Heat Release Research Articles

DATAWARE AND SOFTWARE OF THE AUTOMATED TECHNOLOGY FOR COMPUTER- INTEGRATED CONTROL OF HEAT PUMP SYSTEMS

The paper has solved a scientific and applied problem as for substantiating requirements to technical and functional characteristics of the automated technologies of computer-integrated control of heat pump systems in the heating and cooling modes owing to its dataware and software developing and testing. Following functional procedures have been taken into consideration during the dataware and software development of the computer-integrated subsystem for heating of buildings: monitoring of ambient air temperature, ground temperature, and operating modes of functional elements of the heat pump system as well as zonal monitoring of indoor air temperature; computer-integrated processing of the monitoring data; automated control of the heat pump as well as modes of zonal thermal medium supply to the building; and analysis of energy efficiency as for implementation of the proposed computer-integrated method to control systems of thermodynamic heating. It has been identified that thermal capacity of a heat pump is rather sensitive to indicators of the total heat losses of a building. If the total heat losses increase from 0.2°С/hour up to 0.5°С/hour then constant value of the thermal capacity increases by 48%. Moreover, thermal capacity of a heat pump is quite sensitive to ambient air temperature dynamics: if temperature variation is 12°С (i.e. 3°С-9 °С) then average increase in thermal capacity is 58 %. Following functional procedures have been involved during the dataware and software development of the computer-integrated subsystem for cooling of buildings: monitoring of ambient air temperature and operating modes of functional elements of the heat pump system; zonal computer-integrated monitoring of indoor air temperature; computer-integrated the monitoring data processing based upon microcontrollers; automated control of the thermal pump operating modes (i.e. heat energy outfeed and release to the main intercooler unit); and analysis of energy efficiency as for implementation of the proposed computer-integrated method to control systems of thermodynamic cooling of buildings. The abovementioned has helped identify that thermal capacity of a heat pump is rather sensitive to indicator of heat exchange with surrounding air: four times increase in heat-exchange coefficient (i.e. from 1°С/hour up to 4°С/hour) results in 20% growth of thermal capacity of the cooling subsystem system at similar ambient air temperature (it varies from 30°С up to 36 °С) if the maintained target indoor temperature is 22°С.

Multifunctional Polymer Composites for Automatable Induction Heating with Subsequent Temperature Verification

Manipulating ferromagnetic particles using an alternating current (AC) magnetic field is a versatile method for quick, local, and on‐demand heat generation. These particles can be incorporated into various matrices as heating elements. Their heat release can be controlled by adjusting process or material parameters. Herein, a proof‐of‐concept for a flexible polymer composite with customizable magnetically triggered heat release due to prior object identification via fluorescence readout is presented. The maximum temperature resulting from this process can be determined through a second fluorescence readout ex post. This novel combination of functionalities results from the synergistic interaction of inductively heatable magnetic supraparticles (SPs) and luminescent communicating SPs in one polydimethylsiloxane composite. The surface of the composite can be heated to the maximum temperatures of choice in a range between 125 and 200 °C within 2 s. Heat release and temperature verification provide spatial resolution of millimeters. The identification signature and the working range of the temperature indication functionality of the composite are customizable by exploiting its modular material design. The temperature indication functionality of the composite offers spatial resolution and ex‐post readout at any point of interest, making it a versatile alternative to established optical thermometry methods.

Towards fire-safe, smoke-suppression and recyclable epoxy composite from bio-derived flame retardant

