Initial Ignition Research Articles

Effects of space size and fire location on heat transfer in flame spread over electrical wire in a small tunnel

Understanding the flame spread characteristics in tunnel is crucial for developing effective fire prevention strategies.This paper investigated the influence of two key parameters Ht and Dc on the flame spread characteristics of electrical wire in tunnel. The results indicate that the flame shape increases with Dc and Ht. Specifically, when Dc = 12 cm, a symmetrical cone-shaped flame plume forms; when Dc = 1 cm, an asymmetrical flame plume is observed. In the initial ignition stage, the droplet flame merges with the electrical wire flame, resulting in an increase in flame combustion intensity. In the process of stable spread, intermittent dripping leads to an increase in flame height. A dimensionless flame height in a small tunnel is established with Ht and Dc. When Ht is small, due to the lack of air supply, the flame height will decrease nearly at the central place. When Dc = 1 cm, the influence of Ht on the FSR(flame spread rate) can be essentially disregarded. When Dc is 6 cm or 12 cm, the change of Ht will influence the FSR. As Dc decreases, the peak temperature also decreases. Finally, a heat transfer model is built for the preheating zone, which can well predict the flame spread rate.

Enhancing safety in hydrogen storage: Understanding the dynamic process in hydrogen-methane mixtures during the pressurized leakage

Using natural gas pipelines for hydrogen-doped transportation represents a cost-effective solution for large-scale and long-distance hydrogen transport. However, concerns have been raised regarding the potential for leakage under high-pressure conditions, which could result in the spontaneous combustion of the leaking hydrogen. It is, therefore, imperative to understand the gas dynamics involved in methane-hydrogen mixtures during high-pressure leaks to ensure the safety of hydrogen storage. In the present work, the release process and the spontaneous ignition of hydrogen/methane mixtures with a hydrogen blending ratio from 0.1 to 1.0 from pressurized storage containers (20 MPa) have been numerically studied upon validated models. The findings indicate that spontaneous ignition occurs in the mixtures with any hydrogen blending ratios under the releasing pressure of 20 MPa, but the methane component is not involved in the initial combustion if the hydrogen blending ratio is less than 0.5. As the hydrogen blending ratio increases, more combustible components are involved in the initial ignition, and the location of the initial ignition turns closer to the leakage port. Meanwhile, as the hydrogen blending ratio rises from 0.1 to 1.0, the shockwave propagation is accelerated with the moment the shockwave first reflects is advanced from 58 to 60 μs to 22–24 μs, and the maximum temperature in the early leakage will exceed 3000 K. Furthermore, a higher hydrogen blending ratio leads to a more rapid pressure rise in the external space (reaching peak pressure at 191 μs for pure hydrogen) and forming a Mach disk structure with higher Mach numbers (around 7). These findings provide critical insights for understanding the combustion behavior of hydrogen/methane mixtures in high-pressure pipelines and offer valuable guidance for developing safety protocols and infrastructure designs.

Laser ignition on single droplet characteristics of aviation kerosene at different pressures and initial diameters: ignition, combustion and micro-explosion

In this study, an experimental system for single-droplet ignition by laser under different pressures is established, and the laser ignition is used to examine how pressure and initial diameter influence ignition properties of RP-3 aviation kerosene single-droplet. The findings reveal that depending on the extent of the impact of bubble rupture on the droplet's shape, The droplet's morphological alterations can be classified into three types: micro-expansion, puffing, and micro-explosion. The ignition and combustion of droplets is segmented into four distinct phases: heating, ignition, intense combustion, boiling combustion. The flame width diminishes with rising pressure. Single droplet ignition delay time is strongly influenced by the pressure, which is reduced by 92.7 %, 94.1 % and 94.3 % for the three droplets from small to large diameters with the pressure increases from 1 bar to 4 bar. The change trends of droplet diameters are first increasing and then decreasing. The whole burning rate of RP-3 droplets goes up with the rise of pressure. A droplet laser ignition model is proposed, the minimum ignition energy of RP-3 droplets with an initial diameter of 1.42 mm at pressures of 1–4 bar are obtained to be 0.88 J, 0.80 J, 0.68 J, and 0.59 J, respectively.

