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The reactivity of heterogeneous energetic materials (HEMs) intimately depends on the underlying microstructural effects. For reactive materials, key factors include the microstructure distribution, morphology, size scale of heterogeneities, reactant mixing, and chemical kinetics of the reactants. We report the development of a mesoscale model for simulating the evolutions of the hotspot field and associated reaction processes when such materials are exposed to external excitations. The model explicitly accounts for microstructure, interdiffusion between the reactant species, advection of the species mixture, and chemical kinetics of the reaction. An Arrhenius relation is used to capture the rate of reactive heat release. The particular material analyzed is a composite of poly(vinylidene fluoride-co-trifluoroethylene) and nanoaluminum [or P(VDF-TrFE)/nAl]. The excitation leading to the initial microstructural temperature increase that kicks off the exothermic reactive processes is the dissipative heating arising from dielectric breakdown under the electric field developed through piezoelectricity and flexoelectricity of P(VDF-TrFE). As such, the model resolves both the breakdown process and the diffusion, advection, and exothermic reaction processes. The evolutions of the temperature and species distribution fields under the combined effects of breakdown and chemistry are used to predict the effects of microstructure, diffusion, and kinetics on several key metrics characterizing the reactive responses of the material. This mesoscale framework admits the quantification of uncertainties in these predicted macroscopic behavior measures due to microstructure heterogeneity fluctuations through the use of multiple, random but statistically equivalent microstructure instantiations. Although the particular hotspot inducing mechanism considered is dielectric breakdown here, the framework can be adapted to analyze reaction initiation and propagation and establish microstructure–reaction behavior relations under other types of hotspot inducing mechanisms, such as thermomechanical inelastic dissipation, frictional heating, and laser or microwave excitation. [ABSTRACT FROM AUTHOR]

In this paper, the temperature rise in the longitudinal direction, the heat release rate (HRR), the endless area temperature under the ceiling of the utility tunnel, and the root of HRR (oil and fuel type), cable type, number of cable layers and and cables per layer. The effects of airtightness, natural ventilation, and longitudinal ventilation on the fire characteristics of cable compartments were compared. The results showed that the effects of enclosed cable tunnels and natural ventilation on fire behavior near walls in cable tunnels were compared. Compared with the natural ventilation state, when placing RVVR type cables, the fire duration of the enclosed cable compartment was shorter, the ceiling temperature rise was greater. And the time that was necessary to increase the ceiling temperature to its maximum value was shorter. The HRR inside the enclosed cable compartment was very high and could almost reach its peak quickly. The contribution of this article is to reduce the social and economic costs of utility tunnels by preventing tunnel fires. [ABSTRACT FROM AUTHOR]

There is still a disagreement on how aging affects the risk of cable fire. In order to comprehensively assess the aging effects on cable fire risks, a series of cone calorimeter tests and flame spread experiments on accelerated thermal aging PVC cables were carried out with various thermal aging time. A large amount of fire characteristics was measured, including the ignition time (TTI), heat release rate, critical heat flux, fire performance index (FPI) and fire growth index (FGI) by cone calorimeter tests, as well as flame spread and dripping behaviors by flame spread experiments. Results showed that the values of TTI, FPI and the dripping frequency are increased with thermal aging time, but the maximum heat release rate, flame spread rate, FGI are decreased. It is evidenced that the thermal aging PVC cables have lower ignition risk, heat release risk, fire growth risk, but have a higher risk of dripping and igniting surrounding combustibles. This work may provide an in-depth understanding of fire risk of thermal aging cables. [ABSTRACT FROM AUTHOR]

This study investigates the impact of Titanium Suboxide (Ti4O7) on the flame retardancy, mechanical properties, thermal stability, and electrical and thermal conductivity of silicone rubber composites. The addition of 1.0 part of Ti4O7 to the silicone rubber composites results in a total heat release (THR) of 45 MJ/m2, which is 45.7% lower than the silicone rubber without Ti4O7, leading to a decrease in the peak of heat release rate (PHRR). Furthermore, Ti4O7 exhibits temperature stability at low temperatures and acts as a physical barrier, inhibiting the early decomposition of silicone rubber and enhancing the thermal stability of the composites. However, at temperatures exceeding 450°C, the catalytic activity of Ti4O7 is activated, promoting the decomposition of the silicone rubber composites and generating more residue. The addition of an appropriate amount of Ti4O7 can further improve the mechanical properties of the silicone rubber composites and enhance their electrical and thermal conductivity. [ABSTRACT FROM AUTHOR]

The current research investigates the impact of a split fueling strategy combined with several flow rates of exhaust gas recirculation (EGR) on the combustion and emission characteristics of a diesel engine running on B20 waste cooking oil (WCO) biodiesel. A four‐stroke single‐cylinder common rail direct injection engine was employed for experiments. It operates with a B20 blend of WCO biodiesel at 600 bar pressure for varying pilot fueling conditions of 10%, 20%, and 30%. The B20 blend with 30% pilot fuel injection (B20P30) showed excellent performance and emission characteristics compared with B20 blend with 10% pilot fuel injection (B20P10) and B20 with 20% pilot fuel injection (B20P20). However, B20P30 had greater levels of nitrogen oxide (NOx) emissions than those by diesel. EGR discharge levels in 5% increments, ranging from 0% to 15% were introduced to address this issue. The experimental findings revealed that both cylinder peak pressure and heat release rate showed a reduction when the EGR flow rate was enhanced. The recirculation of exhaust gas into the combustion chamber led to a slight increase in the emission levels of hydrocarbon (HC), carbon monoxide (CO), and smoke, as well as a decrease in carbon dioxide (CO2). Nevertheless, the introduction of EGR significantly decreased NOx emissions by 22.94%, 35.05%, and 47.96% for EGR flow rates of 5%, 10%, and 15%, respectively, when compared with the engine operating without EGR. Overall, the two‐stage fueling strategy, B20P30 blended with 10% EGR corroborated to be beneficial in reducing NOx emissions with minimal performance penalties. Although there was a slight uptick in certain emissions, the overall trade‐off between emission reduction and performance was favorable. The culmination of this study is targeting the objectives of sustainable development goal 7 (clean energy) and goal 13 (climate action) to be achieved by 2030. [ABSTRACT FROM AUTHOR]

[Display omitted] Despite the advantages of easy moulding and excellent mechanical properties, there are still some shortcomings with polypropylene (PP) such as high flammability and poor ultra-violet (UV) resistance. In this work, modified zinc oxide (mZnO) was prepared by reacting zinc oxide nanoparticles (ZnO) with polysiloxanes, and the effect of mZnO on the effectiveness of intumescent flame-retardant and on the UV aging resistance of polypropylene were investigated. By introducing 16 wt% (intumescent flame-retardant /mZnO) and 0.3 wt% maleic anhydride-grafted PP (MAH-g-PP), the limiting oxygen index increased to 32.7 %, and passed UL-94V-0 rating. In comparison to the controls, the peak heat release rate and the peak smoke release rate were 88.5 % and 80 % lower, respectively. In addition, PP samples showed improved mechanical properties, with a 5 % increase in tensile properties compared to the pure PP sample. After 100 h of UV irradiation, the surface of the samples was relatively flat and smooth, and the carbonyl index decreased from 81.1 of neat PP to 26.7. PP composites with 100 h aging treatment still had excellent flame retardancy and mechanical properties. The results showed that mZnO was effective in improving the flame retardancy, mechanical properties and light aging tolerance of PP. This study provides a novel approach to fabricate long-life flame-retardant PP composites with low additive content. [ABSTRACT FROM AUTHOR]

