GB2034822A

GB2034822A - Gas turbine engine cooling air supply

Info

Publication number: GB2034822A
Application number: GB7936774A
Authority: GB
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1978-11-15
Filing date: 1979-10-23
Publication date: 1980-06-11

Abstract

An arrangement for cooling the cooling air for the turbine blades or other components of a gas turbine engine comprises a closed circuit system by which the cooling air is first cooled by heat exchange with water. Cooling air taken from the compressor discharge is passed through a heat exchanger 24 disposed between the combustion section 16 and the rotor shaft, the air being cooled by flow of water which is thereby evaporated. The steam passes through line 30 to a condenser 26 disposed around the engine air intake, the condensate passing to a pressurised reservoir 44 and feed pump 40 back to the heat exchanger. The cooled air passes to components for cooling thereof. The reservoir is pressurised by air taken from the engine compressor through accumulator 48. <IMAGE>

Description

SPECIFICATION Improvements in or relating to the supply of cooling air for gas turbine engine components This invention relates to the supply of cooling air for gas turbine engine components, in particular the supply of cooling air to the high pressure turbine blades of a stationary gas turbine engine.

It is well established that increasing the gas temperature at the turbine inlet will increase the power available and efficiency of a gas turbine engine. The increase of turbine entry temperatures results in a need for turbine blade materials which are either able to meet the demands of the increased temperatures and/or which can be cooled to suitable operating temperatures. The blade cooling is generally achieved by the provision of internal passages in the blades, which are supplied with high pressure air from the engine compressor and which exhausts through discharge apertures into the gas flow. The cooling air because it has been compressed is at a relatively high temperature itself and this determines its cooling capability.

The present invention seeks to provide a means of cooling the cooling air without substantially affecting the pressure thereof thereby increasing the cooling capability and indirectly allowing a higher turbine entry temperature for a given blade material and cooling arrangement.

According to the present invention there is provided a gas turbine engine comprising in flow series an intake, compressor means, combustion means and turbine means being arranged to receive a flow of cooling air from the compressor means, the engine also including cooling means arranged to cool the flow of cooling air, the cooling means comprising heat exchanger means having a first flow path through which the cooling air flows and a second flow path through which a cooling medium flows in a closed circuit.

The cooling medium may comprise water and heat exchanger means may then comprise a flash boiler and the closed circuit may comprise the first flow path of the heat exchanger means, a condenser mounted upstream of the engine intake and a condensate pump which may be engine driven, either directly or indirectly or driven by an external power.

The closed circuit may also include a condensate reservoir which is pressurised by an accumulator which is itself pressurised from an engine pressure tapping.

In another arrangement, in which the cooling medium also comprises water and the heat exchanger means comprises a boiler, the condenser may be so mounted in relation to the heat exchanger means that boiler is gravity fed with water.

The present invention will be more particularly described with reference to the accompanying drawings in which: Figure 1 shows a general schematic arrangement of one form of gas turbine engine according to the present invention, Figure 2 shows a general arrangement of a further form of gas turbine engine according to the present invention, Figure 3 shows part of the combustion chamber and cooling apparatus of the gas turbine engine shown in Figure 2, Figure 4 is a view on arrow A in Figure 3 and Referring to the Figures, in Figure 1 there is shown a gas turbine engine 10 having an intake 12, compressor means 14, combustion means 1 6 and turbine means 1 8, the compressor and turbine means being coupled by a shaft 20.

The delivery air from the compressor means is divided into two flow paths, one through the combustion means and the other which provides a flow of cooling air for the blades and/or discs of the turbine means. The flow of cooling air, which whilst being at a relatively high pressure is also at a relatively high temperature as a result of its passage through the compressor means, passes through a first flow path of a cooling means 22, part of which in the form of a heat exchanger, boiler or evaporator 24 is located between the combustion means 1 6 and the shaft 20, the flow path through the evaporator constituting a second flow path of the cooling means.The cooling means also includes a condenser 26 which is cooled by atmosphere and which is arranged to feed water to the evaporator 24 by gravity through a pipe 28, the steam formed in the evaporator being returned to the top of the condenser by a pipe 30.

