Effect Of Hydrogen Addition Research Articles

An Assessment of Hydrogen Addition to Methane Combustion with Argon as a Working Fluid in a Constant Volume Combustion Chamber

ABSTRACT Combustion of natural gas in combination with hydrogen, coupled with argon as a working fluid, is a promising approach to increasing the efficiency of internal combustion engines while decreasing emissions. The use of argon as a working fluid effectively eradicates NOx, extends the flammability limits, and increases the thermal efficiency due to its high specific heat ratio. Additionally, the hydrogen addition aids in emissions reduction and enhances the flammability range. In this study, premixed CH4-H2-O2-Ar combustion is experimentally investigated in an optically accessible constant volume combustion chamber to determine the effect of hydrogen addition on laminar burning velocity, flame morphological structure, and instabilities when argon replaces nitrogen as the working fluid. A numerical thermodynamic model is applied to calculate the laminar burning velocity and an image processing technique is used to quantify the flame speed. The experiments show that, in comparison to methane alone, the addition of hydrogen (40%) to the mixture at atmospheric pressure (1 bar) and room temperature (298 K) increases the maximum laminar burning velocity by 37%, increases the maximum flame speed by 35%, and extends the lower and upper flammability limits from equivalence ratio of 0.4 to 0.3 and 1.6 to 1.7, respectively.

Experimental Investigation on the Effect of Hydrogen Addition on the Sooting Limit and Structure of Methane/Air Laminar Counterflow Diffusion Flames

Experimental Investigation on the Effect of Hydrogen Addition on the Sooting Limit and Structure of Methane/Air Laminar Counterflow Diffusion Flames

Effect of hydrogen addition in diesel/natural gas dual-fuel combustion with late injection

In a previous work, the effectiveness of late pilot injection on improving combustion behaviour – in terms of fuel conversion efficiency and pollutant emission levels – in a diesel/natural gas dual-fuel engine was assessed. Then, an additional set of experiments was performed, aiming at speeding up the combustion process possibly without penalizing NOx levels. Therefore, hydrogen was added to natural gas in a percentage equal to 10%. Results show that hydrogen addition has a significant effect on the combustion development specially during the early stage of combustion: ignition delay is shortened and combustion centre is advanced, while the combustion duration increases when pilot injection timing is set to conventional values, while remains basically unchanged for late timings. Fuel conversion efficiency is only slightly penalized when hydrogen is added. Moreover, it was confirmed that, in general, combustion strategy with late pilot injection timing does not penalize fuel conversion efficiency; indeed, in some cases, it actually increases. Concerning regulated emission levels, it is again proven that late pilot injection does not penalize pollutant production: the hydrocarbons and carbon monoxide reduce as pilot injection is delayed, probably due to the higher temperatures reached into the cylinder during most part of the expansion stroke. Moreover, adding hydrogen always reduces their levels. Concerning NOx, they are drastically reduced delaying pilot injection; as expected, hydrogen addition promotes NOx formation, but the increase, evident with conventional pilot injection timings, becomes marginal with late injection strategy. Therefore, combustion strategy performance with late pilot injection in dual-fuel diesel/natural gas combustion conditions can be further improved with 10% hydrogen addition to natural gas.

Experimental investigation of performance and emissions of CRDI diesel engine in dual fuel mode by hydrogen induction and diesel injection coupled with exhaust gas recirculation

IC engines are the main resources of power in our daily life particularly in transportation, agricultural sectors and power generation. However, faster depletion of petroleum resources and environmental issues raised because of abundant use of it and are the driving force behind the search for replacement of petroleum products with newer reliable alternate fuels. In this point of view, hydrogen is the most promising alternate fuels because of its cleaner combustion characteristics to resolve the earlier stated issues as being the best renewable energy resource. In the current research work, the supplementary fuel used is hydrogen which was injected inside the intake manifold by solenoid type of hydrogen injector whereas diesel is directly injected inside the engine cylinder. The prime intention of current work is to replace the diesel energy share with hydrogen energy in single cylinder CRDI equipped diesel engine and reduction of Oxides of Nitrogen emission which was resulted due to maximum hydrogen energy share during combustion at higher flow rate using exhaust gas recirculation technique. The experimentation was carried out on single-cylinder 4 S water cooled CRDI equipped engine. The effect of hydrogen addition with use of various flow rates of exhaust gas recirculated on engine performance along-with emission parameters were investigated at different loading conditions of engines. The hydrogen enriched dual fuel mode of operation together with exhaust gas recirculation technique resulted in improved performance as well as emissions factors of CRDI diesel engine in comparison with neat diesel except NOx which could be further reduced by cooled maximum mass flow rate of EGR which can be employed is suggested.

