Maximum Rate Of Pressure Rise Research Articles

Impacts of hydrogen fraction and equivalence ratio on the explosion characteristics of ethanol/hydrogen mixtures

With the anticipated widespread integration of biofuels and hydrogen fuels within the future energy landscape, the potential explosion hazards after their release within confined spaces under the atmospheric are deserving of heightened attention. The present work takes the mixtures of ethanol and hydrogen as the objects and experimentally studies the impacts of hydrogen fraction and equivalence ratio on the explosion characteristics in a constant-volume explosion vessel at 0.10 MPa and 400 K. The data reveals that an increase in the hydrogen fraction leads to a rise in the maximum explosion pressure during lean explosions but causes a decrease during rich explosions. Nonetheless, the duration of the explosion decreases with the increase of hydrogen fraction in all the explosions. In consideration of explosion pressure, the maximum pressure rise is found to be exponential in relation to the maximum explosion pressure. However, the confidence level diminishes significantly with an increase in the hydrogen fraction. Conversely, the maximum rate of pressure rise during an explosion appears to be a function of the duration of the explosion, suggesting that the reaction rate plays a more pivotal role in determining the hazardous level. Meanwhile, the duration of fast combustion steadily occupies approximately 83 % of the explosion duration. Furthermore, the deflagration index is no more than 30 MPa*m/s, namely, ethanol/hydrogen mixture is a promising fuel with mild hazardous potential.

Research on Abnormal Starting Noise of Efficient Engine Caused by Abnormal Combustion Noise

Article Research on Abnormal Starting Noise of Efficient Engine Caused by Abnormal Combustion Noise Feng Huang 1, * , Xiaochun Zeng 1, Xili Wang 1, Xinqi Qiao 2, Yi Wang 1, Liang Fang 3, Yunhua Zhang 3, Dengcheng Liu 4, and Yonghong Deng 4 1 Jiangling Motors Co., Ltd., Nanchang 330001, China 2 Mechanical and Power Engineering College, Shanghai Jiao Tong University, Shanghai 200092, China 3 Automobile College, Tongji University, Shanghai 200092, China 4 Nanchang Automotive Institute of Intelligence & New Energy, Nanchang 330052, China * Correspondence: fhuang6@jmc.com.cn Received: 20 February 2024; Revised: 7 April 2024; Accepted: 9 May 2024; Published: 22 May 2024 Abstract: An abnormal noise problem was reported in a pickup truck equipped with a 2.0 L efficient engine during start-up. The noise was reproduced by the engine anechoic chamber bench for further analysis. NVH test (conducted through audio playback and signal filtering) showed that the noise had a signal of 1–3 kHz. Analysis through cylinder-by-cylinder oil-cutting method found that the abnormal noise completely disappeared after the fourth cylinder was cut off, indicating that the noise was related to the combustion of the fourth cylinder. The combustion characteristics of each cylinder were then analyzed in the starting condition through the Kibox combustion analyzer. The noise appeared after the first fuel injection of the fourth cylinder, and the maximum pressure rise rate was 42 Bar/°, confirming that the abnormal noise was combustion noise. Further tests on the physical fuel injection signal of each cylinder found that the fourth cylinder only had the main injection signal with no pilot injection signal. Further analysis of the synchronization signal recognition method of the model and the underlying logic of the fuel injection program showed that the synchronization signal was recognized for the first time in the starting process after the calculation moment of the 4th cylinder pre-injection program, resulting in the failure of the pre-injection calculation. Finally, the bottom fuel injection interrupt program was pushed back (60° to the crankshaft angle), ensuring smooth injection of the 4th cylinder pilot injection in the starting working condition, thus solving the abnormal noise without impacting engine performance.

