Steam cooling of gas turbine with backup air cooling.

摘要

A gas turbine power plant in which a mixture of steam and compressed air (18), the mixture (18) being primarily steam, is used to cool the rotating blades (46) and stationary vanes (44) in the turbine section (4). The air is bled from the compressor (1). The flow rate of steam (50) that is mixed into the compressed air (12) is adjusted so to maintain the pressure drop experienced by the compressed air (12) as it flows to the turbine (4) within a predetermined range. Consequently, the steam and air mixture (18) has the same volumetric flow rate as if compressed air (12) alone were being used. Thus, any sudden decrease in steam flow rate will automatically result in an offsetting increase in the flow of compressed air (12) due to the decrease in the line pressure in the common line through which the air and steam flow to the turbine (4). Consequently, no control, isolation or check valves are utilized in the compressed air piping.