Extreme Temperature Conditions Research Articles

The Effectiveness of the Bacteria Derived Extremolyte Ectoine for the Treatment of Allergic Rhinitis.

Nonpharmacological therapies with a good tolerability and safety profile are of interest to many patients with allergic rhinitis, as a relevant proportion of them have reservations about guideline-concordant pharmacological therapies due to their local irritations and side effects. Ectoine is a bacterial-derived extremolyte with an ability to protect proteins and biological membranes against damage caused by extreme conditions of salinity, drought, irradiation, pH, and temperature. Evidence from preclinical and clinical studies attests its effectiveness in the treatment of several inflammatory diseases, including allergic rhinitis. In this review, we analyzed 14 recent clinical trials investigating ectoine nasal spray in patients with allergic rhinitis and/or conjunctivitis, including sensitive patient groups like children or pregnant women. Some studies investigated monotherapy with ectoine; others investigated combination therapy of ectoine and an antihistamine or a corticosteroid. Analysis of the study results demonstrated that patients with mild-to-moderate symptoms of allergic rhinitis can be successfully treated with ectoine-containing nasal spray. When applied as monotherapy, ectoine exerted noninferior effects compared to first-line therapies such as antihistamines and cromoglicic acid. Using ectoine as an add-on therapy to antihistamines or intranasal glucocorticosteroids accelerated symptom relief by days and improved the level of symptom relief. Importantly, concomitant treatment with ectoine was proven beneficial in a group of difficult-to-treat patients suffering from moderate-to-severe rhinitis symptoms. Taken together, the natural substance ectoine represents a viable alternative for allergic rhinitis and conjunctivitis patients who wish to avoid local reactions and side effects associated with pharmacological therapies.

Dislocation dynamics modelling of the creep behaviour of particle-strengthened materials.

Plastic deformation in crystalline materials occurs through dislocation slip and strengthening is achieved with obstacles that hinder the motion of dislocations. At relatively low temperatures, dislocations bypass the particles by Orowan looping, particle shearing, cross-slip or a combination of these mechanisms. At elevated temperatures, atomic diffusivity becomes appreciable, so that dislocations can bypass the particles by climb processes. Climb plays a crucial role in the long-term durability or creep resistance of many structural materials, particularly under extreme conditions of load, temperature and radiation. Here we systematically examine dislocation-particle interaction mechanisms. The analysis is based on three-dimensional discrete dislocation dynamics simulations incorporating impenetrable particles, elastic interactions, dislocation self-climb, cross-slip and glide. The core diffusion dominated dislocation self-climb process is modelled based on a variational principle for the evolution of microstructures, and is coupled with dislocation glide and cross-slip by an adaptive time-stepping scheme to bridge the time scale separation. The stress field caused by particles is implemented based on the particle–matrix mismatch. This model is helpful for understanding the fundamental particle bypass mechanisms and clarifying the effects of dislocation glide, climb and cross-slip on creep deformation.

(Invited) A Brief Overview and Future Outlook on the Progress of III-Nitride Semiconductors Research

The increasing need for devices capable of performing under extreme condition of power and temperature, and opto-electronic devices operating in the UV-Vis spectral range has been the principal driving force for research interest in III-Nitrides semiconductors over the last three decades. Progress in bulk growth and film deposition techniques for homo- and hetero-epitaxial growth of III-Nitride semiconductors has led to successful fabrication and commercialization of an increasing number of devices that are revolutionizing both the optoelectronic and electronic device industries.Many relevant figures of merit related to electronic device performance scale superlinearly with the band gap; hence, ultra-wide band gap (UWBG) materials (Eg > 3.4 eV) have the potential for far superior performance than conventional WBG materials such as GaN and SiC. UWBG materials will be critical enablers of future electronic components and systems, and a fundamental understanding of their synthesis and properties is critical to exploiting their advantages. In particular, cubic boron nitride (c-BN), among the semiconductor materials in the UWBG group (c-BN, AlN, Ga2O3, and diamond), with a band gap of ~6 eV and thermal conductivity of 13 W/mK (second only to diamond, 20 W/mK) offers the best combination of breakdown voltage and specific on-resistance. Another advantage of c-BN over other UWBG semiconductors is that it can be doped with donors and acceptors, enabling the fabrication of bipolar devices.The development of high quality GaN substrates and device grade films will be reviewed and a brief overview of the intrinsic properties of the WBG and UWBG semiconductors will be presented.

