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Introduction
Whenever you turn on a light-switch in your home, there is a strong likelihood that those electrons were generated by a gas turbine combined cycle (GTCC) power plant. These jet-engines-on-the-ground represent the most efficient conversion of natural gas into electricity. In April 2016, under the auspices of the Guinness Book of World Records, a 9HA.01 GTCC set a world record for combined cycle efficiency of 62.22%. Achieving this new record, and setting new ones in the years to come, involves the science and inventions of hundreds of engineers.
H Class Gas Turbine Heritage And Evolution Of 7/9HA Gas Turbines
Gas turbine technology level is commonly identified by letter designation, with higher letters representing increased combustion temperatures and higher efficiencies. Development of H-class technology began in the early 1990s leading to the first commercial operation (COD) in 2003. This original H-class gas turbine pioneered many technologies, including the 4-stage, steam-cooled turbine section and 4 stages of variable guide vanes at the compressor inlet.
Experience and knowledge gained from operation and maintenance of the original GE H-machines paved the way for a new set of H-class products, designated the 7HA and 9HA. The 7/9HA gas turbine hot gas path is entirely air-cooled, facilitated by technological advances in turbine cooling, sealing, materials, and coatings. The "H" signifies H-class firing temperature with the addition of'A' denoting air-cooling.
The 7HA and 9HA are speed and geometric scales with factors of 0.83 (versus 9HA) and 1.2 (versus 7HA), respectively. The 7HA serves the 60 Hz market while the 9HA serves the 50 Hz market. Scaling based upon this approach has been routinely applied for industrial gas turbines, including the 7/9E's and 6/7/9FS offered by GE Power.
The 7/9HA family of gas turbines offers two output sizes for both 7HA and 9HA The ".02's" are flow scales of the ".01s". The process of flow scaling can be summarized by increasing compressor inlet and turbine exit annulus areas to accommodate higher air flow with resultant increase in power output. Pressure ratio is increased to maintain aerodynamic flow function in the mid-to-later compressor and first and second turbine stages. Overall length increases by about one meter for both the 7HA.02 and 9HA.02. Fuel supply capability and fuel nozzle sizing are increased to maintain...