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On Industrial Gas Turbine Performance
Recently, Texas A&M hosted the 51st Turbomachinery and Pump Symposia in downtown Houston, with thousands attending. It was a hotbed for theoretical and practical turbomachinery discussions. TPS is considered a key forum for the collaboration and discussion of ideas for individuals working in the turbomachinery space worldwide. This article showcases one of several technical sessions held during the event; a more comprehensive report will be found in the November-December 2022 edition of Turbomachinery International Magazine.
Performance of Industrial Gas Turbines, by Burnes and Kurz
Rainer Kurz of Solar Turbines presented Performance of Industrial Gas Turbines. The session focused on how industrial gas turbines are used in many applications as drivers for generators, pumps, and compressors.Historically, the technologies to bring the concept of a gas turbine to a working, useful machine include manufacturing and material capabilities, aerodynamics, and combustion technology.
Gas turbines feature high efficiency, low operating and purchasing cost, emissions, and weight. Fuel and maintenance requirements are relatively low. Kurz spoke on gas turbine use cases, their benefits over other driver types, manufacturing methods, the Brayton Cycle, and aerodynamic considerations. He also explained the different types of industrial gas turbines, such as single and two shaft designs, as well as industrial gas turbines adapted from aircraft engines (aeroderivative).
Industrial gas turbines have performance characteristics that distinctly depend on ambient and operating conditions. Application of these gas turbines, as well as control and condition monitoring, require consideration of site elevation, ambient temperature, relative humidity, speed of the driven equipment, fuel, and load conditions. In the presentation, the reasons for these performance characteristics were explained by considering the performance of individual components, and the interaction between these components. Methods allowing the use of performance data for trending and comparison purposes were discussed. These methods are a key tool in modern condition monitoring systems.
The discussion of the Brayton cycle revealed how much power is used in the gas turbine cycle to power the compressor, how the power generated by the turbine section is divided into the power needed to drive this compressor, and how much is available as useful power output. This type of cycle analysis reveals the impact of compressor pressure ratio and firing temperature on the size and efficiency of the gas turbine.
Aerodynamics were next on the plate. Kurz said, “The key to understanding Turbomachinery is that it is concerned with forcing the movement of air”. Work from the blades is spinning velocity multiplied by the change in velocities of the centrifugal direction i.e., the deflection of gas. The Euler equation then connects thermodynamics to aerodynamics and stipulates that velocity can be directly correlated with enthalpy.
This article is a preview of the upcoming Houston Turbomachinery and Pump Symposium report. For a more detailed overview, see the upcoming November-December 2022 issue.