Full-scale Burning Tests Research Articles

A feasible heat release rate estimation approach for fire hazard assessment in green design

New energy harvesting systems in buildings are becoming more attractive in new green buildings. However, the potential fire hazard of the combustible items used in new green building limits their wider application. Fire behaviour of combustible items in new green designs should be studied carefully. Heat release rate of burning combustible items of different materials is important in fire hazard assessment and can be estimated by oxygen consumption calorimetry. An exhaust hood with a fan-duct system was built to collect flue gas. As the burning was likely to be incomplete in building fires, carbon monoxide, carbon dioxide, water vapor and soot would be emitted. Heat release rates of combustible items were estimated by measuring the transient amount of oxygen, carbon monoxide and carbon dioxide collected by the hood. Based on mass balancing, there are at least three equations in terms of mass flow rates of oxygen, carbon monoxide and carbon dioxide in the incoming air and exhaust gas. There are always questions about using which equations because measuring gases in full-scale burning tests is difficult and expensive. These three equations are introduced and compared in this paper. Heat release rates of four selected combustible items were studied as an example case. Accuracy of the results based on the measured oxygen concentration only was similar to the values provided by commercial software. Results from the experimental data are useful in further full-scale burning tests on combustible items in energy harvest systems planning at the moment.

Analyzing Combustion Efficiency According to Spray Characteristics of Gas-Centered Swirl-Coaxial Injector

The momentum flux ratio (MFR) significantly affects the mixing characteristics and combustion efficiency of propellants in rocket engine injectors. The spray characteristics of three gas-centered swirl-coaxial injectors used in a full-scale combustion test were investigated according to the change in the momentum flux ratio. The difference in combustion efficiency was analyzed through the comparison with combustion test results using spray visualization and quantification. The spray cross-sectional shape and droplet distribution were measured using a structured laser illumination planar imaging technique. As the swirl effect was more apparent at a low MFR, the flow rate of the liquid that was sprayed outside was high. The flow rate of the liquid sprayed around the gas injection increased with the MFR. The Sauter mean diameter (SMD) of each injector liquid spray was obtained using the laser shadow imaging method. The SMD decreased as the MFR of all injector types increased, and the injector with a high liquid flow rate and small SMD injected towards the gas center exhibited higher combustion efficiency than the injector with a dominant liquid spray and the large SMD at a large injection angle. The outcomes of the study could help contribute to the increase in the combustion efficiency of the full-scale staged combustion cycle engine combustor.

Desirable Coal Quality for a 660 MW Benson Boiler's Full-Scale Combustion Tests and Related Emissions

Desirable Coal Quality for a 660 MW Benson Boiler's Full-Scale Combustion Tests and Related Emissions

Upgrading of fire safety requirement for tall buildings in Bulgaria and proposal of implementing fire safety management under facility management

PurposeThe purpose of this paper is to check and fill the gap between the existing fire safety regulations for newly built tall buildings in Bulgaria and those in areas with rapid economic growth in the Asia-Oceania regions like the Hong Kong Special Administrative Region and Mainland China, by making comparative analysis and identifying good practices. The main focus is on the development of fire safety designs, facilities and management, which shall be recognized as essential parts of facility management in tall buildings.Design/methodology/approachBulgarian regulations are analyzed and then compared with those in the Hong Kong Special Administrative Region and Mainland China. In addition, the scientific aspect of fire load density in the fire codes is discussed. The possibility of implementing a fire engineering approach to supplement prescriptive codes is outlined. The essential roles of fire safety management and fire safety culture are presented.FindingsKey points and recommendations that are worthy for discussion about incorporation in the Bulgarian tall buildings fire safety requirements are upgraded requirements for fire load density, detection and sprinkler systems in tall residential buildings, refuge floors, ventilation/air conditioning control systems, full-scale burning tests and fire engineering approach. The importance of fire safety management is emphasized as a main, key component in facility management.Originality/valueThe research is the first study focusing on implementation of additional and specific fire safety regulations for tall buildings in Bulgaria.

