Patent for Contrail Generation Method
(continued)
by DONALD WERLE ET AL
Attorney, Agent, or Firm: Sciascia; Richard S.;
St.
Amand; Joseph M.;
Primary/Assistant Examiners: Blix; Trygve M.;
Kelmachter; Barry L.
U.S. References:
Show the 1 patent that references this one
Patent
Issued
Inventor(s) Applicant(s) Title
US1619183* 3 /1927 Bradner et al.
US2045865* 6 /1936 Morey
US2591988* 4 /1952 Willcox
US3531310 9 /1970 Goodspeed et al.
PRODUCTION OF IMPROVED METAL OXIDE PIGMENT
USR0015771* 2 /1924 Savage
* some details unavailable
CLAIMS:
[Hide claims]: What is claim is:
1. Contrail generation apparatus for producing a
powder contrail having maximum radiation
scattering
ability for a given weight material,comprising:
a. an aerodynamic housing;
b. a jet tube means passing through said
housing,
said
tube means having an inlet at a forward end of
said
housing and an exhaust at a rearward end
thereof;
c. a powder storage means in said housing;
d. a deagglomeration means also in said housing;
e. means connecting said powder storage means
with
said deagglomeration means for feeding radiation
scattering powder from said powder storage means
to
said deagglomeration means;
f. the output of said deagglomeration means
dispensing
directly into said jet tube means for exhausting
deagglomerated powder particles into the
atmosphere
to
form a contrail; and
h. means for controlling the flow of said powder
from
said storage means to said deagglomeration
means.
2. Apparatus as in claim 1 wherein said jet tube
means
is a ram air jet tube.
3. Apparatus as in claim 1 wherein an upstream
deflector baffle is
provided at the output of said deagglomeration
means
into said jet tube means to produce a venturi
effect
for minimizing back pressure on said powder
feeding
means.
4. Apparatus as in claim 1 wherein said
deagglomerator
means comprises:
a. means for subjecting powder particles from
said
powder storage means to a hammering action to
aerate
and precondition the powder; and
b. a jet mill means to further deagglomerate the
powder into separate
particles.
5. Apparatus as in claim 4 wherein pressurized
gas
means is provided for operating said
deagglomeration
means.
6. Apparatus as in claim 1 wherein said
radiation
scattering powder particles are titanium dioxide
pigment having a median particle size of about
0.3
microns.
7. Apparatus as in claim 1 wherein said
radiation
scattering powder particles have a coating of
extremely fine hydrophobic colloidal silica
thereon
to
minimize interparticle cohesive forces.
8. Apparatus as in claim 1 wherein the
formulation
of
said powder
consists of 85% by weight of TiO2 pigment of
approximately 0.3 micron media particle size,
10%
by
weight of colloidal silica of 0.007 micron
primary
particle size, and 5% by weight of silica gel
having
an average particle size of 4.5 microns.
9. The method of producing a light radiation
scattering contrail,
comprising:
a. surface treating light scattering powder
particles
to minimize
interparticle cohesive forces;
b. deagglomerating said powder particles in two
stages
prior to dispensing into a jet tube by
subjecting
said
powder particles to a hammering action in the
first
stage to aerate and precondition the powder, and
by
passing said powder through a jet mill in the
second
stage to further deagglomerate the powder;
c. dispensing the deagglomerated powder from the
jet
mill directly into a jet tube for exhausting
said
powder into the atmosphere, thus forming a
contrail.
10. A method as in claim 9 wherein said light
scattering powder
particles is titanium dioxide pigment.
11. A method as in claim 9 wherein said powder
particles are treated with a coating of
extremely
fine
hydrophobic colloidal silica to minimize
interparticle
cohesive forces.
12. A method as in claim 11 wherein said treated
powder particles are further protected with a
silica
gel powder.
Background/Summary:
BACKGROUND
The present invention relates to method and
apparatus
for contrail
generation and the like.
An earlier known method in use for contrail
generation
involves oil smoke trails produced by injecting
liquid
oil directly into the hot jet exhaust of an
aircraft
target vehicle. The oil vaporizes and
recondenses
being the aircraft producing a brilliant white
trail.
