Showing papers on "Spontaneous combustion published in 1986"

Thermal ignition combustion system

Abstract: The thermal ignition combustion system comprises means for providing walls defining an ignition chamber, the walls being made of a material having a thermal conductivity greater than 20 W/m° C. and a specific heat greater than 480 J/kg° C. with the ignition chamber being in constant communication with the main combustion chamber, means for maintaining the temperature of the walls above a threshold temperature capable of causing ignition of a fuel, and means for conducting fuel to the ignition chamber.

Device for inhibiting NOx formation by a combustion system

Abstract: A device is disclosed for use in a combustion system to inhibit formation of oxides of nitrogen (NOx) by the combustion system thereby reducing NOx emissions from the combustion system. The device is made of a material, such as stainless steel, which is positioned at the periphery of a combustion flame produced by a burner which is part of the combustion system, to temper the combustion flame by absorbing thermal energy from the combustion flame. The device sufficiently tempers the combustion flame to limit peak combustion flame temperatures and residence times at these peak combustion flame temperatures to levels which inhibit formation of oxides of nitrogen while allowing substantially complete combustion of the fuel supplied to the burner.

Spontaneous combustion of coal

Abstract: A study of spontaneous combustion which involves mine fires as well as safety in the utilization of coal has led Cerchar to develop, new tests on a scale of several hundred kilograms and their mathematical modelling. The space-time rise of the temperatures at the core of the coal can be compared with the results of the model and its parameters can be adjusted progressively until its predictions approach the real facts. The model in turn makes it possible, based on the relations between the transfers of heat and of matter and the aerodynamics of gas flow, to get to know the action of the different parameters and variables and to establish an order of rank of their effects on the phenomenon of oxidation and of self-heating. The results obtained with different grades of coal in experimental bunkers of 3.5 and 5.5 m/sup 3/ are in fact of direct use for safety problems in the utilization of coal in pulverized form. The tests in tanks with a controlled heat loss which make it possible to take into account factors like the grain size, humidity and heterogeneity of the coal will be of more direct usefulness for anticipating the risk of self-heating of a solid fuel of the run-of-mine grade during transport or storage.

Deactivation of dried subbituminous coal

Abstract: Deep drying of inherent moisture from subbituminous coal produces a dried product which is friable and very reactive to oxygen in air. The major problems in handling dried coal, which are unique to deep drying of low-rank coal, are: (1) avoidance of spontaneous combustion, (2) prevention of moisture reabsorption, and (3) control of dust. Atlantic Richfield has developed, and successfully demonstrated, technologies which solve all three problems. However, this paper will be confined to the spontaneous combustion problem Low-temperature ‘oxidation may result in spontaneous combustion’ of the coal during storage or transit. The increased reactivity to low-temperature oxidation of dried coal is due to two factors: (1) the reduction in moisture content, and (2) the increase in temperature. A laboratory technique was developed to measure the coal reactivity to low-temperature oxidation at temperatures near ambient. Laboratory data was then used to develop a pseudo-first order kinetics model for dried subbitumin...

Influence of Pressure on Autoignition Characteristics of Gaseous Hydrocarbon-Air Mixtures

Abstract: The influence of pressure on the auto ignition characteristics of homogeneous mixtures of hydrocarbon fuels in air is examined. Auto ignition delay times are measured for propane, ethylene, methane, and acetylene in a continuous flow apparatus featuring a multi-point fuel injector. Results are presented for mixture temperatures from 670K to 1020K, pressures from 1 to 10 atmospheres, equivalence ratios from 0.2 to 0.7, and velocities from 5 to 30 m/s. Delay time is related to pressure, temperature, and fuel concentration by global reaction theory. The results show variations in global activation energy from 25 to 38 kcal/kg-mol, pressure exponents from 0.66 to 1.21, and fuel concentration exponents from 0.19 to 0.75 for the fuels studied. These results are generally in good agreement with previous studies carried out under similar conditions.

