The 5AT/Sr(NO3)2 mixture has recently attracted attention as a gas-generating agent for use in novel fire-suppression applications. However, it cannot provide the desired combustion behavior alone. Thus, nitroguanidine (NQ) was added as a fuel component to 5AT/Sr(NO3)2 in attempt to improve the mixture's combustion behavior. The effects of NQ on the thermal and burning characteristics of 5AT/Sr(NO3)2 were investigated. Thermogravimetry-differential scanning calorimetric (TG-DSC) analysis with four heating rates (5, 10, 15, 20 K min−1) under a nitrogen atmosphere was performed to determine the thermal characteristics and non-isothermal reaction kinetic parameters. The addition of NQ decreases the activation energy of the Stage II and III decomposition reaction, and accelerates the redox reaction and decomposition of Sr(NO3)2. Thermodynamic calculations and measurements of temperature profile and liner burning rates were performed to evaluate the combustion characteristics. Adding NQ decreased the adiabatic combustion temperature, outlet temperature, average flame height, flame oscillation frequency and pressure exponent of Vieille's equation, and increased the gas output and linear burning rate. Notably, mesa burning occurred when NQ was added, the mechanism of which is elaborated using a physical combustion model. The analysis deepens the understanding of when the gas-phase or condensed-phase reactions control the burning characteristics of the composite propellant.

•Maximum smoke temperature was studied by a reduced-scale enclosed channel model.•Fire locations showed significant influence on the maximum smoke temperature.•Existing model was improved to predict maximum smoke temperature in enclosed channel.•The improved model obeys reasonably well with the experimental results.Smoke movement and the temperature beneath the ceiling in enclosed channel were investigated experimentally and theoretically. The experimental results show that the maximum smoke temperature decreases with an increasing flame inclination angle when fire source is moving away from the channel center in Region I (within the dimensionless distance for 0.64), which is caused by the gas velocity difference of the two sides of flame. However, when the dimensionless distance is >0.64, the maximum smoke temperature was observed to rise. In addition, an existing model was improved to predict the maximum smoke temperature in enclosed channel applying it to different boundary conditions. Its predictions fit reasonably well when the fire source located at Region I. Beyond that, the predictions are lower than the experiments, which is probably because of the absent consideration of bouncing process of the hot smoke from end walls. Therefore, an extra correction coefficient was proposed to the improved model in Region II with a consideration of bouncing process of the hot smoke from both end walls. As a result, it was found that the experimental results can be well predicted by this model in Region II.

•Monolithic silica aerogels were synthesized rapidly by ambient pressure drying (APD) using water as the only solvent.•CTAB plays an important role in overcoming phase separation.•Various properties of aerogels can be adjusted through changing the concentrations of CTAB.•This method for aerogel synthesis avoids lengthy solvent exchange and surface modification.To avoid lengthy solvent exchange and surface modification processes and reduce the production cost, monolithic silica aerogels were prepared rapidly (reduced from regular three days to 5 h) under ambient pressure using methyltrimethoxysilane (MTMS, precursor) and water (solvent). For preparing aerogels in aqueous phase, the phase separation caused by the immiscibility between hydrophobic oligomers and water should be avoided. This problem has been solved by using an efficient surfactant, cetyltrimethylammonium bromide (CTAB). The porous morphology and different properties of the aerogels were observed changing along the content of CTAB. It was found that the macroporous morphology evolves from coarsened structure to continuous structure, and finally to elongated column, showing decreased structural size. Based on bulk density measurement, SEM and TG-DSC, it is known that the aerogels with 0.02 g CTAB (molar ratio CTAB/MTMS = 1.5 × 10−2) show the lowest density (0.079 g/cm3), highest porosity (96.1%), and thermostability up to approximately 490 °C.

