【 Weak current College 】 explosive detonation velocity of detonation, and clearance effects---Power By 【 China power house network 】

Detonation is explosive decomposition occurs in the moment should be of a particular form, its essence is a detonation wave propagation with explosives. Detonation is the detonation of the first front, with the shock of the chemical should be district, detonation is detonation of excitation source. Detonation is characterized by:
　　
(1) chemical reaction area very thin, condensed phase explosive chemical reaction zone thickness between the 0.5mm ~ 2.5mm;
　　
(2) chemical reaction area to the regular transmission, the speed is greater than the explosive sound.
　　
(3) on the Wavefront produces very high temperature gradient and the pressure gradient.
　　
I. detonation velocity
　　
Explosive detonation wave propagation speed is called a detonation velocity. Commonly used explosive detonation velocity in 2500m\s ~ 7000m/s. Impact of explosive detonation velocity:
　　
(1) grain diameter. Detonation velocity with grain diameters grows when grain diameter increase to a certain value, the detonation velocity can be close to the ideal explosion intensive grain as ideal closure, detonation products without radial flow can achieve the ideal detonation velocity). On the other hand, reduce grain diameter, detonation velocity will decrease accordingly. When grain diameter decreases to a fixed value, the detonation wave will no longer be stable transmission, will eventually burst out, this is because the effective energy is reduced to no longer to hold the detonation stability. Detonation can stabilize the dissemination of the smallest grain diameter are called critical diameter, the diameter of the blast express criticality is called critical detonation velocity.
　　
(2) explosive density. For pure dynamite, detonation velocity with density grows; for mixed-explosive, density and detonation velocity of relationship is more complex. In a certain range, round stones large density improves ideal detonation velocity; but more than this range continues to increase density, leads to the detonation velocity drops, eventually leading to put explosive.
　　
(3) explosive particle size. Size does not affect the explosive detonation velocity of the ideal, but reduce the size of the General can improve the responsiveness of the explosives, reducing response time and reaction zone thickness, thereby reducing critical diameter, improve the detonation velocity.
　　
(4) grain shell. Grain shell does not affect the explosive detonation velocity of the ideal. But shell can reduce critical diameter of explosives, so when grain diameter smaller, detonation velocity of the detonation velocity from ideal difference is large, enhanced shell increases the detonation velocity, the effect is the same as increasing grain diameter.
　　
Second, the space effect
　　
Mixed-explosive thin continuous grain, usually in the air are functioning booster. But in the drill hole, if grain and perforation hole wall gap between, often occur detonation interrupt or detonation into combustion phenomena. This phenomenon is called clearance effects (once called Groove effects or pipeline effect). It not only reduces the blasting effect, and in gas mine for blasting, if explosives occur burning, there is the possibility of accidents.
　　
Clearance effect occurs because when the propellant detonation, produced in the air gap ahead of detonation wave propagation of air shock wave. Blast pressure, explosives within baiyao column surface to the spread of compression waves in the grain deformation, compact grain surface conical compression area. Compression zone can be seen as inert layer, thereby reducing the grain diameter, when the grain diameter decreases to less than the critical diameter, can cause detonation. In addition, when ahead of detonation wave after wave of air will be sparse production reactor reverse, reverse sparse wave will weaken the detonation wave propagation.
　　
In blasting works, clearance effects not only affects the blasting effect and influence on this. particularly in methane and coal dust explosion hazard of mine. Therefore, in engineering practice should, as far as possible, eliminate clearance effects. Measures to eliminate clearance effects are:
　　
(1) use of coupling bulk explosives elimination of radial clearance, can radically overcome clearance effects;
　　
(2) the use of ammonium nitrate mixed explosives, create gaps less likely effect;
　　
(3) in continuous charge, at a certain distance (or in connection with power phase Pro-end Office) on cardboard or made of other materials, its outer diameter at slightly less than the drill hole, the space dividers, to prevent gaps in air shock wave propagation or diminish its intensity;
　　
(4) use critical diameter is small, the detonation of good performance, the effect of the clearance of explosive strength resistance.