Numerical study of the lean premixed PRECCINSTA burner with hydrogen enrichment

Hydrogen combustion is one of the most promising solution to achieve a global decarbonization in power production and transports. Pure hydrogen combustion is far from becoming a standard but, during the energy transition, hydrogen co-firing can be a feasible and economically attractive shortterm measure. The use of hydrogen blending gives rise to several issues related to flashback, NOx emissions and thermo-acoustic instabilities. To improve the understanding of the effect of hydrogen enrichment, herein a numerical analysis of lean premixed hydrogen enriched flames is performed by means of 3D unsteady CFD simulations. The numerical model has been assessed against experimental results for both cold and reacting flows in terms of velocity profile (average) and flame shape (mean OH* radical fields). The burner under investigation is the swirl stabilized PRECCINSTA studied at the Deutsches Zentrum für Luft-und Raumfahrt (DLR). The DLR’s researchers have shown the effect of hydrogen addition on the flame topology and combustion instabilities at various operating conditions in terms of thermal power, equivalence ratio and H2 volume fraction. Simulations are in good accordance with experimental data both in terms of velocity and temperature profiles. The numerical model provides a qualitative estimation of the flame shape.

Effect of hydrogen additions to shielding gas on activated TIG austenitic stainless steel weld

In tungsten inert gas (TIG) welding, less penetration depth is achieved in a single pass which adversely affects productivity, Activated TIG (A-TIG) welding techniques achieve better performances and higher penetration depths compared to conventional TIG welding. Pure argon does not have the potential to provide adequate penetration in austenitic stainless steel. Argon–hydrogen shielding gas mixture provides high heat flux, thereby influencing the arc voltage and penetration. In the present study, hydrogen is added to base shielding gas argon to study the effect on weld geometry during TIG and A-TIG of 310S stainless steel. The result shows a higher weld depth to width ratio and a significant reduction in the angular distortion. Also, higher tensile strength is obtained in A-TIG weld metal with 1% hydrogen addition, due to more efficient cooling of the weldment. However, increasing the hydrogen concentration in shielding gas resulted in defect formations in the weldment due to the interaction between activated flux and the hydrogen.

Effects of hydrogen addition into liquefied petroleum gas reductant on the activity of Ag–Ti–Cu/Cordierite catalyst for selective catalytic reduction system

In this study, low temperature activity of Ag–Ti–Cu/Cordierite catalyst was investigated with liquefied petroleum gas (LPG) and hydrogen-liquefied petroleum gas (H2-LPG) mixture as reductant. The selective catalytic reduction (SCR) catalyst was synthesized by impregnation method and characterized by Brunauer-Emmett-Teller (BET), Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) analyzes. BET analysis of the catalyst revealed surface area as 12.89 m2/g. Silver (Ag), titanium (Ti) and copper (Cu) nanoparticles were observed on the catalyst surface with SEM analysis. XRD analysis showed high dispersion of catalytic elements. The SCR performance tests were carried out at 170–270 °C temperature range, 30,000 h−1 and 40,000 h−1 space velocities, 1 kW, 2 kW, 3 kW and 4 kW engine loads with diesel engine real exhaust gas sample. NOx conversion efficiency increased significantly in the presence of H2, especially at low exhaust temperatures. The maximum NOx conversion ratio was obtained as 89.53% with H2-LPG reductant at 270 °C, 4 kW engine load and 30,000 h−1 space velocity.

