Jet Fire Research Articles

Analysis of Flow Field Characteristics in the Three-Phase Jet Fire Monitor Head

To enhance the jet performance of the three-phase jet fire monitor (TPJFM), an analysis was conducted on the internal flow field (IFF) characteristics of the monitor head. Using the volume of fluid method, the impact of key structural parameters, such as the powder-pipe bending angle and the supporting blade length, on the turbulent kinetic energy (TKE) of the IFF, the velocity distribution uniformity at the nozzle outlet, and the pressure drop (PD) between the inlet and outlet of the internal flow field, was analyzed. The study revealed that increasing the bending angle of the powder pipe will lead to a significant improvement in the uniformity of velocity distribution in the IFF. Extending the supporting blade length helps reduce the average TKE at the nozzle outlet but has a minimal impact on the velocity distribution uniformity and the PD between the inlet and outlet. Reasonable design of the distance between the supporting blades and the bending section of the powder pipe can improve the IFF characteristics, reducing local pressure losses and peak TKE. The research results can effectively improve the IFF characteristics, enhance jet performance, and provide theoretical basis and technical support for the design and optimization of the TPJFM.

Experimental and theoretical study on the burning and pulsation behaviors of hydrogen-containing and hydrocarbon jet flames

Hydrogen-containing and hydrocarbon fuels have been widely used in industrial production. Jet fires involving these fuels emerge frequently after leakage or explosion accidents for gas pipelines and processing equipments. To reveal the influencing mechanisms of inclination angle on the pulsation behaviors of jet fires, the burning experiments of hydrogen, syngas, methane and propane jet fires with a nozzle diameter (D) of 15 mm, inclination angles (θ0) of 0°∼90°, fuel flow rates (Qf)of 2.5–40 L/min were conducted. The variations of the global and spatial pulsation frequencies with inclination angle and fuel flow rate are sensitive to the fuel types. Subharmonic pulsation was found at large fuel flow rates (Qf>Qcri). For hydrogen-containing jet flame, a transition from natural pulsation to subharmonic pulsation occurs at a critical inclination angle (θcri). In this case, the transition height where the local pulsation frequency begins to be dominated by subharmonic pulsation, increases with the inclination angle. The local Richardson number (Riy) at the transition height is close to 1. The interaction between the inner and outer vortices increases with the decrease of inclination angle, resulting in decreased natural frequency at the nozzle exit. With the theoretical velocity and flame width at y/D = 2, a unified dimensionless model of natural pulsation frequency was developed, Sty=0.411/Fry0.5, reasonably predicting the natural pulsation frequency of jet flames under different conditions.

Carbon fibres: Effect of various thermo-oxidative environments on structural and performance damage, both alone and in composites

This study examines the effects of heat and fire on the physical, mechanical and electrical properties of carbon fibre and those in carbon fibre reinforced composites (CFRCs). Carbon fibres were exposed to controlled heating (thermogravimetric analysis (TGA) and a tube furnace) in inert and air (oxygenated) environments and simulated fire (cone calorimetry at 35–75 kW m−2 and jet fire (propane burner) of 116 kW m−2) atmospheres. In inert atmospheres there was a minimal effect on the properties of carbon fibres, but in an oxygenated environment, significant oxidation began at temperatures ≥550 °C, resulting in a reduction in fibre diameter, which reduced further with increasing temperature and exposure duration. Tensile strength and electrical conductivity of carbon fibre decreased with reduction in fibre diameter. CFRCs exposed to 75 kW m−2 in a cone calorimeter and direct flame in a propane burner (116 kW m−2) showed varying degrees of oxidation in CFRC plies, with surface ply fibres experiencing more oxidation and consequent reductions in fibre diameter and tensile properties compared to fibres in underlying plies, where oxidation was limited due to restricted oxygen availability. Fibres exposed to the propane burner exhibited notable damage, including pitting and internal oxidation. Despite this, the overall electrical properties of residual carbon fibres did not significantly decrease, indicating that they still pose an electrical hazard if exposed during a high heat or fire event.