In this paper, flame retardant composites were prepared by incorporating three flame retardants (FRs), including triphenyl phosphate (TPP), polysiloxane (PSQ) and phosphite functionalized polysiloxane (PPSQ), respectively into a polylactic acid (s/PLLA) matrix. The results indicated that the ultimate oxygen index increased from 20.6% (s/PLLA) to 22.5% (s/PLLA/TPP), 21.1% (s/PLLA/PSQ), and 23.3% (s/PLLA/PPSQ). The composites exhibited a decrease in peak heat release rate (pHRR) and prolonged peak time according to the cone calorimetry analysis. s/PLLA/PPSQ possessed the highest residual carbon content and the densest char residue with finest and smallest pores, indicating excellent flame-retardant performance. The crystallization behavior analysis revealed that the three FRs resulted in an increased crystallization rate and crystallinity. Notably, the crystallinity of s/PLLA/PPSQ increased from 25.8% in s/PLLA to 37.3%. Additionally, PSQ and PPSQ effectively enhanced the mechanical properties of composite materials. Compared to s/PLLA, the tensile strength of s/PLLA/PSQ and s/PLLA/PPSQ increased by 11.5% and 31.3% respectively, and storage modulus increased by 50.0% and 14.6%. This research demonstrated that among the three additives, PPSQ can effectively provide both flame retardancy and mechanical properties to the s/PLLA matrix, resulting in the composite with the best comprehensive performance. [ABSTRACT FROM AUTHOR]

To investigate the flame propagation characteristics and chemical kinetics of premixed propane/hydrogen/air mixtures at elevated pressure, a series of experiments on propane/hydrogen/air mixtures with varying initial pressures (P 0 = 100–300 kPa) and equivalence ratios (φ = 0.6–1.4) at a hydrogen fraction of 0.6 and an ambient temperature of 298 K were carried out in a closed duct with an aspect ratio of 15. The chemical kinetics of the elementary reaction were analyzed numerically. The results revealed that the combustion-induced rapid phase transition (cRPT) occurred in the premixed C 3 H 8 /H 2 /air flames. Both the combustion pressure and flame propagation velocity increase with initial pressure except at P 0 = 300 kPa, where the flame propagation velocity decreases. Moreover, the linear dependence between the laminar burning velocity and peak mole fraction [H + O + OH] max was found by the effect of initial pressure on the peak mole fraction (H, O, OH). The explosion pressure P rea and the maximum rate of production of free radical H/O show excellent correlations. The maximum rate of pressure rise can be predicted by the maximum heat release rate (HHR). These results provide essential data on elevated-pressure duct accidents and have important implications for explosion prevention. • C 3 H 8 /H 2 /air flames at elevated pressure in a closed duct were investigated. • Combustion-induced rapid phase transition was observed in C 3 H 8 /H 2 /air flames. • An equation is established for combustion pressure with peak rate of H production. • A relationship between explosion parameters and fundamental parameters are found. [ABSTRACT FROM AUTHOR]

The hydrogen carrier ammonia is considered a prominent carbon-free alternative fuel. This paper examines the impact of flue gas recirculation (FR) on combustion instability and emission behavior of premixed CH 4 /NH 3 /air swirl flame at different equivalence ratios (Φ) and ammonia mole fractions (χ NH 3 ). Experimental results show that FR is beneficial to suppressing the self-excited pulsating pressure and pulsating heat release rate of CH 4 /NH 3 /air flame, and the pulsating frequency decreases monotonically with the increase of FR. Under fuel-lean and stoichiometric conditions, FR is beneficial to suppressing NOx formation but will increase CO and NH 3 emissions. Under fuel-rich conditions, FR reduces CO emissions but increases NOx emissions. The NO emissions obtained from the chemical reactor network simulation are in qualitative agreement with the experimental results. The results show that the elementary reactions related to HNO and NHi radicals play a crucial role in the influence of FR on NO formation. • Flue gas recirculation (FR) suppresses combustion instability of CH 4 /NH 3 /air flame. • FR decreases NOx emission but increases CO emission under non-rich conditions. • FR increases NOx emission but decreases CO emission under fuel-rich conditions. • Chemical reactor network reveals the main reactions of FR affecting NO formation. [ABSTRACT FROM AUTHOR]

This study investigated the effect of the H 2 fraction on reaction dynamics and NO x formation in a premixed NH 3 /H 2 /air jet flame within a hot coflow (JHC) through numerical simulations. We found that even a small mole fraction of H 2 (e.g., X H2, F = 5%) significantly enhances the ignition of the premixed NH 3 /air flame. However, the presence of H 2 markedly intensifies the main combustion reactions only when X H2, F ≥ 30%, resulting in a sharp increase in temperature and heat release rate. Moreover, as X H2, F increases, the NO x emission first increases until X H2, F = 75% and then decreases. Without any H 2 addition, a high emission of unburned NH 3 occurs in the pure NH 3 JHC flame. On the other hand, when X H2, F ≥ 50%, the emissions of unburned H 2 and OH increase rapidly due to extremely high temperatures. Notably, maintaining X H2, F between 5% and 20% minimizes the emissions of NO x , NH 3 , H 2 , and OH. Furthermore, the preferential diffusion of H 2 plays a key role in enhancing the production of active radicals (OH, O, and H), thereby significantly boosting the initiation and combustion reactions of NH 3 /H 2 blended fuel. [Display omitted] • Effect of H 2 addition on the premixed NH 3 /H 2 /air jet flames is investigated. • A small amount of H 2 (5%) in the fuel notably enhances the ignition of NH 3 flame. • H 2 significantly boosts major combustion reactions only when its proportion ≥30%. • Optimal H 2 proportion is 5%–20% to reduce emissions of NO x , unburned NH 3 and H 2. • Preferential diffusion of H 2 greatly enhances the ignition and combustion reactions. [ABSTRACT FROM AUTHOR]

Hydrogen's wide flammability range causes its high-pressure jet flames to exhibit large-scale, high-temperature characteristics, posing risks of casualties and property damage. This study investigates the impact of different nozzle shapes and release pressures on flame behavior and temperature distribution through high-pressure hydrogen jet flame experiments. Circular outlets (0.5–4 mm diameter) and rectangular outlets (aspect ratios 1 to 8) are used, covering release pressures from 20 to 220 bar. High-pressure hydrogen is released through a nozzle into ambient air, igniting to form a flame. Flame length, width, and axial temperature are measured. Findings indicate that visible flame size increases with release pressure. The models for dimensionless visible flame length and width, considering the dimensionless heat release rate, are proposed for different nozzle shapes. Additionally, the dimensionless temperature rise along the flame axis is observed to be a function of the dimensionless distance and dimensionless heat release rate. • The hydrogen jet flame length and width varied regularly with the outlet shape. • The model of the flame length and width at rectangular outlets was proposed. • The flame temperature varied regularly with the outlet pressure, area and shape. • The model of the flame temperature distribution at circular outlets was proposed. • The model of the flame temperature distribution at rectangular outlets was proposed. [ABSTRACT FROM AUTHOR]

