Method for starting up a gas turbine engine of a combined cycle power plant

Abstract

The invention relates to a method for starting up a gas turbine engine of a combined cycle power plant. The method includes applying load to the gas turbine engine and increasing the load until a predetermined combustor firing temperature is reached, while keeping the adjustable inlet guide vanes in a start position adapted to reduce the mass flow of air into the compressor; further increasing the load of the gas turbine engine while opening the adjustable inlet guide vanes and keeping the predetermined combustor firing temperature constant until the inlet guide vanes reach an end position adapted to increase the mass flow of air into the compressor; further increasing the load of the gas turbine engine while keeping the adjustable inlet guide vanes in the end position until a predetermined load of the gas turbine engine is reached.

Claims

1. A method for starting up a gas turbine engine of a combined cycle power plant, the gas turbine engine including a compressor, a combustor and a turbine, the compressor providing compressed air to the combustor for combustion with a fuel to produce a working fluid and the turbine receiving the working fluid to produce power; the compressor comprising adjustable inlet guide vanes, the adjustable inlet guide vanes being adjustable between a fully closed position for minimizing the mass flow of air into the compressor and a fully open position for providing the maximum mass flow of air into the compressor; wherein the method comprises the steps of: step 1: applying load to the gas turbine engine and increasing the load until a predetermined combustor firing temperature is reached, while keeping the adjustable inlet guide vanes in a start position adapted to reduce the mass flow of air into the compressor, whereby the predetermined combustor firing temperature is chosen to be an emission-compliant temperature, step 2: further increasing the load of the gas turbine engine while opening the adjustable inlet guide vanes and keeping the predetermined combustor firing temperature constant until the inlet guide vanes reach an end position adapted to increase the mass flow of air into the compressor, step 3: further increasing the load of the gas turbine engine while keeping the adjustable inlet guide vanes in the end position until a predetermined load of the gas turbine engine is reached.

2. A method according claim 1, wherein the predetermined combustor firing temperature is between 1000° C. and 1850° C.

3. A method according to claim 1, wherein in step 3 the predetermined load is a base load of the gas turbine engine.

4. A method according to claim 1, wherein in step 1 the start position of the adjustable inlet guide vanes is the fully closed position.

5. A method according to claim 1, wherein in step 3 the end position of adjustable inlet guide vanes is the fully open position.

Description

(1) These and other advantages of the invention will be more apparent from the following description in view of the drawings that show:

(2) FIG. 1 a schematic diagram of a combined cycle power plant;

(3) FIG. 2 a new start-up profile of a gas turbine engine according to the present invention in a diagram showing the power of gas turbine engine over the exhaust temperature;

(4) FIG. 3 in a diagram two new start-up profiles according to the present invention in a diagram showing the exhaust temperature over the gas turbine power of the gas turbine engine; and

(5) FIG. 4 in a diagram the development of a combustor firing temperature over the power of a gas turbine engine for two new start-up profiles according to the present invention.

(6) Referring to FIG. 1 an abstract, schematic drawing of a combined cycle power plant 2 is shown. In the figure a gas turbine engine 4 and a steam turbine engine 6 are shown.

(7) The gas turbine engine 1 comprises an inlet 8, a compressor 10, a combustor 12 and a turbine 14. A fuel 16 is supplied to the combustor 12 as indicated by an arrow. A fluid which is exhausted by the turbine 14 is identified as exhaust fluid 18.

(8) The exhaust fluid 18 is provided to a heat exchanger 20, in particularly a heat recovery steam generator (HRSG). In the HRSG 20 all of the heat recovered from the exhaust fluid 18 is converted into high pressure steam 22. This steam 22 is used to drive the steam turbine engine 6 which converts the energy of the steam to mechanical energy, which in its turn is converted into electrical power.

(9) The gas turbine engine 4 is driving a first generator 24, so that the mechanical load on the gas turbine engine 4 is converted in the first generator 24 into electrical power. The steam turbine engine 6 is driving a second generator 26. Alternatively mechanical components could be driven.

