Maximum Explosion Pressure Research Articles

Experimental study on the effect of initial accumulation pattern on gas explosion and explosion suppression in a real roadway

In real roadways, gas is prone to accumulate, which in turn can lead to explosive hazards. The state of gas accumulation has a significant impact on the degree of disaster caused by gas explosive hazards. In this study, gas explosion propagation in complex situations was investigated in the actual roadway. The mechanism of explosion suppression was explored from the perspective of kinetic analysis of chemical reactions. It is found that the peaks of explosion pressure occur in the gas accumulation zone. The length of explosion flame is 3–5 times larger than that of the initial gas accumulation zone. As the initial accumulation volume increases, the flame propagation velocity (FPV), maximum explosion pressure (MEP) and flame zone length all increase. ABC Powder can effectively suppress explosion flames of gas with different gas accumulation patterns. A prediction model of gas explosion wave energy in the roadway is proposed. The explosion wave energy increases with increasing overpressure ratio. The explosion wave energy decays significantly after 80 m because of explosion suppression. The explosion suppression of ABC powder is a synergistic effect of surface cooling, dilution, physical isolation and chemical mechanisms. The free radical ions generated by the pyrolysis of ABC powder destroy the structure of the flame and make the reaction more difficult, which corresponds to an increase in the critical flame temperature and makes the gas phase dilution effect easier to achieve.

Numerical investigation of the in situ gas explosion fracturing and the enhancement of the penetration in coal seam boreholes

AbstractPermeability enhancement of low permeability coal seams is a key tool in coal mine gas extraction and utilization. Numerical investigations are used to analyze the geometric parameters of the drilled gas cavity and the effect of initial pressure on explosion parameters to explore the potential of original gas blasting in enhancing crack penetration in coal seams. On the basis of these analyses, the changes in characteristic parameters of the coal body under blasting pressure are examined. The results show that the maximum explosion pressure tends to be close to the theoretical explosion maximum when the L/Φ is 1.67–2.5, and the mechanical effect of the explosion pressure and surge velocity on the wall reaches the optimum in the experimental group when the L/Φ is 1.67. The initial pressure and the maximum explosion pressure demonstrate a linear positive correlation, and increasing the former can effectively enhance the force applied to the hole wall. During the gas explosion pressurization stage, the cracking range of coal under pressure is 0.05 m, but the duration of peak pressure can extend the range of cracking. The combined effect of the stress and pressure fields causes elastic energy storage in the coal body to fail in the radial region of the hole wall, but regains elastic energy storage as the pressure increases. The effect of fracturing on the radial coal seam permeability of the borehole wall before and after the fracturing effect is expanded by 19.6 times, proving that in situ gas explosion in boreholes can effectively improve the gas seepage characteristics of coal seams and increase the gas recovery rate. The simulations indicate that the application of in situ gas explosion fracturing and permeation technology is limited by the increase in maximum explosion pressure and the cumulative effect time of the peak pressure. This provides a theoretical basis for understanding the constraints of gas explosion fracturing and permeation technology.

Research on Explosion Pressure Characteristics of Long Flame Coal Dust and the Inhibition Effect of Different Explosion Suppressants.

To discuss the inhibition of long flame coal dust explosion pressure, NaHCO3, KHCO3, and NH4H2PO4 are selected as explosion suppression dust for explosion pressure tests under different conditions. The results show that when 25-38 and 38-45 μm coal dust are mixed in 1:1 ratio, the maximum explosion pressure is the largest, the maximum pressure is 0.79 MPa, and the maximum pressure rise rate is 74.89 MPa·s-1. The suppression dusts have good inhibition effect on explosion, the order of inhibition is NaHCO3, KHCO3, and NH4H2PO4 from the smallest to the largest. With the reduction of particle size of NH4H2PO4, its inhibition effect on explosion pressure is increasing, because more NH4H2PO4 particles move around coal dust particles, blocking the heat transfer and kinetic energy exchange. The above three suppression dust and their suppression methods can provide important data for dust prevention and control and have certain reference significance for carrying out explosion suppression work.