Oil smoke trail production requires a minimum of
equipment; and, the material is low in cost and
readily available. However, oil smoke requires a
heat
source to vaporize the liquid oil and not all
aircraft
target vehicles, notably towed targets, have
such
a
heat source. Also, at altitudes above about
25,000
feet oil smoke visibility degrades rapidly.
SUMMARY
The present invention is for a powder generator
requiring no heat source to emit a "contrail"
with
sufficient visibility to aid in visual
acquisition
of
an aircraft target vehicle and the like. The
term
"contrail" was adopted for convenience in
identifying
the visible powder trail of this invention.
Aircraft target vehicles are used to simulate
aerial
threats for missile tests and often fly at
altitudes
between 5,000 and 20,000 feet at speeds of 300
and
400
knots or more. The present invention is also
suitable
for use in other aircraft vehicles to generate
contrails or reflective screens for any desired
purpose.
The powder contail generator is normally carried
on
an
aircraft in a pod containing a ram air tube and
powder
feed hopper. Powder particles, surface treated
to
minimize interparticle cohesive forces are fed
from
the hopper to a deagglomerator and then to the
ram
air
tube for dispensing as separate single particles
to
produce a contrail having maximum visibility for
a
given weight material.
Other object, advantages and novel features of
the
invention will become apparent from the
following
detailed description of the invention when
considered
in conjunction with the accompanying drawing.
Drawing Descriptions:
DESCRIPTION OF DRAWING
FIG. 1 is a schematic sectional side-view of a
powder
contrail generator of the present invention.
Description of Preferred Embodiments:
DESCRIPTION OF PREFERRED EMBODIMENT
The powder contail generator in pod 10, shown in
FIG.
1, is provided with a powder feed hopper 12
positioned
in the center section of the pod and which feeds
a
powder 13 to a deagglomerator 14 by means of
screw
conveyors 16 across the bottom of the hopper.
The
deagglomerator 14 produces two stages of action.
In
the first stage of deagglomeration, a shaft 18
having
projecting radial rods 19 in compartment 20 is
rotated
by an air motor 21, or other suitable drive
means.
The
shaft 18 is rotated at about 10,000 rpm, for
example.
As powder 13 descends through the first stage
compartment 20 of the
deagglomeration chamber, the hammering action of
rotating rods 19 serves to aerate and
precondition
the
powder before the second stage of
deagglomeration
takes place in the jet mill section 22. In the
jet
mill 22, a plurality of radial jets 24 (e.g.,
six
0.050 inch diamter radial jets) direct nitrogen
gas
(at e.g., 120 psig) inward to provide energy for
further deagglomeration of the powder. The N2,
or
other suitable gas, is provided from storage
tanks
25
and 26, for example, in the pod.
The jet mill 22 operates in a similar manner to
commercial fluid energy mills except that there
is
no
provision for recirculation of oversize
particles.
Tests with the deagglomerator show that at a
feed
rate
of approximately 11/2 lb/min, treated titanium
dioxide
powder pigment is effectively dispersed as
single
particles with very few agglomerates evident.
The nitrogen gas stored in cylinder tanks 25 and
26
is
charged to 1800
psig, for example. Two stages of pressure
reduction,
for example, by
pressure reduction valves 28 and 29, bring the
final
delivery pressure at the radial jets 24 and to
the
air
motor 21 to approximately 120 psig. A solenoid
valve
30 on the 120 psig line is connected in parallel
with
the electric motor 32 which operates the powder
feeder
screws 16 for simultaneous starting and running
of
the
powder feed, the air motor and the jet mill
deagglomerator.
Air enters ram air tube 34 at its entrance 35
and
the
exhaust from the
jet mill deagglomerator passes directly into the
ram
air tube. At the
deagglomerator exhaust 36 into ram air tube 34,
an
upstream deflector baffle 38 produces a venturi
effect
which minimizes back pressure on the powder feed
system. The powder is then jetted from the
exhaust
end
40 of the ram air tube to produce a contrail. A
pressure equalization tube, not shown, can be
used
to
connect the top of the closed hopper 12 to the
deagglomeration chamber 14.
