Ignition Of Hydrogen Research Articles

Effect of Hydrogen Blending on the Combustion Performance of a Gasoline Direct Injection Engine.

To explore the effect of hydrogen blending on the combustion of a gasoline direct injection engine, a three-dimensional model of the engine is built. The effects of some hydrogen volume fractions (HVFs) and ignition timings (ITs) on the engine performance parameters are studied. Furthermore, the microstructure and mechanism of combustion are analyzed. The simulation results reveal that when the gasoline engine is blended with hydrogen, the active hydroxyl radical concentration increases, and the combustion process is accelerated. When the IT is fixed, with the HVF rising, the peak heat release rate and cylinder pressure will increase. The ignition delay, combustion duration, and crank angle when cumulative heat release reaches 50% decrease. Additionally, the autoignition is shifted to an earlier time as the IT advances. Under the studied conditions with the increase in the HVF, the knock resistance is enhanced because hydrogen has a high knock resistance and octane number.

Investigating the explosion hazard of hydrogen produced by activated aluminum in a modified Hartmann tube

Metallic powders exposed to water are sources of hydrogen gas that may result in an explosion hazard in the process industries. In this paper, hydrogen production and flame propagation in a modified Hartmann tube were investigated using activated aluminum powder as fuel. A self-sustained reaction of activated aluminum with water was observed at cool water and room temperatures for all treatments. One gram of Al mixed with 5 wt% NaOH or CaO resulted in a rapid rate of hydrogen production and an almost 100% yield of hydrogen generation within 30 min. The flame structures and propagation velocity (FPV) of released hydrogen at different ignition delay times were determined using electric spark ignition. Flame structures of hydrogen were mainly dependent on hydrogen concentration and ignition delay time, likely due to different mechanisms of hydrogen generation and flame propagation. As expected, FPVs of hydrogen in the Hartmann tube increased with ignition delay time. However, the FPV of upward flame propagation was much larger than that of downward flame propagation due to the effect of spreading acceleration at the explosion vent. Once ignited, the FPV of upward flame propagation reached 31.3–162.5 m/s, a value far larger than the 7.5–30 m/s for downward flame propagation. Hydrogen explosion caused by the accumulation of wet metal dust can be far more dangerous than an ordinary hydrogen explosion.

Unsteady Regimes of Hydrogen Ignition and Flame Stabilization in a Channel

Unsteady Regimes of Hydrogen Ignition and Flame Stabilization in a Channel

Compression ignition of Hydrogen (H2) in a direct injection diesel engine Modified to operate as a Low Heat Rejection

Global pollution levels in many applications will now be at danger because of the growing need for fuel. CR hydrogen is an alternative to diesel fuel and a possible supply of unspent fuel in India. Using hydrogen as a sole fuel in a direct-injection diesel engine has been tested for its practicality. One-cylinder diesel engine with air cooling was adapted to operate as a low-heat-rejection engine. To protect the engine's combustion chamber, partially stabilized zirconia ceramic components were employed. A single-cylinder compression ratio (CR) engine with varied CR Hydrogen fuels will be studied to determine the optimal performance and emission characteristics. There was a comparison of diesel fuel performance measures such as specific fuel consumption (SFC), brake thermal efficiency (BTE), and emissions of HC, CO, Smoke, and NOx. A compression ratio of 17.5 for hydrogen fuel demonstrates higher performance and reduced emissions, which is quite similar to neat diesel fuel in terms of performance and emissions levels. Different compression ratios (15.5, 16.5, and 17.5) were tested in order to determine the optimal combination for running the engine on hydrogen mixes. Furthermore, the increase in compression ratio raises the BTE, reduces the SFC, and lowers emissions without any engine design changes

Combustion Analysis of Various Speed on Hydrogen (H2) in a Direct Injection Diesel Engine Modified to operate as a Low Heat Rejection (LHR)

The feasibility of using hydrogen as the sole fuel in a direct injection diesel engine was investigated. An air cooled single cylinder diesel engine was modified to operate as a lowheat-rejection engine for this study. Partially stabilized zirconia (PSZ) ceramic parts were used to shield the combustion space of the engine. Using a compression ratio of 17.9:1 and motoring the test engine at 2100 rpm, a maximum compression temperature of approximately 900 K was achieved. Under these operating conditions, all lubricants tested were found to burn. Lowering the speed to 1450 rpm and the compression ratio to 17.1, lubricant combustion and hot spots were successfully eliminated. The maximum compression temperature, when compression ignition of hydrogen was tried, was in the 800 K range. The corresponding ceramic surface temperature was estimated to reach 600- 700 K. Only sporadic compression ignition of hydrogen was achievable

