Heat release rate determination of pool fire at different pressure conditions

This research deals with the experimental determination of the heat release rate (HRR) of n‐heptane pool fire at different pressure conditions based on oxygen consumption method. The method, initially developed for open atmosphere fires, is modified for pool fires in ventilated chamber under different pressure conditions. The calculation equation of the HRR with consideration of ambient pressure is presented. The experiments are performed in the large‐scale ventilated altitude chamber of size 2 × 3 × 4.65 m under series of pressure, 24, 38, 64, and 75 to 90 kPa. Based on the experimental data, the effects of pressure on the mass burning rate and HRR are discussed; meanwhile, the calculation method of HRR is verified. The results show that the mean mass burning rate at the steady burning stage increases exponentially with pressure as , with α = 0.68. The maximum HRR increases from 27 to 63 kW as the pressure rises from 24 to 90 kPa. It is concluded that the ambient pressure has a significant effect on the fire HRR and will further influence on other fire parameters.     

Experimental determination of fire heat release rate with OC and CDG calorimetry for ventilated compartments fire scenario

This research deals with the experimental determination of the heat release rate (HRR) of fires in mechanically ventilated compartments based on oxygen consumption (OC) and carbon dioxide generation (CDG) calorimetry. It proposes formulations for fire in force‐ventilated compartments on the same basis as the relations established for hood calorimetry in an open atmosphere but considering inertia and unsteady behavior of the fire via the time variation mass of O₂ and CO₂ in the compartment. The value of the new formulations of HRR has been tested in two series of propane gas fire experiments performed in a large‐scale facility. The first series involves a fire scenario with one compartment, and the second series, a fire scenario with three compartments connected to each other by doorways. In the first test series, the OC and CDG formulations for HRR are assessed. In the second test series, the OC and CDG formulations are presented with two approaches to definition of the control volume: approach involving three rooms and the flow rate in the ventilation network and approach involving only the fire room and the flow rate through the doorways. On the basis of the fire experiments considered, the most accurate method (accuracy to within 10%) for determining the HRR is the CDG formulation with approach for the control volume without considering the flow rates at the doorways. This analysis points out the different features of each method (OC and CDG) and thoroughly discusses their advantages and drawbacks. The overall analysis allows guidelines to be formulated for fire HRR calculation in confined and ventilated compartments. Copyright © 2013 John Wiley & Sons, Ltd.     

A guide to characterizing heat release rate measurement uncertainty for full‐scale fire tests

Accurate heat release rate measurements provide essential information to defining the fire safety characteristics of products. The size, complexity, and cost of full‐scale fire tests make achieving accurate and quantitative results a serious challenge. A detailed uncertainty analysis of a large‐scale heat release rate measurement facility is presented as a guide to the process of estimating the uncertainty of similar facilities. Quantitative heat release rate measurements of full‐scale fires up to 2.7 MW were conducted using the principle of oxygen consumption calorimetry. Uncertainty estimates were also computed for the heat input measurements from a well‐controlled natural gas burner. The measurements of heat input and heat release rate were performed independently, and the discrepancy between the two was well within the uncertainty limits. The propagation of uncertainty was performed at the level of voltage and temperature measurements, which avoided using mutually dependent measurement parameters. Reasons for the significant contribution to the combined uncertainty from the oxygen concentration and exhaust flow measurements are demonstrated. Also presented is a first‐order effort to account for the uncertainty due to factors in full‐scale fire tests such as operator error and environmental influences that are not modeled by the heat release rate equation. Published in 2008 by John Wiley & Sons, Ltd.     

Investigation of a combustible material in the fire of Hengyang merchant's building

Agaric, a kind of important combustible material in the fire of Hengyang merchant's building, was investigated using different experiment equipments. Its degradation and pyrolysis behavior were studied by means of thermogravimetric and kinetic analysis and pyrolysis gas chromatography–mass spectroscopy analysis. External radiation heat and internal heat were used to ignite the agaric. For external radiation ignition, a series of bench‐scale fire tests were done in cone calorimeter in accordance with ISO 5660. As for the internal heat ignition, a fire test was carried out in a full‐scale room in accordance with ISO 9705. Multi‐parameter measurement, including heat release rate (HRR), mass loss rate (MLR), temperature field and species concentration, has been accomplished. Meanwhile, the process of a full‐scale fire test was numerically simulated. The computational results were consistent with experiment data, which will lay down a good foundation for further study in fire reconstruction of the whole fire. Copyright © 2008 John Wiley & Sons, Ltd.     