Comparative effectiveness of C3-Hydrocarbons and their mixtures on suppression of hydrogen-air explosions

The next-generation energy economy relies heavily on hydrogen. Handling hydrogen during production, storage, and transportation requires risk mitigation. In this regard, the application of halide-free additives is very crucial. The present study experimentally and theoretically investigates the individual and combined inhibiting effect of propane and propene on hydrogen-air explosions. The experiments are carried out at 298 K and 1 bar, with additives ranging from 0.5 to 5% for the individual and 1–2% each for the combined effect in the 20–50% hydrogen-air mixture. Experimentally, the additive content in the stoichiometric and rich mixture decreases the explosion pressure, maximum pressure rise (MPR) rate, laminar burning velocity (LBV), and flame temperature, while increasing minimum ignition energy. For instance, the addition of 2% propane in a 50% hydrogen-air mixture, reduces the MPR rate by 98%, whereas such an effect is observed with 2.5% propene. Theoretical study shows that 3% equivalent additive augments inhibiting reactions, countering the main flame-promoting reaction R1 (H + O2O + OH) and thereby reducing LBV. Due to its low activation energy, propene consumes the active radicals twice the rate of propane, while propane not only scavenges the active radicals but also promotes oxygen consumption in the prior phase of combustion, weakening flame propagation. Overall, this approach exhibits a significant step forward in harnessing the potential of hydrogen while mitigating the safety risks associated with its use.

Effect of water injector location on combustion and performance of an HCCI engine - A CFD analysis

A homogeneous charge compression ignition (HCCI) engine is capable of producing high thermal efficiency with very low emissions. However, because of the limited upper load level constrained by knocking, the HCCI engine is not yet commercialized. Water injection can tackle this issue, enhancing the upper load limit without excessive heat release rate. However, the effectiveness of water injection depends on in-cylinder water evaporation, which in turn depends on water injection parameters. Therefore, this study is conducted to study the effect of water injector location on the combustion and performance characteristics of an HCCI engine by a computational fluid dynamic (CFD) analysis. The engine specifications and boundary conditions are taken from the literature. A three-dimensional computational fluid dynamics (3D CFD) model was developed using CONVERGE CFD coupled with detailed chemical kinetics to gain a better understanding of the phenomena of water injection in an HCCI engine. The CFD models used are validated from the available experimental data in the literature for the engine considered. Here, the water injector location is optimized based on the Water vapor distribution within the cylinder, nitric oxide (NOx) emissions, and maximum rate of pressure rise (MRPR). The results show that the water injector at 37 mm from the center of the cylinder gives better results than in other cases considered. With the optimum water injector location, the indicated mean effective pressure is increased by about 35.91% than without the water injection case. This study will be helpful in the development of HCCI engines.

Effect of Ammonia Addition on Combustion and Emission Characteristics of Diesel Engine Under Various Operating Conditions

ABSTRACT Ammonia is a carbon-free alternative fuel and a hydrogen carrier. Ammonia diesel dual fuel (ADDF) combustion mode is one of the promising ways to reduce carbon emissions in CI engines. However, present researches are mainly based on combustion and emissions for naturally aspirated diesel engine under specific operating condition. This paper aims to illustrate the impacts of replacing diesel with ammonia in a turbocharged diesel engine under various operating conditions. Hence, the effects of various ammonia substitution rate (ASR) on combustion and emission characteristics are numerically investigate by using GT-Power software for nine groups of different operating conditions with low, medium and high speeds and loads. Results show maximum 70% of input energy can be provided by ammonia for nine groups of different operating conditions, and the brake mean effective pressure (BMEP) and the indicated thermal efficiency (ITE) increases with the increase of ASR. Secondly, increasing ASR decreases the peak cylinder pressure (PCP) under different operating conditions, but increases the maximum pressure rise rate (MPRR) at certain operating conditions. Among them, under medium-speed and high-load conditions, the MPRR reaches the highest value, about 0.587 MPa/(°CA), but does not exceed 0.6 MPa/(°CA). Thirdly, increasing ASR changes the combustion mode from diffusion combustion in pure diesel operation to premixed combustion in dual fuel mode. Finally, adding ammonia reduces the NOx, CO and HC emissions, and the decrease is 15.2%–43.2%, 76.2%–82.3%, 70%–79.6%, respectively.