Experimental and Modelling Study of Hydrogen Ignition in Co2 Bath Gas

Experimental and Modelling Study of Hydrogen Ignition in Co2 Bath Gas

Unsteady Regimes of Hydrogen Ignition and Flame Stabilization in a Channel

Unsteady Regimes of Hydrogen Ignition and Flame Stabilization in a Channel

Experimental study on the propagation characteristics of hydrogen/methane/air premixed flames in a narrow channel

This work is focused on the explosion characteristics of premixed gas containing different volume fractions of hydrogen in a narrow channel (1000 mm × 50 mm × 10 mm) under the circumstance of stoichiometric ratio. The ignition positions were set in the closed end and the middle of the pipeline respectively. The results showed that when the gas was ignited at the pipeline closed end, the propagating flame was tulip structure for different premixed gas. When the hydrogen volume fraction was less than 40%, the flame propagation speed increased significantly with the rise of hydrogen volume fraction, and the overpressure peak also appeared obviously in advance. However, when the volume fraction of hydrogen was more than 40%, the increase of flame propagation speed and the overpressure peak occurrence time varied slightly. Furthermore, when the ignition position was placed in the middle of the pipeline, the flame propagation speed propagating to the opening end was much faster than that propagating to the closing end, and there was no tulip shape when the flame propagates to the opening end. The flame propagating to the closed end appeared tulip shape under the influence of airflow, and high-frequency flame oscillation occurred during the propagation. This work shows that the hydrogen volume fraction and ignition position significantly affected the flame structure, flame front speed, and explosion overpressure.

Mechanism of spontaneous ignition of high-pressure hydrogen during its release through a tube with local contraction: A numerical study

The tendency of spontaneous ignition of high-pressure hydrogen during its sudden release into a tube is one of the main threats to the safe application of hydrogen energy. A series of investigations have shown that the tube structure is a key factor affecting the spontaneous ignition of high-pressure hydrogen. In this paper, a numerical study is conducted to reveal the mechanism of spontaneous ignition of high-pressure hydrogen inside the tube with local contraction. Large Eddy Simulation, Renormalization Group, Eddy Dissipation Concept, 37-step detailed hydrogen combustion mechanism and 10-step like opening process of burst disk are employed. Three cases with burst pressures of 3.10, 4.90, and 8.45 MPa are simulated to compare against the pervious experimental study. The spontaneous conditions and positions agree well with the experimental results. The numerical results indicate that shock wave reflection takes place at the upstream vertical wall of contraction part. The interacted-shock-affected region is generated at the tube center because of the subsequent shock wave interaction. The forward reflected shock wave couples with normal shock wave and increases the pressure of leading shock wave. The sudden contraction of tube blocks the propagation of hydrogen jet and decreases the speed from supersonic flow to subsonic flow. More flammable mixture is generated inside the contraction part, as a results, the length of the flame is increased. Two mechanisms are proposed finally.

Combustion characteristics of hydrogen in a noble gas compression ignition engine

Hydrogen eliminates carbon emissions from compression ignition (CI) engines, while noble gases eliminate nitrogen oxide (NOx) emissions by replacing nitrogen. Noble gases can increase the in-cylinder temperature during the compression stroke due to their high specific heat ratio. This paper aims to find the optimum parameters for hydrogen combustion in an argon–oxygen atmosphere and to study hydrogen combustion in all noble gases, providing hydrogen combustion data with suitable engine parameters to predict hydrogen ignitability under different conditions. Simulations are performed with Converge CFD software based on the Yanmar NF19SK direct injection CI (DICI) engine parameters. The results are validated with the experimental results of hydrogen combustion in an argon–oxygen atmosphere with a rapid compression expansion machine (RCEM), and modifications of the hydrogen injection timing and initial temperature are proposed. Hydrogen ignition in an argon atmosphere is dependent on a minimum initial temperature of 340 K, but the combustion is slightly unstable. Helium and neon are found to be suitable for hydrogen combustion in low compression ratio (CR) engines. However, krypton and xenon require temperature modification and a high CR for stable ignition. Detailed parameter recommendations are needed to improve hydrogen ignitability in conventional diesel engines with the least engine modification.