Modified carbon‐dioxide measurement to predict the heat release rate of fire burning in a compartment based on the three‐zone model

The heat release rate (HRR) of fuels has been described as the single important variable of fuels in fire hazard, and the HRR experimental measurement remains a key issue in fire science. A modified carbon‐dioxide generation (CDG) method, applying a three‐zone smoke model, is developed to predict the HRR of gas, liquid, and solid fuel fires. The three‐zone smoke model with three layers is determined by the vertical thermal stratification, and their physical thermal properties are computed. The application of modified method on typical gas fuel, liquid fuel, and simple solid‐fuel fires is verified. The prediction accuracy is examined quantitatively by the cosine similarity comparison of predicted results with the experimental data. In addition, the ventilation effects on the predicted results are also explored. Results show that the application of three‐zone model improves the HRR prediction accuracy, because it can accurately capture the mixing behavior from the upper layer to the lower layer. The effect of ventilation on modified CDG method is positive as the ventilation enhances the smoke mixing and the smoke distribution in each layer is relatively uniform.     

Effectiveness of impregnation of ammonium polyphosphate fire retardant in poplar wood using microwave heating

Poplar samples were impregnated with ammonium polyphosphate fire retardant at various pressures and durations after they were pretreated with microwave heating. The effects of the pressure and duration on the flame‐retardation and smoke‐suppression properties were investigated with cone calorimeter analysis. The peak heat release rate (pk‐HRR), total heat release (THR), and total smoke product (TSP) of treated woods were measured for samples of pretreated and untreated with microwave. After the impregnation, the poplar wood showed the significant improvement in its fire resistance. Compared with non‐impregnation wood, the pk‐HRR, THR, and TSP of wood impregnated with ammonium polyphosphate at pressure of 0.4 MPa and duration of 10 min were 48.29%, 35.58%, and 68.64% less, respectively. The pk‐HRR, THR, and TSP of microwave pretreated wood was 15.89%, 5.69%, and 13.59% less than those without microwave pretreated sample. The microwave pretreatment of wood can increase fire retardant effectiveness of ammonium polyphosphate‐impregnated wood. Copyright © 2015 John Wiley & Sons, Ltd.     

Fire calorimetry relying on the use of the fire propagation apparatus. Part II: burning characteristics of selected chemical substances under fuel rich conditions

The paper focuses on the detailed characterization of ventilation controlled fires of industrial products that are likely to govern accidental fire scenarios in fire resistant enclosures. Results regarding under‐ventilated fires of substances that are not polymers are presented to illustrate the capability of the fire propagation apparatus (FPA) to qualify such types of fires. Based on results from heptane fire tests in both well‐ and under‐ventilated fire conditions, a set of recommendations was previously provided in order to check the validity of the experimental results. The application of these recommendations is illustrated for the selected liquid substances containing hetero‐atoms. It emerges that the fire propagation apparatus assesses quite easily the performance of well‐controlled fires in both well‐ and under‐ventilated conditions. Another major outcome of our work is that the potential of the FPA has the capability to address fire issues outside the conventional use of the equipment, in particular to qualify the burning behaviour of chemicals on the full spectrum of ventilation conditions. Copyright © 2005 John Wiley & Sons, Ltd.     

Experimental investigation on smoke spread characteristics and smoke layer height in tunnels

A series of experiments were carried out in a model‐scale tunnel with dimension of 6.0 m × 1.0 m × 0.7 m to investigate the smoke spread behaviors and the typical smoke layer height. Alcohol was employed as fuel, and the heat release rate was set to be 9.5, 18.4, 30.1, and 63.5 kW, respectively. The temperature profile in the tunnel was measured, and the buoyant flow stratification conditions were visualized by a laser sheet. The experiment results show that the N percentage rule would greatly influence by subjective factors. As the N (10, 20, 30) value increases, the smoke layer height also increases. The results calculated by the buoyancy frequency method were more accurate. Fan's prediction method (Fan WC, Wang QG, Jiang FH. Concise Guide of Fire Science. He Fei: University of Science and Technology of China Press; 1995.161 p.) does not accurately evaluate the smoke layer thickness in tunnel fire. An enhanced empirical formula for predicting the smoke layer thickness in the one‐dimensional horizontal spread stage was proposed. It is shown that the empirical formula could well predict the smoke layer thickness by comparing with the experimental data of previous studies.     

