Fire | Special Issue : Pyrolysis, Ignition, Combustion and Fire Spread of Combustible Materials

Research

20 pages, 13314 KiB

Open AccessArticle

Effect of Bubbling on Ignition of PMMA Slab: Change in Thermo-Physical and Thermo-Radiative Properties

by Chloë Vincent, Claire Longuet, Laurent Aprin, Pierre Slangen, Guillaume Rambaud and Laurent Ferry

Fire 2024, 7(4), 117; https://doi.org/10.3390/fire7040117 - 03 Apr 2024

Viewed by 512

Abstract

In semi-transparent polymers, ignition is not only dependent on conductive thermal transfer into the material but also on in-depth absorption of the radiation. The aim of this work was to investigate the influence of bubbling on the thermo-physical and thermo-radiative properties of PMMA [...] Read more.

In semi-transparent polymers, ignition is not only dependent on conductive thermal transfer into the material but also on in-depth absorption of the radiation. The aim of this work was to investigate the influence of bubbling on the thermo-physical and thermo-radiative properties of PMMA and how it may affect its ignition. PMMA plates of varying thickness were exposed to the heat flux of two radiative sources with different emission spectra. Exposure was stopped after different periods of time to study bubbling kinetics and bubble size distribution by optical microscopy. Front and back surface temperatures of samples were recorded during heat exposure. The results indicate that the bubble size distribution is closely related to the temperature gradient within the sample. Steep thermal gradients lead to small-sized bubbles underneath the exposed surface, while weak thermal gradients generate a wider size distribution with in-depth bubbling. All thermo-physical quantities

k

,

ρ

and

C_{p}

were shown to decrease with increasing bubbling degree. Likewise, it was highlighted that bubbling modifies the thermo-radiative properties of PMMA, especially in the near-infrared range. Transmittance decreases while absorbance increases with a bubbling degree. The increase in the absorption coefficient was attributed to multiple scattering by bubbles that expand the pathway of radiation into the materials. It was concluded that changes in both the thermo-physical and thermo-radiative properties with bubbling were likely to account for the delay in ignition observed when using the near-infrared heating source. Full article

(This article belongs to the Special Issue Pyrolysis, Ignition, Combustion and Fire Spread of Combustible Materials)

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14 pages, 3891 KiB

Open AccessArticle

Determining the Conditions That Lead to the Self-Extinguished and Self-Sustained Smoldering Combustion of Wood

by Pengfei Ding, Chunyin Zhang, Qize He, Lijing Wang and Yun Yang

Fire 2024, 7(2), 60; https://doi.org/10.3390/fire7020060 - 19 Feb 2024

Viewed by 942

Abstract

To improve our understanding of flaming, smoldering, or self-extinction in the burning of wood, it is necessary to quantify the conditions that lead to self-extinguished and self-sustained smoldering combustion. Experiments were performed in a cone calorimeter under an external irradiation of 10 to [...] Read more.

To improve our understanding of flaming, smoldering, or self-extinction in the burning of wood, it is necessary to quantify the conditions that lead to self-extinguished and self-sustained smoldering combustion. Experiments were performed in a cone calorimeter under an external irradiation of 10 to 25 kW/m² to analyze the temperature and mass loss of self-extinguished and self-sustained smoldering. The smoldering front depth was the significant parameter used to capture the smoldering characteristic, and it was defined as the axial thickness that reaches the smoldering characteristic temperature. The critical smoldering front depth of self-extinguished smoldering was lower than 10–15 mm for 30 mm thick wood at 15.5 kW/m² irradiation. This critical depth decreased with the increase in heat flux, from 26.5 ± 1.5 mm at 10 kW/m² to 11 ± 1 mm at 25 kW/m². A simple theoretical analysis is proposed to explain the smoldering thickness threshold of self-sustained smoldering propagation based on the local heat balance. The equation predicts that the critical depth decreases as the heat flux increases, from 23.9 mm at 8 kW/m² to 7.3 mm at 25 kW/m². The predicted critical depth and heating duration were consistent with the experimental results. This study proposes a feasible parameter to help understand the threshold of smoldering propagation and the development of biomass burners. Full article

(This article belongs to the Special Issue Pyrolysis, Ignition, Combustion and Fire Spread of Combustible Materials)