Epoxy-based vitrimers appear as a promising alternative to common epoxy materials. Nevertheless, the possibility of epoxy vitrimers in practical applications is limited by their high flammability. In this study, a novel bio-based casein phosphopeptide chelating zinc (CPP-Zn) is purposely developed, specifically designed to serve as a flame retardant and smoke suppressant for epoxy vitrimer, operating through a condensed phase mechanism. To further enhance the fire safety of epoxy resins, DOPO derivative (DDP) is synthesized through grafting with bio-based itaconate and subsequently used as a synergistic flame retardant in combination with CPP-Zn. DDP exhibits gas phase flame retardant mechanism through the release of free radical scavangers generated during combustion. As a result of the combination of condensed and gas phase effect, the composite achieves self-extinguishing within 1 second, attains a V-0 rating in UL-94 testing, and boasts an LOI of 32.3 %. Additional, it shows a remarkable 73.7 % reduction in heat release rate (HRR) and 27.2 % in total smoke production (TSP) compared with neat epoxy vitrimer. The experimental results also evidence that the characteristic features of vitrimers, self-healing and recyclability, have been retained in the prepared flame-retarded composites. The remolded 50D/EST-25Cz is still able to maintain 72.2 % of its tensile strength. This opens promising avenues for the development of highly fire-safe and eco-friendly epoxy resins.

Fire Properties of Paper Sheets Made of Cellulose Fibers Treated with Various Retardants.

This article presents the results of flame-retardancy tests conducted on cellulose sheets produced using a Rapid Köthen apparatus treated with retardants. The agents used were potassium carbonate (PC) K2CO3 (concentrations of 20; 33.3; and 50% wt/wt), monoammonium phosphate (MAP) NH4H2PO4 (concentrations of 35% wt/wt), diammonium phosphate (DAP) (NH4)2HPO4 (concentrations of 42.9% wt/wt), and bisguanidal phosphate (FOS) C2H10N6 (concentrations of 22.5% wt/wt). The agents were used to improve Kraft cellulose-based sheets' flame-retardant properties and compare their performances. As part of the study, the flammability of the materials was determined by the following methods: an oxygen index (OI) test, a mass loss calorimeter (MLC) test, and a mini fire tube (MFT) test. All formulations showed an increase in flame retardancy compared to the control test. All protected samples were non-flammable for OI determinations, and DAP-protected samples showed the highest OI index. For the MLC test, DAP-protected and MAP-protected samples showed the best heat-release rate (HRR), total heat release (THR), and average heat-release rate (ARHE) (samples did not ignite for 600 s). In the MFT test, all treated samples had comparably reduced weight loss. The best parameter was achieved for MAP and DAP (15% weight loss).

Thermal conductive enhanced phase change composites with high latent-heat for constant temperature thermal management

Phase change materials (PCMs) can absorb and release heat without the temperature changing to realize the constant temperature thermal management. The low thermal conductivity (K) of PCM molecules leads to slow heat absorbing and releasing. In this study, a polyethylene glycol (PEG) based cross-linked polyurethane network is synthesized to wrap PCMs microcapsules. The composites have a high latent heat (152–164 J g−1) at 38 °C. Carbon fiber (CF) and Al powder with high K is composted to improve the thermal conductivity of the PCMs. After doping with CF, the K increases to two-fold to 0.306 W m−1 K−1. The experimental result reveals that the heat transfer inside the PCMs is improved obviously after doping with CF, which is further verified by a simulation result, and the composites show excellent shape stability and latent heat retention rate (>92 %) under 30 days' cycle test. This thermal conductivity enhanced PCMs composite is also formable which may have the potential applications for the thermal management of electronic devices, such as chips, fast charging, and battery.

A comprehensive enhancement of the optical, mechanical, low dielectric, and flame-retardant characteristics of epoxy resin by the incorporation of multifunctional additive

Epoxy resin is widely utilized but faces the drawback of flammability. However, adding flame retardants often results in the compromise of other properties, such as mechanical and optical characteristics. In this study, a phosphorus-nitrogen multifunctional flame retardant named DPVPI was successfully synthesized. The resulting epoxy resin containing DPVPI demonstrated good transparency and low dielectric constant. Furthermore, the unique structure of DPVPI led to additional enhancements in the mechanical properties of EP composite. The tensile strength of EP composite was increased by 33 %, and the impact strength was improved from 13.61 kJ/m² to 25.74 kJ/m². Remarkably, the composites with Only 4wt% DPVPI can achieve a V-0 rating in the UL-94 test and the maximum limiting oxygen index (LOI) of it reached 32.6 %. The cone calorimeter test showed that the peak heat release of the composites with a 5 wt% addition decreased by 35 %, the total smoke release decreased by 37 %, and the char yield doubled. This research presents a novel strategy for subsequent synthesis endeavors about multifunctional flame retardants.

