Hydrogen Blending Ratio Research Articles

Study on leakage and explosion consequence for hydrogen blended natural gas in urban distribution networks

It appears to be the most economical means of transporting large quantities of hydrogen over great distances by the existing natural gas pipeline network. However, the leakage and diffusion behavior of urban hydrogen blended natural gas and the evolution law of explosion characteristics are still unclear. In this work, a Computational Fluid Dynamics three-dimensional simulation model of semi-confined space in urban streets is developed to study the diffusion process and explosion characteristics of hydrogen-blended natural gas. The influence mechanism of hydrogen blending ratio and ambient wind speed on the consequences of explosion accident is analyzed. And the dangerous area with different environmental wind effects is determined through comparative analysis based on the most dangerous scenarios. Results indicate that the traffic flow changes the diffusion path of the jet, the flammable gas cloud forms a complex profile in many obstacles, high congestion level lead to more serious explosion accidents. Wind effect keeps the flammable gas cloud near the vehicle flow, the narrow gaps between the vehicles aggravate the expansion of the flammable gas cloud. When the wind direction is consistent with the leakage direction, hydrogen blended natural gas is gathered in the recirculation zone due to the vortex effect, which results in more serious accident consequences. With the increase in hydrogen blending ratio, the higher content of H and OH in the gas mixture significantly increases the premixed burning rate, the maximum overpressure rises rapidly when the hydrogen blend level increases beyond 40%. The results can provide a basis for construction safety design, risk assessment of leakage and explosion hazards, and emergency response in hydrogen blended natural gas distribution systems.

Influences of Hydrogen-Natural Gas Mixtures on The Performance of an Internal Reforming Solid Oxide Fuel Cell Unit: A Simulation Study

Blending hydrogen into natural gas grid can effectively reduce carbon emissions and promote the development of the hydrogen economy. Utilizing hydrogen-natural gas mixtures through internal reforming solid oxide fuel cells (SOFCs) can convert the chemical energy of the fuels direct into electricity, which is a promising technology for combined heat and power systems. In this study, a three-dimensional model for an internal reforming solid oxide fuel cell unit is developed coupling chemical and electrochemical reactions, mass, momentum and heat transfer processes. The model is validated by both the patterned anode experiments and the button cell experiments with porous electrodes. The distributions of temperature, gas compositions, and current density between pure methane and 30% hydrogen addition are simulated and compared. The influences of the hydrogen addition on the performance of the SOFC unit are further studied by changing the hydrogen blending ratio. The simulation results show that the addition of hydrogen affects the coupling of the endothermic reforming reactions and exothermic electrochemical reactions, which leads to improved temperature uniformity and higher current density of the SOFC unit compared with pure methane feeding.

An Experimental Study of the Effect of Different Blending Ratios of Dual and Triple Fuel Mixtures (Gasoline-Hydrogen-Ethanol) on Laminar Flame Speed


 
 
 
 Abstract
 In a centrally ignited constant volume chamber, an experimental research on the laminar flame speed of premixed gasoline/ethanol/hydrogen/air mixtures is undertaken at varied initial pressures (0.1-0.3 MPa), constant initial temperature (593 K), and variable equivalency ratios (0.75-1.5). The mixing method is based on the energy replacement principle, and various component blending ratios are tested. This has necessitated the construction of a specific laboratory experimental equipment. The flame speeds are measured using the Shelerian photography technique using a high-speed camera. The results reveal that adding hydrogen to dual fuel mixtures has a considerable impact on stretched laminar flame speed. The stretched laminar flame speeds for 20 percent H2-80 percent G, 40 percent H2-60 percent G, and 60 percent H2-40 percent G are 3.71 m/s, 7.329 m/s, and 11.0267 m/s, respectively, at 0.1 MPa initial pressure and stoichiometric mixture. For 20 percent H2-80 percent G, 40 percent H2-60 percent G, and 60 percent H2-40 percent G mixtures, the un-stretched flame speed at atmospheric pressure and stoichiometric is computed and found to be 1.23 m/s, 3.67 m/s, and 7.093 m/s, respectively. When the initial pressure is increased, both stretched and un-stretched flame rates drop. "
 The results of the triple fuel mixes demonstrate that the influence of ethanol addition on the stretched laminar flame speed is significant at constant hydrogen blending ratios, with 2.24 m/s at 20% H2-16% E-64 percent G and 2.68 m/s at 20% H2-32 % E-48 % G at 0.1 MPa for stoichiometric mixture. For dual fuel combinations, the effect of starting pressure on stretched and un-stretched flame speeds is the same. Where the flame speed has a maximum value for stoichiometric combustion, the equivalence ratio has a greater effect on flame speed. "
 
