MAIN PROPULSION ENGINE SYSTEM INTEGRATED WITH SECONDARY POWER UNIT

SYSTEME DE MOTEUR DE PROPULSION PRINCIPAL INTEGRE A UNE UNITE D'ALIMENTATION SECONDAIRE

English Abstract

A main engine (14) mounted auxiliary power unit (30) comprises an auxiliary
power unit (31) integrated with a primary gas turbine engine (14) into a
single power plant suited for aircraft applications. The auxiliary power unit
(30) can be mounted within an engine core compartment of the main engine or at
the main engine aft center body. The integration of the auxiliary power unit
(30) provides for installation and certification cost savings to the airframer
by eliminating the need for mounting an auxiliary power unit (30) to the tail
section of the aircraft.

French Abstract

L'invention concerne une unité d'alimentation auxiliaire montée dans un moteur principal, qui comporte une unité d'alimentation auxiliaire intégrée à un moteur à turbine à gaz primaire dans un groupe motopropulseur simple, conçue pour des applications aéronautiques. Cette unité d'alimentation auxiliaire peut être montée dans le compartiment central du moteur principal ou au niveau du corps central arrière du moteur central. L'intégration de cette unité d'alimentation auxiliaire permet au constructeur de cellules de réaliser des économies sur les prix d'installation et de certification, grâce à l'élimination du besoin de monter une unité d'alimentation auxiliaire dans la partie de queue de l'aéronef.

Claims

CLAIMS:
1. A power plant comprising:
a nacelle cowl having an inlet end and an exhaust nozzle
end;
a primary gas turbine engine mounted within said nacelle
cowl;
said primary gas turbine engine having a core compartment;
secondary power means for providing pneumatic air to at
least one load; and
said secondary power means being positioned within said
core compartment.
2. A power plant according to claim 1, further comprising:
an inner core cowl being concentrically mounted within said
nacelle cowl about the primary gas turbine engine; and
an annular by-pass passage extending between said nacelle
cowl and said inner core cowl.
3. A power plant according to claim 2, further comprising
said secondary power means having inlet means for drawing a
fluid from said by-pass passage into said secondary power means.
4. A power plant according to claim 3, wherein said inlet is
an axial inlet.
5. A power plant according to claim 3, wherein said inlet
means comprises a radial inlet plenum.
6. A power plant according to claim 5, wherein said radial
inlet plenum comprises a ring member defining a number of air
passages extending radially through the core compartment.
8

7. A power plant according to claim 3, further comprising said
secondary power means having outlet means for directing expanded
gases into said by-pass passage.
8. A power plant according to claim 3, further comprising a
closure member movable between a first position where fluid from
said by-pass passage is drawn into said inlet means and a second
position where fluid from said by-pass passage is prevented from
being drawn into said inlet means.
9. A power plant according to claim 1, wherein said primary
gas turbine engine has a compressor section, a combustion
section, and a turbine section.
10. A power plant according to claim 1, wherein said secondary
power means comprises an auxiliary power unit for providing
pneumatic air to said at least one load and electrical loads for
an aircraft.
11. A power plant according to claim 1, wherein said pneumatic
air from said auxiliary power unit is used to start said primary
gas turbine engine.
12. A power plant according to claim 1, wherein said secondary
power means comprises a gas turbine engine.
13. A power plant according to claim 1, wherein said secondary
power means comprises an auxiliary power unit having an
environmental control system.
14. A power plant according to claim 1, wherein said secondary
power means comprises a power unit which integrates an auxiliary
9

