Direct Flame Research Articles

Development and Characterization of Thermal Protection Gels for Steel Pipelines Transporting Combustible Materials

Due to low costs, pipelines are commonly used for transporting hazardous substances such as combustible liquids and gasses. Currently, chemical industrial parks and gas production stations have dense pipeline networks. In the case of a pipeline leakage and subsequent fire accident, the adjacent pipelines could be directly impinged by the flame or engulfed in hot smoke, with the potential to result in a chain of accidents and catastrophic consequences. It is thus of practical importance to develop an efficient thermal protection material for pipelines. In this study, a new type of bio-based gel material was prepared for pipeline thermal protection, using guar gum (GG) as the gelling agent, sodium tetraborate (B) as the crosslinking agent and magnesium chloride (MgCl2) as the fire retardant. Firstly, orthogonal experiments were conducted to examine the gelling time of the gel and determine the optimal formulations that meet the protection requirements. Subsequently, water retention, thermal stability and the microstructure of these formulations were analyzed. Finally, the thermal protection performance of the gel formulations was evaluated under the direct impingement of flames or high-temperature smoke. The results indicated that the best performance was achieved by the formulation with GG, B and MgCl2 mass fractions of 2.5, 0.6 and 0.5 wt%, respectively. This formulation also exhibited the best water retention capacity and thermal stability. In the pipeline thermal protection experiments, this formulation achieved effective protection times of 216 s (for a 90 mm diameter) and 312 s (for a 120 mm diameter) for the lower part of the pipeline under direct flame impingement. Under high-temperature smoke impingement, this formulation also showed excellent performance. These research and findings can provide an important foundation for the further development of thermal protection materials for pipelines under fire conditions.

Integrating an urban fire model into an operational wildland fire model to simulate one dimensional wildland–urban interface fires: a parametric study

Background Wildland fires that occur near communities, in the wildland–urban interface (WUI), can inflict significant damage to urban structures. Although computational models are vital in wildfires, they often focus solely on wildland landscapes. Aim We conducted a computational study to investigate WUI fire spread, encompassing both urban and wildland landscapes. Methods We developed a 1D landscape-scale semi-physical model by integrating a semi-physical urban fire spread model into an Eulerian level set model of wildfire. The model includes ignition and spread through radiation, direct flame contact and ember deposition. Key results Through a parametric study, we compare the relative change of spread rate from various structural properties and landscape layouts represented by model parameters, highlighting the significant impact of fire-resistant structure materials over surface treatments. Layout configurations play a pivotal role in fire spread, with isolated islands of combustibles effective in reducing spread rate, aligning with existing mitigation strategies. Conclusion Despite using a 1D domain and limitations on spatial and temporal variability, our model provides insights into underlying phenomena observed in WUI fires and their mitigation. It offers early-stage development of strategies for managing structure materials and landscape layouts. Implications Our model and findings provide insights into WUI fire dynamics, paving the way for advanced mitigation strategies.

Flame-Resistant Inorganic Films by Self-Assembly of Clay Nanotubes and their Conversion to Geopolymer for CO2 Capture.

Self-assembling of very long natural clay nanotubes represents a powerful strategy to fabricate thermo-stable inorganic thin films suitable for environmental applications. In this work, self-standing films with variable thicknesses (from 60 to 300µm) are prepared by the entanglement of 20-30µm length Patch halloysite clay nanotubes (PT_Hal), which interconnect into fibrosus structures. The thickness of the films is crucial to confer specific properties like transparency, mechanical resistance, and water uptake. Despite its completely inorganic composition, the thickest nanoclay film possesses elasticity comparable with polymeric materials as evidenced by its Young's modulus (ca. 1710MPa). All PT_Hal-based films are fire resistant and stable under high temperature conditions preventing flame propagation. After their direct flame exposure, produced films do not show neither deterioration effects nor macroscopic alterations. PT_Hal films are employed as precursors for the development of functional materials by alkaline activation and thermal treatment, which generate highly porous geopolymers or ceramics with a compact morphology. Due to its high porosity, geopolymer can be promising for CO2 capture. As compared to the corresponding inorganic film, the CO2 adsorption efficiency is doubled for the halloysite geopolymeric materials highlighting their potential use as a sorbent.