Effect of Equivalent Ratio and Hydrocarbon Ratio on Explosive Characteristics of Synthetic Gas

With the development of society, the importance of energy is increasing day by day, and more and more people realize the importance of energy for social development.Therefore, people began to explore energy utilization, energy exploitation, clean energy and other fields.Therefore, in order to use coal resources cleanly and efficiently and reduce the damage to the environment, the development of clean coal technology is particularly important.As a kind of clean energy, syngas has been paid more and more attention, so people pay more and more attention to the safety application of syngas. This paper explores its influence on syngas explosion by changing the equivalent ratio of syngas and the ratio of hydrogen and hydrogen.The results show that the maximum explosion pressure of syngas occurs near the equivalent ratio 1.2, the maximum explosion pressure rise rate reaches the maximum near the equivalent ratio 1.5, and the maximum explosion pressure time reaches the minimum near the equivalent ratio 1.5.The change of hydrocarbon ratio does not shift the equivalent ratio of the above result, but only changes its value. The prediction equations for predicting the maximum explosion pressure under different equivalent ratios are obtained

Effect of hydrogen blending on ammonia/air explosion characteristics under wide equivalence ratio

In order to evaluate the effect of mixing hydrogen on the explosive characteristics of ammonia, this work explored the evolution of explosion overpressure and flame propagation characteristics of ammonia/hydrogen/air mixture under different hydrogen blending ratios in closed pipelines through experimental research. Experimental results show that as the hydrogen blending ratio increase, the instability of flame increases, and flame surface changes from smooth to wrinkled. Flame propagation undergoes the evolution of jellyfish-shaped/near-spherical, finger-shaped, plane-shaped, irregularly protruding flame and tulip flame. Flame surface area is constantly changing, accompanied by violent flame tip velocity pulsations. The maximum explosion pressure and the maximum explosion pressure rise rate are consistent with the evolution law of adiabatic flame temperature. They first increase and then decrease with increase of the equivalence ratio, and their peak value appears near the equivalence ratio of 1.1. On the contrary, the explosion duration and rapid combustion period first decrease and then increase with increase of equivalence ratio, and decrease monotonically with increase of hydrogen blending ratio. The conclusions obtained in this work will contribute to the structural design of flame arresters and the formulation of explosion venting strategies during the preparation, transportation and utilization of ammonia/hydrogen mixtures.

Study on Explosion Characteristics and Mechanism of Electrostatic Spray Powder.

In order to fully understand the explosion risk of electrostatic spraying powder, corresponding preventive measures are put forward. The explosion characteristics, ignition sensitivity, and flame propagation of three typical electrostatic spraying powders were tested using a 20 L spherical explosion test device, a G-G furnace test device, and a Hartmann tube test device, and the explosion process and mechanism of electrostatic spraying powders were discussed. The results show that the maximum explosion pressure and the maximum explosion pressure rise rate increase first and then decrease with the increase in mass concentration. The maximum explosion pressure and the maximum explosion pressure rise rate of acrylic powder coating are the largest, which are 0.75 and 85.4 MPa/s, respectively. The shortest burning time is 97.5 ms, and the highest explosion danger level is 23.46 MPa·m/s. The flame propagation of electrostatic spraying powder develops slowly; the flame front spreads linearly and the average flame velocity increases first and then decreases. The explosive development process of powder coating particles is concentrated in the three-phase system of solid particles, molten particles, and pyrolytic gasification combustible gas, which goes through the kinetic process of particle heating melting, cross-linking curing, pyrolytic gasification, combustion, and extinction.