Flame Geometry and Temperature Distribution of Jet Fires in Pits

Flame Geometry and Temperature Distribution of Jet Fires in Pits

Impact of plate-deflected flame on thermal runaway propagation of lithium-ion battery

Ceiling jet fire is a common phenomena in thermal runaway (TR) accidents of electric vehicle and energy storage power station scenarios based on lithium-ion battery, which is a potential risk of inducing large-scale fire spread in battery modules, but it is not been known clearly. This work investigates the influence of ceiling jet fire on TR propagation of lithium nickel cobalt manganese oxide (NCM) battery module by arranging a ceiling-like obstacle directly above the tested module. A series of overheat-induced TR propagation tests under different height (H) of ceiling-like obstacle are conducted to gain better understanding of the heat transfer mechanism. The heat transfer and average heating power of ceiling jet fire to adjacent cells are determined for the first time. Results indicate the TR propagation speed of the module accelerates with the decrease of H, and the TR propagation speed inside the cell is not affected by ceiling jet fire. More importantly, the heat transferred from cell experiencing TR to adjacent cells through ceiling jet fire (Qfl) decreases from 11087.33 J to 7872.02 J, and the ratio of Qfl to the total heat released in TR (ΔEtot) declines from 4.02 % to 2.85 % as H increases from 5 to 15 cm. Finally, the change process of contact thermal resistance between adjacent cells and its relationship with heating power are revealed during TR propagation. This work provides a basic understanding of the influence mechanism of ceiling jet fire on TR propagation, which possess important guidance for the safety protection of lithium-ion battery system.

Experimental Study on the Influence of Ignition Position on the Overpressure of Hydrogen Jet Flame.

The accidental leakage of hydrogen poses a significant barrier to the widespread adoption and development of hydrogen energy due to the potential risks of fire, explosion, and jet fire hazards. Experimental investigations have been conducted on the process of jet fires formed by igniting hydrogen jet streams after accidental releases in scenarios such as high-pressure hydrogen gas storage tanks and hydrogen transmission pipelines. These experiments utilized a release pipe with a diameter of 10 mm and a length of 0.75 m, along with three pressure sensors, to study the influence of release pressure and ignition position on jet flame overpressure and flame propagation. Extensive tests at 1.5 MPa yielded a hydrogen flammability map containing two nonflammable zones and one flammable zone, along with a graph illustrating the relationship between overpressure and ignition points. Furthermore, experiments conducted at ignition positions of 0.05, 0.5 and 1.0 m under release pressures ranging from 6 to 10 MPa revealed that release pressure had no significant effect, while ignition position notably influenced the waveform and peak of the shockwave. Additionally, a peak shockwave reaching 30 kPa was observed at the downstream of the pipe outlet when ignited at 0.05 m, far exceeding the threshold of 24 kPa associated with fatalities. This research aims to provide valuable insights for safety design and protection distance considerations in scenarios involving hydrogen release and ignition.

Quantitative risk assessments of hydrogen blending into transmission pipeline of natural gas

Recently, considerable attention has been paid to blending hydrogen with natural gas transmission pipelines. However, risk assessments using different hydrogen blend concentrations in natural gas pipelines have not been thoroughly investigated. Thus, the main objective of this study is to carry out a quantitative risk assessment of hydrogen blending into the transmission of natural gas. For this, six different concentrations of hydrogen blending, three pipes and four different release holes are used in this study. The effect distance decreased with increasing hydrogen concentration for the jet fire case. For case of vapor cloud explosions, the downwind distance of the maximum explosion overpressure increased with increasing hydrogen concentration. It was also found that as the hydrogen concentration increased, the individual risk was sensitive to adjacent to the pipelines, however, it was less for far-fields. This study is expected to contribute to the safety measures for business sites with hydrogen blending into natural gas pipelines.

Experimental Study of the Effect of CO/H2 Ratio and Release Pressure on Syngas Jet Flame Propagation and Overpressure.