Tribological behavior of hybrid aluminum self-lubricating composites under dry sliding conditions at elevated temperature

ABSTRACT In this study, the influence of n-Al2O3 (aluminum oxide) and graphene nanoplatelet (GNP) on the tribological properties of a eutectic Al–Si (aluminum silicon) alloy was investigated. For Al–Si/n-Al2O3 (advanced composite), the coefficient of friction (COF) decreased by 34.41% and the wear resistance enhanced by 43.75% compared with base matrix alloys under high temperature (HT) conditions. For Al–Si/n-Al2O3/GNP (hybrid composite), COF decreased by 61.41% and the wear resistance improved by 96.87% at HT compared with base matrixes (eutectic Al–Si alloy). This finding was attributed to enhanced lubrication through GNP, glazed layer, thin tribooxide film (TTL) and mechanical mixed layer (MML) present on wear scars. Melt wear caused by scuffing was the main wear mechanism for the base composition at 300 and 400°C, and adhesion abrasion, crack formation and delamination pits were the wear mechanisms observed for the advanced and hybrid composites at extreme temperature conditions. Highlights Al–Si/ n-Al2O3 and Al–Si/ n-Al2O3/GNP composites were fabricated through spark plasma sintering. The tribological performance of the fabricated composite samples was investigated under dry sliding at elevated operating temperatures (100–400°C). The coefficient of friction and wear resistance improved with an increase in the secondary GNP reinforcement. Transition in the wear regime occurred at approximately 0.8 of melting temperature. The self-lubrication mechanism of GNP was observed on the wear track, which significantly reduced scar surface roughness.

Axial crashworthiness performance of foam-based composite structures under extreme temperature conditions

Due to their unique properties, metal foams can be used under extreme temperature conditions. To this end, this paper investigates the influence of temperature (−196, −25, 25 and 250 °C) on the axial crashworthiness performance of foam-based composites. The composite structures are made of aluminum thin-walled circular tubes, filled with aluminum alloy (A356) foam. It is found that the highest mechanical characteristics are obtained at the cryogenic temperature (−196 °C) due to the hardening behaviour of the matrix material in both foam and tube. Contrary, the softening behaviour of the matrix material at high temperature (250 °C) decreases the mechanical properties of the composite material. Between two extreme temperatures, a transition from brittle-to-ductile deformation occurs. The deformation transition is observed both on the stress–strain curves (gradual reduction of oscillations of the plateau region) and the macroscopic images of the compressed samples (changing the crushing mode from non-axisymmetric < Diamond > to axisymmetric < Concertina >). Moreover, due to the foam-tube interaction effect, the experimental results show that the quasi-static compressive behavior and collapse mechanisms of the composite structures has considerably improved (over 50% in some cases). Furthermore, the strength properties and energy absorption performances of the foam filled tube shows significantly higher values (almost double) compare to empty one.

Chemistry Under Shock Conditions

Shock loading takes materials from ambient conditions to extreme conditions of temperature and nonhydrostatic stress on picosecond timescales. In molecular materials the fast loading results in temporary nonequilibrium conditions with overheated low-frequency modes and relatively cold, high-frequency, intramolecular modes; coupling the shock front with the material's microstructure and defects results in energy localization in hot spots. These processes can conspire to lead to a material response not observed under quasi-static loads. This review focuses on chemical reactions induced by dynamical loading, the understanding of which requires bringing together materials science, shock physics, and condensed matter chemistry. Recent progress in experiments and simulations holds the key to the answer of long-standing grand challenges with implications for the initiation of detonation and life on Earth.