Research on explosion hazard and prevention of ultrafine aluminium powder based on orthogonal matrix analysis

This study investigated the coupled effects of multiple factors, namely dust mass concentration, dust particle size, and oxygen volume concentration, on the explosion intensity of ultrafine aluminium powder (UAP); the study determined the weight of each factor by using an orthogonal experimental design. Explosion intensity was evaluated using the maximum explosion pressure (MEP) and MEP rise rate (MEPR) of UAP. Explosion tests were performed using a 20 L standard spherical explosive device. A weight matrix for the explosion intensity was calculated. The results revealed that the MEP and MEPR increased most with the oxygen volume concentration. They also increased with the dust mass concentration to a lesser extent. The dust particle size had the smallest effect; the MEP and MEPR initially increased and then decreased as the particle size increased. The weights for oxygen volume concentration, dust mass concentration, and dust particle size were 69.191%, 18.761%, and 13.038%, respectively. The optimal factor combination for minimizing intensity was a dust mass concentration of 500 g/m3, an oxygen volume concentration of 9 vol%, and a dust particle size of 0.172 µm. On the basis of these findings, the study proposes industrial explosion-proofing countermeasures to increase the safety of production in aluminium-related enterprises.

Effect of initial pressure on hydrogen/propane/air flames in a closed duct

To investigate the flame propagation characteristics and chemical kinetics of premixed propane/hydrogen/air mixtures at elevated pressure, a series of experiments on propane/hydrogen/air mixtures with varying initial pressures (P0 = 100–300 kPa) and equivalence ratios (φ = 0.6–1.4) at a hydrogen fraction of 0.6 and an ambient temperature of 298 K were carried out in a closed duct with an aspect ratio of 15. The chemical kinetics of the elementary reaction were analyzed numerically. The results revealed that the combustion-induced rapid phase transition (cRPT) occurred in the premixed C3H8/H2/air flames. Both the combustion pressure and flame propagation velocity increase with initial pressure except at P0 = 300 kPa, where the flame propagation velocity decreases. Moreover, the linear dependence between the laminar burning velocity and peak mole fraction [H + O + OH]max was found by the effect of initial pressure on the peak mole fraction (H, O, OH). The explosion pressure Prea and the maximum rate of production of free radical H/O show excellent correlations. The maximum rate of pressure rise can be predicted by the maximum heat release rate (HHR). These results provide essential data on elevated-pressure duct accidents and have important implications for explosion prevention.

Fabrication of Al@AIH@PVDF metastable composite film with enhanced laser ignition ability and combustion performance

Laser ignition technology has garnered significant attention for energetic materials in recent years, offering advantages over traditional electrical initiation methods, notably in mitigating issues related to stray currents and electromagnetic interference. Moreover, it can facilitate multi-point synchronous ignition. However, the persistent challenges of high ignition thresholds and delays in energetic materials necessitate effective resolutions. In this study, we address these challenges by converting the inert Al2O3 layer on the surface of aluminum powder into the active compound Aluminum Iodate Hexahydrate ([Al(H2O)6](IO3)3(HIO3)2, AIH) to prepare an Al@AIH@PVDF energetic composite film (ECF) with the aim of reducing the laser ignition threshold and delay of Al@PVDF ECF. The Al@AIH@PVDF ECF was synthesized through a simple wet chemistry method and a rapid evaporation process suing a simple, environmental-friendly, and cost-effective way. Differential scanning calorimetry-thermogravimetric analysis (DSC-TG) results demonstrate a lower exothermic reaction temperature (161 °C) and higher heat release (2900 J g−1) for Al@AIH@PVDF ECF. Laser ignition tests reveal a reduced laser ignition delay (11 ms) and threshold (1.59 J cm−2) for Al@AIH@PVDF ECF. Combustion experiments showcase elevated combustion flame temperature (3090 K), burning rate (4.11 cm s−1), and smaller condensed combustion products, while effectively igniting CL-20. Pressure tests indicate higher maximum combustion pressure (3.24 MPa) and pressure rise rate (4.05 GPa s−1) for Al@AIH@PVDF ECF. Finally, the reaction process and mechanism of Al@AIH@PVDF ECF was also investigated and proposed.