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19 pages, 1646 KiB

Open AccessArticle

Investigation of Mineral Oil and CuO Mixed Synthetic Oil in Compression Ignition Engines: A Comparison of Physicochemical Attributes

by Aamir Sajjad Nasir, Muhammad Usman, Muhammad Ali Ijaz Malik, Asad Naeem Shah, Ali Turab Jafry, Muhammad Wajid Saleem, Naseem Abbas, Uzair Sajjad, Mohammad Rezaul Karim and Md Abul Kalam

Fire 2023, 6(12), 467; https://doi.org/10.3390/fire6120467 - 13 Dec 2023

Viewed by 1357

Abstract

Mineral oil resources are depleting rapidly, and the slower conventional oil biodegradation process results in environmental pollution. To resolve this issue, cupric oxide (CuO) nanoparticles (1% wt) were introduced into a base oil to improve the lubricating capability of castor oil. In addition, [...] Read more.

Mineral oil resources are depleting rapidly, and the slower conventional oil biodegradation process results in environmental pollution. To resolve this issue, cupric oxide (CuO) nanoparticles (1% wt) were introduced into a base oil to improve the lubricating capability of castor oil. In addition, 1% wt. sodium dodecyl sulfate was also blended with the base oil in order to attain the maximum dispersion stability of CuO nanoparticles in the castor oil. Afterward, thermophysical property, atomic absorption spectroscopy, and Fourier transform infrared radiation (FTIR) testing of the lubricant oil sample were performed before and after 100 h of engine operations at 75% throttle and 2200 rpm for each lubricant sample in order to check the capability of the novel oil with mineral oil. Compared with the natural mineral oil, the behavior of the CuO-based lubricant has essentially the same physical features, as measured according to ASTM standard methods. The physicochemical properties like (KV)_{40 °C}, (KV)_{100 °C}, FP, ash, and TBN decrease more in the case of the synthetic oil by 1.15, 1.11, 0.46, 1.1, and 1.2% than in the conventional oil, respectively. FTIR testing shows that the maximum peaks lie in the region of 500 to 1750 cm⁻¹, which shows the presence of C=O, C-N, and C-Br to a maximum extent in the lubricant oil sample. AAS testing shows that the synthetic oil has 21.64, 3.23, 21.44, and 1.23% higher chromium, iron, aluminum, and zinc content. However, the copper and calcium content in the synthetic oil is 14.72 and 17.68%, respectively. It can be concluded that novel bio-lubricants can be utilized as an alternative to those applications that are powered by naturally produced mineral oil after adding suitable additives that further enhance their performance. Full article

(This article belongs to the Special Issue Pyrolysis, Ignition, Combustion and Fire Spread of Combustible Materials)

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15 pages, 3937 KiB

Open AccessArticle

Kinetic Analysis of Thermal Decomposition of Polyvinyl Chloride at Various Oxygen Concentrations

by Shuo Yang, Yong Wang and Pengrui Man

Fire 2023, 6(10), 404; https://doi.org/10.3390/fire6100404 - 20 Oct 2023

Viewed by 1387

Abstract

PVC plastic products are common combustible substances seen in fires, but their thermal degradation behavior under different oxygen concentrations has not been adequately studied. The thermal degradation behavior of PVC materials in atmospheres with different oxygen concentrations was analyzed via thermogravimetric–Fourier transform infrared [...] Read more.

PVC plastic products are common combustible substances seen in fires, but their thermal degradation behavior under different oxygen concentrations has not been adequately studied. The thermal degradation behavior of PVC materials in atmospheres with different oxygen concentrations was analyzed via thermogravimetric–Fourier transform infrared spectroscopy (TG-FTIR). The TG results show that the thermal degradation process of PVC under a non-oxygenated atmosphere occurred in two stages, and the activation energies of the two stages were 130–175 KJ mol⁻¹ and 230–320 KJ mol⁻¹, respectively; under the oxygenated atmosphere, the thermal degradation process occurred in three stages. The activation energies of the three stages were 130–175 KJ mol⁻¹, 145–510 KJ mol⁻¹ and 75–190 KJ mol⁻¹, respectively. And the reaction mechanism of the second stage of thermal degradation was changed from D-ZLT₃ to E_n by the higher oxygen concentration. Infrared spectroscopy (FTIR) was used to analyze the pyrolysis process of PVC in the non-oxygenated atmosphere, and the eight major components were as follows, in descending order according to amount released: C-H stretching > HCl > C-Cl stretching > H₂O > CO₂ > C-H bending > C-H aliphatic bending > CH₂. For the reaction of PVC at an oxygen concentration of 7%, the nine major components, in descending order according to amount released, were as follows: CO₂ > HCl > H₂O > CO > C-H stretching > C-Cl stretching > C-H aliphatic bending > C-H bending > CH₂. For PVC reactions at oxygen concentrations of 14% and 21%, the five major components, in descending order according to amount released, were CO₂ > HCl > CO > C-Cl stretching > H₂O. Full article

