Cooling system for a turbomachine speed reducer

Details Cooling system for a turbomachine speed reducer Cooling system for a turbomachine speed reducer

2000-01-03

2001-09-04

Kim, Ted (Department: 3746)

Power plants

Combustion products used as motive fluid

With lubricators

C060S039010, C060S226300, C060S226100, C184S006110

Reexamination Certificate

active

06282881

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application is related and claims priority, under 35 U.S.C. §119, to French Patent Application No. 99-00082 filed on Jan. 7, 1999, the entire contents of which is hereby incorporated by reference herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to turbomachincs having a speed reducer and more particularly, to turboprop engines and high-power bypass turbojet engines, such as are used in civil aviation.
2. Discussion of Background
To improve performance while reducing noise and fuel consumption, turbomachines such as turboprop engines must have slow-running large-diameter multiple blade propellers. However, the power transmitted to a slow-running propeller from a fast-running gas turbine through a mechanical speed reducer produces considerable heat as a result of mechanical losses—i.e., due to friction. Of course, this heat must be dissipated or removed efficiently, otherwise the mechanical parts of the reducer, such as the gears and bearings, will soon be damaged or the qualities of the reducer lubricant will be impaired, leading to decreased engine efficiency. Even with an efficiency of close to or even exceeding 99%, the speed reducer of a turbomachine with a mechanical power equivalent to 10,000 kW, evolves a heat equivalent of 100 kW due to mechanical losses.
It is well known in the art to remove this kind of heat—i.e., to dissipate this kind of thermal power —by means of a closed-circuit pump or thermosyphonic circulation of the reducer lubricant through a radiator, such as an oil radiator or an oil-air exchanger.
FIG. 1
shows a schematic view of one possible example of this known form of cooling. In
FIG. 1
the propeller
1
of a turboprop engine is driven by a gas generator
2
through a speed reducer
3
. The speed reducer
3
is cooled by circulation of its lubricant through a cooling circuit
4
including a radiator
6
disposed in the bottom scoop
5
of the engine. The radiator
6
may also be disposed below the aircraft wing
20
or even laterally with respect to the aircraft wing
20
.
In the example shown in
FIG. 1
, the air moving through the radiator
6
removes the heat to outside the bottom scoop
5
, and the cooled lubricant returns to the speed reducer
3
through the cooling circuit
4
. If required, a flap (not shown) can be provided at the entry or exit of the scoop
5
to control the rate of air flow through the radiator
6
in order to stabilize the temperature of the lubricant, since at high speed the radiator
6
is oversized, as compared with low speeds. This kind of radiator
6
, particularly if it is an air-oil heat exchanger, must be large if it is to remove substantial amounts of heat. This is the case, inter alia, during low speed flight, during prolonged parking with the engine idling, and also during runway taxying. This kind of equipment is therefore heavy and bulky, increases engine drag, requires a large quantity of oil, and is very vulnerable to the intake of birds.
However, this latter disadvantage does not occur with a cooling system such as that described in French patent application No. FR-A-2 742,479 (hereinafter “FR'479”). In FR '479, the boundary layer of the air flow over the engine nacelle, particularly in the zone where this boundary flow becomes turbulent as aircraft speed increases, is aspirated via holes in the cowling so that air is drawn into a collector in which a long heat exchanger, which forms a part of the cooling system, is disposed. However, since the rate of air flow through the holes is low this cooling system needs a very long, and therefore very bulky, heat exchanger.
SUMMARY OF THE INVENTION
It is an object of the present invention to overcome the disadvantages of the prior art cooling systems, particularly as above-described.
Since an aircraft spends more of its time at medium or high speeds than at low speeds or idling, it would appear more appropriate to dimension the air-oil radiator for the longest flight phases and, during the shorter phases, to increase temporarily the air flow through the radiator in some appropriate fashion, rather than to reduce the air flow through an oversize radiator by means of flaps.
Accordingly, the present invention provides a turbomachine including: at least one air intake scoop; an internal gas flow path; an exhaust nozzle; a speed reducer, which is arranged to be lubricated by a lubricant; and a cooling system for the lubricant. The cooling system includes: a lubricant circuit for the flow of lubricant to and from the speed reducer; a radiator, in the lubricant circuit, for dissipating heat from the lubricant as it flows through the radiator; an air supply duct leading to the radiator; and at least one air take-off slot, of very reduced cross-section, disposed in the air intake scoop of the turbomachine, wherein the air take-off slot communicates with and feeds air to the air supply duct.
Preferably, the cooling system also includes an air discharge duct leading from the radiator and opening into the exhaust nozzle of the turbomachine.
In order to vary the rate of air flow through the radiator, it is also preferable to provide a pivotally mounted flap in the air discharge duct.
To ensure an adequate rate of air flow through the radiator when the air flow into the turbomachine is low and to enable a radiator of reduced size to be used, if the turbomachine has at least one compressor, the cooling system, according to the present invention, preferably also includes a compressed air take-off duct, connected to the compressor, and opening into the air discharge duct through an ejector-mixer in order to accelerate the air flow through the cooling system; and a control valve for controlling said compressed air take-off duct and controlled by a control unit of the turbomachine.


REFERENCES:
patent: 4351150 (1982-09-01), Schulze
patent: 4409788 (1983-10-01), Nash
patent: 4765131 (1988-08-01), Benson
patent: 4999994 (1991-03-01), Rud et al.
patent: 5265408 (1993-11-01), Sheoran et al.
patent: 5438823 (1995-08-01), Loxley et al.
patent: 5553449 (1996-09-01), Rodgers et al.
patent: 5806793 (1998-09-01), Brossier et al.
patent: 5987877 (1999-12-01), Steiner
patent: 6000210 (1999-12-01), Negulescu
patent: 6058696 (2000-05-01), Nikkanen et al.
patent: 6092360 (2000-07-01), Hoag et al.
patent: 195 24 731 (1997-01-01), None
patent: 0 514 119 (1992-11-01), None
patent: 0 743 247 (1996-11-01), None
patent: 2 742 479 (1997-06-01), None
patent: WO 92/11451 (1992-07-01), None

Affiliated with

Also associated with

Rating

Cooling system for a turbomachine speed reducer does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Cooling system for a turbomachine speed reducer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cooling system for a turbomachine speed reducer will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2534767