•Hybrid aerogel based on organic and in-organic silicon source was prepared.•Hybrid aerogel was prepared under freezing drying.•The hybrid aerogel shows high thermal stability and low thermal conductivity.In this paper, hybrid silica aerogels were prepared by methltrimethoxysilane (MTMS) and water-glass co-precursor through two-step sol-gel process followed by freeze drying (FD). The characteristics of aerogels were strongly affected by the molar ratio of MTMS/Water-glass. When the molar ratio is 5.1, hybrid aerogel was obtained with good performances, such as low density (0.083 g/cm3), high contact angle (155.1°) and low thermal conductivity (0.0226 W/m·K). The density, contact angle and thermal conductivity of aerogels based on co-precursor are still showing excellent thermal stability with the same performances after 550 °C heat-treatment.Download high-res image (186KB)Download full-size image

•Fabrication of adiabatic foam using sodium silicate modified by boric acid.•High temperature, low boric acid content and low modulus of sodium silicate are helpful.•Thermal conductivity less than 0.044 W/m⋅K,density less than 100 kg/m3 and compression strength more than 0.7 Mpa.Adiabatic foam has been successfully prepared through sintering sodium silicate which is modified by boric acid. The effect of the sintering temperature, boric acid content and modulus of sodium silicate on the thermal conductivity, density, compression strength and microstructure of the adiabatic foam was studied in detail. In the sintering process, B3+ ion can take the place of the Si4+ ion by incorporating into the Si–O–Si structure via Si–O–B bridges, increasing the chemical stability of the adiabatic foam. High temperature, low boric acid content and low modulus of sodium silicate can reduce the thermal conductivity, density and compression strength. In order to meet the application of exterior wall thermal insulation, 450–500 °C of the sintering temperature, 18–24 g boric acid per 600 g sodium silicate solution, and 2.5–2.8 modulus of sodium silicate are chosen. The samples with thermal conductivity less than 0.044 W/m·K, density less than 100 kg/m3 and compression strength more than 0.7 MPa are obtained.

•Fabrication of adiabatic foam using sodium silicate and glass fiber.•Thermal conductivity is about 0.0454–0.0459 W/m K.•Density is about 74–80 kg/m3 and compression strength is about 0.42–0.46 MPa.•Thermal conductivity is more sensitive to glass fiber content.Fabrication of adiabatic foam by sodium silicate with glass fiber as supporting body was researched in this paper. The variation of the thermal conductivity, density, and compression strength with the sintering temperature, modulus of sodium silicate and glass fiber content were characterized. The results show that through sintering at 450 °C with 3.3 modulus of sodium silicate and less than 0.67 wt.% content of glass fiber, the adiabatic foam with 0.0454–0.0459 W/m K of thermal conductivity, 74–80 kg/m3 of density, and 0.42–0.46 MPa of compression strength can be obtained. Therefore, this adiabatic foam has a large potential of thermal insulation application.

•Thermal properties of MTMS/TEOS co-precursor aerogels were tailored successfully.•Thermal conductivity decreased linearly with the base concentration rising.•Specific heat presented a logarithmic reduction with the base concentration rising.•Thermal diffusivity retained the similar tendency to the porosity.•Thermostability was improved up to 508 °C with the rising base concentration.Methyltrimethoxysilane (MTMS) and tetraethoxysilane (TEOS) are used as precursors to synthesize MTMS/TEOS co-precursor aerogels (cp-aerogels) via ambient pressure drying (APD). The effects of NH3·H2O concentration on thermal properties of the MTMS/TEOS cp-aerogels were explored in detail. As the NH3·H2O concentration increased, the density slightly declined first and then dramatically ascended while the porosity presented an opposite trend. Meanwhile, the cluster size was minished and the pores became more abundant and uniform. These variations induced the changes of the thermal properties of the cp-aerogels. With the NH3·H2O concentration increasing, the thermal conductivity approximated linear decrease to 0.027 W m−1 K−1, the specific heat displayed a logarithmic reduction and the thermal diffusivity retained the similar tendency to the porosity. Furthermore, the thermostability was improved up to 508 °C with the increasing NH3·H2O concentration. All these results indicate that the thermal properties of the MTMS/TEOS cp-aerogels can be tailored by adjusting the NH3·H2O concentration.