Effects of buoyancy on the spherical flame and explosion pressure of a CH4 mixture under dilution conditions

To determine the effects of buoyancy on the spherical flame and explosion pressure under dilution conditions, a series of explosion experiments were conducted in a 20-L spherical container. The schlieren technique was used to record CH4 flames to assess the buoyancy effect. The change in the explosion pressure was recorded and correlated with the flame shape to analyze the explosion characteristics. The methane explosion occurred in two stages: initial ignition and flame development. During initial ignition, the addition of CO2 caused the flame buoyancy to increase considerably. Flames with different buoyancies had different shapes, such as spherical, ellipsoidal, and “ω” shapes. The radius of the flame at 12 mm may serve as the threshold for the onset of buoyancy effects; once the radius exceeds this value, the flame could deform due to buoyancy effects. Increasing the added CO2 concentration caused the buoyancy effect to be enhanced and appear at a very low radius of the flame. The combined effects of buoyancy and dilution reduced the flame expansion speed. The difference between the horizontal and upward expansion speeds linearly increased with the CO2 concentration. At a high CO2 concentration, the flame stagnated at speeds below 0.5 m/s. During flame development, CO2 addition made the flame surface smoother. Suppressing the cellular flame structure delayed the maximum explosion pressure rise rate and reduced the pressure peak. A coupled analysis of the flame shape and the maximum explosion pressure rise rate showed a dense cellular structure for a high explosion pressure rise rate and a smooth flame surface for a low maximum explosion pressure rise rate. The size and number of cellular structures for different mixtures were similar at a fixed maximum explosion pressure rise rate.

Experimental study on the inertization of wood-based biomass with solid inerts

Wood pellets are one of the primary solid substitutes for fossil fuels worldwide. They present both advantages and disadvantages that have been widely studied, where one of the main disadvantages is the risk of self-heating, which may lead to smouldering combustion or explosion. The risk of smouldering increases with decreasing particle size, while the difference in fire behaviour due to particle sizes needs to be studied in more detail. One of the techniques used to avoid, or decrease, the risk of smouldering is inertization. Inertization with gases is ineffective due to the difficulty gas has in accessing all voids in solid materials. An alternative solution is to use inert solids instead of gas.This research empirically studies the fire behaviour of wood pellets and wood dust with particle size of less than 1 mm, and the influence of solid inertization in both materials in two different configurations: mixed and layered. The ignition initiation of both particle sizes is similar, while the cool-down phase is quicker in the case of dust. However, inertization of dust needs a significantly higher amount of inert solids than in the case of pellets, being easier to avoid smouldering when the inerts are disposed in layers rather than mixed with the materials.

In situ preparation of aluminum-copper pentafluorobenzoate energy microspheres: Enhancing aluminum combustion properties in composite propellants

Aluminum powder is the main metal fuel in composite propellants, and upgrading the proportion of aluminum powder loaded in solid propellants is currently one of the most effective means of increasing propellant energy. Nonetheless, the substantial disparity in boiling points between the core aluminum particles and the alumina layer enveloping their surfaces often results in reduced reactivity, inadequate combustion, and combustion agglomeration during the combustion process of the aluminum powder. Herein, copper pentafluorobenzoate (CuPF) interfacial layer was established on the surface of aluminum powder through the self-assembly coordination reaction between pentafluorobenzoic acid and copper ions, and Al-CuPF energy microspheres were successfully prepared. A comprehensive examination was carried out to scrutinize the surface morphology, elemental composition, and distribution of the Al-CuPF energy microspheres. Furthermore, meticulous studies were conducted on the ignition and combustion properties of these Al-CuPF energy microspheres under various atmospheric conditions. It was found that the Al-CuPF interfacial layer within the Al-CuPF energy microspheres plays a pivotal role in enhancing ignition initiation and acting as a catalyst to facilitate the more efficient combustion of aluminum powder. Moreover, the combustion behavior of Al-CuPF energy microspheres when integrated into composite propellants has been exhaustively researched. Notably, composite propellants incorporating Al-CuPF energy microspheres exhibit heightened burning temperatures and an increased burning rate. Additionally, the combustion and agglomeration dynamics of Al-CuPF energy microspheres on the propellant burning surface were meticulously documented using a high-speed camera. The findings revealed that Al-CuPF energy microspheres spend a significantly shorter duration on the propellant burning surface and notably mitigate the occurrence of aluminum agglomeration issues thereon. This research contributes fresh insights into the application of innovative aluminum-based fuels within the realm of composite propellants.