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

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

Smoldering ignition and transition to flaming in wooden mulch beds exposed to firebrands under wind

Spotting ignition by firebrands is a significant fire spread pathway at the wildland-urban interface (WUI), where mulch products are commonly used as landscaping materials. Mulch is typically organic in nature, thus it may be easily ignited into a smoldering mode by firebrands and subsequently transition to flaming, leading to direct flame contact and radiant heat exposure to siding materials of adjacent structures. This work quantified the thresholds of smoldering ignition of four common types of commercially available mulch (black mulch (BM), forest floor (FF), redwood (RW), and fir bark (FB)) exposed to heating by smoldering firebrand piles, and their propensity for smoldering-to-flaming transition under external winds (up to 1.4 m/s). We found that there was a minimum mass of firebrand pile to achieve smoldering ignition of mulch (e.g., ∼0.1 g for FF). Beyond this minimum mass, the required wind speed to trigger smoldering ignition generally decreased as the mass of the firebrand pile increased, agreeing well with theoretical analysis. After smoldering ignition, smoldering-to-flaming transition could be observed when the wind speed exceeded a critical value (e.g., ∼1 m/s for FF), which was not affected by the initial spotting process. To achieve smoldering-to-flaming transition, the glowing mulch had to reach a critical temperature of around 850 °C. Mulch samples with larger particle sizes were more likely to smolder and transition to flaming, due to increased oxygen supply through larger inter-particle pores and channels and better firebrand accumulation due to a more crevice-like geometry on the fuel surface. This work advances the fundamental understanding of the ignition and burning behavior of landscaping mulches, and thus contributes to the prevention of extreme WUI fire events.

Effects of ignition methods and control parameters on the lean combustion performance and flame geometry of jet ignition based on constant-volume combustion chamber

Pre-chamber jet ignition provides one of the most reliable thermal efficiency improvement technologies for future gasoline engines, especially hybrid gasoline engines. The effects of jet ignition control parameters on the jet flame morphology and combustion characteristics are still unclear, for example, the fuel injection mass in the pre-chamber and the time interval between low-flow injection and ignition. The paper explored the effects of jet ignition stoichiometric and lean combustion performance on the flame propagation process of high-energy spark ignition, passive and active pre-chamber, using direct flame imaging in a constant-volume combustion chamber. The jet ignition performance under lean combustion conditions is further enhanced by optimizing the jet ignition control parameters. Based on the luminance characterization of the image, the active pre-chamber with additional low-flow injection can provide 281% of the ignition intensity equivalent to high-energy spark plug ignition. Increasing the fuel injection mass in the pre-chamber can improve heat release and enhance ignition performance. However, the jet ignition performance will drop sharply due to the too-rich pre-chamber gas mixture. Extending the mixing time interval after ignition will enrich the lean ambient mixture outside the pre-chamber and increase the ignition performance. Over-mixing will occur if the mixing time interval is too long, especially under a few injected fuel mass situations. The radial stretch coefficient of the jet flame is defined to characterize the flame geometry during the jet flame propagation process. The jet ignition performance reaches its best when the jet flame propagates at high speed in both radial and circumferential directions, namely a wide jet flame.

Investigating the protective performance of turnout gears for firefighters under diverse exposure conditions: Effect of age and body segments

Present work investigates the impact of different exposures (flame, 50/50 convection and radiation, and radiation alone) on thermal performance of firefighters' clothing. The protective performance is evaluated across various body segments for firefighters of different ages. Transient heat transport equations are numerically discretized using finite difference approach. The computational domain comprises of a three-layer fabric assembly, a single-layer skin, and a microclimate between the fabric and skin. Heat transfer in the porous fabric assembly results from the interaction of both conduction and incident radiation penetrating through confined hot air within the fabric. The energy equation of fabric employs a two-flux model, encompassing self-emission originating from absorbed incident radiation in the encapsulated hot air. A nonlinear bioheat transfer model, accounting for age and body segment, incorporates temperature-dependent thermal conductivity, blood perfusion rate, skin thickness, and heat generation from metabolism, shivering, and external work. Results found that first and second-degree burn durations decrease by 30.85 % and 37.92 %, 26.73 % and 29.76 %, and 24.23 % and 26.63 % for flame, 50/50 convection-radiation and pure radiation heat exposure respectively as firefighter’s age from 25 to 65 years. The protective attire excels the best for the torso against direct flame but is the least effective for shielding arms from radiant heat. Moreover, the transition time from first to second-degree burn injury decreases by 64.77 %, 65.73 %, and 66.03 % for arms, and by 70.93 %, 66.29 %, and 67.22 % for legs in flame, 50/50 convective-radiative, and purely radiant heat exposures, respectively, with a 100 % reduction in skin conductivity coefficient.

