In this work, the evaporation, heat transfer, and ignition characteristics of RP-3 aviation kerosene leakage on curved hot surfaces were investigated. It was found that the spread and evaporation rates gradually increased during the injection stage, peaked after the end of injection, and then decreased. The variation of the heat transfer coefficient between the hot surface and the fuel during evaporation was further investigated. The results indicate that the heat transfer coefficient attains its maximum value at the initial stage of injection, then gradually decreases, and stabilizes after the injection ends. The range of stable values is from 150 to 200 W/(m²·K). A dimensionless relationship was established between the stable heat transfer coefficient and the hot surface temperature. Numerical simulations provide insights into the diffusion behavior of fuel vapor above the curved hot surface. The results indicate that during the diffusion process, the fuel vapor temperature and concentration fields exhibit a high degree of spatial correlation, and the vapor diffusion velocity increases with vertical height. At the ignition core region, vapor temperature and concentration data were extracted and analyzed, revealing a critical range for airborne ignition: vapor temperatures between 349 K and 469 K, and concentration from 0.750% to 6.382%.

Aircraft operations are faced with fire accident caused by the ignition of leaked flammable liquids on hot surfaces. This type of accident could cause catastrophic consequences. To predict and identify the potential risk of flammable liquid ignition, a quantitative assessment model based on system dynamics is proposed in this work. Firstly, the ignition-related parameters in the flammable liquid leakage and hot surface ignition scenario are identified by leakage characteristics and ignition characteristics. Secondly, the causal relationship between flammable liquid leakage and hot surface ignition scenarios is constructed based on mathematical relationship for leakage volume, hot surface temperature and ignition probability. Among them, the key coefficients of the mathematical relationships are determined by hot surface experiments. Finally, a causal diagram is constructed using system dynamics to calculate the ignition probability and analyze the fire risk. A case study is used to illustrate the developed model and a discussion based on the case study is presented to identify the key influencing parameters of ignition probability. The proposed model can provide a new idea for the assessment of the ignition probability of flammable liquid leakage on hot surface, as well as a new perspective for the aviation safety.

If liquid fuel leaks onto a metal surface (such as the ship’s deck), it may lead to the burning behavior of an unbounded fuel layer. This work carried out the burning experiment of an unbounded fuel layer on a steel substrate. The evolutions of flame height, burning diameter, fuel mass and fuel thickness etc., are revealed. The unbounded fuel layer on the steel substrate ranges from 0.18 mm to 0.76 mm. There is a positive correlation between the fuel thickness and the burning diameter. The difference of leakage rate or burning diameter does not have a significant impact on the burning rate during the quasi-steady burning stage, and the average burning rate is about 14.0 g/(m2s). The classical formula for pool fires cannot accurately calculate the burning rate of unbounded oil. In addition, if the classical formulas for the burning rate and flame height of pool fires are used to predict the flame height of a burning unbounded oil layer, the accuracy is rather poor; if the fuel burning rate directly obtained from the experiment and the classical formulas of flame height for pool fires are used, the accuracy of the predicted flame height is high.

In the aircraft engine, auxiliary power unit and other areas, hot surfaces are generated due to fuel combustion, power transmission and other reasons. Meanwhile, these areas may have the potential for oil leakage. When the leaked oil contacts these hot surfaces, it may be ignited to form a fire, threatening the aircraft's safety. In this paper, evaporation and ignition experiments of oil leakage on a flat hot surface were carried out, and the vapor plume movement and flame propagation characteristics were investigated. Furthermore, the relationship between the hot surface temperature and the ignition core height and ignition delay time was studied. By the PIV technique, the velocity distribution of the vapor plume was studied. The flame transient development process and the flame propagation speed were quantitatively analyzed. The results show that the vapor plume velocity increased rapidly with height, then remained relatively stable, and eventually decreased gradually. Overall, the plume velocity shows a "cap-shaped" horizontal distribution. After ignition, the flame first expands in a spherical shape and then propagates in the vertical direction. The vertical upward propagated flame velocity is greater than the downward, and the corresponding velocities are 100.6 similar to 496.42 cm/s and 66.71 similar to 192.51 cm/s, respectively.