Effect of hydrogen direct injection strategies and ignition timing on hydrogen diffusion, energy distributions and NOx emissions from an opposed rotary piston engine

Opposed rotary piston (ORP) engines as a new type of internal combustion engines are free of connecting-rod mechanisms, have small engine size and mass. ORP engines have the abilities of delivering high power density. Hydrogen fuel applications in internal combustion engines contribute to nearly zero carbon emissions in the combustion processes. In this paper, the effect of hydrogen direct injection strategies and ignition timing on hydrogen diffusion, in-cylinder combustion, energy distributions, and nitric oxide (NOx) emissions are investigated using a numerical simulation method regarding this novel internal combustion engine. The results showed that hydrogen was the most unevenly distributed in the combustion chambers for the start of injection (SoI) of −68.2° crank angle (CA) after top dead centre (aTDC) among the three hydrogen injection strategies; meantime, it presented the lowest combustion efficiency, being smaller than 98.5%. The peak in-cylinder pressure ranged from 40 bar to 83 bar for the given scenarios. The combustion durations were in the range of 20 °CA ~ 30 °CA for the ignition timing of −20.85 °CA aTDC ~ −11.06 °CA aTDC. The indicated thermal efficiency was higher than 38% over early ignition cases; the energy losses in total fuel energy by cylinder walls were lower than 15%. NOx emissions factors were lower than 36 g/kWh, and they were reduced by the retarded hydrogen injection. The engine performance and NOx emissions under early hydrogen injection scenarios are less sensitive to late ignition; additionally, the crank angle corresponding to the optimal efficiency was almost the same under different hydrogen injection strategies.

Numerical study on the spontaneous ignition of pressurized hydrogen during its sudden release into the tube with varying lengths and diameters

Fuel cell vehicles (FCV) and other hydrogen systems with pressurized hydrogen has a safety hazard of spontaneous ignition during its sudden release into the tube. Tube parameter is a key factor affecting the spontaneous ignition of pressurized hydrogen. In this paper, a numerical study on the spontaneous ignition of pressurized hydrogen during its sudden release into the tube with varying lengths and diameters is conducted. The models of Large Eddy Simulation (LES), Eddy Dissipation Concept (EDC), Renormalization Group (RNG), 10-step like opening process of burst disk and 18-step detailed hydrogen combustion mechanism are employed. 6 cases are simulated based on the previous experiments. Numerical results show that the possibility of spontaneous ignition of pressurized hydrogen increases inside the longer and thinner tubes, which agrees with the experimental results. The increasing of tube length has little influence on the shock wave formation and propagation inside the tube. However, there exists critical tube lengths for the generation of Mach disk and the normal shock wave: the maximum and minimum distances for the generation of the Mach disk in 10 mm diameter tube are 7.8 and 6.7 mm, respectively. As for the normal shock wave, these critical values are 22.1 and 19.4 mm, respectively. In addition, the formation times and initial positions of Mach disk and normal shock wave are delayed inside the thicker tube. Due to the shock-affected time increases with the increasing of tube length, the temperature could rise to the critical ignition temperature and triggers the spontaneous ignition due to the sufficient tube length even though the less hydrogen/air mixture and the contact surface with lower temperature is produced inside the thicker tube. Finally, a simple time scale analysis is conducted.

External explosions of vented hydrogen-air deflagrations in a cubic vessel

The effects of hydrogen concentration and ignition location on the external explosion were experimentally investigated during vented hydrogen-air deflagrations in a cubic vessel. Hydrogen concentration ranging from 14 vol% to 50 vol% and three ignition locations (front, center, and back ignitions) were focused with the ambient temperature and pressure of 283 K and 100.5 kPa, respectively. The pressure histories and flame behavior inside and outside the vessel were recorded. Experimental results show that Helmholtz oscillation was always found for front ignition. Three overpressure peaks of Popen, Phel and Pvib resulting from the vent rupture, Helmholtz oscillation and flame-acoustic-oscillation were recorded respectively. For center and back ignitions, an additional overpressure peak Pext, generated by the external explosion, was monitored. Popen was the maximum one for front ignition while Pext became the maximum one with increasing hydrogen concentration for center and back ignitions. However, the maximum overpressure for back ignition was significantly larger than those for front and center ignitions. Only one external overpressure peak was recorded for front ignition. However, as hydrogen concentration was larger than 18 vol%, two external overpressure peaks were recorded for center and back ignitions, and the one induced by the external explosion for back ignition was significantly larger than that for center ignition. Moreover, external explosion affected significantly affects the flame evolution outside the vessel.

