminished approximately 5 times with an increase in the adiabatic flame temperature from 1200 to 2100 K. Deviations from the known empirical rule of the approximate constancy of the laminar burning velocity for near-limit flames are shown.

Laminar burning velocity of hydrogen–methane/air premixed flames

The laminar burning velocities of hydrogen–methane/air mixtures at NTP conditions were calculated using the CHEMKIN PREMIX code with the GRI kinetic mechanism. The equivalence ratio and the fuel composition were varied from lean to rich and from pure methane to pure hydrogen, respectively. The results show that the values of the blends laminar burning velocities are always smaller than those obtained by averaging the laminar burning velocities of the pure fuels according to their molar proportions. Moreover, in lean mixtures the hydrogen addition enhances the methane reactivity slightly, while a strong inhibiting effect of the hydrogen substitution by methane is observed at rich conditions. These findings are attributed to changes of both, the H radicals concentration and the reactions involving such atoms. It was attempted to correlate the calculated laminar burning velocities by means of a Le Chatelier's Rule-like formula. A good prediction is obtained, except for rich mixtures with high hydrogen contents. With this limitation, the proposed formula is successfully applied also to mixtures at higher than normal values of initial pressure (up to 10 atm) and temperature (up to 400 K).

Laminar burning velocities in stoichiometric hydrogen and hydrogenhydrocarbon gas mixtures

Measurements of the laminar burning velocities of hydrogen, acetylene, propane, and methane have been made using a spherical combustion bomb. In addition measurements were also made for mixtures of hydrogen with acetylene, propane, methane, and simulated combustion products in various proportions. All mixtures were stoichiometric with air and pressures and temperatures ranged from 0.5 to 7 atm and 300 to 550K, respectively. The values for the pure gases were in good agreement with previous experimental results from combustion bombs and in reasonable agreement with theoretical calculations by Warnatz. When mixed with hydrogen, propane and methane exhibited a double peak behavior in the burning velocity, as a function of pressure along an unburned gas isentrope.