A butterfly valve could be provided at the
powder
hopper outlet 39 to
completely isolate and seal off the powder
supply
when
not in use. Powder 13 could then be stored in
hopper
12 for several weeks, without danger of picking
up
excessive moisture, and still be adequately
dispensed.
Preparation of the light scatter powder 13 is of
a
critical importance
to production of a powder "contrail" having
maximum
visibility for a given weight of material. It is
essential that the pigment powder particles be
dispensed as separate single particles rather
than
as
agglomerates of two or more particles. The
powder
treatment produces the most easily dispersed
powder
through the use of surface treatments which
minimize
interparticle cohesive forces.
Titanium dioxide pigment was selected as the
primary
light scattering
material because of its highly efficient light
scattering ability and
commercially available pigment grades. Titanium
dioxide pigment (e.g.,
DuPont R--931) with a median particle size of
about
0.3µ has a high bulk density and is not readily
aerosolizable as a submicron cloud without the
consumption of a large amount of deagglomeration
energy.
In order to reduce the energy requirement for
deagglomeration, the TiO2 powder is specially
treated
with a hydrophobic colloidal silica which coats
and
separates the individual TiO2 pigment particles.
The
extremely fine particulate nature (0.007µ
primary
particle size) of Cobot S--101 Silanox grade,
for
example, of colloidal silica minimizes the
amount
needed to coat and separate the TiO2 particles,
and the hydrophobic surface minimizes the
affinity
of
the powder for
absorbtion of moisture from the atmosphere.
Adsorbed
moisture in powders causes liquid bridges at
interparticle contacts and it then becomes
necessary
to overcome the adsorbed-liquid surface tension
forces
as well as the weaker Van der Waals' forces
before
the
particles can be separated.
The Silanox treated titanium dioxide pigment is
further protected from the deleterious effects
of
adsorbed moisture by incorporation of silica
gel.
The silica gel preferentially adsorbs water
vapor
that
the powder may be exposed to after drying and
before
use. The silica gel used is a powder product,
such
as
Syloid 65 from the W. R Grace and Co., Davison
Chemical Division, and has an average particle
size
about 4.5µ and a large capacity for moisture at
low
humidities.
A typical powder composition used is shown in
Table
1.
This formulation was blended intimately with a
Patterson-Kelley Co. twin shell dry LB-model
LB--2161
with intensifier. Batches of 1500 g were blended
for
15 min. each and packaged in 5-lb cans. The bulk
density of the blended powder is 0.22 g/cc.
Since
deagglomeration is facilitated by having the
powder
bone dry,
the powder should be predried before sealing the
cans.
In view of long periods (e.g., about 4 months)
between
powder preparation and use it is found
preferable
to
spread the powder in a thin layer in an open
container
and place in a 400°F over two days before
planned
usage. The powder is removed and placed in the
hopper
about 2 hours before use.
Table 1______________________________________
CONTRAIL POWDER
FORMULATIONIngredient % by
Weight______________________________________TiO2
(e.g., DuPont R-931) 85 median particle size
0.3µColloidal Silica (e.g.,
Cabot S-101 Silanox) 10 primary particle size
0.007µSilica gel (e.g., Syloid
65) 5 average particle size
4.5µ______________________________________
Other type powder compositions can also be used
with
the apparatus
described herein. For example, various powder
particles which reflect
electromagnetic radiation can be dispensed as a
chaff
or the like from the contrail generator.
Obviously many modifications and variations of
the
present invention are possible in the light of
the
above teachings. It is therefore to be
understood
that
within the scope of the appended claims the
invention
may be practiced otherwise than as specifically
described.
Foreign References: Publication Country Date IPC
Class
GB01022621 United Kingdom 3 /1966
*COPYRIGHT NOTICE** In accordance with Title 17
U.
S.
C. Section 107,
any copyrighted work in this message is
distributed
under fair use
without profit or payment to those who have
expressed
a prior interest
in receiving the included information for
nonprofit
research and educational purposes only.
[Ref.
http://www.law.cornell.edu/uscode/17/107.shtml
]
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