Method for operating a combustion device during transient operation

1. A method for operating a combustion device during transient operation, comprising:

feeding the combustion device with a fuel during a transient operation which includes a period having a period length (T) during which the fuel is fed in an amount lower than a designated amount (Mc), where the designated amount (Mc) is an amount below which pulsations start to occur at a level above an operating limit of the combustion device;

defining a limit value (L) for the period length (T); and

regulating fuel feed to keep the period length (T) smaller or equal to the limit value (L).

2. The method of claim 1 , wherein the transient operation is a switch over from operation with a first fuel to operation with a second fuel.

3. The method of claim 2 , wherein the first fuel is a liquid fuel and the second fuel is a gaseous fuel or vice versa.

4. The method of claim 1 , wherein the combustion device is a part of a gas turbine.

5. A method for operating a combustion device during transient operation, comprising:

feeding the combustion device with a fuel during a transient operation which includes a period having a period length (T) during which the fuel is fed in an amount lower than a designated amount (Mc);

defining a limit value (L) for the period length (T);

regulating fuel feed to keep the period length (T) smaller or equal to the limit value (L);

providing a parameter (Bo) that is a function of the period length (T) and fed fuel (Δβ); and

defining the limit value (L) for the period length (T) as a limit value for the parameter; and

wherein the regulating of the fuel feed and period length (T) comprises:

preventing the parameter (Bo) from overcoming the limit value for the parameter.

6. The method of claim 5 , wherein the parameter (Bo) is defined by:

Bo =(α GR ·T )/(2π·Δβ)

wherein

α GR is an averaged linear growth rate of fuel during a fuel feed change Δβ;

T is a period length for the fuel feed Δβ;

β is an energy content of one fuel divided by an energy content of a total supplied fuel;

Δβ=abs(β2−β1) is the difference of β in T.

7. The method of claim 6 , wherein α GR is approximated by:

α GR =f osc /(2π) 2

wherein

f osc is a mean oscillation frequency during a period in a range of the fuel feed Δβ.

8. The method of claim 6 , wherein the limit value is π.

9. The method of claim 5 , wherein the transient operation is a switch over from operation with a first fuel to operation with a second fuel.

10. The method of claim 9 , wherein the first fuel is a liquid fuel and the second fuel is a gaseous fuel or vice versa.

11. The method of claim 5 , wherein the combustion device is a part of a gas turbine.

12. A fuel feed regulator for feeding a combustion device during transient operation, the regulator configured to:

feed the combustion device with a fuel during a transient operation which includes a period having a period length (T) during which the fuel is fed in an amount lower than a designated amount (Mc), where the designated amount (Mc) is an amount below which pulsations start to occur at a level above an operating limit of the combustion device;

define a limit value (L) for the period length (T); and

regulate fuel feed to keep the period length (T) smaller or equal to the limit value (L).

13. The fuel feed regulator of claim 12 , wherein the regulating of the fuel feed and period length (T) comprises:

preventing the parameter (Bo) from overcoming the limit value for the parameter; and

the fuel feed regulator is further configured to:

provide a parameter (Bo) that is a function of the period length (T) and fed fuel (Δβ); and

define the limit value (L) for the period length (T) as a limit value for the parameter.

14. The fuel regulator of claim 12 , wherein the transient operation is a switch over from operation with a first fuel to operation with a second fuel.

15. The fuel regulator of claim 14 , wherein the first fuel is a liquid fuel and the second fuel is a gaseous fuel or vice versa.

16. The fuel regulator of claim 12 , wherein the combustion device is a part of a gas turbine.