Effect of polyurethane foam and carbon dioxide on the suppression of hydrogen/air explosion

This study examines the influence of polyurethane porous materials and carbon dioxide on hydrogen/air explosions within an enclosed vessel. Through analysis of peak overpressure, maximum rate of pressure rise, and shock wave propagation velocity, the suppression effects on explosions in hydrogen-air mixtures with different equivalence ratios at room temperature and atmospheric pressure are investigated. Findings indicate that porous materials with a PPI (pores per inch) of 60 significantly mitigate hydrogen/air explosions across all equivalence ratios. Conversely, a PPI below 60 exacerbates the explosions. Simultaneous presentation of PPI60 porous material and a CO2 addition level of x = 2 (carbon dioxide to oxygen ratio) reduces hydrogen explosion pressure to only 13.7 kPa at "Φ = " 1.2, representing an attenuation rate of 84% and falling well below the human safety threshold of 28 kPa. Independent effects of carbon dioxide and porous materials on hydrogen explosions across various equivalence ratios are also explored. The experimental design encompasses a broad range of equivalence ratios, covering hydrogen's explosive limits. These results contribute to the design of flame arrestors and enhance understanding of explosion suppression in hydrogen systems.

Thermodynamic Reactivity Study during Deflagration of Light Alcohol Fuel-Air Mixtures with Water

In this paper, a thermodynamic and reactivity study of light alcohol fuels was performed, based on experimental and numerical results. We also tested the influence of water addition on fundamental properties of the combustion reactivity dynamics in closed vessels, like the maximum explosion pressure, maximum rate of pressure rise and the explosion delay time of alcohol–air mixtures. The substances that we investigated were as follows: methanol, ethanol, n-propanol and iso-propanol. All experiments were conducted at initial conditions of 323.15 K and 1 bar in a 20 dm3 closed testing vessel. We investigated the reactivity and thermodynamic properties during the combustion of liquid fuel–air mixtures with equivalence ratios between 0.3 and 0.7 as well as some admixtures with water, to observe water mitigation effects. All light alcohol samples were prepared at the same initial conditions on a volumetric basis by mixing the pure components. The volumetric water content of the admixtures varied from 10 to 60 vol%. The aim of water addition was to investigate the influence of thermodynamic properties of light alcohols and to discover to which extent a water addition may accomplish mitigation of combustion dynamics and thermodynamic reactivity.

Study on the Synergistic Suppression Effect and Mechanism of N2/Ultrafine Water Mist on Liquefied Petroleum Gas Explosion.

Liquefied petroleum gas (LPG) is widely used for its cleanliness and high efficiency in industry and city life. In order to improve the suppression effect on LPG explosion, a constant volume combustion bomb was used to investigate the synergistic influence of N2/ultrafine water mist on the explosion and combustion characteristics of 6% premixed LPG/air gas. The results showed that (1) the effect of a single ultrafine water mist on suppressing LPG explosion is unstable. When the concentration of ultrafine water mist is low, the flame acceleration in the initial stage of explosion is promoted, and when the ultrafine water mist with a mass fraction of 420 g/m3 is introduced, the maximum pressure rise rate increases. (2) The combination of N2/ultrafine water mist has a synergistic effect on LPG explosion. Compared to the individual suppression effects, the combination of N2/ultrafine water mist showed more effective suppression on the explosion pressure, flame propagation, and flame instability of LPG explosion. (3) Through the mechanism analysis, it is found that the combined action of N2/ ultrafine water mist can better reduce the mole fraction and ROP peak of active free radicals such as H, O, and OH by inhibiting the main reaction of generating H, O, and OH radicals during the explosion of LPG, resulting in the reduction of flame free radicals in the explosion system, thus effectively inhibiting the chain reaction of ignition and explosion of LPG. This research can provide guidance for a better understanding and implementation of gas-liquid two-phase suppression technology for LPG explosion.