In this paper, we have prepared methyltrimethoxysilane (MTMS)-based sponge-reinforced silica aerogel with low density through facile synthesis within 12 h. The sample’s mechanical property has been improved significantly compared with pure MTMS-based silica aerogel. The aerogels are hydrophobic and oleophilic. And its absorption capacity to the organic liquids is excellent. To overcome the low efficiency of traditional desorption methods (squeezing or distilling), the obtained sample is inserted by a stainless steel pipe which is connected to a pump. The novel design can realize the aerogels’ continuous absorption ability. The pumping rate is significantly affected by the aerogels’ pore size and the organic liquids’ viscosity, which is consistent with the simple proposed model in this paper. Such an apparatus means that a small piece of this sponge-reinforced silica aerogel can continuously collect a large area of floating oil from a water surface with high speed and efficiency.

Aramid fibers reinforced silica aerogel composites (AF/aerogels) for thermal insulation were prepared successfully under ambient pressure drying. The microstructure showed that the aramid fibers were inlaid in the aerogel matrix, acting as the supporting skeletons, to strengthen the aerogel matrix. FTIR revealed AF/aerogels was physical combination between aramid fibers and aerogel matrix without chemical bonds. The as prepared AF/aerogels possessed extremely low thermal conductivity of 0.0227 ± 0.0007 W m−1 K−1 with the fiber content ranging from 1.5% to 6.6%. Due to the softness, low density and remarkable mechanical strength of aramid fibers and the layered structure of the fiber distribution, the AF/aerogels presented nice elasticity and flexibility. TG–DSC indicated the thermal stability reaching approximately 290 °C, can meet the general usage conditions, which was mainly depended on the pure silica aerogels. From mentioned above, AF/aerogels present huge application prospects in heat preservation field, especially in piping insulation.

Porous anorthite ceramics with low thermal conductivity were successfully prepared using fly ash and gypsum by direct foaming and slip casting method. Effects of dispersant and foaming process on the performance of the porous materials were investigated. The results show adiabatic anorthite ceramics with the highest open porosity (94%) and the lowest thermal conductivity (0.042 W/m K) can be fabricated by adding 10% content of gypsum, 0.8% content of SHMP and using two-step foaming process. High porosity and small pore size are the main factors resulting in the low thermal conductivity. Meanwhile, the thermal conductivity can be predicted with the proportionality coefficient χ obtained by fitting the experimental data based on previous Gong's model. The a and b values in the expression of the proportionality coefficient χ were further discussed. The results show that they are affected by the pore size and distribution, and then the thermal conductivity will change accordingly.

•Large scale and monolithic sponge reinforced silica aerogels were prepared under ambient pressure.•The mechanical properties of as-prepared aerogels improved significantly.•Its absorption capacity of organic liquids is larger than those of pure silica aerogels.Silica aerogels (SA) with low density were reinforced with monolithic polyurethane sponge (PUS) using the sol–gel method at ambient pressure. The product (PUS reinforced SA) presents good features of high hydrophobicity and lipophilicity after the surface is modified by trimethylchlorosilane (TMCS). In the product, the nanoporous SA granules were held by the PUS skeleton. The SA has excellent absorptivity for various solvents and oils. Moreover, the aerogels demonstrate remarkable elasticity which overcomes the fragility of pure SA without PUS. Furthermore, the preparation process is also cost effective hence the PUS reinforced SA could be recommended as solvent/oil absorbent for the water pollution industry.

•Highly porous ceramic foams were firstly prepared by combining the direct foaming method and agar consolidation method, using fly ash as the raw material, which is economical, practical, environment friendly.•Meanwhile, the production of ceramic foams is a useful way of recycling large amounts of fly ash, which could efficiently resolve the disposal problem of fly ash.•Additionally, the change of thermal conductivity of highly porous ceramic foams along with different amounts of agar gelation agents was systematically researched.The ceramic foams with low thermal conductivity (0.0579–0.0826 W m−1 K−1) were successfully prepared by using fly ash as main raw material, combining direct foaming method and agar consolidation method. Additionally, the change of thermal conductivity of highly porous ceramic foams along with different amounts of agar gelation agents was systematically researched. The experimental results show that the samples with different amounts of agar gelation agents exhibit similar pore morphology. As the content of agar increased the pore size decreased first and then increased, but the porosity continued to decrease. Meanwhile, lower thermal conductivity was achieved with higher porosity, smaller pore size and more small pores of sintered product, but the porosity dominated.