Multifunctional nanocomposite coating for aluminium alloy: Corrosion resistance, flame retardancy, and mechanical enhancement for automotive components

Aluminium alloys are utilized in the automotive industry for components such as engine blocks, wheels, chassis, and body panels. Their lightweight nature helps reduce vehicle weight, leading to improved fuel efficiency and lower emissions. The development of nanocomposites incorporating impermeable two-dimensional materials holds significant promise for safeguarding metals against corrosion. By introducing N-aminoethyl-3-aminopropyltrimethoxysilane (AAMS) functionalized molybdenum nitride (MoN) into a coating matrix, the barrier effect can be significantly enhanced owing to its remarkable chemical and thermal stability. This enhancement is further amplified through the incorporation of functionalized MoN into graphitic carbon nitride (GCN) within a polyurethane (PU) matrix, resulting in improved corrosion protection and fire-retardant properties. Through electrochemical techniques conducted in marine environments, the protective efficacy of aluminium coated with polyurethane, alongside varying concentrations of functionalized MoN/GCN, was assessed. The resulting PU composite exhibited superior flame-retardant capabilities, manifesting in substantial reductions in peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP) compared to pure PU formulations. Electrochemical impedance spectroscopy (EIS) measurements revealed a notable enhancement in coating resistance (5.65 × 1011 Ω. cm2), even following 500 h of exposure to the electrolyte. Furthermore, the newly formulated PU composite, featuring functionalized MoN/GCN, demonstrated exceptional water repellency with a water contact angle (WCA) of 157°. This remarkable hydrophobicity underscores its potential for applications requiring protection against moisture ingress. Additionally, the PU composite exhibited commendable mechanical properties, boasting an adhesive strength of 19.1 MPa within the PU substrate. This enhanced adhesive strength ensures the coating's integrity even after prolonged immersion periods. Given its multifaceted benefits, the PU composite incorporating functionalized MoN/GCN emerges as a promising candidate for integration into automotive industries as a viable coating component. Its ability to concurrently provide corrosion protection, flame retardancy, water repellency, and mechanical robustness underscores its potential to enhance the durability and longevity of automotive components, thereby contributing to improved performance and longevity in harsh operating environments.

Preparation of Al@FTCS/P(VDF-HFP) Composite Energetic Materials and Their Reaction Properties.

Strengthening the interfacial contact between the reactive components effectively boosts the energy release of energetic materials. In this study, we aimed to create a close-knit interfacial contact condition between aluminum nanoparticles (Al NPs) and Polyvinylidene fluoride-hexafluoropropylene (P(VDF-HFP)) through hydrolytic adsorption and assembling 1H, 1H, 2H, 2H-Perfluorododecyltrichlorosilane (FTCS) on the surface of Al NPs. Leveraging hydrogen bonding between -CF and -CH and the interaction between C-F⋯F-C groups, the adsorbed FTCS directly leads to the growth of the P(VDF-HFP) coating layer around the treated Al NPs, yielding Al@FTCS/P(VDF-HFP) energetic composites. In comparison with the ultrasonically processed Al/P(VDF-HFP) mixture, thermal analysis reveals that Al@FTCS/P(VDF-HFP) exhibits a 57 °C lower reaction onset temperature and a 1646 J/g increase in heat release. Associated combustion tests demonstrate a 52% shorter ignition delay, 62% shorter combustion time, and a 288% faster pressurization rate. These improvements in energetic characteristics stem from the reactivity activation of FTCS towards Al NPs by the etching effect to the surface Al2O3. Moreover, enhanced interfacial contact facilitated by the FTCS-directed growth of P(VDF-HFP) around Al NPs further accelerates the whole reaction process.