Syngas, composed of hydrogen and carbon monoxide, serves as an alternative fuel for hydrogen energy and a key raw material for chemical synthesis. However, due to its flammable nature, syngas poses risks of forming explosive mixtures in the event of a leak. This study explores potential accident scenarios in coal chemical environments involving syngas reaction vessels. Experimental investigations focus on the overpressure and propagation dynamics of jet flames resulting from syngas leakage, with CO volume fractions ranging from 50 to 80% and release pressures between 2 and 5 MPa. Results reveal that maximum flame overpressure occurs within a CO volume fraction range of 55-65%, with no consistent relationship observed between overpressure and CO fraction at fixed release pressures. During our experiments, the maximum recorded overpressure of 28.4 kPa was reached during vented explosions. Additionally, ignition outcomes categorize into three types based on flame propagation speed: combustion/flare, resembling normal deflagration; and high-velocity deflagration, characterized by rapid propagation and potential for steady jet fire formation. While shockwave-like features may be observed, these do not indicate true detonation. These findings offer insights for the safe handling and storage of syngas.

Experimental study on the flame trajectory evolution of horizontal jet fires under reduced pressures

Jet fire including process pipeline/tank leakage, oil exploitation industry of tail gas treatment flare or other industrial combustors as a common phenomenon can be found at high altitude areas. This work characterizes the flame trajectory evolution of horizontal jet fires under reduced pressures, which is rarely studied. The experimental results show that the horizontal flame projection distance increases monotonously, but the vertical flame length first increases and afterward decreases with the increase of heat release rate and the decrease of ambient pressure. Meanwhile, flame trajectory length increases significantly and then slowly with increasing heat release rate, but first increases to a maximum value and afterward declines with decreasing ambient pressure. Meanwhile, the turning point of vertical flame length appears earlier than that of flame trajectory length with increasing heat release rate (or jet velocity at source) and decreasing ambient pressure. Then, a mathematical model based on the flame arc hypothesis and a dimensionless model were proposed to describe the flame trajectory length, the momentum-buoyancy length scale Lm=(M0/g′)1/3 was used to normalize the flame trajectory length. The measured flame trajectory length in terms of the nozzle diameter, heat release rate, and ambient pressure was satisfactorily correlated by the proposed models.

Study on Thermal Radiation Characteristics and the Multi-Point Source Model of Hydrogen Jet Fire

Study on Thermal Radiation Characteristics and the Multi-Point Source Model of Hydrogen Jet Fire

Numerical simulation of high-pressure jet fire in on-board hydrogen storage cylinders under fire conditions

Hydrogen fuel cell vehicles (HFCVs) may cause fires in the event of an accident. When the high-pressure hydrogen storage cylinders are exposed to fire for a long time, there will be a risk of catastrophic consequences such as leakage, jet fire and explosion. Fire test is the main method to study the safety performance of hydrogen storage cylinders. During the firing process, the wall and internal temperature of the hydrogen storage cylinder rise gradually, and the thermally activated pressure relief device (TPRD) of the cylinder reaches a certain temperature and then releases high-pressure hydrogen to prevent the cylinder from bursting. As the hydrogen storage cylinder is in the fire environment, the release of high-pressure hydrogen will be ignited to form a jet fire and cause damage to personnel and equipment. In this paper, CFD software Fluent was used to numerically simulate the local fire test of the hydrogen storage cylinder with high-temperature air as the fire source. The variation law of cylinder wall temperature, gas temperature and pressure inside the cylinder, and the activation of TPRD were analyzed. At the same time, on the basis of the fire test simulation, a high-pressure hydrogen jet fire simulation numerical model caused by the TPRD action was established. The velocity field, temperature field and hydrogen concentration distribution of the jet fire were obtained, and the overpressure generated by the jet fire and the flame length size were analyzed. The results show that the high-pressure hydrogen released by TPRD was ignited under the fire condition to produce a jet flame and generated an overpressure in the jet direction, and the influence range of the overpressure was smaller than the influence range of the jet flame.

Impact of Jet Fires on Steel Structures: Application of Passive Fire Protection Materials

Jet fires are the second most common fire scenario after spill fires. This type of fire is characteristic of gas and gas–oil fires occurring on oil platforms and gas production and processing plants. The consequences of such fires are characterized by high material damage; this is associated with extensive networks of technological communications, since there is a high density of technological facilities and installations in the territory where these fires occur. At such facilities, there is a large number of steel structures, which under the action of high temperature quickly lose their strength and deform. To protect steel structures in the oil and gas industry, fire protection is used, which consists of different types: boards in the form of flat plates, plasters, and epoxy paints. This paper compares three types of fire protection materials for steel structures under jet fire: board fireproofing, plaster composition, and epoxy coating. When comparing the efficiency in jet fire, cement boards were found to be the best. However, despite the better fire protection efficiency, their low application is expected due to their massiveness and the high cost of such protection and the difficulty of installation. Nevertheless, the development of fire depends on the place of its origin, the size of the initial fire zone, and the stability and massiveness of the metal elements of the vessel structure or the structure of the boards on which the equipment can be placed. Therefore, it is necessary to take these factors into account when selecting fire protection and to apply it depending on the required fire resistance limits of structures, which should be determined depending on the fire development scenarios.

