scholarly journals HEAT RELEASE RATE AS A PARAMETER FOR FIRE SPREAD – A CASE STUDY

2020 ◽  
pp. 101
Author(s):  
Darko N. Zigar ◽  
Dusica J. Pesic ◽  
Milan Đ. Blagojevic
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Simulation Method ◽  
Fire Spread ◽  
Fire Dynamics ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Fire Spreading

Indoor fires very often may cause great material damage and endanger human lives. The heat produced by fire affects the heating and ignition of surrounding flammable materials, as well as the heating of the building structure, causing its damage. It is well known that fire spread mostly depends on flammability and quantity of surrounding material, but small differences in the amount of fuel can significantly affect the speed of fire spread, and consequently, rate of heat released by fire. In this paper, the influence of the heat release rate on fire spreading is shown. The Large Eddy Simulation method of Fire Dynamics Simulator software package has been used to investigate the prediction of fire dynamics in a compartment. Numerical results show that the fire dynamics in the compartment is largely dependent on the quantity of fire load mass and the heat release rate during the fire.

The Effects of Forcing Direction on the Flame Transfer Function of a Lean-Burn Spray Flame

2021 ◽  
Author(s):  
Nicholas C. W. Treleaven ◽  
André Fischer ◽  
Claus Lahiri ◽  
Max Staufer ◽  
Andrew Garmory ◽  
...  
Keyword(s):  
Transfer Function ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Fuel Injector ◽  
Lean Burn ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Good Reproduction ◽  
Small Change

Abstract The flame transfer function (FTF) of an industrial lean-burn fuel injector has been computed using large eddy simulation (LES) and compared to experimental measurements using the multi-microphone technique and OH* measurements. The flame transfer function relates the fluctuations of heat release in the combustion chamber to fluctuations of airflow through the fuel injector and is a critical part of thermoacoustic analysis of combustion systems. The multi-microphone method derives the FTF by forcing the flame acoustically, alternating from the upstream and downstream side. Simulations emulating this methodology have been completed using compressible large eddy simulations (LES). These simulations are also used to derive an FTF by measuring the fluctuations of mass flow rate and heat release rate directly which reduces the number of simulations per frequency to one, significantly reducing the simulation cost. Simulations acoustically forced from downstream are shown to result in a lower value of the FTF gain than simulations forced from upstream with a small change in phase, this is shown to be consistent with theory. Through using a slightly different definition of the FTF, this is also shown to be consistent with measurements of the heat release rate using OH* chemiluminescence however these results are inconsistent with the multi-microphone method result. The discrepancy comes from not having an accurate measurement of the acoustic impedance at the exit plane of the injector and from certain convective phenomena that alter the downstream velocity and pressure field with respect to the purely acoustic signal. All simulations show a lower gain in the FTF than the experiments but with good reproduction of phase. Previous work suggests this error is likely due to fluctuations of the fuel spray atomisation process due to the acoustic forcing which is not modelled in this study.

scholarly journals LARGE EDDY SIMULATION OF LEAN MIXED-MODE COMBUSTION ASSISTED BY PARTIAL FUEL STRATIFICATION IN A SPARK-IGNITION ENGINE

2021 ◽  
pp. 1-15
Author(s):  
Chao Xu ◽  
Sibendu Som ◽  
Magnus Sjoberg
Keyword(s):  
Large Eddy Simulation ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Mixed Mode ◽  
Spark Ignition ◽  
Pilot Injection ◽  
Eddy Simulation ◽  
Fuel Stratification ◽  
Large Eddy

Abstract Partial fuel stratification (PFS) is a promising fuel injection strategy to improve the stability of lean combustion by applying a small pilot injection near spark timing. Mixed-mode combustion, which makes use of end-gas autoignition following conventional deflagration-based combustion, can be further utilized to speed up the overall combustion. In this study, PFS assisted mixed-mode combustion in a lean-burn direct injection spark-ignition (DISI) engine is numerically investigated using multi-cycle large eddy simulation (LES). A previously developed hybrid G-equation/well-stirred reactor combustion model is extended to the PFS condition. The experimental spray morphology is employed to derive spray model parameters for the pilot injection. The LES based model is validated against experimental data and is further compared with the Reynolds-averaged Navier-Stokes (RANS) based model. Overall, both RANS and LES predict the mean pressure and heat release rate traces well, while LES outperforms RANS in capturing the CCV and the combustion phasing in the mass burned space. Liquid and vapor penetrations obtained from the simulations agree reasonably well with the experiment. Detailed flame structures predicted from the simulations reveal the transition from a sooting diffusion flame to a lean premixed flame, which is consistent with experimental findings. LES captures more wrinkled and stretched flames than RANS. Finally, the LES model is employed to investigate the impacts of fuel properties, including heat of vaporization (HoV) and laminar burning speed (SL). Combustion phasing is found more sensitive to SL than to HoV, with a larger fuel property sensitivity of the heat release rate from autoignition than that from deflagration. Moreover, the combustion phasing in the PFS-assisted operation is shown to be less sensitive to SL compared with the well-mixed operation.