When aiming to cut down on the emission of nitric oxides by gas turbine engines, it is advantageous to have them operate at low combustion temperatures. This is achieved by lean premixed combustion. Although lean premixed combustion is a proven and promising technology, it is also very sensitive to thermoacoustic instabilities. These instabilities occur due to a coupling between the unsteady heat release rate of the flame and the acoustic field inside the combustion chamber. In this paper, this coupling is investigated in detail. Two acoustic design parameters of a swirl-stabilized pressurized preheated air (300 °C)/natural gas combustor are varied, and the occurrence of thermoacoustic limit cycle oscillations is explored. The sensitivity of the acoustic field as a function of combustion chamber length (0.9 m to 1.8 m) and reflection coefficient (0.7 and 0.9) at the exit of the combustor is investigated first using a hybrid numerical and analytical approach. ANSYS CFX is used for Unsteady Reynolds Averaged Navier-Stokes (URANS) numerical simulations, and a one-dimensional acoustic network model is used for the analytical investigation. Subsequently, the effects of a change in the reflection coefficient are validated on a pressurized combustor test rig at 125 kW and 1.5 bar. With the change in reflection coefficient, the combustor switched to limit cycle oscillation as predicted, and reached a sound pressure level of 150 dB. [ABSTRACT FROM AUTHOR]

It is imperative to develop efficient flame retardants to solve the issues of high heat and smoke release for epoxy resin (EP) polymeric materials plagued over time. Hence, a phosphorus–nitrogen modified Ti3C2Tx MXene nanohybrids (MXene@MPA) were synthesized by in situ assembly melamine phytate macromolecules (MPA) to boost the fire hazards of EP composites. The introduction of MPA improved the dispersion of MXene in epoxy matrix, contributing to the improved thermal stability and flame-retardant properties for EP composites. With the addition of 2 mass% MXene@MPA, EP composites achieved the decreased maximum mass loss rate (MLRmax) by 41.8%, indicating the enhanced thermal properties. Also, the peak heat release rate (PHRR) and peak smoke production rate (PSPR) of EP-MXene@MPA composites were down by 27.9% and 43.6% compared to pure EP, respectively, accompanied by significantly increased char production. The synergistic effects between MPA and MXene contributed to the elevated fire safety of EP-MXene@MPA composites: the catalytic charring of transition metals and phosphorus-containing acid and the barrier effect of MXene nanosheets, as well as the quenching effects of phosphorus–oxygen free radicals and dilution of nitrogen-containing inert gases due to the decomposition of MPA. The multiple hybridization route provided a reference for the development of efficient MXene-based flame retardants. [ABSTRACT FROM AUTHOR]

Microalgae biofuel has gained notoriety as a third-generation renewable fuel due to its high yield, rapid growth rate, and capability to absorb CO2. The current study provides insights into the combustion, performance and emission characteristics of neat algae oil and biodiesel from the Chlorella vulgaris microalgae as an alternative fuel source for compression ignition (CI) engine in comparison with diesel. In addition, elemental analysis and fuel characterisation studies of Chlorella vulgaris methyl ester (CVME) algae with GC–MS, FTIR, and UV–Vis are accorded. The spectral studies of CVME algae confess the existence of (C–H) along with (C–O), (C=O), (O–CH3), etc. Further, the spectral study of CVME algae with GCMS imposes the presence of methyl oleate as a significant constituent and the chemical structure of algae biofuel is C19H36O2. Conversely, the elemental compositions of CVME algae with a CHN analyser illustrate the existence of carbon, hydrogen and oxygen in the proportions of 66.80%, 11.80%, and 21.40%, respectively. The BTE of the engine fuelled with CVME shows a closer resemblance with diesel, whereas the NCVO deteriorates owing to its higher viscosity. Regardless, the combustion phenomenon such as ignition delay period, in-cylinder pressure, combustion duration and heat release rate (HRR) of NCVO and CVME are significantly lower at maximum load conditions in comparison with diesel. However, the emissions of carbon monoxide (CO), unburned hydrocarbons (UBHC) and smoke are lesser with diesel than NCVO and CVME. In contrast, the emissions of nitrous oxide (NOx) are higher for CVME compared to diesel and NCVO. [ABSTRACT FROM AUTHOR]

This study presented the development of a reaction kinetics scheme based on saturates–aromatics–resins–asphaltenes (SARA) fractions to represent the complicated chemical reactions occurring during high-pressure differential scanning calorimetry (HP-DSC) tests. The heat release characteristics during heavy crude oil combustion were analyzed from a set of HP-DSC results. On the basis of this analysis, an improved reaction kinetics model, including low-temperature oxidation (LTO) reactions of SARA fractions, cracking of oxidized asphaltenes, and coke combustion, was established. Following that, this model was incorporated into Computer Modeling Group STARS to simulate the HP-DSC results. Both activation energy and frequency factor of each reaction were continuously tuned until the correct kinetics parameters were obtained by matching the simulation data with the HP-DSC experimental data. The experimental results indicated that the heavy crude oil experienced greater heat release due to LTO rather than high-temperature oxidation at 5 MPa, which differed from the results observed at atmospheric pressure. The simulation results showed that the energy required to activate the oxidation reactions in the HP-DSC experiments was similar to that in the numerical simulation. However, the oil sample was subjected to higher molecular collision frequency in the HP-DSC experiments than in the numerical simulation. Therefore, more attention should be given to adjusting frequency factor when determining the oxidation kinetics parameters in the numerical model. Overall, the SARA-based oxidation kinetics model successfully simulated the exothermic characteristics of the heavy oil during heating. [ABSTRACT FROM AUTHOR]

Experiments were carried out in an optical engine, and the effects of hydrogen ratio on the combustion process of diesel/methane/hydrogen triple fuel combustion with 5% diesel fuel ratio were studied. The natural photometric images of the combustion process were recorded by a high-speed camera. Combined with the optical experimental results, the combustion process of methane and hydrogen mixture ignited by trace diesel oil was simulated. The development process of in-cylinder temperature, OH group and combustion components during combustion with different hydrogen ratios was studied. It is found that the increase of hydrogen ratio promoted the combustion, the ignition delay time and combustion duration were significantly reduced, and the heat release stage of combustion was also advanced. When the second derivative of the heat release rate is the largest, a low temperature ignition point is formed at the edge of the cylinder at first, and the flame expands with the increase of temperature in a short time. With the increase of intake pressure, the ignition delay period decreases at the same hydrogen ratio. High hydrogen ratio leads to more NOx emissions due to higher combustion temperature, and CO and CH4 emissions decrease with the increase of hydrogen ratio. • The combustion characteristics of hydrogen, methane and diesel mixture were studied. • The ignition strategy uses 5% trace diesel oil as the ignition fuel. • The combustion data are interpreted by optical visualization. • Higher hydrogen ratio can reduce ignition delay time and combustion duration. • Appropriately increase the proportion of hydrogen to reduce CO and methane emissions. [ABSTRACT FROM AUTHOR]