Failure analysis of a separator under various thermal loading: A numerical study

In the present study, Computational Fluid Dynamics (CFD) simulations were carried out on a separator subjected to three different fire scenarios: pool fire, jet fire and fireballs. The empirical models applicable to such plants are not developed and conventional radiation models leads to an overestimation of the heat flux and safety distances. Therefore an alternative tool like CFD along with empirical models is used to model the potential scenarios mentioned above in a model oil and gas separator plant. The developed model were validated by comparing literature data on the flame length, maximum flame temperature and its location above pan surface in case of pool fire and comparing them with literature data. It is found that in case of flame length the deviation from literature data was about 10% and less than 5% for the maximum flame temperature. For jet fire the average surface temperature was 561 K while this value is 423 K in case of pool fire and 317 K for fireballs. When it comes to the radiative flux, an average value of 29 kW/m2 is found for jet fires while this value was only 14 kW/m2 for pool fire and 23 kW/m2 for fireballs. The thermal loads on the separator vessel due to above fire scenarios were also calculated. The obtained value of thermal stresses were around 285 MPa and 600 MPa for pool and jet fires respectively. Thus it can be concluded that from safety point of view jet fires are the most critical one. The results obtained form simulations were also compared with that of data from empirical models.

Risk Analysis of Jet A-1 Tank Filling and Storage Processes at the Shorebase

Coastal Logistics Centers (CLS) provide logistics support to deep-sea drilling operations. Jet A-1 (helifuel), required for helicopters that transfer personnel to drilling ships, is filled into tanks from the tanker arriving at CLS and stored in open areas. Jet A-1 is a hazardous chemical with flammable and toxic effects and can also explode when exposed to flame. Risk analysis of this hazardous chemical is essential for CLS. This study aimed to determine the process hazards and risk analysis in the filling and storage operation of Jet A-1 from tankers to tanks. For this purpose, the Preliminary Hazard List (PHL) and Preliminary Hazard Analysis (PHA) were performed. Then, a Hazard and Operability (HAZOP) study was carried out based on these analysis results. The HAZOP study identified Jet A-1 overflow from the tank as a high-risk event. Afterward, Event Tree Analysis (ETA) was performed on the initial event of Jet A-1 spilling due to tank overflow. In ETA analysis, immediate ignition, delayed ignition, and explosion probabilities resulting from delayed ignition were calculated with the CCPS (Center for Chemical Process Safety) Module. The probability and frequency values of accident scenarios were calculated as P=0.0028, f=1.736 x10-4 year-1 for jet fire, P=0.0225, f=1.395x10-3 year-1 for vapor cloud explosion, P=0.127, f=7.874x10-3 year-1 for flash fire, P=0.847, f = 0.0525 year-1 for toxic release, respectively. It was determined that all accident scenario frequency values were above the legislation threshold value (10-4 year-1). Design solutions and preventive measures have been proposed to reduce risks. The combination of risk analysis methods is effective in risk assessment studies.

Methodology for optimally designing hydrogen refueling station barriers using RSM and ANN: Considering explosion and jet fire

Hydrogen is gaining attention as a sustainable energy source with the potential to replace fossil fuels. Due to its high diffusivity and wide flammability range, hydrogen can easily ignite with minimal electrical energy, leading to explosion and fires with minimal friction. Effective blast walls can restrict the dispersion of hydrogen, reducing the explosion overpressure due to delayed ignition. In addition, firewalls can improve safety by minimizing the impact behind the walls, thereby reducing the radiant heat caused by jet fires. This study proposes to optimize the distance between leak sources and barriers, as well as the height and width of barriers, to address explosion overpressure and radiation heat at hydrogen refueling stations (HRS). The optimization was carried out using Response Surface Methodology (RSM) and Artificial Neural Networks (ANN) and validated by simulations. This study confirms the feasibility of the barrier design at HRS and contributes to the improvement of safety.

