U.S. patent application number 10/264128 was filed with the patent office on 2004-04-08 for turbofan engine internal anti-ice device.
This patent application is currently assigned to General Electric Company. Invention is credited to Holm, Raymond G., Wadia, Aspi R..
Application Number | 20040065092 10/264128 |
Document ID | / |
Family ID | 31993578 |
Filed Date | 2004-04-08 |
United States Patent
Application |
20040065092 |
Kind Code |
A1 |
Wadia, Aspi R. ; et
al. |
April 8, 2004 |
TURBOFAN ENGINE INTERNAL ANTI-ICE DEVICE
Abstract
A system and method are provided for preventing the formation of
ice on or removing ice from an internal surface of a turbofan
engine. A splitter region, associated with a booster compressor of
the turbofan engine, is identified. The splitter region has
surfaces internal to the turbofan engine subject to inlet icing
conditions. A resin is molded along a leading edge of the splitter
region, and electric coils are installed within the resin to
prevent ice build-up on the splitter region or to remove ice from
the splitter region during icing conditions.
Inventors: |
Wadia, Aspi R.; (Loveland,
OH) ; Holm, Raymond G.; (Lebanon, OH) |
Correspondence
Address: |
Barbara Joan Haushalter
Law Office
228 Bent Pines Court
Bellefontaine
OH
43311
US
|
Assignee: |
General Electric Company
|
Family ID: |
31993578 |
Appl. No.: |
10/264128 |
Filed: |
October 3, 2002 |
Current U.S.
Class: |
60/778 ;
60/39.093 |
Current CPC
Class: |
F01D 25/02 20130101;
Y02T 50/60 20130101; Y02T 50/672 20130101; F02C 7/047 20130101;
Y10T 29/49401 20150115 |
Class at
Publication: |
060/778 ;
060/039.093 |
International
Class: |
F02C 007/047 |
Claims
What is claimed is:
1. A system for preventing the formation of ice on or removing ice
from an internal surface of a turbofan engine, comprising: a
splitter region associated with a booster compressor of the
turbofan engine, the splitter region having surfaces internal to
the turbofan engine subject to inlet icing conditions; a resin
molded along a leading edge of the splitter region; and a heating
means installed within the resin to prevent ice build-up on the
splitter region or to remove ice from the splitter region during
icing conditions.
2. A system as claimed in claim 1 wherein the heating means
comprises a plurality of electric coils.
3. A system as claimed in claim 2 wherein the plurality of electric
coils are placed to approximately follow a configuration of the
splitter region.
4. A system as claimed in claim 1 wherein the heating means can be
developed from a stamped sheet of resistance alloy profiled to
provide controlled area heating.
5. A system as claimed in claim 1 wherein the heating means is
sandwiched in molded rubber.
6. A system as claimed in claim 1 wherein the heating means
provides continuous heating at controlled temperatures.
7. A system as claimed in claim 1 wherein the heating means
provides intermittent heating at controlled temperatures.
8. A system as claimed in claim 1 wherein the heating means is
powered by an auxiliary power unit.
9. A system as claimed in claim 1 wherein the resin comprises a
high temperature epoxy resin.
10. A system as claimed in claim 1 wherein the resin is molded
using hand-lay-up techniques in clean room conditions followed by
autoclave curing.
11. A system as claimed in claim 10 wherein the lay-up can include
ceramic fibers for fire barrier capability.
12. A system as claimed in claim 1 wherein the resin comprises a
resin impregnated fabric.
13. A method of preventing formation of ice on or removing ice from
an internal surface of a turbofan engine, comprising the steps of:
identifying a splitter region associated with a booster compressor
of the turbofan engine, the splitter region having surfaces
internal to the turbofan engine subject to inlet icing conditions;
molding a resin along a leading edge of the splitter region; and
installing a heating means within the resin to prevent ice build-up
on the splitter region or to remove ice from the splitter region
during icing conditions.
14. A method as claimed in claim 13 wherein the step of installing
heating means comprises the step of installing a plurality of
electric coils.
15. A method as claimed in claim 14 wherein the step of installing
a plurality of electric coils further comprises the step of placing
the plurality of electric coils to approximately follow a
configuration of the splitter region.
16. A method as claimed in claim 13 wherein the heating means
provides continuous heating at controlled temperatures.
17. A method as claimed in claim 13 wherein the heating means
provides intermittent heating at controlled temperatures.
18. A method as claimed in claim 13 wherein the heating means is
powered by an auxiliary power unit.
19. A method as claimed in claim 13 wherein the resin comprises a
high temperature epoxy resin.
20. A method as claimed in claim 13 wherein the step of molding a
resin further comprises the step of molding the resin using
hand-lay-up techniques in clean room conditions followed by
autoclave curing.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to gas turbine engines, and,
more specifically, to the deicing therein.
[0002] During flight and/or while grounded, aircraft may encounter
atmospheric conditions that cause the formation of ice on airfoils
and other surfaces of the aircraft. If accumulating ice is not
removed, it can change the aerodynamic profiles of the components
being iced, adversely affecting the aerodynamic performance of the
engine. Hence, aircraft engines are required to demonstrate the
ability to operate in an icing environment to show compliance with
Federal Aviation Administration requirements.