 
 

Numerical investigation on the leakage and diffusion characteristics of hydrogen-blended natural gas in a domestic kitchen

Hydrogen blending has significant influences on the characteristics and evolution of safety accidents of natural gas. In this study, the numerical investigation is performed to reveal the leakage and diffusion characteristics of hydrogen-blended natural gas in a real domestic kitchen by using the ANSYS Fluent software. The physical and mathematical model of gas leak from cooking appliances is established, and the explosion risk area, alarm response time and concentration distribution of leaked gas are studied. Influences of hydrogen blending ratio (HBR), leak rate, ventilation condition and dimension size on the characteristics and evolution of leakage and diffusion are analyzed. Results show that with the increase of HBR at constant leak rates, both the alarm time and the time to reach lower explosion limit are advanced. When the volume leak rate is constant, the alarm response time for HBR of 2.5%, 5%, 7.5%, 10%, 12.5%, 15%, 17.5% and 20% is 0.50%, 1.51%, 3.02%, 3.78%, 6.53%, 10.34%, 12.34% and 14.11% earlier than that of natural gas. The natural ventilation can effectively reduce leaked gas concentration in kitchen. At the wind speed of 1 m/s, the leaked gas concentration falls below alarm concentration within 28s, but the free diffusion takes as long as 720s.

Study on combustion characteristic of premixed H2/C3H8/air and working performance in the micro combustor with block

Combustion characteristics and thermal performance of premixed H2/C3H8/air in a micro planar combustor with block insert are experimentally and numerically tested. Effects of hydrogen blended fraction, equivalence ratio, flow rate and block width on the flame stability and heat transfer are discussed and analyzed. The results indicate that hydrogen addition is beneficial to the combustion stability in the micro combustor, and the lowest hydrogen blending mole fraction of the premixed H2/C3H8/air steady flame is obtained by experimental study. The combustion stability range is the widest in the combustor with a 0.7 mm block inserted at a high fuel rate. Moreover, the wall temperature is deeply influenced by hydrogen blending ratio and block size, that is, the combustor with appropriate block width and H2/C3H8 blended burning gains a higher radiation temperature. Then, effects of the hydrogen fraction on the reaction pathways are analyzed, and the fluxes of OH and H production by the key reactions such as H + O2 = OH + O and H2 = OH + H are calculated, where flame location and reaction area are significantly affected. It also finds that the combustor C0.7 fueled with 90% hydrogen gains the highest mean wall temperature of 1150.3 K and radiation power of 27.9 W under the same chemical energy input Ec = 90.6 W.

Numerical Simulation of an Internal Reforming Solid Oxide Fuel Cell Unit Fueled with Hydrogen-Natural Gas Mixtures

Blending hydrogen into natural gas grid can effectively reduce carbon emissions and promote the development of the hydrogen economy. Utilizing hydrogen-natural gas mixtures through internal reforming solid oxide fuel cells (SOFCs) can convert the chemical energy of the fuels direct into electricity, which is a promising technology for combined heat and power systems. In this study, a three-dimensional model for an internal reforming solid oxide fuel cell unit is developed coupling chemical and electrochemical reactions, mass, momentum, and heat transfer processes. The influences of the hydrogen addition on the distributions of temperature, gas compositions, and current density are studied by changing the hydrogen blending ratios in inlet gas mixtures. The simulation results show that the addition of hydrogen affects the coupling of the endothermic reforming reactions and exothermic electrochemical reactions, which leads to improved temperature uniformity and higher current density of the SOFC unit compared with pure methane feeding.

Influences of Hydrogen Blending on the Joule-Thomson Coefficient of Natural Gas.