Evolution characteristics of ethyl ether spray explosion process in 20L near-spherical vessel

As a biofuel with a wide range of uses, ethyl ether leakage may cause serious spray explosion accidents during storage and transportation, however, the evolution characteristics and process mechanism of ethyl ether spray explosion have not been thoroughly studied. Therefore, the effects of material temperature and ambient temperature on ethyl ether spray explosion at different concentrations are studied by means of spray explosion experiment system. In this paper, the development of ethyl ether spray explosion with a mass concentration range of 107.1–392.7 g/m3 was studied at different ambient temperature and material temperature. Where the ambient temperature range is 298.15–323.15 K, and the material temperature range is 298.15–323.15 K. Moreover, in this paper, the risk of spray explosion is more clearly understood through the classification of deflagration index, and the explosion characteristics of spray explosion are analyzed comprehensively according to the boiling point as the dividing line. The maximum explosion pressure and its arrival time, the rate of rise of the maximum explosion pressure and its arrival time are used as the basis to evaluate the effect of the explosion process of ethyl ether spray. The results show that when the ambient temperature is lower than the boiling point temperature of ethyl ether, the increase of ambient temperature has little effect on the explosion characteristics of ethyl ether spray. When the ambient temperature is higher than 308.15 K, the maximum explosion pressure and maximum rate of pressure rise of ethyl ether spray explosion increase. At medium and low concentrations(107.1 g/m3, 178.5–249.9 g/m3), the increase of ambient temperature is conducive to the rapid development of spray explosion, and the arrival time of maximum explosion pressure and pressure rise rate both show a decreasing trend. However, under the influence of incomplete combustion at high concentration, the explosion development rate is reduced. At lower material temperature, the maximum explosion pressure and the maximum rate of pressure rise increase with the increase of material temperature. When the material temperature is higher than 303.15 K, the ethyl ether droplet temperature is higher than the ambient temperature, and the heat loss of the droplet has a certain inhibition effect on spray explosion. Especially when the material temperature is high, the inhibition effect is more significant, so when the material temperature rises to 323.15 K, the maximum rate of pressure rise decreases. The effect of ambient temperature on the explosion grade is more obvious than that of the material temperature, and the effect on the explosion characteristics of ethyl ether spray is also greater.

Experimental and Numerical Studies on the Explosion Characteristics of Ethanol–Air Mixtures under Aviation Conditions

As a representative renewable biofuel, ethanol can reduce mankind’s dependence on petroleum resources and the emission of greenhouse gases and other pollutants. In recent years, the application of ethanol in the aviation field has begun to be a concern of scholars. As ethanol is a flammable liquid, it is significant to study its explosion characteristics in aviation conditions from a safety perspective. In this work, at 20 kPa, the explosion characteristics of ethanol–air mixtures (concentration 6~12%) were experimentally and numerically studied under an initial temperature range of 303 K~363 K. The effects of the initial temperature and concentration on the maximum explosion pressure, maximum rate of pressure rise, explosion time, and fast burning time were analyzed. In addition, the heat loss fraction and sensitivity analysis were examined and discussed. The main conclusions are as follows: A linear relationship exists between the maximum explosion pressure and the reciprocal of the initial temperature. The maximum rate of a pressure rise appears to decrease or at least approach a constant value as the initial temperature increases. The explosion time is significantly dependent on the concentration. At a constant concentration, the proportions of heat loss are approximately constant except for 12%. In our sensitivity analysis, R1 (H + O2 <=> O + OH) was the dominant elementary reaction.

Experimental study of explosion parameters of hybrid mixture caused by thermal runaway of lithium-ion battery

The explosion characteristics of the runaway battery vented gas (BVG) was studied using an 8 L column type device. The effects of ambient temperature, turbulence condition, and graphite dusts-ejected along with the BVG on the explosion process-were investigated. At 25 ℃, the explosion limits of pure BVG, the maximum explosion pressure (Pmax), and the maximum rate of explosion pressure rise (dP/dt)max is 10.8–45.8% by volume, 0.62 MPa, and 37.6 MPa/s, respectively. At 80 ℃, the three parameters changed to 10.4%− 46.5%, 0.49 MPa and 35.5 MPa/s. Moreover, these three parameters changed to 10.2–47.5%, 0.45 MPa and 33.3 MPa/s at 120 ℃. The increase in temperature reduced Pmax of BVG. While turbulence had little effect on the explosion pressure of BVG, it has significantly affected the dP/dt value. Adding graphite dusts helps BVG get to Pmax at a much lower volume concentration. As temperature increased, this effect became greater. Also, the graphite dusts can reduce the time of BVG to attain the Pmax value after igniting – the maximum reduction is from 325 ms to 158 ms. As ambient temperature increased, the combustible gas molecules were reduced, resulting in a lower Pmax value. The heat released from the BVG explosion drives the graphite involving dust explosion when oxygen is excessive. The above findings can provide a reference for the prevention of environmental explosions caused by the thermal runaway of lithium-ion batteries in process industry.

