Smooth Compressor Maps - GasTurb

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Smooth Compressor Maps

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

The compressor 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 compressor 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 are required.

The program Smooth C is a tool that quickly produces high quality compressor maps from measured data. Such maps can be used not only for performance calculations. One can also the map differences between compressor variants. Moreover, the effects of inter stage bleed, Reynold's number, tip clearance, restaggered blades and vanes, distortion etc. can be evaluated.

The accuracy of the compressor map representation is very important for precise cycle calculations. Remember, that 1% error in compressor efficiency can mean - dependent on engine type - up to 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 compressor map. T
he interpolation of data is prone to error if the data are scattered or if there are not enough speed lines in the map.

However, Smooth C is not only a valuable tool for dealing with measured data. It can also be used to check the quality of any compressor map. One can use, for example, existing compressor maps as input. Various cross plots offered by the program allow a judgment whether the map is a reasonable description of compressor physics or not. Deficiencies can be corrected and physical meaningful interpolation 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 compressor 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 the performance of gas turbines or turbocharged piston engines.

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