METHOD CONTROLLING COOL AIR FLOW OF GAS TURBINE, SYSTEM FOR INJECTING AIR TO RELEVANT TURBINE

摘要

PURPOSE: A method is provided to modulate pressure of a turbine constitutive element such as a turbine outside wall cavity, by controlling a cooling air flow. CONSTITUTION: The pressure at which cooling and purge air is supplied to the turbine outer side wall cavities is modulated, based on compressor discharge pressure(Pcd), thereby to generally maintain the back flow margin(BFM) so as to minimize excessive leakage and the consequent performance deterioration. The air pressure within the third stage outer side wall cavity and the air pressure within the fourth stage outer side wall cavity are each controlled to a respective value that is a respective prescribed percentage of the concurrent compressor discharge pressure. The prescribed percentage is determined from a ratio of the respective outer side wall pressure to compressor discharge pressure at Cold Day Turn Down(CDTD) required to provide a prescribed back flow margin.