Criterion for Spontaneous Ignition of Radiantly Heated Organic Solids

Abstract: In analytical studies of radiant ignition of organic solids, one of the important tasks is to quantitatively describe what ignition is. Experimentally, ignition is signalled by the inception of a flame or of an abrupt change in such crucial gas property as temperature. Some ignition criteria which evolved from experimental observations and intuition are the attainment of a critical: (i) temperature of the exposed surface; (ii) pyrolyzate efflux rate; (iii) char depth in the pyrolyzing slab; (iv) rate of local gas temperature in the boundary layer; and (vii) gas temperature gradient at the solid-gas interface. In this paper, a one-dimensional mathematical model is presented for the radiantly induced spontaneous ignition of solids to examine the issue of ignition criterion. The model takes into account the transient heat conduction within the heated solid, consequent pyrolysis, and exothermic oxidation reactions in the developing natural convective boundary layer in the gas-phase. The results show ...

Hydrogen Combustion Study in Direct Infection Hot Surface Ignition Engine

Abstract: The hydrogen combustion characteristics have been studied in a late-injection (near TDC) hot surface ignition engine. As a supplemental experiment, the mode of combustion was observed in a constant volume combustion chamber by the schlieren method. Consequently the combustion process, that was the flame propagation initiated by a hot surface through heterogeneous hydrogen jets, was not the same as that of a diesel engine. The experimental results in test engine showed the optimum number of injection holes and the effect of intake air swirl for better mixture formation.

Swirl chamber arrangement for diesel engine or the like

Abstract: In a pre-chamber type diesel engine, in order to prevent droplets of liquid fuel finding their way into zones of the main combustion chamber (108) wherein they undergo slow combustion and thus tend to form smoke, a recess (120) is formed at the main combustion chamber end of an auxiliary transfer passage (114) in a manner to provide a wall section (122) which deflects droplets of fuel, which have passed through the auxiliary passage during the induction phase and/or initial stage of the compression phase, in a manner that they do not escape toward the perimeter of the piston crown and remain in a zone through which the flame produced by spontaneous combustion of the highly compressed airfuel mixture in the pre-chamber (112) passes thus ensuring rapid vaporization and subsequent oxidation.

Effect of Pressure on Polymer Ignition

Abstract: Auto-ignition temperature of polystyrene, poly(vinyl chloride) and carboxy terminated polybutadiene has been measured at various oxygen pressures (1-28 atm) in a high pressure differential thermal analysis assembly at a heating rate of 10°C/min. The exothermic peak appears between 250-350°C in polystyrene and poly(vinyl chloride) and between 150-200°C for carboxy terminated polybutadiene. Ignition appears to be controlled by in situ forma tion and degradation of polymeric peroxides. Inverse dependence of ignition temperature on oxygen pressure is explained by the rate equation which con siders that ignition of a particular sample, of a fixed geometry, occurs when gasification rate reaches a unique critical value.

Characterization of Western Canadian coals with respect to their susceptibility to spontaneous combustion

Abstract: The problem of spontaneous combustion of coal has long been a concern of the mining, storage and transportation sectors of the industry. This paper reviews a project which examines susceptibility of coals to spontaneous combustion. Common testing methods were used including: determination of initial temperature; differential thermal analysis; and, determination of crossing point temperature. Results included information on tests conducted for a number of Western Canadian coals. 5 refs., 14 figs., 4 tabs.

The Autoignition and Combustion of Coal-Water Slurry Under Simulated Diesel Engine Conditions

Abstract: The combustion characteristics of a coal-water slurry spray were examined under diesel engine conditions. A two-stage combustion process was used to simulate the diesel engine conditions in a constant-volume combustion bomb. The combustion characteristics investigated were ignition delay, ignition site, combustion development, combustion duration, and combustion completeness. The results show that the ignition delay of the coal-water slurry fuel is temperature and pressure dependent. Also, the coal slurry ignition delay is approximately a factor of five longer and the energy release rate is significantly slower in comparison to the ignition delay and energy release rate for conventional No. 2 diesel fuel.

Discharge gas treating device

Abstract: PURPOSE: To prevent solid fine particles generated by combustion from sticking to pipe wall, etc., by providing a connecting liquid-streaming part of washing liquid to the inner wall of a gas introducing pipe introducing a discharge gas containing a spontaneous ignition toxic gas to a combustion chamber. CONSTITUTION: A double pipe structure 7 is provided with numerous spouting openings to an area of a certain length (l) from the open end 5a of the discharge gas introducing pipe 5 which introduces a gas containing a spontaneous ignition toxic gas, such as silane gas, discharged from a semiconductor manufacturing process to a shower washing chamber 8 used also as a combustion chamber. SiH 4 , etc., are spontaneously ignited by bringing into contact with air, and fine particles of SiO 2 , etc., produced by combustion are always washed out by a washing liquid, such as an alkaline aqueous solution, along all the inner peripheral surface of the introducing pipe 5, and, as a result, the clogging of the open end 5a is surely prevented. COPYRIGHT: (C)1988,JPO&Japio

Upgrading and storage of solid carbonaceous fuel

Abstract: Solid carbonaceous fuel is dried to a desired moisture content, cooled, and stored in an atmosphere having a controlled humidity and oxygen content to prevent heat generation which causes spontaneous combustion. A suitable atmosphere is produced by displacing air in a storage enclosure with dehumidified combustion gases.