The classical approach to use hydrogen as a fuel for Internal Combustion Engines (ICEs) is premixed combustion. In order to avoid knocking and to limit NO x emissions, very lean mixtures are employed, thus resulting in a high boost pressure demand or low specific engine power. To overcome these limitations, the possibility of a diesel-like jet-guided combustion of hydrogen is explored. The approach is to ignite a directly injected hydrogen jet at its periphery by means of a conventional spark discharge, followed by a diffusion-controlled combustion while injection remains active. An optically accessible Rapid Compression Expansion Machine (RCEM) is used to investigate ignition and combustion of underexpanded hydrogen jets in air by means of simultaneous Schlieren visualization and OH chemiluminescence. Different injection and ignition timing are investigated, resulting in premixed, partially premixed and diffusion-controlled (jet-guided) combustion conditions. The possibility of ignition and combustion of the hydrogen jets in diffusion-controlled conditions is investigated for different orientations of the incoming fuel jet with respect to spark location. The combustion tests are analyzed in terms of ignition success rate, ignition delay, reacting surface and heat release rate, and an optimal orientation of the jet is assessed. The present study provides insights for optimizing hydrogen direct injection ignition and combustion for later application in ICEs. • The possibility of a diesel-like jet-guided combustion of hydrogen is explored. • Different timing of injection and ignition are investigated. • Hydrogen jet-guided combustion is successfully demonstrated. • Insights are obtained for optimizing hydrogen DI ignition and combustion in ICEs. [ABSTRACT FROM AUTHOR]

Due to the difficulty of absorbing viscous crude oil, there is an urgent need for carbon sponges with excellent photothermal properties and oil‐water separation capabilities to reduce viscosity and facilitate oil absorption. However, the preparation of high‐temperature carbonization leads to poor mechanical properties, low absorption capacity, and stringent preparation conditions. To solve these challenges, a highly hydrophobic flame‐retardant melamine sponge (CPBA@CMS) is designed by assembling sponge at the interface of cobalt–iron Prussian blue (CoFe‐PBA) derived from metal–organic frameworks (MOFs) and conducting low‐temperature catalytic carbonization under nitrogen. The results demonstrate that CPBA@CMS exhibits excellent superhydrophobic properties (water contact angle = 169.7°) and oil absorption capacity (80.7–219.5 g g−1). Furthermore, CPBA@CMS displays remarkable photothermal effects and thermal conductivity, making it adaptable to various environmental conditions. It can rapidly rise to 141 °C under 1 kW m−2 solar irradiation, with the maximum oil absorption rate reaching 98% and the highest oil absorption capacity at 105.5 g g−1. Additionally, CPBA@CMS shows significant fire safety performance, reducing heat release rate by 84.2%, smoke factor by 97.5%, and CO release rate by 81.4%, respectively. It provides an efficient, safe, and sustainable practical solution for effectively addressing spills of crude oil. [ABSTRACT FROM AUTHOR]

The Diesel engine is expected to be available for operation at high altitude. However, power loss and emission deterioration have been plaguing highland Diesel engines. Therefore, this study aimed to investigate the impact of altitude on the performance and combustion characteristics of Diesel engines that is limited discussed in existing studies. The research was conducted by varying the altitude from 0-4500 m using a research Diesel engine and analyzing the combustion characteristics at different combustion phases with the help of triple Wiebe function. The results indicated a noticeable drop in power output with increasing altitude, and the deterioration of performance and emissions became significant when the altitude exceeded 3000 m. Specifically, the indicated specific CO, unburned hydrocarbon, and soot emissions increased while nitrogen NOx showed a reverse trend. Additionally, it was found that the lower cylinder pressure at high altitude extended the ignition delay and caused a higher heat release rate in the premixed combustion stage. Moreover, the high altitude condition shortened the duration of combustion and reduced the energy release fraction in the diffusion phase. Furthermore, the late combustion phase occurred earlier and lasted longer at high altitude, which consequently reduced the combustion and thermal efficiency. The most important finding is that the engine performance, especially the combustion efficiency, shows an abrupt degradation with altitudes above 3000 m. As a result, engines operating at extremely high altitudes require multi-stage turbocharging to compensate for combustion deterioration. [ABSTRACT FROM AUTHOR]

The urban utility tunnel is an indispensable part of modern engineering construction. However, the fire risk cannot be ignored due to the narrow space and limited ventilation of the utility tunnel. A study of smoke filling is performed in a 1/8-scaled utility tunnel (25 m × 0.5 m × 0.45 m). Five heat release rates (5, 10, 15, 20 and 25 kW) and four positions of fire sources are used for tests. The initial position of the one-dimensional smoke movement of strong plume is determined. Based on the traditional model, the longitudinal temperature attenuation model of tunnel smoke is established with consideration of radiation and convection heat losses. The theoretical value of the longitudinal temperature rise of smoke is in good agreement with the experimental value. A one-dimensional spreading velocity model is established that coincides well with the experimental value, and the relative error is less than 20%. The spreading velocity of smoke is increased by the heat release rate. The velocity of the smoke spreading at the near end is smaller than that at the center, due to the long spreading route. The current conclusions disclosed in this study provide important guidance for the ventilation design of utility tunnels for fire smoke scenarios. [ABSTRACT FROM AUTHOR]

In South Korea, the need to link fire and evacuation simulations to compare the available safety egress time (ASET) and required safety egress time (RSET) in real time when implementing performance-based design in buildings is increasing. Accordingly, the Consolidated Model of Fire Growth and Smoke Transport (CFAST) has been discussed as an alternative to the fire dynamics simulator, which requires high computational costs, sufficient experience in fire dynamics numerical calculations, and various input parameters and faces limitations in integration with evacuation simulations. A method for establishing a reasonable computational domain to predict the activation times of smoke and heat detectors has been proposed. This study examined the validity of using CFAST to predict factors relevant to the ASET evaluation. The results showed that CFAST, which solved empirical correlations based on heat release rates, predicted high gas temperatures similarly. Moreover, the applicability of the visibility distance calculation method using smoke concentration outputs from CFAST was examined. The results suggest that despite the limitations of the zone model, CFAST can produce reasonable ASET results. These results are expected to enhance the usability of CFAST in terms of understanding general fire engineering technology and simple fire dynamics trends. [ABSTRACT FROM AUTHOR]

Research on knocking combustion is vitally essential since it impacts engine performance regarding noise and emissions, fuel consumption, power density, and durability. Because of end-gas auto-ignition, current SI engines may experience conventional knock, which restricts increasing the compression ratio to increase thermal efficiency. Therefore, this paper examined the in-cylinder pressure and vibration of a port fuel-injected gasoline engine under knocking and non-knocking conditions. The heat release rate was calculated from pressure traces where the crank angle resolutions were not constant, and the conversion from the time domain to the frequency domain of knock sensor signals by using the Fourier Transform was performed. The result reveals that more heat is released during knocking combustion than during non-knocking combustion. When there is a knock, the temperature variation increases. This would facilitate the use of heat transfer studies to detect knock occurrences. Moreover, knocking is caused by an ignition timing that is too advanced, 22°BTC, compared to the non-knocking spark case, 14°BTC. In the frequency domain, the amplitude of the knocking combustion is higher than the amplitude of the non-knocking combustion, indicating the engine’s noise and vibration. [ABSTRACT FROM AUTHOR]