Experimental investigation on the dynamic responses of vented hydrogen explosion in a 40-foot container

To investigate the structural dynamics of a container subjected to a vented hydrogen explosion, 48 field tests were conducted in a 40-foot container with roof vents and an end vent. The effects of the hydrogen concentration, ignition position, and obstacles on the evolution of the dynamic responses were investigated. Three stages were generally observed for displacements: (1) At the stage of the vent rupture, the displacement could be approximated as a quasi-static response, and there was a linear relationship between the peaks of positive overpressure and displacement. (2) Structural deformation appeared as reciprocating vibration at the stage of Helmholtz oscillation. (3) The structure exhibited relatively weak irregular fluctuation when high-frequency acoustic oscillation occurred. Two types of the structural acceleration with low and high amplitudes resulting from Helmholtz oscillation and acoustic oscillation, respectively, were clearly observed. For the end-vented explosion, multiple peaks were observed for the displacement at the quasi-static stage due to the rupture, discharge, and external explosion. Moreover, the displacement was sensitive to hydrogen concentration, whereas the number of obstacles and the ignition position had significant influences on the peak acceleration for roof venting. This work conducted the fundamental explanation for the evolution law of structural responses induced by vented hydrogen explosions from the perspective of structural dynamics and enriched the experimental accumulation in a large-scale container with congestion in this field.

Numerical study on ignition and failure mechanisms of hydrogen explosion accident in Fukushima Daiichi Unit 1

This paper studied ignition and failure mechanisms of hydrogen explosion accident in the container building of Fukushima Daiichi Nuclear Power Plant Unit 1, which occurred a day after the Great East Japan Earthquake in 2011. To understand the mechanism of hydrogen explosion, an unsteady three-dimensional numerical analysis of the flow field in the container building was conducted in real time by assuming that the high-temperature hydrogen gas (500 °C) issued from the head flange of the reactor vessel. The numerical results show that the hydrogen gas spread not only on the 5th floor but also on the 4th floor of the container building covering the stairs. It was found that the hydrogen concentration on the 5th and 4th floors was highly uniform owing to the long real-time accumulation (15 h) of hydrogen, and it spread gradually from the 5th to the 4th floor through the stair. As a result, the hydrogen concentration reached the ignition level on the 4th floor (5%), which could result in the ignition of hydrogen by a tank heater on the 4th floor and the flame propagated to the 5th floor, where fast deflagration and detonation might occur because of the high concentration of hydrogen gas (19%). This scenario is consistent with the observations of failure mechanism after the explosion accident.

Large-eddy simulation of tri-fuel ignition: diesel spray-assisted ignition of lean hydrogen–methane–air mixtures

We present 3D numerical results on tri-fuel (TF) combustion using large-eddy simulation and finite rate chemistry. The TF concept was recently introduced by Karimkashi et al. (Int. J. Hydrogen Energy, 2020) in 0D. Here, the focus is on spray-assisted ignition of methane–hydrogen blends. The spray acts as a high-reactivity fuel (HRF) while the ambient premixed methane-hydrogen blend acts as a low-reactivity fuel (LRF) mixture. Better understanding on such a TF process could enable and motivate more extensive hydrogen usage in e.g. compression ignition marine engines where spray-assisted dual-fuel (DF) combustion is already utilised. The studied spray set-up is based on the modified ECN Spray A case, see Kahila et al. (Combustion and Flame, 2019) for DF combustion. The ambient pressure and temperature are 900 K and 60 bar. The hydrogen content of the LRF blend is varied systematically by changing the molar fraction , . The main added value of the study is that we extend the TF concept to 3D. The particular findings of the study are as follows: 1) Consistent with Karimkashi et al. 2020, hydrogen delays ignition also in 3D and the effect becomes significant for . 2) The ratio between the first- and second-stage ignition delay times and . Furthermore, the ratio between 3D and 0D ignition delay times is given as for all TF cases. 3) Finally, consistent with Karimkashi et al. 2020, also in 3D the high-temperature combustion heat release mode is shown to appear stronger in TF than the low-temperature combustion mode compared to DF methane–diesel combustion.