Preparation of a Highly Flame-Retardant Urea-Formaldehyde Resin and Flame Retardance Mechanism.

Urea-formaldehyde (UF) resin is the most widely used adhesive resin. However, it is necessary to improve its flame-retardant performance to expand its applications. In this study, exploiting electrostatic interactions, anionic phytic acid and cationic chitosan were combined to form a bio-based intumescent flame-retardant, denoted phytic acid-chitosan polyelectrolyte (PCS). The molecular structure of the urea-formaldehyde resin was optimized by crosslinking with melamine and plasticizing with polyvinyl alcohol-124. Thus, by combining PCS with the urea-formaldehyde resin and with ammonium polyphosphate and ammonium chloride as composite curing agents, flame-retardant urea-formaldehyde resins (FRUFs) were prepared. Compared to traditional UF resin, FRUF showed excellent flame retardancy and not only reached the UL-94 V-0 level, but the limit of oxygen index was also as high as 36%. Compared to those of UF, the total heat release and peak heat release rate of FRUF decreased by 86.44% and 81.13%, respectively. The high flame retardancy of FRUF originates from the combination of oxygen and heat isolation by the dense carbon layer, quenching of phosphorus free radicals, and dilution of oxygen by a non-flammable gas. In addition, the mechanical properties of the FRUF remained good, even after modification. The findings of this study provide a reference for the flame-retardant application of FRUF for applications in multiple fields.

Joint Exfoliation of MXene by Dimensional Mismatched SiC/ZIF-67 Toward Multifunctional Flame Retardant Thermoplastic Polyurethane.

The single-layer MXene fully demonstrates the advantages of 2D materials, especially catalytic, conductive, and mechanical properties. However, the high energy consumption and low efficiency faced by MXene in the divestiture process are still challenges that need to be solved urgently. In this article, dimension mismatch and collaborative stripping strategies are skillfully combined to easily realize the transformation from multi-layer MXene to single layer. In addition, the functionalized MXene@SiC@polyaniline (MXene@SiC@PANI) nano-hybrid materials are used as fillers to improve the thermal conductivity, flame retardant, and antibacterial properties of thermoplastic polyurethane (TPU). The surface temperature of TPU/MXene@SiC@PANI composites increased from 33.4°C to 59.8°C within 10 s. In addition, the antibacterial efficiency of TPU composites against Escherichia coli and Staphylococcus aureus is 69.6% and 88.9%, respectively. Compared with pure TPU, the peak heat release rate and total heat release are reduced by 71.4% and 34.6%, respectively. The flame-retardant mechanism of MXene hybrid materials is systematically discussed. It is worth noting that the introduction of PANI enhances the compatibility between the filler and the polymer, effectively maintaining the mechanical properties of the TPU itself. This work provides a convenient method for the multi-functional practical application of TPU.

Energetic transition metal complexes based on 1‐allylimidazole and nitrocyanamide: Syntheses, characterizations and catalytic performances on the thermal decomposition of ammonium perchlorate

AbstractTo explore combustion catalysts for solid propellants, four novel energetic coordination compounds were prepared with the anion of nitrocyanamide (NCA) as the ligand and 1‐allyl‐imidazole (AIM) as the ligand, and transition metals Mn, Co, Ni, and Cu as the central ions. The structures of these compounds were [Mn(AIM)4] (NCA)2 (1), [Co(AIM)4](NCA)2 (2), [Ni(AIM)4](NCA)2 (3), [Cu(AIM)4](NCA)2 (4). The results showed that all of the compounds possessed high energy density, and compound 2 had a mass energy density (Eg) of 17.9 kJ g−1 and a volume energy density (Ev) of 25.59 kJ cm−3. The catalytic effect of these compounds on the thermal decomposition of ammonium perchlorate (AP) was studied using DSC. The addition of 5 % catalyst to AP samples advanced the high‐temperature decomposition temperature and significantly increased the heat release. Compound 4 exhibited the best catalytic performance, with an increased heat release of 1739 J g−1, decomposition temperature advanced by 88.2 °C, and activation energy reduced to 74.74 kJ mol−1. These results demonstrate the potential of these compounds as combustion catalysts for solid propellants.

