What are the limits of flammability?

Flammability and Explosion Limits – Flammability, explosion, and detonation limits are distinct. Flammability limits refer to the range of compositions, for fixed temperature and pressure, within which an explosive reaction is possible when an external ignition source is introduced.

• This can happen even when the mixture is cold.
• Flammability limits are given in terms of fuel concentration (by volume) at a specified pressure and temperature.
• For example, the lean flammability limit for Jet A (aviation kerosene) in air at sea level is a concentration (by volume or partial pressure) of about 0.7%.

The rich flammability limit is about 4.8% by volume or partial pressure. Flammability limits are not absolute, but depend on the type and strength of the ignition source. Studies on flammability limits of hydrocarbon fuels have shown that the stronger the source of the ignition stimulus, the leaner the mixture that can be ignited.

1. Flammability limits also depend on the type of atmosphere (for example, limits are much wider in oxygen than in air), the pressure, and the temperature of atmosphere.
2. Explosion limits usually refer to the range of pressure and temperature for which an explosive reaction at a fixed composition mixture is possible.

The composition has to be within the flammable range. The reaction is usually initiated by autocatalytic (sometimes called self-heating) reaction at those conditions, without any external ignition source. In practical terms, this means that the mixture needs to be sufficiently hot.

1. Explosion limits are given in terms of a minimum autoignition temperature (AIT) for ignition of fuel injected into hot air.
2. The minimum AIT is strong function of the fuel type (atomic composition and molecular structure), pressure, and fuel concentration.
3. For common hydrocarbon fuels, the minimum AIT ranges between 600C (1350 F) for methane (CH4) to 200C (472F) for dodecane (C12H26).

A minimum AIT of 190C (450F) is used for the purposes of hazard analysis for aviation kerosene. Note that the minimum AIT is much higher than the flash point and much lower than typical hot surface ignition temperatures, which can be as high as 900C (2000F) for common hydrocarbon fuels (Smyth, K.C.; Bryner, N.P.

Combustion Science and Technology, Vol.126, 225-253, 1997). Detonation limits are the range of composition within which detonations have been observed in laboratory and field experiments. Detonation limits are a strong function of mixture composition, initial pressure and temperature but usually considered to be narrower than the flammabilty limits.

In addition, detonation limits are much more strongly dependent on the ignition source, confinement, and the physical size of the experiment than flammability limits. The ability to initiate and propagate a detonation requires a set of critical conditions to be satisfied and despite extensive research into the subject, the limits are empirical in nature.

1. Data on the flammability and explosion limits of liquids and gases are given in Appendix A to Kuchta (1985).
2. Since I often get questions about the flammability of various substances, I have scanned these pages in and made them available as a pdf files.
3. The citation for Kuchta and other sources of flammability data are listed following the definitions.

Data on detonations is available in the Detonation Data Base Digitized pages from Appendix A “Summary of Combustion Properties of Liquid and Gaseous Compounds” (Kuchta 1985) p 71, p 72, p 73, p 74, p 75, p 76, p 77, See below for full text of Bulletin 680.

1. Definitions of properties listed in Appendix A: Mol wt Molar weight, modern term is molar mass.
2. This the mass of the fuel molecule expressed in terms of g/mol or kg/kmol.
3. Specific gravity Density of fuel vapor relative to that of air.
4. Boiling Point (BP) The temperature at which the vapor pressure of a liquid is equal to one standard atmosphere (101.325 kPa).

This is the temperature for the onset of boiling and formation of vapor bubbles on nucleation sites on the container surface. Stoichiometric Concentration (Cst) The ratio of moles of fuel to moles of fuel-air mixture required to get complete oxidation of the fuel to carbon dioxide (CO2) and water (H2O) with no excess oxygen in the products.

• The values given in Kuchta are as a percentage of fuel in the mixture of fuel and air.
• Note that these values are identical for volume, molar, and partial pressure basis for gaseous fuels.
• Heat of formation (Delta Hf) Heat of reaction for formation of fuel from elements at the standard state.
• Expressed in Appendix A in terms of kcal per mole of fuel.

Heat of Combustion (Delta Hc) Heat of reaction for stoichiometric combustion of fuel with oxygen of air. Expressed in Appendix A in terms of kcal per mole of fuel. Flash point This is the minimum temperature at which the vapor above a liquid fuel will first support a combustion transient or “flash”.

The flash point is measured by a standardized test (ASTM D56) using a small quantity (50 cc) of liquid that is slowly heated (about 1 deg C/minute) until a flash is observed when an open flame is dipped down into a covered vapor space. The legal description of flammable is used for all liquids with a flash point less than 100 deg F (37.8 C), and the term combustible is used for liquids with a flash point in excess of 100 deg F (37.8 C).

Autoignition temperature (Minimum AIT) The temperature that a fixed volume of fuel-oxidizer mixture must be heated to before an explosion will take place without an external ignition source, i.e., spark or flame. The values of the minimum AIT used in conventional hazard classifications (e.g., Appendix A of Kuchta) have been measured in a standardized test (ASTM E659) which involves injecting a fuel into a heated flask filled with hot air.

Explosion does not take place immediately when fuel is injected but occurs after a delay of between 5 and 600 s. Flammability Limits (L25 or U25) A fuel-air mixture is flammable when combustion can be started by an ignition source. The main fact is the proportions or composition of the fuel-air mixture.

A mixture that has less than a critical amount of fuel, known as the Lean or Lower Flammability Limit (LFL), or greater than a critical amount of fuel, known as the rich or Upper Flammability Limit (UFL), will not be flammable. The values in Kuchta are given in terms of molar percentages of fuel in the fuel-air mixture at 1 atm and 25 C.

How do you calculate lower flammability limit?

Step 1: Calculate LFL of mixture using Le Chatelier’s rule: Equation B.8.1(a) where xi is the mole fraction of component i having LFL = Li (mol%) in mixture. Step 2: Calculate stoichiometric oxygen Si needed for each mixture component i.

What is flammability limit test?

and vapours – The test determines the lower and upper concentration limits of flammability of chemicals having sufficient vapour pressure to form flammable mixtures in air at atmospheric pressure at the test temperature. Above the upper explosible limit (sometimes called the upper flammable limit) the mixture of substance and air is too rich in fuel (deficient in oxygen) to burn.

