METHOD FOR CONTROLLING A GAP MINIMIZATION OF A GAS TURBINE

Abstract

A method for controlling a gap minimization for an adjustable gap between a rotor and a housing of a gas turbine carried out on the basis of a correlation extracted from simulation data. If the actual value (P.sub.I) lies below the lower threshold (P.sub.U), the gap minimization is deactivated, whereas if the actual value lies above the upper threshold (P.sub.O), the gap minimization is activated. The gap minimization is activated between the thresholds (P.sub.U, P.sub.O) if the actual value lies above the threshold (P.sub.G) but is deactivated if the actual value (P.sub.I) lies below the threshold (P.sub.G).

Claims

1. A method for controlling a gap minimization of an adjustable gap between a rotor and a housing of a gas turbine, wherein the gas turbine comprises a gap-adjusting device, in particular a hydraulic gap-adjusting device, the method comprising: with the aid of a simulation program, the operation of the gas turbine with different parameter settings is modeled and a simulation data set is prepared which contains the dependence of the gap size on an operating parameter, on the basis of the simulation data set, a lower threshold (P.sub.U) and an upper threshold (P.sub.O) for the operating parameter are specified, furthermore, for a transition region (M) between the lower threshold (P.sub.U) and the upper threshold (P.sub.O), a correlation (F) between the operating parameter and a maximum value (P.sub.MAX) of the operating parameter is extracted from the simulation data set, during operation of the gas turbine, an actual value (P.sub.I) of the operating parameter is continuously determined and compared with the lower threshold (P.sub.U) and the upper threshold (P.sub.O), and the maximum value (P.sub.MAX) of the actual value (P.sub.I) is determined over a specified time period, wherein, in the comparison of the actual value (P.sub.I) with the lower threshold (P.sub.U) and the upper threshold (P.sub.O), if the actual value (P.sub.I): lies below the lower threshold (P.sub.U), the gap minimization is deactivated, lies above the upper threshold (P.sub.O), the gap minimization is activated, lies in the transition region (M), a limit value (P.sub.G) for the operating parameter is determined with the aid of the maximum value (P.sub.MAX) from the specified time period using the correlation (F) and the gap minimization is activated if the actual value (P.sub.I) lies above the limit value (P.sub.G) and deactivated if the actual value (P.sub.I) lies below the limit value (P.sub.G).

2. The method as claimed in claim 1, wherein there is used as the operating parameter the relative power (P.sub.REL), which is normalized to the nominal power of the gas turbine.

3. The method as claimed in claim 1, wherein the time period in which the maximum value (P.sub.MAX) is determined is between 20 minutes and 3 hours, in particular between 30 min and 90 min.

4. The method as claimed in claim 2, wherein the lower threshold (P.sub.U) lies at a relative power (P.sub.REL) between 30% and 45%.

5. The method as claimed in claim 4, wherein the upper threshold (P.sub.O) lies at a relative power (P.sub.REL) between 50% and 65%.

6. The method as claimed in claim 5, wherein, after a fall in the relative power (P.sub.REL) which is followed by a rise in the relative power (P.sub.REL), the gap minimization is activated with a time delay if the actual value (P.sub.I) exceeds the limit value (P.sub.G).

7. The method as claimed in claim 6, wherein multiple stages for the maximum value (P.sub.MAX) are defined between the lower threshold (P.sub.U) and the upper threshold (P.sub.O), wherein only the highest stage exceeded by the maximum value (P.sub.MAX) in the time period is taken into consideration for the activation or deactivation of the gap minimization.

8. The method as claimed in claim 1, wherein the correlation between the limit value (P.sub.G) and the maximum value (P.sub.MAX) is predefined.

9. The method as claimed in claim 8, wherein a correlation between the limit value (P.sub.G) and the maximum value (P.sub.MAX) is predefined for each stage.

10. The method as claimed in claim 1, wherein the correlation between the limit value (P.sub.G) and the maximum value (P.sub.MAX) is determined by computation.

11. The method as claimed in claim 1, wherein the method is carried out continuously during operation of the gas turbine.

12. A control device for carrying out the method as claimed in claim 1, comprising: a gap-adjusting device, in particular a hydraulic gap-adjusting device, and means for determining the actual value of the operating parameter.

13. A gas turbine comprising: a control device as claimed in claim 12.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] An exemplary embodiment of the invention will be described in greater detail with reference to a drawing, in which:

[0037] FIG. 1 shows the division of the relative power of a gas turbine into three regions in respect of the HCO activation, and

[0038] FIG. 2 shows a detail of the course of the relative power of the gas turbine over time.

[0039] In the figures, the same reference numerals have the same meaning.