Half etching of ZIF-67 towards open hollow nanostructure with boosted absorption ability for toxic smoke and fume in epoxy composites

Metal-organic frameworks (MOFs) are favored in the field of flame retardancy due to the catalytic effect of metal nodes on char layer formation and the synergistic flame-retardant effect of organic ligands containing elements such as nitrogen and phosphorus. However, the inherent microporosity of MOFs limits their adsorption efficiency for toxic smoke and flammable gases. In this work, an organic phosphorus-modified MOF with a distinctive nanostructure of hierarchically porous (P-Co-MOF/ZIF) was successfully synthesized. In brief, an amino-functionalized zeolitic imidazolate framework (NH2-ZIF) was initially synthesized through a ligand substitution reaction with ZIF-67. Subsequently, organic phosphorus flame retardants were grafted on NH2-ZIF, and the acidic substances generated during this process were used to synchronously half etch ZIF, resulting in a ZIF with a high specific surface area and unique nanostructure. Through this simple synthetic method, the catalytic ability of transition metals in ZIF is preserved, and organic phosphorus flame retardants are incorporated into ZIF, resulting in the synergistic flame-retardant effect of phosphorus and nitrogen. Additionally, its unique hierarchically porous nanostructure can effectively enhance the adsorption of volatile products during the combustion process, thereby offering outstanding flame retardancy and smoke suppression effects for epoxy resin (EP). The results indicate that adding 2 wt% P-Co-MOF/ZIF to EP can increase the limiting oxygen index value to 29.5%. Furthermore, the peak of heat release rate, total heat release, and total smoke production of the composite material can decrease by 43.3%, 37.9%, and 38.1%, respectively, compared to EP. Therefore, this work will provide new inspiration for designing functional nanostructures and synthesizing efficient flame retardants.

Sodium iron sulfate cathodes with ultra-long cycle-life and high safety for sodium-ion batteries

The development of low-cost and high-safety cathode materials is critically important to sodium-ion battery (Na-ion) research. Here we report a carbon nanotube (CNT)-percolating Na2Fe(SO4)2 cathode (NFS-CNT) prepared via a rationally designed mechano-chemical method. The material synthesis mechanism is elucidated for the first time by in situ X-ray diffraction and thermogravimetric analysis. It is discovered that Na2Fe(SO4)·4H2O is formed as an intermediate phase during the mechano-chemical process, which is dehydrated to produce the Na2Fe(SO4)2 cathode material upon a mild thermal treatment. The NFS-CNT composite cathode achieves an ultra-long cycle-life of over 13,000 cycles at 10 C at room temperature and over 6000 cycles at 55 °C, demonstrating its exceptional durability. The superior cycling performance is attributed to the small lattice change during Na-ion extraction/insertion and the percolating CNT network. Furthermore, the NFS/CNT cathode exhibits stable cycle performance in Na-ion full cells (93.4 % retention after 700 cycles) and a significantly lower heat release (∼ 229.2 J g−1) at the fully charged state compared to a wide range of Na-ion and Li-ion cathodes. materials. demonstrating its high thermal stability and safety. This work provides a promising path towards developing low-cost, high-performance Na-ion batteries.