Experimental and numerical investigation of combustion characteristics of carbon-free NH3/H2 blends in N2O

A detailed experimental and numerical investigation of the combustion characteristics of carbon-free NH3/H2 blends in N2O was performed in the present work. The experiments with various hydrogen fractions (α = 0–1.0) and equivalence ratios (φ = 0.6–1.4) were performed at ambient pressure (1 atm) and temperature (283 K) in a standard 3.375-L cubic combustion vessel. The explosion behaviors (maximum explosion pressure Pmax and maximum pressure rise rate (dp/dt)max) were obtained from the pressure-time curves. Further, the combustion characteristics (e.g. laminar burning velocity (SL), thermal expansion ratio (σ), flame thickness (δ), effective Lewis number (Leeff) and Markstein length (Lb)) were calculated numerically by means of chemical kinetic analysis using Zhang's mechanism (Zhang et al., Combust. Flame, 2017, 182: 122–141). Besides, sensitivity analyses of the explosion pressure and laminar burning velocity were performed to identify the contribution of dominant elementary reactions. The results show that, for combustion supported by N2O, the flame instability and the potential of deflagration to detonation transition (DDT) should be considered for the evaluation of Pmax and (dp/dt)max. Moreover, the hydrodynamic instability of premixed H2/NH3/N2O flame reaches its peak near the stoichiometric ratio and increases monotonously with the hydrogen fraction. The diffusion-thermal instability is more significant in the leaner mixture, and it is not invariably enhanced with the increase of hydrogen fraction but is relevant to the composition of the mixture. In addition, the sensitivity analysis of explosion pressure demonstrates that R80 (N2O + H2N2+H2O) and R70 (N2O+(M) = N2+O (+M)) are the most dominant reactions contributing to the pressure rise. The sensitivity analysis of laminar burning velocity shows that R70 (N2O+(M) = N2+O (+M)), R71 (N2O + HN2+OH) and R80 (N2O + H2N2+H2O) are the most dominant reactions enhancing laminar burning velocity.

Effects of dust concentration, particle size, and crude oil concentration on the explosion characteristics of oil-immersed coal dust

To investigate the explosion hazards of oil-immersed coal dust in co-existing mine areas, the explosion characteristic parameters of coal dust under different particle dimensions, coal dust concentration, and oil-immersed concentration were studied in a 20-L explosion chamber. The maximum explosion pressure of oil-immersed coal dust first decreases and then increases as coal dust particle size increases. For oil-immersed concentration samples between 2 and10 wt.%, the Kst value, and maximum explosion pressure of the oil-immersed samples were higher than those of the raw coal counterpart. The maximum explosion pressure of oil-immersed samples was 7.49%, 4.10%, 5.7%, 7.13%, and 4.10% higher than the raw samples. Moreover, when the oil-immersed concentration was 6 wt%, the minimum explosion concentration (MEC) of finer particles was the lowest, while the MEC for large particles was the highest. The impact mechanism of coal dust concentration on maximum explosion pressure is that the number of coal dust particles affects the distance between particles and heat transfer efficiency. The influence mechanism of particle size on the explosion of oil-immersed coal is that the particle size can reflect the specific surface area size, which affects the diffusion of oxygen in particles and the rate of combustible volatiles released by particles. Hydrocarbons released from the crude oil via heating and the complex organic molecules generated during high-temperature pyrolysis produced simpler hydrocarbons, generating hydrogen and higher temperatures that accelerated the onset of explosions and increased coal dust explosion intensity. These experimental results were of use to process safety working and can help prevent coal dust explosion accidents in underground coal mines.

