Showing papers on "Spontaneous combustion published in 1982"

A Study of the Relationships between Cycle-to-cycle Variations of Combustion and Heat Release Delay in a Spark Ignited Engine

Abstract: To clarify the cause of cycle-to-cycle variations of combustion in a spark ignited engine, two types of combustion, conventional and fast burn (2-plug ignition), and two types of fuel, gasoline and propane, were tested and analyzed by measuring the cylinder pressure. An electronic computer was utilized for these analyses. From these analyses, it was established that cycle -to-cycle variations of combustion in a spark ignited engine were dependent on cycle-to-cycle variation of the air-fuel ratio of the mixture ; and that the shorter the heat release delay between ignition and start of heat release, the lower the cycle-to cycle variations of combustion.

Self-ignition of gas in front of the flame front in a closed vessel

Abstract: The peculiarities of the appearance of thermal self-ignition in front of the flame front in the combustion of a homogenous gas mixture in a closed vessel is studied. The possibility of self-ignition is determined by whether the combustion of the mixture or bulk combustion occur first. The system of equations is included. The self-ignition conditions, the relation between the process parameters, and the basic criterion are studied. Special problems such as the expansion of gas during self-ignition are considered. Finally, the scale factor of self-ignition is considered in light of the tendency to increase the size of technology apparatus of late. The phenomenon of ''knock'' in motors with spark ignition is a practical analog with a solution suggested.

Stabilization of coal

Abstract: PURPOSE: To reduce the activity of a low-grade coal and prevent its spontaneous ignition, by heating the coal to a specified temperature to reduce the water content and then subjecting it to an oxidation treatment. CONSTITUTION: Coal, mainly low-grade coal such as peat, brown coal or sub- bituminous coal, is heated at 100W350°C until its water content is reduced substantially to 0% and is then subjected to an oxidation treatment. For example, the water content of the coal is lowered to 15W20wt% by drying in the sun, etc. and the oxidation treatment is performed for 10minW3hr in an inert gas such as nitrogen gas. When necessary, the coal after the heat treatment is formed into shape under heat and pressure and is oxidized at 10W200°C for 30minW5hr with oxygen in the concentration of 1W21vol.%. The method produces coal for fuel with excellent resistance to spontaneous ignition and a high calorific value. COPYRIGHT: (C)1984,JPO&Japio

Experimental study on gas-phase ignition of cellulose under thermal radiation

Abstract: This study aimed to clarify the mechanism of gas phase ignition of a solid. Small cellulosebricks were irradiated by an Xe-lamp, and the time and space variation of the temperature and fuel gas concentration in the gas phase were examined precisely during ignition by means of a Mach-Zehnder interferometer and a specially designed gas sampler. Small amounts of hydrocarbons were detected at the time close to ignition. CO and CO2were the dominant species in the gas phasepyrolysis products, and they appeared a short time after the start of irradiation. The ignition was considered to be controlled by the gas phase reaction of these minor species. The ignition point where the flame kernel first appeared was identified, and the transitionfrom ignition to quasi-steady flame was followed by means of a Schlieren system.

Loading coal in open hopper barges

Abstract: Problems of spontaneous combustion and acid corrosion in coal carrying open hopper steel barges are significantly reduced by loading a mixture of coal of various particle sizes in the hopper without segregating and isolating groups of particles of different sizes. This reduces the air circulation paths through the loaded coal and prevents the supply of oxygen necessary for feeding both spontaneous combustion and acid corrosion. A preferred embodiment of the invention comprises spreader-deflector means between a chute and the barge hopper floor that distributes the coal particle mixture in a substantially flat loading pattern that eliminates prior art conical patterns tending to create an air flow chimney effect encouraging spontaneous combustion and acid corrosion.

Experimental Study on Suppression of Detonation Waves

Abstract: In this experiment, detonation waves propagating in a stoichiometric propane-oxygen mixture through a channel containing an obstruction were investigated in order to clarify the cellular structure of the waves and also to find some methods for suppressing the detonation. The results suggest that triple shocks are formed by isochoric combustion accompanying spontaneous ignition behind the shock waves at the detonation front and that the propagation velocity must be decelerated to suppress the detonation, to the extent of keeping the temperature or the mixture so low that no spontaneous ignition takes place.