Research on explosion venting characteristics of CH4/H2/Air mixture in square explosion vessels

Hydrogenation of methane (CH4) is an important means of achieving energy savings and large-scale hydrogen (H2) transportation. Explosion venting is considered to be an effective method to reduce the risk of gas explosions. To investigate the parameters of the explosion characteristics of CH4/H2/Air premixed fuel under venting conditions, the explosion characteristics and the dynamic propagation law of venting flame in CH4/Air mixtures with 5% concentration were studied in 20 L and 40 L square explosion venting vessels. The development process of flames inside vessels, the evolution characteristics of explosive venting flames, and the changes in explosion pressure were tested using a high-speed camera and pressure sensors. The maximum explosion pressure, the maximum explosion pressure rise rate, and the maximum flame velocity increased first and then decreased with the addition of H2. However, the maximum flame length increased continuously with the increase of H2. With the increase of hydrogenation, the maximum flame area showed an exponential increase. At equivalence ratio less than 1, the effect of hydrogenation on the flame area was much attenuated than that at equivalence ratio was greater than 1.

Aspects of the combustion variability analysis at an automotive engine fuelled with hydrogen

Over the last decades, the use of the alternative fuels was one of the main research activities for specialists in the field of internal combustion engines. The development of the modern automotive engines is constantly challenged by the more severe emission legislation. The engine emissions levels and the fuel efficiency are directly influenced by the engine operation, reproduction of the combustion phases from one cycle to other, cyclic dispersion during combustion process being important. In general, the use of alternative fuels in internal combustion engines provides an improvement of the energetic and pollution performance, or just a slight improvement of them, but the study of the combustion process must be completed with aspects regarding the cyclic variability. In particular, using this alternative fuel, a study of cyclic variation of the combustion process would be necessary in order to establish if the normal operation of the engine can be ensured. The paper presents some aspects of the analysis of the cyclic variability at a spark ignition engine fuelled with gasoline and hydrogen. During the engine operation at the regime of 2500 rev/min speed and 55% engine load, a number of 250 consecutive combustion cycles was recorded for classic fuel use and for hydrogen use. The coefficient of cyclic variation (CCV) or the coefficient of variation (COV) is determined for different combustion parameters such as maximum pressure, maximum pressure rise rate and mass fraction burned, defined by angles at which the conventional fractions of 10%, 50% and 90% of the heat of reaction is released. Thus, the values of the COV for maximum pressure (COV)pmax, maximum pressure rise rate (COV)dp/dα, angles of 10, 50 and 90% heat release as (COV)10%, (COV)50% and (COV)90% were calculated and compared with the admissible limit of 10%. The combustion variability analysis establishes the limits of the normal operation of the spark ignition engine fuelled with gasoline and hydrogen compared with the classic fuelling method.

Aspects of combustion in diesel engine at hydrogen use-a theoretical approach

The use of alternative fuel may be a viable solution in order to ameliorate the engine performance especially in terms of pollutant emissions. Among the alternative fuels that can be use to fuel internal combustion engines hydrogen can be a viable alternative fuel especially due to the advantage of reducing the carbon emission at its use as alternative fuel even for partial substitution of classic fuel. Hydrogen has good combustion properties like higher Lower Heating Value, large inflammability limits, higher combustion speed, which may has a benefic influence on combustion process. The use of hydrogen to diesel engine bring few important issues that must be solved in order to assure the normal engine operation, starting with the fuelling system and engine with the control of the combustion process. The paper presents some results obtained during the theoretical modeling of the in-cylinder process at a diesel engine fuelled with classic fuel and hydrogen. The diesel fuel is energetically substituted by hydrogen in percent’s of 25% and 30%. The influences of hydrogen use on in-cylinder maximum pressure, maximum pressure rise rate, heat release rate, combustion temperature, indicated thermal efficiency and nitrogen oxides and smoke emission levels are shown and analyzed.

