OPERATION OF A GAS TURBINE AT A HIGH TEMPERATURE AND GAS TURBINE ASSEMBLY

Abstract

The disclosure relates to a method for operating a gas turbine at a high temperature and to a gas turbine assembly. In the method, a gas turbine having a structural material and a thermal barrier layer disposed on the structural material is cooled down in a decelerated manner after operation at an operating temperature above 1000° C., so that damage to the structural material and/or the thermal barrier layer is minimized. In this way, the gas turbine can be operated permanently at temperatures above 1500° C.

Claims

1. A method of operating a gas turbine at a high temperature, wherein the gas turbine has a structural material and a protective layer disposed on the structural material, and wherein the gas turbine is cooled down in a decelerated manner after operation of the gas turbine at an operating temperature above 1000° C.

2. The method according to claim 1, wherein the decelerated cool-down is performed at a cooling rate (cr) of less than 100 K/s.

3. The method according to claim 1, wherein the protective layer includes zirconium oxide or is produced therefrom.

4. The method according to claim 1, wherein the gas turbine is operated at an operating temperature above 1200° C. before a cool-down.

5. The method according to claim 1, wherein the decelerated cool-down is performed to a temperature below 300° C.

6. The method according to claim 1, wherein a cool-down from the operating temperature to a target temperature is performed without interruption and/or within a time of at most 30 minutes.

7. The method according to claim 1, wherein the temperature of the gas turbine is increased up to the operating temperature in a decelerated manner at least for a period of time.

8. The method according to claim 1, wherein the deceleration of the cool-down is achieved at least in parts by continuously reducing a power of the gas turbine at least for a period of time.

9. The method according to claim 1, wherein the deceleration of the cool-down is achieved at least in parts by preventing an inflow of cold gas into the gas turbine.

10. The method according to claim 1, wherein a cool-down is achieved at least in parts by realizing an inflow of oxygen-reduced or oxygen-free gas into the gas turbine.

11. The method according to claim 1, wherein the gas turbine is a stationary gas turbine and the decelerated cool-down is performed without interruption to a temperature below 400° C.

12. The method according to claim 1, wherein prior to cool-down from an operating temperature between 550° C. and 1100° C. to a temperature below 100° C., the temperature of the gas turbine is increased from the operating temperature to at least 800° C. followed by the decelerated cool-down.

13. The method according to claim 1, wherein a control device is present which is configured such that cool-down is performed by reducing the power of the gas turbine continuously or stepwise.

14. The method according to claim 13, wherein the operation of the gas turbine is switched off when a temperature below 400° C. is reached.

15. A gas turbine assembly for performing a method according to claim 1, comprising a gas turbine and a control device for controlling the gas turbine, wherein the gas turbine comprises a structural material and a protective layer disposed on the structural material, wherein the control device is configured to cool down the gas turbine in a decelerated manner after operation at an operating temperature above 1000° C.

16. A method of operating a gas turbine, the gas turbine comprising a structural material and a protective layer disposed on the structural material, the method comprising: operating the gas turbine at an operating temperature above 1000° C.; and subsequently cooling down the gas turbine in a decelerated manner at a cooling rate of less than 100 K/s.

17. The method according to claim 16, wherein the cooling rate is less than 50 K/s.

18. The method according to claim 16, wherein the protective layer is one of a thermal barrier layer and a corrosion protection layer.

19. The method according to claim 16, wherein the decelerated cool-down starts at the operating temperature.

20. The method according to claim 7, wherein the increase of the temperature is performed at a cooling rate of less than 100 K/s.

Description

[0060] In the following, an exemplary embodiment of the invention is also explained in more detail with reference to figures.

[0061] The figures show:

[0062] FIG. 1: a schematic representation of a part of a gas turbine assembly according to the invention, and

[0063] FIG. 2: particularly advantageous operating conditions for performing the method according to the invention.

[0064] FIG. 1 shows a part of a gas turbine 1 of a gas turbine assembly according to the invention. A structural material 2 is shown, on which a protective layer 3 in the form of a thermal barrier layer is disposed. The thermal barrier layer is disposed directly on the structural material 2, i.e. there is no other layer in between.

[0065] The thermal barrier layer consists of zirconium oxide partially stabilized with yttrium oxide (YSZ). The thermal barrier layer was produced by a thermal spray process or by thermal evaporation in an electron beam evaporator. The structural material consists of a nickel-based superalloy.

[0066] The decelerated cool-down according to the invention excludes damage to the depicted part of gas turbine 1, even in continuous operation above temperatures of 1500° C.

[0067] The thickness ratios of the elements in this schematic representation are merely exemplary and may deviate significantly from this representation if necessary.

[0068] FIG. 2 shows the particularly advantageous safe operating conditions 10 in the area shown at the bottom left. However, higher temperatures can also be advantageous. The cooling rate cr at the decelerated cool-down in K/s is plotted in logarithmic form on the X axis. The surface temperature T.sub.s of the protective layer in ° C. is plotted on the Y axis.

[0069] It can be seen that the gas turbine can be operated in a particularly advantageous manner, i.e. safely and/or permanently and without damage, at cooling rates cr in a wide range between 1 K/s and slightly above 100 K/s up to 1600° C. The particularly advantageous safe operating conditions 10 run up to cooling rates cr of about 150 K/s, wherein lower surface temperatures T.sub.s are necessary in this range. At higher surface temperatures T.sub.s, the described damaging phase transformation 20 takes place, wherein at rapid temperature change and at surface temperatures T.sub.s above 1600° C., in particular the cubic structure 21 is present, and at slow temperature change and at surface temperatures T.sub.s above 1200° C., in particular the monoclinic structure 22 is present.

[0070] At cooling rates cr up to approx. 0.3 K/s, temperatures T.sub.s above about 1200° C. are already damaging. This value increases rapidly up to cooling rates cr shortly below 1, where the described surface temperatures T.sub.s of 1600° C. are already possible.

[0071] At cooling rates cr between about 150 K/s and about 2000 K/s, early delamination 30 occurs, and at cooling rates cr above this, surface degradation 40 occurs. In particular, the cooling rate cr must not be too high at high surface temperatures T.sub.s and the cooling rate cr must not be too low at lower surface temperatures T.sub.s.

LIST OF REFERENCE SIGNS

[0072] Gas turbine 1 [0073] Structural material 2 [0074] Protective layer 3 [0075] Safe operating conditions 10 [0076] Damaging phase transformation 20 [0077] Cubic structure 21 [0078] Monoclinic structure 22 [0079] Early delamination 30 [0080] Degradation 40 [0081] Surface temperature T.sub.s [0082] Cooling rate cr