Development of a reduced primary reference fuel – oxymethylene dimethyl ether (PRF-OMEx) mechanism for diesel engine applications

Oxymethylene dimethyl ethers (OMEx), having a chemical formula of CH3O-(CH2O)x-CH3 where x varies from 1 to 5, have been widely considered as a promising fuel to partially replace diesel in CI engines in terms of reducing soot emissions. This work is focused on developing a reduced primary reference fuel (PRF)-OMEx chemical mechanism to better describe the combustion and emission characteristics of gasoline/diesel blends with OMEx. The novelty of this work lies in the fact that the OMEx part of the mechanism is represented not only by OME3 as done in most studies found in literature, but also with other OME chain lengths that is, OME2-4 which are considered to be optimum and better represent the commercial OMEx blends. For this purpose, a detailed OMEx mechanism is reduced by applying different reduction techniques considering a wide range of operating conditions including pressure, temperatures, equivalence ratios and fuel compositions. The result is merged with an already validated PRF mechanism to form a reduced PRF-OMEx mechanism consisting of 213 species and 840 reactions. The newly formed mechanism is validated against a wide set of experimental data including ignition delay times, laminar flame speeds and species concentration profiles. Furthermore, a rigorous set of numerical simulations for various diesel-OMEx blends in a compression ignition engine are carried out at two different operating points to validate the developed mechanism. Simulation results highlight that the developed mechanism not only replicates the experimental behavior in terms of in-cylinder pressure and heat release rate but exhibits a better combustion phasing closer to experimental data when compared with other mechanisms where only OME3 is utilized to represent OMEx. Overall, the developed PRF-OMEx mechanism proves to be realistic and suitable for application in engine combustion simulations involving gasoline/diesel and OMEx blends.

Functionalized Zr‐MOFs for Enhancing Flame Retardancy and Smoke Suppression Performance on TPU

AbstractMetal‐Organic Framework (MOF) materials can be used as flame‐retardants and smoke suppressants for polymers. As a MOF material, UIO‐66(Zr) possesses higher thermal stability and controllable pore size. In this paper, UIO‐66(Zr), NH2‐UIO‐66(Zr), and SiO2, MWCNT, and GO functionalized NH2‐UIO‐66(Zr) was fabricated to improve the flame retardant and smoke suppression performance of thermoplastic polyurethanes (TPU). The experimental results show that compared with neat TPU (LOI value 19.1 %), 2 % usage of UIO‐66(Zr) and NH2‐UIO‐66(Zr) can endow TPU with 26 % LOI value and vertical combustion rating of V‐1. Moreover, SiO2, MWCNT, and GO functionalized NH2‐UIO‐66(Zr) provide TPU with above 27.8 % LOI value and vertical combustion rating of V‐0. Meanwhile, the CCT results showed that the peak heat release rate and total heat release of TPU‐U5 (added 2 % GO‐modified NH2‐UIO‐66(Zr)) are 299.52 Kw ⋅ m−2 and 68.21 MJ m−2, much lower than that of neat TPU, which are 1180.05 Kw ⋅ m−2and 104.87 MJ m−2, respectively. The TGA, char residue EDS and XRD analysis show that SiO2, MWCNT, and GO functionalized NH2‐UIO‐66(Zr) could generate zirconium metal oxide during the combustion process, which acts as a physical barrier to prevent the TPU matrix by promoting the generation of carbonization layer. The zirconium metal oxide and carbonization layer also can confine flammable gases, which can delay the ignition time and hinder the overflow of gas. In addition, NH2‐UIO‐66(Zr) could generate non‐flammable N2 diluting the concentration of flammable gases. The mechanical properties of TPU composites can maintain more than 87 % of the neat TPU after the addition of 2 % SiO2, MWCNT, and GO functionalized NH2‐UIO‐66(Zr). These results indicate that functionalized Zr‐MOFs composites could act as excellent flame‐retardants in TPU.

