This study focuses on the combustion behaviours of low calorific value coal gases containing additions of hydrogen. The main goal of the present study is to improve combustion performances of low ...calorific value coal gases by enriching hydrogen. Investigations have been numerically performed by using a CFD code. PDF/Mixture Fraction Model has been used as combustion model. Moreover, k-Ɛ realizable turbulence model has been selected as turbulence model because of capturing better results with the experimental results. Before the low calorific value coal gases are consumed by enriching hydrogen, the methane, which is a major component of natural gas, has been burned as the baseline fuel to verify predictions. The predicted temperature profiles of the methane flame are compared with the experimental results and these predictions are in good agreement with the measurements from the literature. Then, the low calorific value coal gases are enriched by hydrogen from the same fuel inlet stream by volume and the hydrogen-enriched low calorific value coal gases have been modelled in the combustor. According to the predictions, combustion characteristics of hydrogen-enriched low calorific value coal gases have been improved considerably as the coal gases are enriched by hydrogen. Although, the NOX levels are slightly increased as the hydrogen is added to coal gases.
•Hydrogen-enriched low calorific value coal gases have been consumed.•Combustion model used in this study is the Mixture Fraction/PDF Model.•NOX post-processor has been used to predict NO formation.•Axial and radial distributions have been shown.
Solid oxide fuel cells (SOFCs) transform the energy of the fuel instantly into electric energy with a large fuel option. Coal, which is a local energy source, is a preferred fuel despite its negative ...features because it is cheap and abundant. The use of coal and coal-based fuels in SOFCs has recently attracted considerable attention. In this study, performance analysis of the SOFC has been performed experimentally by using hydrogen, generator gas (contained 12% H2), and water-gas (contained 50% H2) in an electrolyte-supported SOFC (ES-SOFC). The numerical modelling of the fuel cell had been previously performed. In addition, the effect of inlet gas fuel flow rates on the ES- SOFC has been investigated numerically in this study. The temperature effect on the performance of ES-SOFC has been examined experimentally. It is seen that the performance of SOFCs fueled hydrogen is favorable than fueled water gas and generator gas. This is because of the higher hydrogen substance in the water gas measure against the other gas. In addition, it is seen that the increase in temperature increases the performance with positive effects on the reactions. It is also concluded that the performance of SOFC increases when inlet fuel flow rates increase.
•The effect of using coal gas as fuels on the cell performance experimentally.•The high hydrogen content improves SOFC performance.•The increasing temperature increases the performance of SOFC.•The inlet fuel flow rates increase the performance of SOFC increase.
Solid oxide fuel cell (SOFC) is a device that produces electricity directly from oxidizing a fuel. Some of the advantages are operating at high temperatures and converting various hydrocarbon fuels ...directly into electricity. This study investigates the parameters that influence the cell characteristics of a cathode-supported SOFC (CSSOFC) model. Numerical modeling has been performed utilizing low calorific value coal gases, generator gas, and water gas by deriving an SOFC model based on finite element method (FEM). The effects of fuel compositions, temperature, pressure, and porosity on the performance of the developed SOFC have been examined using COMSOL software. These effects are presented by polarization and power curves. A mathematical model has been developed to determine the performance of a CSSOFC with low calorific value coal gases that were obtained from Turkey/Turk coal. It is predicted that the performance of CSSOFC is higher than that of the electrolyte-supported SOFC (ES-SOFC) for all studied fuels. Besides this, the cost of the cathode supporting materials for high-performance CSSOFC is low. The performance of SOFC using water gas is higher than that of the generator gas. This being maybe the hydrogen content of the water gas is higher compared with the generator gas. Therefore, the result confirmed that low calorific value coal gases could be used in SOFCs as a source of fuel. Moreover, the power of the CSSOFC increases as the pressure, temperature, and hydrogen content increase.
•The numerical modeling of a SOFC fed by coal gases has been performed.•It has been proved that the coal gases can be used on SOFC as fuels.•The increasing temperature, pressure and porosity increase the SOFC performance.•The increasing hydrogen amount in the fuel increase the SOFC performance.•The cathode-supported SOFC outperforms the electrolyte-supported SOFC.
This paper deals with the effect of the swirl number (0–0.8) on combustion characteristics of hydrogen-containing fuel blends in a gas-fired combustor. The present study is a numerical study that has ...been performed by using a commercial CFD (computational fluid dynamics) code. Selection of coherent combustion model is very important for more accurate prediction in the reactive modelling. Because of that, the PDF/Mixture Fraction combustion model has been selected due to better capturing the experimental results and is preferable for blending fuels. The other mathematical models used in this study are k−Ɛ realizable turbulence model of turbulent flow and P−1 radiation model. Methane as baseline fuel has been modelled to verify the predictions. It is shown that predictions are in good agreement with the existing experimental data. Then, the hydrogen-containing fuel blends have been modelled to find out the effect of the swirl number on combustion characteristics of these fuels with five different swirl numbers from 0 to 0.8 at interval of 0.2. It is concluded that the flame temperatures are highly affected depending on changes of the swirl number. Because, tangential velocity of the air stream changes the temperature distribution in the combustor considerably. It is also demonstrated that changes in swirl number lead to position of the high NOX regions.