A physical model-free ant colony optimization network algorithm and full scale experimental investigation on ceiling temperature distribution in the utility tunnel fire

To advance understanding of the ceiling temperature characters in tunnel fires, a physical model-free ant colony optimization network algorithm is developed. Compared to the traditional physical model-based methods, the algorithm is not limited to the specific fire conditions and the structure of tunnels. The main advantage and contribution of the algorithm is that a novel ant colony optimization (ACO) network is constructed and firstly used to predict the ceiling temperature distribution in the tunnel fire as well as the maximal ceiling temperature based on only some sensors data. In order to verify the effectiveness of the algorithm, full scale burning tests were investigated in the largest fire experiment platform of the utility tunnel at the Tianjin Fire Research Institute, China. In addition, the developed ACO network algorithm has excellent performance by contrast with the commonly used back propagation (BP) neural network algorithm. By compared with the experimental results and the results obtained from the BP neural network algorithm, the ability and the effectiveness of the algorithm were supported. The algorithm can be used to predict the ceiling temperature in the tunnel fires for rapid and efficient fire disaster evaluation.

Sustainable Smoke Extraction System for Atrium: A Numerical Study

Smoke extraction systems, either static with natural ventilation, or dynamic with mechanical ventilation are required to keep smoke layer at high levels in many tall atria. It is observed that a design fire with high heat release rate (HRR) is commonly used for designing natural vents, but a low HRR is used for mechanical ventilation system. This will not produce a sustainable environment. There are no internationally agreed on design guides to determine the HRR in the design fire for different extraction systems and scenarios. This issue will be studied using a Computational Fluid Dynamics (CFD)-based software, the Fire Dynamics Simulator (FDS) version 6.7.1. Simulations on natural smoke filling, static and dynamic smoke extractions were carried out in a big example atrium. CFD-FDS predictions were compared with previous full-scale burning tests. Results confirmed that static smoke extraction is a good option for big fires, and a dynamic system is best for small fires. A sustainable new hybrid design combining the advantages of static and dynamic systems is proposed, which could result in a lower smoke temperature and higher smoke layer interface height, indicating a better extraction design.

Full-scale experimental investigation on smoke spreading and thermal characteristic in a transversely ventilated urban traffic link tunnel

Transverse ventilation system is an effective method to control the smoke propagation in tunnel fires. In the current research, 14 full-scale burning tests were conducted in an urban traffic link tunnel in Chongqing, China. Temperature and velocity profiles, as well as the smoke stratification characteristics affected by the transverse ventilation were successively explored. Results underlined that 1) Fire location and air supply system have limited influence on the induced air velocity while the induced air velocity slightly decreased as heat release rate increased. When more smoke outlets were activated, the induced air velocity increased; 2) Ceiling temperature was very sensitive to the fire location, smoke extraction, and air supply system. A distinct temperature decrease was observed when (a) the fire moved closer to the outlet; (b) more outlets were activated; (c) supply vents near the fire were opened; 3) Thermal stratification could be well predicted by the temperature quotient proposed by Newman. Considering the transverse ventilation, the relationship between temperature ratio ΔTcf/ΔTavg and Froude number Fr accounting for the transverse ventilation was modified based on the present measurements.

A large-scale experimental study on the thermal failure propagation behaviors of primary lithium batteries

In order to investigate the thermal failure propagation behaviors of lithium batteries, a sequence of full-scale burning tests were conducted. The results showed that the average mass loss and total heat release of an individual cell are 5.8 g and 31.9 kJ, respectively. The battery pack fire exhibited intermittent propagation behaviors due to the heat interaction between the cells. An obvious domino phenomenon with a chain-like increase in temperature rise and propagation speed could be observed during the thermal failure propagation process. The temperature of the cell surface is about 700~1000 °C during the combustion process. Several cells burned simultaneously and exacerbated the burning rate, resulting in the larger mass loss rate and the heat release rate for the larger battery pack. The average mass loss rate is 0.69 g/s for 6 × 6 cells and 1.0 g/s for 10×10 cells, respectively. Moreover, the increasing combustion efficiency appeared in the larger battery pack. The effective heat is 2.0 kJ/g for single cell, 3.2 kJ/g for 6 × 6 cells, and 3.9 kJ/g for 10×10 cells. This study can provide a theoretical reference for the fire safety design of large lithium battery energy storage equipment.