Below the lower explosible limit (sometimes called the lower flammable limit) the mixture of substance and air lacks sufficient fuel to burn. The test is based on central electrical ignition in a 12 litre flask with video recording to observe flame propagation. At the limit of flammability testing, a single frame of video may be sufficient to detect combustion flame.

The applicable test standard is ASTM E681.

What is the flammability limit and pressure?

The upper flammability limits of the hydrogen/air mixtures increase with the initial pressure and temperature. The upper flammability limit of the hydrogen/air mixtures at 90 °C and 0.4 MPa reaches 93%, much higher than 76% at 21 °C and 0.1 MPa.

Can you measure flammability?

Vertical and Horizontal Flammability Testing – Flammability test methods measure how easily materials ignite, how quickly they burn and how they react when burned. The materials are placed over a Bunsen burner either vertically or horizontally, depending on the specification.

What are flammability standards?

ASTM’s fire and flammability standards are involved in the testing and evaluation of the ignition, burning, or combustion characteristics of certain materials. Most of these standards are inclined towards the testing of the flammability of interior and exterior building parts, as well as common household and commercial furniture.

These fire and flammability standards are instrumental in the establishment of building codes, insurance requirements, and other fire regulations that govern the use of building materials, as well as in defining the appropriate criteria for the storage, handling, and transport of highly flammable substances.

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What is lean limit of flammability?

Lean flammability limits of alternative aviation fuels , September 2019, 102851 Fuel flammability limit is a specific concentration limit when fuel and air mixture become flammable. Flammability limit has important indications for fire safety. The lean and rich flammability limits are denoted as the minimum and maximum percentage of fuel vapor in air by volume or fuel-air mass ratio that can result in an unexpected fire when an ignition source is present. Outside of this range, ignition and flame propagation cannot take place, The lean flammability limit is more relevant to ground operations of practical fuels such as fuel storage and handling at an airport. The flammability limits of combustible gases such as hydrogen, methane and light hydrocarbon fuels have been reported in the literature. Data for heavy hydrocarbons and practical fuels, however, are sparse. As alternative aviation fuels are being developed, which exhibit different chemical and physical properties than traditional fuels, there is a need to determine their fire-safety properties such as flammability limits. It is essential to understand the flammability limits of new alternative fuels and how they would differ from the limits of conventional petroleum-based fuels such as Jet A. Petroleum-based and alternative aviation fuels usually consist of hundreds of compounds, including n -alkanes, iso-alkanes, cycloalkanes, and aromatics. As such, flammability limits of pure hydrocarbons are also of interest. Additionally, it is desirable to develop models that can predict the fuels flammability limits as a function of their chemical composition. These together will enable researchers and firefighters to collaborate in determining both, the tactical responses and the strategic improvements, needed to effectively combat alternative aviation fuel fires. Jones et al., performed one of the earliest experiments to measure the flammability limits of aviation fuels using a long glass tube. The concentration of the fuel vapor was determined by measuring the partial pressure of the fuel vapor inside the glass tube. The fuel vapor/air mixture was ignited with a spark discharge. The lean flammability limits of two aviation gasoline fuels (grade 100/130 and 115/145) and two jet fuels (JP-1 and JP-3) were determined at various initial temperatures and pressures. The lean limit for these fuels was reported in the range of 0.037–0.041 in terms of fuel-air mass ratio at an initial temperature of 149 °C and atmospheric pressure. Using the same method as Jones et al., Coward et al. later measured the lean flammability limits of several pure heavy hydrocarbon fuels including n-heptane, iso-octane, and n-decane. Egerton and Powling measured the lean limit of the higher hydrocarbons including n-heptane, n-octane, and iso-octane in the air using a glass tube similar to that of Jones et al., However, their values are slightly higher than those obtained by Coward et al., Zabetakis later carried out similar experiments to measure the flammability limits of aviation fuels as well as pure fuels. This work extended previous results from Jones et al. and Coward et al. to include more chemicals and initial conditions. Most recently, Shepherd et al. examined the flammability limits and ignition energy of Jet A vapor in air at various conditions, as part of the investigation of the TWA flight 800 crash that had happened in 1996. It was found that the lean flammability limit of Jet A was within the range of 0.035–0.040 in terms of fuel-air mass ratio at a temperature of 100 °C and a pressure of 58.5 MPa – the conditions at the altitude where the crash started. However, the TWA 800 accident involved preferential vaporization of the light species, which then ignited. It should be noted here, that the experiments in this paper have no such preferential vaporization but burn the entire fuel mixture. Barnett and Hibbard provided a review on the flammability limits of several jet fuels (JP-1, JP-3, JP-4, and JP-5). Based on the experimental data available in the literature, they proposed a correlation between the flammability limit, the molecular weight and the combustion heat of the fuel. The results showed that the predicted lean flammability limit was around 0.035 in terms of fuel-air mass ratio for typical jet fuels. Five alternative blending components have recently been approved by ASTM, for blending (with varying ratios) with conventional jet fuels, including Hydroprocessed Esters and Fatty Acids (HEFA), Synthesized Iso-Paraffins (SIP), and Fischer-Tropsch Iso-Paraffinic Kerosene (FT-IPK). The purpose of the present work was to experimentally determine the lean flammability limit of Jet A, HEFA, SIP and FT-IPK under various initial temperatures and pressures. Currently utilized fuels are mixtures of hundreds of compounds and their fuel flammability limits depend on the chemical composition. Therefore, simpler mixtures of surrogates were also measured and compared to the lean limits of sample fuels. These surrogates included four organic compounds ( n -heptane, n -decane, n -dodecane, and iso-octane) as the major components of transportation fuels (therefore, they are referred to as fuels in the text). The pure hydrocarbon compounds included n-heptane (Spectrum Chemicals, 99+% pure), n-decane (Spectrum Chemicals, 99+% pure), n-dodecane (Spectrum Chemicals, 99+% pure), and iso-octane (Spectrum Chemicals, 99+% pure). The petroleum jet fuel (Jet A), Fischer-Tropsch Iso-Paraffinic Kerosene (FT-IPK), and Hydroprocessed Esters and Fatty Acids (HEFA) were provided by the Wright-Patterson Air Force Base, Dayton, Ohio. Synthesized Iso-Paraffins from Hydroprocessed Fermented Sugars (SIP) was obtained Jet A was composed of all main hydrocarbon classes (Table 2) FT-IPK was mostly composed of iso-alkanes and cycloalkanes, aromatic content was negligible. HEFA50 was also composed of all main hydrocarbon groups, due to the fact, it was 50:50 vol% mixture with Jet A. SIP was unique in its composition as it predominantly contained iso-alkane, namely farnesane (2,6,10-trimethyl-dodecane). The lean flammability limit of the four pure hydrocarbon fuels at various initial temperatures and atmospheric The lean flammability limit of four pure hydrocarbon compounds ( n -heptane, iso-octane, n -decane, and n -dodecane), Jet A, and three alternative aviation fuels (HEFA50, SIP, and FT-IPK) were measured at various temperatures and pressures. In terms of fuel vapor percentage in mixture by volume, the lean flammability limit decreased in the order: n -heptane>iso-octane> n -decane>FT-IPK>Jet A>HEFA50> n -dodecane>SIP. The lean flammability limit decreases with increasing molecular weight. As the initial The authors certify that they have NO affiliations with or involvement in any organization or entity with any financial interest or non-financial interest such as personal or professional relationships in the subject matter or materials discussed in this manuscript. This work has been supported by the Federal Aviation Administration through the Partnership to Enhance General Aviation Safety, Accessibility and Sustainability (PEGASAS) center with Mr. Keith Bagot as the technical monitor.

