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. 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. Pdf robert bruce energy work, the secrets of healing. The energy of a break spark is given by eb 12 li2 15 where l is inductance henries and i is the current amperes. Hydrogen detonations, although rare, are characterized by. This means that there is a need for methods that permit differentiation when. 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. Ignition temperature is an important property of any fuel because the combustion reaction of the fuel becomes selfsustaining only above it. 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. The ignition energies given by magison and those obtained in the present work are considerably.
The materials used are, gases methane, propane and hydrogen and dust starch, lycopodium, toner, wood and cn4 mixture of bituminous and. Some attempts were done to correlate the aits of pure hydrocarbons with the average carbon chain length 2. Every different fuel air mixture will have different minimum ignition energies. Previous investigations of ignition energy utilized various tech niques, such as heat. The parameter of most significance for prediction of ignition is the spark energy. Take the above precautions and restrict use of insulating materials. Although hydrogenair mixtures have the same calorific value per pound as tnt, the rate of energy release is much slower for hydrogenair mixtures. The minimum ignition energy for hydrogenair mixtures is at nearstoichiometric conditions, i. It does not have good ozone, oxygen or sunlight resistance without the addition of special additives. 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 technical literature lists different types of possible ignition sources. Mie of a flammable dust is the minimum spark energy needed to ignite an ideal concentration under lab conditions.
Rather, the reactant energy and the product energy remain the same and only the activation energy is altered lowered. This means that the minimum energy is increased as the inverse of the laminar flame speed, cubed. Minimum ignition energy and ignition probability for methane. The spark ignition system consisted of 3mm diameter metal rod electrodes with a durable plastic spacer for rigidity. Minimum ignition energy the minimum amount of energy supplied that is needed for combustion is the minimum ignition energy.
The important effect of energy input radius on minimum ignition energy is discussed in some detail for a propaneair mixture. Discharges from humans generally need to be greater than the fuels minimum ignition energy to be an ignition source. 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. For a fire or deflagration to occur, three things must be present. Increased pressures can also reduce the auto ignition temperature. Statistical analysis of spark ignition of keroseneair mixtures. Nitrile has poor resistance to ketones, chlorinated hydrocarbons, and nitro hydrocarbons. Increasing the oxygen levels andor the pressure can increase the minimum ignition energy. Rifet sloan automotive laboratory the energy laboratory massachusetts institute of technology january 1980. Minimum ignition of six pure hydrocarbon fuels of the c2 and c6. In comparison, a small coin dropped from a height of less than 1 mm has. The minimum ignition energy of jet a was found to vary between 100 j for a fuelair temperature of 25 cto40mjat55 c. A catalyst is able to reduce the activation energy by forming a transition state in a more favorable manner.
Comparison of minimum ignition energy for four alkanes. In other words, heavier hydrocarbons tend to autoignite before lighter hydrocarbons. Prediction of autoignition temperatures and delays for gas. The position of the minimum of the parabola depends upon. 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. Today in part 1 we will introduce important concepts in hydrocarbon gas flammability. In this work, two quantitative structureproperty relationship qspr models were built based on existing.
However, it is extremely difficult to obtain experimental mie data due to the high cost, time involved, and safety issues of experimental tests. All flammables including dusts have minimum ignition energies. Statistical analysis of spark ignition of keroseneair. Lmie lowest minimum ignition energy measured al optimum concentration ig in eq. Flammable refrigerant odorant study may be funded by the consumer products safety commission instead of ashrae. Depending on the specific application, there are several standard procedures for determining mie of dust clouds, solvent vapours and gases. Finding minimum structures on the seam of crossing in. Catalysts, by nature, create a more comfortable fit for the substrate of a reaction to progress to a transition state. Investigation of hot surface ignition temperature for a2l refrigerants nfpa. The mie is the minimum energy of an ignition source, such as a spark, required to ignite the vapor. Part 2 technical aspects of flammability and ignition 2. Ignition temperature an overview sciencedirect topics. Ignition by adiabatic compression and shock waves 401 e. The new standard on avoidance of electrostatic hazards.