[0003] Ice accumulation has conventionally been accommodated by
configuring affected compressor airfoils with an increase in
ruggedness to avoid or minimize problems caused by ice liberation.
Commercial engines have been able to alleviate operability issues
caused by ice accumulation by raising flight idle or ground idle
speeds without violating thrust constraints. However, as technology
drives commercial engines to achieve higher and higher bypass
ratios, some of the operability issues are becoming more severe
than encountered in the past, since more engine airflow will
correspondingly increase the amount of ice accumulation which must
be accommodated.
[0004] Furthermore, ever larger fan blades that operate at slower
rotational speeds are being designed with state of the art
composite materials. Slow fan speeds can permit more accumulation
of ice in certain icing conditions.
[0005] One way of reducing the ice accumulation on booster airfoils
is to provide heat to the inlet guide vanes (IGVs), as is disclosed
in commonly assigned, co-pending U.S. application Ser. No.
09/932595. Hot air from the high pressure compressor could be
allowed to flow through hollow IGVs. However, hollow IGVs tend to
have an increased thickness. While the anti-ice system of such a
configuration works well, there can be some performance loss with
the thicker, hollow IGVs.
[0006] An alternative to circulating air through the inlet guide
vanes is to use compressor bleed air channeled through the manifold
and out the splitter nose for de-icing, as was also disclosed in
commonly assigned, co-pending U.S. application Ser. No. 09/932595.
However, the amount of bleed compressor air used to de-ice the
booster splitter leading edge is considered to be a heretofore
necessary performance loss to the engine cycle. This loss is a
result of the work done to the ambient air by the compressor to
pressurize it and thereby melt ice off the splitter nose, which
work is not then used by the turbomachinery components to produce
thrust.
[0007] It would be desirable, therefore, to provide an anti-icing
technique that effectively reduces ice threat to aircraft without
increasing aerodynamic total pressure losses due to the increased
thickness of hollow IGVs.
BRIEF SUMMARY OF THE INVENTION
[0008] The present invention reduces ice threat to the internal
surfaces of aircraft engines, eliminating both the need for hollow
inlet guide vanes and/or the use of an internal heavy and complex
piping system to deice the booster splitter leading edge surfaces.
The present invention has the additional advantage of eliminating
the need to use compressor air, with the associated performance
penalty of such air use, and bulky valves with their added system
weight. The present invention uses electric coils meshed into the
booster splitter lip near the leading edge in a conventional
turbofan engine, to reduce ice accumulation on surfaces internal to
the engine.
[0009] Accordingly, the present invention provides a system and
method for preventing the formation of ice on or removing ice from
an internal surface of an aircraft engine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The invention, in accordance with preferred and exemplary
embodiments, together with further objects and advantages thereof,
is more particularly described in the following detailed
description taken in conjunction with the accompanying drawings in
which:
[0011] FIG. 1 is an axial sectional view through a portion of a
high bypass turbofan gas turbine engine for powering an aircraft in
flight;
[0012] FIG. 2 is an enlarged, axial sectional view through the
splitter between the booster compressor and fan bypass duct
illustrated in FIG. 1, showing heating coils wrapped around the
splitter nose as the deicer system according to the present
invention; and
[0013] FIG. 3 is an enlarged portion of the splitter nose
illustrated in FIG. 2, showing the heating coils wrapped around the
splitter nose.
DETAILED DESCRIPTION OF THE INVENTION
[0014] Referring to FIG. 1, there is illustrated a portion of a
high bypass turbofan gas turbine engine 10 configured for powering
an aircraft (not shown) in flight from takeoff, cruise at altitude,
descent, and landing, within a corresponding flight envelope of
operation. The engine is axisymmetrical about a longitudinal or
axial centerline axis 12 and includes an inlet at its forward end
for receiving ambient air 14. The ambient air 14 first engages a
row of fan rotor blades 16. Air discharged from the fan blades is
split concentrically by an annular splitter nose 18 for separate
flow through an annular bypass duct 20 surrounding the splitter,
and low pressure or booster compressor 22 disposed inside the
splitter.
[0015] The basic engine configuration illustrated in FIG. 1 is
conventional, and but for the present invention, has been used in
commercial service in this country for many years. The bypass duct
20 is surrounded by a conventional nacelle, shown in part, and
supported by rows of struts and bypass outlet guide vanes.
[0016] In an exemplary embodiment, a heating means such as electric
heaters 22 can be used in place of bleed compressor anti-ice air 48
as the deicer for surfaces internal to the turbofan engine.
Specifically, electric coils 24 are proposed to avoid ice buildup
in the splitter surfaces. The electric coils can be installed
within a resin 26 that is molded essentially into the shape of the
leading edge of the splitter.
