Split exhaust jet blast deflector fence

A jet blast deflector fence comprising two curved corrugated deflecting surfaces separated from each other in a common structural framework that is fastened to a concrete foundation, with the taller front deflecting surface open at the bottom to permit the high speed jet exhaust ground layer component to split off and pass through the opening to impinge upon the shorter rear deflecting surface which deflects that component vertically upward to hug the convex rear surface of the front deflector, while the upper slower moving component of the jet blast is guided upwardly by the concave surface of the front deflecting surface such that the two split layers come together in a substantially vertical direction at the discharge edge of the taller deflecting surface to form a vertical air curtain which aerodynamically increases the effective height of the blast deflector.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to jet blast deflection fences for upwardly 
deflecting the blasts of various types of jet and turbo prop aircraft and 
more particularly the present invention pertains to a new and improved 
fence which splits or divides the jet blast into higher velocity 
components that move close to the airport surface and upper components of 
lower velocity, the higher velocity components moving at more than twice 
the speed of the upper remaining components to form a barrier or wall that 
guides the remaining components of the blast upward, thereby increasing 
the ability or capacity of the jet blast deflector fence to handle the 
tremendously increased volume of gases from the new super-thrust engines 
such as the GE-90 for the Boeing 777, which produces a blast of 100,000 
pounds or more jet blast deflector, which is necessary to protect 
personnel, other aircraft, and other property at military and public 
airports from the horizontal jet blast which is composed of hot gases and 
particles of debris which have been accelerated to high velocities. 
2. Description of the Prior Art 
Early blast fences were fairly simple in structure and usually no more than 
eight (8) feet in height. As larger aircraft with greater thrust appeared, 
taller fences with more complex supporting structures were required. For 
example, blast deflector systems for the Douglas DC-10 and MD-11 aircraft 
for takeoff power engine runup and testing have now reached thirty-five 
(35) feet in height. At least two newer and larger jet transports are now 
undergoing development. The Boeing 777 and the Airbus 610 will be making 
their appearance at the world's airports in the next few years. These new 
aircraft will produce greater thrust (more than 100,000 pounds thrust per 
engine) than aircraft presently in use and will require larger jet blast 
deflectors to deflect a greater mass of hot, high velocity jet exhaust. 
Note that thrust is the product of mass of gas times velocity (T=MV) so to 
obtain 100,000 pound thrust requires twice the volume of exhaust gas as 
compared with a 50,000 pound thrust # T engine for equal velocities. 
Larger, stronger, and more expensive blast fences are required to handle 
this doubled volume. 
With the increase in height of jet blast deflectors there has been an 
attendant increase in the width of support structure and also increased 
use of expensive airport apron space to support the deflector fences. 
There has also been an increase in cost of blast deflectors as the 
deflectors are increased in height. The average and most used height of 
deflector fences is currently fourteen (14) feet as opposed to the eight 
(8) foot height of fences that were required for the Boeing B-52 
twenty-five to thirty years ago. As the Boeing 777 and Airbus 610 are 
introduced the average height of fences will increase to possibly 
twenty-one (21) to thirty (30) feet. And with the increases in height more 
valuable airport apron space will be committed to use for blast fence 
structure and support. 
The improvements embodied in the present invention address and alleviate 
the problems created by newer jet aircraft such as the Boeing 747, 767, 
777, and Airbus 610 and particularly the Douglas MD-11 the Number 2 
engine of which is already 32 feet above the pavement, which have higher 
trust engines that produce larger volumes of hot, high velocity gas. The 
MD-11 may require a fence 50 feet in height. 
The present invention presents a shorter, less costly blast fence that has 
the effective blast deflector capability of larger blast fences. Coupled 
with the reduction in size of the blast deflector fence of the present 
invention is a reduction in the cost of structure and airport apron space 
necessary to support the fence. 
While the inventor knows of no prior art patents which incorporate the 
theory and effect of the present invention, prior blast deflectors have 
included two or more separate blast deflection surfaces in the same fence. 
Most notably the jet blast deflecting fence described in the U.S. Pat. No. 
4,471,924 issued to B. S. Lynn, Sep. 18, 1994 includes two (2) blast 
deflection surfaces separated by a slot. That Patent does not teach any of 
the objects of the present invention. 
