Showing papers on "Spontaneous combustion published in 1970"

Shock-wave ignition of liquid fuel drops

Abstract: Combustion processes and ignition criteria in shock wave ignition of liquid fuel drop in oxidizing atmosphere

Spontaneous ignition of oil sands

Abstract: In planning oil recovery by in situ combustion, one problem is how to ignite the formation. Ignition can be effected by heating the formation around the injection well or by injecting an easily reacting chemical compound prior to injecting air. In some field experiments (General Petroleum's project in S. Belridge and Shell's field test in W. Venezuela), no special measures appeared to be necessary. The formations ignited spontaneously when air was injected for a prolonged period to determine the gas-flow distribution in the formation underlying the test site. This showed that at least in some oil reservoirs, oxidation rate of the crude at reservoir temperature is high enough to heat the reservoir locally to ignition temperature in a reasonable short time. Spontaneous-ignition times depend on the initial formation temperature and the reactivity of the crude, and may vary from a few weeks to several months. For this reason, it is desirable to have an estimate of how long spontaneous ignition will take, so that ignition by artificial means may be considered soon enough. A method for predicting the ignition time on the basis of measured oxidation rates of the crude is given.

Thermal Effects Accompanying Spontaneous Ignitions in Gases. I. An Investigation of the Heating Effects Which Accompany the Rapid Admission of Inert Gas to an Evacuated Vessel

Abstract: In experiments on spontaneous ignition of gases, transient temperature changes normally accompany the entry of gases to evacuated vessels. They may invalidate much quantitative experimental work and give rise to spurious observations. In the present investigation, temperature–time histories accompanying gas entry have been mapped with a fine (13 μ m) thermocouple for many positions in a spherical vessel. It is found that although transient (characteristically, 0.1 s), the temperature rises can be large—perhaps 200 °C—and are appreciable even for gases at low pressures. They arise from adiabatic heating of the entering gas. Experiments with 18 different gases show that heating is greatest for monatomic molecules (large γ ; low C v ) and least for complex molecules (small γ ; large C v ). The effects are mitigated by conductive heat losses; such losses are greatest at low pressures, in small vessels, and for gases of high thermal diffusivity. The effects of convection are apparent at higher pressures. The implications of the results are various. Not only do they concern many laboratory measurements on spontaneous ignition, but they are also important for the large-scale handling of potentially reactive gases or gas mixtures, especially involving simple small molecules (as in mixtures with air, halogens or oxygen).

Study on Ignition Lag and Flame Propagation in Spark Ignition Engines

Abstract: The ignition lag in the spark ignition engine was determined by detecting the ion current through the spark plug itself, which was caused by the ions produced by the combustion immediately after the ignition spark. The influences of mixture ratio of fuel and air, electrode spacing and dilution with incombustible gas on the ignition lag of propane-air mixture in the closed vessel were made clear by this technique. In a two-stroke cycle gasoline engine, the ignition lag and the subsequent flame propagation and cycle-to-cycle variations in them were investigated. The results are as follows : (i) The cycle-to-cycle variations of ignition lag are hardly affected by the mixture ratio, the content of residual gas and by the engine speed. (ii) The cycle-to-cycle variations of the flame propagation and the maximum pressure in the cylinder are hardly affected by the cycle-to-cycle variation of ignition lag.