Self-assembled coatings with durable flame retardancy for EPS foam

Layer by layer (LBL) self-assembly coatings upon expandable polystyrene (EPS) surface play an important role in improving its flame retardancy. However, a large number of layers is needed to achieve a satisfied fire performance, and the coatings are difficult to adhere on the inert EPS surface, resulting in the poor durability. In this work, the surface of EPS was activated by ultraviolet ozone (UVO) with the appearance of oxygen contained groups, then a LBL coating with only two bilayers (branched polyethyleneimine (BPEI)-kaolinite (kaol)-BPEI-diethylene triamine penta (methylene phosphonic acid)) was covalently connected on the EPS surface. Compared with neat EPS, the obtained E-K5D30 sample increased the value of limiting oxygen index (LOI) from 18.8 % to 37.7 %, improved the ignition time from 59 s to 95 s, reduced the peak heat release rate (pHRR) value from 282.0 kW/m2 to 220.9 kW/m2, and enhanced the char residues from 6.3 % to 32.3 % after the combustion. Moreover, an ultraviolet (UV) curing layer with P/N elements was prepared upon E-K5D30 sample to maximize the flame retardant durability. A novel amino-intercalated kaol was used to play a smoke suppression role. The results showed that E-K*5D30-P8N3 sample further increased the LOI to 39.2 %. Even after 12 h washing, the E-K*5D30-P8N3 sample exhibited a slight LOI reduction to 37.8 %, and fire performance index (FPI) value of 0.405 m2·s/kW, showing the successful construction of coatings with good fire safety and flame retardant durability.

Evaluation of WRF Cloud Microphysics Schemes in Explicit Simulations of Tropical Cyclone ‘Fani’ Using Wind Profiler Radar and Multi-Satellite Data Products

Extremely severe cyclonic storm (ESCS) ‘Fani’ formed in the North Indian Ocean and crossed at Puri in Orissa State on the east coast of India on 03 May 2019. In this study, we examine the sensitivity of convection permitting WRF simulations (3 km) of ‘Fani’ to cloud microphysics (CMP) schemes using radar and multi-satellite data products. Five CMP schemes, namely Thompson, Goddard, WSM6, Morrison and Lin are tested in WRF. Results show that the changes in the CMP schemes primarily affect the simulated intensity and have lesser impact on the track predictions. Simulations with Thompson followed by Goddard produced the best predictions for both track and intensity estimates. Our analysis reveals significant variations in vertical motions associated with Fani across different CMP schemes; the WSM6, Goddard and Lin schemes produced relatively stronger vertical motions. The explicit WRF simulations could reproduce the wind profiler radar observed intense convective motions during the transit of Fani between 1 and 2 May 2019 at Gadanki station. Experiments with Thompson and Goddard schemes simulated the mean vertical velocities in lower, middle and upper layers in better agreement with radar data. The Lin, WSM6 and Goddard CMP predicted stronger updraft velocities (~ 0.35 m/s); Thompson produced moderate updraft velocities (~ 0.25 m/s) in the upper troposphere over a relatively wider area of high theta-e (385–390 K) indicating the simulation of a convectively stronger and warmer core compared to Morrison. Our analysis suggests that the differences in vertical motions in various CMP simulations are mainly due to the variations in the warming in simulations. It has been found that WSM6, Lin and Goddard produced a deeper core (up to 200 hPa) with a stronger diabatic heating of ~ 6° C followed by Thompson, which simulated a moderately deep core extending to ~ 250 hPa with moderate heating of ~ 5 °C whereas Morrison produced a relatively weak core with a heating of ~ 4 °C limited to 300 hPa. The stronger simulated diabatic heating in Lin, WSM6 and Goddard produces stronger inflow, moisture convergence in the lower levels and stronger outflow and divergence in the upper levels leading to stronger convection in the core region in these cases. The Lin, WSM6 and Goddard mixed phase schemes with more solid hydrometeors simulated stronger radar reflectivities, and stronger eyewalls, due to more latent heat release leading to the development of a strong warm core in the upper troposphere and thus a stronger TC.