Effect of hydrogen addition on the structure and stabilization of a micro-jet methane diffusion flame

The micro-jet diffusion flame can act as the heat source for the micro power generation systems due to some advantages. The present work investigates the effect of hydrogen addition on the structure and stabilization of micro-jet methane diffusion flame by numerical simulation. The results show that the oval flame becomes more and more circular with the increase of hydrogen addition fraction. The addition of hydrogen remarkably suppresses the increase of the flame height with the inlet velocity. The methane sharply decreases around the outlet of the micro-jet tube due to the high fresh fuel temperature. The intermediate species (e.g., H2 and CO) increase sharply before the flame front, and they are consumed sharply within the flame front. With the increase of hydrogen addition fraction, the concentration gradients of reactive species increase before the flame front, while the flame temperature decreases. In addition, with the increase of hydrogen addition fraction, the micro-jet flame root shifts toward the tube-wall and downstream direction at the radial and axial directions, respectively, and the addition of hydrogen decreases the anchoring temperature of the micro-jet flame root, which is conductive to improve the flame stabilization. Meanwhile, a large hydrogen addition fraction is detrimental for the flame stabilization in terms of the thermal interaction between the micro-jet flame and tube-wall. However, the positive effects brought by a large hydrogen addition fraction are noticeably larger than the adjunctive negative effects. This study not only provides the guideline for further expanding the operating range of the micro-jet methane diffusion flame but also helps us to gain insights into the mechanism of hydrogen addition on improving the flame stabilization.

Influence of hydrogen addition on methane coupling in a moderate pressure microwave plasma

In this paper, the effect of hydrogen addition on methane coupling in a microwave moderate pressure (55 mbar and 110 mbar) plasma reactor has been studied. The use of optical emission spectroscopy allowed the determination of the rotational temperature of heavy particles and showed it to be in the range of 3000–4000 K. Due to the high temperature in the discharge the dominant product was acetylene and it was concluded that the methane coupling process is mainly through thermal decomposition with a key role of H radicals. It was revealed that the addition of hydrogen can increase both methane conversion and acetylene and ethylene yield and selectivity. With the CH4:H2 ratio of 1:1, the methane conversion increased from 31.0% to 42.1% (55 mbar) and from 34.0% to 48.6% (110 mbar), when compared to pure methane plasma. Respectively, the yield of acetylene increased from 14.4% to 25.3% (55 mbar) and from 20.1% to 34.0% (110 mbar). Moreover, the addition of hydrogen decreased the output of the problematic soot-like product. These results indicate that hydrogen addition can be a simple yet effective method of increasing selectivity to desirable products in plasma reforming of CH4.

Experimental study of compact swirl flames with lean premixed CH4/H2/air mixtures at stable and near blow-off conditions

An experimental study on the compact lean premixed flames stabilized on a bluff-body and swirl burner is performed. The flames are featured with a strengthened Inner Recirculation Zone (IRZ). The objective is to identify the critical causes of blow-off near the lean limit. Meanwhile, the effects of hydrogen addition on the flame stabilization are also examined. Premixed CH4/H2/air mixtures are adopted with varied hydrogen fractions up to 80%. Flames far from and close to the blow-off conditions are both obtained for comparison. Simultaneous PIV/OH-PLIF measurements are performed, and flow-flame dynamics are analyzed. Results show that the flow straining near the flame root is dominant to induce the root extinction and initiate the blow-off. The strain is observed to mainly result from the shear deformation. The weakened root burning intensity is demonstrated with the CH* chemiluminescence. With hydrogen addition, the flame root is strengthened due to the enhanced resistance to the strain. The increased burning velocity and temperature with hydrogen are also beneficial for the flame stabilization. The inner shear layer vortices are anticipated to promote the blow-off by convecting cold unburned mixture into the IRZ.

Effect of hydrogen addition on compression deformation behaviour of Ti–0.3Mo–0.8Ni alloy argon-arc welded joints

The effect of hydrogen addition on compression deformation behaviour of Ti–0.3Mo–0.8Ni alloy argon-arc welded joint has been investigated. Evolution mechanism of hydrogen-induced flow stress was discussed in detail. The results show that with increasing hydrogen content, the stretching and bending extent of fully lamellar microstructures including α lamellas and acicular hydride continued to increase, the morphology of dynamic recrystallization (DRX) grains tended to change from approximately equiaxed to large lamellar shape, and the quantity of DRX grains and recrystallization degree of grains increased obviously. A large number of dislocations concentrated in the vicinity of the hydride. Steady stress was decreased continuously with increasing hydrogen content, while peak stress of the hydrogenated 0.12 wt.% H weld zone was decreased to the minimum value and then increased slowly. A slight decrease in flow stress of the hydrogenated 0.05 wt.% H weld zone was caused by limited increase in the volume fraction of softer β phase. Hydrogen-induced DRX of α phase and improved dislocation movement by strong interaction between the hydride and dislocation directly resulted in a sharp drop in flow stress of the hydrogenated 0.12 and 0.21 wt.% H weld zone. Solute hydrogen also finitely contributed to a sharp drop in flow stress of the hydrogenated 0.12 and 0.21 wt.% H weld zone by promoted local softening, which induced continuous DRX and more movable dislocations to participate in slipping or climbing. The reinforcement effect and plastic deformation of the hydride and solution strengthening of β phase induced by solute hydrogen finally led to the increase in flow stress of the hydrogenated 0.21 wt.% H weld zone in its true strain range from 0 to 0.36.