(10) As an alternative to the power plant design shown in FIG. 1, the combined cycle power plant 2 may be designed as a single shaft combined cycle having the gas turbine engine 4 and the steam turbine engine 6 on one shaft line, both driving a common generator.

(11) A steam exhaust 28 passes through a condenser 30 and water 32 coming from condenser 28 is fed into the HRSG 20.

(12) The steam turbine engine 6 comprises for example a low, a medium and a high steam turbine section which are not shown in FIG. 1.

(13) A control unit 34 is simply indicated by a rectangle. A single or several control units may be present. The control unit 34 may control all shown components or only a subset.

(14) In FIG. 2 the method for starting up a gas turbine engine 4 of a combined cycle power plant 2 is visualized by means of a diagram showing the load P [%] as percent ratio of the base load generated by gas turbine engine 4 over an exhaust temperature T.sub.EXH [° C.] of the turbine 14. The dashed lines within the diagram represent isothermal lines for different firing temperatures T.sub.F in the combustor 12.

(15) Starting at minimum load in the first step S.sub.1 the profile follows the traditional path, whereby adjustable inlet guide vanes located in the compressor 10 are kept in the fully closed position. At low loads, the CO emission is very high, this is why it is preferable to keep the combustion temperature high and to minimize the exhaust flow 18 by keeping the adjustable inlet guide vanes closed. In this case, the start position of the adjustable inlet guide vanes corresponds to the fully closed position, in which the mass flow of air 8 to the compressor 10 is minimized.

(16) When firing temperature T.sub.F of about 1200° C. is reached at a turbine load between 10% to 20% of the base load, in the second step S.sub.2 the firing temperature T.sub.F is kept constant and the load on the gas turbine engine 4 is increased up to about 40% of the base load, while the adjustable inlet guide vanes are opened. This results in a decrease of the exhaust temperature T.sub.EXH from about 500° C. to about 375° C. Thus, the thermal stress on the HRSG 20 components is alleviated and at the same time the firing temperature T.sub.F remains CO-compliant at the level of about 1200° C.

(17) Once an end position of the adjustable inlet guide vanes is reached at a firing temperature=1200° C., whereby in the example shown in FIG. 2 the end position corresponds to a fully open position for providing the maximum mass flow of air 8 into the compressor 10, in the third step S.sub.3 the load of the gas turbine engine 4 is increased. In the third step S.sub.3 the gas turbine engine 4 reaches its base load. The power of the gas turbine engine 4 increases to 100% load, the firing temperature T.sub.F reaches approximately 1850° C. and the exhaust temperature T.sub.EXH is about 680° C.

(18) The profile of the temperature development of the method as shown in FIG. 2 is characterized by “sliding backwards” along the constant firing temperature T.sub.F in the range between about 15% and 40% of the base load, which results in a reduction of the exhaust temperature T.sub.EXH with increasing power, while the firing temperature T.sub.F is kept CO-compliant.

(19) A profile of the temperature development of the method according to the present invention is shown in FIG. 3, whereby the x-axis represents the engine load P [%] as percent ratio of the base load of the gas turbine engine 4 and the y-axis represents the exhaust temperature T.sub.EXH [° C.]. The flexibility of the new loading strategy is illustrated by two different firing temperatures T.sub.F (1200° C. and 1400° C.) in step S.sub.2. Depending on the CO emission regulation one of these firing temperatures T.sub.F (or a different CO-compliant firing temperature T.sub.F) may be applied, resulting in an offset of the exhaust temperature profile while startup.

(20) The corresponding relationship of the firing temperature T.sub.F [° C.] and the gas turbine load P [%] as percent ratio of the base load is shown in FIG. 4, whereby the horizontal lines show step S.sub.2 of the loading strategy—the maintenance of a constant firing temperature T.sub.F.