US3651645A

US3651645A - Gas turbine for aircrafts

Info

Publication number: US3651645A
Application number: US79508A
Authority: US
Inventors: Hubert Josef Grieb
Original assignee: MTU Motoren und Turbinen Union Muenchen GmbH
Current assignee: Daimler Benz AG; MTU Aero Engines AG
Priority date: 1969-10-11
Filing date: 1970-10-09
Publication date: 1972-03-28
Anticipated expiration: 1989-03-28
Also published as: DE1951356A1; DE1951356C3; DE1951356B2; FR2065179A5; GB1287983A

Abstract

A gas turbine for aircrafts, particularly jet engines with aircooled turbine blades whereby the cooling air is taken off either directly or indirectly from a compressor stage; a heat-exchanger with a closed circulation is provided in the cooling system whose heat-absorbing part is arranged in a cooling air channel disposed between the compressor and the turbine rotor.

Description

United States Patent Grieb 51 Mar. 28, 1972 GAS TURBINE FOR AIRCRAFTS 21 Appl. No.: 79,508

3,301,526 1/1967 Chamberlain ..60/39.66 2,992,529 7/1961 Sampletro ..60/39.66 3,083,532 4/1963 Cook ..60/39.66 3,253,406 5/1966 Grieb... .....60/262 3,418,808 12/1968 Rich ..60/226 3,437,313 4/1969 Moore ..60/39.66 3,584,458 6/1971 Wetzler ..60/39.66

FOREIGN PATENTS OR APPLICATIONS 861 ,632 2/1961 Great Britain ..60/39.66

[30] Foreign Application Pnonty Data Primary EXaminer Mark M Newman Oct. 11, 1969 Germany ..P 19 51 356.5 Assistant ExaminerRichard Rothman Attorney-Craig, Antonelli, Stewart & Hill [52] U.S. Cl ..60/262, 60/3966 [51] Int. Cl. ..F02c 7/12, F02c 7/14 [57] ABSTRACT [58] Field oISearch ..60/262, 226, 39665523655651, A gas turbine for aircrafts particularly jet engines with aib cooled turbine blades whereby the cooling air is taken off [56] References Cited either directly or indirectly from a compressor stage; a heatexchanger with a closed circulation is provided in the cooling UNITED STATES PATENTS system whose heat-absorbing part is arranged in a cooling air channel disposed between the compressor and the turbine ro- 2,465,099 3/1949 Johnson ..60/262 X ton 2,501,633 3/1950 Price ...60/262 2,703,477 3/1955 Anxionnaz ..60/262 16 Claims, 4 Drawing Figures N. :l S

PATENTEDMAR28 1972 3. 651 ,645

SHEET 1 OF 2 INVENTOR HUBERT J. GRIEB ATTORNEYS PATENTED MR 2 8 I972 SHEET 2 [IF 2 GAS TURBINE FOR AIRCRAFIS The present invention relates to a gas turbine for aircrafts, especially to a jet engine, with air-cooled turbine blades whose cooling air is taken off either directly or indirectly from a compressor stage. With such types of gas turbines, one aims at an increase of the output by an increase of the turbine inlet temperature of the operating gases. However, limitations are imposed thereon by the heat resistance of the available materials. The use of strongly compressed air for the improvement of the blade cooling results in a favorable pressure drop for the cooling air stream, however, on the other hand, it reduces the cooling effect by the heating of the cooling air connected with the compression. The present invention has as its purpose to eliminate this shortcoming and to enable an output increase of the gas turbine by an effective cooling of the turbine blades. This is realized according to the present invention by a heatexchanger with closed circulation, whose heat-absorbing part is arranged in the cooling air channel between the compressor and the turbine rotor. By the use of such an arrangement a good blade-cooling can be achieved also with strongly compressed cooling air so that also high turbine inlet temperatures are possible. In this manner, an increase of the turbine output or, with with the same output, a smaller structural weight and smaller dimensions of the gas turbine are achieved by the present invention.

The heat-exchanger may be so arranged according to the present invention in the gas turbine that the heat-absorbing part of the heat-exchanger is arranged in an annular space between the rotor shaft and the combustion chambers, which part is connected on the one hand, with the compressor outlet diffusors and, on the other, with the blades at least of the first turbine stage. Oneobtains with this arrangement highly compressed air for the purpose of blade cooling, which is able to absorb a sufficient amount of heat and therebeyond produces a good pressure drop. By reason of the fact that only the thermally most strongly stressed turbine stages are supplied with cooled compressor air, one is able to get along in an advantageous manner with a small heat-exchanger so that the structural expenditures are of no significance in comparison to the output gain.