Hydrogen effects on ignition delay time of methyl butanoate in a rapid compression machine

SummaryThe effect of hydrogen addition on the ignition delay time of methyl butanoate was studied using a rapid compression machine experiment and ANSYS CHEMKIN‐PRO 19.0 numerical analysis. The ignition delay was measured under engine‐relevant conditions by varying equivalence ratios (0.5 and 1.0), compression pressures (15 and 30 bar), compression temperatures (860‐1060 K), and hydrogen mole fractions in the methyl butanoate/hydrogen mixture (0%, 25%, 50%, and 75%). The kinetic mechanism was modified by adding the methyl butanoate mechanism to the NUIG Aramco 3.0 mechanism and modifying the rate parameters of the H‐atom abstraction reactions of methyl butanoate. The numerical results obtained using the modified mechanism were in good agreement with the experimental results. The methyl butanoate/hydrogen mixture did not show a negative temperature coefficient characteristic. With hydrogen addition, the ignition delay increased at low temperatures but decreased at high temperatures. The results of the chemical and dilution effect analysis using the imaginary inert H2 showed that the chemical effects differ depending on the temperature. Most added hydrogen molecules participate in the chain propagation reactions to produce H radicals and consume OH by the reaction H2 + OH → H + H2O. This, in turn, changes the reactions of other species, such as HO2 and H2O2. The results of the reaction path analysis for the related species showed that the addition of hydrogen reduced radical reactions at low temperatures, while increasing them at high temperatures.

Effect of hydrogen blending on the high temperature auto-ignition of ammonia at elevated pressure

To understand the effect of hydrogen addition on the auto-ignition of ammonia at high temperatures, ignition delay times of stoichiometric ammonia/hydrogen blends were measured in a shock tube at temperatures from 1020 to 1945 K, pressures of 1.2 and 10 atm, and hydrogen fractions from 0% to 70%. The measured ignition delay times were compared with seven available kinetic models. Chemical kinetic analyses were performed using both the Glarborg Model and Otomo Model to interpret the interactions between ammonia and hydrogen during the high temperature auto-ignition. Experimental results show that ammonia ignites slower than hydrogen, and hydrogen addition can reduce the ignition delay time nonlinearly. The numerical analysis identifies that 5% hydrogen addition does not significantly affect the reaction flux of ammonia at 20% fuel consumption, however, it makes the fuel H-atom abstraction reaction NH3 + H <=> NH2 + H2 proceed in the reversed way at the initial stage of ignition, therefore generate active H radical for further chain branching and promote the reactivity.

Study of the Effects of Changes in Gas Composition as Well as Ambient and Gas Temperature on Errors of Indications of Thermal Gas Meters

Thermal gas meters represent a promising technology for billing customers for gaseous fuels, however, it is essential to ensure that measurement accuracy is maintained in the long term and in a broad range of operating conditions. The effect of hydrogen addition to natural gas will change the physicochemical properties of the mixture of natural gas and hydrogen. Such a mixture will be supplied through the gas system, to consumers, including households, where the amounts of received gas will be metered. The physicochemical properties of hydrogen, including the specific density or viscosity, differ significantly from those of the natural gas components, such as methane, ethane, propane, nitrogen, etc. Therefore, it is of utmost importance to establish the impact of the changes in the gas composition caused by the addition of hydrogen to natural gas on the metrological properties of household gas meters, including thermal gas meters. Furthermore, since household gas meters can be installed outdoors and, taking into account the fact that household gas meters are good heat exchangers, the influence of ambient and gas temperature on the metrological properties of those meters should be investigated. This article reviews a test bench and a testing method concerning errors of thermal gas meter indicators using air and natural gas, including the type containing hydrogen. The indication errors for thermal gas meters using air, natural gas and natural gas with an addition of 2%, 4%, 5%, 10% and 15% hydrogen were determined and then subjected to metrological analysis. Moreover, the test method and test bench are discussed and the results of tests on the impact of ambient and gas temperatures (‒25 °C and 55 °C, respectively) on the errors of indications of thermal gas meters are presented. Conclusions for distribution system operators in terms of gas meter selection were drawn based on the test results.