Operational Forest-Fire Spread Forecasting Using the WRF-SFIRE Model

In the present research, the open-source WRF-SFIRE model has been used to carry out surface forest fire spread forecasting in the North Sikkim region of the Indian Himalayas. Global forecast system (GFS)-based hourly forecasted weather model data obtained through the National Centers for Environmental Prediction (NCEP) at 0.25 degree resolution were used to provide the initial conditions for running WRF-SFIRE. A landuse–landcover map at 1:10,000 scale was used to define fuel parameters for different vegetation types. The fuel parameters, i.e., fuel depth and fuel load, were collected from 23 sample plots (0.1 ha each) laid down in the study area. Samples of different categories of forest fuels were measured for their wet and dry weights to obtain the fuel load. The vegetation specific surface area-to-volume ratio was referenced from the literature. The atmospheric data were downscaled using nested domains in the WRF model to capture fire–atmosphere interactions at a finer resolution (40 m). VIIRS satellite sensor-based fire alert (375 m spatial resolution) was used as ignition initiation point for the fire spread forecasting, whereas the forecasted hourly weather data (time synchronized with the fire alert) were used for dynamic forest-fire spread forecasting. The forecasted burnt area (1.72 km2) was validated against the satellite-based burnt area (1.07 km2) obtained through Sentinel 2 satellite data. The shapes of the original and forecasted burnt areas matched well. Based on the various simulation studies conducted, an operational fire spread forecasting system, i.e., Sikkim Wildfire Forecasting and Monitoring System (SWFMS), has been developed to facilitate firefighting agencies to issue early warnings and carry out strategic firefighting.

Kinetic insights into ammonia-hydrogen doped ignition and emission assisted by nanosecond pulsed discharge

Non-equilibrium plasma is applied for the first time to ignite the ammonium-hydrogen mixture and reduce the NOx/N2O emission with effect in this work. Gas chromatography (GC) experiments as well as a detailed kinetic model, including neutral molecules, free radicals, charged particles, vibratory excited states, and electron excited states, are integrated to investigate the kinetic process of ammonia-hydrogen doped ignition and NOx/N2O emission facilitated by nanosecond pulsed discharge. The numerical model closely matches the GC-measured values of NH3 consumption, H2 increase, and N2O production. Pathway fluxes of important species and sensitivity analysis of ignition delay time reveal that the addition of non-equilibrium plasma has an obvious promotion effect on ammonia and hydrogen-doped oxidation and ignition. The initial ignition temperature significantly impacts the ignition delay time, with a more pronounced plasma-promotion effect observed at lower temperatures. Conversely, as the hydrogen mixing ratio increases, the ignition delay time decreases, yet the generation of NO and N2O increases. This is attributed to the heightened production of H and NH through elementary reactions such as NH3+HNH2+ H2, H + O2O + OH, and OH + H2H + H2O. Nevertheless, NO and N2O emissions are reduced by 1-2 orders of magnitude with plasma assistance compared to auto-ignition. The reduction in NO emissions can be attributed to increased consumption in the pathway of NO + NH2N2 + H2O and decreased formation in the pathways of HNO + O2HO2 + NO and NH + NON2O + H. Additionally, it was discovered that the electron attachment dissociation reaction e + N2O → O− + N2 predominantly contributes to the reduction of N2O. These research findings significantly contribute to advancing our understanding of the kinetics involved in ammonia-hydrogen doped ignition and emissions, particularly with plasma assistance, for potential engine applications.