Advanced Solid Geopolymer Formulations for Refractory Applications.

Cement, as a construction material, has low thermal resistance, inherent fire resistance, and is incombustible up to a certain degree. However, the loss of its mechanical performance and spalling are its primary issues, and it thus cannot retain its performance in refractory applications. The present study explores the performance of geopolymer formulations that have excellent fire resistance properties for potential refractory applications. This study is unique, as it investigates advanced solid geopolymer formulations that need only water to activate and bind. Various solid geopolymer formulations with fly ash as a precursor; potassium hydroxide and potassium silicate as activators; and mullite and alumina as refractory aggregates were studied for their compressive strength at up to 1100 °C and compared with their two-part conventional liquid alkaline geopolymer counterparts. Advanced solid geopolymer formulations with mullite and alumina as refractory aggregates had mechanical strength values of 84 MPa and 64 MPa post-1100 °C exposure and were further exposed to ten thermal cycles of 1100 °C to study their fatigue resistance and post-exposure compressive strengths. The geopolymer sample with mullite as a refractory aggregate yielded 115.2 MPa compressive strength after the fourth cycle of exposure. This sample was also studied for its temperature distribution upon direct flame exposure. All the geopolymer formulations displayed a drop in compressive strength at 600 °C due to viscous sintering and then a rise in strength at 1100 °C due to phase transformation. X-ray diffraction studies revealed that the formation of crystalline phases such as leucite, sanidine, and annite were responsible for the superior strengths at 1100 °C for the alumina- and mullite-based geopolymer formulations.

Experimental investigation on the effects of transverse injection distribution scheme on dual flame dynamics subjected to flow disturbances

Combustion instability has become a major problem in low-emission annular gas turbine combustors. It is of practical importance to investigate the effects of transverse nozzle distribution scheme on multi-flame dynamics subjected to external acoustic perturbations. In this study, the responses of heat release rate perturbations from dual propane/air laminar premixed flames to axial acoustic perturbations have been experimentally measured. Specifically, the velocity disturbance upstream the flame base has been measured by two-microphone method and the flame heat release rate perturbation is obtained by the photomultiplier tube with CH* filter lens. The dynamic evolution of dual flames is captured by the high-speed camera and then analyzed with the proper orthogonal decomposition (POD) method. Results indicate that there is a critical distribution distance, where the peak gain of the dual flame transfer function is the largest. And the direct injection dual flame transfer function can behave as the low-pass filter. Furthermore, the dual flame transfer function behaves nonlinearly with the increase of the injection angle. The dual flame transfer function for large injection angle can behave as the hybrid mode of the low-pass filter and the band-pass filter. The POD analysis reveals that the coupling effect of gas thermal expansion and stretch effect would contribute to the interaction between dual flame front dynamics. The transverse injection distribution scheme (dual flame distance and injection angle) has a significant effect on the dual flame front dynamics, which in turn affects the flame heat release rate disturbance. The bulk mean flow velocity can enhance the interaction effect between dual flame front dynamics.

SiCf/SiC composites tolerance to high temperature combustion atmosphere and post ageing mechanical and microstructural characterisation

This article reports the activities carried out under WP4, coordinated by ENEA, within the CEM-WAVE European project, about experimental study on SiCf/SiC composites tolerance to high temperature combustion atmosphere. Water corrosion phenomena are known to affect mechanical properties of SiC-based CMC, due to the formation of a silica, volatile in certain condition. The study will simulate combustion conditions, aiming at using more environmentally friendly alternatives to methane, such as hydrogen, coke oven gas or biomethane, in steel production. It is essential to determine, in each case, if corrosion happens in active (that means continuous degradation) or passive (silica forms a protective “scale” on the component) regime. Since fibre-to-matrix interface can also be degraded, it is important to determine post-ageing mechanical flexural strength (by 4point bending tests). Water corrosion ageing was performed by means of direct flame exposure. When the oxidizing species becomes CO2, instead of O2, the formation rate of silica passivating layer is expected to be lower than the volatilization rate, and consequently active oxidation results in continuous weight loss. Ageing tests of SiCf/SiC composites were carried out at high temperature in a CO2/H2O/N2 gaseous environment at atmospheric pressure (reference conditions: 1200°C, 10/20/70 v/v). Bending tests up to failure are carried out at room temperature on these aged samples after different exposure times. Relationships are established between the evolution of mechanical properties, the ageing conditions, and the rates of oxidation reactions.