[0017] The booster compressor 28 includes a row of inlet guide
vanes (IGVs) 30 which, in conventional configurations, first
receive the inner portion of the air discharged from the fan blades
for entry in the compressor. With the configuration of the present
invention, the need for hollow and, therefore, thicker IGVs as well
as the use of compressor air to melt the ice from the IGV surface
or the booster splitter leading edge is eliminated, and electric
heaters are used to avoid ice buildup on the splitter surfaces
without a consequent aerodynamic performance penalty.
[0018] FIG. 2 illustrates in more particularity a portion of the
booster compressor at the splitter nose 18. A splitter shell 34 is
integrally formed with the splitter nose 18 in a unitary member
which defines the cooperating shroud 32 and annular manifold 36.
The IGVs 30 are preferably fixedly mounted to and supported from
the surrounding annular shroud 32, which vanes are not adjustable
in this exemplary embodiment. The radially inner ends of the row of
IGVs are suitably mounted in an inner band, as shown in FIG. 1. The
electric coils 24 are placed to essentially follow the
configuration of the splitter, to melt any ice formations on the
splitter. The channeling of the hot air can be through a controller
60, with a valve 46 for bleeding the hot air 48 to the splitter
region.
[0019] The splitter nose 18 and leading edges of the IGVs 30 are
subject to icing from moisture carried with the fan air 14 during
certain icing conditions in the flight envelope. Typically, icing
conditions occur at altitudes below 24,000 feet with air
temperature below freezing. In such operating conditions, ice may
form and accumulate on the splitter nose and IGVs, but for the
introduction of the present invention.
[0020] More specifically, an anti-icing system and method is
introduced into the splitter region of the booster compressor for
reducing, eliminating, or preventing the accumulation or formation
of ice during icing conditions within the flight envelope of the
engine. As shown in FIGS. 2 and 3, a resin 26 is molded along the
defined leading edge of the splitter nose 18. In a typical
embodiment, the booster splitter lip is three-dimensional with
compound curved surfaces to meet aerodynamic requirements. In
accordance with a preferred embodiment of the present invention, a
commercially available high temperature epoxy resin hybrid
enforcement system with a non-metallic honeycomb is used. Molding
is via conventional hand-lay-up techniques in clean room
conditions, followed by autoclave curing. The resin filler/hardener
system, which is developed from commercially available materials,
produces high temperature operational properties. Resin impregnated
fabric, commonly known as prepreg, is commercially manufactured
using a special solventless process which provides complete control
of resin formulation, prepreg manufacture, and storage management.
Ceramic fibers in the lay-up can provide the ability to meet fire
barrier requirements. Hence, the resin is capable of withstanding
the necessary heat generated by the electric coils.
[0021] In the event of malfunction of the control valve 46, the hot
bleed air will not damage the splitter assembly, as the splitter
shell and nose may be formed of a suitable metal for withstanding
the intended temperature of the hot bleed air. The typical acoustic
liner or skin 62 disposed aft from the splitter shell 34 is
protected from the hot temperature of the bleed air by physical
separation therefrom.
[0022] Electric coils 24 are installed within the resin 26 to
prevent ice buildup on the splitter. The electric heater can be
developed from a stamped sheet of resistance alloy profiled to
provide controlled area heating. A sandwich, with molded rubber on
each side, protects the heating element and ensures bonding to the
metal splitter lip. The integrated ice protection system
incorporates electronic control and composite structures with
integral heaters. The anti-icing system provides continuous heating
at a controlled temperature, which prevents ice formation,
particularly at the splitter lip susceptible to ice formation from
engine ice ingestion. The heater elements are powered by the
aircraft's auxiliary power unit. The melted ice flows through the
booster as liquid water or steam, depending on the temperature of
the engine. The coils 24 can be controlled to provide either
continuous heating for anti-icing or intermittent heating for
de-icing at controlled temperatures to the splitter nose region 18.
The temperature range provided by the heating coils varies and is
dependent on the inlet airflow and the engine bypass ratio. Icing
severity will vary with airspeed and inlet temperature, so the
controlled temperature of the electric coils 24 can vary between 15
and 150 degrees Fahrenheit to provide the necessary anti-icing or
de-icing capability, in accordance with the present invention.
[0023] A particular advantage of this anti-icing and deicing system
and method is that the IGVs 30 may remain aerodynamically thin and
solid, without the need for channeling hot bleed air radially
therethrough. Hence, maximum aerodynamic efficiency of the IGVs 24
may be obtained by optimizing their aerodynamic configuration,
which typically requires a relatively thin profile or thickness.
The thin profile of the IGVs is not possible if internal passages
are provided within the IGVs for anti-icing purposes. In addition,
no bleed compressor air is required to melt ice off the booster
splitter or IGV surfaces, enhancing performance of the engine.
[0024] While the invention has been described with reference to
preferred and exemplary embodiments, it will be understood by those
skilled in the art that various changes may be made and equivalents
may be substituted for elements thereof without departing from the
scope of the invention. Therefore, it is intended that the
invention not be limited to the particular embodiment disclosed as
the best mode contemplated for carrying out this invention, but
that the invention desired to be secured will include all
embodiments and modifications as fall within the true spirit and
scope of the appended claims.
* * * * *