The objective of the present study is to evaluate the elevated fires using the metrics of smoke distribution and changes in fire signals at the early stage, which affect activation of fire detectors. Most previous works on elevated fires in compartments are mainly concerned with physical phenomena of fully-developed fires. However, fire signals at initial 60 s are key parameters for aircraft cargo fire detection. A series of elevated fires were conducted in a simulated Boeing 737–700 forward cargo compartment. The fuel mass loss rate, the vertical and ceiling temperature, gas concentrations and relative humidity (RH) were measured. Results show that the smoke layer interface remains constant for various fuel pan elevation heights and no clear smoke stratification phenomenon is observed during the early stage, nevertheless, the first indication of smoke has been raised. The ceiling temperature rise is attenuated at different rates for various elevations with an exponential model proposed in ceiling temperature distributions for early stage fires. 60 s after ignition of the elevated fires, compared to non-elevated fires, CO/CO2 concentrations increase by at least 3.73/1.49 times and O2 concentration decreases by 2.5 times. The RH increases at the early stage. These experimental results can be used to inform the selection of optimum sensors, to develop appropriate detection algorithms and to optimize the number and location of fire detectors.

•Fabrication of dense cordierite ceramic through reducing Al2O3 mole ratio from 2.0 to 1.4 was studied, while the others fabricated dense ceramics by adding metal oxide or fine powders.•In this paper, changing the ratio of the starting materials themselves can fabricate dense cordierite ceramics.•At 1.4 Al2O3 mole ratio, the bulk density tends to the maximum value of 2.50 kg/m3.Dense cordierite ceramic was fabricated through reducing Al2O3 mole ratio from 2.0 to 1.4. The effect of the content of Al2O3 on crystalline phases, sintering characteristics and microstructures were studied. The green bodies, made of kaolin, attapulgite and basic magnesium carbonate, were sintered at 1200 °C. The result suggests that reducing the Al2O3 mole ratio can fabricate dense cordierite ceramic. At 1200 °C, cordierite became the main crystallization phase with a little of sapphirine. With the Al2O3 mole ratio decreasing, the shrinkage and bulk density increased but porosity reduced. When the mole ratio of Al2O3 reduced to 1.4 and sintered at 1200 °C, the bulk density tends to the maximum value of 2.50 kg/m3.

In a transportation hub complex (THC) in China, ticket entrance gates and station exits are common bottlenecks. Although road traffic in China follows right-hand traffic rules, the influence of right-hand traffic rules on the movement characteristics of pedestrians passing through such facility bottlenecks have been investigated rarely. In this article, simulation experiments are conducted to investigate the effect of THC bottle-necks on pedestrian movement characteristics given the existence of right-hand road traffic rules. Based on the use of a combination of histograms of oriented gradients and support vector machine algorithms, the movement behavior of pedestrians passing through multiple parallel bottlenecks are extracted. A total of 21 scenarios are considered in this simulation experiment, consisting of two-opening and three-opening parallel bottlenecks, where the width of each opening and width of the barriers between adjacent openings are varied. This study provides fundamental data for pedestrian flow passing through multiple parallel bottlenecks, data that can help identify important parameters for the design and improvement of many kinds of pedestrian flow management facilities. Results from the study also will be useful for the development and verification of evacuation models.

A novel application of correspondence analysis for identifying the relationships between fire loss and time, causes, and locations is proposed. The fire loss is divided into four levels which are [1, 1 k], [1 k, 10 k], [10 k, 100 k], and [100 k, ∞] Yuan (RMB) (1YUAN = 0.1647US, $), where 1 k equals to 1,000 Yuan. The results indicate that the loss levels have significantly related to months, time of day (hour), years, fire causes, and locations. Fires occurring in January, February, and June tend to be strongly associated with the loss level of [1, 1 k], while the loss level of [1 k, 10 k] is more likely to occur in May and August. It shows that September and December have strong relationship with the high loss level of [100 k, ∞]. Regarding the time of day, low loss level of [1, 1 k] is associated with the period from 10 a.m. to 10 p.m.; while high loss levels tend to occur between 2 a.m. and 6 a.m., the level of [1, 1 k] tends to be related to the causes of smoking, playing with fire, and others, while the level of [1 k, 10 k] is mainly caused by the electrical fire and spontaneous combustion. The locations of traffic, production operation places and commerce buildings, have been significantly related to high loss level. This paper introduces the application of correspondence analysis to fire losses, demonstrating the possibility of using CA to identify the relationships between fire losses and influencing factors. The achieved information can improve loss assessment of fires at a given time or location.