Heat release rates of modern residential furnishings during combustion in a room calorimeter

Results are presented from a number of fire experiments that were conducted in a room environment to study the fire characteristics of typical residential furnishings and assist in the design of a subsequent phase of a project involving fully furnished room fire experiments. The experiments were conducted in a 16‐m² test room (with dimensions 3.8 m wide × 4.2 m long × 2.4 m high), which had a 1.5 × 1.5‐m window opening. The furnishings tested included mattresses, bed clothes, bed assemblies, upholstered seating furniture, clothing arrangements, books, plastic audio/video media and storage cases, toys, shoes, and a computer workstation setup. The smoke (gaseous products of combustion) from the room was collected using a hood system in order to measure the heat release rate (HRR) and optical density of the smoke. The test room was instrumented with load cells, heat flux gauges, thermocouples and velocity probes in order to take the following measurements: mass loss, total heat flux on gauge‐installed flush with the internal surfaces (floor, walls, and ceiling), temperatures at numerous locations, and gas velocities in the window opening. Twin‐size mattresses produced peak HRRs of approximately 3800 kW, and the maximum room temperature was approximately 980°C. The HRRs of bed assemblies of various sizes and configurations ranged from 1800 kW for a twin‐size bed to 6250 kW for a bunk bed. The maximum temperature and heat flux recorded in the experiments were 1071°C and 221 kW/m², respectively. Upholstered chairs and sofas had HRRs ranging from 630 kW for an ottoman to 3360 kW for a two‐seat sofa. In tests with clothing, toys, shoes, books, a computer workstation, and CD/DVD media, the peak HRRs ranged from 440 kW for a bookcase to 2045 kW for toys. Furnishings containing a large proportion of rigid thermoplastic plastics, such as shoes and media cases, produced very dense smoke even at low HRRs. The effect of parameters such as bed clothes, mattress type, foundation type, bed assembly and chair size, material composition, and fuel package arrangement was evident in the results. Because the room dimensions and wall lining materials remained constant, temperatures were linearly proportional to the peak HRR (and exposure time) until the ventilation limit (approximately 4100 kW) was reached. Copyright © 2014 John Wiley & Sons, Ltd.     

Experimental study on fire properties of interior materials used in low‐floor light‐rail trains

In this work, cone calorimeter tests were conducted to investigate fire properties of interior materials (floor covering [FC], aluminum plate covered with paint [APCP], light diffuser [LD], and gel coat [GC]) used in low‐floor light‐rail trains. Ignition time (t_ig) of each material decreases with the increase of radiative heat flux. The decreasing order of the four samples by ignition time under the same radiative heat flux is LD > APCP > FC > GC. The heat release rate (HRR), peak value of HRR (PHRR), time from ignition to PHRR (t_p), fire growth rate index (FIGRA), and fire growth index (FGI) rise with the increasing radiative heat flux. For the FC, LD, and GC, single HRR peak is observed in the HRR history while three peaks are observed for APCP. For PHRR, LD > FC > APCP > GC, while for t_p, GC < FC < APCP < LD. Under most conditions, the FIGRA and FGI of the FC is the highest among the four materials. Results of this work are beneficial to evaluate fire hazard of low‐floor light‐rail train and determine the emphasis of fire prevention.     

Steady heat release rate by the moment–area method

A simple mathematical procedure is described for computing temporal averages of heat release rate (HRR) data from the moments and area of the history. The moment–area method was used to calculate average HRRs for over 200 specimens having a wide range of chemical composition and sample thickness tested on a bench‐scale fire calorimeter at various external heat fluxes. The average values of HRR obtained by the moment–area method are essentially independent of sample thickness and are potentially useful for ranking material flammability and determining material combustion properties. Published in 2007 by John Wiley & Sons, Ltd.     

Design car fire size based on fire statistics and experimental data

Passenger vehicle fires present a significant fire hazard in enclosed car parks. Accordingly, this hazard is often used as a design fire scenario for the application of fire protection systems. Specific fire protection standards, like NFPA 88A:2019 and NFPA 502:2020 in the United States (US) or BS 7346-7:2013, NBN 21-208-2:2014, VDI 6019-1:2006, NEN 6098:2010 and ITB 493:2015 in Europe, provide varying requirements for car park fire protection. Car parks fire strategies, especially when smoke control systems are used, often make use of performance-based methods, in which fire growth (ie, heat release rate [HRR]) plays a fundamental role. The chosen HRR can influence the specification of car park construction and on smoke control system calculations. This article presents a review of 44 full-scale car fire tests together with Polish and British passenger car fire statistics from the last 8 years. Based on the collected data and the averaged tests, HRR values provided in this article could assist local authorities and stakeholders determine optimal fire safety design criteria for car parks.     