•The effect of the swirl number on combustion characteristics of hydrogen-containing fuels has been investigated.•Model validation has been performed.•Temperature and NOX distributions are shown.
Increasing energy need and running out of fossil-based fuels direct us to renewable energy resources. Although hydrogen is not an energy source by itself, it is an energy carrier with a high specific ...heat capacity. As it is used as fuel in unitized regenerative PEM fuel cells, water is separated in electrolyzer mode and stored by producing hydrogen when there is no need for energy. In this study, performance tests on the unitized regenerative PEM electrolyzer/fuel cell were carried out and numerical modelling has been performed. The validity of the developed model was confirmed by the results of the experimental study. Before starting the performance tests, the cell's leakproofness tests were carried out, and the appropriate torque force was optimized, reducing the contact resistance that causes performance loss. The material selection of the cell components and corrosion-resistant materials that can operate in both electrolyzer and fuel cell modes were preferred.
In this study, 0.019 slpm of hydrogen and 0.0095 slpm of oxygen gas is produced in the electrolyzer mode, while a power density of 0.353 W/cm2 is obtained in the fuel cell mode at 80 °C, from a unitized regenerative PEM fuel cell with a 5 cm2 active area, whose cell elements are combined with a 3 Nm clamping torque by using 12 bolts.
•Three dimensional two phase flow modelling of regenerative PEM FC was performed.•Working parameters of unitized regenerative PEM fuel cell were optimized.•The developed model was verified by comparing the experimental and numerical results.•An increase in cell performance was achieved for both modes.
This study concentrates on the 3D numerical modelling of combustion of different biogases in a generated burner and combustor. The main goal of this study is to investigate the combustion ...characteristics (such as temperature and emissions) of biogases through a combustor due to depletion of natural gas. Moreover, the effect of the preheated air on flame temperatures of biogases have been studied in the present study. Finally, the effect of H2S amount in biogas on SO2 emissions has been investigated within these predictions. The numerical modelling of turbulent diffusion flames has been performed by using the standard k–ε model of turbulent flow, the PDF/Mixture Fraction combustion model and P-1 radiation model in the combustor. A CFD code has been used for all predictions. Temperature gradients have been determined on axial and radial directions for better understanding combustion characteristics of biogases. Modelling has been studied for thermal power of 10 kW and excess air ratio of λ = 1.2 for each biogas combustion. The first finding is that combustion of biogases is possible via the newly generated burner. Moreover, the results show that the one of biogas is very close to methane in terms of temperature distributions in the combustor due to including high amount of methane compared to other biogases. It is also concluded that the flame temperatures of biogases increase with preheating the combustion air as expected. It is finally revealed that SO2 emissions increase as amount of H2S in biogas is increased through the combustor.
•The newly generated burner has been described in detail.•The PDF/Mixture Fraction combustion model, standard k-Ɛ turbulence model and P-1 radiation model have been used.•Temperature and emission distributions of the biogases have been obtained.•The effects of the preheated air and H2S amount in the biogases have been investigated.
This study discusses numerical study of premixed hydrogen flames in confined/unconfined combustors. Within the scope of this study, combustion performances and emission characteristics of premixed ...hydrogen combustion have been performed by using a CFD Code. Modellings were implemented by changing excess air ratios from 0.8 to 1.7 for fixed heat input of 50 kW. Moreover, investigations were conducted in two different combustors (confined/unconfined) for better understanding of hydrogen combustion. According to the results, the maximum temperature distribution was emerged as about 2000 K in confined combustor. Although the maximum temperature value increases with increasing the excess air ratio until stoichiometric condition, the maximum temperature value decreases as the excess air ratio is increased after stoichiometric condition. Besides, simulation results were compared with experimental datas from the literature (diffusion flames). This comparison reveals that the general trend of the axial temperature profiles are in good agreement with the measurements.
•CFD Modelling of premixed hydrogen flames in confined/unconfined combustors was performed•Combustion model used:Reaction rate in turbulent flow is calculated from Arrhenius kinetic rate expression and the eddy break-up model which are given asThe Arrhenius reaction rate expression:Ri1,k=−vi′,k′Mi′TβkAk∏j′Cj′vj′,kexp(−EkRT)The eddy break-up reaction rate:Ri1,k=−Cρ(−εK)∑i′mi′vi,k1•NOX post-processingA NOX post-processor has been used to predict NO formation from the hydrogen combustion.•Results and discussions-Model validation-Temperature and NOX predictions-The effect of the combustor types-The effect of varying excess air ratios•ConclusionIn this study, numerical investigation of premixed hydrogen flames has been performed for 50kW heat input and varying excess air ratios in confined/unconfined combustors.
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