Porous mullite ceramics were prepared from an industrial grade mullite powder by foaming and starch consolidation. The viscosities of the original suspensions and the foamed ones with solid loading of 62.5 and 67.5 wt% were measured. After the steps of forming and drying, the green bodies were sintered under different temperatures from 1,200 to 1,600 °C for 2 h. The influence of solid loading of suspension and sintering temperature on the porosity and compressive strength was evaluated. The sintered mullite ceramics, with porosity from 86 to 73 vol% and corresponding compressive strength from 1 to 22 MPa, contained a multi-modal microstructure with large spherical pores and small pores on internal walls. Thermal conductivity measurement carried out by the transient plane source technique at room temperature resulted in values as low as 0.09 W/mK. In addition, the relationship between thermal conductivity and porosity was discussed in detail.

To provide a view of countries’ relative fire protection efficiency from an international perspective, this study conducted an evaluation of fire protection performance of eight countries (i.e. Denmark, Japan, Norway, Singapore, Slovenia, Sweden, United Kingdom, and United States) based on the fire statistics from 2000 to 2008 released by the World Fire Statistic Center. Three inputs and two undesirable outputs were determined. After applying a transformation to both undesirable outputs, the overall efficiency and pure technical efficiency were acquired using two basic models of data envelopment analysis, respectively. Thereafter, the scale efficiency was calculated and the results were analyzed. It indicates that international technical exchange and cooperation in fire protection are needed for these eight countries. According to their status, Singapore and Slovenia could be set as good examples; Denmark, Norway, and United Kingdom need to reallocate their resources and refine the operation mode; United States should reduce the scale properly; Japan and Sweden need both scale increase and technique adjustment. An increasing trend is believed to exist for the OTE, PTE, and SE means of countries. However, further work is needed to improve and enlarge the dataset to obtain more accurate, wide, and applicable results.

Focusing on the high casualty fires (HCFs), an analytic network process (ANP) approach was proposed for rapid loss assessment. The networks of situation index (SI) and consequence index (CI) were built. A dataset of 469 HCF cases in China from 2002 to 2010 was established. The relative weights of all attributes and the values of CI and SI were calculated and analyzed. The results show that the casualty factors should be emphasized in loss assessment by CI. The elements of day, hospital, and smoking are most likely to cause huge loss for the attributes of time, place, and cause in the SI network, respectively. The correct classification rates of accident level were compared between ANP, multinomial logistic regression, multi-layer perceptron network, and radial basis function network. It is indicated that ANP performs best for HCFs of the high and extreme level or when the influence of accident level is considered. The relationship between CI and SI for HCFs of the high and extreme level was obtained by the weighted least square based polynomial fitting and can be used to generate meaningful results of extreme possibility for decision making.

Experiments and research on heat transport through firefighting protective clothing when exposed to high temperature or intensive radiation are significant. Phase change material (PCM) takes energy when changes from solid to liquid thus reducing heat transmission. A numerical simulation of heat protection of the firefighting protective clothing embedded with PCM was studied. We focused on the temperature variation by comparing different thicknesses and position conditions of PCM combined in the clothing, as well as the melting state of PCM and human irreversible burns through a simplified one-dimensional model. The results showed it was superior to place PCM between water and proof layer and inner layer, in addition, greater thickness increased protection time while might adding extra burden to the firefighter.