New Experimental Evaluation Strategies Regarding Slag Prediction of Solid Biofuels in Pellet Boilers

Pellet boilers and pellet stoves are widely used for heat production. But in most cases, only specific wood pellets with a low ash content are approved due to the increased risk of slagging and limited deashing capacity. The ash fusion test (AFT), according to prCEN/TS 15370-1, is currently the only standard method for the prediction of slagging. This method is not feasible for all biomass fuel types, since sometimes the characteristic temperatures cannot be determined or the characteristic shapes do not occur for temperature determination. Furthermore, the method is costly and requires complex instrumental infrastructure. Hence, a demand for more expressive or more rapid methods to characterize slag formation potential of fuels is often claimed. Based on a literature study, four such laboratory test methods were chosen, partly adapted, and then experimentally investigated. These methods included thermal treatment of the fuel itself or the ashes of the fuel and were the rapid slag test, CIEMAT, the slag analyzer, and the newly developed pellet ash and slag sieving assessment (PASSA) method. Method performance was practically assessed using 14 different biomass fuel pellets, which were mainly from different assortments of wood, but also herbaceous or other nonwoody fuels. The results from the tests with these four alternative methods were evaluated by comparing to both results from standard AFT and results from full-scale combustion tests performed over a maximum of 24 h. Seven different pellet boilers were assessed, of which one boiler was used to apply all 14 test fuels. According to the granulometric ash analysis (i.e., the ratio of >1 mm-fraction toward total ash formed), the sensitivity of the new test methods to depict slagging phenomena at a suitable level of differentiation was assessed. Satisfactory conformity of the boiler ash assessment (reference) was found for both, the slag analyzer and the PASSA method. The latter may, in particular, be seen as a promising and relatively simple low-input procedure, which can provide more real-life oriented test results for fixed-bed combustion. The standardized AFT could, however, not sufficiently predict the degree of slag actually formed in the reference boiler, particularly when only wood fuels are regarded.

Analysis of the Self-Excited Dynamics of a Heavy-Duty Annular Combustion Chamber by Large-Eddy Simulation

Abstract This paper discusses the use of large eddy simulation (LES) to predict the performance of an annular combustion chamber in stable operating conditions and in the presence of self-exited dynamics. The availability of high-accuracy data taken in a full-scale combustion test facility allowed an extensive validation of the prediction capability. The analysis focuses on a small size heavy duty annular gas turbine whose size allows to test and compute the entire 360 deg combustion chamber. The comparison with measurements confirms that, if the correct operating conditions are implemented, LES is capable to discern between stable and unstable operating conditions, as well as predict several other engineering relevant parameters, although the model is sometime affected by a limited shift in frequency.The post processing of LES results in presence of combustion dynamics is not a trivial task. Here, the results of the simulations have been postprocessed by means of a triple decomposition method to determine a mean flow, a deterministic unsteady flow at the main instability frequency, and a turbulent stochastic flow. Such decomposition indicated the instability triggering mechanism together with the cross-talk mechanism between different components. This approach is currently used for design phase, while further validation is on-going to include different geometries and operating conditions with the goal of reducing both risks and number of tests.

Performance evaluation on fixed water-based firefighting system in suppressing large fire in urban tunnels

Operating fixed water-based firefighting systems (FFFS) might affect the performance of other parts of an integrated tunnel safety system, particularly the longitudinal ventilation system. The interaction of the water spray discharged from two FFFS (with and without foam), with the longitudinal ventilation system in a new city tunnel under construction was studied by full-scale burning tests. Results of the study under large fires up to 20 MW in diesel pool fires or wood pallet fires are reported in this paper. The impact of longitudinal ventilation, the activation sequences of the ventilation system and the fixed fire-fighting system, and the performance of the two FFFS in suppressing vehicular fires with and without shields to fire sources were evaluated. Results are expected to be useful for drafting appropriate fire codes on fire suppression systems for controlling urban tunnel fires.

Dependence of flame height of internal fire whirl in a vertical shaft on fuel burning rate in pool fire

An internal fire whirl (IFW) was generated by a pool fire in a vertical shaft with appropriate ventilation provision at the wall. The flame height of the IFW was found to increase with the burning rate of the pool fire. Semi-empirical formula for flame height in the IFW was studied analytically in this paper using reported experimental data from full-scale burning tests. Burgers vortex theory was applied for dynamic and thermodynamic corrections. From the experimental data, a rotating flame height coefficient was introduced to modify the empirical formula for the flame height in the IFW. Effects of thermal radiation and fuel vaporization were included to modify the calculation of the fuel burning rate.