P. Vozka et al. M. Vidal et al. T. Ma M.G. Zabetakis et al. H.-J. Liaw et al. S.R. Turns G.W. Jones et al. H.F. Coward et al. A. Egerton et al.

Hydrogen can be used in conjunction with aviation kerosene in aircraft engines. To this end, this study uses n-decane/hydrogen mixtures to investigate the explosion characteristics of aviation kerosene/hydrogen in a constant volume combustion chamber with different hydrogen addition ratios (0, 0.2, 0.4), wide effective equivalence ratios (0.7–1.7), an initial temperature of 470 K, and initial pressures of 1 and 2 bar. The results show that the explosion pressure and explosion time decrease linearly with increasing hydrogen addition ratio. The effect of initial pressure is also discussed. A comparison of the adiabatic explosion pressures indicates that the hydrogen addition effect varies at different initial pressures and effective equivalence ratios owing to heat loss. In addition, the maximum pressure rise rate and deflagration index increase with increasing hydrogen concentration, which is more obvious for rich mixtures and high hydrogen concentrations. Synthesized iso-paraffins (SIP) are compounds that can be blended with traditional aviation fuels up to 10% vol. to reduce greenhouse gas emissions. The safety properties of these fuels need to be determined to guarantee their reliable utilization. These properties include the upper flammability limit (UFL). The objective was to determine experimentally the UFL in air of SIP, jet fuel, and mixtures containing 10% (F10) and 50% (F50) of SIP on a mass basis, respectively. The initial conditions involved different initial temperatures and pressures. The experimental configuration followed the ASTM E681 standard. The temperature range was from 420 to 470 K and the pressure range was from 101.3 kPa to 20 kPa. The results show that the UFLs of the tested compounds have a second-order tendency with respect to pressure and constant temperature. The F10 mixture has a significant reduction of the UFL at 20 kPa. The experimental results were fitted by using regression models and empirical correlations which allow the determination of UFLs at different initial temperatures and pressures. Concern of environmental and energy crisis all over the world have caused the attention on reduction fuel consumption of IC engines used on trucks. This investigation mainly focuses on reducing fuel consumption heavy duty vehicles by using correcting system of inlet air, and established the mathematical dependence of operational fuel consumption trucks from temperature, pressure, density and humidity of air at the inlet of the engine. And finally, was determine the temperature optimal range of the air at the inlet to the diesel engine, which ensures minimum fuel consumption. Experimental studies on trucks equipped with of the air correcting parameters system at the engine inlet confirmed reduced fuel consumption by 5 to 16%. Hydrogen impacts on lean flammability limits and the burning characteristics of n-decane, a kerosene surrogate, were studied using a spherical combustion chamber and Chemkin software at 460 K and 100 kPa. Laminar flame propagated spherically at λ = 0.8–1.3 by using 50 mJ IE, whereas further leaner mixture (λ ≥ 1.4) could be ignited at 1000 mJ. However, the wrinkles appeared on flame morphology thanks to higher IE. The effect of IE on flame morphology reduced with increasing the value of λ. In contrast, the flame distortion enhanced as lifting IE, 1000–3000 mJ. Near lean limit, the spherical flame appeared initially from 0 ms to 20 ms. When time increased from 20 ms, it buoyed due to slow flame speed and rapid radiation losses. Eventually, it disappeared at t ≈ 200 ms, and the mixture could not burn completely. Lean limits of n-decane were found λ = 1.6, λ = 1.7, and λ = 1.8 at 1000 mJ, 2000 mJ, and 3000 mJ, respectively. It linearly extended by 0.5 λ with 70% H 2 addition (0–70%) and enormously enlarged by 1.3 λ with 20% H 2 addition (70–90%). IE, 1000–3000 mJ, extended the lean limit by 0.2 λ. H radical produced greatly from H 2 and CO by consuming OH, whereas it consumed by translating formaldehyde and oxygen into aldehyde, O and OH. OH produced significantly from the consumption of H and hydroperoxyl radicals. By lifting hydrogen, H and OH increased rapidly, which enhanced the reaction rates of dominant intermediates. Consequently, the lean limit improved. The creation of alternative fuels to reduce CO2 emissions in the aeronautical sector necessitates the determination of their safety properties, among which are their Flammability Limits. Synthesized Iso-Paraffins (SIP) are blending components that have already been approved for blending with traditional aviation fuel by up to 10 vol%. Therefore, this manuscript is aimed at experimentally determining the Lower Flammability Limit (LFL) of SIP, jet fuel and mixtures of 10% (F10) and 50% (F50) in mass of SIP at atmospheric and reduced pressures with air. For this purpose, an experimental bench was built in accordance with American Society for Testing and Materials, ASTM, The LFL of the samples was initially determined at a pressure of 101.3 kPa and high temperatures. Afterward, the LFL of samples was determined at reduced pressures, i.e.80, 60, 40 and 20 kPa, and also high temperatures. For this analysis, 316 tests were performed. For a better understanding of the experimental results, additional material is attached, presenting the temperatures and the volumes used in carrying out each test. Finally, adjustment equations based on the experimental results of this manuscript for SIP, jet fuel, and their mixtures, were presented as a function of temperature and atmospheric pressure.