•Using fly ash as main material to reduce its environmental endanger.•Combination of foaming and slip casting method.•Effects of some factors on the properties of the material.•Thermal conductivity as low as 0.0511 W/(m K).•Comparison of some traditional and innovative insulating materials.The paper introduces a new kind of thermal insulation material using coal fly ash as main raw material by the method of foaming and slip casting process. The foaming ability of the suspensions with solid loading of 30, 35 and 40 wt% at different foaming agent additive levels were measured. The green bodies were then sintered under different sintering temperatures from 850 °C to 1000 °C for 2 h following the steps of foaming and drying. Effects of solid loading of suspensions and sintering temperature on the porosity, compressive strength and thermal conductivity were investigated. The sintered bodies, with porosity from 86.3 vol.% to 94.5 vol.% and compressive strength from 0.43 MPa to 1.01 MPa, contained spherical pores with no preferred orientation. The thermal conductivity of the sintered thermal insulation material, measured by the transient plane source (TPS) at room temperature, could reach as low as 0.0511 W/(m K). As an environmental friendly material, it is suitable for wall application to save energy.

A better understanding of terrorist attacks and the relationships between the fatality and the influencing factors is helpful to improve the decisions to allocate resources in the fight against terrorism. The fatality is divided into four levels: 1-2, 3-9, 10-29 and ≥30. The article uses a novel approach of correspondence analysis to explore the associations between terrorist attacks and factors. The fatality level of terrorist attacks is influenced by countries, regions, weapons, attack types and targets. The factors that tend to result in high fatality levels are identified. The attacks occur in developing countries and regions are associated with fatality level of ≥30 while the developed countries such as the North America and Western Europe tend to be related with low fatality level. The attacks caused by the weapons of Incendiary and WMD (Biological, Chemical, Radiological, Nuclear) tend to precipitate a relatively high fatalities. The attack types of Hijacking, Barricade Incident and Facility/Infrastructure Attack have strong relationships with fatality level of ≥30. Compared to other targets, Airports & Airlines and Maritime are more likely to generate extremely high fatalities. The results are useful for understanding the fundamental cause of fatalities in terrorist attacks.

Wire and cable fire has become the major cause of fire disaster in China. Effective evaluation and analysis of the flammability of cables are critical for developing new flame retardant cable materials by the industry and testing cables which have already been used in the market. Due to the complex internal structure of cable, it is difficult to investigate the complete pyrolysis and combustion of the cable sheath by using the Cone calorimeter and full-scale experiment. The recently developed pyrolysis combustion flow calorimeter (PCFC) is able to measure the vital information for evaluating the flammability of cable sheath using samples of milligram size. The current study aims to assess the flammability of eight samples of seven kinds of cables that are widely used in China using PCFC. The three important parameters related to fire hazard of materials, namely the heat release rate (HRR), ignition temperature (IT) and total heat release (THR), were measured and analyzed. Detailed differences in flammability among the eight samples were differentiated by PCFC.

High-casualty fires (HCFs) involving ≥ 3 fatalities derived from the Fire Statistical Year Book of China and Chinese Fire Services from 2002-2010 were analyzed. The aim of this study was to investigate the time-scaling properties of HCFs. The time-scaling properties were detected by means of Fano Factor (FF), Allan Factor (AF) and detrended fluctuation analysis (DFA). The results of FF and AF show that the HCF sequences with death ≥ 3 and death ≥ 4 exhibit obvious time scaling behavior after the fractal onset times. The scaling exponents of FF and AF decrease significantly with increasing fatality, which reflects that HCF sequences with more fatalities tend to behave as Poisson process. The sequence of HCFs with death ≥ 6 can be considered as a Poisson process according to the comparison of FF (AF) curve and Poissonian 95% confidence curve. The DFA scaling exponent of HCF sequence involving fatality ≥ 3 is approximate 0.551±0.005, indicating that this sequence exhibits long-range correlations. With the increase of fatality threshold the DFA scaling exponent gradually decreases to about 0.5, which reflects that the HCFs with high fatality levels are likely to be uncorrelated. Furthermore, the sequence of HCFs with death ≥ 6 can be regarded as uncorrelated because its DFA scaling exponent is 0.496±0.003.© 2013 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the Asia-Oceania Association for Fire Science and Technology.