To meet the environmental protection and flame retardancy requirements for epoxy resins (EPs) in certain fields, in this study, a novel triazine-ring-containing DOPO-derived compound (VDPD), derived from vanillin, 2,4-Diamino-6-phenyl-1,3,5-triazine, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), was synthesized using a one-pot method. Flame-retardant epoxy resin (FREP) was prepared by adding various ratios of VDPD to EP and curing with 4,4-diaminodiphenylmethane (DDM). The curing behavior, thermal stability, mechanical properties, and flame-retardant properties of the FREP were examined in various tests. According to the results, when the amount of VDPD added to the EP increased, the glass transition temperature of the FREP decreased linearly, and the flame-retardant properties gradually improved. With a 0.4 wt.% P content, the vertical burning rating of EP/DDM/VDPD-0.4 (according to the theoretical content of VDPD) reached the V-0 level, and the LOI value reached 33.1%. In addition, the results of a CCT showed that the peak heat release rate (PHRR) of EP/DDM/VDPD-0.4 decreased by 32% in comparison with that of the EP. Furthermore, compared with those of the EP, the tensile strength of EP/DDM/VDPD-0.4 decreased from 80.2 MPa to 74.3 MPa, only decreasing by 6 MPa, and the tensile modulus increased. Overall, VDPD can maintain the mechanical properties of EP and effectively improve its flame-retardant properties. [ABSTRACT FROM AUTHOR]

This paper tackles the influence of the functionalization of polystyrene and graphene oxide (GO) composites on the flammability characteristics. A microscale combustion calorimeter (MCC) was used to experimentally determine the heat release capacity (HRC), the specific heat release rate (HRR) and the total heat released (THR). Neural models were designed that correlate the THR with a number of parameters related to the composition and type of flame retardant used, the heating rate, the amount of residue, the HRC, the peak heat release rate (PHRR), the temperature at the peak pyrolysis rate (TPHRR) and the time elapsed until the occurrence of the peak heat release rate (Time). The best results in the training, validation and testing stages were achieved with the neural model with 9 neurons in the input layer, 40 neurons in the hidden layer and one neuron in the output layer. This model was incorporated into an optimization procedure, based on a genetic algorithm, to establish the values of the input parameters used in the training of the neural networks, in order to generate a minimum THR value, which is the output parameter. Since the synthesis of polystyrene particles with different GO concentrations is costly, this research helps to reduce the number of experimental tests and allows to determine the best GO concentration by means of neural models and genetic algorithms. [ABSTRACT FROM AUTHOR]

The aluminum combustion significantly affects the stability of solid rocket motors (SRM). In this study, the influence of aluminum combustion on the damping of SRM was investigated using the pulse decay method. Initially, the accuracy of the numerical method was validated using a theoretical model, followed by an analysis of the grid and monitoring locations for their independence. Subsequently, the flow field of SRM using propellants with and without aluminum were compared, and the oscillation attenuation coefficients for both cases were obtained. Finally, the damping of the motor system was computed for various aluminum particle sizes and concentrations. It is shown that aluminum combustion increases the temperature of the combustion chamber from 2970 K to 3500 K. This increase results in heightened gas-phase and nozzle damping, leading to faster oscillation attenuation. The aluminum oxide particles formed by aluminum combustion (30 μm) introduce particle damping, which far exceeds the unstable gain caused by heat release rate (HRR) fluctuations by about 13 times. Therefore, aluminum continues to play a crucial damping role in the instability of SRM. When the frequency is fixed, there exists an optimal particle size that maximizes the damping effect of aluminum, and the particle damping increases as the aluminum content rises. Hence, for a specific motor model, selecting the appropriate diameter and aluminum content of particles can effectively suppress the occurrence of instability phenomena. • The comprehensive effect of Al on SRM combustion instability is studied. • A numerical calculation method of SRM two-phase flow including Al combustion is established. • The gain and damping effects caused by aluminum particles are analyzed in detail. • The particle damping is far larger than the gain caused by aluminum combustion. • Effect of Al particle size and content on SRM combustion instability are studied. [ABSTRACT FROM AUTHOR]

The first step in current methodologies for the (probabilistic) performance-based fire safety design and assessment of structures is characterizing fire hazard scenario(s). Next, structural response analysis is performed to estimate hazard consequences in terms of damage or loss metrics of interest. These metrics are eventually appraised to verify whether various performance objectives are achieved and design iterations are needed. Nevertheless, such approaches rely on preliminary assumptions on the structural configuration and features characterizing scenarios used as thermal inputs. Consequently, they do not fully exploit the fire–structure coupling effect, where fire affects a structure, and the characteristics of the structure also affect the combustion process and fire dynamics. Indeed, the structural design choices define the fire scenarios that could potentially affect the structural and nonstructural performance. This paper introduces a consequence-oriented fire intensity optimization (CFO) approach to the fire safety design of structures to address such limitations. The proposed approach considers fire scenarios as additional design variables and delivers them as procedure outputs, optimizing the balance between increasing structural capacity and decreasing fire intensity. Furthermore, it evaluates the effect of input uncertainties through Monte Carlo sampling. A single-span bridge subject to a car fire is used to showcase the proposed approach. For this case study, it is shown that fire scenario characteristics (fuel bed and traffic load positions, heat release rate history) maximizing consequences are strongly correlated to the structural features and cannot be set a priori. Finally, design decisions exploiting the described coupling effect to achieve various performance objectives are discussed. Overall, the proposed approach highlights the benefits of enhancing the fire and heat transfer model's capability to capture the fire–structure coupling effect for achieving more optimized design solutions. [ABSTRACT FROM AUTHOR]

In this research, we conducted an experimental analysis of a Kerosene/air burner designed according to the FAA's proposed ISO 2685 standard. The burner serves as a vital tool for generating flames and burnt gases, simulating real-world conditions relevant to fire safety studies. The core objective of this study was to comprehensively characterize the burner's behavior. Through a series of experiments, we investigated the influence of the equivalence ratio on several key parameters, including the spatial distribution of gas temperature (monitored using thermocouples), heat flux (measured with heat flux gauges), and the composition of gas emission species. Notably, our findings revealed a significant correlation between the equivalence ratio and these parameters. Specifically, we observed that as the equivalence ratio increased, so did the flame temperature, heat flux, and heat release rate. This increase continued until a critical equivalence ratio value of 1.03 was reached, resulting in a flame temperature of 1101.5°C and a heat flux of 140 kW/m2. Furthermore, our study encompassed a pyrolysis test on various composite materials, including Carbon-phenolic, Carbon-BMI, and Carbon-PEKK. The comparative analysis of these materials highlighted the superiority of Carbon-PEKK, which exhibited the lowest mass loss, the highest back-face temperature without experiencing significant material delamination, and the lowest concentration of gas emission species. Importantly, our investigation also delved into the influence of the equivalence ratio on the flow's turbulence characteristics, a critical factor in comprehending the burner's performance and its interactions with materials in the context of fire safety scenarios. These findings contribute to a better understanding of combustion dynamics, which is invaluable for enhancing fire safety measures and developing more efficient flame-generating systems. [ABSTRACT FROM AUTHOR]