Comparison of simulated wet bench fires with small‐ and intermediate‐scale fire tests

Fire hazard studies of clean room facilities indicated that significant losses due to fire may occur in the semiconductor industry. The present study reports the results of full‐scale wet bench fire tests conducted (1) to assess the fire hazards of existing wet bench materials not meeting the listing requirement of NFPA 318, (2) to assess the impact on wet bench fires of engineered materials with improved flammability characteristics, and (3) to compare the observed fire behavior with the results of simpler small‐ and intermediate‐scale fire tests using the same materials. The full‐scale wet bench fires were observed to be consistent in terms of chemical heat release rate, fire propagation, and smoke generation with the results of the small‐ and intermediate‐scale test results. The simpler fire tests are incorporated in FM Approvals 4910 certification for materials to be used in semiconductor fabrication facilities. The small‐scale test protocol is also standardized in NFPA 287. Copyright © 2008 John Wiley & Sons, Ltd.     

Experimental study of the combustion characteristics of methanol‐gasoline blends pool fires in a full‐scale tunnel

The combustion characteristics of methanol‐gasoline blends pool fires were studied in a series of full‐scale tunnel experiments conducted with different methanol and gasoline blends. The parameters were measured including the mass loss rate, the pool surface temperature, the fire plume centerline temperature, the ceiling temperature, the smoke layer temperature profile, the flame height, and the smoke layer interface height. The gasoline components were analyzed by GC‐MS. The effects of azeotropism on the combustion characteristics of the different blends were discussed. On the basis of the results of the fire plume centerline temperature, the ceiling temperature, and the flame height, it shows that the tunnel fire regime gradually switches from fuel controlled to ventilation controlled with increasing gasoline fractions in the blends. The fire plume can be divided into 3 regions by the fire plume centerline temperature for the different blends. The N‐percentage rule to determine the smoke layer interface height is found to be applicable for tunnel fires with different blends for N = 26.     

Enhancement of fire retardancy properties of glass fibre–reinforced polyesters composites

This paper presents the results of an experimental investigation on the fire retardancy properties of glass fibre–reinforced polyester (GFRP) composites with bisphenol‐A vinylester and isophthalic polyester as matrices and low electrical conductivity E‐glass fibres as reinforcement. The fire protection systems tested were alumina trihydrate (ATH), decabromodiphenyl ether (DBDE), and antimony trioxide (Sb₂O₃). A mass loss cone calorimeter was used to obtain the properties of heat release rate (HRR), peak HRR, total heat released, total mass loss, time to ignition, and time of combustion. Moreover, limiting oxygen index (LOI), UL‐94, and glow‐wire tests were also performed. The fire tests were carried out in order to investigate if the combination of ATH and DBDE could have “additive,” “antagonistic,” or “synergistic” effects on the flame retardant properties of the GFRP studied in this work. In addition, the influence of the ATH content variation on flame retardant properties was also evaluated. The results indicate that the sole addition of ATH at 47.7 phr could lead to the complete inhibition of the composites ignition, while the materials containing DBDE exhibit ignition and flame propagation in the cone calorimeter test.     

Poly(vinyl chloride) and its fire properties

This work provides an up‐to‐date review of the fire properties of poly(vinyl chloride) (PVC) materials, both rigid (unplasticized) and flexible (plasticized). The fire properties addressed include ignitability, ease of extinction (oxygen index), flame spread (small scale and intermediate scale), heat release, smoke obscuration, smoke toxicity, hydrogen chloride emission and decay, and performance in real‐scale fires. This comprehensive review includes a wide selection of references and tables illustrating the properties of PVC materials in comparison with those of other polymeric materials, including, in many instances, wood materials. The work puts these fire properties in perspective, showing that the heat release rate (the key fire property) of rigid PVC (and that of properly flame‐retarded flexible PVC) are among the lower values found for combustible materials. This work also shows that the smoke toxicity and smoke obscuration resulting from burning PVC materials in real‐scale fires is in the same range as those of other materials.     

