However, at the lean flammability limit, the ignition energy. Lmie lowest minimum ignition energy measured al optimum concentration ig in eq. The torch igniter for the liquid fuel worked in a satisfying way. Minimum ignition energy and ignition probability for methane. Minimum ignition energy mie is one of the most important and most widely used parameters when characterizing hazardous chemicals. Statistical analysis of spark ignition of keroseneair. The spark ignition system consisted of 3mm diameter metal rod electrodes with a durable plastic spacer for rigidity. Depending on the specific application, there are several standard procedures for determining mie of dust clouds, solvent vapours and gases. Comparison of minimum ignition energy for four alkanes. Ignition energy depends on the relative concentrations of fuel and oxygen present in the mixture. This is because conditions such as temperature, humidity and surface shape all affect the energy of the discharge.
General risk assessment with all flammable refrigerants, the risk arises with. Basics of flammability flash and fire points the flash point is the minimum temperature. The minimum ignition energy of jet a was found to vary between 100 j for a fuelair temperature of 25 c and 40 mj for a fuelair temperatue of 55 c 7. Every different fuel air mixture will have different minimum ignition energies. Ignition sources the information on this section of the site looks at the many possible ignition sources. The focus of attention on the root cause of the variations has been in. The flammability hazard of a substance is also increased by.
Minimum ignition energy mj of table 2 shows that the data obtained with inductance sparks agrees reasonably well with that of magison, but the measured ignition energy was higher with the capacitance spark. The position of the minimum of the parabola depends upon. The minimum ignition energy of jeta fuel commercial jet fuel shows a nearly parabolic variation upon stoichiometric ratio of the mixture. It refers to the smallest amount of energy that an electric spark discharge must have to cause an ignition of a given gas mixture at given conditions. Ignition quality is arguably the most important fuel property from a combustion standpoint metrics cetane number cn research motor octane number ron mon sensitivity s ron mon flammability limits flame speed tolerance to egr minimum ignition energy 5 ignition quality. Prediction of autoignition temperatures and delays for gas. In a typical gasifier, a certain amount of combustion is necessary to provide the energy required for drying and pyrolysis and finally for the endothermic gasification reaction. Statistical analysis of spark ignition of keroseneair mixtures. Rather, the reactant energy and the product energy remain the same and only the activation energy is altered lowered. All flammables including dusts have minimum ignition energies. Finding minimum structures on the seam of crossing in. Flammable refrigerant odorant study may be funded by the consumer products safety commission instead of ashrae. Ignition tests are performed with varying spark energies and a range of fuel temperatures. The new standard on avoidance of electrostatic hazards.
Hydrocarbon gas flammability part 1 of 3 in a series on. For a cylinder 10 cm in diameter, the time required for a pressure disturbance. This is accomplished by following the gas velocity limitations set forth in cga pamphlet g4. It does not have good ozone, oxygen or sunlight resistance without the addition of special additives. The parameter of most significance for prediction of ignition is the spark energy. In this connection, it is extremely important to assess electrostatic charges properly with regard to incendivity. The energy of a break spark is given by eb 12 li2 15 where l is inductance henries and i is the current amperes. Take the above precautions and restrict use of insulating materials. The materials used are, gases methane, propane and hydrogen and dust starch, lycopodium, toner, wood and cn4 mixture of bituminous and.
Ignition energy minimum for ignition in air 0,017 mj autoignition temperature, 858k flame temperature in air, 2318k the principle hazard presented by the gasification and posterior separation process described for hydrogen production is the uncontrolled combustion of accidentally released hydrogen. Minimum energy for ignition an overview sciencedirect. Despite these previous studies, we still lack a comprehensive database of ignition energy data for use in safety engineering and assessment. The lower explosive limit for dust concentrations is 50 gramsm3, which is more than 10,000 times the commonly cited occupational exposure limit of 3. Predicts the ease and likelihood of ignition of a dispersed dust cloud. Minimum ignition energy mj x, where the artificialforceinduced reaction afir method is combined with the seam model function smf approach. Today in part 1 we will introduce important concepts in hydrocarbon gas flammability. Electrical sparks are the result of a discharge of energy through a gap. However, it is extremely difficult to obtain experimental mie data due to the high cost, time involved, and safety issues of experimental tests. This means that the minimum energy is increased as the inverse of the laminar flame speed, cubed. Hydrocarbon fuels and their properties university of calgary. Pdf numerical calculation of minimum ignition energy for.
Auto ignition temperature ignitability and minimum ignition energy mie static electricity 5 chemistry and physics of fire for a fire to start, 3 elements must combine. For any given vapor air mixture, there is a minimum spark ignition energy. Ignition temperature an overview sciencedirect topics. Rifet sloan automotive laboratory the energy laboratory massachusetts institute of technology january 1980. A glossary of some of the terms used in this guide is provided at the end of the document. Pdf robert bruce energy work, the secrets of healing. In other words, heavier hydrocarbons tend to autoignite before lighter hydrocarbons. This means that there is a need for methods that permit differentiation when. The determination of minimum ignition energy curves for fuelair mixtures have been problematical with widely varying results for different groups using different fuels, fuel treatment regimes and ignition sources. Discharges from humans generally need to be greater than the fuels minimum ignition energy to be an ignition source. Finally, the disparity in minimum ignition energy between hydrogen and gaseous hydrocarbons may not be as significant in terms of hazard issues as it might appear. In chemistry and physics, activation energy is the energy which must be provided to a chemical or nuclear system with potential reactants to result in. Its application to reactions between triplet dioxygen and unsaturated hydrocarbons provided many msx structures. The technical literature lists different types of possible ignition sources.
