Ignition adiabatic compression

Much work has been done on the adiabatic compression ignition of NPN vapor mixed with various gases by both NOL (Ref 2) and Brit Imp Chem Inds (Ref 4). A table of compression ratios and resultant temps from the detons of NPN vapor saturated gas mixts is presented below... 

The temperature of ignition of a mixture fired by adiabatic compression Is lower than when the same mixture is fired by being heated in a glass or silica tube at atmospheric pressure. Professor H B. Dixon in a private communication to the author states that he found the ignition temperature of electrolytic gas under the latter conditions to be 580° C. 

Evans and Yuill [49] investigated the ignition of mercury fulminate by the adiabatic compression of the atmosphere surrounding it. They calculated that a 50% response corresponds to a temperature of 530°C. 

Evans and Yuill [51] showed that lead styphnate may be ignited by adiabatic compression of air, the calculated temperature amounting to 660°C, whereas Bryan... 

Ignition temperature was used with partial success (52, 57, 74, 135,189). Results depended critically on the method used—e.g., adiabatic compression, ignition limits in tubes, or crucible method. Jackson (70, 86, 87) determined ignition temperatures for a large number of hydrocarbons by the crucible method and developed correlations with structure. 

Ignition delays, investigated in adiabatic compression machines (89, 91, 92, 106, 182, 209, 212, 213), have been correlated with knock (90, 93-5, 111, 158, 160, 194, 203). Ignition occurs in two stages. Levedahl (106) examined the effects of temperature, density, and fuel type on the induction periods, ti and r2, corresponding to each ignition stage. A close correlation existed between total delay, r, and knock resistance. Sensitivity was explained in terms of the relative partial contributions of n and r2 to r. 

The so-called "secondary or after flame which arises from the combination of reaction products of primary flame (such as of CO) with surrounding oxygpn in the air, is also dangerous. Other causes of ignition include any naked flame present in mine hot or inflamed particles ejected from the expl adiabatic compression of the gas by a shock wave at supersonic velocity general adiabatic compression of a body or pocket of gas electric sparks or sparks produced by drills hitting stones (which are sometimes embedded in coal) (Refs 7b, 7c, 16a, 22 31)... 

It is known that ignition and expln of dangerous coal mine atmosphere depends on many factors, such as compn of mine atm, wt of charge of expl, induction period (time elapsed betw expln of charge and ignition of mine atm), temp of products of expln, presence of hot solid particles in products of expln, duration of flame, heating of mine atm due to adiabatic compression created by incident and reflected shock waves, etc. 

Problem 1 Will the firedamp of initial temp 27 and ignition point of 650°C be ignited by adiabatic compression to 20 atm, created by an incident shock wave ... 

We see the reason for this increase in Texp and NO in a more rapid rise in pressure and an approach to adiabatic compression. Interest attaches to a circumstance observed in the experiments at p0 = 200 mm in the glass apparatus where the amount of nitric oxide changed when the point of ignition was transferred to the center of the flask P (Fig. 1) the conditions of the chemical reactions in the flame front do not change it is only the conditions of the subsequent compression of the combustion products which are affected. The question has been investigated in detail by Frank-Kaimenetskix [7]. We shall merely observe here that the influence of the conditions of compression of the combustion products on the yield of nitric oxide proves the thermal nature of the reaction, since the compression is effective after combustion, when the reaction of the fuel with oxygen has ended,. Such an influence would be impossible from the point of view of an induced reaction. 

The majority of researchers lean to the point of view, shared and developed further by the author, that the beginning of the chemical reaction, ignition, is related to heating of the gas above its auto-ignition temperature by adiabatic compression in a shock wave. It is precisely for this reason that we shall first consider other points of view and objections encountered in the literature against this conception. 

In fact, Vant Hoff s 250 atm and Nernst s pressure significantly higher than 100 atm [21] are the pressures that explosive mixtures, adiabatically compressed to the temperature of auto-ignition, may develop in combustion. 

THE IGNITION TEMPERATURES OF HYDROGEN AND OXYGEN AS DETERMINED BY ADIABATIC COMPRESSION. (Dixon and Crofts, 1911.)... 

Johansson and co-workers (7, 8, 9) have shown that heat transfer from a compressed spherical bubble does not increase the temperature of its liquid surface sufficiently to account for the impact sensitivity of liquid explosives the high sensitivity of nitroglycerin is postulated as arising from the fact that small droplets are readily formed by the impact and ignited by the compressed air. Bolkhovitinov (1) postulated crystallization of the liquid under the impact pressure, with the phase transition causing the temperature increase which causes explosions. Bowden (3) favors the adiabatic compression of gas bubbles combined with the dispersion of the explosive into fine particles as the mechanism for initiation by mechanical impact. 

---