Study on influence of magnetic field on ethane explosion mechanism

To explore new gas explosion prevention and control technology, experiments on the influence of magnetic field on the explosion characteristics of ethane were carried out, and the effect of magnetic field on the explosion pressure, product component changes and other explosion characteristics were obtained. CHEMKIN-PRO software was used to simulate the explosion chain reaction process and determine the key radicals and main reaction paths. The forces of radical particles under magnetic fields were analyzed through theoretical calculations. Fukui function and population analysis of elementary reaction C2H6+·OH=·C2H5 + H2O were carried out by Material Studio. The results showed that magnetic fields decreased the ethane maximum explosion pressure, pressure rise rate, and average flame propagation speed, while increasing CO and CO2 production and decreasing residual ethane. ·H, ·O, ·OH, ·CH3, and ·C2H5 were identified as the key radicals in the ethane explosion process, with ·OH having the greatest effect on the ethane consumption rate. H5 has the strongest nucleophilic sensitivity and C2 has the strongest electrophilic sensitivity, which leads to that H5 and C2 are the most easily broken sites of chemical bonds during C2H6 explosion. C2H6+·OH has the strongest adsorption capacity and the most unstable structure, and the two are more likely to react. The magnetic field affects the explosion of ethane by weakening the bond energy of CH, and the change of bond energy directly affects the enthalpy change, resulting in the change of ethane consumption rate. At the same time, the magnetic field will also change the migration trajectory of ·OH by applying the magnetic field force, reducing the multi-chain reaction rate of ·OH participation, thereby reducing the chain reaction rate of ·HCO → CO → CO2, showing that the magnetic field has a significant inhibitory effect on the explosion of ethane.

Experimental study of methane explosion containing coal dust in flame instability and pressure variation process

It is important to understand the evolution process of an explosion flow field for accident prevention. This study investigated the effects of low coal dust concentrations on gas explosion characteristics by incorporating coal dust into air-methane gas mixtures (the volume fraction of methane is 12.5%, 9.5% and 6.5%, respectively) in a cylindrical combustion chamber for conducting explosion experiments. Pressure measurement and laser schlieren technology were used to record explosion pressure variations and to capture flame schlieren images. The results revealed that the flame radius shrank with elevated coal dust concentration at the initial stage of explosion. At a methane concentration of 6.5%, the flame appeared to float up, and the explosion reaction intensity increased with higher coal dust content. The flame spread out in a spherical morphology was observed at 9.5% and 12.5% methane concentrations. With elevated coal dust concentration, increased the maximum explosion pressure and pressure rise rate first, then decreased it. The dynamic coupling of flame instability propagation and pressure had a limited effect on the rising explosion pressure. In addition to providing experimental data for validating and enhancing the kinetic mechanism of gas-dust chemical reactions, these findings provide in-depth insight into prevention and management of coal-mine catastrophes.

Investigation on the lower flammability limit and critical inhibition concentration of hydrogen under the influence of inhibitors

Hydrogen is considered a leading clean energy carrier and versatile industrial raw material, playing a crucial role in driving down greenhouse gas emissions. Ensuring the safe utilization of hydrogen holds paramount significance. The present study investigated the variation law of the lower flammability limit of hydrogen under the influence of inhibitors (carbon dioxide, nitrogen, and heptafluoropropane) through experimental testing. The critical inhibitory concentration required for complete suppression was determined. Additionally, the explosive characteristics under the influence of inhibitors were evaluated, and the inhibitory mechanism was analyzed in conjunction with chemical kinetics. With an increase in the quantity of inhibitors added, there was a corresponding increase in the lower flammability limit of hydrogen, as demonstrated by the results. When 10% volume fraction of heptafluoropropane was added, the lower flammability limit of hydrogen increased by 94.74%. At lean Burn conditions, the inhibitory effect of carbon dioxide on the maximum explosion pressure, adiabatic flame temperature, and heat release rate of hydrogen was higher than that of nitrogen. When the heptafluoropropane inhibitor was added, the explosion pressure, adiabatic flame temperature, and heat release rate of Hydrogen -Air flame showed an increasing trend followed by a significant decrease. As the addition of heptafluoropropane inhibitor increased, the consumption of active free radicals such as hydrogen radicals and hydroxyl by fluorine-containing free radicals interrupted the chain reaction, thus inhibiting the combustion reaction process. Additionally, it was determined that the critical inhibitory concentrations of the three inhibitors for hydrogen with different volume fractions are ranked in order from low to high as heptafluoropropane < carbon dioxide < nitrogen. The research results can promote the safe utilization of hydrogen energy.