(This article belongs to the Special Issue Pyrolysis, Ignition, Combustion and Fire Spread of Combustible Materials)

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19 pages, 2172 KiB

Open AccessArticle

Study on Pyrolysis Behaviors and Characteristics, Thermodynamics, Kinetics, and Volatiles of Single-Base Propellant, a Typical Energy-Containing Material

by Yitao Liu, Wenfang Zheng, Yueqiang Wu and Ruiyu Chen

Fire 2023, 6(10), 370; https://doi.org/10.3390/fire6100370 - 23 Sep 2023

Cited by 1 | Viewed by 1052

Abstract

The widespread use of single-base propellant may contribute to serious pollution of the environment. The study of single-base propellant pyrolysis could provide an in-depth understanding of the combustion mechanism, reveal the key steps and reaction kinetics of the combustion process, and reduce the [...] Read more.

The widespread use of single-base propellant may contribute to serious pollution of the environment. The study of single-base propellant pyrolysis could provide an in-depth understanding of the combustion mechanism, reveal the key steps and reaction kinetics of the combustion process, and reduce the damage when using single-base propellant to the environment. In the present study, the pyrolysis behaviors, pyrolysis characteristic parameters, kinetics, thermodynamics, and volatiles of single-base propellant pyrolysis in an argon atmosphere were studied. The results showed that the main temperature ranges of pyrolysis and heat variation were 400–700 K and 450–520 K, respectively. With the increase in the heating rate, the maximum/average reaction rate of pyrolysis increased, the maximum instantaneous heat flow and the heat flow integral increased, the pyrolysis and combustion performance increased, and the thermal stability decreased. The average global activation energy and pre-exponential factor of the pyrolysis were 202.82 kJ and 9.48 × 10²¹, respectively. Thermodynamic analysis showed that the single-base propellant pyrolysis was a spontaneous endothermic reaction with a low energy barrier and fast reaction rate, which was beneficial to the formation of active complexes. In addition, information on the main volatiles was obtained, including H₂, CH₄, C₂H₄, C₂H₆, H₂O, HCN, HCOOH, NO₂, HONO, and CO₂. Full article

(This article belongs to the Special Issue Pyrolysis, Ignition, Combustion and Fire Spread of Combustible Materials)

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13 pages, 784 KiB

Open AccessCommunication

Kinetic Study of Pyrolysis of Coniferous Bark Wood and Modified Fir Bark Wood

by Olga Yu. Fetisova, Nadezhda M. Mikova, Anna I. Chudina and Aleksandr S. Kazachenko

Fire 2023, 6(2), 59; https://doi.org/10.3390/fire6020059 - 08 Feb 2023

Cited by 5 | Viewed by 1221

Abstract

We report on the kinetics of pyrolysis of bark wood of four coniferous tree species: fir (Abies sibirica), larch (Larix sibirica), spruce (Picea obovata), and cedar (Pinus sibirica) denoted as FB, LB, SB, and CB, [...] Read more.

We report on the kinetics of pyrolysis of bark wood of four coniferous tree species: fir (Abies sibirica), larch (Larix sibirica), spruce (Picea obovata), and cedar (Pinus sibirica) denoted as FB, LB, SB, and CB, respectively. Thermogravimetry (TG) and differential scanning calorimetry (DSC) methods were used to study the influence of KCl and K₃PO₄ compounds on the process of thermal decomposition of fir bark and determine the main thermal effects accompanying this process. As a result of the studies carried out, it was found that KCl additives practically do not affect the decomposition of hemicelluloses, but they shift the maximum decomposition of the cellulose peak in the direction of decreasing temperature to 340.9 °C compared to untreated bark (357.5 °C). K₃PO₄ promotes the simultaneous decomposition of hemicelluloses and cellulose in the temperature range with a maximum of 277.8 °C. In both cases, the additions of KCl and K₃PO₄ reduce the maximum rate of weight loss, which leads to a higher yield of carbon residues: the yield of char from the original fir bark is 28.2%, in the presence of K₃PO₄ and KCl it is 52.6 and 65.0%, respectively. Using the thermogravimetric analysis in the inert atmosphere, the reaction mechanism has been established within the Criado model. It is shown that the LB, SB, and CB thermal decomposition can be described by a two-dimensional diffusion reaction (D2) in a wide range (up to 0.5) of conversion values followed by the reactions with orders of three (R3). The thermal decomposition of the FB occurs somewhat differently. The diffusion mechanism (D2) of the FB thermal decomposition continues until a conversion value of 0.6. As the temperature increases, the degradation of the FB sample tends to R3. It has been found by the thermogravimetric analysis that the higher cellulose content prevents the degradation of wood. The bark wood pyrolysis activation energy has been calculated within the Coats–Redfern and Arrhenius models. The activation energies obtained within these models agree well and can be used to understand the complexity of biomass decomposition. Full article