DETAILED DESCRIPTION OF INVENTION

[0040] FIG. 1 shows a graphical representation of the three power regions into which the power of a gas turbine, not shown in greater detail, having a gap-adjusting device according to the novel HCO logic controller is divided and which is characterized by different operating regimes. The gap-adjusting device, which in particular is hydraulically driven, is part of a control device, not shown in greater detail here, which communicates by data connections with sensors, likewise not shown, which monitor the operation of the gas turbine. On the X-axis there is plotted the relative power P.sub.REL, which is formed by the current power, which is normalized by the nominal power of the gas turbine. On the Y-axis there is plotted the maximum value of the relative power P.sub.MAX of the gas turbine. The three regions U, M and O on the X-axis are separated from one another by a lower threshold P.sub.U and an upper threshold P.sub.O. Between zero and the lower threshold P.sub.U, the power region is marked U. Above the upper threshold P.sub.O, the power region is marked O. Between the lower threshold P.sub.U and the upper threshold P.sub.O there is the middle transition region M, in which a limit value P.sub.G lies. The thresholds P.sub.U and P.sub.O are machine-specific and are stored in the controller of the gas turbine, which is contained in a control device, not shown. For example, P.sub.U=40% and P.sub.O=60%. These numerical values may optionally also be changed.

[0041] The line F, which extends over the transition region M, shows the dependence of the limit value P.sub.G on the maximum value P.sub.MAX. In the exemplary embodiment shown, this dependence is stored in a table which the controller is able to access. The table is in turn based on a simulation data set which was generated by means of a simulation program or digital twin for this turbine type.

[0042] The decision whether the HCO is activated or deactivated, or remains active or inactive, is based on the evolution of an actual value P.sub.I of the relative power P.sub.REL. For this purpose, the maximum value P.sub.MAX of the actual value P.sub.I (see FIG. 2) is recorded for a time period which, for example, always corresponds to the last hour. The time period is likewise stored in the controller and is machine-specific. The time period can also be shorter than 1 hour (e.g. the measurements of the relative power P.sub.REL from the last 45 minutes are used) or also longer (e.g. 90 min).

[0043] If the actual value P.sub.I lies in the lower region U beneath the lower threshold P.sub.U, the controller deactivates the gap minimization or, if the gap minimization is already inactive, it remains deactivated.

[0044] If the actual value P.sub.I lies in the upper region O above the upper threshold P.sub.O, the controller activates the gap minimization or, if the gap minimization is already active, it remains activated.

[0045] In the transition region M, the gap minimization is activated or deactivated depending on whether the actual value P.sub.I of the relative power P.sub.REL is in the region M below the limit value P.sub.G or in the region M above the limit value P.sub.G. The limit value P.sub.G, as already explained, can be derived on the basis of the correlation (F), stored in the controller, from the maximum value P.sub.MAX of the maximum power P.sub.MAX in the last hour.

[0046] In order to simplify the detection of the maximum value P.sub.MAX, multiple stages for the maximum value P.sub.MAX can additionally be defined on the Y-axis, wherein only the highest stage exceeded by the maximum value P.sub.MAX in the last hour is taken into consideration for the activation or deactivation of the gap minimization. For example, between 3 and 10 such stages can be defined, which stages can also be of different sizes. In particular, the line F looks slightly different for each stage, that is to say the predefined or calculated correlation between the limit value P.sub.G and the maximum value P.sub.MAX can vary from stage to stage.

[0047] In addition, a further barrier can be incorporated in the HCO, which blocks HCO activation for 15 min, for example. The barrier takes effect in particular following a considerable load or power rise in the transition region M or in the upper region O which follows a considerable load or power drop in the lower region U.

[0048] This case is shown in FIG. 2, in which the relative power P.sub.REL is plotted over time t. Up to time t.sub.1, the actual value P.sub.I is substantially constant and lies in the upper power region O, in which the HCO is active. Between t.sub.1 and t.sub.3, P.sub.I falls rapidly until a value below the lower threshold P.sub.U is reached. When the power falls below the limit value P.sub.G in the transition region M at time t.sub.2, gap minimization is deactivated. Between t.sub.3 and t.sub.4, the actual value P.sub.I remains in the lower region U and the HCO thus remains inactive. Between t.sub.4 and t.sub.7, the P.sub.I increases constantly, wherein at time t.sub.5 the limit value P.sub.G is exceeded again. However, this does not trigger activation of the HCO at t.sub.5, but gap minimization takes place only after, for example, a further 15 min, at time t6, although the actual value P.sub.I lies in the region M the entire time. At time t.sub.7, the actual value P.sub.I is again at the level of the starting state of the gas turbine according to FIG. 2.

[0049] If the actual value P.sub.I were to fall again, for example, after t.sub.4 before activation of the HCO, this would under certain circumstances influence P.sub.MAX from the last hour, which could in turn lead to a new limit value P.sub.G.