igniter
Noun
1 a substance used to ignite or kindle a fire
[syn:
ignitor,
lighter]
2 a device for lighting or igniting fuel or
charges or fires; "do you have a light?" [syn:
lighter,
light,
ignitor]
English
Noun
- Any device that is used to ignite something, especially a
fuel mixture, or a charge
of explosive
A pyrotechnic initiator (also initiator or
igniter) is a device containing a
pyrotechnic
composition used primarily to ignite other, more difficult to
ignite materials, e.g.
thermites,
gas
generators, and
solid-fuel
rockets. The name is often used also for the compositions
themselves.
Pyrotechnic initiators are often controlled
electrically (called electro-pyrotechnic initiators), e.g using a
heated bridgewire or a bridge resistor. They are somewhat similar
to
blasting
caps or other
detonators, but they differ in
that there is no intention to produce a shock wave.
Composition
The energetic material used is usually a
pyrotechnic
composition made of a fuel and oxidizer, where the fuel
produces a copious amount of hot particles that cause/promote the
ignition of the desired material.
Initiator compositions are similar to
flash
powders, but they differ in burning speed, as
explosion is not intended, and
have intentionally high production of hot particles. They also tend
to be easier to ignite than
thermites, with whom they also
share similarities.
Common oxidizers used are
potassium
perchlorate and
potassium
nitrate. Common fuels used are
titanium,
titanium(II)
hydride,
zirconium,
zirconium
hydride, and
boron.
The size of the fuel particles is determined to produce hot
particles with the required burning time.
For special applications,
pyrophoric igniters can be
used which burst into flame in contact with air.
Triethylborane
was used as an igniter for the
Lockheed
SR-71 jet engines.
Common compositions
Metal-oxidizer
ZPP
One of the most common initiators is ZPP, or zirconium
- potassium perchlorate - a mixture of metallic zirconium and
potassium perchlorate. It is also known as NASA Standard Initiator.
It yields rapid pressure rise, generates little gas, emits hot
particles when ignited, is thermally stable, has long shelf life,
and is stable under vacuum. It is sensitive to
static
electricity.
BPN
Another common igniter formula is BPN, or boron -
potassium nitrate, a mixture of 25%
boron and 75%
potassium
nitrate by weight. It is used e.g. by
NASA. It is thermally
stable, stable in vacuum, and its burn rate is independent on
pressure.
Metal hydride-oxidizer
Metal
hydride-oxidizer mixtures replace the metal with its
corresponding
hydride.
They are generally safer to handle than the corresponding
metal-oxidizer compositions. During burning they also release
hydrogen, which can act
as a secondary fuel. Zirconium hydride, titanium hydride, and boron
hydride are commonly used.
ZHPP
ZHPP (zirconium hydride - potassium perchlorate) is a
variant of ZPP that uses
zirconium
hydride instead of pure zirconium. It is significantly safer to
handle than ZPP.
http://www.freepatentsonline.com/6117254.html
THPP
THPP (titanium hydride potassium perchlorate) is a
mixture of
titanium(II)
hydride and potassium perchlorate. It is similar to ZHPP. Like
ZHPP, it is safer to handle than titanium-potassium perchlorate.
http://www.freepatentsonline.com/6117254.html
Others
BNCP
BNCP,
(cis-bis-(5-nitrotetrazolato)tetraminecobalt(III) perchlorate) is
another common initiator material. It is relatively insensitive. It
undergoes
deflagration to
detonation transition in a
relatively short distance, allowing its use in
detonators. Its burning
byproducts are of relatively little harm to environment.
http://www.patentgenius.com/patent/6672215.html
It can be ignited by a
laser
diode.
Lead azide
Lead azide
(Pb(N3)2, or PbN6) is occasionally used in pyrotechnic
initiators.
Others
Other materials sensitive to heat can be used as
well, e.g.
tetrazene,
lead mononitro-resorcinates, lead dinitro-resorcinates, and lead
trinitro-resorcinates.
http://www.patentstorm.us/patents/5942717-description.html