Pressure-induced symmetry lowering in Nb3Sn1−x superconductor

Cubic Pm-3n Nb3Sn0.92 superconductor (T c ∼ 16 K) was found to exhibit tetragonal instabilities at the superconducting state (T = 10 K). These instabilities are manifested through the appearance of reflections which are forbidden in the Pm-3n symmetry but are compatible with the P42/mmc structure which is observed in the Nb3Sn1−x system for higher Sn content at temperatures lower than ∼43 K. Nevertheless, the low-temperature structure of Nb3Sn0.92 remains metrically fully cubic, as concluded from single crystal synchrotron radiation diffraction experiments. Subsequent application of external pressure amplifies the observed instabilities with a resulting pseudo-cubic–tetragonal transformation at P = 3 GPa at 10 K and this transition is energy driven, as concluded from ab initio calculations. The electronic structures of the corresponding phases are virtually identical and, therefore, the pseudo-cubic–tetragonal transformation does not influence significantly the underlying electronic interactions. Consequently, no anomalies in the behavior of the critical temperature, T c, are expected at this pressure. However, anomalies in the upper critical field are anticipated during this transition, in analogy to the corresponding behavior observed during the cubic–tetragonal transformation in Nb3Sn1−x induced by increase in Sn content. Therefore targeted changes in composition could be used to enhance upper critical field of Nb3Sn1−x for specific extreme conditions of temperature and pressure.

Response analysis of HTPB propellant under extreme high temperature conditions

Temperature load is one of the loads that propellant grains are often subjected to. Temperature shock or temperature cycling will affect the structural integrity of propellant grains to a certain extent. How to ensure that the propellant grains meet the structural integrity requirements under temperature load conditions and ensure equipment the significance of a smooth launch is very important. In this paper, the HTPB propellant sample response analysis test is carried out based on the global temperature environment distribution of different temperature grades, and the extreme high temperature impact simulation experiment is carried out for the grains under the specific structure considering the impact of extreme high temperature conditions, and finally different models are constructed. The constitutive model of HTPB propellant under extreme high temperature, its grain meets the structural integrity criterion after being subjected to the impact of extreme high temperature.

Response Analysis of HTPB Propellant under Extreme Low Temperature Conditions

Temperature load is one of the loads that propellant grains are often subjected to. Temperature shock or temperature cycling will affect the structural integrity of propellant grains to a certain extent. How to ensure that the propellant grains meet the structural integrity requirements under temperature load conditions and ensure equipment the significance of a smooth launch is very important. In this paper, the HTPB propellant sample response analysis test is carried out based on the global temperature environment distribution of different temperature grades, and the extreme low temperature impact simulation experiment is carried out for the grains under the specific structure considering the impact of extreme low temperature conditions, and finally different models are constructed. The constitutive model of HTPB propellant under extreme low temperature, its grain meets the structural integrity criterion after being subjected to the impact of extreme low temperature.

New amphiphilic semi-interpenetrating networks based on polysulfone for anion-exchange membrane fuel cells with improved alkaline and mechanical stabilities

As considerable advance has recently been made in enhancing the conductivity of anion-exchange membranes, durability has become the critical requirement in the development of fuel cells. Such properties often develop at the expense of the other. In this work, new amphiphilic semi-interpenetrating networks composed of free polysulfone and crosslinked polysulfone are synthesized for the first time. The same nature of both polymers makes them highly compatible. The free polymer provides the hydrophobic component, whereas the crosslinked polysulfone, functionalized with trimethylammonium, 1-methylimidazolium, or 1,2-dimethylimidazolium groups, is responsible for the ionic conductivity. The compatibility between both components in the blend, improves the mechanical properties, while unaffecting the transport properties. Thus, the obtained membranes exceed the mechanical behaviour of commercial materials, even in conditions of extreme humidity and temperature. The tensile strength of these synthesized membranes can reach to relatively high values, and when compared to the commercial PSU, the difference in tensile strength can be noted to be as low as 10%. Moreover, the tensile strength and the ductility values of the crosslinked PSU are higher than those obtained with non-crosslinked PSU. Furthermore, the membranes presented in this work show a great alkaline stability (e.g. semi-interpenetrating network containing 1,2-dimethylimidazolium maintains 87% of the ionic conductivity after 14 days of treatment). Thus, these membranes provide an improvement in the durability limiting factors, in comparison to functionalized polysulfones, fulfilling the requirements to be used as electrolytes in anion-exchange membrane fuel cells.

Development of an MFL Coil Sensor for Testing Pipes in Extreme Temperature Conditions.

This paper aims to design a coil sensor for corrosion monitoring of industrial pipes that could detect variations in thickness using the MFL (Magnetic Flux Leakage) technique. An MFL coil sensor is designed and tested with pipe sample thicknesses of 2, 4, 6, and 8 mm based on the magnetic field effect of ferrite cores. Moreover, a measurement setup for analysing pipe samples up to a temperature of 200° Celsius is suggested. Experimental results reveal that the MFL coil sensor can fulfil the requirements for MFL testing of pipes in high temperature conditions, and that the precision of MFL monitoring of pipes to detect corrosion at high temperatures can be improved significantly.