Burning oil layer affected by the built-in obstacle is common, e.g., leaked fuel around tanks in chemical parks. This work conducted experiments of the burning oil with different heights (Ho) and diameters (Do) obstacle. Results showed that as Ho increases, the burning rate in this work is greater than the pool fire without the built-in obstacle. Radiation, convection and conduction heat processes among the flame, built-in obstacle and fuel are quantified. Total radiation heat received by the liquid fuel is almost unchanged with Ho but varies with Do. Radiation heat from the obstacle to the fuel rises with Ho, but first rises then falls with Do, contributing up to ∼0.32 to total radiation heat (flame: ∼0.68). Conduction heat from the obstacle to the fuel (Qcond,o−l) depends mainly on Do. When Do≥ 10 cm, the proportion of Qcond,o−l almost all exceeds half. In contrast, the proportion of conduction heat from the pool to the fuel decreases with increasing Do. The dominant heat feedback mechanism of a burning oil affected by built-in obstacles is revealed. Physically, total heat feedback received by the liquid fuel is from the flame and the built-in obstacle. Their contributions are highly sensitive to Do but not Ho. Total heat feedback is from conduction, convection and radiation. If Do is small, the dominant heat feedback is radiation. But as Do increases, the conduction heat from the obstacle to the liquid fuel increases significantly, increasing its contribution and even becoming the dominant heat feedback, which is different from the pool fire.

Hydrothermally synthesized alpha-MnO2 precursor with different K+ contents were calcined and evaluated for soot oxidation under tight-contact conditions. Characterization methods including XRD, ICP, XPS, and Raman were performed. Redox properties were probed by H-2-TPR and Soot-TPR. The calcined samples exhibit the phases of Mn2O3 and/or alpha-MnO2. DFT calculations modeled K+ occupancy, vacancy formation, and O-2/NO adsorption. 0.4KMnO achieves T-90 of soot removal at 346 degrees C with 96% CO2 selectivity in O-2 atmosphere; the activity trend is 0.4KMnO > 0.6KMnO approximate to 0.2KMnO > 0KMnO. XRD/ICP/XPS verify K+ embedding in the tunnel structure. Raman results indicate MnO6-K-MnO6 linkages weaken Mn-O bonds and activate lattice oxygen, generating surface vacancies and richer surface reactive oxygen species. The results from H-2-TPR and Soot-TPR also suggest the similar trend. DFT results show tunnel K+ promotes vacancy formation and stronger O-2/NO adsorption. K+ occupancy in alpha-MnO2 tunnels tunes the Mn-O lattice and surface redox chemistry, enabling soot oxidation at lower temperatures.

Sustainable aviation fuels are increasingly employed in modern aviation systems to meet both performance demands and global carbon reduction goals. However, fuel leakage and accidental contact with hot surfaces remain serious safety hazards in aviation thermal energy systems. A comprehensive understanding of both conventional and sustainable aviation fuel behavior is essential for improving thermal safety and guiding fuel selection. Therefore, this study investigates the comparative pyrolysis characteristics and hot surface ignition behavior of conventional aviation fluids (RP-3 aviation kerosene and phosphate ester hydraulic fluid) and sustainable aviation fuel, using a combination of hot surface ignition testing and thermogravimetric-Fourier transform infrared (TG-FTIR) analysis. Results show that RP-3 kerosene and sustainable aviation fuel exhibit similar ignition behavior, characterized by near-complete combustion and the release of hydrocarbon-rich volatiles. Corresponding to the test results of hot surface ignition, the ignition probabilities of two fuels are close under the same conditions. In contrast, the hydraulic fluid demonstrates inhibited ignition, and the ignition probability curve shifts towards higher temperatures. It is attributed to the generation of PO radicals that suppress reactive chain propagation, alongside residue formation. Kinetic modeling indicates that RP-3 kerosene and sustainable aviation fuel follow nth-order reaction mechanisms, while the hydraulic fluid aligns with a three-dimensional contraction model. Moreover, average activation energies calculated for the three fuels (ERP-3 < E-SAF < E-Hyjet) were found to correspond to the order of their respective minimum hot-surface ignition temperatures (TRP-3 < T-SAF < T-Hyjet). This provides a potential predictive metric for assessing ignition risk in fuel-integrated systems. These findings contribute to offering insights for fuel selection, system design, and fire risk mitigation in the aviation system.

