Bubble energy

PETN is an effective underwater expl. Its shockwave energy and bubble energy relative to Pentolite (see in this Vol) are 1.15 and 1.13, respectively (Ref 21 a)... 

Cole (Ref 1) described methods and presented data for measuring the underwater effects of expls. Price (Ref 3) suggested that the underwater effectiveness of an expl can be indicated by the sum of its shock wave and bubble energy equivalent wts (in her paper relative to 50/50 Pentolite). In Table 2 we compare such indices of underwater performance (but relative to TNT rather than Pentolite) with relative heats of detonation. We used 1.09kcal/g for the heat of detonation of TNT under the assumption that... 

Mixtures of TNT, RDX, and/or AN are used as TNT-based explosives. Various additives such as aluminum powder, barium nitrate, and/or some other small amounts of materials are used. Densities are in the range 1450-1810 kg m"l Aluminum powder is added to obtain bubble energy when used in underwater conditions. 

When an explosive is detonated in water, a shock wave propagates through the water accompanied by a bubble. The chemical energy of the explosive is converted into shock wave energy and bubble energy. The volume of the bubble is increased by the expansion wave and decreased by the compression wave in an oscillatory fashion. The maximum size of the bubble is determined according toili i i... 

Experimental results of underwater explosion tests using an emulsion explo-sivecomposed of ammonium nitrate and hydrazine nitrate showed 0.85 MJ kg for the shock wave energy and 2.0 MJ kg for the bubble energy. The shock wave energy of underwater explosions is increased by the addition of aluminum powder to the explosives. The aluminum powder reacts with H2O molecules in the bubble. Large amounts of Hj molecules and heat are produced by the oxidahon of the A1 with H2O according to ... 

The AI-H2O reaction increases the temperature and the number of moles of gas in the bubble by the production of H2 molecules. The pressure in the bubble is thereby increased. As a result, the bubble energy and shock wave energy are increased. It must be understood that the oxidation of aluminum powder is not like that of gaseous reactants. Reaction occurs at the surface of each aluminum particle and leads to the formahon of an aluminum oxide layer that coats the particle. The oxidized layer prevents the oxidation of the interior particle. The combustion efficiency of aluminum parhcles increases with decreasing particle size.l =l The shock wave energy and bubble energy are increased by the use of nano-sized aluminum powders. 

No information at our disposal for its brisance and power, but accdg to investigation conducted at Hercules Powder Co Laboratory (Ref 2), mixts TNEtTNBu with A1 powder yielded about 30% more shockwave energy and 80—90% more bubble energy than did HBX-1 (RDX 40, TNT 38j A1 17, D-2 Wax 5 and Ca chloride 0.5 added)... 

Underwater Shock Wave and Bubble Energy Equivalent Weight Ratios for... 

Relative Potential Bubble Energy (RPBE) The cube of the ratio of the maximum bubble radius constants (J s) ... 

In recent years it has become popular to characterize the effectiveness of industrial expls in terms of their measured underwater shock and gas bubble effects (Refs 6,18 21). For example, it is claimed (Refs 6 21) that measured gas bubble energies correlate well with performance of the expl in breaking rock... 

In this test the total explosive energy was postulated to be the sum of the shock wave and bubble energies... 

In addition to measuring shock wave and bubble energies, underwater tests also can measure the shock wave impulse, another indicator of explosive strength. The shock wave impulse is derived by measuring the area under the pressure-time curve for a selected integration time interval at a known distance from the explosion... 

Occasionally it is desired to compare expls on the basis of shock pressure and/or relative bubble energy. Table 6 (from Ref 17) shows the weight ratios for several expls relative to Pentolite. If the weight ratio is greater than unity, the expl is more powerful than Pentolite, and conversely... 

Aluminized expls exhibit a decrease in performance as their packing density approaches theoretical maximum density (TMD). This effect is more pronounced in compns of high A1 content. Table 9 (from Ref 17) shows equivalent weight ratios (WQd) and relative bubble energies (RBE) of two aluminized expls as a function of %TMD... 

Ref 2) we obtain the following comparison of shock and bubble energies (in cal/g) with the heat of detonation for 1.6g/cc PETN and Pb Azide ... 

As in the case of TNT, the sum of the shock and bubble energies for these two expls agrees closely with measured heats of detonation... 

In Section II it was stated that measured underwater bubble energy is being used to estimate performance of commercial expls. 

A correlation between measured bubble energy and computed expansion work, E, is presented in Fig 30 (Ref 16). The quantity Ewjc is obtained from theoretical considerations. Usually it is less than the heat of detonation... 

Bjarnholt and coworkers (Refs 13 and 21) used a semi-empirical approach to estimate the useful energy of HE via underwater expln energy measurements. In essence, their approach involves computation of a shock toss factor, ft > 1, to estimate the shock energy at the HE/water boundary from measured shock energies at some distance from the HE. This is coupled with the assumption that the measured bubble energy at some distance from the HE equals the bubble energy at the HE/water boundary. Then the total underwater expansion work per unit mass of HE, A0, is given by ... 

Bubble Period Measurements(Used for Bubble Energy Measurements). See under Underwater Explosions... 

Shock Energy Generated, MJ/kg Bubble Energy, MJ/kg Deton Press, GPa Heat of Deton (—A Hd), MJ/kg Expansion Work, MJ/kg... 

In the Ballistic Mortar and Trauzl Block tests, Tetryl is 130% and 125% of TNT, respectively (Ref 46a). In air shock overpressure, in the 3—20psi range, the TNT equivalent weight of Tetryl is 1.07 (Ref 62). In underwater performance, the pentolite equivalent weight of Tetryl is 1.00 for shock energy and 0.98 for bubble energy (Ref 20), The Gurney Constant for 1.62g/cc Tetryl (quoted in Ref 71) is 2.5km/sec. This value seems low... 

The bubble energy is conveniently expressed as the sum of the pressure-volume work, 6pV, the surface kinetic energy, eSKl the surface potential energy, eSP, and the volume kinetic energy, eVK, arising from the removal of atoms from the cavity boundary to the bulk of the liquid. 

Using two kinds of supporting frame shown in Fig.3.122, the sample was fixed in the center of the frame, sunk to a specific depth by a crane and initiated. The frame shown in Fig.3.122(a) was used to determine the bubble energy of initiators at a depth of 0.4 m. In the variable initiation test and the variable sample test, in which larger charges were studied, the set-up shown in fig. 3.122(b) was used for a depth of 1.0 m. Thin wire was used to bind the components in place. The atmospheric pressure needed i the calculation was measured at the site every hour. 

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