Predict Future Transient Fire Heat Release Rates Based on Fire Imagery and Deep Learning

The fire heat release rate (HRR) is a crucial parameter for describing the combustion process and its thermal effects. In recent years, some studies have employed fire scene images and deep learning algorithms to predict real-time fire HRR, which has led to the advancement of HRR prediction in terms of both lightweightness and real-time monitoring. Nevertheless, the development of an early-stage monitoring system for fires and the ability to predict future HRR based on current moment data represents a crucial foundation for evaluating the scale of indoor fires and enhancing the capacity to prevent and control such incidents. This paper proposes a deep learning model based on continuous fire scene images (containing both flame and smoke features) and their time-series information to predict the future transient fire HRR. The model (Att-BiLSTM) comprises three bi-directional long- and short-term memory (Bi-LSTM) layers and one attention layer. The model employs a bidirectional feature extraction approach, followed by the introduction of an attention mechanism to highlight the image features that have a critical impact on the prediction results. In this paper, a large-scale dataset is constructed by collecting 27,231 fire scene images with instantaneous HRR annotations from 40 different fire trials from the NIST database. The experimental results demonstrate that Att-BiLSTM is capable of effectively utilizing fire scene image features and temporal information to accurately predict future transient HRR, including those in high-brightness fire environments and complex fire source situations. The research presented in this paper offers novel insights and methodologies for fire monitoring and emergency response.

Influence of structure parameters of pre-chamber on lean combustion of active pre-chamber jet ignition engine

Turbulent jet ignition (TJI) technology has the potential to improve engine efficiency. To elucidate the influence of different factors (diameter and number of holes) affecting the nozzle's total cross-sectional area, internal structure of the pre-chamber, and nozzle angle on the combustion characteristics of the engine. A 3 × 3 orthogonal test was designed and machined. The experiments were carried out on a pre-chamber single-cylinder engine.The results show that the pre-chamber's internal volume ratio has a great effect on the combustion characteristics in the cylinder. While the volume ratio of top of pre-chamber, transition region, and pre-chamber throat is 1:1:1, the engine's peak heat release rate is the highest. The highest Indicated thermal efficiency (ITE) can reach 43.43 %, with an absolute increase of 1.24 %, and the lean burn limit can reach λ = 2.6. Too large or too small nozzle angle will worsen the combustion state in the cylinder. The aperture and Nozzle number, which are the factors influencing the nozzle's total cross-sectional area, have different effects on the ignition delay, CA10-CA50, and CA50-CA90 of the engine. Various factors affecting the nozzle's total cross-sectional area have no apparent influence on the changing trend of ITE, but the aperture greatly influences ITE.

Analysis of stage parameters of low-temperature oxidation of water-soaked coal based on kinetic principles

Mine fires caused by spontaneous coal combustion are major disasters in coal mines. The staged oxidation kinetic parameters of various coal samples at oxygen concentrations of 21 %, 15 %, 10 %, 5 %, and 3 % were analyzed using a programmed temperature testing system. Herein, the temperature increase rate of coal, the temperature difference between the furnace and coal, and the oxygen consumption characteristics were obtained. Based on the amount of CO produced and the temperature sensitivity coefficient, three characteristic temperatures and four stages of low-temperature oxidation (LTO) were identified. The results showed that at a critical temperature (TC), the amount of CO gas released from the coal samples increased with increasing oxygen concentration, and the difference in the oxygen consumption rate increased. After the limit temperature (Tu), the amount of CO gas increased steadily, and the increase in the oxygen consumption rate stagnated. CO production, the maximum heating rate, and the maximum heat release rate were positively correlated with the oxygen concentration. As the oxygen concentration increased, the activation energy during the oxygen absorption stage gradually decreased. The average reaction enthalpy (ΔH) of pre-oxidized water-immersed coal was 19.37 kJ/kg greater than that of raw coal. The equation for the conservation of energy of the coal oxidation warming process was normalized. The theoretical values of the awakening stage and the stable stage were τν and τν (1-B), respectively. When B was >1, pre-oxidized water-immersed coal at a low oxygen concentration was prone to crossover points during the oxygen absorption stage, which increased the risk of coal spontaneous combustion (CSC). The research results could provide a theoretical basis for the staged control of the spontaneous combustion of water-immersed coal in goaf areas.