(This article belongs to the Special Issue Pyrolysis, Ignition, Combustion and Fire Spread of Combustible Materials)

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11 pages, 3373 KiB

Open AccessArticle

On The Flame Behavior during Cable Insulation Material Ignited by Fault Arc: A Flame Extracting and Noise Reduction Algorithm

by Yalong Wang, Chaoying Li, Haidong Liu, Jin Lin, Shouxiang Lu and Kim Meow Liew

Fire 2023, 6(2), 45; https://doi.org/10.3390/fire6020045 - 24 Jan 2023

Viewed by 1541

Abstract

The electric fault arc, particularly the series arc, leads to plenty of electrical fire. The limitations of t previous studies include: (1) most existing research focused on gaseous atmospheres rather than solids materials, which is contrary to the actual demand; and (2) the [...] Read more.

The electric fault arc, particularly the series arc, leads to plenty of electrical fire. The limitations of t previous studies include: (1) most existing research focused on gaseous atmospheres rather than solids materials, which is contrary to the actual demand; and (2) the studied external heat sources were restricted to cone heaters and flames, while the electric arc was seldom studied. To overcome these limitations, we developed an experimental platform to investigate the flame behavior when cable insulation material was ignited by the fault arc. We proposed a flame-extracting and noise-reduction algorithm to process the enormous number of photos shot by the high-speed camera. The main obtained findings were: (1) the appropriate size of the structuring element plays an essential role in filtering the flame region in the photos, too small a size resulted in the wrong recognition of incandescent particles, while too large a size made a jagged distortion; (2) the mean flame area increased as the system load grew; (3) The flame size became more prominent, and the flame appeared more frequently in specific locations when the system load increased. The in-depth understanding of flame behavior provided by this work will help to optimize the design of electric systems and disaster prevention reduction. Full article

(This article belongs to the Special Issue Pyrolysis, Ignition, Combustion and Fire Spread of Combustible Materials)

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37 pages, 14706 KiB

Open AccessArticle

Influence of Compartment Fire Behavior at Ignition and Combustion Development Stages on the Operation of Fire Detectors

by Alena Zhdanova, Roman Volkov, Aleksandr Sviridenko, Geniy Kuznetsov and Pavel Strizhak

Fire 2022, 5(3), 84; https://doi.org/10.3390/fire5030084 - 17 Jun 2022

Cited by 7 | Viewed by 2905

Abstract

This paper presents experimental research findings for those involved in the early phase of fire in office buildings. Class A model fires with a reaction area from 5 cm² to 300 cm² were chosen for investigation. To mock up a fire, [...] Read more.

This paper presents experimental research findings for those involved in the early phase of fire in office buildings. Class A model fires with a reaction area from 5 cm² to 300 cm² were chosen for investigation. To mock up a fire, the following combustible materials typical of offices were used: wood pieces, heat-insulated linoleum, paper and cardboard. The main characteristics of a model fire were recorded: temperature in the combustion zone, heat release, time of complete burnout and concentration of flue gas components. Typical trends and histograms of changes of these characteristics over time were presented; stages of ignition, flame combustion and smoldering were illustrated. The key characteristics of fire detector activation at different stages of model fire combustion were analyzed. Dead bands and operation conditions of a group of detectors (smoke, heat, optical, flame), their response time and errors were identified. It has been established that the most effective detectors are flame and smoke detectors. Specific operational aspects of detectors were established when recording the ignition of different types of model fires. The viability of combining at least two detectors to record fire behavior was established. Recommendations were made on using the obtained findings when optimizing the systems for detecting and recording the start of a compartment fire. Full article

(This article belongs to the Special Issue Pyrolysis, Ignition, Combustion and Fire Spread of Combustible Materials)

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