Side discharge anti-ice manifold

An improved anti-ice manifold for a gas turbine engine is formed as a separate toroidal manifold arranged to be mounted forward of the inlet guide vanes. Axial discharge holes connect the manifold to interior passages in the inlet guide vanes for conveying heated gas thereto. An integral static pressure duct may also be provided in the manifold.

BACKGROUND OF THE INVENTION 
This invention relates to gas turbine engines, and particularly to an 
improved anti-ice manifold for conducting heated gas to the inlet guide 
vanes of a gas turbine aircraft engine. 
In a gas turbine engine inlet guide vanes are typically arranged near the 
engine intake between the first and second peripheral engine flanges 
inward of the forward engine mounting lugs. An inlet seal guide, which 
peripherally seals the forward end of the engine to cooperating duct seals 
in the engine nacelle, is typically provided forward of the inlet guide 
vanes. To provide anti-ice function the inlet guide vanes may have a 
hollow interior into which heated engine gas is ducted. Typically a 
manifold is provided radially outward from the inlet guide vanes in the 
space between the first and second peripheral engine flanges. This 
manifold may be formed by providing a cap which bridges the two flanges 
This known approach requires considerable hand welding, particularly in 
the region of the engine mount lugs, service and instrumentation bosses. 
Further, since the manifold bridges the flanges, threaded inserts must be 
used in the flanges, increasing required flange thickness and weight. 
It is therefore an object of the present invention to provide an improved 
anti-ice manifold arrangement that is easily fabricated and assembled to 
the engine without extensive hand welding. 
It is a further object of the invention to provide an improved anti-ice 
manifold arrangement with an integrally formed duct for conveying engine 
gas pressure to engine control sensors. 
SUMMARY OF THE INVENTION 
In accordance with the invention there is provided an improved anti-ice 
manifold for a gas turbine engine for conducting heated gas to inlet guide 
vanes. The invention comprises a hollow toroidal manifold arranged for 
axial mounting to the engine, forward of the inlet guide vanes. The 
manifold has a forward end with a tapered cross-section for being received 
in a forward duct seal on an engine nacelle and has rearwardly facing 
openings for conducting heated gas to the inlet guide vanes. 
According to a preferred embodiment the manifold further includes a 
toroidal duct formed integrally with and isolated from the manifold and 
having radially inner openings for conveying engine gas pressures to the 
duct. The manifold is advantageously fabricated from substantially 
circular pieces of sheet metal which are joined with circular, automated 
machine welds (electron beam, TiG, or other). 
For a better understanding of the present invention, together with other 
and further objects, reference is made to the following description, taken 
in conjunction with the accompanying drawings, and its scope will be 
pointed out in the appended claims.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows the front view of the forward, air-intake end of a gas turbine 
engine. The exemplary engine illustrated is an engine for a high 
performance military aircraft. FIGS. 2, 3 and 5 are modified 
cross-sectional views of the FIG. 1 engine intake section taken along 
corresponding lines illustrated in FIG. 1. The term modified cross-section 
as used herein refers to a simplified cross-sectional view illustrating 
only the structure immediately adjacent the cross-section, and not 
illustrating background structures that would normally be visible in a 
cross-sectional view. 
The FIG. 1 engine includes a generally cylindrical peripheral housing 12 
and a plurality of inlet guide vanes 14 which extend radially across the 
engine intake. The inlet guide vanes are typically hollow to provide 
internal passages 20 to which a supply of heated gas may be provided to 
prevent engine icing that might otherwise occur when the engine is 
operating at low ambient temperatures, for example, at high altitude. 
Conventional engines of this type include an anti-ice manifold which 
radially surrounds the inlet guide vanes 14 and provides heated gases to 
the interior passages 20 of the inlet guide vanes through radially outer 
openings on the vanes. In one known arrangement wherein the inlet guide 
vane section of the engine has immediately adjacent flanges toward the 
forward and aft ends of the peripheral housing section surrounding the 
guide vanes, the manifold can be formed by providing a cap which bridges 
the two flanges of the guide vane section and forms a manifold between the 
flanges which communicates with the interior passages of the vanes through 
the openings in the radially outer ends of the vanes. As previously noted, 
installation of a cap in this configuration requires extensive hand 
welding. 
In accordance with the invention, and as illustrated in detail in FIGS. 2 
to 5, the anti-ice manifold 16 of the present invention is formed as an 
integral, separate unit from the inlet guide vane peripheral housing and 
is mounted forward of the inlet guide vanes with rearwardly extending 
openings 18 connecting the manifold 16 to the interior passages 20 of the 
inlet guide vanes. Accordingly, manifold 16 is separately fabricated and 
joined to the peripheral housing surrounding the inlet guide vanes by a 
junction 22, and bolted thereto by a forward guide vane flange 24. The 
guide vane housing is separately connected to the rearwardly adjacent 
housing by rear guide vane flange 26. 
In addition to functioning as an anti-ice manifold, structure 16 
additionally provides an inlet extension duct/seal guide by having a 
tapered forward cross-section 30 that mates with inlet seal member 28 of 
the engine nacelle. Structure 16 is toroidal and substantially uniform in 
cross-section, having a cylindrical outer wall 32, a cylindrical inner 
wall 34 and a planar rear wall 36 in addition to the tapered forward 
section 30. The closed toroidal manifold is provided with heated air which 
is conveyed by rearwardly facing openings 18 to the interior passage 20 of 
inlet guide vanes 14. 
The substantially uniform toroidal structure of manifold 16 makes the 
structure relatively easy to fabricate as a separate unit. The various 
walls of the unit can be separately formed as circular pieces then welded 
together by circular automated machine welds. Possible weld joint 
positions are indicated by numeral 40 in FIG. 3. 
In addition to providing an anti-ice manifold, the structure 16 can be 
provided with an integral duct 38 for conveying the static pressure to 
sensors for engine control functions. Radially inward passages 42, as 
shown in FIG. 5, may be provided for sensing intake pressure at various 
circumferential points. FIG. 5 additionally shows the arrangement of the 
engine mounting lugs 44, which are isolated from the heated gas in 
manifold 16 and accordingly subject to reduced temperature stress. 
FIG. 4 is a modified cross sectional view taken as shown in FIG. 2 and 
showing an end cap 46 on inlet guide vane 14 sealing the normally open 
radially outer end thereof. FIG. 4 also shows the discharge hole 18 which 
can be varied in size from strut to strut to better control the 
distribution of heated gas as required for strut heating while minimizing 
bleed air requirements. Guide vanes which are at circumferential locations 
of manifold 16 closer to the heated gas supply would have smaller passages 
18 than those at other circumferential locations. 
The manifold 16 according to the invention functions as anti-ice manifold, 
inlet static pressure duct and inlet extension duct/seal guide. It is 
easily formed as a separate part reducing the need for manual welding of a 
cap to flanges 24 and 26 to form a conventional manifold. The structure 
can be easily removed from the engine by flange 24 for replacement and/or 
servicing. The assembly 16 with its circular symmetry is fabricated from 
circular parts by simple circular automated machine welds. 
While there has been described what is believed to be the preferred 
embodiment of the invention, those skilled in the art will recognize that 
other changes and modifications can be made thereto without departing from 
the spirit of the invention and it is intended to claim all such changes 
and modifications as fall within the true scope of the invention.