Thermal runaway and combustion of lithium-ion batteries in engine room fires on oil/electric-powered ships

The thermal characteristics of traditional fuel fires can be altered by the thermal instability of lithium-ion batteries (LIBs) in–oil-electric hybrid ships. The thermal runaway (TR) and combustion of 18,650 LiFePO4 LIBs with 0 %, 50 %, and 100 % states of charge (SOC) in pool fires were studied with different annular n-heptane pools. The goal is to simulate the thermal safety of LIBs in hybrid ships within the thermal environment of pool fires. The flame morphologies resulting from the combustion of the battery and pool fires, temperatures of the battery surface and flame, exhaust characteristics of the battery, heat radiated from the pool fire to the battery, and mass losses were analyzed. The results showed that the risks of thermal runaway and combustion with LIBs were significantly higher in a thermal fire environment. Lithium batteries produce jet fires that increase the width and height of the flame during pool fires. Moreover, the battery with a 0 % SOC doesn’t experience thermal runaway during the fire, but thermal runaway of the battery with a 100 % SOC is more severe than that of the battery with a 50 % SOC, and the maximum rates for their temperature increases are 12.98 °C/s and 7.12 °C/s, respectively. In addition, the energy balance method showed that the pressure relief by the battery safety valve during a fire was not dependent on the SOC. An equivalent network diagram was constructed for the radiative heat transfer between the lithium battery and the pool fire. It is proposed that the total heats required to induce thermal runaway of batteries with the same SOCs are almost the same in different thermal environments, but the energy required for the 50 % SOC battery is greater than that required for the 100 % SOC battery, 10,161 ± 59 J and 9724 ± 43 J, respectively. Moreover, the combustion rates were proportional to the height of the flame during the mixed combustion of a lithium battery jet fire and pool fire. A dimensionless model was developed for the relationship between flame height and mixed combustion rate.

Burning behavior of hydrogen jet flame inhibited by a wire mesh screen

Hydrogen is recognized as a promising energy source and the potential risks associated with leakage and jet fire accidents should be considered. The objective of this study is to explore the feasibility of utilizing wire mesh to suppress hydrogen jet flames. The experiments of hydrogen jet fire with ignitors below and above the wire mesh were performed to explore the effect of wire mesh on the burning behaviors at different mesh numbers, mesh-to-nozzle distances, and fuel flow rates. Compared to the free jet flame, the length of jet flame under the action of wire mesh is decreased by 50–90 %. The flame with topside ignition fails to pass through the mire mesh due to the cooling effect of the fuel jet. Experimental results reveal that the state of the flow field in the impingement area plays an important role in determining the upper flame height. Both the upper flame height and the flame extension length beneath the screen decrease with mesh-to-nozzle distance. As the mesh porosity decreases, the flame extension length increases, however, the upper flame height decreases. Based on the classical theory of flow resistance through porous media, a new dimensionless model was developed to predict the characteristic flame lengths of the jet flame inhibited by wire mesh. The findings presented in this paper offer fresh insight into the safeguarding of jet fires.

Characterization of the hypergolic ignition of green fuels with hydrogen peroxide by drop test and jet impingement

