Environmental Engineering Reference
In-Depth Information
is reached, the stability of combustion is broken, and the combustion experiences an
abrupt transform to detonation. For
flammable gas mixture, the shock wave is pro-
duced in the nonreacted liquids close to
fl
flame front, while the shock wave is gen-
erated in the gas products of incomplete reactions. The shock wave plays dual roles
here. It increases the pressure of the liquid explosives, which is close to the burning
fronts, uniforms the liquid surfaces, reduces the gaps of intersurfaces, and lowers the
burning rate. The shock wave also leads to the thermal explosions of intermediates or
liquid explosives of local area. The pressure jumps from thermal explosions, impacts
back to unreacted liquid explosives, and leads to detonation.
The change of burning of liquid explosives to detonation experiences four stages
fl
—
agration, and
steady detonation. Heat transfer and initiated mechanisms are different in these four
stages. Heat transfer of steady self-sustaining combustion is achieved by heat
conduction. In convection combustion, the gas products inside spare surfaces ignite
the inside surfaces of the gaps of liquid explosive molecules which is immigrated
from the liquid bulk. It helps to increase the surface area/unit volume/mass, and the
mass burning rate is about hundreds times than that of steady self-sustaining
combustion. The stability of combustion is broken, and heat transfer comes true
through forced convection. Heat transfer of de
steady self-sustaining combustion, convection combustion, de
fl
agration is initiated by weak shock
waves. Stable detonation is induced by strong shock waves. The total reactions
accelerate, and the relative active stages have something with the physical and
chemical properties of liquid explosives and the experiment conditions.
It is believed that after the stable combustion is broken, the explosion rates of
explosives straighten up until stable detonation occurs. But the writer does not
agree with it. In the writer
fl
agration stage between unsteady
burning and normal detonation. It is also the new discovery from the explosion
characters/features of liquid explosives.
The de
'
is opinion, there is a de
fl
agration is stable under certain conditions. For example, when the
charge diameters of the liquid explosives (e.g., H
2
O
2
-
fl
(CH
3
)
2
NNH
2
or N
2
O
4
-
CH
2
(NO
2
)CH(NO
2
)CH
3
) are large (1,500
2,000 mm), the burning may not be
-
stable. The de
agration stage is void and the reactions change from burning to
detonation directly.
According to the experiments, when the pressure inside the containers (it is
charged explosives) is lower than certain critical value P
′
fl
(P < P
′
), the de
fl
agration
is stable. If P > P
′
, the de
fl
agration changes to detonation. The exchange of def-
f-
l
lagration to detonation is achieved in a jump range.
For the bicomposition liquid explosives or severely volatile explosives, there is
no obvious de
agration stage in the change process from combustion to detonation.
Convection combustion develops into detonation directly. The key feature of this
change is that the detonation occurs in the fronts of convection combustion. In
volatile liquids, the convection combustion develops rapidly, and forms shock
waves in the front of
fl
flame fronts. The pressure of liquid surfaces accelerates the
heat transfer into the inside of liquids, and leads to the heat explosion in local zone,
then to the detonation of other space. If liquid explosives are charged in closed
containers,
fl