scholarly journals Large Eddy Simulation of Lean Mixed-Mode Combustion Assisted by Partial Fuel Stratification in a Spark-Ignition Engine

2020 ◽  
Author(s):  
Chao Xu ◽  
Sibendu Som ◽  
Magnus Sjöberg
Keyword(s):  
Large Eddy Simulation ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Mixed Mode ◽  
Spark Ignition ◽  
Pilot Injection ◽  
Eddy Simulation ◽  
Fuel Stratification ◽  
Large Eddy

Abstract Lean operation is beneficial to spark-ignition engines due to the high thermal efficiency compared with conventional stoichiometric operation. Lean combustion can be significantly stabilized by the partial fuel stratification (PFS) strategy, in which a small amount of pilot injection is applied near the spark energizing timing in addition to main injections during intake. Furthermore, mixed-mode combustion, which makes use of end-gas autoignition following conventional deflagration-based combustion, can be further utilized to speed up the overall combustion. In this study, PFS-assisted mixed-mode combustion in a lean-burn direct injection spark-ignition (DISI) engine is numerically investigated using multi-cycle large eddy simulation (LES). To accurately represent the pilot injection characteristics, experimentally-derived spray morphology parameters are employed for spray modeling. A previously developed hybrid G-equation/well-stirred reactor model is extended to PFS conditions, to capture interactions of pilot injection, turbulent flame propagation and end-gas autoignition. The LES-based engine model is compared with Reynolds-averaged Navier-Stokes (RANS) based model, allowing an investigation of both mean and cycle-to-cycle variation (CCV) of combustion characteristics. Instantaneous spray and flame structures from simulations are compared with experiments. The LES-based model is finally leveraged to investigate impacts of fuel properties including heat of vaporization (HoV) and laminar flame speed (SL). It is shown that overall, the predicted mean pressure and heat release rate traces from both RANS and LES agree well with the experiment, while LES captures the CCV and the combustion phasing in the mass burned space much better than RANS. Predicted liquid fuel penetrations agree reasonably well with the experiment, both for RANS and LES. Detailed flame structures in the simulations also reveal the transition from a sooting flame to a lean premixed flame, which is consistent with experimental findings. LES is shown to capture more wrinkled and stretched flame fronts than RANS. Local sensitivity analysis further identifies the stronger combustion phasing sensitivity to SL compared with that to HoV, and the stronger sensitivity of autoignition heat release rate than deflagration. The results from this study demonstrate the high fidelity of the developed computational model based on LES, enabling future investigation of PFS-assisted mixed-mode combustion for different fuels and a wider range of operating conditions.

scholarly journals Estimation of Magnitude and Heat Release Rate of Fires Occurring in Historic Buildings-Taking Churches as an Example

2021 ◽  
Vol 13 (16) ◽  
pp. 9193
Author(s):  
Wen-Yao Chang ◽  
Chieh-Hsin Tang ◽  
Ching-Yuan Lin
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Water Mist ◽  
Smoke Detector ◽  
Fire Dynamics ◽  
Historical Building ◽  
Maximum Heat ◽  
Improvement Measures ◽  
Maximum Heat Release

Historical buildings often fail to meet today’s building and fire protection regulations due to their structure and space restrictions. For this reason, if such buildings encounter fire, serious damage will be resulted. The fire of the Notre-Dame Cathedral in Paris (Notre-Dame de Paris) in April 2019 highlights the seriousness of this problem. In this study, the historical building of “Tamsui Church” was selected as an example. The Fire Dynamics Simulator (FDS) was adopted to analyze the scale of damage and possible hazards when the wooden seats in the church are on fire, and improvement measures were proposed to ensure that such buildings can be used under safer conditions. It was found that the existing seat arrangement will cause the spreading of fire, and the maximum heat release rate is 2609.88 kW. The wooden roof frame above the fire source will also start to burn at 402.88 s (6.6 min) after the fire, which will lead to a full-scale fire. To maintain the safety of the historical building, it is necessary to add active firefighting equipment (smoke detector and water mist system).