Failure Analysis of Engine Valves and its Performance Evaluation under Various Titanium Based Composite Coatings Using FE Analysis

In an internal combustion engine poppet valve is the crucial component which often opens and closes, thereby regulating gas flow in an engine cylinder. During engine operation, the valve is exposed to high temperature gases (thermal load) along with spring and cam loads (mechanical load). Due to high temperatures and fatigue loads, the valves are subjected to metallurgical changes and leads to failure. In order to resist these extreme conditions of high temperature and mechanical loads, the engine valve should possess special properties such as high surface hardness, a good amount of thermal conductivity, and fatigue strength. In this work, the reasons for the failure of two wheeler engine valve were evaluated and found that failure takes place due to change in the chemical composition mainly due to thermal diffusion at the interfaces. Thermal barrier coatings on the valve surface arrest the temperature load and increase its life. In this work, the performance of various titanium based composite coatings, i.e., TiN, TiC, TiC-Al2O3, TiCN, TiAlN, TiN- Al2O3, DLC, and uncoated valves of two wheeler engine was simulated using Finite Element Analysis. The simulation results indicated that coated valves have less thermal and fatigue loading and have more life than the uncoated valve. The Finite element simulation results of both coated and uncoated valves are presented and analyzed in this paper.

Thermodynamic properties of ε -Fe with thermal electronic excitation effects on vibrational spectra

The thermodynamic properties of hcp-iron ({\epsilon}-Fe) are essential for investigating planetary cores' internal structure and dynamic properties. Despite their importance to planetary sciences, experimental investigations of {\epsilon}-Fe at relevant conditions are still challenging. Therefore, ab initio calculations are crucial to elucidating the thermodynamic properties of this system. Here we use a free energy calculation scheme based on the phonon gas model compatible with temperature-dependent phonon frequencies. We investigate the effects of electronic thermal excitations, which introduces a temperature dependence on phonon frequencies, and the implication for the thermodynamic properties of {\epsilon}-Fe at extreme pressure (P) and temperature (T) conditions. We disregard phonon-phonon interactions, i.e., anharmonicity and their effect on phonon frequencies. Nevertheless, the current scheme is also applicable to T-dependent anharmonic frequencies. We conclude that the impact of thermal electronic excitations on vibrational properties is not significant up to ~ 4,000 K at 200 GPa but should not be ignored at higher temperatures or pressures. However, the static free energy, Fst, must always include the effect of thermal excitation fully in a continuum of Ts. Our results for isentropic equations of state show good agreement with data from recent ramp compression experiments up to 1,400 GPa conducted at the National Ignition Facility (NIF).

Novel production of biodispersant by Serratia marcescens UCP 1549 in solid-state fermentation and application for oil spill bioremediation

ABSTRACT Oil spills in aquatic ecosystems cause irreparable damage to marine life and the coastal populations of affected areas. In recent years, chemical dispersants have been extensively used to remedy these impacted ecosystems, although these agents have been increasingly restricted due to their toxic potential. In this context, biosurfactants are emerging as a promising alternative to chemical dispersants, which have some advantages including low toxicity, high biodegradability and good ecological acceptability. Thus, this study aimed to the production of biosurfactant by the bacteria Serratia marcescens UCP 1549 for application as biodispersant. The experiment was carried out using wheat bran as substrate in solid-state fermentation (SSF) as low-cost technology. Biosurfactant production was verified by the reduction of surface tension (28.4 mN/m) and interfacial tension (4.1 mN/m) with n-hexadecane. Also, promising result of emulsification (94%) with burned motor oil was obtained. Acid precipitation yielded 52.0 g/kg dry substrate of biosurfactant, that was identified as an anionic compound of a lipopeptide nature by the Zeta potential and FTIR spectrum, respectively. The biomolecule showed stability under extreme conditions of temperature, pH and salinity, as well as low toxicity against the microcrustacean Artemia salina. In addition, the biosurfactant demonstrated excellent properties to dispersing burned motor oil in water (ODA = 50.24 cm2) and to washing of marine stones (100% removal of burned motor oil). Therefore, these results confirm SSF as a sustainable technology for the production of biodispersant by S. marcescens UCP 1549, promising in the bioremediation of marine ecosystems impacted by petroderivatives.