Fuel leakage during storage and transportation processes poses challenges to the fire safety of industrial systems. Especially when fuel continuously leaks from a vertical surface, the increased flow velocity caused by gravity leads to stronger convection. This paper presents an experimental investigation of the fire behavior of spill fires on a vertical plate. Two fuels (methanol and n-heptane) were used at different leakage rates. The experimental results indicate that methanol forms a stable fuel film structure in an arc shape in the quasi-stable state, while the liquid film structure of n-heptane is disrupted and breaks from the flame front to form many split flames. This phenomenon can be attributed to the reverse heating effect caused by the plate temperature exceeding the fuel temperature. A refined Sherwood number (Sh) is proposed to estimate the fuel burning rate from the perspective of evaporative mass transfer. Additionally, the heat transfer analysis during the quasi-stable stage indicates that the burning process is mainly dominated by the flame convection. Specifically, convection heat accounts for 98% of the total heat transfer in methanol and 95% in n-heptane. Furthermore, approximately 1.5% of the additional convective heat transfer in n-heptane is derived from the plate.

The aggregation tendency of micro-proppants in fracturing fluids poses a major challenge for their field application. In this work, the physicochemical properties of three quartz micro-proppants (MP1, MP2, MP3) and the effects of surfactants on their wettability and dispersibility were systematically investigated by experiments combined with molecular dynamics (MD) simulations. Increasing surface roughness and carbon content was found to significantly increase the water contact angle and reduce hydrophilicity, with contact angles of 131.6 degrees, 94.2 degrees and 32.6 degrees for MP1, MP2 and MP3, respectively. The influence of particle size on wettability was closely coupled with intrinsic surface character: size reduction slightly enhanced the hydrophilicity of MP3 but markedly intensified the hydrophobicity and aggregation tendency of MP1 and MP2. The properties of the wetting liquid also played a critical role. The addition of surfactants effectively improved wettability and dispersion stability, among which the nonionic surfactant AEO-9 showed the best performance, reducing the contact angle of MP1 from 131.6 degrees to 47.5 degrees and providing higher stability than SDS and CTAB. MD simulations show that analysis of adsorption conformations and interaction energies confirms that AEO-9 forms the most stable adsorption layer on the particle surface, while MSD results further demonstrate that it effectively promotes hydration-film for-mation, thereby enhancing the wettability and dispersion stability of the system. These results provide molecular-level insight into how surface properties and wetting-liquid characteristics jointly control micro-proppant behavior and offer practical guidance for surfactant selection in enhanced oil and gas recovery.

Amid rising global energy demand and ongoing green transition, the safe operation of energy systems is critically important. However, liquid fuel in energy systems faces the challenge of fire hazards. This study focused on initial stage of fuel leakage fire, and investigated flame spread over flowing fuel surface under different substrate slopes (θ) and fuel discharge flow rates (Q). Results show that: (1) For tail flame, two distinct types of spread behaviors were identified. The tail flame front could remain at the ignition position or move downstream with flowing fuel. Transition between these two modes was governed by the balance among total heat input, heat loss, and total heat of gasification. Increased bottom-plate heat dissipation and forced convection loss promoted the movement of tail flame front. Furthermore, considering the coupled effects of fuel thickness and flow velocity, a correlation describing the critical state of no relative motion between tail flame front and fuel was established. (2) For pioneering flame, the flame spread rate (Vf) increased with Q under all θ, with relative increases of 58%, 71% and 86% for θ = 0°, 0.1° and 0.2° cases, respectively. However, depending on Q, Vf exhibited three types of trends, i.e., it decreased, remained constant, or increased with θ. Moreover, a flame spread rate correlation was proposed based on momentum balance, which provides acceptable predictions. Finally, influences of fuel type and boundary conditions were discussed. These findings are expected to improve understanding and provide references for prediction and emergency response of such fires.

