Effect Of Hydrogen Enrichment Research Articles

Experimental Study on the Effect of Hydrogen Enrichment of Methane on the Stability and Emission of Nonpremixed Swirl Stabilized Combustor

An ultra lean mixture (ϕ ≤ 0.5) of methane–hydrogen–air was experimentally investigated to explore the effect of fuel flexibility on the flame stability and emission of a nonpremixed swirl stabilized combustor. In order to isolate the effect of hydrogen addition to methane, experiments were carried out at fixed fuel energy input to the combustor while increasing the hydrogen content from 0% up to 50% in the methane–hydrogen mixture on volume basis. The combustor fuel energy was then increased up to the range of typical gas turbine combustors. Equivalence ratio sweep was carried out to determine the lean stability limit of the combustor. Results show that the hydrogen content in the fuel mixture and fuel energy input have a coupled effect on the combustor lean blow off velocity (LBV), temperature and emissions. The LBV increases by ∼103% with the addition of 30% H2. On the other hand, the LBV increases by ∼20% as the fuel energy increases from 1.83 MW/m3 to 2.75 MW/m3. Burning under ultra lean condition serves two purposes. (1) The excess air supplied reduces the overall combustor temperature with its ensuing effect on low NOx formation. (2) It increases the overall combustor volume flow rate which reduces the residence time for NOx formation. The axial temperature profile presented along with the emission data can serve as basis for the validation of numerical models. This would give more insight onto the effect of hydrogen on the turbulence level and how it would improve the localized extinction of methane in a cost-effective way.

Investigation of Hydrogen Enriched Natural Gas Flames in a SGT-700/800 Burner Using OH PLIF and Chemiluminescence Imaging

The effect of hydrogen enrichment to natural gas flames was experimentally investigated at atmospheric pressure conditions using flame chemiluminescence imaging, planar laser-induced fluorescence of hydroxyl radicals (OH PLIF), and dynamic pressure monitoring. The experiments were performed using a third generation dry low emission (DLE) burner used in both SGT-700 and SGT-800 industrial gas turbines from Siemens. The burner was mounted in an atmospheric combustion test rig at Siemens with optical access in the flame region. Four different hydrogen enriched natural gas flames were investigated; 0 vol. %, 30 vol. %, 60 vol. %, and 80 vol. % of hydrogen. The results from flame chemiluminescence imaging and OH PLIF show that the size and shape of the flame was clearly affected by hydrogen addition. The flame becomes shorter and narrower when the amount of hydrogen is increased. For the 60 vol. % and 80 vol. % hydrogen flames the flame has moved upstream and the central recirculation zone that anchors the flame has moved upstream the burner exit. Furthermore, the position of the flame front fluctuated more for the full premixed flame with only natural gas as fuel than for the hydrogen enriched flames. Measurements of pressure drop over the burner show an increase with increased hydrogen in the natural gas despite same air flow thus confirming the observation that the flame front moves upstream toward the burner exit and thereby increasing the blockage of the exit. Dynamic pressure measurements in the combustion chamber wall confirms that small amounts of hydrogen in natural gas changes the amplitude of the dynamic pressure fluctuations and initially dampens the axial mode but at higher levels of hydrogen an enhancement of a transversal mode in the combustion chamber at higher frequencies could occur.

Experimental results of hydrogen enrichment of ethanol in an ultra-lean internal combustion engine