power unit, an energy power unit, an environmental control
system, and an engine start system.
15. A power plant according to claim 1, wherein said secondary
power means comprises means for heating said primary gas turbine
engine.
16. A power plant according to claim 1, further comprising said
secondary power means having an inlet for receiving air from
said core compartment.
17. A power plant according to claim 1, further comprising a
hollow member for allowing ambient air to be drawn into said
secondary power means.
18. A power plant according to claim 1, further comprising a
hollow member extending from an outlet end of said secondary
power means for directing expanded gas to an ambient
environment.
19. A power plant comprising:
a nacelle cowl having an inlet end and an outlet end;
a primary gas turbine engine mounted within said nacelle
cowl;
said primary gas turbine engine having an aft center-body;
secondary power means for providing pneumatic air to at
least one load; and
said secondary power means being positioned within said aft
center-body.
20. A power plant according to claim 19, further comprising:
a by-pass passage; and
10

said secondary power means having inlet means for drawing a
fluid flowing through said by-pass passage into said secondary
power means.
21. A power plant according to claim 20, further comprising
said secondary power means having an outlet for discharging a
fluid into an exhaust nozzle.
11

Description

CA 02430912 2003-06-03
WO 02/052136 PCT/USO1/47827
MAIN PROPULSION ENGINE SYSTEM INTEGRATED
WITH SECONDARY POWER UNIT
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power plant suitable for
aircraft and, more particularly, to a new power plant
arrangement wherein a secondary power unit is integrated within
a main propulsion system of an aircraft or the like.
2. Description of the Prior Art
It is well known to mount an auxiliary power unit in the
tailcone section of an aircraft to supply pressurized air for
environmental control systems or main engine starting, and shaft
horsepower to drive accessories such as an electric generator
while the aircraft is on the ground and the main propulsion
engines thereof are shutdown. In flight, the auxiliary power
unit is typically shut off. However, auxiliary power units are
occasionally used in flight, for instance, in the event of a
main engine generator malfunction.
Such a tail mounted auxiliary power unit is commonly
considered to be a low-utilization device that adds weight and
complexity to the airplane while providing little operational
benefits during most flight conditions.
SUMMARY OF THE INVENTION
It is therefore an aim of the present invention to simplify
the installation of a secondary power unit by integrating it
with a main engine into a single power plant.
It is also an aim of the present invention to provide
installation and certification cost savings to airframers by
eliminating the tailcone auxiliary power unit installation.

CA 02430912 2003-06-03
WO 02/052136 PCT/USO1/47827
It is a further aim of the present invention to improve the
performances of an aircraft secondary power unit during flight
conditions.
Therefore, in accordance with the present invention, there
is provided a power plant for a vehicle, comprising a nacelle
cowl and a primary gas turbine engine mounted within said
nacelle cowl and forming therewith a main vehicle propulsion
system, and a secondary power system integrated to said main
vehicle propulsion system for providing auxiliary power to the
vehicle.
BRIEF DESCRIPTION OF THE DRAWINGS
Having thus generally described the nature of the
invention, reference will now be made to the accompanying
drawings, showing by way of illustration a preferred embodiment
thereof, and in which:
Fig. 1 is a schematic side view of an aircraft power plant
wherein an auxiliary power unit is mounted in a core compartment
of a main propulsion engine in accordance with a first
embodiment of the present invention;
Figs. 2 to 5 are schematic side views illustrating
different possible inlet and exhaust configurations for a main
engine core mounted auxiliary power unit; and
Fig. 6 is a schematic side view of an aircraft power plant
wherein an auxiliary power unit is mounted to the aft center
body of the main propulsion engine in accordance with a further
embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As will be seen hereinafter, the present invention is
generally directed to a new aircraft power plant, whereby a pair
of secondary power units can be integrated into respective main
aircraft propulsion engines in replacement of a conventional
2