Inhibited radiation transmittance and enhanced thermal stability of silica aerogels under very-high temperature

Silica aerogels are applied extensively in thermal insulation due to their extra-low density and thermal conductivity. However, this can be heavily undermined under high temperature, especially beyond 700–800 °C, due to not only a high transparency for radiation heat transfer, but also an instability caused by nanoparticle collapse. The present study demonstrated a solution to this problem by two steps. Firstly, the size effect of nanoparticles is explored by experimentally preparing unconventional samples composed of large-diameter particles (larger than 20 nm). The prepared sample microstructures and radiative characteristics are investigated by SEM apparatus and FTIR measurements, respectively. Additionally, based on the fractal structures reconstructed using the Diffusion-Limited Colloid Aggregation (DLCA) method, the effects of particle size on thermal stability of silica aerogels are theoretically investigated and the light shielding performance is numerically analyzed by the Generalized Multiparticle Mie-solution (GMM) method. The simulation and experimental results indicate that the enhanced size of nanoparticles can improve the radiative inhibition and thermal stability property under high temperature significantly. However, the ideal above should be refined as it brings an increasing contribution of conduction heat transfer. Thus, a novel structure of core-mantle nanoparticle is proposed to retain the excellent resistance in radiation but avoid an increased thermal conduction. The present work may pave a new direction for developing aerogels under extreme temperature conditions, compared with the widely-used opacifier addition.

Features of construction of multi-storey buildings and structures made of monolithic reinforced concrete in various climatic conditions

The construction of high-rise buildings with load-bearing structures made of monolithic reinforced concrete with the required quality is not an easy task. This applies mainly to the production of works in extreme temperature and humidity conditions. As the practice of construction using traditional technologies shows, the concrete of the erected floors does not reach the required strength. In winter, it is 85-90% of the project. In addition, on the upper floors where the concrete is in the hardening stage, its strength on average is even lower. Thus, high-rise buildings made of monolithic reinforced concrete at the construction stage do not meet the requirements of stability and reliability to the perception of seismic loads. This situation is not taken into account at the design stage. In the normative design and design approaches, the condition for setting the grade strength of concrete is laid down. In fact, the real picture differs significantly from the estimated one. And it is necessary to study transient design situations. This means that when designing, you should consider options for different combinations of applied loads and the actual strength of the concrete structure of the floors. Modern construction technologies provide favorable conditions for concrete hardening. All of them are associated with a significant increase in production costs (electricity, materials, labor), construction time, and therefore the cost of building construction. The way out of this situation is a systematic linking of design issues and organizational and technological capabilities of construction production. Options for such solutions are discussed in the article.

Smartphone-based competitive immunoassay for quantitative on-site detection of meat adulteration

Rapid, sensitive, and portable analytical methods for on-site inspection of food fraud are now an urgent requirement to ensure food quality and satisfy the ethnic considerations of consumers. Hence, for the first time, a colorimetric smartphone-based immunoassay was developed for the on-site detection of pork adulteration in meat. In detail, the immunoassay was based on a competitive strategy in which immobilized standard porcine IgG competed with the target porcine IgG extracted in a single step from meat samples. The parameters involved in each step of the immunoassay conception and the digital colorimetric detection were carefully investigated and optimized. Using polystyrene microplates as ready-to-use stable and portable immunoplatforms, TMB as chromogenic substrate, smartphone as signal readout, and Image J software for image processing; the developed immunoassay was able to detect as low as 0.01% of pork in meat mixtures in a total assay time of 30 min. The selectivity of the immunoassay was evaluated for different meat species, and it was shown to selectively respond only to pork. Furthermore, excellent stability of the prepared immunological platform was demonstrated under extreme temperature conditions (50 °C), which confirms its high portability potential for in situ quantification of pork, while being relatively cost effective and non-laborious. The developed method also provides great precision (RSD < 6%) and accuracy (relative error< 6%). Given the universal use of smartphones as portable and affordable devices, such format of immunoassay could be a promising approach for rapid and sensitive real-time monitoring of food fraud.

Sugarcane vinasse extreme thermophilic digestion: a glimpse on biogas free management.

