Showing papers on "Autoignition temperature published in 1972"

Discrepancies and correlations of reported autoignition temperatures

Abstract: Why are significant discrepancies reported in the autoignition temperatures of materials, and which values should be used for fire protection purposes? These are questions to which the authors addressed themselves.

Research on Methods of Improving the Combustion Characteristics of Liquid Hydrocarbon Fuels. Volume I. Experimental Determination of Ignition Delay Times in Subsonic Flow Systems. Volume 2. Kinetics Modeling and Supersonic Testing

Abstract: : The purpose of this program was to determine, analytically and experimentally the extent to which the autoignition delay times of liquid hydrocarbons could be reduced by modification of the molecular structure or through the utilization of homogeneous additives and heterogeneous catalysts. To this end the autoignition delays of a number of different hydrocarbons were determined in three different experimental apparatus; a well-stirred reactor, a constant flow subsonic duct and a supersonic detached jet or ducted flow system. At one atmosphere pressure the velocity and temperature of the test devices were varied from subsonic to supersonic and from 300 to 1600 K respectively. No quantitative relationship could be established between the ignition lags measured in the constant flow system and the average residence times determined in the stirred reactor at the blow-out point. However, it is clear that the stirred reactor data more closely describe the total hydrocarbon combustion time than any 'pseudo ignition lag' associated with the hydrocarbon. Of the more than 25 different homogeneous additives tested, the strongest ignition promoters, by far, were found to be the alkyl nitrates and nitrites or nitric oxide and nitrogen dioxide. The presence of a platinum surface on the walls of the combustion chamber reduced the autoignition temperature of various hydrocarbons by 350 K. Fuel blends consisting of 15 volume percent n-propyl nitrate in either H-MCPD or Shelldyne-H were ignited and combusted in a piloted supersonic flow (Mach 1.5) over a temperature range of 300 to 1300 K.

Combustible mixture analyzer

Abstract: The sample of the gaseous fuel mixture to be analyzed is directed from the feed line leading to a combustion chamber and circulated through a flame arrestor and gas flow meter to a combustion mixture analyzer having an oxygen solid electrochemical cell contained therein. The fuel mixture is heated above its ignition temperature to obtain complete chemical equilibrium and the excess oxygen and/or fuel that remains, if any, mixed with the products of combustion circulate around the outer surface of the electrochemical cell. A suitable readout device measures the EMF produced across the electrodes of the cell when a gas of known partial pressure comes in contact with the inner surface of the electrochemical cell. The fraction of excess oxygen above that required for stoichiometric combustion that remains in the gaseous products of combustion is determined by the formula:

Research on methods of improving the combustion characteristics of liquid hydrocarbon fuels. Volume I. Experimental determination of ignition delay times in subsonic flow systems. Volume II. Kinetics modeling and supersonic testing. Final report 1 Jan 69--31 Dec 71

Abstract: The purpose of this program was to determine, analytically and experimentally the extent to which the autoignition delay times of liquid hydrocarbons could be reduced by modification of the molecular structure or through the utilization of homogeneous additives and heterogeneous catalysts To this end the autoignition delays of a number of different hydrocarbons were determined in three different experimental apparatus; a well-stirred reactor, a constant flow subsonic duct and a supersonic detached jet or ducted flow system At one atmosphere pressure the velocity and temperature of the test devices were varied from subsonic to supersonic and from 300 to 1600 K respectively No quantitative relationship could be established between the ignition lags measured in the constant flow system and the average residence times determined in the stirred reactor at the blow-out point However, it is clear that the stirred reactor data more closely describe the total hydrocarbon combustion time than any 'pseudo ignition lag' associated with the hydrocarbon Of the more than 25 different homogeneous additives tested, the strongest ignition promoters, by far, were found to be the alkyl nitrates and nitrites or nitric oxide and nitrogen dioxide The presence of a platinum surface on the walls of the combustionmore » chamber reduced the autoignition temperature of various hydrocarbons by 350 K Fuel blends consisting of 15 volume percent n-propyl nitrate in either H-MCPD or Shelldyne-H were ignited and combusted in a piloted supersonic flow (Mach 15) over a temperature range of 300 to 1300 K (GRA)« less

Method of, and apparatus for, heating of liquids

Abstract: A gaseaous combustible mixture, having a temperature lower than its ignition temperature, is passed with a speed exceeding its rate of flame propagation through a gas permeable layer of an radiation substance adapted to produce a thermal condition for radiating substantially the entire thermal energy, released at its surface, in the wave-length range of 0.5 - 6 micrometers within the active substance layer on. The apparatus comprises a reaction space filled with said substance and a supply system for the combustible mixture.

Electric ignition system

Abstract: The present fuel control and ignition system senses both the temperature of an electric igniter and flame at a burner. When the system senses that the igniter has reached ignition temperature, the main fuel valve is opened and the igniter deenergized. If ignition occurs, then the main fuel valve will be held open and the igniter deenergized until there is no more demand for heat, when the fuel valve will be closed. However, if ignition does not occur or if power is lost after a flame has been established at the burner, then the main fuel valve will be closed and the ignition sequence will be automatically restarted.

The Effects of Additives on High Speed Ignition and Combustion Characteristics of Storable Fuels

Abstract: : The report describes studies performed on mixing, ignition and combustion of high density fuels. Ignition and combustion augmentation of slurries using magnesium and lithium fluoride, respectively, is included. Experiments were conducted in a direct connect constant area combustor supplied by Mach 2 airstream at a pressure level of about 1 atmosphere covering a stagnation airstream temperature range from about 600 to 1600K. The results indicate that the autoignition limit for the lithium impregnated boron slurry appears to be about 1500K. It was found that within the piloting regime the boron slurry with and without the lithium fluoride involves four characteristic zones: no ignition, initial flame, staged burning, and propagating flame zone. These studies substantiate that the lithium fluoride mechanism of combustion enhancement involves chemical removal of the boron oxide barrier, rather than having a direct thermal effect. (Modified author abstract)

Superheating in the Zirconium-Oxygen Combustion System

Abstract: WHEN a clean metal surface is exposed to the attack of a gas such as oxygen in low temperature conditions, reaction begins at the gas-metal interface, so that if the reaction products are nonvolatile an intermediate layer between the gas and metal will be formed. If, however, the rate at which the oxidation occurs is sufficiently high and the amount of energy supplied by the oxidation is sufficiently large, the oxidation mode, in most cases, changes into a different sustained rapid combustion mode. This initial rapid rise in temperature of the metal is called an “autoignition” period when it is followed by a sustained period of rapid combustion.