SUMMARY OF THE INVENTION 
The general purpose of the present invention in its preferred embodiment 
which will be described subsequently in greater detail, is to provide a 
new and improved jet blast deflector fence which is composed of two (2) 
curved deflectors, a front, taller deflector surface, and a rear, shorter 
deflector surface. Both of the deflector surfaces are supported by the 
same support structure. The front deflector surface includes an opening 
between the surface of the apron and the leading edge of the deflector 
surface that is approximately one-quarter of the height of that deflector 
surface. The opening allows passage of and separates the highest velocity 
component of the jet blast and directs it to the concave forward surface 
of the rear deflector, the leading edge of which is at ground level. The 
concave rear surface guides the higher velocity components of the jet 
blast from a horizontal to a vertical direction. The higher velocity 
components then move into contact with the convex rear surface of the 
taller deflector. By means of the Coanda effect the higher velocity 
components of the jet blast follow the rear surface to the trailing edge 
of that surface. At that point the higher velocity components combine to 
accelerate lower velocity elements of the blast that have been deflected 
by the front deflector surface and forms a barrier to other slower moving 
components of the blast. 
To obtain these advantages, the present invention requires a simple 
supporting structure composed of a series of support frames, that are each 
comprised of a first or front curved support member or rib, a second or 
rear curved support member or rib, and an upright support member. A series 
of corrugated panels are bolted to the face of the series of first curved 
support members starting at approximately one-quarter of the height of the 
first ribs to form a continuous first blast deflecting surface. The 
leading edge of the panels define an opening with the surface of the 
apron. And similarly a series of corrugated panels is bolted to the curved 
face of the second series of curved support members or ribs to form a 
second continuous deflection surface. The leading edge of the second 
surface commences at the surface of the apron. The first and second 
deflecting surfaces combine to form a confined channel which separates the 
highest velocity component of the blast which is lower to the ground, 
guides it through the channel and redirects it along the backside of the 
front or first deflecting surface. The high velocity components combine at 
the trailing edge of the first deflecting surface with slower components 
that have been deflected by the first surface, impart an acceleration to 
the slower components and further combine to create a barrier or wall of 
higher velocity air which prohibits passage by the remaining components of 
the blast. 
There has thus been outlined rather broadly, the important features of the 
present invention in order that the detailed description thereof that 
follows may be better understood, and in order that the present 
contributions may be better appreciated. There are, of course, additional 
features of the invention that will be described hereinafter plus other 
embodiments all of which will form the subject matter of the claims 
appended hereto. Those skilled in the art will appreciate that the 
concept, upon which this disclosure is based, may readily be utilized as a 
basis for designing of other structures for carrying out the several 
purposes of the present invention. It is important, therefore that the 
claims be regarded as including such equivalent construction so far as 
they do not depart from the spirit and scope of the present invention. 
As such it is an object of the present invention to provide a new and 
improved jet blast deflector fence which has all of the advantages of the 
prior art jet blast deflector fences and none of the disadvantages. 
It is another object of the present invention to provide a new and improved 
jet blast deflector fence which may be efficiently and easily manufactured 
and marketed, and installed, and the components of which are easily 
transported to the far corners of this world. 
It is a further object of the present invention to provide a new and 
improved jet blast deflector fence that may be simply efficiently, and 
reliably assembled. 
It is a still further object of the present invention to provide a new and 
improved jet blast deflector fence to split the jet blast into higher and 
lower velocity components and to utilize the higher velocity component as 
a barrier that is impervious to the lower velocity components. 
It is an additional object of the present invention to use the blast itself 
to assist in blast deflection, an effect which reduces the height and cost 
of the blast fence required to handle the tremendous exhaust gas volumes 
of the newest jumbo jet engines. 
Still another object of the present invention is to provide a new and 
improved jet blast deflector fence that is of durable and rugged 
construction yet which is less costly to construct than existing fences. 
Even another object of the present invention is to provide a new and 
improved means for modification of existing jet blast deflector fences 
that will allow existing fences to split the jet blast into several 
components in order to be utilized for newer and larger aircraft with the 
new super-engines now being developed, such as the new GE 90. 
Still yet another object of the present invention is to provide a new and 
improved jet blast deflector fence which uses less airport apron space 
resulting in the creation of more useable area on the overcrowded and very 
expensive aprons. 
And even yet another object of the present invention is to provide a new 
and improved jet blast deflector fence that eliminates the bounce back of 
the blast into the airplane, thus reducing possibility of Foreign Object 
Damage (F.O.D.) which can ruin the engines. 
An even further object of the present invention is to provide a new and 
improved jet blast deflector fence which provides in the apparatuses and 
methods of the prior art some of the advantages thereof while 
simultaneously overcoming some of the disadvantages normally associated 
therewith. 