Research on nonequilibrium plasma-assisted evaporation and ignition of n-decane droplet

To evaluate the nanosecond pulsed discharge plasma-assisted evaporation and ignition attributes of hydrocarbon fuel droplets, numerical models are established. The influences of nonequilibrium plasma on the characteristics of n-decane droplet evaporation and ignition are numerically studied through a loosely coupled method employing a one-dimensional (1D) fully transient model of droplet evaporation and ignition and a model of nanosecond pulse plasma discharge. The results show that the reaction rate of the initial phase of n-decane droplet ignition is increased by nonequilibrium plasma. In addition, both the evaporation and ignition of the droplet are accelerated. Increasing the reduced electric field of the discharge leads to decreases in the droplet ignition delay time, survival time, and shortening amplitude. The evaporative cooling effect, which occurs at the initial phase of droplet ignition and typically decreases the local temperature surrounding a droplet surface, is weakened by the plasma. As the reduced electric field increases, the time to generate a high-temperature zone (>1800 K) decreases, while its duration increases. The initial phase of n-decane droplet ignition, in which the flame temperature increases while the flame radius decreases, is strongly affected by the plasma during the initial ignition phase. However, the plasma has little impact on the peak flame temperature and the flame radius during the stable combustion phase of the droplet. According to reaction kinetics analysis, the plasma directly interferes with the elementary reactions R330 (nC10H22 + O = 3-C10H21 + OH) and R331 (nC10H22 + O = 2-C10H21 + OH) of n-decane/air combustion. Moreover, the dissociation and oxidation processes of intermediate products are accelerated. Then, the important reaction rates, which determine the ignition delay time, increase indirectly. Thus, the overall ignition delay time of the n-decane droplet is shortened.

Numerical simulation of the damage and ignition responses of high explosives under low-velocity impact using the SPH method

The damage evolution and ignition mechanism of high explosives are of great importance in assessing the safety of munitions and guiding the design of munitions. In this study, the smoothed particle hydrodynamics (SPH) method is combined with a viscoelastic–viscoplastic-damage constitutive model and a hot spot model to explore the damage and ignition responses of high explosives under low-velocity impact. In particular, the sub-particle method is developed in the SPH method to combine the macroscopic constitutive model with the mesoscopic hot spot model. First, the damage evolution of a compressed plate containing a cavity and the ignition response of a single particle at a given pressure and strain rate are studied separately, and the simulation results are validated by experimental results and existing finite element method simulations. Subsequently, the impact shear and crack extrusion tests of high explosives with complex stress states are explored, respectively. For typical pressed PBX under impact-shear loading, a large damage region is formed in the high explosives due to the tensile stress formed by the meeting of rarefaction waves, and the initial ignition region is mainly located in the region where the outer edge of the rod is in contact with the high explosives and extends in a circular shape to the inside of the explosives. For typical pressed PBX under crack extruded loading, the damage region is mainly concentrated in the materials squeezed into the crack, and the initial ignition region is mainly located around the crack and gradually extends above the crack. The results indicate that the proposed SPH method is capable of modeling the damage and ignition responses of high explosives under complex stress states.

Frontal Polymerization for the Rapid Obtainment of Polymer Composites.

Among the different polymerization techniques, frontal polymerization (FP) has gained high interest from the scientific community because of its peculiar characteristics: in particular, compared to classic polymerization reactions, FP allows for a better exploitation of the heat of polymerization involved, without requiring any external energy input apart from an initial photo or thermal ignition that triggers the reaction. The latter usually propagates in a few tenths of seconds or (at most) minutes through a hot self-sustaining polymerization front, giving rise to the formation of fully cured thermosetting networks or thermoplastic polymers. Furthermore, different polymerization mechanisms can be involved in FP reactions, comprising cationic or anionic, ring-opening metathesis, and free-radical polymerization, among others. Further, it is possible to run FP reactions in bulk, in solution, or even using solid monomers if they are melted at the temperature of the front, notwithstanding the possibility of using reactive systems containing fillers or fiber/fabric reinforcements. In this context, the use of FP is becoming very important also for the design and production of advanced (nano)composite materials, saving processing time and achieving the completeness of the curing reaction, even in the presence of high filler/reinforcement loadings. Therefore, this mini-review aims to provide the reader with the basics of FP and its main peculiarities, even in the context of preparing high-performing composites. In this respect, some recent case studies witnessing the potentialities of frontal polymerization for the design of advanced (nano)composite systems will be elucidated. Finally, some perspectives about possible future developments will be proposed.