Fires in confined spaces are of major concern in fire safety engineering. Indeed, fires with ensuing fatalities, generally occur in apartment or room fires. The decision and response time of rescue teams mainly results from empirical understanding. However, since compartment fires are multi-physical and multi-scale problems, a clear fundamental approach is needed. One of the main issues concerns the transition from localized to generalized fire. The most important vector leading to generalized fires is smoke. Indeed, smoke temperature is very high and many species i.e. burned and unburned gases are already or might mix. In this study, an experimental facility composed of a maritime container is set-up. It allows enclosure fires up to 1 MW of power. This power is representative of moderate room fires. The global behavior of the smoke is investigated through the analysis of mean experimental temperature fields, smoke dynamics by large scale PIV as well as numerical simulations. For numerical simulations, the Fire Dynamics Simulator (FDS) software is used. The experimental measurements are used to evaluate the validity of FDS in under-ventilated conditions. It is observed that FDS code is able to reproduce both temperature and velocity data of enclosure fires with accuracy depending on the power to volume ratio. A criterion capable to discriminate the ventilation status of confined fire is observed and discussed. Combustion characteristics in a hydrogen fuelled single-element lean direct injection (LDI) combustor for low emission gas turbine engine are computationally investigated. A single-element LDI combustor was produced and simulated with steady-state Reynolds-averaged Navier–Stokes reacting computations. Reacting computations of the single-element LDI combustor were performed with an augmented reduced 23-step reaction mechanism for hydrogen/air. A realizable k − ε model was used to obtain turbulence closure. For the single-element LDI combustor with different equivalence ratio, the effective area, axial velocity, total pressure drop coefficient, total temperature, mass fraction of OH, emission index of pollutant NO (EI NO ) were achieved and discussed. This research has developed a soap-derived biokerosene (SBK) production process to produce hydrocarbons for use as an aviation alternative fuel. The SBK production process was developed in keeping with the conditions of the available technologies and investment while leveraging the advantage of an abundant national feedstock resource that is found in Indonesia in particular, and tropical emerging countries in general. The production of SBK comprises two main processes: saponification and thermal decarboxylation to convert coconut oil into hydrocarbons. The composition of SBK was analyzed and compared to that of Jet A1. Additionally, the critical properties of SBK and several of its blends with Jet A1 were measured and collated with the established jet fuel standard. The results show that SBK can be blended directly with Jet A1 at up to 10 vol.% to meet selected properties: distillation temperature, flash point, density, net heating value, viscosity, freezing point, smoke point, and oxidation stability. From this study, it can be concluded that SBK is feasible for use as a drop-in aviation fuel when blended with conventional jet fuel. Thus, the SBK production is highly promising for use in tropical countries to produce aviation biofuels, given the appropriate technologies and feedstock resources. In order to reduce the emission of carbon dioxide, gas turbine power station will expect to use more clean fuels in the future, especially those like hydrogen. Hydrogen-rich fuel(syngas) combustion characteristics of the novel counter dual-swirl gas turbine combustor under fixed calorific value input were studied by experiment and numerical simulation. PIV and temperature rake were used respectively to obtain the velocity and temperature distribution in the combustion chamber. The turbulence model of Reynolds stress and the kinetic model of detailed chemical syngas combustion were used simultaneously in the computational simulations. Based on the obtained results, it was found that there is a reasonable agreement between the numerical results and the experimental data. The analysis shows that the flow field and temperature field of the combustor were almost unaffected by the change of hydrogen content and shows a nearly identical distribution structure under all conditions with hydrogen content below 90%; but when the H 2 content reaches 90%, the above characteristic plots were significantly changed. As the H 2 content in the fuel increases, on the center line of the combustor, the jet velocity of the fuel decreased, the temperature of the gas flow increased, the recovery coefficient of total pressure decreased, and the temperature distribution at the combustor outlet became more uniform. In addition, it is also found that the syngas turbine with the same output power consumed less fuel than the gas turbine with hydrocarbon fuel. This paper provides reference for the study of hydrogen-rich syngas turbine and the application of hydrogen-rich fuel in combustor of energy system. We present an approach for predicting the lower flammability limits of combustible gas in air. The influence of initial pressure and temperature on lower flammability limit has been examined in this study. The lower flammability limits of methane, ethylene and propane in air are estimated numerically at the pressure from one to 100 bar and the temperature from ambient to 1200 K. It was found that the predicted LFLs of methane, ethylene and propane decrease slightly with the elevated pressure at the high temperature. The LFLs variation for methane-air mixture is 0.17, 0.18, 0.18 volume% with the initial pressure from one to 100 bar at the initial temperature of 800 K, 1000 K and 1200 K respectively, which is significantly higher than that at lower temperature. And the LFL of methane-air mixture at 1200 K and 100 bar reaches 1.03 volume% which is much lower than that at 1 bar and ambient temperature. On the other hand, the LFLs variation is 0.11–0.12 volume% for ethylene-air mixture and 0.06–0.07 volume% for propane-air mixture with the initial temperature from 800 K to 1200 K at the same range of pressure. The LFL values at high temperatures and pressures represent higher risk of explosion.

: Lean flammability limits of alternative aviation fuels

What are upper and lower flammability limits?

What is a Flammability Limit? – The amount of combustible gas in an air mixture when the mixture is flammable is known as the flammability limit or flammable limit. Gas mixtures that consist of combustible, oxidizing, or inert gases are only flammable under certain conditions.

• The lower flammability limit (LFL) identifies the smallest mixture able to sustain a flame.
• The upper flammable limit (UFL) identifies the richest flammable mixture.
• A quantifiable difference exists between the flammability limit and explosive limit.
• In specialized process applications such as combustion engines, achieving the perfect combustible or explosive mixture is important.

However, in engineering a gas detection system, the flammable gas cloud is turbulent and the exact mixture can greatly vary. As such, many professionals interchange the term flammability limit (UFL/LFL) and explosive limit (UEL/LEL) depending on their education or geographic location.

What is a lower flammability limit?

2.1 Dispersion – A leak from a pressurized hydrogen system will mix with air and become diluted to the point where it is no longer flammable at some distance from the leak point. The lower flammability limit was discussed previously as a property of a fuel.