An investigation was made to determine the effects of hydrogen enrichment of ethanol at ultra-lean operating regimes utilizing an experimental method. A 0.745 L 2-cylinder SI engine was modified to operate on both hydrogen and ethanol fuels. The study looked at part throttle, fixed RPM operation of 0%, 15%, and 30% hydrogen fuel mixtures operating in ultra-lean operating regimes. Data was collected to calculate NO and HC emissions, power, exhaust gas temperature, thermal efficiency, volumetric efficiency, brake-specific fuel consumption, and Wiebe burn fraction curves.It was shown that hydrogen enrichment of ethanol demonstrated an ability to reduce NOx and stabilize and accelerate the combustion process. The experiments showed that operating near the LOL at both 15% and 30% hydrogen by volume reduced engine out NOx emissions by more than 95% as compared to stoichiometric gasoline operation. This reduction is comparable to the efficiency of modern three-way catalyst and could offer an alternative to current NOx reduction technologies. Power, thermal efficiency, and volumetric efficiency were not affected by the hydrogen mixture at a given equivalence ratio. However, hydrogen addition allowed an increase in the lean operating limit which helped further reduce NOx emissions, but also at reduced power and thermal efficiency.

An Experimental Study on Performance Characteristics of a Hydrogen Fuelled Spark Ignition Engine

The purpose of this study is to obtain low-emission and high-efficiency in LPG engine with hydrogen enrichment. The objective of this paper is to clarify the effects of hydrogen enrichment in LPG fuelled engine on exhaust emission, thermal efficiency and performance. The compression ratio of 8 was selected to avoid abnormal combustion. To maintain equal heating value of fuel blend, the amount of LPG was decreased as hydrogen was gradually added. The relative air-fuel ratio was increased from 0.76 to 1.5, and the ignition timing was controlled to be at minimum spark advance for best torque (MBT).

Experimental investigation on the effects of hydrogen addition on thermal characteristics of methane/air premixed flames

This paper presented an experimental study on the measurements of premixed laminar methane/air flames with and without hydrogen addition. The premixed flames were stabilized on a McKenna flat fame burner at atmospheric pressure. The traveling thermocouple approach was used to measure the axial flame temperature profiles over ranges of equivalence ratios and hydrogen enriching ratios. The measured temperatures, corrected by considering radiation loss, were analyzed to estimate the rate of flame heat release, by solving the continuity equations of mass, energy, and species which were applied to a flat flame. Some of important flame properties, such as the peak temperature, the average temperature, the flame thickness, the thickness of reaction zone and combustion efficiency, were presented to characterize the effect of hydrogen enrichment on laminar flame propagation. It is shown that the presence of hydrogen in laminar flame can promote flame reaction to some extent. With an increase of hydrogen addition fraction in fuel, the peak rate of heat release and combustion efficiency show increases, while the average temperature gives decrease. The analysis of the heat release profiles suggested that hydrogen addition has significant effect on the early part of flame heat release profile. The flames enriched by hydrogen show linear approximations in the plots of the logarithmic heat release rate against the reciprocal of flame temperature. A modeling for one dimensional premixed laminar burner-stabilized flame had been implemented with GRI-Mech 3.0 detailed kinetic reaction mechanism, based on the measured temperature profiles of these premixed flames. And then an analysis on the heat release was performed for each reaction. It suggested that the reaction OH+H2⇔H+H2O gradually increases its contribution to the early heat release with the increase of hydrogen enrichment, which is due to the fact of hydrogen addition resulting in an increased concentration of radical H in flame. The promoted H formation accelerates the flame burning velocity, and then thins the thicknesses of flame and reaction zone to a great extent.

LPG기관의 부분부하 조건에서 수소 혼합에 따른 성능 및 배출가스 특성에 관한 실험적 연구

The purpose of this study is to obtain low-emission and high-efficiency by hydrogen enriched LPG fuel in LPG engine and is to clarify the effects of hydrogen enrichment in LPG fuelled engine on exhaust emission and performance. An experimental study was carried out to obtain fundamental data for performance and emission characteristics of hydrogen enrichment in LPG engine. The research was held by changing the hydrogen ratio to 0, 5, 10, 20% in 1500rpm, bmep 2 and 4bar. The result turned out that the combustion duration was shortened due to fast flame propagation of hydrogen. And the amount of Carbon dioxide and Hydrocarbon decreased. However, the amount of NOX increased, which is thought to be the result of high adiabatic flame temperature of hydrogen. It has been confirmed that this phenomenon has changed by the Hydrogen mixing ratio.