Blending hydrogen into the natural gas pipeline is considered as a feasible way for large-scale and long-distance delivery of hydrogen. However, the blended hydrogen can exert major impacts on the Joule–Thomson (J–T) coefficient of natural gas, which is a significant parameter for liquefaction of natural gas and formation of natural gas hydrate in engineering. In this study, the J–T coefficient of natural gas at different hydrogen blending ratios is numerically investigated. First, the theoretical formulas for calculating the J–T coefficient of the natural gas–hydrogen mixture using the Soave–Redlich–Kwong (SRK) equation of state (EOS), Peng–Robinson EOS (PR-EOS), and Benedict–Webb–Rubin–Starling EOS (BWRS-EOS) are, respectively, derived, and the calculation accuracy is verified by experimental data. Then, the J–T coefficients of natural gas at six different hydrogen blending ratios and thermodynamic conditions are calculated and analyzed using the derived theoretical formulas and a widely used empirical formula. Results indicate that the J–T coefficient of the natural gas–hydrogen mixture decreases approximately linearly with the increase of the hydrogen blending ratio. When the hydrogen blending ratio reaches 30% (mole fraction), the J–T coefficient of the natural gas–hydrogen mixture decreases by 40–50% compared with that of natural gas. This work also provides a J–T coefficient database of a methane–hydrogen mixture with a hydrogen blending ratio of 5–30% at a pressure of 0.5–20 MPa and temperatures of 275, 300, and 350 K as a reference and a benchmark for interested readers.

Characterising premixed ammonia and hydrogen combustion for a novel Linear Joule Engine Generator

A novel ammonia/hydrogen dual-fuelled Linear Joule Engine Generator (LJEG) is developed for medium to large scale power generations and electrification of ship propulsion systems. The characteristics of premixed ammonia/hydrogen combustion of the LJEG are investigated through chemical kinetic modelling. Three representative mechanisms are compared based on their accuracy of reproducing experimental results. With robust combustion and low NOx emission as the primary targets, laminar burning velocity, ignition delay and flame species concentration are investigated over a wide range of equivalence ratio (0.8−1.6), hydrogen blending ratio (0.0−0.6), oxygen content (0.21−1.00), inlet temperature (300K−700K) and pressure (1bar−20bar). Rate of production (ROP) analysis is carried out to gain in-depth understanding of critical NO production and consumption pathways. The results indicate that an equivalence ratio around 1.1 is beneficial for both combustion robustness and NOx emission reduction. Both adding hydrogen in the fuel (40%Vol) and enriching oxygen in the oxidizer (60%Vol) promote burning velocity to the similar level of methane (37cm/s). Explicit reduction of NO emission is observed when pressure increases, which can be attributed to the combination of NHi radicals. The findings show the potential of the ammonia and hydrogen fuelled LJEG for ultra-low emission power generation.

Effects of hydrogen blending on hydraulic and thermal characteristics of natural gas pipeline and pipe network

Blending a fraction of hydrogen into the natural gas pipeline or urban pipe network is an efficient approach for hydrogen delivery. In this paper, the mathematical model of Hydrogen-Blended Natural Gas (HBNG) transportation is established, and the influences of hydrogen blending on hydraulic and thermal characteristics of natural gas pipeline and pipe network are numerically investigated. The impact of hydrogen blending ratio on the performance of centrifugal compressor and the operating point for joint operation of pipeline and compressor is discussed. Results illustrate that compared with natural gas without hydrogen, the hydrogen blending can reduce the pipeline friction resistance and increase the volume flow rate. However, due to the lower volumetric calorific value of HBNG, the energy flow rate actually decreases under the same transportation condition. Meanwhile, the temperature drop along the pipeline slows down due to the blended hydrogen. The performance degradation of centrifugal compressor occurs with the increasing hydrogen blending ratio, and the operating point for joint operation of pipeline and centrifugal compressor moves to the direction of higher volume flow rate and lower pressure. This study is expected to shed a light on the hydrogen delivery by natural gas pipelines and pipe networks.

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.