Pdf minimum ignition energies of hydrogenair and methaneair mixtures have been investigated numerically by solving unsteady. Experimental investigation of spark ignition energy in. In previous work on spark ignition 10,11 a single threshold minimum ignition energy was not observed, but rather the ignition was found to be probabilistic in nature at low spark energies. Investigation of hot surface ignition temperature for a2l refrigerants nfpa. Many of the characteristics of hydrocarbon and oxygenated solvents can be understood from the general overview provided in this guide. Robert bruce energy work, the secrets of healing and spiritual growth x robert bruce. Some attempts were done to correlate the aits of pure hydrocarbons with the average carbon chain length 2.
Unlike many other sources of ignition, electrostatic dis. For a fire or deflagration to occur, three things must be present. The minimum ignition energy of jet a was found to vary between 100 j for a fuelair temperature of 25 cto40mjat55 c. Minimum auto ignition temperature ait of fuels at standard temperature and pressure in the literature k fuel reference publication 1 2 3 4. In this work, two quantitative structureproperty relationship qspr models were built based on existing. Apr 27, 2007 the important effect of energy input radius on minimum ignition energy is discussed in some detail for a propaneair mixture.
Carbon steel pipelines in oxygen service must be designed and operated to minimize the potential hazard. After establishing a methodology for finding the minimum ignition energy for a specific fuel and equivalence ratio, results are presented for methane through butane over a wide range of equivalence ratios. Some gases have even lower minimum energies for ignition as indicated in. Depending on the specific application, there are several standard procedures for determining mie of. Although hydrogenair mixtures have the same calorific value per pound as tnt, the rate of energy release is much slower for hydrogenair mixtures. Ignition hazards caused by electrostatic charges in. Measurements of minimum ignition energy by using laser. Hydrogen detonations, although rare, are characterized by. Experimental tests have generally demonstrated that saturated hydrocarbon vapors.
The mie depends on the specific chemical or mixture, the concentration, pressure, and temperature. T1 measurements of minimum ignition energy by using laser sparks for hydrocarbon fuels in air. Prediction of minimum ignition energy from molecular. Spontaneous ignition of pressurized releases of hydrogen. Increasing the oxygen levels andor the pressure can increase the minimum ignition energy. General properties of elastomers elbex corporation.
Despite these previous studies, we still lack a comprehensive database of ignition energy data for use in. Minimum ignition energy the minimum amount of energy supplied that is needed for combustion is the minimum ignition energy. Part 2 technical aspects of flammability and ignition 2. Ignition by adiabatic compression and shock waves 401 e. The minimum ignition energy for hydrogenair mixtures is at nearstoichiometric conditions, i. A catalyst is able to reduce the activation energy by forming a transition state in a more favorable manner. However, the burning of these hydrocarbon fuels causes the emission of greenhouse gases and other pollutants. Nitrile has poor resistance to ketones, chlorinated hydrocarbons, and nitro hydrocarbons. Mie of a flammable dust is the minimum spark energy needed to ignite an ideal concentration under lab conditions. When an external ignition source with sufficient energy to ignite the fueloxygen. New refrigerants designation and safety classifications.
Working with modern hydrocarbon and oxygenated solvents. Previous investigations of ignition energy utilized various tech niques, such as heat. The most efficient burning occurs when the fuel and oxygen are near the stoichiometric mixture and this also approximately corresponds to the minimum ignition energy mie. The minimum ignition energies for six hydrocarbon fuels are reported herein. Minimum energy for ignition an overview sciencedirect topics. Increased pressures can also reduce the autoignition temperature.
Pdf determination of the minimum ignition energy on different. Hydrocarbon formation and oxidation in spark ignition engines final report on a research program funded by general motors research laboratories september 1976 to august 1979 volume i. In comparison, a small coin dropped from a height of less than 1 mm has. A3 risk assessment and ignition severity study ashrae1794. Auto ignition temperature ignitability and minimum ignition energy mie static electricity 5 chemistry and physics of fire. Minimum ignition energy mie values by the break spark method can be nearly of the order of mies associated with the capacitance spark method if very fine wires and rapid separations are used. Ignition temperature is an important property of any fuel because the combustion reaction of the fuel becomes selfsustaining only above it. The flash point of a substance is often treated as the principal index of flammability, especially for liquids.
The common element in all procedures is that the energy is generated by an. Catalysts, by nature, create a more comfortable fit for the substrate of a reaction to progress to a transition state. Spontaneous ignition of pressurized releases of hydrogen and. It can be shown that the minimum energy for ignition, based on supplying sufficient energy to the volume of mixture in the vicinity of the sparkgap to cause a stable flame, is q p, min. Minimum ignition of six pure hydrocarbon fuels of the c2 and c6. Prabir basu, in biomass gasification and pyrolysis, 2010. Irp18 website copy final june 14 sue ignition sources. The mie is the minimum energy of an ignition source, such as a spark, required to ignite the vapor. By limiting the velocity, the particle impact energy is reduced, which minimizes the chance of an ignition. Increased pressures can also reduce the auto ignition temperature. The ignition energies given by magison and those obtained in the present work are considerably. Critical ignition parameters, eg, the minimum ignition temperature and the minimum ignition energy, of a given explosive gas mixture can vary substantially with the actual ignition source characteristics, and the dynamics, pressure, and temperature of the gas mixture. The important effect of energy input radius on minimum ignition energy is discussed in some detail for a propaneair mixture.
1302 113 1322 1019 917 1295 272 653 266 1413 929 429 1261 1382 106 1480 1504 1559 104 1349 276 694 45 1345 474 1084 1357 269 924 833 734 1111 456