Control system and method for controlling a gas turbine engine during transients
A control system and method for a gas turbine engine are provided A controller ( 40 ) is responsive to at least one parameter to control an air-to-fuel ratio. The parameter may be a measured engine exhaust temperature from a temperature sensor ( 42 ). During a transient, such as a ramping condition of the engine, a measured value of such parameter may have a time lag affecting one or more control settings during the transient condition. The controller is programmed to predictively determine a bias for the measured value of the parameter to correct such control settings and avoid combustion instabilities and high emissions during such transient conditions.
1. A control system for a gas turbine engine comprising:
a controller responsive to at least one parameter to control an air-to-fuel ratio, wherein during a transient condition of the engine, a measured value of said at least one parameter comprises a time lag affecting at least one control setting during the transient condition of the engine, wherein the controller is programmed to predictively determine a bias to correct said at least one control setting;
wherein a determination of the bias is based at least in part on a ramp rate of the engine during the transient condition;
wherein said controller provides control that in part is based on engine exhaust temperature measurements and said at least one parameter comprises a measured engine exhaust temperature;
wherein a determination of the bias is based on the time lag determined by the difference between the idealized engine exhaust temperature response and the measured engine exhaust temperature; and
further comprising inlet guide vanes to control inlet air flow to a compressor, wherein said at least one control setting comprises a control setting to position said inlet guide vanes during the transient condition of the engine.
2. The control system of claim 1 , wherein the time lag is based on comparing the measured engine exhaust temperature to an idealized engine exhaust temperature response.
3. The control system of claim 1 , wherein the bias is applied to a steady-state exhaust temperature value at a present engine condition.
4. The control system of claim 1 , wherein a determination of the bias is based on the following equation:
Texh bias,1 =a ×( MW rate ×Δt lag ×( Texh SS,1 −Texh SS,2 ))+ b
where,
Texh bias,l =bias to a steady-state exhaust temperature (Texh) value at a present engine condition,
Texh SS,1 =the steady-state Texh value at the present engine condition,
Texh SS,2 =a steady-state Texh value at a target engine condition,
MW rate =ramp rate of the engine,
Δt lag =value of the lag time,
a =a proportionality factor, and
b =a site-specific constant.
5. The control system of claim 1 , further comprising a fuel system to control at least one fuel flow to a combustor, wherein said at least one control setting further comprises a demand for said at least one fuel flow.
6. The control system of claim 1 , further comprising a bias adjustor configured to adjust the bias as a function of ambient temperature.
7. The control system of claim 1 , further comprising a bias adjustor configured to adjust the bias as a function of engine load.
8. The control system of claim 1 , further comprising a bias adjustor configured to adjust the bias as a function of ambient temperature and/or engine load.
9. A method for controlling a gas turbine engine, the method comprising:
controlling an air-to-fuel ratio with a controller responsive to at least one parameter;
measuring a value of said at least one parameter, which during a transient condition of the engine comprises a time lag affecting at least one control setting during the transient condition of the engine; and
predictively determining a bias to correct said at least one control setting; wherein the determining of the bias is based at least in part on a ramp rate of the engine during the transient condition;
wherein said controlling comprises controlling that in part is based on engine exhaust temperature measurements and said at least one parameter comprises a measured engine exhaust temperature;
wherein the determining of the bias is based on the time lag determined by the difference between the idealized engine exhaust temperature response and the measured engine exhaust temperature; and
further comprising controlling inlet air flow to a compressor with inlet guide vanes, wherein said at least one control setting comprises a control setting to position said inlet guide vanes during the transient condition of the engine.
10. The method of claim 9 , wherein the time lag is based on comparing the measured engine exhaust temperature to an idealized engine exhaust temperature response.
11. The method of claim 9 , further comprising applying the bias to a steady-state exhaust temperature value at a present engine condition.
12. The method of claim 9 , wherein the determining of the bias is based on the following equation:
Texh bias,1 =a ×( MW rate ×Δt lag ×( Texh SS,1 −Texh SS,2 ))+ b
where,
Texh bais,1 =bias to a steady-state exhaust temperature (Texh) value at a present engine condition,
Texh SS,1 =the steady-state Texh value at the present engine condition,
Texh SS,2 =a steady-state Texh value at a target engine condition,
MW rate =ramp rate of the engine,
Δt tag =value of the lag time,
a =a proportionality factor, and
b =a site-specific constant.
13. The method of claim 9 , further comprising controlling at least one fuel flow to a combustor, wherein said at least one control setting further comprises a demand for said at least one fuel flow.
14. The method of claim 9 , adjusting the bias as a function of ambient temperature.
15. The method of claim 9 , adjusting the bias as a function of engine load.