Informal settlement fires in South Africa: Fire engineering overview and full-scale tests on “shacks”

This paper discusses fires in informal settlements (otherwise known as slums, ghettos, shantytowns, etc.), which are regularly ravaged by fire in South Africa. Initially an overview of the problem is presented, highlighting the factors that contribute to the frequent, large conflagrations that occur. Details have been based on research conducted in Cape Town, South Africa, although the research is applicable to settlements worldwide. Data from recent fires where up to 4500 people were left homeless is included, highlighting aspects regarding fire spread and fire dynamics. Thereafter, preliminary results from a pilot study are presented where full-scale burn tests have been carried out on informal settlement dwellings, or “shacks”. Results from (a) a smoldering fire test, (b) 25kg/m2 wood fire load test and (c) a ‘representative’ shack fire test are presented. For flaming fires it is shown that flashover in these small dwellings can occur in as little as one minute (depending on the fuel source), which is consistent with observations from professional firefighters in the field. Photoelectric smoke detectors, ionization, and rate-of-rise heat detectors were included during fire tests, to evaluate their performance in such confined spaces, as these are currently being either used or being considered for use in settlements. Activation times are reported for the different tests conducted.

A Probabilistic Inferential Algorithm to Determine Fire Source Location Based on Inversion of Multidimensional Fire Parameters

A probabilistic inferential framework is proposed to utilize transient temperature data measured at the ceiling of the compartment to determine location of fire source, as well as size of fire, based on Bayesian inferential theory. This approach treats the problem as one of parameter estimation, expressed as a function of posterior probability distribution based on the qualitative of agreement between predicted temperatures and observed temperatures at the sensor locations. A comparison of the measured temperature from full-scale burn tests with predicted temperatures from in verse problem solution algorithm indicate the error to be less than 5% when fires are small, but the error increases to more than 10% for large size fires. The accuracy of the inverse problem solution algorithm can be improved by utilizing data from sensitivity studies carried out on fire source location errors and heat release rate errors.

Thermodynamic Equilibrium Model Applied To Predict the Fouling Tendency in a Commercial Fluidized-Bed Boiler, Combusting Solid Waste

A thermodynamic equilibrium model, combined with an advanced fuel analysis, was applied to predict the fouling tendency in a commercial bubbling fluidized-bed (BFB) boiler, combusting a mixture of solid waste. In order to enhance the performance of the model, further modifications were made, considering the combustion pattern in the fluidized-bed system and also the temperature profile in the combustion zone. The modeling was performed using Factsage, and experimental data obtained during the full-scale measurements were used as input for the model, simulating the deposit formation in the real boiler. The simulation results were then compared with the results obtained during the full-scale combustion tests to estimate the accuracy and validity of the applied model. The thermodynamic equilibrium modeling proved to be a reliable tool for predicting the fouling in the BFB boiler, thus determining the fraction of the melt in the deposited salts formed on the heat transfer surfaces during the flue gas condensation. The calculations showed that the ratio of the SO2 to alkali chloride concentration in the flue gas was the decisive factor that affected the rate of the deposit formation in the boiler. Both the simulation and the experimental results indicated that lower bed temperatures and cocombustion of P-rich fuels decrease the deposition buildup in the boiler.

Effect of CaO on retention of S, Cl, Br, As, Mn, V, Cr, Ni, Cu, Zn, W and Pb in bottom ashes from fluidized-bed coal combustion power station

This work was conducted to evaluate whether Ca-bearing additives used during coal combustion can also help with the retention of some other elements. This work was focused on the evaluation of bottom ashes collected during four full-scale combustion tests at an operating thermal fluidized-bed power station. Bottom ashes were preferred to fly ashes for the study to avoid interference from condensation processes usually occurring in the post-combustion zone. This work focused on the behaviors of S, Cl, Br, As, Mn, V, Cr, Ni, Cu, Zn, W, and Pb. Strong positive correlations with CaO content in bottom ashes were observed (for all four combustion tests) for S, As, Cl and Br (R=0.917–0.999). Strong inverse proportionality was calculated between the contents of Pb, Zn, Ni, Cr and Mn and CaO, so these elements showed association to materials other than Ca-bearing compounds (e.g., to aluminosilicates, organic matter, etc.). Somewhat unclear behaviors were observed for W, Cu, and V. Their correlation coefficients were evaluated as statistically “not significant”, i.e., these elements were not thought to be significantly associated with CaO. It was also discovered that major enrichment of CaO in the finest bottom ash fractions could be advantageously used for simple separation of elements strongly associated with these fractions, mainly S and As, but also Cl or Br. Removal of 5% of the finest ash particles brings about a decrease in As concentration down to 77%–80% of its original bulk ash content, which can be conveniently used e.g., when high As content complicates further ash utilization.