The reactivity-controlled compression ignition (RCCI) engines fueled with polyoxymethylene dimethyl ethers (PODE n) and hydrogen (H 2) demonstrate great potential in enhancing engine performance because of the beneficial fuel properties of PODE n. This study comprehensively investigates the performance of H 2 /PODE n RCCI at medium load with the gross indicated mean effective pressure of roughly 6 bar in a single-cylinder light-duty compression-ignition engine. The results showed that H 2 /PODE n RCCI has a more retarded ignition timing than that of H 2 /diesel RCCI under the same premixed energy ratio because the higher heat of absorption of PODE n reduces the bulk-gas temperature during the evaporation process owing to its higher latent heat of vaporization and lower heating value. Moreover, the combustion of H 2 shifts from flame propagation in H 2 /diesel RCCI to spontaneous auto-ignition dominated by the reactivity stratification in H 2 /PODE n RCCI, because the higher fuel reactivity and greater volatility of PODE n enhance the mixing of direct-injection PODE n and premixed H 2 , and promote the auto-ignition reactivity of the H 2 /air mixture. Overall, H 2 /PODE n RCCI exhibits a greater advantage in the ignition control than H 2 /diesel RCCI to achieve successive ignition and reduce heat release rate due to its higher sensitivity of combustion to fuel reactivity gradient. Based on this benefit, H 2 /PODE n RCCI considerably improves engine thermal efficiency and simultaneously reduces peak pressure rise rate and soot emissions, in particular realizing an order of magnitude decrease in nitrogen oxides emissions compared to H 2 /diesel RCCI. [Display omitted] • The combustion characteristics of H 2 /PODE n RCCI were extensively investigated. • The auto-ignition/flame propagation mechanism for H 2 combustion was identified. • The H 2 combustion in H 2 /PODE n RCCI is governed by multi-point auto-ignition. • H 2 /PODE n RCCI is able to significantly enhance thermal efficiency. • H 2 /PODE n RCCI can substantially reduce NO x emissions. [ABSTRACT FROM AUTHOR]

High fluctuations in the combustion process from one cycle to another, referred to as cycle-by-cycle variations, can have adverse effects on internal combustion engine performances, particularly in spark ignition (SI) engines. These effects encompass incomplete combustion, the potential for misfires, and adverse impacts on fuel economy. Furthermore, the cycle-by-cycle variations can also affect a vehicle's drivability and overall comfort, especially when operating under lean-burn conditions. Although many cycle-by-cycle analyses have been investigated extensively in the past, there is limited in-depth knowledge available regarding the causes of cycle-by-cycle (CbC) variations in hydrogen lean-burn SI engines. Trying to contribute to this topic, the current study presents a comprehensive analysis of the CbC variations based on the cylinder pressure data. The study was carried out employing a hydrogen single-cylinder research SI engine. The experiments were performed by varying more than fifty operating conditions including the variations in lambda, spark advance, boost pressure, and exhaust gas recirculation, however, the load and speed were kept constant throughout the experimental campaign. The results indicate that pressure exhibits significant variations during the combustion process and minor variations during non-combustion processes. In the period from the inlet valve close till the start of combustion, pressure exhibits the least variations. The coefficient of variation of pressure (COV P) curve depicts three important points in H2-ICE as well: global minima, global maxima, and second local minima. The magnitude of the COV P curve changes across all the operating conditions, however, the shape of the COV P curve remains unchanged across all the operating conditions, indicating its independence from the operating condition in an H2-ICE. This study presents an alternative approach for a quick combustion analysis of hydrogen engines. Without the need for more complex methodologies like heat release rate analysis, the presented cylinder pressure cycle-by-cycle analysis enables a quick and precise identification of primary combustion features (start of combustion, center of combustion, end of combustion, and operation condition stability). Additionally, the engine control unit could implement these procedures to automatically adjust cycle-by-cycle variations, therefore increasing engine efficiency. • Pressure exhibits significant variations during the combustion process and minor variations during non-combustion processes. • In the period from the inlet valve close till the start of combustion, pressure exhibits the least variations. • The magnitude of the COV P curve changes across all the operating conditions. • The shape of the COV P curve remains unchanged across all the operating conditions. • The presented cylinder pressure cycle-by-cycle analysis allows fast and accurate detection of the main combustion features. [ABSTRACT FROM AUTHOR]

The structure and thermoacoustic instability (TI) of premixed CH 4 /H 2 /air swirling flames were experimentally investigated for a range of hydrogen fraction (η H2) up to 80% under different equivalence ratio (Φ) and swirl number (S) conditions. It is shown that the onset of TI is enhanced when increasing either η H2 , S , or Φ. The dominant frequency of TI increases dramatically with η H2. The higher dominant frequency in the hydrogen-enriched flames can be attributed to a shorter flame length which results in a reduced flame convection time. It is observed that the unstable flames are always accompanied by the appearance of outer recirculation zone (ORZ) flame. Therefore, the flame kernel residing in the ORZ can be an indicator of the occurrence of TI. The flame front of thermoacoustic unstable flames was observed to be more wrinkled, e.g., with larger mean absolute curvature (κ abs) and local flame surface area ratio (δ Σ max). Importantly, the phase-locked analysis shows that κ abs and δ Σ max can be modified at different oscillation phases, and their maximum and minimum values are simultaneously achieved at phase angles θ of about 0° and 180°, respectively. Variations of κ abs and δ Σ max are in phase with the heat release rate, indicating a strong correlation between the TI and flame structure modification; however, they show a phase lag of about 72° behind the pressure in this work. These results are vital when understanding and predicting the TI based on the flame structure, especially when adopting a visual detection method of the instability. [Display omitted] • Thermoacoustic instability of swirling lean premixed CH 4 /H 2 /air flames is studied. • The dominant frequency increases significantly with hydrogen fraction. • Appearance of the ORZ flame is highly related to the instability. • The flame front is more wrinkled in unstable flames. • Flame curvature and surface area oscillate in phase with heat release rate. [ABSTRACT FROM AUTHOR]

With a numerical method, the discharging process within a container with a double complex cold surface has been scrutinized in this paper. The inherent process makes conduction as the main mechanism and the temperature equation includes three terms and two of them are time-dependent which was discretized by means of implicit technique. Adding nanoparticles within water can enhance the rate of heat release and concentration of powders and their shapes can affect the properties of nanomaterial. Single phases for estimating the features of nanomaterial were applied. The maximum period of process takes 326.95 s which is 1.36 times lower than the case of pure water. Increasing the shape factor can enhance the speed of process and its impact is less than concentration of additives. [ABSTRACT FROM AUTHOR]

In response to the problems of high mass and high thermal resistance in traditional cold plate collectors, the author proposes a shaped and efficient micro-channel collector structure design for non-normal temperature control scenarios such as high power, multiple heat sources, and highly non-uniform power density. The author conducted numerical and experimental studies on the laminar heat transfer in a highly efficient micro-channel shaped collector for non-normal temperature control scenarios such as high power, multiple heat sources, and highly non-uniform power density, the results show that: The relative deviation between the simulated and experimental values of the pressure drop of the micro-channel collector using perfluorotriethylamine as the working fluid is within -20%, and the relative deviation between the simulated and experimental values of the surface temperature is within +3 ° C, the predicted trend of the pressure drop and temperature field of the collector is in good agreement with the experimental values, indicating the feasibility of using numerical simulation methods for performance analysis and design optimization of 3-D printed micro-channel collectors. As the flow rate increases, the pressure drop of the collector increases approximately linearly, while the value increase of the total heat transfer coefficient gradually decreases, and increasing inlet temperature or heating power will reduce pressure drop of collector and increase total heat transfer coefficient. The influence of gravity on the pressure drop and total heat transfer coefficient of micro-channel collectors is less than 1. The straight through micro-channel collector has lower pressure drop and stronger heat transfer ability compared to the folded type collector. [ABSTRACT FROM AUTHOR]