Detailed chemical kinetic study of the effect of molecular structure on autoignition of fuel-air mixtures

Abstract: Kinetic model is used to simulate the ignition of n-butane, isobutane, and n-pentane in air. Computed results are compared with data from shock tube experiments for the two n-alkanes, with very good agreement obtained. Model calculations under conditions of pressure and temperature encountered in internal combustion engines are reported. The influences of fuel molecular size and structure on autoignition rates are discussed in detail in terms of the site-specific H atom abstraction rates and subsequent fragmentation patterns of the alkyl radicals for each of the fuels considered.

Theoretical Study on Combustion of Injected Pulverized Coal in the Blast Furnace Blowpipe Zone

Abstract: Pulverized coal is being used increasingly as a blast furnace injectant. It is injected into a blowpipe zone where spontaneous ignition and combustion occur by mixing with the hot blast.A theoretical study is made on the ignition and combustion of injected coal particles in the blowpipe zone. The theory uses a simple combustion model in which diffusion of gaseous oxygen is dominant for the combustion rate. The derived results show the effects of coal properties and blast and injection conditions on the degree of burn out and the blast gas temperature at the tuyere nose. These results are compared qualitatively with reported experiments and reasonable agreement is obtained.In spite of some severe assumptions used in the theory for simplicity, the present objective is satisfied, which is to provide preliminary information for optimization of the injection conditions.

Aircraft Engine Oils and Their Behaviour at High Temperatures

Abstract: : Characteristics of aero-engine oils are changed considerably under high-temperature conditions ( > 200-250 deg C). Consequences of this are the formation of aging products and deposits, deficiencies in the tribological behaviour and spontaneous ignition, in extreme cases. The problems arising from these are illustrated using several selected examples, and their effects on engine functioning are described.

Novel experimental investigation of spontaneous ignition of gaseous hydrocarbons

Abstract: Studies of spontaneous ignition of gases under rapid compression1–3 are directed mainly towards understanding ‘knock’ in spark-ignition engines and the duration of ignition delays in diesels. The relevance to engine combustion lies in the ability to investigate the effects of fuel structure on the development of spontaneous ignition (arising either in different isomers of a hydrocarbon or due to reaction of mixtures of different hydrocarbons), while avoiding complicating practical features such as droplet evaporation, induction and exhaust of the charge, reciprocating piston motion and cycle-to-cycle variations. We report here a novel development, in which a variable-speed impeller in the combustion chamber of a rapid compression apparatus is used, first, to bring about spatial uniformity of temperature and concentration throughout the ignition delay period and, second, to enhance the rate of heat dissipation by successive increases in the speed of rotation. We show that, at given conditions for rapid compression, spontaneous ignition ceases to be possible beyond a limiting rotor speed.

Puff-Jet Ignition of Methane in an Internal Combustion Engine

Abstract: The puff-jet, a mechanically assisted ignition system, produces a turbulent ignition kernel that enhances the combustion of methane, a slow burning fuel. Detailed mapping of the puff-jet ignition system in a motored internal combustion engine has confirmed preliminary results. Compared with a spark gap ignition system, the puff-jet decreased both the ignition delay and the burn duration of methane charges in a motored single cylinder internal combustion engine and extended the lean misfire limit. Output power from the same engine run continuously on lean air-methane mixtures was increased using the puff-jet system because of the ameliorated combustion characteristics using that ignition system rather than a conventional igniter. Further, the output power from the engine running continuously with the puff-jet was almost the same as that achieved with a plasma jet igniter, without the concomitant high energy demand or electrode wear

An experimental study of the ignition and burning mechanisms in a pulse combustor (Combustion characteristics supplied with a propane-air mixture)