Comparative Analysis of Fire and Explosion Properties of Lycopodium Powder

Lycopodium (L.) clavatum powder, due to its uniform particle size distribution and low equilibrium moisture content, is often used as a reference material and a calibration benchmark for dust combustion and dust explosion studies. The aim of the study was to determine its fire and explosion parameters, compare them to values obtained in the previous literature findings, and assess the appropriateness of using lycopodium powder as a reference material. The research included the determination of minimum ignition temperatures of dust layer and dust clouds, spontaneous ignition behavior, and explosion characteristics of dust clouds including maximum explosion pressure, maximum rate of explosion pressure rise, and the lower explosion limit of the air/dust mixture. The results reveal that the maximum equipment temperature used with lycopodium dust should not exceed 215 °C for dust thickness up to 5 mm. In order to eliminate the risk of lycopodium dust ignition, the temperature of the equipment surfaces that can come into contact with the dust cloud should not exceed 300 °C. In order to prevent explosions, the concentration of lycopodium dust in air should not be greater than 15 g/m3. Based on the obtained results, it can be seen that lycopodium fire and explosion parameters vary slightly, and its usage as a benchmark is considered legitimate.

Определение взрывоопасности сжиженного природного газа

Excess explosion pressure is one of the main indicators characterizing the explosiveness of a gas. Precise determination of the dependence of the explosion pressure on the distance allows to ensure the safe layout of production facilities with minimal economic costs. Every year, all over the world and in Russia in particular, there is an increase in energy consumption. There is a shift in the global energy system towards the large-scale use of low-carbon energy sources, which is caused by the policy of decarbonization of the fuel and energy complex as part of the fight against global warming. The advantage of operating natural gas in a liquefied state led to the development of the liquefied natural gas market in Russia, with the development of which the risk of accidents at the facilities in this segment of the economy increases. However, the existing methods do not allow calculating the explosion pressure for a mixture of low molecular weight hydrocarbons, which is liquefied natural gas. A new formula for calculating the explosion pressure is proposed considering the composition of the liquefied natural gas. The conducted studies showed the possibility of using the proposed formula to determine the parameters of the explosion of mixtures of low molecular weight hydrocarbons, in particular, liquefied natural gas. It is shown that, despite the linear dependence of the change in the maximum explosion pressure of methane on the change in the percentage of impurities of its homologues, the expected composition of the mixture components differs from that calculated according to the Le Chatelier rule, which can be taken into account in further studies. A comparative analysis of the explosion pressure according to the proposed methodology and the standard showed deviations for grades V, B, and A were 34.99; 20.45; and 2.1%, respectively, which significantly reduces the possible consequences of the explosion and creates a significant error in determining the safe distance. In order to exclude the possibility of obtaining underestimated indicators of the explosion pressure of the liquefied natural gas, it is recommended to use an adjusted methodology.

Effects of mixing CO and H2 as main components on the explosion characteristics and dynamics properties of methane

This study experimentally examines the effect of the addition of mixed gas (C2H6 + C2H4): (CO + H2) = 1:5 on the explosion characteristics of methane (volume fractions of 7%, 9.5%, and 11%) The explosion pressure, rate of increase in explosion pressure and time to reach the maximum explosion pressure are monitored. The mole fraction of radicals, sensitivity of CH4, and rate of production (ROP) are then calculated. The results show that the addition of mixed gas has the greatest impact on the explosion characteristics of the 7% methane mixture. For methane mixture of 7%, 9.5% and 11%, R1, R107 and R104, respectively, have the greatest impact on the methane sensitivity. The impact on the methane sensitivity in descending order is 7% > 9.5% > 11%. R1 (H + O2 = O + OH) was the most promoting and primary reaction for the consumption of O2 and the production of OH.