Theheat-releasing part of the heat-exchanger, i.e., the part of the heat-exchanger that gives off heat, may be arranged according to the present invention at the inlet of the compressor. This has the advantage that the air flowing past this place has its lowest temperature. According to another embodiment of the present invention for ducted-fan-jet power plants or engines, the heat-releasing part of the heat-exchanger which gives off the heat, is arranged in the bypass channel. This arrangement makes possible with slight additional structural expenditures a favorable heat transfer to the air flowing in the bypass channel.

Accordingly, it is an object of the present invention to provide a gas turbine for aircrafts which avoids by simple means the aforementioned shortcomings and drawbacks encountered in the prior art.

Another object of the present invention resides in a gas turbine which permits an increase in the output by an increase of the turbine inlet temperature of the working gases.

A further object of thepresent invention resides in a gas turbine for aircrafts which allows a good cooling of the blades also with a strongly compressed cooling air.

A still further. object of the present invention resides in a gas turbine for jet engines which results in a relatively slight structural weight and small dimensions of the turbine for the relatively high output of the turbine.

These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, several embodiments in accordance with the present invention, and wherein:

FIG. 1 is a schematic longitudinal cross-sectional view through a pure jet engine in accordance with the present invention;

FIG. 2 is a schematic longitudinal cross-sectional view through a ducted-fan-jet engine in accordance with the present invention;

FIG. 3 is-a partial longitudinalcross-sectional view illustrating the heat-exchanger for the blade cooling system of a jet engine according to FIG. 2; and

FIG. 4 is a schematic control diagram of a heat-exchanger in accordance with the present invention.

Referring now to the drawing, an d more particularly to FIG. 1, a low pressure compressor 13 and a low pressure turbine 14 are mounted on and secured to a shaft 12 within the housing 11 of the pure jet engine illustrated in this figure while a high-pressure compressor 16 and a high-pressure turbine 17 are secured on a hollow shaft 15 coaxial to the shaft 12. The combustion chambers of the jet engine are designated by reference numeral 18. The blades 19 of the first turbine stage 20 are cooled by compressed air which is taken off from the last stage 21 of the high-pressure compressor 16. The cooling air is conducted for that purpose through the annular space 22 formed between the hollow shaft 15 and the combustion chambers 18. The heat-absorbing part 23 of a heat-exchanger generally designated by reference numeral 24 with closed circulatory system is arranged in the annular space 22. The heatreleasing or heat-transferring part 25 of the heat-exchanger 24 which gives off heat, is secured at the compressor inlet 26 and is connected with the heat-absorbing part 23 by

lines

27 and 28.

In contradistinction thereto, in the ducted-fan-jet engine illustrated in FIG. 2, the heat-transferring or heat-releasing part 29 of a heat-exchanger 30 also with closed circulatory system is accommodated in the bypass channel 33 surrounded by a jacket or casing 31 and delimited inwardly by a housing 32. The heat-absorbing part 34 is arranged, similar as in the example according to FIG. 1, in an annular space 35 between the combustion chambers 36 and a hollow shaft 37. The hollow shaft 37 connects a high pressure compressor 38 with a highpressure turbine 39. A shaft 40 for a low pressure compressor 41 and a low pressure turbine 42 is extended through the hollow shaft 37.

Lines

43 and 44 connect the heat-absorbing part 34 with the heat-releasing part 29 of the heat-exchanger 30.

The ducted-fan-jet engine partially illustrated in FIG. 3 corresponds in its essential construction to that of FIG. 2. A shaft 46 for a low-pressure compressor (not shown) and a low-pressure turbine 48 as well as a hollow shaft 49 surrounding the shaft 46 for a high-pressure compressor 50 and a high-pressure turbine 51 are rotatably supported in the housing 45. Reference numeral 52 designates rotor blades and reference numeral 53 guide blades of the last stage generally designated by reference numeral 54 of the high pressure compressor 50. Compressor outlet diffusors 55 terminate in the combustion chambers 56, in each of which are arranged a flame tube 57 of conventional construction with a fuel feed line 58. Guide blades 59 and rotor blades 60 of the first turbine stage generally designated by reference numeral 61 adjoin the same. The bypass channel of the ducted fan-jet engine is designated by reference numeral 62.

The combustion chambers 56 are provided each within the area of the compressor outlet diffusors 55 with apertures 63, through which a part of the compressed air is able to flow over into an annular space 64 disposed between the hollow shaft 49 and the combustion chambers 56. From there, the air is fed by way of an annular channel 66 sealed off by labyrinth seals to the first turbine stage generally designated by reference numeral 61. Therotor blades 60 of this stage 61 have hollow spaces 67 which are in communication with the blade surface so that the compressed air is able to escape and is able to cool the thermally particularly strongly stressed turbine blades 60.