This property is found by igniting stagnant, well-mixed blends of air and fuels. A leak from a hydrogen system will be anything but stagnant and well mixed. A high-pressure leak of hydrogen will become choked at the leak point, meaning the gas will flow at a sonic velocity and remain at a pressure above ambient pressure at the leak plane.

A complex series of shock waves will form at the leak exit, and downstream from the shocks, highly turbulent mixtures will be present in the form of a turbulent diffusion jet. Leaks from liquid hydrogen systems are often at a high enough pressure (roughly double atmospheric pressure) that they will also be choked.

Even at low pressure, as liquid hydrogen mixes with warm air, there is a rapid volume change as the phase changes, creating highly turbulent conditions. As cryogenic hydrogen mixes with the warm ambient air, the flow will also be highly turbulent. Air is entrained along the length of the jet, and the mean concentration decreases as distance from the leak increases.

The highest mean concentration will be along the centerline of the jet (as opposed to the jet periphery). It has been shown experimentally that while an ignition kernel can form in a region of the diffusion jet with a mean mole fraction close to the lower flammability limit, a jet flame will not form unless the mean mole fraction at the ignition point is above 8% for these highly turbulent diffusion jets,

What is the LEL test method?

Minimum explosible concentration and lower explosible limit – The lower explosible limit – also known as the minimum explosible concentration or MEC – is the lowest concentration of dust cloud that will allow combustion. Testing follows EN 14034-3:2006 (determination of the lower explosible limit LEL of dust clouds) and is carried out in the 20 litre sphere apparatus.10 grams of combustible dust is placed in the dust container and the explosion chamber is evacuated to 0.4 bar.

• An automatic test sequence is initiated to pressurise the dust container to 20 bar and activate the two chemical igniters, each having an energy of 1 kJ, 60 msec after the dust has been dispersed.
• A test series is undertaken with a systematic decrease of the dust concentration until no ignition of the dust / air mixture is observed.

The test is repeated to ensure no ignition is found in three consecutive tests. An ignition is deemed to have occurred if the maximum explosion pressure is at or above 0.5 bar. The lower explosible limit may be used as an explosion prevention method in areas where the explosive concentration of dust can be reliably controlled.

Why is flammability limit important?

Flammability Limits The range of gas or vapor amounts in air that will burn or explode if a flame or other ignition source is present. Importance: The range represents an unsafe gas or vapor mixture with air that may ignite or explode. Generally, the wider the range the greater the fire potential.

Why do we test for flammability?

It happens with some regularity – news of a fire or explosion in an industrial facility that causes considerable property damage or, even worse, worker casualties. It has been said before, but continues to remain true, even one incident of fires and explosions resulting from an employee in the building mixing chemicals, is one too many. The all too frequent occurrence of fires and explosions in the process industries that use flammable materials is typically the result of a couple of factors, an explosive mixture being present in the vapor space, lack of knowledge of the properties of the chemical’s inherent safety implications or inadequate safety procedures,

• And, that in a nutshell, is why flammability testing is important.
• In order to minimize the risk of fire or explosion, it is important to evaluate the flammability characteristics of the material to understand key characteristics such as the lower flammability limit, upper flammability limit, limiting oxygen concentration and deflagration index.

Simply put, these are defined as:

Lower Flammability limit (LFL) – the lowest concentration at which a mixture of flammable vapor or gas and air is flammable Upper Flammability Limit (UFL) – the highest concentration at which a mixture of flammable vapor or gas and air is flammable Limiting Oxygen Concentration (LOC) – the minimum concentration of oxygen required to produce a flammable event when mixed with a flammable vapor or gas in any concentration. Deflagration Index (K G ) – the volume-normalized maximum rate of pressure rise for a flammable mixture

A variety of different flammability tests can be performed to allow for determination of these characteristics, and the understanding of these conditions is essential when implementing proper safety practices. When conducting flammability testing, it is important that customers communicate what data is being sought so that testing can be properly designed in order to determine the necessary flammability property of a chemical mixture.

• A good flammability testing regime will take into consideration the many different variables that affect the flammability of a specific chemical: oxidizing environment, temperature, pressure, ignition energy, size and geometry of the vessel, gas composition, etc.
• There are a variety of pressure vessels varying in size and geometry to use for flammability testing purposes dependent on the particular need.

The choice (spherical, cylindrical, large, small, glass, steel, etc.) depends on the particular test design. A well defined ignition source is also necessary, as is a good data acquisition system for monitoring pressure and temperature. Accounting for these variables can result in test data that is much more applicable to your specific process than information taken from literature.

Experts are happy to have a discussion with you about your flammable hazard concerns and work with you on designing tests that get you the information you need. The goal is to provide you with specific data – not just data. For more information regarding how flammability testing might be important to you, contact the flammability department at [email protected],

You can also subscribe to our quarterly Process Safety News below! Topics: flammable vapor, flammable gas, LFL, Flammability, industrial explosion, industrial fire, testing

What is 10% LEL?

Methane LEL – Let’s have a look at how we can interpret this measurement. Methane LEL is 4.4% volume-per-volume, which means that if the concentration of methane in 1 cubic metre of air exceeds 4.4%, the mixture will explode. If the alarm goes off at 10% LEL, it means that the detector will calculate 10% of 4.4%, being 0.44% of the cubic metre of air.

What is difference between LEL and LFL?

The minimum concentration of a substance that propagates a flame through a homogeneous mixture of the substance and air under the specified test conditions. The LFL is sometimes referred to as LEL ( Lower Explosive Limit ). For the purposes of this definition, LFL and LEL are identical.

What is critical flammability ratio?

ASHRAE funds refrigerant flammability tests USA: ASHRAE has awarded a $195,000 grant to the University of Maryland to more accurately determine refrigerant flammability. The project, titled 1717-TRP, Improve the Accuracy and Reproducibility of the Flammability Test Method ASTM E681, has been awarded to the university’s Department of Fire Protection Engineering (FPE).

• ASTM E681 is the standard test method to determine refrigerant flammability.
• The move towards the adoption of low global warming potential refrigerants will increase the use of flammable and “mildly flammable’ refrigerants.
• Classifying some of these new gases, particularly some of the new blends can be problematic.

According to ASHRAE, ASTM E681 is insufficient to accurately and precisely determine their flammability. Revisions to the test method are needed to correct this and allow SSPC 34 to properly identify their safety classification for use by the industry.