The objective of this study is to explore the associations between the fire causes and the influence factors that include provinces, months, hours, building types and places. The fire causes that are obtained from China fire statistics are composed of arson, electric, production, careless with fire, smoking, playing with fire, self-ignite, unknown and others. The results show that the tendency of fire causes of various provinces is different. Fires occurred in January and February is trend to be strongly associated with playing with fire. The difference of fire causes between night and daytime is obvious. It is clear that the daytime trend to be associated with smoking, careless with fire, production operation and playing with fire, while the night group trends to be associated with arson, unknown, others, electrical fire and self-ignite. It is shown that significant differences of fire causes exist among the building types and the places. Multi-storied buildings have close association with electrical fire. Personnel crowded places are trend to be associated with electrical fire while the vehicles are trend to be associated with self-ignite. Finally, the study highlights that correspondence analysis is an appropriate technique to explore the relationships among fire statistics data and can play a complementary role in analyzing fire data.

This study examines smoke control capacity of impulse ventilation system (IVS) in an underground car park. An analysis is made in relation to important parameters including jet fan number, jet fan velocity, extract rate and system robustness on fire position. The comparison with ductwork system is also performed to determine the different effect of smoke control between two systems. Fire Dynamic Simulator version 5.30 is applied to simulate 10 scenarios in a 80 m long, 40 m wide and 3.2 m height domain witha fire source simulating a car fire with an peak heat release rate of 4 MW. Results show that impulse ventilation system not noly prohibit fire smoke spreading but also maintain a good visibility providing clear access for fighters. However it may cause temperature rise on the downwind zone of fire source with a maximum value between 80-100 and fire plume e tilt. Smoke control capacity of impulse ventilation system is sensitive to jet fan numbers. Too high jet fan velocity may cause severe smoke recirculation. Increment in extract rate is conductive to relay jet flows. An impulse ventilation system can effectively control smoke movement and induce smoke to extract points under two typical different fire locations, which is of great practical importance. Impulse ventilation system seems superior to ductwork system in maintaining high visibility.

This study examines smoke control capacity of impulse ventilation system (IVS) in an underground car park. An analysis is made in relation to important parameters including jet fan number, jet fan velocity, extract rate and system robustness on fire position. The comparison with ductwork system is also performed to determine the different effect of smoke control between two systems. Fire Dynamic Simulator version 5.30 is applied to simulate 10 scenarios in a 80 m long, 40 m wide and 3.2 m height domain witha fire source simulating a car fire with an peak heat release rate of 4 MW. Results show that impulse ventilation system not noly prohibit fire smoke spreading but also maintain a good visibility providing clear access for fighters. However it may cause temperature rise on the downwind zone of fire source with a maximum value between 80-100 and fire plume e tilt. Smoke control capacity of impulse ventilation system is sensitive to jet fan numbers. Too high jet fan velocity may cause severe smoke recirculation. Increment in extract rate is conductive to relay jet flows. An impulse ventilation system can effectively control smoke movement and induce smoke to extract points under two typical different fire locations, which is of great practical importance. Impulse ventilation system seems superior to ductwork system in maintaining high visibility.

•A series of CH3N5-Sr(NO3)2 propellants catalyzed by TMOs are synthesized.•TMOs added into CH3N5-Sr(NO3)2 propellants decrease flame temperature, increase combustion stability and burning rate.•The decomposition mechanism of CH3N5-Sr(NO3)2 propellants has been proposed.•TMO influencing reaction pathway of propellant’s combustion is reflected not only in condensed phase but also in gas phase.In firefighting area, the novel CH3N5-Sr(NO3)2 is of growing interest as solid propellant gas generating agent. However, undesirable reaction temperature and burning rate of CH3N5-Sr(NO3)2 limit their applications to fire-fighting systems, which forces fire researchers to find more fitting ingredient proportions or burning rate catalysts. This paper presents a detailed experimental study adding nanosized metal oxides (Fe2O3, CuO, and NiO) effects on CH3N5-Sr(NO3)2 burning behaviors, including thermal analysis, scanning electron microscopy, specific surface area measurement, and thermal conductivity test. Results show, the additions of transition metal oxides (TMOs) increase the burning rate of the CH3N5-Sr(NO3)2-based propellants and decrease reaction temperature. The modifying effects of TMOs on combustion behavior alter both the condensed phase and gas phase reactions in a synergistic manner. The novel propellant formulation has shown a superior property to promote CH3N5-Sr(NO3)2-based propellants’ application into fire-fighting area.