The heat-absorbing part 68 of a heat-exchanger 69 with closed circulation is arranged in the annular space 64. A line 70 leads from the heat-absorbing part 68 within the area of the compressor outlet diffusor55 to the'heat-releasing part 71 which'gives off heat and is arranged in the bypass channel 62 of the jet engine. A line 72 leads from the heat-transferring part 71 to a circulating pump (not shown) for the cooling medium and from there a further line 73, parallel to the line 70, leads back to the heat-absorbing part 68 of the heatexchanger 69. The two

lines

70 and 73 are lined on the inside of the compressor outlet diffusor 55 by a hollow rib 74. The heat-absorbing part 68 and the heat-transferring part 71 are arranged in parallelly connected heat-exchanger groups, for example, consisting of pipe coils and uniformly distributed over the circumference of the annular space 64 and the bypass channel 62.

In operation, the heat-absorbing part 68 of the heatexchanger 69 cools the highly compressed and strongly heated air taken off from the compressor outlet diffusor 55, which flows through the annular space 64. The cooling medium heated up thereby, flows through the line 70 to the heat-transferring part 71 of the heat-exchanger 69 and thereby gives off heat to the less strongly compressed and relatively cool air flowing in the bypass channel 62. The cooling medium is again conducted back to the heat-absorbing part 68 by way of the line 73 by means of the circulating pump (not shown).

The cooled compressor air flows from the annular space 64 by way of the annular channel 66 into the hollow spaces of the rotor blades 60 of the first turbine stage 61. The air escapes out of the rotor blades 60 by way of openings (not shown) and cools the thermally highly stressed surfaces thereof. The temperature decrease of the highly compressed cooling air achieved by the heat-exchanger of the present invention improves the blade cooling and permits thereby the application of higher pressures and temperatures of the working gases. This leads to a considerable increase of the specific thrust or permits the construction of more lightweight and smaller jet engines.

The cooling air may be taken off, instead of from the compressor diffusor as shown in the illustrated embodiment, also directly from a compressor stage. Cooled compressor air may, in case of need, be branched off also for further stages in addition to the first turbine stage, whereas the remaining turbine stage, insofar as necessary, are supplied with uncooled compressor air. The turbine guide blades may also be cooled with uncooled compressor air whereby possibly the rate of air flow of the first stage is slightly increased.

The heat-exchanger 75 illustrated in FIG. 4 in a schematic diagram which has a closed circulator system, essentially consists of the heat-absorbing part 76 and of the heat-transferring or heat-releasing part 77 as well as of a circulating pump 78 and the

lines

79 and 80. The heat-absorbing part 76 is subdivided into parallel pipe lines 81. The compressed air branched off from the compressor for the blade cooling flows through the pipe lines 81 which is indicated by an arrow 82. The heattransferring part 77 subdivided in a similar manner into pipe lines 83 is located in an air stream indicated by an arrow 84 which, for example, is conducted through the bypass. The circulating pump 78 as well as a charging pump 85 are driven in this example by an electric motor 86.

The charging pump 85 supplies cooling medium under pressure out ofa tank 87 through the

lines

88 and 89 into the line 80. The operating pressure is appropriately chosen so high that the boiling temperature of the cooling medium is not attained. A check valve 90 disposed in the line 89 closes after the charging of the circulatory system and thus prevents a return flow of the cooling medium. In case ofa decrease of the pressure, the charging pump 85 supplies cooling medium to the circulatory system until the minimum pressure is again reached. In this manner, also in case of an occurrence of a leakage place, the operation can be maintained at least for a short period of time. An excess pressure valve 91 is disposed in a line 91 leading from the line 88 to the tank 87 which prevents that the pressure of the supplied cooling medium exceeds a predetermined value.

Lines

93 and 94 conduct cooling medium that is discharged out of the

bearings

95 and 96 of the circulating pump 78 and of the charging pump 85, respectively, back into the tank 87. v

A line 97 is connected to the line 79 which branches off into

lines

98 and 99 that lead to an equalization tank generally designated by reference numeral 100 and to an excess pressure valve 101, respectively. The equalization tank 100 absorbs against the pressure of an air cushion 102 the excess cooling liquid caused by heat expansion and returns the same again to the circulatory system when the cooling liquid cools off again. The excess pressure valve 101 opens a return line 103, when the permissive operating pressure is exceeded, and thus avoids damages in the installation.