Effect of biogas-enriched with hydrogen on the operation and performance of a diesel-biogas dual engine

The effect of hydrogen enrichment was tested for a diesel-biogas dual fuel engine. The operation and performance characteristics, such as thermal efficiency, pollutant emissions and combustion parameters were determined. Experiments have been carried with a stationary compression ignition (CI) engine coupled with a generator in dual mode using a typical biogas composition of 60% vol. CH4 and 40% vol. CO2. For every load engine evaluated, the hydrogen concentration was varied from 5 to 20% H2 v/v. The results showed increases in peak pressure chamber up to 10.7 bar, and diesel substitution levels up to 80% under conditions of steady combustion without knocking. Also, thermal efficiency increases up to 16% and carbon monoxide emissions decreases up to 13% at full load, and 20% of hydrogen in engines operating in diesel-biogas dual mode.

Effects of hydrogen and steam addition on laminar burning velocity of methane–air premixed flame: Experimental and numerical analysis

Effects of hydrogen enrichment and steam addition on laminar burning velocity of methane–air premixed flame were studied both experimentally and numerically. Measurements were carried out using the slot burner method at 1 bar for fresh gases temperatures of 27 °C and 57 °C and for variable equivalence ratios going from 0.8 to 1.2. The hydrogen content in the fuel was varied from 0% to 30% in volume and the steam content in the air was varied from 0 to 112 g/kg (0–100% of relative humidity). Numerical calculations were performed using the COSILAB code with the GRI-Mech 3.0 mechanism for one-dimensional premixed flames. The calculations were implemented first at room temperature and pressure and then extended to higher temperatures (up to 917 K) and pressures (up to 50 bar). Measurements of laminar burning velocities of methane–hydrogen–air and methane–air–steam agree with the GRI-Mech calculations and previous measurements from literature obtained by different methods. Results show that enrichment by hydrogen increases of the laminar burning velocity and the adiabatic flame temperature. The addition of steam to a methane–air mixture noticeably decreases the burning velocity and the adiabatic flame temperature. Modeling shows that isentropic compression of fresh gases leads to the increase of laminar burning velocity.

An experimental study on the effect of hydrogen enrichment on diesel fueled HCCI combustion

This paper experimentally investigates the influence of hydrogen enrichment on the combustion and emission characteristics of a diesel HCCI engine using a modified Cooperative Fuel Research (CFR) engine. Three fuels, n-heptane and two middle distillates with cetane numbers of 46.6 and 36.6, are studied. The results show that hydrogen enrichment retards the combustion phasing and reduces the combustion duration of a diesel HCCI engine. Besides, hydrogen enrichment increases the power output and fuel conversion efficiency, and improves the combustion stability. However, hydrogen enrichment may narrow the operational compression ratio range and increase the knocking tendency. Both the overall indicated specific CO emissions (isCO) and CO emissions per unit burned diesel fuel mass are reduced by hydrogen enrichment. Although hydrogen enrichment decreases the overall indicated specific unburned hydrocarbon emissions (isHC), it does not significantly affect the HC emissions per unit burned diesel fuel mass.

Flammability limits of hydrogen-enriched natural gas

This paper reports both the lower and upper flammability limits of hydrogen-enriched natural gas with hydrogen fractions of 20%, 40%, 60% and 80% respectively as well as these of natural gas and hydrogen, measured by using a constant volume combustion chamber together with a high-speed schlieren photographic system. Based on investigating pressure rise history inside the combustion chamber as well as flame photos, the effect of hydrogen enrichment on the flammability characteristics is discussed. Our experimental results show that the flammability limits of methane–hydrogen mixtures can be used for hydrogen-enriched natural gas as long as their hydrogen fractions are the same. In this paper, the flammability data of methane–hydrogen mixtures available in the literature are reviewed. Correlations for both the lower and upper flammability limits of methane–hydrogen mixtures are summarized.