Abstract: The ignition and burning mechanisms of pulse combustion are experimentally investigated using a basic two-dimensional combustor supplied with a propane-air mixture. The forced mixture supply widens the pulsation limit to a practically usable one. the burning process is so rapid that there exists no flame in the combustor at the time of the mixture inflow in the next combustion cycle. The back-flow from the tail-pipe also contains no flame. Then the ignition of the mixture is found to be caused by a direct contact and rapid mixing with residual hot burned gases, which can be regarded as a spontaneous ignition. High-speed schlieren movies reveal that a pair of large scale eddy motions, formed by the in flowing mixture jet, promote reveal that a pair of large scale eddy motions, formed by the inflow mixture jet, promote the mixing of the mixture and hot nurned gases, resulting in a distributed reaction zone.

Spontaneous Ignition of Dust Deposits

Abstract: The temperature distribution in the combustible dust deposits placed in hot environments is described by a differential equation, according to the thermal theory. The temperature profiles of the dust deposits at any time could be calculated at various ambient temperatures by solving the equation using the finite element method. Thus, the minimum ambient temperature for ignition, which is defined as the ignition temperature, and the induction time to ignition could be determined. With a cylindrical cork dust deposit (volume=3.2×10-3m3, radius=0.08m), the resulting temperature distribution in the radial direction at any time agrees well with the experimental data currently reported by Leuschke, except for extremely high ambient temperatures. Therefore, it is practicable to estimate the spontaneous ignition behavior of dust deposits by computer simulation.

定常高温空気流中における燃料噴霧の着火 : 第2報,物理的因子の影響

Abstract: Spontaneous ignition was studied on fuel sprays injected into a steady hot air flow by a hole-nozzle with a single hole. Usually, the ignition delay is the so-called Arrhenius type and makes a straight line in an Arrhenius plot. In the present study, the effect of physical factors on ignition was investigated, and special attention was paid as to how the gradient of the straight line is decided. five kinds of experiments were carried out: Where pure fuels of iso-octane and n-heptane were used in the beginning, then the mixing condition was changed with a cylinder inserted into fuel jets or a wall facing a fuel nozzle, and the spray condition was changed with a change of fuel injection pressure or with a change of water content in n-propanol/water solution fuel or diesel-oil/water emulsion fuel. As a result, it was found that physical factors change ignition delay greatly, but have almost no effect on the gradient of the straight line in an Arrhenius plot. Then, the temperature dependency of the ignition delay is considered to be controlled almost completely by the chemical factor.

Steam ignition and control of an oxygen-driven fire flood injection well

Abstract: STEAM IGNITION AND CONTROL OF AN OXYGEN-DRIVEN FIRE FLOOD INJECTION WELL A method for initiating an in-situ combustion operation to recover oil from a subterranean, viscous oil-containing formation employing high purity oxygen as the combustion supporting gas. Initially, a predetermined amount of steam at a predetermined injection rate is injected into the formation via the injection well to clean the flowpath in the borehole and heat the formation adjacent the injection well. Thereafter, a mixture of steam and oxygen having a steam to oxygen molar ratio of 2 to 1 and a predetermined injection rate is injected into the formation to initiate spontaneous combustion and establish a combustion front followed by increasing the oxygen concentration of the injected gas to about 100 percent oxygen.

Rotary combustion engine

Abstract: The advantages obtained by means of the invention stem in particular from the fact that due to the variable compression, a spontaneous ignition engine is produced with quantitative control which requires neither injection pump nor cold starting aid. The adjustable valve timings, the ever-present torque arm of constant length, the absence of valve control parts, the low internal friction resistance, the completely balanced distribution of masses result in a high thermal efficiency. In addition it is possible at any time to use unleaded fuels, even ones with low knock ratings.

Spontaneous Combustion of Coal (IV)

Abstract: A Computer simulation of the spontaneous combustion of coal in a silo has been developed taking into consideration the mass transfer of oxygen via air diffusion in the pores of the coal zone. The numerical calculation has been carried out by a Finite Element Method (FEM). The adequacy of this model has been investigated by the comparison of the compared results with data obtained from a full-scale experiment with a coal silo.

Algorithms for the Detection of Spontaneous Combustion in Coal Mines

Abstract: Very effective detection of spontaneous combustion or open fires in coal mines can be provided from calculations based on measurements of a few parts per million of carbon monoxide (CO) in the ventilating air, even in the presence of CO from shotfiring, diesels and other sources. A project to develop automatic alarms is described.