Supercharged Combined Cycle System With Air Flow Bypass
A system and method for supercharging a combined cycle system includes a forced draft fan providing a variable air flow. At least a first portion of the air flow is directed to a compressor and a second portion of the airflow is diverted to a heat recovery steam generator. A control system controls the airflows provided to the compressor and the heat recovery steam generator. The system allows a combined cycle system to be operated at a desired operating state by controlling the flow of air from the forced draft fan to the compressor and the heat recovery steam generator.
1 . A combined cycle system comprising:
a gas turbine subsystem having a compressor and an output side that provides an exhaust;
a heat recovery steam generation subsystem having an inlet;
an exhaust duct coupled to the gas turbine subsystem and the inlet for transporting the exhaust to the heat recovery steam generation subsystem;
a controllable air stream source that produces an air flow;
a ducting assembly coupled to the controllable air stream source that conveys at least a portion of the air flow to the compressor; and
a bypass coupled to the controllable air stream source and the exhaust duct adapted to selectively convey at least a portion of the air flow to the inlet.
2 . The combined cycle system of claim 1 wherein the controllable air stream source comprises a forced draft fan.
3 . The combined cycle system of claim 2 further comprising a variable frequency drive coupled to the forced draft fan.
4 . The combined cycle system of claim 1 further comprising a flow sensor and a damper valve disposed on the bypass.
5 . The combined cycle system of claim 3 further comprising a control system that controls the variable frequency drive.
6 . The combined cycle system of claim 4 further comprising a control system that receives signals from the flow sensor and controls the damper valve.
7 . The combined cycle system of claim 1 wherein the heat recovery steam generation subsystem comprises a supplemental burner.
8 . A supercharging system comprising:
a forced draft fan providing a variable air flow;
a duct that directs at least a first portion of the variable air flow to a compressor;
a bypass subsystem that diverts at least a second portion of the variable air flow to a heat recovery steam generator; and
a control system coupled to the bypass subsystem and the forced draft fan.
9 . The supercharging system of claim 8 wherein the bypass subsystem comprises a duct, a flow sensor, and a valve.
10 . The supercharging system of claim 8 wherein the control system comprises a control component that controls the variable air flow provided by the forced draft fan.
11 . The supercharging system of claim 8 further comprising a variable frequency drive coupled to the forced draft fan.
12 . The supercharging system of claim 8 further comprising a secondary burner in the heat recovery steam generator.
13 . A method of operating controlling comprising:
determining a first operating state;
determining a desired operating state;
determining a first mass flow quantity of air to be provided to a compressor and a second mass flow quantity of air to be provided to a heat recovery steam generator to achieve the desired operating state;
providing source of controllable air flow;
selectively conveying the first mass flow quantity of air into the compressor; and
selectively conveying the second mass flow quantity of air to the heat recovery steam generator.
14 . The method of claim 13 wherein the method element of providing source of controllable air flow comprises providing a forced draft fan driven by a variable frequency drive.
15 . The method of claim 13 wherein the desired operating state is a state that compensates for output degradation.
16 . The method of claim 13 wherein the method element of selectively conveying a second mass flow quantity of air to the heat recovery steam generator further comprises conveying a second mass flow quantity of air at a temperature and modulating the temperature.
17 . The method of claim 13 further comprising force cooling the first mass flow quantity of air.
18 . The method of claim 13 wherein the desired operating state is a state that provides a predetermined steam flow.
19 . The method of claim 13 wherein the method element of selectively conveying the second mass flow quantity of air comprises conveying the second mass flow quantity of air through a bypass to the heat recovery steam generator.
20 . The method of claim 19 further comprising controlling the second mass flow quantity of air with a valve coupled to the bypass.