This work presents an experimental study on the hypergolic behavior of variants of N,N,N’,N’-tetramethylethylenediamine (TMEDA)/N,N-dimethylethanolamine (DMEA) system, named PAHyp 0, with 93 wt% hydrogen peroxide. Two different copper-based catalyst and one cobalt-based catalytic agent were dissolved in the fuels to trigger the pre-ignition reactions. When employing copper chloride dihydrate, the resultant fuel requires methanol (ternary system) as a stabilizing agent, whereas both carboxylic salts of copper and cobalt dissolved in TMEDA/DMEA deliver a stable formulation (binary system) without the need for any organic solvent. Shadowgraph high-speed imaging was used to capture the ignition process and pressure wave development of over 30 fuel samples in a modified drop test. An ignition/stability envelope was proposed to map the safe and unstable formulations. It was demonstrated that the concentration of TMEDA should be no more than 50% in the binary system, while the amount of methanol should fall within a concentration window of 33 to 50% in the ternary system. Lower loadings of catalyst, ranging from 0.5 to 1.0 wt%, are required to deliver stable fast-igniting fuels. Three promising formulations catalyzed with 1 wt% copper salts were selected to perform impinging jet fire experiments. Impinging jets yielded significantly lower ignition delay times than drop tests due to the better mixing conditions. However, it was verified that ignition may fail for low values of jet velocities, below 0.8 m/s, and for high jet velocities, exceeding 14 m/s. An attempt to explain the ignition and non-ignition events was made by using the fundamentals of explosion limits of the hydrogen/oxygen system and oxidation reactions at low temperature. Remarkably, ultra-fast ignitions of about 10 ms were measured by the impinging jet setup within near-optimal operational conditions. Therefore, TMEDA/DMEA-based fuels with reduced catalyst loadings (0.5–1.0 wt%) offer new opportunities in aerospace propulsion and should be further studied.

Influence of different causes on thermal runaway characteristic of LiFePO4 battery

To solve the current battery safety issues and accident investigation problems. Thermal runaway experiments triggered by nail penetration, hot box, flame heating and heating plate were carried out on a commercial 8 Ah pouch LiFePO4 battery. Recorded real-time phenomena, voltage and temperature. Then we discussed the TR process in the light of the latest mechanism study. The local TR is triggered by nail penetration within 3 s. The hot area above 700 °C and the spreading of internal TR was detected. LiFePO4 battery thermal runaway will generally emit white smoke, no fire. And it requires more attention to explosion risk. If the combustible gas is ignited, jet fire will appear, but the injection pressure is not extreme. Thermal runaway triggered by local heating is inconsistent with a voltage drop. A mapping method of thermal runaway parameters radar map is designed, which can indicate the danger degree of TR with shapes. Through comparison, some characteristics are obtained for the judgment of battery accident causes. This research can provide a basis for LFP battery safety evaluate and accident investigation.

Воздействие криогенных сред и струйного горения на эпоксидные интумесцентные композиции, предназначенные для защиты оборудования и строительных конструкций нефтегазового комплекса

The article discusses the studies of epoxy intumescent fire-protective coating of steel structures impacted by cryogenic media and jet fire, in accordance with the requirements of the methodology developed at the Orenburg branch of the Federal State Autonomous Educational Institution of Higher Education VNIIPO EMERCOM of Russia, and harmonized with the international standards ISO 22899-1:2021, ISO 20088-1:2016, and ISO 20088-3. The tests have been conducted with the epoxy fire- and cryogenic-protective intumescent composition «Plamkor-5» (produced by JSC Scientific and Production Holding «VMP», Yekaterinburg, Russia). According to the results of the test for resistance of a square-shaped sample with internal dimensions 1500×1500×500 mm and a central shelf made of 10 mm thick carbon steel coated with the fire-retardant composition «Plamkor-5» to cryogenic fluid spill, it has been established that the sample does not reach the critical temperature of minus 49 °C with an actual 22.37 mm dry layer thickness. The average sample temperature at the 60th minute of the test was minus 32.09 °C. The results of the test of a similar sample in order to determine the resistance of the fire-protective composition «Plamkor-5» to a jet fire with an actual 10,89 mm thickness of the protective dry layer have shown that the sample does not reach the critical temperature of 500 °С during 60-minute fire exposure, whereas the average temperature of the sample was only 37 % (184.84 ºС) of the temperature limit value. According to the results of the test for resistance of a steel column shape sample of I-section 25K2 coated with the fire-retardant composition «Plamkor-5» to spill under the pressure of the cryogenic liquid, it has been established that the sample does not reach the critical temperature of minus –49 °С with an actual 23.78 mm dry layer thickness, whereas the average temperature of the sample at the 60th minute of test was minus 48.38 °С. The obtained results are comparable with the effect of the best import analogs; therefore, «Plamkor-5»-based fire-protective coatings can be used for the design and development of fire protection of building structures, at the facilities of the oil and gas industry, in tunnel structures, and civil engineering.