Performance, Emissions, and Decarbonization of an Industrial Gas Turbine Operated With Hydrotreated Vegetable Oil

Abstract As part of Uniper's strategy for carbon neutrality in its European power generation by 2035, a Kraftwerk Union/Siemens V93.0 gas turbine (GT) in Malmö, Sweden was operated with hydrotreated vegetable oil (HVO) as a low-carbon replacement for gas oil in July 2021. Prior to HVO operation, a feasibility study was conducted including fuel comparison, flame temperature modeling, and a hazard identification study. During the two-day demonstration, GT performance was monitored using either gas oil or HVO at startup, full load, part load, and shut-down. Accredited emissions of NOx, CO, SO2, and dust were measured to allow comparison between fuels. When firing HVO, no adverse GT operations were encountered, and direct flame imaging was used to observe the successful HVO ignition process at startup. NOx emissions were nominally similar to gas oil during HVO operation. Therefore, the water injection rate for NOx control was unchanged between fuels, confirming the predictions of the flame temperature modeling. Dust, CO, and SO2 emissions reduced during HVO operation. HVO also enables significant lifecycle CO2 emissions reductions compared with fossil gas oil with ∼163 tCO2 emissions avoided in this trial. This trial provides evidence for future site fuel conversion. Further testing and monitoring is required to develop evidence regarding the long-term impact of HVO operation on fuel storage, fuel delivery, and hot gas path components. To the authors' knowledge, this trial is the first successful demonstration of HVO use in an industrial gas turbine in the world.

Fire Performance of Reinforced Concrete Slabs: Direct Flame Effects

The behaviour of two-way reinforced-concrete slabs exposed to direct fire was investigated in this study. The slabs were exposed to fire for one hour in a gas furnace and the flame-spread area was varied by increasing the number of fire sources from three to six. The slabs were cooled in two different ways: gradual cooling and sudden cooling. The results showed that the flame-spread area had a significant effect on the load-carrying capacity and deflection of the slabs. The load-carrying capacity decreased by 20.68% with gradual cooling and by 33.78% with sudden cooling when the flame-spread area was increased. The deflection at failure increased by 26.3% with gradual cooling and by 33.78% with sudden cooling when the flame-spread area was increased. The ductility factor showed an increase of 12.6% to 50.3 % for gradually-cooled slabs and of 50.3% to 59.6% for suddenly-cooled slabs with an increasing flame-spread area, compared to reference slabs. KEYWORDS: Reinforced solid concrete slabs, Direct fire flame, Thermal flame, Cooling method.

Rehabilitation of Fire-damaged Reinforced-concrete Slabs Using Ferro-cement

his study was conducted to investigate the effect of strengthening with ferro-cement on the flexural behavior of two-way RC slabs after exposure to direct fire. Twelve reinforced-concrete slabs were exposed to direct fire for one hour and cooled with air and water. They were then rehabilitated with a layer of ferro-cement using different bonding patterns (surface roughening, SBR material and screws). The effect of these variables was studied on the load-deflection relationship, ultimate load capacity, stiffness, energy absorption, ductility factor and strains of the compressed zone. The results showed a significant improvement in all the investigated parameters, demonstrating the efficiency of ferro-cement strengthening in improving the behavior of the slabs. It contributed to increasing the ultimate load capacity and initial stiffness of the slabs and to preventing and arresting crack propagation after cracking and even after reaching collapse. The effectiveness of SBR material in ensuring the bonding between the surface of the damaged slabs and the reinforcement layer was also revealed. KEYWORDS: Solid slab, Direct fire flame, Ferro-cement, Rehabilitation, SBR (styrene-butadiene rubber), Roughing.