Effects of hydrogen addition on combustion, thermodynamics and emission performance of high compression ratio liquid methane gas engine

It is a potential approach to improve the fuel efficiency that the liquid methane gas (LMG) purified from liquefied natural gas (LNG) is fueled with the high compression ratio (CR) engine, while the actual effect is restricted by the lowcombustion velocity of methane. To solve this problem and further improve the LMG engine performance, the approach of hydrogen addition to LMG engine was investigated by combining experiment with numerical simulation. Based on experimental data, the computational fluid dynamics (CFD) model coupled with reduced chemical kinetic mechanism was built and calibrated, which was then employed to study the effects of different hydrogen energy fraction (HEF) on combustion, thermodynamic and emission of LMG engine. The results show that, the peak of heat release rate (HRR) increases sharply with the HEF rising and leads the maximum in-cylinder pressure to increase. The indicated thermal efficiency of LMG engine first increases and then decreases, and the maximum falls in the HEF range between 8% and 12%. Although the combustion velocity of mixture gas is obviously increased by hydrogen addition, the detonation trend still becomes larger and it increases by 10 times as HEF changes from 12% to 20%. As the HEF increases from 0 to 20%, NOx emission increases continuously, while CO and CH4 emissions decrease due to the higher combustion temperature. All these provided direction for improving LMG engine performance, and offered theoretical basis for selecting technology routes to meet emission regulations.

Effects of hydrogen direct injection on combustion and emission characteristics of a hydrogen/Acetone-Butanol-Ethanol dual-fuel spark ignition engine under lean-burn conditions

Acetone-Butanol-Ethanol (ABE) is an essential product in the production process of butanol, which is considered as an effective way to replace butanol used in engines because of the lower production cost of ABE. Hydrogen is an ideal fuel for engines because of its low ignition energy and high flame propagation speed. In this study, the effects of hydrogen addition on the combustion and emission characteristics of a spark ignition ABE engine under lean-burn conditions are investigated. Specifically, five hydrogen blending ratios (0, 5%, 10%, 15%, 20%) and three λ values (1, 1.1, 1.2) are studied. The results show that adding hydrogen can increase the maximum cylinder temperature and pressure, decrease the flame development and propagation duration of the hydrogen/ABE dual-fuel SI engine. In addition, hydrogen addition can reduce the COVIMEP, BSFC, CO, HC emissions, and improve the IMEP, but increase NOx emissions; however, a lower NOx emissions for the hydrogen/ABE engine working under learn-burn conditions (λ equals 1.2) can be achieved with a suitable proportion of hydrogen adding (proportion = 5%) than that of engine working under stoichiometric air-fuel ratio condition. Thus, hydrogen addition can facilitate the combustion of ABE in engines, especially under lean-burn conditions.

The effect of hydrogen addition to compressed natural gas on performance and emissions of a DI diesel engine by a numerical study

Diesel engines are the most commonly used internal-combustion engines. Due to incomplete combustion of fossil fuels, engine performance and emissions output are unsuitable. On the other hand Emissions of greenhouse gases using fossil fuels in internal-combustion engines are considered to be the main cause of climate change. Thus to find an alternative fuel to eliminate or reduce CO2 and exhaust emissions is an urgent concern worldwide. Superabundant and readily available, makes hydrogen an attractive alternative to fossil fuels. In this study, a 3-cylinder turbocharged diesel engine is converted into CNG direct-injection engine and then hydrogen as a fuel enrichment added to CNG. AVL Fire™ Software is used to simulate the engine at different engine speeds, injection pressure, and Air/Fuel ratios. The results confirm that adding hydrogen to CNG improves brake thermal efficiency and engine brake power, reduces brake specific fuel consumption as well as the diminution in HC and Soot but also increases the NOx.

