Environmental Engineering Reference
In-Depth Information
explosives is the reacted volume within unit time and unit area of
fl
flame fronts
(Eq.
2.1
).
V
S
u ¼
ð
2
:
1
Þ
Here, V represents the burned/combusted volume within unit time; S represents
the total surface area of
flame fronts.
The mass speed (m) of combustion is de
fl
ned as the mass amount of explosives
consumed per unit time and unit
flame front area. The mass speed of combustion is
a function of the explosive density and the linear speed (Eq.
2.2
).
fl
m
¼
q
u
ð
:
Þ
2
2
Combustion process has stable and unsteady combustions. The stable combus-
tion of explosives presents that single component explosive has a constant burning/
combustion speed under certain conditions (e.g.,
xed pressure, temperature,
packed density, etc.). Most of liquid explosives can reach stable combustion. The
combustion of explosive is not always stable. For mixed liquid explosives, the
combustion speed may accelerate or slow down, sometimes accelerate or slow
down suddenly. The main reason is the nonuniformity of mixtures.
Acceleration of unsteady combustion leads to faster combustion,
finally deto-
nation. Slowing down results in the slower combustion, to burning off. Whether an
explosive explodes
finally is determined by its combustion speed.
2.2.1.2 Combustion of Volatile Liquid Explosives
Liquid explosives have different volatilities, which varied the combustion pro-
cesses. The important characteristic is the variation of reaction phase in the com-
bustion reactions. Generally, because alkyl nitrates and some of alkene nitrates are
highly volatile, their combustion reactions proceed in gas state. In contrast, the
combustion reactions of nitroglycerine, azide nitrate ether, and aqueous hydrazine
proceed in both gas and solid phases. The reactions of mercury fulminate and urea
perchlorate mainly proceed in solid state.
To simplify the
fl
flame propagation, the assumption is based on
fl
flame propagation
with a
filled in
a pipe. The ignition device is used to induce the combustion of liquid explosives
from one end. At
fixed speed toward the liquid in only one dimension. Butyl nitrate is
first, only the explosive (which is very close to the ignition
device) starts burning. The propagation of
fl
flames is shown in Fig.
2.1
.
The propagation of
fl
flames proceeds the reaction zone forward till the end of the
pipe. The
fl
flame fronts isolate the reacted and nonreacted zones. Every moment of
fl
flame propagation reaction is in process of the thin layer close to
fl
flame fronts. The
preheating layer isolates the nonreact zone and
fl
flame fronts. The speeds of
fl
ame
propagation are determined by the chemical properties of liquid explosives.
