Concentration Limits of Detonation

HE charge weight Equivalence ratio limits Vol% H2 limits Publication 

Concentration limits of detonation depend on the power of the initiator, its geometrical dimensions and on the initial conditions (for example, the mixture temperature). An increase in the initiator weight and the temperature widens the range of concentrations which allow the detonation to propagate throughout the mixture. 

Earlier, based on data from [22, 23], it was assumed that the concentration limits for detonation in H2 + air lie in the range of 18.2-58.9% H2 (the combustion limits were from 4% H2 to 75% H2). It was also assumed that the detonation was suppressed in a stoichiometric mixture diluted with more than 30% water steam (the combustion suppression was recorded at more than 55% dilution with water steam). 

Measurements performed using large-scale test arrangements [24-26] resulted in a more pessimistic assessment of the detonation limits in H2 + air mixtures (9.4-76.9% H2) the water steam concentration necessary for detonation suppression was about 39% of the mixture volume. The experimental data revealed that the 

Mixture composition Diluter T,K Combustion limits Detonation limits 

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Crussard [4] points out that for the mixture 2CO + 02, in which the measured detonation velocity is variable and close to 1210 m/sec, in a shock wave propagating with a velocity of 1210 m/sec the compression temperature is 720°C, so that at this temperature a noticeable delay in auto-ignition is still possible. In 1924-1925 Wendlandt [10], a student of Nemst, energetically defended the view that the gas is ignited by a shock wave with a velocity equal to that of the detonation wave. Wendlandt studied in detail the concentration limits of detonation propagation in explosive mixtures and... 

Table 7.7 Concentration limits of detonation initiated by an HE charge in H2 + air mixtures...

Fig. 5.24 Concentration limits of slow flames 1, fast flames 2 and deflagration -to - detonation transition (DDT) in H2 + air and CH4 + air in tubes of various diameters. DDT limits are given for tubes with blockage ratio BR = 0.3...

If the reaction order does not change, reactions with n < 1 wiU go to completion in finite time. This is sometimes observed. Solid rocket propellants or fuses used to detonate explosives can bum at an essentially constant rate (a zero-order reaction) until all reactants are consumed. These are multiphase reactions limited by heat transfer and are discussed in Chapter 11. For single phase systems, a zero-order reaction can be expected to slow and become first or second order in the limit of low concentration. 

Homogeneous mixtures of concentrated peroxide with alcohols or other peroxide-miscible organic liquids are capable of detonation by shock or heat [1]. Furfuryl alcohol ignites in contact with 85% peroxide within 1 s [2], Detonability limits of mixtures with 2-propanol have been measured. Approximately stoichiometric combinations of 50% hydrogen peroxide and the alcohol could be made to detonate, as could a wider range of mixtures with higher test peroxide [3],... 

The peroxyacids were until relatively recently the most powerful oxidants of all organic peroxides, and it is often unnecessary to isolate them from the mixture of carboxylic acid and hydrogen peroxide used to generate them. The pine lower aliphatic members are explosive (performic, particularly) at high, but not low concentrations, being sensitive to heat but not usually to shock. Dipicolinic acid or phosphates have been used to stabilise these solutions. The detonable limits of peroxyacid solutions can be plotted by extrapolation from known data. Aromatic peroxyacids are generally more stable, particularly if ring substituents are present [1],... 

Ozone is endothermic, thus it can burn or detonate by itself and represents the simplest combustible and explosive system, The concentration threshold for spark-initiated explosion ofliquid ozone in oxygen at — 183°C is 18.6 mol % O3 the concentration limit for shock wave-initialed detonation of gaseous ozone-oxygen at 25°C is 9.2 mol % O3. Gaseous ozone exhibits three principal absorptions in the infrared at 710. 1043, and 2105 cm-1... 

Many interesting questions remain to be answered about spinning detonation. Why does spin always appear at low concentrations near the detonation limit What determines the stable mode and amplitude of the spin What effect, if any, does spin have on the stability of detonations ... 

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