Effect of hydrogen addition on the ionization of partially premixed methane flame

The flame ionization characteristic is a key point to realize the combustion diagnosis and control of hydrocarbon flame based on electric fields. In this paper the effects of hydrogen addition on the ionization of partially premixed methane flame were investigated experimentally and computationally. The flame current was measured by applying a small electric field across the partially premixed methane flame with different hydrogen addition and the effects of hydrogen addition on the ionization intensity and the flame ionization structure were analyzed. Furthermore, the intrinsic reaction mechanism of hydrogen addition affecting the ionization of partially premixed methane flame was studied based on a comprehensive reaction mechanism, which combines GRI 3.0 for neutral species and an 85-steps flame ionization reaction for 13 kinds of charged species. The results show that hydrogen addition can promote the ionization of partially premixed flame by affecting the chemical ionization process. However, when the hydrogen content reaches 50% of the total fuel amount, the promotion effect will be significantly weakened. Moreover, for partially premixed methane flame, the effect of hydrogen addition on the flame ionization was affected by the amount of primary premixed air. The larger the amount of primary premixed air, the more significant the promotion of hydrogen addition. What’s more, the hydrogen addition mainly affects the concentration of e− in the flame through the reactions H + CH3 (+M) ⇔ CH4 (+M) and H + O2 ⇔ O + OH while affects the concentration of H3O + through the reactions OH + CH3 ⇔ CH2 (S) + H2O and H3O+ + e− ⇔ OH + 2H.

Swirl flame boundary layer flashback at elevated pressure: Modes of propagation and effect of hydrogen addition

Operating lean-premixed gas turbine burners with fuels containing large amounts of hydrogen severely increases the risk of flame flashback. Enabling fuel-flexible burners, i.e. mitigating that risk for a wide range of hydrogen admixed to natural gas, for instance, is particularly challenging. An improved understanding of the responsible mechanisms and their impact on flashback limits is required to aid the development of such fuel-flexible and yet flashback-resistant burners. Only few detailed and systematic investigations on flame flashback have been conducted at elevated pressure and preheat temperature. In the current experimental study, boundary layer flashback of methane-hydrogen air flames has been investigated in an optically accessible swirl burner installed in a high-pressure test rig. High-speed imaging and laser diagnostics have been applied to characterize the flame propagation pathway and flame shapes. The current findings show that the flame propagation pathway, which determines the relevant flow-flame interaction for flashback, differs compared to previous swirl flame studies. The characteristics of flashback in the current configuration are found to be comparable to flashback in non-swirling boundary layers. Flashback limits have been measured at 2.5 bar and 200∘C preheat temperature to quantify the increase in flashback propensity as the amount of hydrogen is increased from 50% to 100% by volume. Counterflow premixed flame simulations have been performed to investigate the increase in flashback propensity with hydrogen addition. The results suggest that the investigated flames are close to being critically stretched when flashback occurs in the turbulent boundary layer, which allows deriving a Karlovitz number based criterion for an improved prediction of flashback limits.

Minimizing carbon deposition in plasma-induced methane coupling with structured hydrogenation catalysts

The effect of temperature and hydrogen addition on undesired carbonaceous deposit formation during methane coupling was studied in DBD-plasma catalytic-wall reactors with Pd/Al2O3, using electrical power to drive the reaction. Experiments with thin catalyst layers allowed comparison of the performance of empty reactors and catalytic wall reactors without significantly influencing the plasma properties. The product distribution varies strongly in the temperature window between 25 and 200 °C. Minimal formation of deposits is found at an optimal temperature around 75 °C in the catalytic-wall reactors. The selectivity to deposits was c.a. 10% with only 9 mg of catalyst loading instead of 45% in the blank reactor, while decreasing methane conversion only mildly. Co-feeding H2 to an empty reactor causes a similar decrease in selectivity to deposits, but in this case methane conversion also decreased significantly. Suppression of deposits formation in the catalytic-wall reactor at 75 °C is due to catalytic hydrogenation of mainly acetylene to ethylene. In the empty reactor, H2 co-feed decreases conversion but does not change the product distribution. The catalytic-wall reactors can be regenerated with H2-plasma at room temperature, which produces more added-value hydrocarbons.