In operation, some of the delivery air from the compressor means flows over the evaporator 24, i.e. through the first flow path of the cooling means 22 where heat is extracted and the cooled cooling air then flows to those parts of the engine to be cooled, for example, the high pressure turbine blades, turbine discs and shaft bearings.

The heat extracted from the cooling air flow passes into the water from the condenser, the water flowing through the second flow path of the cooling means 22. In the evaporator, the water turns to steam and rises in pipe 30 to the condenser where the steam reverts to water by means of a flow of atmospheric air through the condenser and the water pump returns to the evaporator 24 by pipe 28. The condenser 26 has a vent 32 to allow steam to escape to atmosphere in the event of excess quantities of steam being produced.

Referring now to Figures 2 to 4 inclusive in which the same reference numerals have been used to denote similar features, the arrangement is generally similar to that shown in Figure 1 with the following basic differences. The feed from the condenser is no longer gravity fed and the feed water for the evaporator is pumped from the condenser to the evaporator by a pump 40 which can be of any suitable type driven either independently, e.g. by electric or hydraulic motor, or from the engine 10. The condenser is mounted in a casing 42 located upstream of the inlet 1 2 of the engin 10, so that the incoming air for the engine provides the cooling medium for the steam.

The water from the condenser passes into a pressurised reservoir 44 which has a bleed valve 46, the water then being pumped to the evaporator by the pump 40. The pressurisation for the reservoir 40 is providad by an accumulator 48 connected to the reservoir by a pipe 49, the accumulator itself being pressurised by a bleed of high pressure compressor air from the engine 10.

The evaporator 24, shown in more detail in Figures 3 and 4 is located between the combustion means 16, which in this case comprises an annular combustion chamber and associated fuel injectors (not shown)- and the shaft 20. The evaporator comprises two pipes 50 each wound into two helical banks and each having a single inlet (not shown) for feed water and two outlets 52 for the steam produced in the evaporator, the outlets all being joined to the pipe 30 taking the steam to the condenser 26.

The first flow path through the cooling means 22 for the cooling air is constituted by a passage 54 leading from the downstream end of the compressor means between the combustion means 16 and the shaft 20 to that part of the engine to be cooled. The second flow path partly consists of the two pipes 50 into which water flows and from which steam is exhausted.

The condenser 26 need not be cooled by the incoming air to the engines and the condenser can be located in any convenient position and cooled by air supplied from an independently driven fan.

Claims

1. A gas turbine engine comprising in flow series, an intake, compressor means, combustion means and turbine means arranged to receive a flow of cooling air from the compressor means, the engine also including cooling means to cool the flow of cooling air, the cooling means comprising heat exchanger means having a first flow path through which the cooling air flows and a second flow path through which a cooling medium flows in a closed circuit.

2. An engine as claimed in claim 1 in which the cooling medium comprises water and the heat exchanger means comprises a flash boiler, the cooling medium flowing back to the flash boiler via a condenser.

3. An engine as claimed in claim 2 in which the condenser is mounted upstream of the engine in line with the airflow into the intake.

4. An engine as claimed in claim 2 in which the condenser is so mounted in relation to the boiler that the condensate is gravity fed to boiler.

5. An engine as claimed in claim 2 in which the cooling means includes a condensate reservoir, a pump means to return the condensate to the boi!er, the condensate reservoir being pressurised by an accumulator itself pressurised by compressed air from the engine.

6. An engine as claimed in claim 2 in which the boiler is located between the engine combustion means and a shaft connecting the compressor and turbine means, the second flow path comprising inner and outer tube banks, each bank being wound into two coils and having inlet means for the condensate and outlet means for the steam produced in the boiler.

7. A gas turbine engine constructed and arranged for use and operation substantially as herein described with reference to and as shown in Figure 1 and Figures 2, 3, and 4 of the accompanyinn drawings.