These together with other objects of the invention, along with the various 
features of novelty which characterize the invention, are pointed out with 
particularity in the claims annexed to and forming a part of this 
disclosure. For a better understanding of the invention, its operating 
advantages and the specific objects attained by its uses, reference should 
be had to the accompanying drawings and descriptive matter in which there 
is illustrated preferred embodiments of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1 and 2, the elements of the split exhaust jet blast 
deflector fence 10 are well disclosed. In the preferred embodiment the 
split exhaust jet blast deflector fence is comprised of a series of spaced 
support frames or deflector support frames which are anchored to the 
concrete apron of an airport. (For high thrust large airplanes such as the 
B-777 or B-747, the support frames are spaced three (3) feet apart. For 
lesser thrust airplanes or for light "brakeaway" duty the support frames 
would be spaced as much as six (6) feet apart.) 
The support frames include a first concave curved front rib or channel or 
structural member 12 that is comprised for example of standard five (5) 
inch steel channel that has been rolled such that the outer edge of the 
channel flanges form the fore and aft edges of the curve. At its lower end 
the front rib or channel 12 is pivotally bolted to the vertical leg of a 
front anchor clip 14. The horizontal leg of the clip is bolted by means of 
two (2) spaced cap screws to Hilti anchors which are installed in drilled 
holes in the concrete of the airport apron. 
Near its upper end the rib or channel 12 is rigidly bolted to the upper end 
of an upright main strut or structural member 16. At its lower end the 
strut or post 16 is bolted to the vertical leg of a rear clip 18. The 
horizontal leg of the rear clip 18 is bolted to the apron by means of two 
(2) spaced cap screws that mate with Hilti expansion anchors that have 
been installed in drilled holes in the concrete apron. The strut 16 is 
comprised of angle iron. 
A second concave curved rib or channel or structural member 20 located to 
the rear of the rib 12 is pivotally secured at its lower end to a front 
clip 22. The horizontal leg of the clip 22 is bolted to the apron by means 
of spaced cap screws mated to Hilti anchors installed in drilled holes in 
the apron. Near its upper end the rib 20 is bolted to the strut 16. Angle 
iron cross braces 24 and 26 are added to the support frames when the Blast 
Deflector is used to deflect the blast from high thrust airplanes, such as 
the Boeing 747, the Boeing 777, or the MD-11. It is significant that the 
rear strut 16 is constrained from moving or bending either fore-and-aft or 
from side-to-side. This eliminates the need for additional external 
bracing. 
A first and forward deflector surface 28 is created by a series of 
galvanized corrugated metal sheets or corrugated deflector surface means 
that are bolted to the concave front surfaces of the ribs 12. The 
corrugated panels are approximately two (2) feet in width. With a fence of 
20 foot height that could be used to deflect the blast from a Boeing 777 
airplane the first of the series of corrugated panels would commence at an 
elevation of five (5) feet above the airport apron and continue with 
sheets butted in turn one to the next to cover the upper portion of the 
ribs 12. The sheets are bolted to the ribs by means of bolts and curved 
washers which mate with the curved surface of the valleys of the 
corrugated panels. With the commencement of the deflection surface at the 
five (5) foot elevation the lower edge or leading edge of the first panel, 
the apron and the ribs 12 define an opening below the deflection surface. 
A second or rear deflector surface or fence 30 is similarly created by a 
series of galvanized corrugated metal sheets or panels or corrugated 
deflector surface means that are bolted to the curved ribs or channels 20. 
The panels overlay the concave front faces of the ribs 20 from the lower 
ends of the ribs to the upper ends thereof. In the present embodiment the 
rear blast deflector is about seven plus (7+) feet in height. The leading 
edge of the rear deflector commences at the surface of the apron. 
Reference is now made to FIG. 3A which graphically displays the jet wake 
velocity contours of the engine thrust at takeoff setting (84,600 lbs.) 
for the Boeing 777 Airplane (B-777). Data from the graph is tabulated in 
the accompanying Chart (FIG. 3B). It can be seen by a review of FIGS. 3A 
and 3B that the layer of jet exhaust closest to the plane of intersection 
at ground level is moving at a much higher velocity than the upper portion 
of the blast envelope. It is the difference in velocities of the lower and 
upper components of the exhaust that is the essence of the novelty in the 
design of the present invention. It is the intent and ability of the 
present invention to split off the highest velocity component, designated 
herein and in FIG. 3B as V1. That component is traveling between the 
ground surface and five (5) foot elevation according to FIG. 3A and the 
chart of FIG. 3B. 