Numerical studies on heat release rate in a room fire burning wood and liquid fuel

Heat release rates of burning gasoline and wood fires in a room were studied by computational fluid dynamics (CFD). Version 5.5.3 of the software Fire Dynamics Simulator (FDS), which is the latest one available, was selected as the CFD simulation tool. Predicted results were compared with two sets of reported data from full-scale burning tests. In the two sets of experiments, the scenarios were set at gasoline pool fire and wood chipboard fire with gasoline respectively. The input heating rate of gasoline pool fire based on experimental measurements was used in the first set of experiments. Three scenarios G1, G2 and G3 with different grid systems were simulated by CFD. The grid system of scenario G2 gave more accurate prediction, which was then used to study the second set of experiments on wood chipboard with gasoline. The combustion model in FDS was used in wood chipboard fire induced by gasoline pool. The wood chipboard was allowed to burn by itself using the pyrolysis model in FDS. The effects of the boundary conditions on free openings for the same set of experiments were studied by three scenarios SOB1, SOB2 and SOB3. Boundary condition SOB2 gave more reliable prediction among the three boundary conditions. Two other scenarios on the effect of moisture content of wood were also studied. The predicted HRR curve was found to agree better with experiment in using SOB2.

Bed Agglomeration Characteristics during Cocombustion of Animal Waste with Municipal Solid Waste in a Bubbling Fluidized-Bed Boiler—A Thermodynamic Modeling Approach

Full-scale waste combustion tests showed that adding animal waste (AW) to municipal solid waste (MSW) prevented bed agglomeration, and the reason for this finding was not fully understood. This study uses thermodynamic modeling to investigate the composition of equilibrium products for two combustion scenarios: monocombustion of MSW (the reference case) and cocombustion of AW with MSW (the AW case). The modeling was performed using FactSage, and experimental data obtained during the full-scale combustion tests were used as input data for the calculations. The results of equilibrium modeling, together with information extracted from ternary phase diagrams, suggest higher bed temperature as the primary cause for formation of bed agglomerates in the reference case. In addition, melt-induced agglomeration is suggested as the bed agglomeration mechanism in this case. In the AW case, however, reduced bed temperature, as well as enriched calcium phosphate and sulfate in the bottom ashes are considered to significantly decrease the slagging tendency.

Co-Combustion of Animal Waste in a Commercial Waste-to-Energy BFB Boiler

Co-combustion of animal waste, in waste-to-energy boilers, is considered a method to produce both heat and power and to dispose of possibly infected animal wastes. This research conducted full-scale combustion tests to identify the impact of changed fuel composition on a fluidized-bed boiler. The impact was characterized by analyzing the deposit formation rate, deposit composition, ash composition, and emissions. Two combustion tests, denoted the reference case and animal waste case, were performed based on different fuel mixes. In the reference case, a normal solid waste fuel mix was combusted in the boiler, containing sorted industry and household waste. In the animal waste case, 20 wt% animal waste was added to the reference fuel mix. The collected samples, comprising sampling probe deposits, fuel mixes, bed ash, return sand, boiler ash, cyclone ash and filter ash, were analyzed using chemical fractionation, SEM-EDX and XRD. The results indicate decreased deposit formation due to animal waste co-combustion. SEM-EDX and chemical fractionation identified higher concentrations of P, Ca, S, and Cl in the bed materials in the animal waste case. Moreover, the risk of bed agglomeration was lower in the animal waste case and also a decreased rate of NOx and SO2 emissions were observed.

Full-Scale Burn Test of a 2001 Full-Size Pickup Truck

Full-Scale Burn Test of a 2001 Full-Size Pickup Truck