Handbook of Turbomachinery Second Edition Revised - Ventech!

istics. The more accurate the performance maps, the more accurate will be
the overall gas turbine cycle performance predictions. In addition,
instrumentation is also often included on the test rig for flow diagnostic
evaluation of the individual blade rows and localized areas of interest.
For steady-state operation (engine and flight operating conditions
changing very slowly with time), the component maps describe several
performance features. Typical compressor and turbine maps are shown in
Figs. 1and 2. Performance maps are characterized with stage total pressure
ratios plotted as a function of corrected flow rate at different corrected
rotational speeds. As seen, each speed line has a distinctive locus of
performance data. Also included on performance maps are constant
efficiency islands as is shown in Fig. 1. See the final section for a definition
of corrected flow parameters.
Compressor and fan maps also include a stall line. The stall line
identifies the locus of unstable operating conditions with stable operation to
the right of the stall line. The operating regions that include choked flow
through the blade passages are recognized by the vertical speed line
performance characteristics. Referring to the performance map examples, we
see a weak dependence of turbine performance on wheel speed, contrasted
with a relatively strong dependence shown by compressors and fans.
Each turbomachine component performance map is associated with a
specific configuration and flow-path geometry. Blading differences, flowpath
geometric changes, running tip clearance changes, different gaps,
Figure 1 Typical compressor map.
Copyright © 2003 Marcel Dekker, Inc.