This project supports the ASHRAE Research Strategic Plan 2010-2015 for support of research into new alternative low global warming potential refrigerants by addressing difficulties experienced in their flammability assessment and identifying corrections needed in the test approach to result in proper safety data development and classification for flammability.

ASHRAE’s A2L “mildly flammable” classification is an example. The A2L designation requires a lower flammability limit above 3.5%, a heat of combustion below 19kJ/g, and a laminar flame speed of less than 10cm/s. Blends of A2L and A1 refrigerants may result in A1 classification and low GWP.

• The ASTM E681 test is essential in determining whether a refrigerant is mildly flammable (A2L) or not flammable (A1).
• According to ASHRAE, some of the 2L refrigerants result in flames that are less stable, making flammability property measurement more difficult.
• In particular, it says, when blending one of these mildly flammable refrigerants with ones that are non-flammable it has been difficult to accurately determine the ratio of the components that form the boundary between a non-flammable and flammable blend.

This ratio is termed the critical flammability ratio or CFR. For a given CFR of a blend, there was a wide variation in the test results causing difficulty in classifying the blend in ASHRAE Standard 34 for flammability which would be a safety concern that impacts Standard 15 and codes.

The research will be led by the FPE’s associate professor Peter Sunderland and research associate Dr Vivien Lecoustre, and will run until October 2016. The project is divided into five tasks: Develop a complete understanding of the ASTM E681 test method; set up a test facility and perform ASTM E681 testing; utilise CFD to aid in understanding the problem and in finding solutions; recommend and justify improvements to ASTM E681; and document these findings and present them to the ASHRAE community.

: ASHRAE funds refrigerant flammability tests

What is the ASTM standard for flammability?

Flammability ASTM D635 standards assess the ignition or combustion properties of certain materials such as plastics. ASTM D635 flammability test determines the rate of burning of substantial thick-walled plastics.

What is 10% LEL?

Methane LEL – Let’s have a look at how we can interpret this measurement. Methane LEL is 4.4% volume-per-volume, which means that if the concentration of methane in 1 cubic metre of air exceeds 4.4%, the mixture will explode. If the alarm goes off at 10% LEL, it means that the detector will calculate 10% of 4.4%, being 0.44% of the cubic metre of air.

What is lean limit of flammability?

Lean flammability limits of alternative aviation fuels , September 2019, 102851 Fuel flammability limit is a specific concentration limit when fuel and air mixture become flammable. Flammability limit has important indications for fire safety. The lean and rich flammability limits are denoted as the minimum and maximum percentage of fuel vapor in air by volume or fuel-air mass ratio that can result in an unexpected fire when an ignition source is present. Outside of this range, ignition and flame propagation cannot take place, The lean flammability limit is more relevant to ground operations of practical fuels such as fuel storage and handling at an airport. The flammability limits of combustible gases such as hydrogen, methane and light hydrocarbon fuels have been reported in the literature. Data for heavy hydrocarbons and practical fuels, however, are sparse. As alternative aviation fuels are being developed, which exhibit different chemical and physical properties than traditional fuels, there is a need to determine their fire-safety properties such as flammability limits. It is essential to understand the flammability limits of new alternative fuels and how they would differ from the limits of conventional petroleum-based fuels such as Jet A. Petroleum-based and alternative aviation fuels usually consist of hundreds of compounds, including n -alkanes, iso-alkanes, cycloalkanes, and aromatics. As such, flammability limits of pure hydrocarbons are also of interest. Additionally, it is desirable to develop models that can predict the fuels flammability limits as a function of their chemical composition. These together will enable researchers and firefighters to collaborate in determining both, the tactical responses and the strategic improvements, needed to effectively combat alternative aviation fuel fires. Jones et al., performed one of the earliest experiments to measure the flammability limits of aviation fuels using a long glass tube. The concentration of the fuel vapor was determined by measuring the partial pressure of the fuel vapor inside the glass tube. The fuel vapor/air mixture was ignited with a spark discharge. The lean flammability limits of two aviation gasoline fuels (grade 100/130 and 115/145) and two jet fuels (JP-1 and JP-3) were determined at various initial temperatures and pressures. The lean limit for these fuels was reported in the range of 0.037–0.041 in terms of fuel-air mass ratio at an initial temperature of 149 °C and atmospheric pressure. Using the same method as Jones et al., Coward et al. later measured the lean flammability limits of several pure heavy hydrocarbon fuels including n-heptane, iso-octane, and n-decane. Egerton and Powling measured the lean limit of the higher hydrocarbons including n-heptane, n-octane, and iso-octane in the air using a glass tube similar to that of Jones et al., However, their values are slightly higher than those obtained by Coward et al., Zabetakis later carried out similar experiments to measure the flammability limits of aviation fuels as well as pure fuels. This work extended previous results from Jones et al. and Coward et al. to include more chemicals and initial conditions. Most recently, Shepherd et al. examined the flammability limits and ignition energy of Jet A vapor in air at various conditions, as part of the investigation of the TWA flight 800 crash that had happened in 1996. It was found that the lean flammability limit of Jet A was within the range of 0.035–0.040 in terms of fuel-air mass ratio at a temperature of 100 °C and a pressure of 58.5 MPa – the conditions at the altitude where the crash started. However, the TWA 800 accident involved preferential vaporization of the light species, which then ignited. It should be noted here, that the experiments in this paper have no such preferential vaporization but burn the entire fuel mixture. Barnett and Hibbard provided a review on the flammability limits of several jet fuels (JP-1, JP-3, JP-4, and JP-5). Based on the experimental data available in the literature, they proposed a correlation between the flammability limit, the molecular weight and the combustion heat of the fuel. The results showed that the predicted lean flammability limit was around 0.035 in terms of fuel-air mass ratio for typical jet fuels. Five alternative blending components have recently been approved by ASTM, for blending (with varying ratios) with conventional jet fuels, including Hydroprocessed Esters and Fatty Acids (HEFA), Synthesized Iso-Paraffins (SIP), and Fischer-Tropsch Iso-Paraffinic Kerosene (FT-IPK). The purpose of the present work was to experimentally determine the lean flammability limit of Jet A, HEFA, SIP and FT-IPK under various initial temperatures and pressures. Currently utilized fuels are mixtures of hundreds of compounds and their fuel flammability limits depend on the chemical composition. Therefore, simpler mixtures of surrogates were also measured and compared to the lean limits of sample fuels. These surrogates included four organic compounds ( n -heptane, n -decane, n -dodecane, and iso-octane) as the major components of transportation fuels (therefore, they are referred to as fuels in the text). The pure hydrocarbon compounds included n-heptane (Spectrum Chemicals, 99+% pure), n-decane (Spectrum Chemicals, 99+% pure), n-dodecane (Spectrum Chemicals, 99+% pure), and iso-octane (Spectrum Chemicals, 99+% pure). The petroleum jet fuel (Jet A), Fischer-Tropsch Iso-Paraffinic Kerosene (FT-IPK), and Hydroprocessed Esters and Fatty Acids (HEFA) were provided by the Wright-Patterson Air Force Base, Dayton, Ohio. Synthesized Iso-Paraffins from Hydroprocessed Fermented Sugars (SIP) was obtained Jet A was composed of all main hydrocarbon classes (Table 2) FT-IPK was mostly composed of iso-alkanes and cycloalkanes, aromatic content was negligible. HEFA50 was also composed of all main hydrocarbon groups, due to the fact, it was 50:50 vol% mixture with Jet A. SIP was unique in its composition as it predominantly contained iso-alkane, namely farnesane (2,6,10-trimethyl-dodecane). The lean flammability limit of the four pure hydrocarbon fuels at various initial temperatures and atmospheric The lean flammability limit of four pure hydrocarbon compounds ( n -heptane, iso-octane, n -decane, and n -dodecane), Jet A, and three alternative aviation fuels (HEFA50, SIP, and FT-IPK) were measured at various temperatures and pressures. In terms of fuel vapor percentage in mixture by volume, the lean flammability limit decreased in the order: n -heptane>iso-octane> n -decane>FT-IPK>Jet A>HEFA50> n -dodecane>SIP. The lean flammability limit decreases with increasing molecular weight. As the initial The authors certify that they have NO affiliations with or involvement in any organization or entity with any financial interest or non-financial interest such as personal or professional relationships in the subject matter or materials discussed in this manuscript. This work has been supported by the Federal Aviation Administration through the Partnership to Enhance General Aviation Safety, Accessibility and Sustainability (PEGASAS) center with Mr. Keith Bagot as the technical monitor.