CA 02430912 2003-06-03
WO 02/052136 PCT/USO1/47827
auxiliary power unit, which is typically separately mounted to
the airframe of the aircraft at the tail section thereof.
Fig. 1 illustrates a first embodiment of such a new
aircraft power plant 10. The power plant 10 comprises a nacelle
cowl 12 having an inlet end 11 and an exhaust nozzle end 13, and
a main propulsion engine 14 housed within the nacelle cowl 12.
An inner core cowl 16 is concentrically mounted within the
nacelle cowl 12 about the main propulsion engine 14. The inner
core cowl 16 and the nacelle cowl 12 define therebetween an
annular by-pass passage 18.
The main propulsion engine 14 has a casing assembly 20
defining an annular core flow passage 22. The casing assembly 20
defines with the inner core cowl 16 an engine core compartment
23 in which various components can be received.
The main propulsion engine 14 consists of a gas turbine
engine having a compressor section 24 which typically includes a
fan (not shown) and a high pressure compressor (not shown), a
combustion section 26 and a turbine section 28, as is well known
in the art. In operation, the gas turbine engine inducts ambient
air via the inlet end 11. A portion of the air is diverted into
the by-pass passage 18 and discharged at the exhaust nozzle 13.
Before being directed into the by-pass passage 18, the air is
compressed in the compressor section 24 of the gas turbine
engine. The other portion of the air, which is drawn into the
nacelle cowl 12, is caused to flow through the core flow passage
22. The air flowing through the core flow passage 22 is
compressed in the compressor section 24 and is then directed to
the combustion section 26 where it is mixed with fuel and
ignited. The combustion gases from the combustion section 26 are
then delivered to the turbine section 28 for driving the
compressors (not shown) of the compressor section 24 and the
engine accessories (not shown). The expanded gases from the
3

CA 02430912 2003-06-03
WO 02/052136 PCT/USO1/47827
turbine section 28 are discharged through the exhaust nozzle end
13 with the air emanating from the bypass passage 18.
As seen in Fig. l, a secondary power unit 30 is mounted
within the engine core compartment 23 instead of being mounted
to the aircraft tail section as is conventionally done.
According to the illustrated embodiment, the secondary power
unit 30 consists of an auxiliary power unit of the type used for
providing pneumatic air to loads, such as the aircraft passenger
cabin, electrical power to the aircraft, and starting the main
propulsion engine 14 pneumatically, while the aircraft remains
stationary on the ground. However, it is understood that the
secondary power unit 30 could consist of various types of
multifunction power unit having a gas turbine engine section.
For instance, the secondary power unit could consist of an
auxiliary power unit having an environmental control system
(ECS), such as an air cycle machine. The secondary power unit 30
could also consist of a multifunction power unit integrating an
auxiliary power unit (APU), an emergency power unit (EPU), an
environmental control system (ECS) and an engine start system
(ESS) .
The secondary power unit 30 includes a secondary gas
turbine engine 31 having a compressor section 32, a combustion
section 34 and a turbine section 36. As seen in Fig. 1, a radial
inlet plenum 38 can be provided for allowing air to be drawn
from the by-pass passage 18 directly into the gas turbine engine
31. The radial inlet plenum 38 could be provided in the form of
a ring member defining a number of air passages extending
radially through the engine core compartment 23 to convey air
from the by-pass passage 18 to the secondary gas turbine engine
31. The secondary gas turbine engine 31 includes an axial
exhaust outlet 40 for directing the expanded gases from the gas
turbine section 36 back into the by-pass passage 18.
4

CA 02430912 2003-06-03
WO 02/052136 PCT/USO1/47827
During ground operation, the inlet air is drawn in through
the stationary fan of the primary gas turbine engine and the
exhaust nozzle 13, then through the by-pass passage 18 and
finally into the secondary gas turbine engine 31 before being
discharged back into a aft portion of the by-pass passage 18. In
flight, the secondary gas turbine engine inlet flow is boosted
by the main propulsion engine fan, as it is compressed thereby
before entering into the secondary gas turbine engines 31. This
provides for a better secondary gas turbine engine fuel burn
when operated at altitude. Aircraft pneumatic and electric power
demand is typically provided on the ground by the secondary
power unit 30 and by the main engine 14 during flight
conditions.
A closure member (not shown) displaceable between closed
and open positions can be provided for selectively preventing
air from being drawn into the secondary gas turbine engine 31,
while the main engine 14 is being operated. However, due to the
inlet boost from the main engine fan, the performances of the
secondary power unit 30 are improved as compared to a
traditional tail mounted auxiliary power unit and, thus, the
secondary power unit 30 could be operated at all time, thereby
replacing the engine bleed requirement and eliminating the need
for a closure member.
By integrating the secondary power unit 30 to the power
plant 10 and, thus, eliminating the tailcone auxiliary power
unit installation, significant installation and certification
cost savings can be achieved for the airframers. This is also
advantageous in that it eliminates the need for an aircraft fire
zone and APU containment issues on tail plane, increases the
cargo space, reduces pneumatic/hydraulic/ and fuel lines, and
also allows for structural cost and weight savings.
The positioning of the secondary power unit 30 into the
nacelle cowl 12 also provides for better main engine cold start