Study on the Inhibition Effect and Mechanism of Ferrocene/NaHCO3 Composite Powder on Oil Shale Dust Explosion

ABSTRACT In order to increase the dispersibility of sodium bicarbonate and improve its inhibitory effect on oil shale dust explosion, this paper uses dry mechanical ball milling method to mix it with different proportions of ferrocene to obtain Fe(C5H5)2/NaHCO3 composite powder. The Hartmann experiment shows that as the proportion of ferrocene added to Fe(C5H5)2/NaHCO3 composite powder increases, the flame brightness, flame height, and flame propagation speed of oil shale dust explosion gradually decrease. The 20 L spherical explosion tank experiment showed that as the proportion of ferrocene in Fe(C5H5)2/NaHCO3 composite powder increased, the maximum explosion pressure (Pmax) and maximum explosive pressure rise rate ((dP/dt)max) of oil shale dust explosion first decreased and then increased. Therefore, the optimal ratio of Fe(C5H5)2/NaHCO3 composite powder is achieved with a compounding ratio of ferrocene at 20%. The addition ratio of Fe(C5H5)2/NaHCO3 composite powder under the optimal ratio is 23%, resulting in the best inhibition effect on oil shale dust explosion. SEM and TG-DTG-DSC experiments have shown that ferrocene and NaHCO3 play excellent roles in both physical and chemical suppression of oil shale dust explosions.

Effect of hydrogen fraction and initial pressure on the inhibition of methane/hydrogen/air explosions by NaHCO3

To explore the effects of the hydrogen fraction and initial pressure on the inhibition of methane/hydrogen/air explosions, the inhibition of stoichiometric methane/hydrogen/air explosions (hydrogen fraction ranging from 0 to 0.8) by NaHCO3 at various initial pressures (0.8 atm, 1.0 atm, 1.4 atm) was investigated in a 36 L spherical vessel. The experimental findings indicate that the effectiveness of NaHCO3 in suppressing methane/hydrogen/air explosions is significantly influenced by the hydrogen fraction and initial pressure. For a given hydrogen fraction, higher initial pressures weaken the inhibitory effect of a given NaHCO3 concentration on explosions. The drop ratios in the maximum explosion pressure for initial pressures of 0.8 atm, 1.0 atm, and 1.4 atm are 41.2 %, 19.7 %, and 15 %, respectively, at a hydrogen fraction of 0.8 and a NaHCO3 concentration of 400 g/m3. Additionally, the inhibitory impact of a given NaHCO3 concentration diminishes as the hydrogen fraction increases at the given initial pressure. An increasing hydrogen fraction decreases the drop ratio of the maximum explosion pressure while simultaneously increasing the maximum pressure rise rate and deflagration index. A thermodynamic equilibrium model for the endothermic decomposition of NaHCO3 particles was built to explore the impact of the hydrogen fraction and initial pressure on the decomposition characteristics of NaHCO3 particles of different sizes. The laminar burning velocity was derived using a theoretical model through the experimental pressure history and was calculated through detailed chemical kinetic modeling. The effect of the hydrogen fraction on the suppression mechanisms of NaHCO3 was evaluated by using the normalized laminar burning velocity. The dominant inhibition mechanism of NaHCO3 on the laminar burning velocity changes from physical inhibition to chemical inhibition with increasing hydrogen fraction.

Research Progress and Preventive Measures of Combustible Dust Explosion

The research on explosion characteristics of metal dust is reviewed. Summarize and condense the main research results in the field of dust explosion. Its contents include: explosion propagation law, lower explosion limit concentration, maximum explosion pressure, maximum pressure rise rate and ignition source causing dust explosion. Finally, some prevention and mitigation measures for dust explosion are put forward.