In order to improve the current situation of double energy loss in waste heat recovery and utilization, according to the factors such as phase change temperature, thermal conductivity, phase change latent heat, economy, and safety of thermal storage materials, 70# phase change thermal storage balls produced by XX company were selected as phase change thermal storage materials, and differential scanning calorimetry was used to test and analyze them, and the melting point, freezing point and phase change latent heat value of PCM were obtained, provide data reference for simulation in the following text. The shell and tube heat exchanger is selected as the core component of the mobile heat storage system, and its heat storage and release processes are simulated using FLUENT software. The results show that when the heat transfer equipment is charged for 7 hours, almost all of the inner-heat exchangers have completed the heat supply, and only the phase change products at both sides and bottom of the heat supply have "dead zone", which is the major effect of heat storage. In order to improve the heat storage and release rate and break the "bottleneck" of heat storage, the heat transfer was strengthened by changing the diameter size, arrangement, and adding fins of the heat exchange tube. The effects of straight fins, T-shaped fins, as well as the number, height, thickness, and width of fins on the heat storage performance were explored. The results indicate that, adding fins cannot only improve heat transfer efficiency, but also inhibit natural-convection. The heat storage and release time decreases to varying degrees with the increase of fin width, thickness, height, and the number of circumferential fins in a single heat exchange tube. [ABSTRACT FROM AUTHOR]

The inherent flammability of polymeric materials poses a potential threat to life and the environment. From a perspective of material renewability and environmental concern, some phosphorus-rich biomass compounds have been considered as effective replacements for conventional intumescent-based flame retardants. In this work, with the aim of suppressing the potential fire hazard of highly flammable polypropylene in a sustainable strategy, a green and facile method was proposed to synthesize ZIF-67 and further used to synergistically improve the performance of phytic acid-based intumescent flame retardants. Diverging from conventional solvothermal synthesis strategies, ZIF-67 was directly prepared with polymer matrix via a solvent-free reactive extrusion method with a notable space time yield. The reaction-to-fire properties were comprehensively investigated under forced combustion bench-scale fire conditions using a cone calorimeter with an external heat flux of 50 kW m−2. It was found that flame retardancy behaviors remain competitive when replacing 10 mass% of expandable graphite with phytic acid component. With the addition of ZIF-67, the heat release (53% reduction), smoke production (22% reduction), char structure stability (35% increment), and specific extinction area (19% reduction) behaviors were further improved due to the development of compact phospho-carbonaceous networks during combustion. Considering these excellent synergistic improvements, it provides a new potential direction to efficiently fabricate biomass-based flame retardants. [ABSTRACT FROM AUTHOR]

The use of a two-stage combustion system in a hydrogen-fueled engine is characteristic of modern internal combustion engines. The main problem with hydrogen combustion in such systems is knocking combustion. This paper contains the results of research under knock combustion conditions with a single-cylinder internal combustion engine equipped with a turbulent jet ignition system (TJI). A layout with a passive pre-chamber and a variable value of the excess air ratio range λ = 1.25–2.0 with a constant value of the center of combustion (CoC = 4 deg) after top dead center (TDC) was used. Two indicators of knock combustion were analyzed: maximum oscillation of pressure and the Mahle Knock Index. Analyses were also carried out taking into account the rate of heat release and the amount of heat released. As a result of the investigation, it was found that knock combustion occurs intensively at small values of the air excess ratio. Hydrogen knock combustion disappears for λ = 2.0 and greater. The pressure oscillation index was found to be more applicable, as its limiting value (>1 bar) allows easy diagnosis of knock combustion. The Mahle Knock Index is a quantity that allows interval analysis of the knock. The choice of classes and weighting coefficients requires an iterative operation, as they strictly depend on engine characteristics, load, and knock magnitude. [ABSTRACT FROM AUTHOR]

The work has been done with the objective of overcoming the sustainability and environmental degradation pertaining to the increasing consumption of diesel fuel. This can be done by replacing it with vegetable oils because they are renewable and eco-friendly. In this regard, initially, this study investigated the performance of a single-cylinder diesel engine fuelled by neat wheat germ oil (WTGO). The results proved that the performance of WTGO was way inferior to that of sole diesel due to its very high viscosity nature. The BTE given by WTGO at full load was 2.1% lesser than diesel. Apart from NOx and CO 2 , other emissions like CO, smoke, and HC were higher for WTGO in comparison to diesel. To improve the performance and emission of WTGO, various fuel modification methods were employed with it, and the results of those methods were compared with neat diesel and WTGO. The methods adopted in this study are: i) Trans -esterified WTGO (biodiesel), ii) Fuel ionization using a magnetic field (Permanent and electrical type), iii) Dual fuel mode: WTGO operated in combination with ethanol and hydrogen. Among these, dual fuel operation of WTGO and hydrogen resulted in maximum brake thermal efficiency, followed by dual fuel operation with ethanol (30% energy share), fuel ionization (both types), and WTGO biodiesel. The WTGO, with a 15% hydrogen energy share, showed the highest BTE of 29.8%, which was higher than neat diesel (28.7%) and WTGO (26.6%). The same method reduced the HC and CO emissions by 39.3% and 40.5%, respectively, when compared to neat WTGO. All methods decreased the smoke emission, and the lowest was recorded by WTGO biodiesel, which was lesser by 21.7% and 6.1% compared to WTGO and diesel, respectively. The peak heat release rate and pressure were higher for all fuel modifications as compared to neat WTGO, but only WTGO and 15% hydrogen energy share of dual fuel operation exhibited higher peak values than diesel. The neat WTGO experienced the most delayed start of combustion, and it was improved with the implication of the above methods. The operation of WTGO in dual fuel mode resulted in the least delay for the start of combustion but was not equivalent to neat diesel. Finally, it is recommended that using hydrogen in dual fuel mode is the best way to achieve maximum performance with WTGO as a fuel for diesel engines without any major modifications to the engine. [Display omitted] • Derive biofuel from wheat germ oil. • Investigation of wheat germ oil and its methyl ester in CI engine. • Improve the engine performance using Permanent and Electro Magnetic integrated fuel filter. • Enhance the performance with hydrogen and ethanol on PCCI mode. [ABSTRACT FROM AUTHOR]

The purpose of this research is to analyze the emission, combustion, and performance parameters of a CRDI diesel engine fueled by waste cooking oil (WCO) biodiesel (B20%), diesel (80%), and their blend with two distinct metal-based nanoparticles cerium oxide (CeO2) and aluminum oxide (Al2O3). Transesterification was used to produce biodiesel from waste cooking oil (WCO). An ultrasonication procedure was used to gradually mingle the nanoparticles with a B20-diesel fuel blend in mass fractions of 50 and 100 ppm. The developed nanoparticle fuel samples were designated as (B20 + 50 Al2O3, B20 + 100 Al2O3, B20 + 50 CeO2, B20 + 100 CeO2). The CRDI engine was run at a constant speed with four different engine loads: 3 kg, 6 kg, 9 kg, and 12 kg. The result showed that the presence of Al2O3 in the blended fuel improved the BTE by 11.39%, reduced the SFC by 13.74%, and increased the cylinder pressure and heat release rate (HRR) by 16.77% and 21.48% respectively compared to B20 fuel at peak load condition. Regarding harmful emissions, CO emissions decreased by 15.06% for B20 + 50 Al2O3 than B20 and HC emissions decreased by 50% for B20 + 50 CeO2 than diesel at peak load. Further, NOx is reduced by 18.29% for B20 + 50 CeO2 than B20 at peak loads. [ABSTRACT FROM AUTHOR]