Experimental Investigation of LPG/H2/Air Premixed Flame Stability Zone

Flame stability, environmental changes and fossil fuel shortage represent major challenges to any successful combustion device utilization. In this study, the stability zone of laminar premixed ILPG/ -air flames was investigated experimentally. Non-swirling burners with different diameters (10, 12.5, and 17 mm) were employed to characterize the flashback and blow-off limits. Different hydrogen blends (0%-50%) at equivalence ratios (ER) (0.6-1.4) were used. The results show that maximum flashback limits occurred at ER slightly richer than stoichiometric, with the mixture flow rate at a flashback of (3.75, 7.25 and 14) LPM for the 50% hydrogen blending ratio and a burner diameter of (10, 12.5 and 17 mm), respectively. When hydrogen blending was 50% at stoichiometric condition, the critical velocity gradient at flashback increased from (469.9-650.8 1/s) with 10 mm diameter, and the critical velocity gradient at blow-off increased from (1538-2936 1/s). It was observed that the flashback limits decreased with increasing burner diameter. Its limit increased with increasing hydrogen addition to the ILPG. The blow-off limit increased with increasing fuel concentration. This paper further presents the stability zone for ILPG/air combustion for a non-swirling burner with a 10-mm diameter and different hydrogen blends. It was found that the stability zone was narrow on the lean combustion side and enhanced with increasing diameter and hydrogen addition.

EFFECT OF OPERATING CONDITIONS ON PERFORMANCE AND EMISSIONS OF A DIESEL ENGINE OPERATED WITH DIESEL-HYDROGEN BLEND

Hydrogen is a clean fuel for internal combustion engines since it produces only water vapor and nitrogen oxides when it burns. In this research, hydrogen is used as a blending fuel with diesel to reduce pollutants emission and to improve performance. It is inducted in the inlet manifold, of a single cylinder, four stroke, direct injection, water cold diesel engine, type (Kirloskar). Hydrogen blending is done on energy replacement basis. A special electronic unit is designed and fabricated to control hydrogen blending ratio. The maximum achieved ratio is 30% of input energy and beyond that engine operation becomes unsatisfactory when the air temperature is 20 oC and injection timing of -35o CA which represent the first part of this work. Inlet air heating system is built and added in the experimental work. The heating system allows to increase the air temperature up to 100 oC. A heating of air to 60 oC with injection timing of -30o CA and 55% of hydrogen blending is executed in the second part of this study. Tests are done with 17.5 compression ratio and 1500 rpm. The brake specific fuel consumption is reduced by 29% and 46%, the engine thermal efficiency is increased with 16% and 21% for the 1st and 2nd part respectively. The pollutant emissions of carbon oxides, UHC, and smoke opacity are dramatically decreased by 19.5%, 13%, and 45% respectively for the 1st part and 41%, 38% and 65.6% for the 2nd part while NOx emission is increased by 10% and 25% for the 1st and 2nd part respectively.

Analysis of exergy losses in laminar premixed flames of methane/hydrogen blends

Combustion is the primary source for exergy loss in power systems such as combustion engines. To elucidate the exergy loss behaviors in combustion and explore the principle for efficiency improvement, the second-law thermodynamic analysis was conducted to analyze the energy conversion characteristics in laminar premixed flames of methane/hydrogen binary fuels. The sources causing exergy losses in laminar premixed flames included five parts, namely heat conduction, mass diffusion, viscous dissipation, chemical reactions and incomplete combustion, respectively. The calculations were conducted at both atmospheric and elevated pressures, with the equivalence ratio varying from 0.6 to 1.5 and the hydrogen blending ratio increasing from 0% to 70%. The results indicated that the total exergy loss firstly increased and then decreased with increased equivalence ratio, and reached the minimum value at the equivalence ratio of 0.9. This was primarily due to the trade-off relation between the decreased exergy loss from entropy generation and the increased exergy loss from incomplete combustion, as equivalence ratio increased. As the hydrogen blending ratio increased from 0% to 70%, the total exergy loss decreased by 2%. Specifically, the exergy loss from heat conduction decreased, primarily due to the decreased flame thickness. Moreover, the reactions with H2, H and H2O as reactants were inhibited, leading to decreased the exergy loss from chemical reactions. As pressure increased from 1 atm to 5 atm, the total exergy loss decreased by 1%, because the exergy losses induced by heat conduction and chemical reactions decreased as the flame thickness was reduced. The exergy loss from incomplete combustion also decreased, because elevated pressure inhibited dissociations and decreased the mole fractions of incomplete combustion products.