Fire Growth in Standard Tests and Railcars

2018 ◽  
Author(s):  
Charles Luo ◽  
Soroush Yazdani ◽  
Brian Y. Lattimer
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Large Scale ◽  
Growth Conditions ◽  
Standard Test ◽  
Fire Growth ◽  
Gas Temperature ◽  
Fire Dynamics ◽  
Room Corner Test

Large scale flammability performance of interior finish used on railcars has been evaluated in previous studies using the NFPA 286 room corner fire test, which has a cross-section similar to a railcar. In some studies, the wall containing the door was removed to account for the shorter length of the room compared to the railcar length. The focus of this study is to assess whether the NFPA 286 standard room-corner test with a door represents conditions that developed inside a railcar during a fire. Fire Dynamics Simulator (FDS) was used to model the fire growth in a NFPA 286 standard room-corner test with a door, NFPA 286 room without the wall containing the door, and railcar geometry with a single door open. All three cases had the same exposure fire in a corner and the same lining material. In predictions of the NFPA 286 room-corner test with a door, gas temperature, heat release rate, and time to flashover agreed well with available NFPA 286 standard test data. The simulation results of fire growth inside a railcar with one side door open produced similar conditions and fire growth compared with the standard NFPA 286 room with a door. For simulations on the NFPA 286 room with the wall containing the door removed, it was found that removal of the wall with the door resulted in non-conservative fire growth conditions with the gas temperature and heat release rate under-estimated compared to the standard NFPA 286 room with a door. These simulations indicate that the standard NFPA 286 room-corner test with a door is representative of conditions that would develop inside of a railcar.

scholarly journals Karakteristik Penyebaran Api Ketika Terjadi Kebakaran Berbasis Metode FDS (Fire Dynamics Simulator) pada Parkiran Sepeda Motor Kampus A Universitas Negeri Jakarta

2016 ◽  
Vol 3 (3) ◽  
pp. 165-173
Author(s):  
Pratomo Setyadi
Keyword(s):  
Heat Release ◽  
Burning Rate ◽  
Heat Release Rate ◽  
Release Rate ◽  
Fire Dynamics ◽  
Fire Dynamics Simulator ◽  
Fire Modelling

Penelitian ini dilatar belakangi karena melihat kondisi bangunan parkiran depan Kampus A Universitas NegeriJakarta yang pembangunan tersendat tetapi sudah dipergunakan untuk khayalayak di khawatirkan dapat membahayakanpenghuni, dan karyawan yang bekerja di gedung parkiran tersebut apabila terjadi kebakaran. Penelitian ini bertujuan untukmenentukan kriteria bahaya kebakaran pada parkiran sepeda motor kampus A UNJ. Dalam penelitian ini digunakan SoftwareFire Dynamics Simulator Version 5.0 untuk membuat suatu pemodelan kebakaran berdasarkan titik awal nyala api dan arahangin.Pada penelitian ini akan membahas tentang perkembangan api dimana perkembangan api tersebut akandirepresentasikan oleh HRR (Heat Release Rate), burning rate, dan visualisasi dari masing-masing simulasi. Langkah inisangat menguntungkan karena dapat mengetahui bagaimana penyebaran api saat terjadi kebakaran dan seberapa bahayakebakaran yang disimulasikan. Dengan adanya fire modelling ini dapat menjadi pendekatan engineering praktis untukmemberikan peninjauan tambahan terhadap aspek keselamatan kebakaran pada gedung parkiran kampus A UniveristasNegeri Jakarta. Dari hasil penelitian ini dapat disimpulkan bahwa cepatnya penyebaran api dipengaruhi titik awalnya api,kecepatan dan arah angin. Dimana semakin besar nilai HRR maka semakin besar pula nilai burning rate yang didapatkandan semakin besar pula tingkat kebakaran yang terjadi.

Numerical and Experimental Study of Merging Fires in Square Arrays

2007 ◽  
Author(s):  
Kohyu Satoh ◽  
Liu Naian ◽  
Liu Qiong ◽  
K. T. Yang
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Forest Fires ◽  
Large Scale ◽  
Gas Flow ◽  
Fire Spread ◽  
Total Heat ◽  
Total Heat Release ◽  
Convective Gas Flow

In large-scale forest fires and city fires, merging fires and fire whirls have often been observed, which cause substantial casualties and property damages. It is important to know particularly where and under what conditions of weather such merging fires and fire whirls appear in cities or forests. However, there have been no adequate answers, since the detailed physical characteristics about them are not fully clarified yet, although previous studies have examined the phenomena of merging flames. Therefore, we have carried out preliminary studies and found that the merged tall fires can enhance the fire spread, and developed a method to analyze burn-out data of fire arrays. If sufficient knowledge can be obtained by relevant experiments and numerical computations, it may be possible to mitigate the damages due to merged fires and fire whirls. The objective of this study is to investigate the merging conditions of fires in square arrays in laboratory experiments and also by CFD numerical simulations, varying the size of square array, inter-fire distance and heat release rate, to judge ‘unmerged’ or ‘merged’ conditions in the fire array. It has been found that the fire merging is dependent on the inter-fire distance in the array and also on the total heat release rate of all fires surrounding the center region of the array. Also found that the experimental and simulated results on the merged and unmerged cases in the fire array, as affected by the total heat release rate and the inter-fire distance, which control the convective gas flow into the array, behave very similarly. Therefore, it can be concluded that the fire merging in array fires are highly based on the convection in the flow field due to fires and can be predicted by simple CFD simulations.