Measuring methane destruction efficiency in gas flares with dual comb spectroscopy

Gas flaring is used as an alternative to venting when waste gases cannot be captured from industrial processes such as oil and natural gas production, chemical processing, and waste management. In the oil and natural gas production sector alone, an estimated 3.5 % of total global natural gas production is flared. Survey studies have shown that the methane destruction efficiency (DE) of flares is lower than expected due to real-world conditions (weather and equipment malfunction) and estimate that improving flare efficiency is a 0.5 Tg/yr methane emissions reduction opportunity. Continuous monitoring of flare DE would provide the opportunity for feedback to lower emissions; however, there are currently no technologies used at scale that can provide such a measurement. Here we present a method for measuring the operational methane DE from flares by monitoring methane levels in flares using dual-frequency comb spectroscopy. This method leverages the temperature-dependent absorption fingerprint of methane to differentiate heated and ambient methane. We assess the capabilities of this technique through a set of laboratory-based experiments utilizing a partially premixed methane flame. We estimate the limit of detection (LOD) and sensitivity of the measurements for directly monitoring a flame, and monitoring a flame from a distance of 1 km in the presence of ambient methane. For our configuration, a targeted monitoring scenario (direct flame measurement) results in the ability to distinguish methane DE up to 99.9 %; whereas in the presence of a 1 km background methane signal, the approach is able to quantify methane DE to 97.5 %. These performance metrics could be improved through an updated high-temperature spectral absorption database for methane, however the current estimated performance could already substantially impact flare emissions by closing the gap between the flare design specifications and what research studies estimate from actual in-field performance.

BLENDING HYDROGEN WITH LPG AND METHANE IN PREMIXED AND STRATIFIED FLAMES: AN EXPERIMENTAL STUDY

This experimental work investigates the effects of blending hydrogen into liquefied petroleum gas (LPG)/air flames and methane/air flames under different stratified mixture conditions. A laboratory scale, a swirl-stabilized burner with two annular tubes, is used to examine the stability and structure of the flames. Fully premixed fuel-air mixture are provided through an inner and outer annulus, with equivalency ratios of φ<sub>1</sub> and φ<sub>2</sub>. Two experimental scenarios are studied to understand the hydrogen blending by mass. In the first scenario, hydrogen was introduced to replace LPG in the inner stream, while in the second scenario, hydrogen replaced LPG in the outer stream. The second scenario involves optimizing the operating conditions of the burner to achieve flame stabilization with a hydrogen blend of up to 90%. The study employs direct flame imaging and simultaneously captures OH*/CH* chemiluminescence imaging. The findings reveal that in the first scenario, a flashback occurs when hydrogen replaces LPG beyond 20% in the inner stream. However, in the second scenario, no flashback is observed even when hydrogen in the outer stream replaces up to 90% of LPG. The study also reports stable flame structures for various operating conditions using chemiluminescence imaging. These results underscore the importance of fuel blending strategies and demonstrate the potential of hydrogen as a feasible alternative fuel in combustion applications.

Forensic Investigation of Electrical Conduct Copper Bead Microstructure as an Effort to Identify Causes of Fire

The purpose of this study was to evaluate the characteristics of the bead formed due to short circuit, overload and direct flame treatment on NYM 3x1.5 copper power cable. Handling of short circuit and overload is carried out at a current load of 800% of the current carrying capacity (144 Amperes) and direct flame treatment is carried out at a temperature of 960 degrees Celsius. The bead specimens formed from each treatment were examined and tested in the laboratory: chemical composition examination, visual inspection, macro and micro structural examination, hardness testing, and SEM-EDS examination. The difference in the characteristics of the arc bead that is formed under short circuit conditions and overload is that in short circuit conditions the damage point is localized at a certain point, namely at the short circuit contact point, while under overload conditions the point damage is localized at one or several specific locations along the wire. The macro characteristic of arc beads formed under short-circuit and overload conditions is that they contain many cavities and a clear transition boundary between the melted/ re-solidified material and the non-melted material. While the characteristics of the granules in the form of globular formed in the direct flame treatment, do not show sharp transitions between melting/ re-solidified materials. The micro structure of NYM 3x1.5 beads of electrically conducting copper wire material under the treatment conditions: short circuit, overload and direct ignition, is an alpha (α) phase dendritic structure.

Quantifying Firebrand and Radiative Heat Flux Risk on Structures in Mallee/Mulga-Dominated Wildland–Urban Interface: A Physics-Based Approach

Fire spread in the Wildland–Urban Interface (WUI) can occur due to direct flame contact, convection, radiation, firebrand attack, or their combinations. Out of them, firebrand attack significantly contributes to damaging structures. To improve the resistance of buildings in wildfire-prone areas, the Australian Standards AS3959 provides construction requirements introducing Bushfire Attack Levels (BAL) based on quantified radiation heat flux. However, quantifying firebrand attack presents challenges, and the standard does not provide specific recommendations in this regard. This study aims to address this research gap by quantifying firebrand flux on houses according to the BALs in Mallee/Mulga-dominated vegetation using physics-based modelling. The study follows the AS3959 vegetation classifications and fire-weather conditions. The study considers Fire Danger Indices (FDI) of 100, 80, and 50 and identifies the housing components most susceptible to firebrand attack and radiant heat flux. The findings reveal an increasing firebrand flux with higher BAL values across all FDIs, with a greater percentage difference observed between FDIs 50 and 80 compared to FDIs 80 and 100. Furthermore, an exponential relationship is found between radiative heat flux and firebrand flux. This research contributes the development of effective strategies to mitigate the firebrand danger and enhance the resilience of structures to enhance AS3959.