The effects of hydrogen substitution on turbulent premixed methane–air kernels using direct numerical simulation

Abstract Direct numerical simulations (DNS) are used to assess the effects of hydrogen substitution on lean premixed methane–air kernels during the early stages of growth in freely decaying turbulence. Two-dimensional simulations with a detailed 68-step reaction mechanism are carried out at equivalence ratios of ϕ = 0.53 and ϕ = 0.625, both with and without the substitution of a 30% fuel mole fraction of hydrogen. A comparative analysis is made into the changes in turbulent flame speeds, global stretch rates, and flame wrinkling at different turbulence intensities. The underlying causes of these changes are investigated through the distributions of the surface-conditioned displacement speed, strain rate and curvature. Direct comparison is made with the planar flame results of Hawkes and Chen [1] to assess the qualitative effects of kernel geometry in combination with a hydrogen-enriched fuel. It was found that the reduced effective fuel Lewis number and preferential diffusion of hydrogen, combined with the higher stretch rates and mean positive curvature of the kernel make the effects of hydrogen enrichment much more pronounced in kernels compared to planar flames.

Effects of hydrogen enrichment on adiabatic burning velocity and NO formation in methane + air flames

Experimental measurements of the adiabatic burning velocity and NO formation in methane + hydrogen + air flames are presented. The hydrogen content in the fuel was varied from 0% to 35%. Non-stretched flames were stabilized on a perforated plate burner at 1 atm. The Heat Flux method was used to determine burning velocities under conditions when the net heat loss of the flame is zero. An overall accuracy of the burning velocities was estimated to be better than ±0.8 cm/s in the whole range of enrichment by hydrogen. A procedure for estimation of errors in equivalence ratio was extended to binary fuel mixtures. The relative accuracy of the equivalence ratio was found to be below 1.47%. Adiabatic burning velocities of methane + hydrogen + air mixtures were found in satisfactory agreement with the literature results and with the Konnov model predictions. A new correlation for the adiabatic laminar burning velocity of methane + hydrogen + air mixtures burning at standard conditions was derived. The NO concentrations as a function of equivalence ratio were measured using probe sampling at a fixed distance from the burner. In lean flames enrichment by hydrogen has little effect on [NO], while in rich flames the concentration of nitric oxide decreases significantly. The numerical predictions are in good agreement with the experiment.

Evaluation of the combustion behaviour of perhydrous coals by thermal analysis

Perhydrous coals are characterized by a high hydrogen content and exhibit a modified composition and physico-chemical properties in comparison with normal coals. These modifications affect the behaviour of perhydrous coals during pyrolysis and, therefore, may have an influence on the subsequent combustion process. In this work the combustibility behaviour of a series of perhydrous coals was evaluated in order to study the effect of hydrogen enrichment during the thermal treatment of the coals in an oxidant atmosphere. To this end temperature programmed combustion tests for the coals, and air isothermal (500°C) reactivity tests for their chars, were carried out in a thermogravimetric analyser. A clear relationship between the combustion behaviour of the perhydrous coals, and the aromatic to aliphatic hydrogen ratio was found.

The effect of hydrogen enrichment on exhaust emissions and thermal efficiency in a LPG fuelled engine

The concept of hydrogen enriched LPG fuelled engine can be essentially characterized as low emissions and reduction of backfire for hydrogen engine. The purpose of study is obtaining low-emission and high-efficiency in LPG engine with hydrogen enrichment. In order to determine the ideal compression ratio, a variable compression ratio single cylinder engine was developed. The objective of this paper is to clarify the effects of hydrogen enriched LPG fuelled engine on exhaust emission, thermal efficiency and performance. The compression ratio of 8 was selected to minimize abnormal combustion. To maintain equal heating value, the amount of LPG was decreased, and hydrogen was gradually added. In a similar manner, the relative air-fuel ratio was increased from 0.8 to 1.3 in increment of 0.1, and the ignition timing was controlled to be at MBT each case.