Reversible system for dissipating thermal power generated in a gas-turbine engine

Abstract

A reversible system for dissipating heat power generated in a gas turbine engine, the system including a condenser-forming first heat exchanger, an evaporator-forming second heat exchanger, a scroll compressor suitable for operating as a compressor when the temperature of the cold source is higher than a predefined threshold temperature and as a turbine when the temperature of the cold source is lower than the threshold temperature, an expander and a pump arranged in parallel, and a control valve arranged upstream from the expander and the pump and suitable for directing the refrigerant fluid to the expander when the temperature of the cold source is higher than the threshold temperature and to the pump when the temperature of the cold source is lower than the threshold temperature.

Claims

1. A reversible system for dissipating heat power generated in a gas turbine engine, the system comprising: a condenser-forming first heat exchanger for exchanging heat between a refrigerant fluid and a cold source; an evaporator-forming second heat exchanger for exchanging heat between the refrigerant fluid and a hot source generating heat power; a scroll compressor arranged upstream from the first heat exchanger and downstream from the second heat exchanger; the scroll compressor for operating as a compressor when a temperature of the cold source is higher than a predefined threshold temperature and as a turbine when the temperature of the cold source is lower than the predefined threshold temperature; an expander and a pump arranged in parallel downstream from the first heat exchanger and upstream from the second heat exchanger; and a control valve arranged upstream from the expander and the pump for directing the refrigerant fluid to the expander when the temperature of the cold source is higher than the threshold temperature and to the pump when the temperature of the cold source is lower than the threshold temperature.

2. The system according to claim 1, wherein the hot source generating heat power is an oil of an oil circuit of the gas turbine engine and the cold source is air coming from a flow passage for a secondary stream through the gas turbine engine.

3. The system according to claim 2, wherein the first heat exchanger is for positioning in the flow passage for the secondary stream through the gas turbine engine.

4. The system according to claim 2, wherein the second heat exchanger, the scroll compressor, the expander, and the pump are positioned in a nacelle gas turbine of the engine.

5. A gas turbine engine including an oil circuit and a reversible system, the reversible system comprising: a condenser-forming first heat exchanger for exchanging heat between a refrigerant fluid and a cold source; an evaporator-forming second heat exchanger for exchanging heat between the refrigerant fluid and a hot source generating heat power; a scroll compressor arranged upstream from the first heat exchanger and downstream from the second heat exchanger; the scroll compressor for operating as a compressor when a temperature of the cold source is higher than a predefined threshold temperature and as a turbine when the temperature of the cold source is lower than the predefined threshold temperature; an expander and a pump arranged in parallel downstream from the first heat exchanger and upstream from the second heat exchanger; and a control valve arranged upstream from the expander and the pump for directing the refrigerant fluid to the expander when the temperature of the cold source is higher than the threshold temperature and to the pump when the temperature of the cold source is lower than the threshold temperature, and wherein the reversible system dissipates heat power generated by an oil of the oil circuit.

6. A method of operating a reversible system according to claim 1, wherein: the control valve is activated to direct all of the refrigerant fluid that has passed through the first heat exchanger to the expander when the temperature of the cold source is higher than the predefined threshold temperature, the scroll compressor then acting as a compressor; and the control valve is activated to direct all of the refrigerant fluid that has passed through the first heat exchanger to the pump when the temperature of the cold source is lower than the predefined threshold temperature, the scroll compressor then operating as a turbine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other characteristics and advantages of the present invention appear from the following description made with reference to the accompanying drawings, which show an embodiment having no limiting character. In the figures:

(2) FIGS. 1 and 2 are diagrammatic views of a system of the invention for cooling the oil of a turbine engine oil circuit, the system being shown respectively in its two operating configurations; and

(3) FIG. 3 is a diagrammatic cross-section view of a turbine engine showing the physical locations of the elements of the system shown in FIGS. 1 and 2.

DETAILED DESCRIPTION OF THE INVENTION

(4) The invention applies to dissipating any type of heat power generated in a gas turbine engine and that needs to be discharged.

(5) The example described below relates more particularly to dissipating the heat power generated by heating the oil in an oil circuit of a turbine engine. Nevertheless, the system of the invention could equally well apply to dissipating heat power coming from the heating of various electrical components of a gas turbine engine, e.g. such as batteries or electrical power generators.

(6) In known manner, the oil circuit of a turbine engine includes various pieces of equipment that use the cooling and/or lubricating oil, such as bearings (in particular for the turbine and compressor shafts), gearboxes (such as the accessory gearbox), electricity generators, etc.

(7) The oil circuit also includes return pumps for recirculating the oil from the equipment to an oil tank, feed pumps, one or more filters, and one or more oil/fuel heat exchangers (FCOC heat exchangers).

(8) The oil circuit also has a reversible oil cooling system of the invention.

(9) As shown in FIGS. 1 and 2, the cooling system 2 comprises a refrigerant fluid circuit 4 having a condenser-forming first heat exchanger 6, the first heat exchanger serving to exchange heat between the refrigerant fluid and air bled from the flow passage for the secondary stream through the turbine engine.