An experimental and modeling study of heat radiation characteristics of inclined ceiling jet in an airplane cargo compartment

A series of pool fires were carried out in an airplane cargo compartment to investigate the effect of the pressure on the heat radiation flux (HRF) of the inclined ceiling jet fire. During the tests, different static chamber pressures ranging from 50 to 101 kPa were controlled by the air flow in and out; both free fire and inclined ceiling jet fire were conducted with five different heat release rates (HRRs), which were produced by a 17‐cm square porous gas burner using propane as fuel. Vertical flame temperature, thermal plume temperature beneath the inclined ceiling, and HRF to the horizontal floor were measured and analyzed; at the same time, the flame shape was recorded by a video. It was found that the HRF was increased with the HRR, and there was a sudden rise for these fire impinging on the ceiling. The flame radiation fraction had a weak correlation with the environment pressure, while the flame emissivity was increased with the increasing ambient pressure. Besides, on the basis of the assumption that the flame emissivity is equaled in both free flame and the inclined ceiling jet fire, HRF calculated model was established and compared with the experimental results.     

Mathematical modelling of fire development in cable installations

In 1996 DG XII of the European Commission (Research and Development) approved a 3 year project on the fire performance of electrical cables. Within this FIPEC project, a major part of the work involved correlation and mathematical modelling of flame spread and heat release rate in cable installations. The FIPEC project has developed different levels of testing ranging from a small‐scale, cone calorimeter test procedures developed for cables and materials, a full‐scale‐test procedure based on the IEC 60332‐3, but utilizing HRR and SPR measurements, and a real scale test conducted on model cable installations. Links through statistical correlations and mathematical fire modelling between these levels were investigated and the findings are presented in this paper. These links could form the scientific foundations for standards upon which fire performance measurements can be based and for new fire engineering techniques within fire performance based codes. Between each testing level correlation, numerical and mathematical models were performed. All of the models were based on the cone calorimeter test method. The complexity of the models varied from correlation models to advanced physical pyrolysis models which can be used in CFD codes. The results will allow advanced prediction of cable fires in the future. Also a bench mark was established for the prediction of cable performance by means of data obtained from the constituent materials. Copyright © 2002 John Wiley & Sons, Ltd.     

Experimental investigation into the influence of ignition location on flame spread and heat release rates of polyurethane foam slabs

This study presents the results from a set of 11 large‐scale open fire tests performed on flexible polyurethane foam slabs/mattresses. The purpose of the study was to investigate the influence of the ignition location on the fire behaviour of the foam slabs and to generate data on a highly characterised material that could be used for modelling work in the future. A method for obtaining spatially resolved flame spread data for this type of material was presented using a gridded array of 5 × 10 thermocouples placed on the underside the foam slab and from this, flame spread was examined using three different approaches. The heat release rate (HRR) results showed clear shapes forming that were dependent on the ignition location, with two distinct behaviours being observed between the various different ignition locations, this was also observed in the calculated flame spread rate (FSR) data. Results within an individual test, showed the calculated range of FSRs over the geometry of the slab varied between approximately 1 and 8 mm/s depending on the ignition location. The average FSR values between tests varied between 3 and 7 mm/s and the maximum and minimum values were calculated to be approximately 11 and 2 mm/s respectively.     

Fire calorimetry relying on the use of the fire propagation apparatus. Part I: early learning from use in Europe

The fire propagation apparatus (FPA) is the bench scale fire calorimeter that was recently described in its updated version in ASTM E 2058. The apparatus was originally developed in the USA by Tewarson and co‐workers from the mid 1970s, under the name ‘50 kW lab‐scale flammability apparatus’, and is therefore still known in Europe as the ‘Tewarson apparatus’. The paper focuses on the experience achieved so far with the first modern version of the apparatus implemented in Europe (France). Part I in this series of articles reports on the main results achieved during the commissioning period of the apparatus. In a first step, preliminary experiments were carried out in order to check and calibrate different sub‐equipment of the calorimeter. The results are principally presented for the load cell system and the infrared heating system which are essential pieces of sub‐equipment. In a second step, a set of fire tests using methane or acetone as fuel was carried out in order to check and calibrate the overall working of the calorimeter in well‐fire conditions. The performance of the calorimeter was also checked when it operates in under‐ventilated fires. Relevant testing procedures and potential technical problems are discussed. A set of recommendations are derived from the early learning obtained at the INERIS fire laboratory in order to check the consistency of the results obtained from bench‐scale fire tests. These recommendations are thought to be applicable to all types of bench scale fire calorimeters. Copyright © 2005 John Wiley & Sons, Ltd.