A criterion of dimensional design to improve flame spread resistance of magnesium alloy components

A criterion for predicting the flame spread time of stick-shaped Mg alloy samples was proposed based on the law of energy conservation. It is indicated that the flame spread time is mainly affected by the material and sample dimension. The initial temperature and ignition temperature of the control volume and the S/lc ratio (the cross-sectional area/cross-sectional circumference) of the sample are decisive for the flame spread time. The flame spread time is proportional to the ΔH (the energy required to heat a unit mass of sample from initial temperature to ignition temperature) and the S/lc ratio, which is confirmed in three Mg alloys of Mg–8.5Al–0.5Zn–0.2Mn, Mg–2.7Nd– 0.4Zn–0.6Zr and Mg–4.0Y–3.3Nd–0.5Zr. For samples with the same dimension, the Mg–8.5Al–0.5Zn–0.2Mn alloy sample possesses the largest ΔH and the longest flame spread time. For samples with constant length and cross-sectional area, the sample with circular cross-section has the largest S/lc ratio and the best flame spread resistance in the same alloy.

Temperature Distribution Within an Ignition Kernel Initiated by a Laser-Induced Plasma

The sizes of, and temperature distributions within, ignition kernels initiated by a Q-switched neodymium-doped yttrium aluminum garnet laser-induced plasma in an unconfined lean premixed hydrogen-air upward jet flow are investigated. The experiments involved a range of jet velocities and a range of deposited laser energies at a fixed height above the exit along the axis of a burner. The growth of, and the temperature distributions within, the ignition kernels, as affected by the size and the energy distribution of the laser-induced plasma, are monitored with an infrared camera. The initial ignition kernels’ areas are larger with higher laser pulse energies and remain unchanged up to 20 μs and then increase by factors of up to 3 at 100 μs. The change in the kernel area caused by the jet velocities is less than 1.5%. An increase of the bulk velocity by 190% decreases the ignition kernel temperature by 6%. This reduction in the ignition kernel temperatures is because of an increase in energy losses by a factor of 2 and decreases in heat releases by 2% at 10 μs and by 11% at 100 μs. The present contributions are: measurements of and insights into temperature distributions and kernel development rates during the laser-induced plasma ignition process at different deposited energies and flow velocities.

Study on the effect of particle morphology on transient dispersion behavior and ignition of Al[sbnd]Mg alloy powder

Particle morphology has a significant effect on the explosion of energetic dust which includes heat transfer and transient dispersion behavior. This study aimed to investigate the differences in transient dispersion characteristics of Al-Mg alloy powders with different shapes using Particle Image Velocimetry (PIV) and to elucidate their effects on subsequent flame propagation and explosion parameters. The results demonstrated that irregular dust exhibited lower agglomeration and terminal fall velocity (TFV) compared to spherical dust, leading to a higher overall concentration of dust involved in the explosion. In addition, the turbulence intensity in the critical ignition zone of irregular particles was relatively high, resulting in particles having more active motion characteristics during the initial ignition phase. Therefore, irregular dust exhibited more intense flame phenomena and higher explosion parameters. These findings emphasize the importance of considering particle morphology when assessing the risk associated with metal dust explosions.