Synthesis and synergistic effect of cuprous(I) oxide nanoparticles and polyethyleneimine modified ammonium polyphosphate on enhancing the flame resistance of epoxy resin

Abstract In this study, cuprous(I) oxide nanoparticles (Cu2ONPs) and APP@PEI (polyethyleneimine-modified ammonium polyphosphate) materials were successfully synthesized and combined to create a flame-retardant system for the fabrication of epoxy (EP) resin with high flame resistance. The characteristic results revealed that the synthesized Cu2ONPs exhibited a particle shape with a size below 200 nm. The synthesized APP@PEI material possessed dimensions ranging from 10–20 micrometers, featuring a core–shell structure. The combination of Cu2ONPs and APP@PEI has proven to be an effective flame-retardant system, significantly enhancing the flame resistance of EP resin. The epoxy-based composite prepared with 2 wt% Cu2ONPs and 18 wt% APP@PEI demonstrated high flame resistance, achieving a V-0 rating (the highest rating according to the UL-94 method for evaluating the flame retardancy of materials) and a limiting oxygen index value of 36% (indicating the material’s self-extinguishing ability). This limiting oxygen index value was significantly higher than that of neat EP resin, which only reached 19%. The characteristic results of the flame-retardant epoxy-based composite demonstrated that both APP@PEI and Cu2ONPs were well dispersed in the EP resin and did not undergo structural transformation during the material preparation process. APP@PEI and Cu2ONPs enhanced the thermal degradation of EP-based composite materials at lower temperatures, exhibiting a faster degradation rate compared to EP resin. This augmentation facilitates the formation of a protective char layer on the surface of composite, thereby shielding it from direct flame exposure during combustion. Cu2ONPs played a role as oxidative catalysts, acting as Lewis acids. In addition to enhancing fire resistance, APP@PEI and Cu2ONPs have increased thermal conductivity, reduced impact strength, maintained tensile strength, and improved flexural strength of the composite material based on EP compared to neat EP resin.

Enhanced photocatalytic activity of zinc oxide and tin doped zinc oxide nanoparticles synthesized by direct injection flame synthesis

Pristine zinc oxide and tin doped zinc oxide (ZnO) nanoparticles were prepared using single step rapid direct injection flame synthesis (DIFS) method and compared. The results revealed prominent changes in morphological and optical properties due to the incorporation of Sn ions into ZnO matrix and its origin was discussed. Upon doping the ZnO nanoparticles experiences change in length along the c- axis which increases the volume of the unit cell and bond length of zinc and oxygen ions. Other than that, tin doping in ZnO introduces new intrinsic defect level which decreases the electron hole recombination rate at the interface and enhances the formation of hydroxyl radicals and superoxide which further improves the photocatalytic degradation of Methylene Blue (93%) compared to pure ZnO (81%).

Experimental study of dynamics of flames from discrete methanol fuel wicks in ullages

The paper presents an experimental study of the burning characteristics of discrete methanol wicks in ullages, where the burning occurs at distances much lower than the lip of the burner. Burning configurations consisting of two methanol wicks burning in varying ullages (from zero to 24 cm at intervals of 6 cm) have been considered in the experiments. At zero and 6 cm ullages, flame shapes resemble that of a general buoyant pool flame. As the ullage is increased to 12 cm or higher, a plume-induced instability triggers in the ullage and the flame bends towards one side over the wicks, resembling a boundary layer type of flame. The transition from a pool flame to a boundary layer-type flame has been illustrated with direct flame photographs. At deeper ullages, as the flame leans over the fuel wicks, the mass burning rates are enhanced from 9% to 35% for different ullages. The resulting air flow inside the ullage and flame shape affects the mass burning rate and has been visualized using smoke flow in the ullage. This study opens further research on the coupling effect of burning of heterogeneous materials in ullages with the flow field induced by the buoyant plume.