Explosion behaviors of hydrogen-nitrous oxide mixtures with propane addition

In the present work, the explosion of hydrogen-propane-nitrous oxide mixtures with various equivalence ratios (ϕ=0.2-2.4), propane fractions (ωC=0-1.0) and initial pressures (P0=50-100 kPa) at ambient temperature (288 K, room temperature) was experimentally performed in a standard 3.375-L cubic vessel. The maximum explosion pressure (Pmax), maximum pressure rise rate ((dp/dt)max) and explosion time (te) were obtained in light of pressure–time curves, and the normalized maximum explosion pressure (Pmax/P0) and normalized explosion time (td/te) were analyzed as well. Moreover, the adiabatic pressure (Pad) and laminar burning velocity (SL) were also calculated for argumentation. The results indicate that with the increase of ωC, Pmax and (dp/dt)max both present three characteristic variation trends for different ϕ, while the inflections of Pmax-ϕ and (dp/dt)max-ϕ transient gradually from lean to rich mixtures. Besides, te and td/te are monotonously rising with ωC, illustrating that propane addition can remarkably decelerate the explosion process. In addition, with the increase of P0, Pmax/P0 raises monotonously and is asymptotic to Pad/P0 at ωC⩽0.2, demonstrating that heat loss decreases under higher P0. Linear dependence is also found between (dp/dt)max and P0 for any composition. Furthermore, te monotonically decreases with P0, due to the flame acceleration occurring in the combustion period. In general, the presence of nitrous oxide (N2O) with a large content makes the explosion extremely unstable, and a spot of propane can dramatically alter the explosion characteristics of H2-N2O mixtures. These results will be meaningful for the development of explosion-mitigation devices and technology in case of underlying explosion and fire hazards.

Suppression effects and mechanisms of three typical solid suppressants on titanium hydride dust explosions

The suppression effects of melamine polyphosphate, titanium dioxide and melamine cyanurate powders on titanium hydride dust explosions were studied using a 1.2 L standard Hartmann tube system, a 20-L spherical vessel testing system, a simultaneous thermal analyzer and a field emission scanning electron microscope. The experimental results showed that the three solid suppressants could effectively decrease the explosion parameters such as flame luminescence intensity, flame propagation velocity and maximum explosion pressure, et al. Because of the different suppression characteristics of the suppressants, their suppression effects on the particles combustion temperatures were significantly different. To completely suppress the dust explosion of titanium hydride, the inerting ratio of the melamine polyphosphate powders was the smallest when compared with those of the titanium dioxide and melamine cyanurate powders. In addition, the field emission scanning electron microscope was used to analyze the residues of a dust explosion. The testing results showed that the thermal decomposition residues of melamine polyphosphate powders were coating on the surface of the unburned titanium hydride particles to make them lose reactivity, that was why the suppression effect of melamine polyphosphate powders was the most effective when compared with titanium dioxide and melamine cyanurate powders.

Inhibition evaluation of modified-fly ash inhibitors in methane/coal dust deflagrations

The inhibitory efficiency of modified-fly ash inhibitors MFAC and PMFAC on methane/coal dust deflagration was experimentally evaluated. Results suggested that PMFAC was superior to MFAC because of the phosphorus-containing substances and abundant reactive radicals. The composite inhibitor first inhibited the gas-phase reactions of the homogeneous combustion in the hybrid explosion field to decrease the maximum rate of explosion pressure rise (dP/dt)max in the period 0–t1, while reducing the maximum explosion pressure (Pmax) by inhibiting the chain combustion reactions in the period t1–t2. Additionally, the impacts of MFAC and PMFAC on the microscopic reactions of hybrid methane/coal dust deflagration were numerically investigated. Results indicated that the inhibitors significantly prolonged the explosion process and decreased the peak rate of productivity (ROP) for each key reactive radical. Subsequently, the inhibition mechanism by which the PMFAC molecules interacted with the deflagration reactions of methane/coal dust was elucidated in detail. Results revealed that the elementary reactions concerning the key free radicals O, H, and OH were considerably inhibited in the gas-phase reactions. The competition for key radicals in the explosion reactions by the inhibitors indirectly inhibited the surface-phase reactions, and the synergistic effect of the radicals significantly decreased the sensitivities of the key reactions.