The formulation of Shenhua coal-water slurry (SCWS) is constrained by the need to simultaneously improve flowability and storage stability through interfacial regulation. Because slurry performance is governed by coal surface chemistry, dispersant adsorption, interfacial water mobility, and particle interactions, clarifying how polymer architecture couples these factors is essential for rational dispersant design. In this work, three polymer-grafted graphene oxide (GO) dispersants, PGO_APEG, PGO_ST, and PGO_AA, were prepared by grafting polymer chains with different interfacial characteristics onto GO sheets and applied to SCWS. Among them, PGO_APEG produced the most favorable interfacial response, decreasing the contact angles of Shenhua coal to 58.40° for water, 47.25° for glycerol, and 11.25° for diiodomethane, while shifting the zeta potential to -28.43 mV. Its adsorption behavior followed the Langmuir isotherm and pseudo-second-order kinetic model, indicating monolayer-like adsorption dominated by interfacial interactions. SCWS prepared with PGO_APEG showed the lowest apparent viscosity of 344.85 mPa·s at 100 s⁻¹ and a final Turbiscan stability index of approximately 0.1. Molecular dynamics simulations suggested that PGO_APEG formed a moderately confined but still mobile interfacial water layer, which helped balance interfacial cohesion and water mobility around coal particles. Extended DLVO analysis further indicated that electrostatic repulsion, steric stabilization, and hydration-related interfacial effects contributed to a positive particle interaction energy barrier. These results demonstrate that grafted polymer architecture can coordinate coal surface regulation, adsorption behavior, interfacial water mobility, and particle interactions, providing a mechanism-guided strategy for designing GO-based dispersants for stable and flowable SCWS fuels.

Fuel leakage fires are a common type of hazard in petrochemical storage and transportation, and their combustion behavior is significantly influenced by the ground surface material. However, the influence mechanism of substrate thermal properties remains incompletely understood. This work presents an experimental study on the combustion behavior of thin-layer fuels with continuous leakage of methanol and heptane on concrete and steel substrates. The results indicate that methanol, due to its low boiling point, is less affected by the substrate. In contrast, the combustion behavior of heptane responds significantly to the thermal properties of the substrate. The burning area of heptane on concrete is significantly reduced due to the film boiling effect, while on steel, its burning rate is lower due to greater heat loss. Further analysis reveals that during the quasi-steady burning stage, the mass loss rate per unit area for the same fuel does not vary with the leakage rate. However, it exhibits significant differences between substrates. Heat feedback calculations based on the energy conservation law indicate that the fundamental reason for this difference lies in the poor thermal conductivity of the concrete substrate, which results in a much lower heat loss fraction (38% – 48%) compared to that of the steel substrate (> 60%). Combined with the reverse heat transfer from the high-temperature surface to the fuel layer, this leads to a higher burning rate and flame height on concrete. Furthermore, thin-layer fuel combustion exhibits a mechanism co-dominated by convective and radiative heat feedback, which is distinct from the single radiation-dominated mechanism of pool fires. This study incorporates the thermal effect of the substrate into the theory of thin-layer fuel combustion, which contributes to improving the prediction accuracy of spreading fires. Novelty and significance statement This study provides the first systematic comparison of continuous leakage fires of methanol and heptane on thermally distinct substrates (steel vs. concrete), revealing how substrate properties influence heat feedback mechanisms in thin-layer combustion. Unlike pool fires, where radiation typically dominates, we demonstrate a co-dominant mechanism of convective and radiative feedback in thin-layer combustion. This finding revises the traditional view that solely relies on fire size to determine the dominant mechanism. The identified reverse heat transfer phenomenon on concrete substrates, along with the quantified heat loss fractions, provides insight into the heat feedback partitioning mechanism in thin-layer fuel combustion. This study provides critical experimental data and mechanistic understanding of this combustion, revealing the essential influence of substrate thermal properties on combustion behavior. This provides a scientific foundation for refining theoretical models of fires and improving fire risk assessment on different substrates.