Experimental tests have generally demonstrated that saturated hydrocarbon vapors. 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. In this connection, it is extremely important to assess electrostatic charges properly with regard to incendivity. Experimental investigation of spark ignition energy in. Measurements of minimum ignition energy by using laser. Ignition energy depends on the relative concentrations of fuel and oxygen present in the mixture. 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.
Prabir basu, in biomass gasification and pyrolysis, 2010. The flammability hazard of a substance is also increased by. The focus of attention on the root cause of the variations has been in. Despite these previous studies, we still lack a comprehensive database of ignition energy data for use in. Ignition sources the information on this section of the site looks at the many possible ignition sources. Minimum energy for ignition an overview sciencedirect. Hydrocarbon fuels and their properties university of calgary. The flash point of a substance is often treated as the principal index of flammability, especially for liquids.
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. Basics of flammability flash and fire points the flash point is the minimum temperature. Minimum ignition energy mj x, where the artificialforceinduced reaction afir method is combined with the seam model function smf approach. However, at the lean flammability limit, the ignition energy. T1 measurements of minimum ignition energy by using laser sparks for hydrocarbon fuels in air.
Spontaneous ignition of pressurized releases of hydrogen and. For any given vapor air mixture, there is a minimum spark ignition energy. Robert bruce energy work, the secrets of healing and spiritual growth x robert bruce. 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. Predicts the ease and likelihood of ignition of a dispersed dust cloud.
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. For a cylinder 10 cm in diameter, the time required for a pressure disturbance. Minimum auto ignition temperature ait of fuels at standard temperature and pressure in the literature k fuel reference publication 1 2 3 4. General risk assessment with all flammable refrigerants, the risk arises with. When an external ignition source with sufficient energy to ignite the fueloxygen. Pdf determination of the minimum ignition energy on different. 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. Minimum energy for ignition an overview sciencedirect topics. Ignition hazards caused by electrostatic charges in. Irp18 website copy final june 14 sue ignition sources. 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.
This is accomplished by following the gas velocity limitations set forth in cga pamphlet g4. 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. Apr 27, 2007 the important effect of energy input radius on minimum ignition energy is discussed in some detail for a propaneair mixture. 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.
Despite these previous studies, we still lack a comprehensive database of ignition energy data for use in safety engineering and assessment. Carbon steel pipelines in oxygen service must be designed and operated to minimize the potential hazard. Depending on the specific application, there are several standard procedures for determining mie of. Unlike many other sources of ignition, electrostatic dis. A glossary of some of the terms used in this guide is provided at the end of the document. Hydrocarbon gas flammability part 1 of 3 in a series on. 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. General properties of elastomers elbex corporation. New refrigerants designation and safety classifications. Some gases have even lower minimum energies for ignition as indicated in. 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. The minimum ignition energies for six hydrocarbon fuels are reported herein.
The torch igniter for the liquid fuel worked in a satisfying way. Pdf minimum ignition energies of hydrogenair and methaneair mixtures have been investigated numerically by solving unsteady. Increased pressures can also reduce the autoignition temperature. Working with modern hydrocarbon and oxygenated solvents.
The minimum ignition energy of jeta fuel commercial jet fuel shows a nearly parabolic variation upon stoichiometric ratio of the mixture. Electrical sparks are the result of a discharge of energy through a gap. Spontaneous ignition of pressurized releases of hydrogen. The mie depends on the specific chemical or mixture, the concentration, pressure, and temperature. Many of the characteristics of hydrocarbon and oxygenated solvents can be understood from the general overview provided in this guide. The common element in all procedures is that the energy is generated by an. This is because conditions such as temperature, humidity and surface shape all affect the energy of the discharge.
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