The high temperature in which sugarcane vinasse (SV) is generated (~ 90°C) and the positive effect of higher temperatures in biochemical reactions have motivated the evaluation of SV anaerobic digestion (AD) under extreme temperature conditions. Two-stage (acidogenic/methanogenic) and single-stage (methanogenic) AD of SV were evaluated under 70°C in structured-bed reactors. The extreme temperature was beneficial to the acidogenic step of the two-stage AD process. The methane production, however, was hindered at 70°C. The VMP of the single and two-stage reactors accounted, respectively, for only 13% and 7% of the production rate reported in sugarcane vinasse AD at 55°C. At 70°C, the main genera responsible for methane production was Methanothermobacter and the acetoclastic methanogenesis did not occur, resulting in acetic acid build up (15,800mgL-1). These results brought a new perspective for sugarcane vinasse management, with acetic acid production alternatively to methanization. In this perspective, two-stage process would be composed of acidogenic and acetogenic reactors, and beyond acetate, hydrogen and other soluble compounds could be recovered in a complete biorefinery process.

Demonstration of a uniform, high-pressure, high-temperature gas cell with a dual frequency comb absorption spectrometer

Accurate absorption models for gases at high pressure and temperature support advanced optical combustion diagnostics and aid in the study of harsh planetary atmospheres. Developing and validating absorption models for these applications requires recreating the extreme temperature and pressure conditions of these environments in static, uniform, well-known conditions in the laboratory. Here, we present the design of a new gas cell to enable reference-quality absorption spectroscopy at high pressure and temperature. The design centers on a carefully controlled quartz sample cell housed at the core of a pressurized ceramic furnace. The half-meter sample cell is relatively long compared to past high-pressure and -temperature absorption cells, and is surrounded by a molybdenum heat spreader that enables high temperature uniformity over the full length of the absorbing gas. We measure the temperature distribution of the sample gas using in situ thermocouples, and fully characterize the temperature uniformity across a full matrix of temperatures and pressures up to 1000 K and 50 bar. The results demonstrate that the new design enables highly uniform and precisely known temperature and pressure conditions across the full absorbing path length. Uniquely, we test the new gas cell with a broadband (~2500 cm−1), high-resolution (0.0066 cm−1) dual frequency comb spectrometer that enables highly resolved absorption spectroscopy across a wide range of temperature and pressure conditions. With this carefully characterized system, we measure the spectrum of CO2 between 6800 and 7000 cm−1 at pressures between 0.2 and 20 bar, and temperatures up to 1000 K. The measurements reveal discrepancies from spectra predicted by the HITRAN2016 database with a Voigt line shape at both low- and high-pressure conditions. These results motivate future work to expand absorption models and databases to accurately model high-pressure and -temperature spectra in combustion and planetary science research.

Experimental investigation of ignition by multichannel gliding arcs in a swirl combustor

In the extreme conditions of high altitude, low temperature, low pressure and high speed, the aircraft engine has a strong tendency to extinguish and it is then difficult to start secondary ignition, which means that re-ignition of the aircraft engine faces great challenges. Additionally, the ability of the single-channel gliding arc (1-GA) in assisting the ignition under extreme conditions is weak. In this paper, to solve this problem, a multichannel gliding arcs (MGA) system is proposed, using the principle of multichannel discharge. Experiments on the electrical characteristics and ignition performance of MGA were conducted under atmospheric pressure in a swirl model combustor. The electrical characteristics of MGA were investigated under different air velocities. The ignition process of MGA was recorded by using a high-speed camera with CH* filter. Results show that the three-channel gliding arcs (3-GA) and five-channel gliding arcs (5-GA) generated more averaged power than the 1-GA under a constant air velocity. For example, the 3-GA and 5-GA generated 112.8% and 187.3% more averaged power than that of the 1-GA at 74.6 m s−1, respectively. The arc shapes of gliding arcs with different channel numbers were different and the duration time of ‘breakdown-stretching-extinguishing’ of MGA shortened. Furthermore, compared with the 1-GA, the percentage of the lean ignition limit widening of the 3-GA and 5-GA can reach 13.5% and 20.9% respectively. The frequency of re-breakdown in the discharge process using different gliding arc channel numbers is different, which can continuously inject energy into the combustor and generate the ‘flame combination’ phenomenon producing a larger flame area. The ignition process of MGA can be divided into three stages: sliding stage, flame combination stage and flame stabilization stage.