Effect of different hydrogen blending ratios on combustion process of gasoline‐fueled rotary engine

The pre‐eminent gasoline rotary engine may be criticized for its unsatisfactory fuel consumption rate and unburnt emissions. The clean and renewable hydrogen fuel is a promising alternative for conventional fuels to improve the combustion process and power performance of the rotary engine. In this article, highly advanced numerical simulation was used to obtain some pivotal results such as the distribution of combustion intermediates, the turbulent kinetic energy, the kinetic rate of reactions, and the fuel concentration fields which are difficult to experimentally achieve. An experimentally validated three‐dimensional dynamic simulation model of a rotary engine coupled with chemical kinetics skeletal mechanism was set up to exactly investigate the effects of hydrogen blending on the combustion process, power performance, and pollutant emissions. The results showed that with the increase of hydrogen mixing ratio, the average pressure and the peak pressure increased in the combustion process. Meanwhile, more combustion active intermediates were generated in both the flame development period and flame propagation period. The mass fraction of OH and H radicals has an increase of 36% and 34%, respectively. The fuel combustion rate rose and the turbulent kinetic energy increased which are conducive to improving flame diffusion in the rear part of the chamber and thus facilitate the complete combustion of the fuel. Moreover, the hydrogen blending led to an effective reduction in the CO emission of gasoline‐fueled rotary engine; however, the NO emission slightly increased due to the rise of temperature in cylinder. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13146, 2019

Study on the combustion characteristics and ignition limits of the methane homogeneous charge compression ignition with hydrogen addition in micro-power devices

Based on the single process of free piston in micro HCCI free piston power device, the parameters such as the combustion characteristics of methane hydrogenation homogeneous charge compression ignition, the free piston movement process, the ignition time of the mixture gas, the changes of temperature and pressure in micro-combustion chamber, and the power capability of the device are compared and analyzed by combining the experiment method with the numerical simulation method. The experimental results are basically consistent with the numerical results. The research shows: when the initial equivalence ratio is 0.5, the blending of hydrogen can widen the ignition limit of mixed fuel, advance the ignition time of the mixture gas and reduce the starting energy needed for the device. At the same time, adding hydrogen to methane will reduce the maximum temperature and the maximum pressure of the micro-combustion chamber, make the burning flame more stable and alleviate the detonation phenomenon of the combustion of mixture gas. However, the addition of hydrogen to methane will result in the decrease of the final speed of the free piston, the increase of the time required for a single stroke, the decrease of the power capacity of the device, and the indicator thermal efficiency is also reduced. Only the proper hydrogen blending ratio can be used to expand the combustion boundary and improve the reliability of the combustion process while ensuring the capability of the micro power device.

Autoignition of DME/H2 mixtures in a rapid compression machine under low-to-medium temperature ranges

Ignition delays of dimethyl ether and hydrogen (DME/H2) mixtures (hydrogen blending ratio ranging from 0% to 60%) were measured in a rapid compression machine at compressed temperatures ranging from 655 to 810K and compressed pressures from 16.9 to 24.5bar with an equivalence ratio range of 0.8–1.6. Experimental measurements are compared with results from numerical simulations using the NUIG Mech_56.54 mechanism and, in general, a good agreement is obtained. The first-stage ignition delay of DME/H2 mixtures proves to be insensitive to compressed pressure and equivalence ratio, whereas the total ignition delay decreases distinctly with the increase of compressed pressure and equivalence ratio, especially in the negative temperature coefficient (NTC) region. Moreover, the simulation results show that the NTC region shifts to a higher temperature when compressed pressure is increased. Increasing the equivalence ratio enhances the overall system reactivity but does not significantly change the temperature range of the NTC region. Both first-stage and total ignition delay increase with the increase of hydrogen blending ratio. The total ignition delay as a function of hydrogen blending ratio increases nonlinearly, and the effect of hydrogen addition becomes more prominent in the NTC region and at 60% hydrogen blending ratio. Kinetic analysis indicates that hydrogen addition consumes OH radical and inhibits DME low-temperature oxidation. More fuel molecules undergo chain propagation reaction subsequently, leading to the decrease of heat release and radicals generated during the first-stage ignition and longer total ignition delay.