Evaluation of high-pressure syngas ignition under high-CO2 dilution in shock tubes

Due to its importance as a candidate fuel for power cycles for future energy production, there have been active efforts to improve our understanding of the chemical kinetics of the Allam-Fetvedt cycle that utilizes syngas highly diluted with CO2. Shock-tube ignition delay times (IDT) of syngas-CO2 mixtures over a range of pressures, syngas blends, and equivalence ratios are now available in the literature, but their unique behavior deserves further study before the resulting data can be used to modify existing syngas kinetics models. In this study, an analysis of CO2-diluted syngas ignition behind reflected shock waves was conducted at the High-Pressure Shock Tube facility at Texas A&M University using an endwall imaging system. A syngas blend of 1:1 H2:CO at an equivalence ratio of 1 was studied at pressures around 12 atm for CO2 dilutions of 85, 88, and 94 % by volume. The combined results of the high-speed OH* imaging through the endwall and OH* time histories from sidewall windows indicate that the initial ignition event appears to be homogeneous and occurs first near the endwall, with no apparent premature ignition or localized flame kernels. An important finding of this investigation is that the existing syngas-CO2 IDT data in the literature are likely free from shock-tube ignition inhomogeneities. Therefore, they can be used to improve existing chemical kinetics mechanisms, which currently have trouble modeling the existing literature data over the range of temperatures of the shock-tube studies (∼1000 – 1400 K). Additionally, the lack of a measured post-combustion pressure rise makes it necessary to use a constant-pressure-enthalpy constraint when modeling the shock-tube IDT event.

Numerical simulation and experimental application of a 300 MW boiler combustion system

In the actual operation of a 300 MW boiler, there are some problems such as unstable combustion, high combustible material of fly ash and slag, and large thermal deviation on both sides of steam. The Cooper method is used to divide the three parts of the furnace by a hexahedral structured grid, which can reduce the grid number and improve the numerical simulation calculation precision. The Realization k-ε turbulent model is used to simulate the gas-solid two-phase flow in the furnace before and after reconstruction. The boundary of the calculation model adopts the actual operating parameters, and the numerical calculation adopts the three-dimensional steady-state calculation - Simple algorithm. The conclusions are as follows: the amount of pulverized coal powder falling into the cold ash hopper is reduced from 0.077 kg/m3 before the reconstruction to 0.045 kg/m3 after the reconstruction, with a decrease of about 42%. The secondary air concentration arrangement in the lowest two layers strengthened the secondary air supporting capacity. The residence time of pulverized coal particles in the furnace is increased from 30.59 s before the reconstruction to 39.97 s after the reconstruction, and the time is extended by about 9.4 s, which is beneficial to the combustion of pulverized coal particles. The centralized arrangement of primary air in the lowest two layers is beneficial to the initial ignition and stable combustion of pulverized coal gas. The downdip of the tertiary air incidence angle reduces the rotational momentum of the tertiary airflow, and the increase of the rotational momentum of the over-fire air angle is conducive to weakening the residual rotation at the furnace outlet. After the implementation of the reconstruction measures, the boiler can be stably burned at 150 MW, the combustible material of fly ash and slag are reduced to the controllable range, the steam thermal deviation is significantly reduced, and the boiler operating parameters are stable.

Multi-factor influencing on detonation quenching performance of hydrogen crimped-ribbon flame arrester

By self-designed experimental apparatus, the influences of initial condition, the structure parameters of flame arrester (FA) and expansion chamber (EC) on hydrogen detonation quenching performance of crimped-ribbon flame arrester are investigated. The effects of different factors on the detonation velocity (Vf) and pressure (Pf) accessing FA, the attenuation extent and the quenching results are determined. The experimental results present that the Vf and Pf exhibit a tendency to increase and then decrease as the hydrogen concentration increases. Both Vf and Pf are raised by enhancing initial pressure and ignition energy, and the attenuation effect of FA is gradually weakened. Meanwhile, the detonation intensity applied to the flame arrester element (FA-E) is reduced due to the attenuation effect of the EC, thus leading to flame being more easily quenched. The baffle and extended type ECs are more effective than the conventional type EC in reducing the detonation velocity, and the quenching performance of extended type EC is better. Then, the reduction of porosity and the rise of element thickness effectively enhance the wall heat transfer and boundary layer effects, resulting in the increasing of velocity deficit and the quenching of detonation. Furthermore, the multi-factor prediction models for Vf and Pf under the action of the initial conditions are built by the response surface method (RSM). The influence extent of factors and their interaction on Vf and Pf are also analyzed and confirmed.