Cтабилизация горения керосино-воздушной смеси инжекцией водорода

On aircrafts at high flight speeds, the ramjet engine (ramjet) is of greatest interest at present, the efficiency of which can be increased by using the thermochemical fuel conversion (TFC) technology. Some aspects of the operation of such an engine can be simulated numerically. In this work, a theoretical and experimental study of the processes in the combustion chamber is carried out, and a method is proposed for stabilizing the combustion of a keroseneair mixture by injecting molecular hydrogen into a direct-flow combustion chamber. An experimental setup created at TsAGI was used, on which the influence of the hydrogen temperature, the location and size of the mass supply area on the combustion process was studied. For a theoretical study, the corresponding numerical technology was applied based on the Navier-Stokes equations using the Spal-rt-Allmares turbulence model, implemented in a complex of computer programs developed at the Research Institute of Mechanics of Moscow State University. Numerical modeling solved two problems. The first concerned the conditions for the ignition of molecular hydrogen supplied to the flow-type igniter, and the second - the conditions for the stabilization of the combustion of a kerosene-air mixture by a hydrogen flame. Based on the results of calculations, it was found that the ignition process is facilitated by an increase in the temperature of hydrogen and the power of its injection. The position and size of the hydrogen source is less influential. In the course of a comprehensive study by the method of a full-scale and computational experiment, the characteristic features of the flow structure in the channel, including the formation of a detonation wave, were revealed, and the possibility of controlling combustion by hydrogen injection was shown.

Simulation of Hydrogen Fuel Combustion in Neon-oxygen Circulated Compression Ignition Engine

The elimination of NOx emissions for hydrogen combustion in the compression ignition (CI) engine is the primary concern, therefore replacing nitrogen with noble gas is one of the solutions to the eliminated the NOx emission. Current research trend focuses on oxygen-argon as the most suitable working. When using argon, external heating for intake is required for low compression ratio (CR) engines. Hence, neon is another potential solution because it has a high specific heat ratio that is as high as other noble gasses with the specific heat capacity, Cp, which is almost identical to nitrogen. This advantage pointed to neon as the best nitrogen replacement option. This paper aims to study neon-oxygen as the working gas for stabilization of the hydrogen ignition with the standard ambient intake condition. In addition, the optimum intake temperature and suitable CR was also determined from the analysis of the combustion properties. A computational analysis was performed using Converge CFD software with specific initial temperature and CR conditions base on Yanmar NF19SK engine. The study showed that the mean initial hydrogen temperature in the neon-oxygen atmosphere was lower than that of oxygen-argon. However, the initial minimum temperature needed for compression ratio 10:1 is 310 K, with a slightly unstable ignition and potential of knock. Hence, the most suitable initial temperature is at 340K. For higher CR, external heating on intake gas is no longer required; hence the engine output was increased. Neon-oxygen is available in CI engine hydrogen combustion at a higher compression ratio with no modification. Analysis of the injection parameters and control of heat loss in the neon-oxygen atmosphere is needed for hydrogen combustion strategies for this type of engine.

On explosion characteristics of premixed syngas/air mixtures with different hydrogen volume fractions and ignition positions

This study analyzes the effect of both ignition position and hydrogen volume fraction on the flame propagation structure and overpressure wave. The interpretations are based on the propagation dynamics of the premixed syngas/air explosions at different ignition positions with different hydrogen volume fractions investigated at a constant equivalence ratio of 1 in a semi-open rectangular combustion chamber experimentally. The initial temperature T0 and pressure p0 were 298 K and 0.1 MPa, respectively. The experimental results are consistent with those obtained using the proposed analytical theory, indicating that the proposed theory predicts the early flame acceleration stage and the flame front motion well under some limited conditions. Flame–wall interaction and combustion instability decrease the theoretical flame front position than the experimental value and increase the wall contact time than the experimental value in some cases. At the same ignition location, both the overpressure growth rate and the maximum overpressure increase with increasing hydrogen volume fraction. When ignited at 0 mm off the closed end, the increased volume fraction of hydrogen would cause the initial location of the tulip flame to approach the opening end of the duct, but at an earlier time. The closer the ignition position to the opening end is, the more intense the overpressure and flame leading edge oscillation are, and the period of overpressure is similar to that of the flame oscillation. Finally, the ignition position and hydrogen volume fraction have obvious effects on overpressure, the structure and development of the flame front.

Effect of inert and reactive gas additives to hydrogen and air on blow-off of flame at hydrogen release from microleakage

This paper presents experimental data on the effect of inert (He, N2, Ar, CO2) and reactive (СН4, O2, CF3Br, (CH3O)3PO) gas additives to hydrogen and ambient air on flame blow-off during diffusion combustion of a hydrogen microjet emanating from a micronozzle into air. It is found that the addition of the above gases to hydrogen narrows the microjet velocity range of stable combustion of hydrogen. For hydrogen with the additives studied, the critical velocity of flame blow-off depends primarily on the mean molecular weight of the combustible mixture. When the gases are added to the air surrounding the diffusion flame, the critical velocity of flame blow-off is determined by their inhibiting effect on the chemical reactions of hydrogen oxidation. The results can be used to determine the minimum concentrations of flame-suppressing additives required to prevent the ignition and combustion of hydrogen in its accidental releases.