Ammonia is considered one of the most promising zero-carbon fuels for internal combustion engines. However, its poor combustion performance often leads to low efficiency and high unburned ammonia emissions in compression ignition engines. Recognizing that hydrogen can significantly enhance the combustion characteristics of ammonia, this paper explores the impact of hydrogen addition on the combustion and emission characteristics of ammonia-diesel dual fuel mode. The results indicate that with the addition of hydrogen, the heat release rate and maximum in-cylinder pressure noticeably increased under medium to high engine loads. Although NOx emissions saw a significant rise, the addition of hydrogen, combined with early diesel injection timing, inhibited N 2 O emissions. The indicated thermal efficiency (ITE) increased remarkably, reaching up to 50 %. For low-load conditions, early diesel injection resulted in a weak reactivity and low heat release rate, leading to ammonia emissions surpassing 10,000 ppm. By elevating intake heating to 55 °C, ammonia emissions were significantly reduced, improving ITE to 45 %. In conclusion, the research suggests that a high ITE can be achieved across a broad range of engine load conditions in ammonia-diesel dual-fuel combustion mode with the strategic addition of hydrogen and optimization of injection timing. • Impacts of hydrogen addition on the ammonia-diesel dual-fuel combustion mode were explored. • 50 % indicated thermal efficiency (ITE) can be reached with 10 % hydrogen for medium-high loads. • By intake heating to 55 °C and 10 % hydrogen, ITE was improved to 45 % under low load. [ABSTRACT FROM AUTHOR]

Mahua oil is a remarkable fuel since it has a similar calorific value to diesel and has similar viscosity, flash point, and boiling points to diesel. However, since mahua oil has a lower cetane number than diesel when utilized as a blend, it displays a longer ignition delay and a greater peak heat release rate, resulting in higher NOx emission. To decrease the negative impact of mahua oil on NOx emission, an effort is made to introduce the ignition improver in different proportions (i.e., 5-20% by vol). Due to its higher latent heat, IAN shows some adverse effects on performance and emission outcomes. An investigation is conducted on a CRDI engine using mahua methyl ester blended with diesel by adding oxygenated additives to the engine characteristics. The emissions like HC, CO, and smoke were reduced by 16.32, 23.56, and 23.12%. The improved combustion process increases NOx and CO2 emissions by 13.62 and 19.89%. Also, an increase in HRR and CP values was noticed at full load operation. Additionally, it is observed that the engine's performance is enhanced using 15% Iso-amyl nitrate (IAN), indicating that the IAN blend is a useful ignition improver for mahua oil and diesel blends. [ABSTRACT FROM AUTHOR]

This work numerically investigates longitudinal and azimuthal thermo-acoustic instabilities in the swirl-stabilised can-type industrial SGT-100 gas turbine combustor operated at elevated pressures of 3 and 6 bar. Previous experiments have shown that the combustor is susceptible to self-excited flame oscillations sustained by a thermo-acoustic feedback loop at specific operating conditions. In order to gain a better understanding of this feedback loop, a fully compressible large eddy simulation method is applied. The unknown sub-grid scale turbulence-chemistry interactions are modelled via a transported probability density function approach solved by the Eulerian stochastic fields method. First, the reaction zones and global flame topology at both operating pressures are analysed and compared to experimental images providing good qualitative agreement. Radial profiles of time-averaged and root-mean-square quantities furthermore demonstrate good quantitative agreement with the available measurement data. The applied simulation approach is capable of successfully reproducing self-excited thermo-acoustic instabilities in the longitudinal direction. The fundamental frequency of the predicted limit-cycle oscillation matches the experimentally measured frequency with high accuracy. Similar to the experimental observations, the fluctuation amplitudes of the pressure and global heat release rate increase significantly upon increasing the mean operating pressure from 3 to 6 bar. In addition to the dominant longitudinal mode, a high-frequency, low-amplitude azimuthal mode is also identified at both pressures. This azimuthal mode is periodically amplified and attenuated by the superposed longitudinal mode and induces small asymmetric (around the burner circumference) fluctuations of the local fuel and total mixture mass flow rates entering the flame region. [ABSTRACT FROM AUTHOR]

In order to investigate the impact of cooling plate channel structural parameters on the cooling performance of battery modules, a heat generation model for LiFePO4 batteries was established. Based on the model, the 1C discharge process of LiFePO4 batteries at room temperature (25 °C) was simulated, and relevant heat release data were obtained. On this basis, three different cooling plate structures (Model A, Model B, Model C) were designed, and the cooling performance of the cooling liquid (50% water and 50% ethylene glycol) for the battery module was analyzed by simulation at different mass-flow rates (0.15 kg/s, 0.18 kg/s, 0.21 kg/s), along with the pressure, temperature difference and flow rate of the cooling channel. The results showed that the uniformity of the flow rate in the channel can reduce the temperature difference. Under the same mass-flow rate, the temperature difference of the battery module on the same surface between Model A and Model C was 1.1 °C, but too many channels would increase the pressure drop. The pressure drop of Model C was more than 10 times that of Model B. Therefore, it is necessary to design the channel structure reasonably while ensuring the heat dissipation effect. Finally, based on the simulation results, beneficial suggestions for the cooling and cooling plate design and manufacture of energy storage container battery modules are proposed. [ABSTRACT FROM AUTHOR]

Fire is one of the most undesirable events onboard a ship. The engine room is one of the most critical spaces in the ship in terms of fire protection, as it includes machinery, hydrocarbon fuel systems, and different electrical equipment. With the phasing out of Halon 1301 as a fire suppressant over recent decades, there has been an intensive effort to explore the efficacy of water-mist spray in mitigating fires within machinery spaces. This exploration entails a comprehensive investigation through experimental and simulation studies aimed at identifying suppression mechanisms and evaluating their effectiveness. While experimental setups typically encompass measurements of gas temperature, thermal radiation heat flux, oxygen concentration, and fire extinction time, limited attention has been paid to quantifying the heat release rate (HRR), a crucial indicator of fire magnitude. Furthermore, research into shielded fire scenarios remains sparse, despite their significance in maritime fire dynamics. Addressing shielded fires with water mist proves particularly challenging due to the potential obstruction impeding the direct interaction between the fire source and the water droplets. In the existing literature, most of the computational fluid dynamics (CFD) modelling of fires and suppression was performed using a Fire Dynamics Simulator (FDS). Alternate studies were performed using FireFOAM. and very few employed FLUENT and other analogous software codes. In the majority of reported computational studies, the determination of HRR was typically relied upon for its calculation derived from the measured data of fuel mass loss rate. Moreover, certain studies were undertaken for numerical simulations without conducting thorough model validation, either by omitting validation altogether or solely validating against dry fire experiments (i.e., without water-mist suppression). This critical review of the literature has identified several notable research gaps in the context of extinguishing hydrocarbon fires utilising water-mist spray, warranting further investigations. Additionally, this review paper highlights recent advancements in both experimental and numerical investigations pertaining to the efficacy of water-mist fire-suppression systems in enclosed spaces regarding hydrocarbon fires. [ABSTRACT FROM AUTHOR]