| 摘要 |
A trim system reduces NOx output from a cannular gas turbine by trimming fuel flow rates to equalize the fuel-air ratio in each combustor can. The system includes a main valve fluidly connected to the fuel inlet of each can and a trim valve fluidly connected to each fuel inlet in parallel with the main valve. Each trim valve has a flow resistance which is about 30-100 times greater than the flow resistance of each main valve. A controller is provided for controlling the opening of the trim valves in response to the level of NOx emitted from the gas turbine. The controller receives a signal corresponding to the NOx emissions from a NOx sensor and outputs suitable control signals to the trim valves. In one preferred control scheme, the controller sequentially perturbs the fuel flow rate to each can and monitors the resulting changes in NOx emissions. The controller establishes influence coefficients for each combustor can which are defined as the ratio of the change in NOx output to the change in fuel flow rate to that can. Baseline fuel flow adjustments are then made in the direction of negative influence coefficients. This is continued until NOx emissions are minimized.
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