The burning rate of spill fires differs significantly from that of pool fires. Experimental results demonstrate that spill fires not only exhibit a lower burning rate per unit area (BRPUA) than equally scaled pool fires, but also maintain a constant BRPUA across diameters. However, a systematic explanation for the diameter-independent BRPUA has yet to be developed, and there is still a lack of predictive models. To address these problems, this work modified key parameters in the stagnant layer theory model based on heat transfer analysis of spill fires. This model encapsulates the fuel and substrate effects through the B-number, while capturing the experimental conditions and boiling effects through the hc/cp (where hc is the convective heat transfer coefficient, and cp is the specific heat capacity). A modified B‑number (Bm) was proposed for spill fires. Based on a variant of the stagnant layer theory, the value of hc/cp was determined. The results show that hc/cp should lie within 9–10 g/m²s under spill fire conditions. It was also found that when boiling occurs, hc/cp decreases with increasing boiling intensity. The combination of Bm and hc/cp is applicable for predicting the burning rate of spill fires involving fuels with different sooting tendencies. Furthermore, the variation of each heat transfer component with diameter was analyzed. Specifically, with increasing diameter, the decreasing convective heat feedback for n-heptane was explained through a variant of the stagnant layer theory, in which the blowing effect coefficients for both fuels were calculated. Finally, from a heat transfer perspective, the diameter‑independent BRPUA observed in spill fires is elucidated. Novelty and significance statement The diameter-independent burning rate per unit area (BRPUA) of spill fires has received limited attention, and existing burning rate correlations do not reflect this characteristic. This work elucidates the underlying mechanism through heat transfer analysis. A new predictive model for spill fire burning rates is proposed based on the stagnant layer theory. Validated against two typical fuels and a steel substrate, this model is shown to quantify the burning rate effectively. This approach also shows potential for extension to other fuels and substrates. Given the difficulty of determining the convective heat transfer coefficient (hc), the method based on a variant of the stagnant layer theory offers a novel solution for evaluating hc under complex heat transfer conditions. By successfully capturing the influence of boiling on hc, this work highlights the importance of incorporating boiling effects into the analysis of hc under spill fire conditions.

The liquid fuel leaked from the chemical industry park may be limited by both the internal and the external boundaries, which may induce large-scale and catastrophic fire accidents. Pool fire experiments of different central oil tank sizes were carried out under the joint limitation of internal and external boundaries. The results show that when the size of the central oil tank is large, the flame morphology is split and cannot be completely converge above the central oil tank. For methanol, the main control mechanism of heat feedback is convection. For n-heptane, the main control mechanism of heat feedback is radiation, and the high central oil tank obviously reduce the total radiant heat flux received by the fuel surface. In addition, the central oil tank has a certain effect on burning rate. Especially for n-heptane, when the central oil tank height increases from 5 cm to 20 cm, the burning rate decreases obviously and there is a peak of burning rate with the further increase of the central oil tank height. At last, through dimensional analysis, a predictive correlation was established, which can well predict the burning rate of pool fire under different central oil tank sizes.

Ignition delay time (IDT) is a critical parameter for characterizing the auto-ignition behavior and combustion stability of NH3/H-2 blended fuels. However, obtaining reliable IDT data remains challenging because experimental measurements are costly and confined to limited operating conditions, while kinetic simulations are highly sensitive to the fidelity of reaction mechanisms. In this study, IDT data for NH3/H-2 mixtures are systematically compiled from multiple literature sources, encompassing diverse experimental facilities and broad ranges of temperature, pressure, and equivalence ratio. Based on this dataset, a small-sample, data-driven framework for IDT prediction is developed. First, a multivariate linear regression model based on a modified Arrhenius formulation is employed to elucidate the influence of key parameters, revealing the hydrogen blending ratio as a dominant factor governing IDT. Accordingly, separate regressions at fixed hydrogen fractions are performed to achieve an optimal balance between predictive accuracy and physical interpretability. Second, a few-shot learning model, TabPFN, is introduced to directly predict IDT across wide operating conditions, demonstrating consistently high accuracy despite the limited data regime. Specifically, TabPFN model shows excellent performance across a broader range of combustion condition, with prediction accuracy of R-2 > 0.97 on both the reflected shock tube (ST) dataset and the rapid compression machine (RCM) dataset. Herein, the proposed framework enables the rapid construction of reliable IDT surrogate models for hydrogen blending-ratio screening and fuel composition optimization, and provides quantitative guidance for experimental design under data-sparse conditions.