P. Vozka et al. M. Vidal et al. T. Ma M.G. Zabetakis et al. H.-J. Liaw et al. S.R. Turns G.W. Jones et al. H.F. Coward et al. A. Egerton et al.

Hydrogen can be used in conjunction with aviation kerosene in aircraft engines. To this end, this study uses n-decane/hydrogen mixtures to investigate the explosion characteristics of aviation kerosene/hydrogen in a constant volume combustion chamber with different hydrogen addition ratios (0, 0.2, 0.4), wide effective equivalence ratios (0.7–1.7), an initial temperature of 470 K, and initial pressures of 1 and 2 bar. The results show that the explosion pressure and explosion time decrease linearly with increasing hydrogen addition ratio. The effect of initial pressure is also discussed. A comparison of the adiabatic explosion pressures indicates that the hydrogen addition effect varies at different initial pressures and effective equivalence ratios owing to heat loss. In addition, the maximum pressure rise rate and deflagration index increase with increasing hydrogen concentration, which is more obvious for rich mixtures and high hydrogen concentrations. Synthesized iso-paraffins (SIP) are compounds that can be blended with traditional aviation fuels up to 10% vol. to reduce greenhouse gas emissions. The safety properties of these fuels need to be determined to guarantee their reliable utilization. These properties include the upper flammability limit (UFL). The objective was to determine experimentally the UFL in air of SIP, jet fuel, and mixtures containing 10% (F10) and 50% (F50) of SIP on a mass basis, respectively. The initial conditions involved different initial temperatures and pressures. The experimental configuration followed the ASTM E681 standard. The temperature range was from 420 to 470 K and the pressure range was from 101.3 kPa to 20 kPa. The results show that the UFLs of the tested compounds have a second-order tendency with respect to pressure and constant temperature. The F10 mixture has a significant reduction of the UFL at 20 kPa. The experimental results were fitted by using regression models and empirical correlations which allow the determination of UFLs at different initial temperatures and pressures. Concern of environmental and energy crisis all over the world have caused the attention on reduction fuel consumption of IC engines used on trucks. This investigation mainly focuses on reducing fuel consumption heavy duty vehicles by using correcting system of inlet air, and established the mathematical dependence of operational fuel consumption trucks from temperature, pressure, density and humidity of air at the inlet of the engine. And finally, was determine the temperature optimal range of the air at the inlet to the diesel engine, which ensures minimum fuel consumption. Experimental studies on trucks equipped with of the air correcting parameters system at the engine inlet confirmed reduced fuel consumption by 5 to 16%. Hydrogen impacts on lean flammability limits and the burning characteristics of n-decane, a kerosene surrogate, were studied using a spherical combustion chamber and Chemkin software at 460 K and 100 kPa. Laminar flame propagated spherically at λ = 0.8–1.3 by using 50 mJ IE, whereas further leaner mixture (λ ≥ 1.4) could be ignited at 1000 mJ. However, the wrinkles appeared on flame morphology thanks to higher IE. The effect of IE on flame morphology reduced with increasing the value of λ. In contrast, the flame distortion enhanced as lifting IE, 1000–3000 mJ. Near lean limit, the spherical flame appeared initially from 0 ms to 20 ms. When time increased from 20 ms, it buoyed due to slow flame speed and rapid radiation losses. Eventually, it disappeared at t ≈ 200 ms, and the mixture could not burn completely. Lean limits of n-decane were found λ = 1.6, λ = 1.7, and λ = 1.8 at 1000 mJ, 2000 mJ, and 3000 mJ, respectively. It linearly extended by 0.5 λ with 70% H 2 addition (0–70%) and enormously enlarged by 1.3 λ with 20% H 2 addition (70–90%). IE, 1000–3000 mJ, extended the lean limit by 0.2 λ. H radical produced greatly from H 2 and CO by consuming OH, whereas it consumed by translating formaldehyde and oxygen into aldehyde, O and OH. OH produced significantly from the consumption of H and hydroperoxyl radicals. By lifting hydrogen, H and OH increased rapidly, which enhanced the reaction rates of dominant intermediates. Consequently, the lean limit improved. The creation of alternative fuels to reduce CO2 emissions in the aeronautical sector necessitates the determination of their safety properties, among which are their Flammability Limits. Synthesized Iso-Paraffins (SIP) are blending components that have already been approved for blending with traditional aviation fuel by up to 10 vol%. Therefore, this manuscript is aimed at experimentally determining the Lower Flammability Limit (LFL) of SIP, jet fuel and mixtures of 10% (F10) and 50% (F50) in mass of SIP at atmospheric and reduced pressures with air. For this purpose, an experimental bench was built in accordance with American Society for Testing and Materials, ASTM, The LFL of the samples was initially determined at a pressure of 101.3 kPa and high temperatures. Afterward, the LFL of samples was determined at reduced pressures, i.e.80, 60, 40 and 20 kPa, and also high temperatures. For this analysis, 316 tests were performed. For a better understanding of the experimental results, additional material is attached, presenting the temperatures and the volumes used in carrying out each test. Finally, adjustment equations based on the experimental results of this manuscript for SIP, jet fuel, and their mixtures, were presented as a function of temperature and atmospheric pressure.