scholarly journals Numerical Studies on Heat Release Rate in Room Fire on Liquid Fuel under Different Ventilation Factors

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
N. Cai ◽  
W. K. Chow
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Liquid Fuel ◽  
Cfd Simulation ◽  
Far East ◽  
Sensitivity Study ◽  
Free Boundaries ◽  
Fire Dynamics ◽  
Door Opening

Heat release rate (HRR) of the design fire is the most important parameter in assessing building fire hazards. However, HRR in room fire was only studied by computational fluid dynamics (CFD) in most of the projects determining fire safety provisions by performance-based design. In contrast to ten years ago, officers in the Far East are now having better knowledge of CFD. Two common questions are raised on CFD-predicted results on describing free boundaries; and on computing grid size. In this work, predicting HRR by the CFD model was justified with experimental room pool fire data reported earlier. The software fire dynamics simulator (FDS) version 5 was selected as the CFD simulation tool. Prescribed input heating rate based on the experimental results was used with the liquid fuel model in FDS. Five different free boundary conditions were investigated to predict HRR. Grid sensitivity study was carried out using one stretched mesh and multiple uniform meshes with different grid sizes. As it is difficult to have the entire set of CFD predicted results agreed with experiments, macroscopic flow parameters on the mass flow rate through door opening predicted by CFD were also justified by another four conditions with different ventilation factors.

scholarly journals Inversion for Fire Heat-Release Rate Using Heat Flux Measurements

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Andrew J. Kurzawski ◽  
Ofodike A. Ezekoye
Keyword(s):  
Heat Flux ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Fire Hazard ◽  
Computational Cost ◽  
Inversion Algorithm ◽  
Fire Dynamics ◽  
Oxygen Consumption Calorimetry ◽  
Flux Measurements

Abstract In fire hazard calculations, knowledge of the heat-release rate (HRR) of a burning item is imperative. Typically, room-scale calorimetry is conducted to determine the HRRs of common combustible items. However, this process can be prohibitively expensive. In this work, a method is proposed to invert for the HRR of a single item burning in a room using transient heat flux measurements at the walls and ceiling near the item. The primary device used to measure heat flux is the directional flame thermometer (DFT). The utility of the inverse method is explored on both synthetically generated and experimental data using two so-called forward models in the inversion algorithm: fire dynamics simulator (FDS) and the consolidated model of fire and smoke transport (CFAST). The fires in this work have peak HRRs ranging from 200 kW to 400 kW. It was found that FDS outperformed CFAST as a forward model at the expense of increased computational cost and that the error in the inverse reconstruction of a 400 kW steady fire was on par with room-scale oxygen consumption calorimetry.

scholarly journals Computational Assessment of the Hazardous Release Dispersion from a Diesel Pool Fire in a Complex Building’s Area

Computation ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 65 ◽  
Author(s):  
Konstantinos Vasilopoulos ◽  
Michalis Mentzos ◽  
Ioannis Sarris ◽  
Panagiotis Tsoutsanis
Keyword(s):  
Physical Phenomenon ◽  
Simulation Method ◽  
Pool Fire ◽  
Urban Setting ◽  
Dynamics Simulation ◽  
Fire Dynamics ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Urban Geometry ◽  
Large Eddy

A hazardous release accident taking place within the complex morphology of an urban setting could cause grave damage both to the population’s safety and to the environment. An unpredicted accident constitutes a complicated physical phenomenon with unanticipated outcomes. This is because, in the event of an unforeseen accident, the dispersion of the hazardous materials exhausted in the environment is determined by unstable parameters such as the wind flow and the complex turbulent diffusion around urban blocks of buildings. Our case study focused on a diesel pool fire accident that occured between an array of nine cubical buildings. The accident was studied with a Large eddy Simulation model based on the Fire Dynamics Simulation method. This model was successfully compared against the nine cubes of the Silsoe experiment. The model’s results were used for the determination of the immediately dangerous to life or health smoke zones of the accident. It was found that the urban geometry defined the hazardous gasses dispersion, thus increasing the toxic mass concentration around the buildings.

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