A Full-scale Fire Test on Electric Vehiclein an Underground Car Parks

A full-scale test was conducted to evaluate the risk of a modern battery electric vehicle (BEV) fire in an underground car park. A test rig 7,800 × 7,800 × 2,300 mm in size was built to simulate the corner segment of an underground car park. The BEV was positioned in a parking bay at a corner of the structure . The lithium-ion battery pack was heated using an electric heating sheet to activate thermal runaway inside the pack. The temperature distribution in the internal space of the test rig was measured using a thermocouple. The incident heat fluxes on neighboring cars were also estimated using heat flux gauges positioned around the test vehicle. Deflagration venting was observed instantaneously after the initial ignition of the flammable gas accumulated under the ceiling of the test rig. This phenomenon accelerated the growth of the BEV fire, resulting in an average ceiling jet temperature of 1,000 ℃ and a peak heat flux of 225 kW/m<sup>2</sup>.

Experimental Research and Numerical Analysis of Marine Oil Leakage and Accidental Ignition in Fishing Vessels

The hazard of highly combustible marine oil leakage greatly increases fishing vessel operation risks. This research integrates an experiment to explore the coupling mechanism of a typical heated surface of an engine room as a source to ignite marine oil. A numerical model is established that depicts the dynamic process of and variations in the combined effects regarding multiple factors of oil ignition under actual experiment. The leaked marine oil is ignited with a heated surface, relevant models are applied to reproduce the results, and the influences of specific parameters of a fishing vessel’s engine room are analyzed. The results indicate that the leaked oil boils violently on the heated surface, and a vapor film forms on the oil surface. Increased heated-surface temperatures lead to a significant difference in the initial ignition occurrences of marine oil, and the distance between the ignition height and oil is closely related to the engine room environment. The ignition probability of marine oil shows a gradually increasing trend with elevated heated-surface temperatures. The ignition height presents a downward trend with the increase in the heated-surface temperature, while the engine room’s humidity in air inhibits the upward transfer of heat; however, the degree of inhibition is limited accordingly. The results evidence that this comparative work can be an effective approach to reveal the impacts of marine oil, heat source, ventilation velocity, and humidity on initial ignition characteristics. Additionally, this work provides a basis for setting up emergency planning with appropriate monitoring equipment and further preventing vessel fires due to oil–thermal ignition.

Advances and Challenges in Combustion Control of Radio Frequency Oscillating Plasma Discharge

Article Advances and Challenges in Combustion Control of Radio Frequency Oscillating Plasma Discharge Linyan Wang , Xiao Yu , Graham Reader , and Ming Zheng * Department of Mechanical, Automotive and Materials Engineering, University of Windsor, 401 Sunset Avenue, Windsor, N9B 3P4 Ontario, Canada * Correspondence: mzheng@uwindsor.ca Received: 18 July 2023 Accepted: 13 September 2023 Published: 20 September 2023 Abstract: Oscillating plasma (corona) ignition is a promising technique for producing a larger initial ignition volume for achieving cleaner combustion. The oscillating plasma system provides a quick response to the ignition command compared with the conventional transistor-coil-ignition systems (TCI). Subsequently, the shorter combustion duration contributes to further improvement of engine efficiency under lean/diluted conditions. The challenges of oscillating plasma ignition appear under elevated background pressures, mostly owing to fewer plasma streamers and even void discharge, thus the advantage of oscillating plasma discharge over spark discharge is compromised. To suffice the industrial applications, the challenges of plasma generation and control platforms are investigated and discussed in this work. The challenges include ignition control, background condition impacts, and other external disturbances. A flexible modulation for oscillating plasma generation is established, with the measurements of discharge voltage and current. High-speed imaging, simultaneous with electrical waveform measurements is applied to record the plasma formation and flame propagation. This research provides advances in the ignition control for the oscillating plasma discharge, adding a foundation and reference for the oscillating plasma diagnostics under engine-like conditions with variations of pressure, temperature, gas composition, and flow pattern.