Smooth Turbine Maps - GasTurb

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Smooth Turbine Maps

Computer programs that calculate the performance of gas turbines or piston engines with turbocharger need as input a description of the turbine maps (sometimes called turbine characteristics). These maps are either calculated or derived from a turbine rig test.

The turbine maps are needed in performance calculation programs in a special format. To produce this format "by hand" is a cumbersome task that takes quite much time because of the scatter in the data. Moreover, the data from the turbine rig test usually are not evenly distributed over the tested speed range or the distance between speed lines is big. Interpolation and extrapolation of the measured data is required.

The program Smooth T is a tool that quickly produces high quality turbine maps from measured data. Such maps can be used not only for performance calculations. One can also evaluate small differences between different turbine variants, for example. Moreover, the effects of tip clearance, re-staggered blades and vanes, cooling air injection etc. can be quantified at all points of the map.

The accuracy of the turbine map representation is very important for precise cycle calculations. Remember, that 1% error in low pressure turbine efficiency can result for a high bypass turbofan engine more than 1% error in specific fuel consumption! It can easily happen, that such an error is introduced into the cycle calculation by use of a low quality turbine map. T
he interpolation of data is prone to errors if the data are scattered or if there are not enough speed lines in the map.

Smooth T is not only a valuable tool for dealing with measured data. It can also be used to check the quality of any turbine map. One can use, for example, existing turbine maps as input. Various cross plots offered by the program allow a judgment whether the map is a reasonable description of turbine physics or not. Deficiencies can be corrected and physical meaningful interpolations and extrapolations of the map are possible.

Instead of genuine measured data, which seldom are available outside industry and research facilities, one can also take data from figures published in literature. Even relativized turbine map data can be used as input.

The output of the program is tabulated data with the same number of points for all speed lines. These data are suited as input into performance programs simulating gas turbines or turbocharged piston engines.

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