Critical diameter, determination

The measurements were made using different experimental apparatus such as narrow pipes, diaphragms with a round hole, flat slots, etc. Values of the critical diameter determined using noncircular apertures have been converted to equivalent circular apertures. 

The experimental values of the critical diameter were determined over a wide range of temperatures and pressures. 

The influence of temperature on detonability limits was not determined in the laboratory of Dr Price, but only search of literature is repotted. There are few data showing a limit curve in the diameter-temperature plane, but one set for NMe (Nitromethane) was reported by Campbell et al (Ref 4a) to exhibit the expected decrease in critical diameter with increase in temperature. However, NMe is a physically homogeneous liquid expl and its behavior differs, probably, from that of heterogeneous expls. Of the two references mentioned by Price, one (Ref 15) concerns granular charges of AN, while the other (Ref 16) deals with one propellant compn. In both cases, there seems to be a marked lowering of... 

I. Jaffe "A Method for the Determination of the Critical Diameters of Explosives , NavWepsRept 7360(1960), USNavalOrdnLab, White Oak, Silver Spring, Md... 

In examining the process of initiation of expls, ic is of importance to determine not only the critical density, p, and critical diameter, dc, of a detonator (or booster), but also its critical length, lc, which is the shortest length required for steady state detonation. It is known that if the initial velocity of shock wave of an initiator is equal to or lower than the velocity of sound, C0, in the charge to be initiated, no detonation can take place even with a large initiator. This means that the critical detonation velocity of an initiator, Dc, must be higher than a certain value which is different for each explosive to be initiated. Another requirement for successful detonation is that pressure at the front of a detonation wave produced by initiator at the expense of chemical energy, must be maintained at a certain minimum level... 

Experimental evidence to support this behavior is given and the implications of these results for the problem of determining critical diameter in composite solid propellants are discussed in the paper of Gordon Refs 1) W. Jost, "Diffusion , Academic Press, NY (1952), p 459 2) Cook (1958),... 

For determination of critical diameters, the test s described under Detonation Velocity-Charge Diameter and Density Relationships, Experimental Procedures can be used... 

In the preceding sections we have emphasized the importance of knowing the heats of formation of explosive materials in order to estimate AH, detonation product compositions, fire explosion hazards of potentially dangerous materials, and critical diameters for thermal explosions. This is by no means a complete list of the uses of heats of formation. Thus the AHf° of a compound is indeed one of its most useful properties. However, how does one proceed if the AHf° for a material of interest has not been determined experimentally The obvious answer to this is by estimating AHf° on the basis of theoretical or semi-empirical methods. Many such methods exist. The following article contributed by Dr. Robert Shaw of SRI presents a method that is particularly applicable to estimating the heats of formation of explosive compounds... 

In fact the interval of variation of the reaction rate in a flame is so large that the formulas into which the reaction rate enters do not even determine the order of magnitude of the flame velocity and critical diameter until the conditions—temperature and concentration—to which the reaction rate relates are indicated. By entering the dependence of the reaction rate on the temperature into Daniell s equations, we render them unsolvable. 

Thus we see that the ratio amplitudes for the particle and the sound wave (or gas element), for constant values of p and p, depend upon the term nd2, so that for a particle having a diameter d the ratio corresponds to one and only one frequency n. Therefore, we conclude that nd2 is a critical function determining the behavior of a particle in a vibrating field. 

Bagnold has determined the Reynolds number which fixes either the critical diameter or the threshold velocity gradient. He has found that when... 

The effects evaluation will determine the likelihood of a transition to propagation and the consequences that can occur, critical height/depth and critical diameter tests will be performed to determine the detonability of a material in bulk or layer form (on a conveyor). Based on the transition results, a decision is made to complete one of the following effects evaluation tests such as a) firespread test which will include rate of flAme spread, heat of flux, and occurrence of fire brands and b) airblast tests including fragment tests. 

The critical diameter of slurry explosives was detennined by Michol and Bigourcl [97]. Tlie smallest critical diameter (22 mm) is shown by slurry with, A1 (density 0.95) ami with methylamine nitrate (density 1.00), Also the method of determining the critical diameter has been given [98]. 

The ability to predict drop size is critical to determining both the interfadal area for mass transfer and the state of dispersion of the system. In dilute systems and in moderately concentrated systems where coalescence can be neglected, the following equation describes the maximum equilibrium (i.e., after a long time) drop diameter of an inviscid or low viscosity dispersed phase ... 

The critical diameter of lead azide for Unconfined powders or crystals has not been established and cannot be until one determines the pressure or absence of detonations in the small dimensions cited above. In the case of heavily confined charges, work on swaged-lead detonating cord lead to the expression [24]... 

Table 5F. 1 Characteristic parameter in the critical point determined for capillaries with three different lengths and constant inner tip diameter of 2r p = 0.15mm, Fainerman Miller (1994b)...

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