Experimental study on aerosol explosion characteristics and flame propagation behavior of aluminum/ethanol nanofluid fuel

Aluminum/ethanol nanofluid fuel, which exhibits superior emission and combustion properties as well as broad application prospects, is a novel clean fuel produced by dispersing aluminum nanoparticles into liquid ethanol. However, the aerosol explosion characteristics of the fuel are not clear at present. In this study, a visible closed aerosol explosion device was set up to perform the explosion experiment, aiming to investigate the explosion characteristics and flame propagation behavior of the fuel under different blending ratios (0 wt%-10 wt%) and aerosol concentrations (97.53 g/m3-214.81 g/m3). The results showed that, as the blending ratio increased, the maximum explosion pressure Pex, the maximum rate of pressure rise (dP/dt)ex, the explosion index Ka, the maximum flame propagation velocity Vmax, and the average flame propagation velocity V¯ all increased first, reaching their peak values at the critical blending ratio (4 wt%), and subsequently decreased. Similarly, for nanofluid fuel of different blending ratios, the explosion time te was first shortened and then extended, with the minimum value also occurring at 4 wt%. Moreover, an analysis of fuels’ evaporation properties was performed using TGA analysis. The morphologies and compositions of the explosion products were analyzed by SEM, EDS, and FTIR analysis. Based on the above analyses, a reaction mechanism model for the nanofluid fuel was established. This model reveals the influence mechanism of the blending ratio on aerosol explosions, explains the corresponding explosion behavior, and provides a reference for the research and development of nanofluid fuel.

Experimental research on combustible gas/air explosion inhibition by dry water

The carbon reduction policy to address environmental change has increased the storage, transportation, and use of clean energy represented by hydrogen (H2) and natural gas (mainly composed of methane, CH4). However, its risk of ignition and explosion also brought significant safety risks. Although many previous studies have studied the effect of traditional detonation inhibitors, the inhibition effect of composite explosion inhibition materials still needs further research, especially for H2 explosion inhibition. In this paper, the effect of dry water (DW), a new type of core-shell structure material, in inhibiting the explosion of combustible gases (mainly H2 and CH4) has been experimentally studied using a typical 20L spherical apparatus. The results shows that DW can significantly reduce the characteristic parameters during the ignition and explosion process of H2 and CH4. However, its ignition and explosion inhibition effect is related to the type of combustible gas. The maximum explosion pressure of CH4 is significantly reduced, but the maximum pressure reduction rate of H2 is more significantly reduced. Compared with typical dry powder inhibitors, the effect of DW inhibition in characteristic parameters during the H2 ignition and explosion is related to concentration. Moreover, the inhibition effect of DW at higher concentrations is significantly better than BC and ABC dry powders at the same concentration. The inhibition mechanism of DW on the ignition and explosion of combustible gases results from a comprehensive synergy of cooling, dilution, homogeneous radical catalytic inhibition, and heterogeneous radical annihilation. The research conclusions can provide a data basis and theoretical guidance for developing explosion inhibition technology and preventing and controlling H2 explosions.

Simulation Research on the Injection Strategy of a Diesel-Ammonia Dual-Fuel Marine Engine

Currently, most ships still rely on fossil fuels as the main source for marine engines. However, diesel as a fuel for marine engines is no longer sufficient to meet the economic requirements of shipping and emission restrictions imposed by regulations as a result of the depletion of fossil fuels and the pollution generated by their burning. This research examined the viability of employing hydrogen-carrying fuel ammonia (NH3) in marine engines to develop a low-carbon combustion technology, to address the carbon emission problem of marine diesel engines. The results demonstrate that a greater proportion of ignition fuel must be injected into the burning of ammonia due to its higher ignition energy requirements. And ammonia has a high evaporation rate, so it is important to properly extend the injection duration to lower the combustion rate and keep the maximum explosion pressure in the cylinder under control. If the injection duration of the original engine’s diesel mode is maintained in dual-fuel mode, the explosion pressure in the cylinder can increase by more than 5 MPa, exceeding the limit of the original engine. However, by extending the original engine duration, the maximum explosion pressure returned to the original engine level. The starting point of the in-cylinder combustion can be efficiently regulated by changing the injection timing. Under typical injection intervals, the heat released rate (HRR) curve shifted with ammonia injection time, and rough combustion occurred only when the injection interval between the ignition fuel and ammonia was too short. According to the simulation, with all other conditions held constant, the optimal fuel injection strategy maintains the in-cylinder pressure of the engine at the diesel engine’s original level in the dual-fuel mode. Additionally, it reduced carbon emissions by over 90% and NOx emissions by approximately 70% compared with the original diesel engine.