In operation the split exhaust jet blast deflector fence of the present 
invention would be utilized during run up or take off at a position 
approximately forty (40) feet behind the aircraft. The highest velocity 
component designated V1 will pass through the opening in the front fence 
and impinge upon the curved concave forward surface of the rear fence. The 
jet blast component V1 will be deflected by the corrugated curved surface 
of the rear fence from a horizontal course to a vertical direction. As the 
component V1 moves along the surface 30 it is guided slightly forward at 
the trailing edge of the surface 30 into contact with the rear convex 
surface of the front fence. The blast component V1 will then be guided 
along in contact with the rear convex surface of the front fence to a 
vertical direction by the Coanda effect, the phenomena according to which 
a stream of gas traveling at high speed will hug a convexly curved surface 
(the rear face of the front blast deflector) and will be guided thereby in 
the desired direction, vertically in this instance. 
The upper jet exhaust component which is designated V2 will for the most 
part impact the first or forward deflector surface and be directed 
upwardly. As the component V2 leaves the discharge or trailing edge of the 
front deflector surface it is contacted by the component V1, which imparts 
an upward acceleration to the component V2. The combined components V1 and 
V2 create an air curtain that is moving vertically. It is significant to 
note that the ratio V1/V2 for the B-777 Airplane is 2.27. The air curtain 
that is created is substantially impervious to the remainder of the blast 
envelope which is moving at significantly lower velocity (See FIG. 3A). 
FIG. 4 illustrates an alternate embodiment of the present invention. This 
embodiment effects similar results to those of the preferred embodiment 
with a variance in structure. The blast deflector of this embodiment 
includes a first or lower fence 50 that is comprised of a series of spaced 
support structures each of which include a curved rib 52 formed of steel 
channel that has been rolled to form a curve such that the outer edges of 
the channel flanges form the fore-and-aft edges of the curve. At its lower 
end the rib 52 is pivotally connected to the upright leg of a front anchor 
clip 56. The horizontal leg of the clip 56 is bolted to Hilti anchors 
which are installed in drilled holes in the concrete airport apron. The 
rib 52 is held rigidly in place by means of two (2) angle iron struts 58 
and 60 which are bolted at their upper ends to the rib 52. The struts 58 
and 60 are bolted at their lower ends to the upright leg of a rear clip 
62. The deflection surface is formed by a series of corrugated metal 
panels butted edge to edge which are bolted to the concave surface of the 
ribs. In this embodiment, wherein the blast fence is designed for higher 
thrust airplanes such as the B-747 or B-777, the upper end of the lower 
fence 50 is at an elevation of nine (9) feet above the payment. 
Interconnected to the upper end of the lower fence 50 is an upper fence 64. 
The upper fence 64 is comprised of a series of curved ribs or steel 
channel members 66 which are supported firstly by the upright angle iron 
strut 68 which is bolted at its upper end near the upper end of rib 66. 
The strut 68 is bolted at its lower end to the upright leg of the rear 
clip 62. The rib 66 is further supported by the cross brace 70 which is 
bolted at one end to the lower end of the rib or channel 66. The brace 70 
is further bolted to the upper end of the channel 66 and then at its other 
end to the strut 68. Further supporting the rib 68 are other cross-members 
72 and 74. Cross-member 72 is bolted at one end near the midpoint of rib 
66 and at its other end to the strut 68. Cross-member 74 is joined with 
cross-member 72 at the midpoint of the rib 66 and also to the brace 70 at 
the upper end of rib 52. 
The deflection surface of the upper fence is formed of a series of 
corrugated metal panels butted together and bolted to the ribs 66. The 
panels extend from the bottom of the ribs at an eight (8) foot elevation 
to the upper end of the ribs twenty-one (21) feet above the pavement. 
In use this embodiment of the blast deflection fence performs in similar 
fashion to the deflection fence of the preferred embodiment. The higher 
velocity component V1 of the blast is deflected from a horizontal heading 
to a vertical heading by the lower fence 50. As that component V1 of the 
blast leaves the trailing edge of the lower fence the component may be 
directed slightly forward against the rear surface of the fence 64. The 
Coanda effect which has been described previously herein causes the 
component to follow the rear of the fence 64 to a vertical heading. As the 
component V1 leaves the trailing edge of the fence 64 it mixes with and 
accelerates the slower moving component V2 of the blast and the two 
components thereby form a barrier to the slower moving components of the 
blast. 
With respect to the above description then, it is to be realized that the 
optimium dimensional relationships for the parts of the invention to 
include variations in size, materials, shape, configuration, form, 
function, and manner of operation, assembly and use, are deemed readily 
apparent and obvious to one skilled in the art, and all equivalent 
relationships to those illustrated in the drawings and described in the 
specification are intended to be encompassed by the present invention. 
Therefore, the foregoing is considered as illustrative only of the 
principle of the invention. Further, since numerous modifications and 
changes will readily occur to those skilled in the art, it is not desired 
to limit the invention to the exact construction and operation shown and 
described, and accordingly, all suitable modifications and equivalents may 
be resorted to falling within the scope of the invention.