Fires in confined spaces are of major concern in fire safety engineering. Indeed, fires with ensuing fatalities, generally occur in apartment or room fires. The decision and response time of rescue teams mainly results from empirical understanding. However, since compartment fires are multi-physical and multi-scale problems, a clear fundamental approach is needed. One of the main issues concerns the transition from localized to generalized fire. The most important vector leading to generalized fires is smoke. Indeed, smoke temperature is very high and many species i.e. burned and unburned gases are already or might mix. In this study, an experimental facility composed of a maritime container is set-up. It allows enclosure fires up to 1 MW of power. This power is representative of moderate room fires. The global behavior of the smoke is investigated through the analysis of mean experimental temperature fields, smoke dynamics by large scale PIV as well as numerical simulations. For numerical simulations, the Fire Dynamics Simulator (FDS) software is used. The experimental measurements are used to evaluate the validity of FDS in under-ventilated conditions. It is observed that FDS code is able to reproduce both temperature and velocity data of enclosure fires with accuracy depending on the power to volume ratio. A criterion capable to discriminate the ventilation status of confined fire is observed and discussed. Combustion characteristics in a hydrogen fuelled single-element lean direct injection (LDI) combustor for low emission gas turbine engine are computationally investigated. A single-element LDI combustor was produced and simulated with steady-state Reynolds-averaged Navier–Stokes reacting computations. Reacting computations of the single-element LDI combustor were performed with an augmented reduced 23-step reaction mechanism for hydrogen/air. A realizable k − ε model was used to obtain turbulence closure. For the single-element LDI combustor with different equivalence ratio, the effective area, axial velocity, total pressure drop coefficient, total temperature, mass fraction of OH, emission index of pollutant NO (EI NO ) were achieved and discussed. This research has developed a soap-derived biokerosene (SBK) production process to produce hydrocarbons for use as an aviation alternative fuel. The SBK production process was developed in keeping with the conditions of the available technologies and investment while leveraging the advantage of an abundant national feedstock resource that is found in Indonesia in particular, and tropical emerging countries in general. The production of SBK comprises two main processes: saponification and thermal decarboxylation to convert coconut oil into hydrocarbons. The composition of SBK was analyzed and compared to that of Jet A1. Additionally, the critical properties of SBK and several of its blends with Jet A1 were measured and collated with the established jet fuel standard. The results show that SBK can be blended directly with Jet A1 at up to 10 vol.% to meet selected properties: distillation temperature, flash point, density, net heating value, viscosity, freezing point, smoke point, and oxidation stability. From this study, it can be concluded that SBK is feasible for use as a drop-in aviation fuel when blended with conventional jet fuel. Thus, the SBK production is highly promising for use in tropical countries to produce aviation biofuels, given the appropriate technologies and feedstock resources. In order to reduce the emission of carbon dioxide, gas turbine power station will expect to use more clean fuels in the future, especially those like hydrogen. Hydrogen-rich fuel(syngas) combustion characteristics of the novel counter dual-swirl gas turbine combustor under fixed calorific value input were studied by experiment and numerical simulation. PIV and temperature rake were used respectively to obtain the velocity and temperature distribution in the combustion chamber. The turbulence model of Reynolds stress and the kinetic model of detailed chemical syngas combustion were used simultaneously in the computational simulations. Based on the obtained results, it was found that there is a reasonable agreement between the numerical results and the experimental data. The analysis shows that the flow field and temperature field of the combustor were almost unaffected by the change of hydrogen content and shows a nearly identical distribution structure under all conditions with hydrogen content below 90%; but when the H 2 content reaches 90%, the above characteristic plots were significantly changed. As the H 2 content in the fuel increases, on the center line of the combustor, the jet velocity of the fuel decreased, the temperature of the gas flow increased, the recovery coefficient of total pressure decreased, and the temperature distribution at the combustor outlet became more uniform. In addition, it is also found that the syngas turbine with the same output power consumed less fuel than the gas turbine with hydrocarbon fuel. This paper provides reference for the study of hydrogen-rich syngas turbine and the application of hydrogen-rich fuel in combustor of energy system. We present an approach for predicting the lower flammability limits of combustible gas in air. The influence of initial pressure and temperature on lower flammability limit has been examined in this study. The lower flammability limits of methane, ethylene and propane in air are estimated numerically at the pressure from one to 100 bar and the temperature from ambient to 1200 K. It was found that the predicted LFLs of methane, ethylene and propane decrease slightly with the elevated pressure at the high temperature. The LFLs variation for methane-air mixture is 0.17, 0.18, 0.18 volume% with the initial pressure from one to 100 bar at the initial temperature of 800 K, 1000 K and 1200 K respectively, which is significantly higher than that at lower temperature. And the LFL of methane-air mixture at 1200 K and 100 bar reaches 1.03 volume% which is much lower than that at 1 bar and ambient temperature. On the other hand, the LFLs variation is 0.11–0.12 volume% for ethylene-air mixture and 0.06–0.07 volume% for propane-air mixture with the initial temperature from 800 K to 1200 K at the same range of pressure. The LFL values at high temperatures and pressures represent higher risk of explosion.

: Lean flammability limits of alternative aviation fuels

Why is there an upper limit on flammability?

Upper flammability limit – Upper flammability limit (UFL): Highest concentration (percentage) of a gas or a vapor in air capable of producing a flash of fire in the presence of an ignition source (arc, flame, heat). Concentrations higher than UFL or UEL are “too rich” to burn.

Jack Gloop