Effect of hydrogen addition on performance of low heat value gas engine

Experiment of low heat value gas blended with hydrogen in a modified single-cylinder CNG engine is studied. The components of low heat value gas contain natural gas and N2, the natural gas contents from 60% to 80% by volume, N2 content is from 20% to 40% by volume. The hydrogen blending ratio is from 10% to 30% by volume. Results show that with the increase of N2 proportion, the engine power, CO and NOx emissions are decreased, but HC emissions is increased. When hydrogen blending ratio is increased, CO emission is increased while HC emission is decreased. When properly increases hydrogen blending ratio, the maximum cylinder pressure and engine torque are increased. However, large hydrogen blending ratio will decrease engine power. NOx emission is related to N2 proportion of low heat value gas.

Study on the effect of hydrogen addition to dimethyl ether homogeneous charge compression ignition combustion engine

The auto-ignition characteristics of dimethyl ether (DME)/H2/Air blends (hydrogen blending ratio ranging from 0% to 70%) in homogeneous charge compression ignition (HCCI) combustion engine are investigated by calculation method using zero-dimension single-zone model. All the simulated mixtures demonstrated a two-stage heat release phenomenon at different crank angles. The results show that the hydrogen addition can retard the auto-ignition timing of DME in HCCI combustion engine. The ignition timing at low temperature is retarded slightly with the hydrogen addition, and the ignition timing at high temperature is delayed significantly due to the increased negative temperature coefficient duration. Chemical kinetic analysis reveals that the competition of OH radicals between hydrogen and DME could be the reason why the low temperature reactions of DME are mitigated. H2O2 molecules decompose at about 1000 K and initiate the high temperature reactions of the mixtures.

Effects of Hydrogen Addition on the Laminar Flame Speed and Markstein Length of Premixed Dimethyl Ether–Air Flames

Laminar flame speeds of premixed dimethyl ether/hydrogen/air flames were measured in a constant volume bomb at different temperatures, equivalence ratios, and hydrogen blending ratios. Results reveal that laminar flame speeds increase with an increased hydrogen blending ratio and initial temperature. The Wang model and Zhao model both perform well in predicting laminar flame speeds of the blends. Furthermore, three different models for an effective Lewis number are validated, and the volume-fraction-weighted model performs well in predicting the Markstein length. The effects of hydrogen addition on the flame speed and Markstein length of fuel blends are systematically studied. The chemical kinetic effect induced by hydrogen addition plays a dominant role in increasing the laminar flame speed in comparison to thermal and diffusive effects. In addition, there exists a critical equivalence ratio in the trend of the Markstein length. At the equivalence ratio less than the critical equivalence ratio, the Marks...

Laminar flame propagation and ignition properties of premixed iso-octane/air with hydrogen addition

Numerical simulations of one-dimensional planar and spherical flame propagation of iso-octane/hydrogen/air mixtures at different equivalence ratios and hydrogen blending levels are conducted considering detailed chemistry. Our focus is on the effects of hydrogen addition on laminar flame propagation and ignition of iso-octane/air mixtures. Specifically, the laminar flame speed, Markstein length, and minimum ignition energy of iso-octane/hydrogen binary fuel blends are investigated. The laminar flame speed is found to increase first slightly and then exponentially with the molar ratio of hydrogen in the iso-octane/hydrogen binary fuel blends. However, a nearly linear trend is observed when the mass ratio instead of molar ratio of hydrogen blending is considered. Similar trend holds for hydrogen addition to other hydrocarbon fuels such as methane and propane. The thermal and chemical effects involved in laminar flame speed enhancement by hydrogen addition are quantified and it is found that the chemical effect prevails over the thermal effect. Unlike the laminar flame speed, the Markstein length is found to change non-monotonically with hydrogen blending ratio. Blending hydrogen to iso-octane/air and blending iso-octane to hydrogen/air both promote diffusive-thermal instability. Moreover, the minimum ignition energy of iso-octane/air is shown to be reduced by a small amount of hydrogen addition, especially for the fuel lean case. When the hydrogen blending molar ratio is above 60%, the minimum ignition energy is found to be insensitive to hydrogen addition.