(10) The refrigerant fluid circuit 4 also has an evaporator-forming second heat exchanger 8, the second heat exchanger 8 serving to exchange heat between the refrigerant fluid and oil coming from the oil circuit.

(11) Upstream from the first heat exchanger 6 (in the flow direction of the refrigerant fluid), and downstream from the second heat exchanger 8, the refrigerant fluid circuit further includes a scroll compressor 10.

(12) A scroll compressor (also known as a spiral compressor) is a known type of compressor that makes use of two interleaved scrolls as vanes for pumping and compressing fluid. Generally, one of the scrolls is stationary while the other moves eccentrically without rotating so as to pump and then hold captive and finally compress pockets of fluid between the scrolls.

(13) The scroll pump 10 is an apparatus that is reversible and can thus be caused to operate in alternation in two different modes, namely as a compressor or as a turbine. These different operating modes are described below.

(14) The refrigerant fluid circuit further includes an expander 12 (or expansion valve) and a pump 14 that are connected in parallel downstream from the first heat exchanger 6 and upstream from the second heat exchanger 8. A control valve 16 (e.g. of the thermostatic type) is arranged upstream from the expander 12 and the pump 14 so as to be able to direct the refrigerant fluid either to the expander when the temperature of the air is greater than a predefined threshold pressure or else to the pump when the temperature of the air is less than this threshold temperature. The predefined threshold temperature may vary as a function of the heat power to be dissipated from the oil. By way of example, it may be set at 20 C.

(15) The cooling system of the invention operates as follows.

(16) During stages of flight in which the temperature of the air flowing through the flow passage for the secondary stream in the turbine engine is greater than the predefined threshold temperature (e.g. stages of idling on the ground under hot conditions), the cooling system of the invention operates as a heat pump (FIG. 1).

(17) In this mode of operation, the refrigerant fluid is heated and vaporized in the second heat exchanger 8 using the heat taken from the oil of the cooling circuit (the flow of oil through the second heat exchanger is represented by arrow F.sub.H). The vapor is then compressed (to high temperature and high pressure) by the scroll compressor 10 operating as a compressor.

(18) Thereafter, the refrigerant fluid is condensed with air by the first heat exchanger 6 (the air stream through the first heat exchanger is represented by arrow F.sub.A) so as to be finally expanded by passing through the expander 12. More precisely, the control valve 16 is activated (preferably automatically if it is a thermostatic type valve) in order to bypass the pump 14 and direct all of the refrigerant fluid that has passed through the first heat exchanger to the expander 12.

(19) In this mode of operation, it is possible in particular to raise the temperature of the refrigerant fluid to temperatures that are much higher than the temperature of the oil, thereby enabling the efficiency of the first heat exchanger 6 to be increased and thus limiting its size so as to avoid impacting the overall performance of the turbine engine.

(20) During stages of flight in which the temperature of the air is lower than the predefined threshold temperature (which corresponds for example to stages of cruising flight in nominal or cold conditions), the temperature difference between the oil and the air becomes large enough to transform the power dissipated by the heat of the oil into mechanical work. The cooling system of the invention then operates as an organic Rankine cycle (FIG. 2).

(21) In this mode of operation, the refrigerant fluid is heated and vaporized in the second heat exchanger 8 by the heat of the oil (the oil flow through the second heat exchanger is represented by arrow F.sub.H), and then the vapor is expanded in the scroll compressor 10, which then operates as a turbine in order to produce mechanical work.

(22) The vapor is then condensed with air by the first heat exchanger 6 (the air flow through the first heat exchanger is represented by arrow F.sub.A) and is transformed into liquid, which is then pumped by the pump 14. More precisely, the control valve 16 is activated to bypass the expander 12 and to direct all of the refrigerant fluid that has passed through the first heat exchanger to the pump 14.

(23) In this mode of operation, which corresponds to the longest stages of operation of the turbine engine during a flight, the cooling system delivers mechanical work (instead of consuming it), thereby enabling the performance of the engine to be improved. For example, this mechanical work may be used to deliver power to hydraulic pumps pumping fuel or oil.

(24) FIG. 3 is a diagram showing an example of how the various elements of the cooling system of the invention can be installed within a two-spool bypass type turbine engine.

(25) FIG. 3 is a cross-section showing the gas generator 18 of the turbine engine centered on a longitudinal axis 20 of the engine. The gas generator is surrounded by a nacelle 22 that is likewise centered on the axis 20 so as to co-operate therewith to define an annular flow passage 24 for the secondary stream.

(26) The air used as the cold source by the cooling system of the invention in this example is preferably air coming from the flow passage 24 for the secondary stream through the turbine engine. For this purpose, the first heat exchanger 6 is positioned in the flow passage for the secondary stream, e.g. against an inside surface of the nacelle 22 that defines the outside of the passage.

(27) The second heat exchanger 8, the scroll compressor 10, the expander 12, and the pump 14 can all be positioned directly in the nacelle 22 of the turbine engine.