In this work, ethylene glycol (EG), formamide, and 1, 2-propanediol were identified as potential extractants for separating cyclohexane + isopropanol (IPA) azeotropic system. The sigma-profile was analyzed using the Dmol3 module of Materials Studio, and the interaction energy between the components was calculated, indicating that EG is the most promising extractant. The liquid-liquid equilibrium (LLE) data for the cyclohexane + IPA + extractants system were measured at 303.15 K, 313.15 K and 323.15 K. When the temperature increases, the extraction capacities of EG and formamide decrease. Meanwhile, the temperature has less impact on the capacity of 1, 2-propanediol. EG has higher value of the distribution coefficient (D) and separation factor (S), indicating its superior effectiveness for separation. Othmer-Tobias and Hand equations were used to estimate the reliability and consistency of the LLE data. The nonrandom two-liquid (NRTL) and universal quasi-chemical (UNIQUAC) thermodynamic model in Aspen Plus 11 software were used to regress the LLE data, and the binary interaction parameters were calculated. The root mean square deviation (RMSD) values were all less than 0.02, indicating that the NRTL and UNIQUAC models can correlate experimental data well. Finally, the regressed binary interaction parameters were further validated using GUI-MATLAB software, confirming the reliability of the data regression.

RP-3 is one of the most widely used aviation fuels in China. The accidental leakage and ignition of RP-3 may pose a serious threat to the aircraft safety. This work focuses on the ignition process of RP-3 liquid flow on a curved hot surface, and investigates characteristics of evaporation and heat transfer. Results showed the flame development after the ignition. There is a small blue flame in the early stage of ignition. Then the blue flame spreads outward from the ignition area to form the yellow flame. A prediction formula for the ignition probability of RP-3 is established. The total lifetime of RP-3 on the curved hot surface is found to decrease as the surface temperature increases. The fuel mass and the fuel evaporation rate on the hot surface are studied. The fuel evaporation rate firstly gradually increases, then reaches a peak value, and finally decreases with the burning time. Based on energy conservation, the heat from the flame to fuel and the heat from the hot surface to fuel are compared in RP-3 injection period and non-injection period. The heat proportion from flame to fuel is found to reach 44.2 % when the curved surface temperature is 660 degrees C in the injection period. However, this proportion is only within 10% in the non-injection period.

During aircraft operation, leakage of liquid fuel onto hot surfaces can lead to severe safety incidents. High-temperature components of aircraft (e.g., engine casings, tail nozzles, and fuel pipeline assemblies) vary significantly in size and shape, which may markedly influence the evaporation and ignition behaviors of leaking fuel. Therefore, this study experimentally investigated the evaporation and ignition characteristics of RP-3 fuel leaked onto hot surfaces of varying sizes (diameter = 4, 8, 12 cm). The experimental results indicated notable differences in evaporation and ignition characteristics across the tested surface sizes. As the hot surface size increased, the minimum hot surface ignition temperature and the ignition temperature threshold range decreased. The ignition delay time monotonically decreased with increasing hot surface temperature (TS) and surface size. By comparing the average evaporation rates for different surface sizes, it was found that within the temperature range of TS = 600-620 degrees C, the average evaporation rate increased with larger surface sizes. Energy conservation analysis demonstrated a positive correlation between the heat absorption rate of fuel and TS. Additionally, before ignition, the relative contributions of heat transfer from the upper surface (Qtop/Qtotal) and the sidewall (Qside/Qtotal) of the fuel container were quantitatively analyzed. The results revealed that the proportion of Qside increased as the hot surface size decreased. This corresponds to higher heat transfer rates. Furthermore, a dimensionless correlation describing the average evaporation rate was developed. It incorporates the effects of varying hot surface sizes and temperatures, with predictions agreeing with the experimental data.