Fire and explosion properties of oil shale

Abstract: This is a progress report summarizing more than 5 years of a long-range Bureau of Mines research program. The purpose of this program has been to investigate the fire and explosion properties of Green River oil shale in the Bureau's Experimental Mine, in laboratories, and in the field. The lean limits of explosibility of oil shale dust, by small- and large-scale tests, are reported as a function of grade, ignition source, and particle size. A limited number of laboratory tests on the autoignition of oil shale dust layers and the spontaneous combustion tendencies of oil shale are described. Moderate-scale rubble fire tests were conducted to determine flame spread rates as a function of ventilation flow. With the aid of a system to continuously monitor methane emissions in a deep oil shale mine, the characteristics of the methane flow are reported as a function of ventilation and blasting procedures, and are compared with gas yields from core samples. Tentative predictions as to the emission of the methane to be expected in deep oil shale mines, far from the outcrop, are offered. Brief reference is made to a parallel investigation into the fire and explosion hazards of oil shale mining and processingmore » by a Bureau contractor; detailed results of the latter investigation are to be found in the contractor's reports. 43 figures.« less

High load combustion method

Abstract: PURPOSE:To enable to burn materials difficult for atomization combustion at high temperature and load by a method wherein feed materials are hels to the front part of a combustion chamber with strong swirling flame in a cylindrical furnace in which materials of higher viscosity or lower heating power are to be burnt CONSTITUTION:In order to burn the fuel producing metal or the like as combustion residue, at first the combustion furnace 1 is preheated by means of an auxiliary burner 6 up to the temperature for spontaneous combustion of the fuel and then the combustion air is spouted from a nozzle 3 and simultaneously the fuel is flowed down from a fuel feed nozzle 2 installed at the center of the side surface upstream of the furnace The tangential flow speed of the combustion air is rendered to be no less than 60m/sec and the angle between the flow line and the generating line of the cylinder is rendered to be 45-75 deg Under the condition given to the combustion air as mentioned above, the swirling flame presses the fuel to the front part of the comsution chamber, preventing the fuel from flowing out to the downstream side of the furnace The solid or particulate fuel falls down by means of a quantitative feeder The fuel with no spontaneous combustion property is burnt with the continuous use of the auxiliary burner

Dynamic effects of combustion

Abstract: The dynamic effects of combustion are due to the evolution of exothermic energy and its deposition in the compressible medium where the process takes place. The paper examines the dynamics of combustion phenomena, including ignition, turbulent flame propagation (inflammation), explosion, and detonation, with emphasis on their exothermic characteristics. Ignition and explosion are treated as problems of nonlinear mechanics, and their dynamic behavior is described in terms of phase space models and cinematographic laser shear interferograms. The results of a numerical random vortex model of turbulent flame propagation are confirmed in a combustion tunnel experiment, where it was observed that a fresh mixture of burnt and unburnt gases can sustain combustion with a relatively small expenditure of overall mass flow, due to the increasing specific volume of burnt gases inside the flame front. An isentropic pressure wave is found to precede the accelerating flame in the process of detonation, and components of this presssure wave are shown to propagate at local sonic velocities.

The spontaneous heating properties of coals

Abstract: The spontaneous heating properties of 41 sample coals at a temperature range of about 20 - 200 degrees C, were studied using a spontaneous ignition tester which was commercially available. It was concluded that:-- The temperature increase rate of coal by oxidation, that is, the exothermic rate by oxidation, is described using Arrhenius' kinetic equation. This rate increases rapidly above 120 degrees C. The frequency factor increases as a 0.4 to 0.7 power of oxygen concentration in the atmosphere, while it decreases as a -0.4 to -0.6 power of the coal particle diameter at temperatures below 120 degrees C, and as a -1 power of the coal particle diameter at temperatures above 120 degrees C. The larger the O/C or the larger the amount of volatile matter, the higher the spontaneous ignition properties of the coal become.

Critical conditions of the propagation of combustion with source ignition of gas-free systems

Abstract: The aim of this work is a numerical investigation of the process of high-temperature ignition of an infinite gas-free condensed homogeneous system by an inert hot plate and the process by which combustion passes beyond the limits of the igniting plane. No account is taken of phase transitions and the various thermophysical characteristics of the initial material and the combustion products. The reaction of thermal decomposition of the initial gas-free system is assumed to be a first-order reaction. The process of ignition and propagation of combustion beyond the limits of the ignition source is described by a system of differential equations of thermal conductivity and chemical kinetics. Concludes that taking the stage of heat-source ignition into account does not have a very strong influence on the critical conditions for transition to combustion conditions. Indicates that after somewhat modifying the Zel'dovich qualitative principle of thermal initiation of the combustion of gas by a spark, it may also be used in the case of source initiation of the combustion of gas-free systems.