CA 02430912 2003-06-03
WO 02/052136 PCT/USO1/47827
capabilities due to the secondary power unit 30 preheating
effect of the main engine core compartment 23. Indeed, while
being operated, the secondary power unit 30 will generate heat
that will contribute to warm up the various components of the
main engine 14.
The re-light characteristics of the secondary power unit 30
will also be improved in flight due to the inlet boost, the ram
air, and the pre-heating thereof by the heat generated by the
main engine 14.
In a wing-mounted application, the integration of the
secondary power unit 30 with the main propulsion engine 14 into
a single power plant will eliminate the need for costly
pneumatic piping.
Figs. 2 to 5 illustrate various possible inlet and outlet
configurations for the secondary gas turbine engine 31.
As shown in Fig. 2, an axial inlet 42 could be defined in
the engine core compartment 23 for directing air from the by-
pass passage 18 directly into the secondary gas turbine engine
31.
Alternatively, as shown in Fig. 3, a urchin" type inlet 44
could be defined in the engine core compartment 23 to direct air
from the by-pass passage 18 into the secondary gas turbine
engine 31.
The secondary gas turbine engine 31 could also be provided
with a radial inlet 46 for receiving air from the engine core
compartment 23 instead of from the by-pass passage 18, as shown
in Fig. 4.
Finally, a hollow inlet strut 48 could extend across the
by-pass passage 18 and through the nacelle cowl 12 to allow
ambient air to be drawn radially into the secondary gas turbine
engine 31, as shown in Fig. 5.
6

CA 02430912 2003-06-03
WO 02/052136 PCT/USO1/47827
As shown in Fig. 4, the expanded gases leaving the
secondary gas turbine engine 31 could be directed into the main
engine exhaust instead of into the by-pass passage 18.
Finally, the expanded gases leaving the secondary gas
turbine engine 31 could be directed overboard to the ambient air
via a hollow outlet strut 50 extending across the by-pass
passage 18 and through the nacelle cowl 12.
It is noted that the inlet and exhausts configurations are
interchangeable.
Fig. 6 illustrates a further embodiment of the present
invention, which only differs from the one illustrated in Fig.
1, by the location of the secondary power unit 30. Indeed,
instead of being integrated in the engine core compartment 23',
the secondary power unit 30' is mounted within the main engine
aft center-body. According to this arrangement, the by-pass
passage 18' constitutes the air inlet source for the secondary
power unit 30'. During ground operation, the inlet air is drawn
through the stationary fan and the exhaust nozzle 13' of the
primary gas turbine engine, then through the by-pass passage 18
and a nacelle inlet 52 connected in fluid flow communication
with turbine exhaust struts 54 and finally into the secondary
gas turbine engine 31' of the secondary power unit 30'. In
flight, the air flowing to the secondary gas turbine engine 31'
has already been compressed by the main engine fan and as a
result the performances of the secondary gas turbine engine 31'
are improved.
It is noted that the present integration concept applies to
either long (Long Duct Mixed Flow) or short cowl (Short Duct
Separate Flow) nacelle configurations and is thus not limited to
the particular type of nacelle cowl illustrated in the drawings.
7

Representative Drawing