A warning installation 104 consists of a pressure-measuring device 105 disposed in the circulatory system which closes the energizing circuit of a warning lamp 106 when the pressure drops below a minimum operating pressure. The illumination of the warning lamp 106 indicates that the cooling circulatory system no longer operates satisfactorily. With a turbine operating at full load, the fuel supply can be timely throttled thereafter so that an overheating of the turbine is avoided. in the same manner, also the operation of the circulating pump can be monitored by a differential pressure-measuring device connected in parallel thereto which in case of a pump damage cases a warning lamp to light up. It is also possible to automatically limit the fuel supply by any conventional means in case of failure of the cooling circulatory system.

Water may be utilized a cooling liquid whose properties can be improved by suitable additives and/or admixtures, for example, for the purpose of increasing its lubricating capacity. For flights at high altitude and during the winter, an antifreeze agent, for example, glycol, has to be admixed to the cooling water.

While I have shown and described several embodiments in accordance with the present invention, it is understood that the same is not limited thereto, but is susceptible of numerous changes and modifications as known to those skilled in the art, and I therefore do not wish to be limited to the details shown and described herein, but intend to cover all such change and modifications as are encompassed by the scope of the appended claims.

What I claim is:

1. A gas turbine for aircraft having a compressor means and air-cooled turbine blade means whose cooling air is taken off from a compressor stage, characterized by a heat-exchanger means with closed circulatory system whose heat-absorbing part is arranged in a cooling air channel means between the compressor means and a turbine rotor means.

2. A gas turbine according to claim 1, characterized in that the cooling air is directly taken off from a compressor stage.

3. A gas turbine according to claim 1, characterized in that the cooling air is indirectly taken off from a compressor stage.

4. A gas turbine with a rotor shaft and combustion chamber means according to claim 1, characterized in that the heat-absorbing part of the heat-exchanger means is arranged in an annular space between the rotor shaft and the combustion chamber means, said annular space being in communication, on the one hand, with compressor outlet diffusor means and, on the other, with rotor blade means.

5. A gas turbine with several turbine stages according to claim 4, characterized in that said rotor blade means are part of at least the first turbine stage.

6. A gas turbine according to claim 4, characterized in that the heat-exchanger means includes a heat-transferring part giving off heat which is arranged at the air inlet of the compressor means.

7. A gas turbine according to claim 4, for a ducted fan-jet engine, characterized in that the heat-exchanger means includes a heat-transferring part giving off heat whichds arranged in a bypass channel means of the jet engine.

8. A gas turbine according to claim 4, with a circulating pump means for the closed circulatory system, characterized in that the minimum pressure of the cooling medium is maintained by a charging pump means operatively connected with the circulatory system.

9. A gas turbine according to claim 8, characterized in that an equalization tank means is connected to the circulatory system.

10. A gas turbine according to claim 9, characterized by a warning device which becomes operable when the pressure drops below a predetermined pressure.

11. A gas turbine according to claim 10, characterized in that the warning device becomes operative by illumination of 5 a warning lamp.

12. A gas turbine according to claim 1, characterized in that the heat-exchanger means includes a heat-transferring part giving off heat which is arranged at the air inlet of the compressor means.

13. A gas turbine according to claim 1, for a ducted fan-jet engine, characterized in that the heat-exchanger means includes a heat-tranferring part giving off heat which is arranged in a bypass channel means of the jet engine.

14. A gas turbine according to claim 1, with a circulating pump means for the closed circulatory system, characterized in that the minimum pressure of the cooling medium is maintained by a charging pump means operatively connected with the circulatory system.

15. A gas turbine according to claim 14, characterized in that an equalization tank means is connected to the circulatory system.

16. A gas turbine according to claim 15, characterized by a warning device which becomes operable when the pressure drops below a predetermined pressure.

Claims

1. A gas turbine for aircraft having a compressor means and aircooled turbine blade means whose cooling air is taken off from a compressor stage, characterized by a heat-exchanger means with closed circulatory system whose heat-absorbing part is arranged in a cooling air channel means between the compressor means and a turbine rotor means.

7. A gas turbine according to claim 4, for a ducted fan-jet engine, characterized in that the heat-exchanger means includes a heat-transferring part giving off heat which is arranged in a by-pass channel means of the jet engine.

11. A gas turbine according to claim 10, characterized in that the warning device becomes operative by illumination of a warning lamp.

13. A gas turbine according to claim 1, for a ducted fan-jet engine, characterized in that the heat-exchanger means includes a heat-tranferring part giving off heat which is arranged in a by-pass channel means of the jet engine.