DEVELOPMENT OF NEW CASCADES WITH PROFILES OF VARIABLE GEOMETRY FOR APPLICATION IN INLET AND EXIT GUIDE VANES OF SWIRL CONTROLLED TURBOMACHINES .2.

The control of axial flow turbomachines by variable geometry inlet and exit guide vanes is a very economical control method with regard to i nvestment and maintenance costs. On the other side, the method in its present state of development is not as good (in terms of efficiency) a s some of the other, more expensive methods - the method of variable g eometry rotors for example. In order to develop the effectiveness of t he variable stator method to the same level as that of the variable ro tor method, new inlet and exit guide vanes have to be designed for axi al flow machines like pumps, blowers and compressors. The present work , published in the last and in this issue of the periodical (part I an d II), describes theoretical and experimental investigations having be en accomplished to develop new guide vane and stator cascades with opt imizes profiles having extremely extented low loss regions compared to those of the usual cascades with conventional profiles. On the theore tical side two direct design methods are introduced, methods by which inlet and exit cascades with special profiles can be generated and opt imized with regard to a maximum working range with minimum losses. In case of the inlet guide vanes these are unstaggered cascades of profil es with mechanical flaps at the rear ends and in case of the exit guid e vanes these are tandem cascades having variable stagger blades in th e first blade row. On the experimental side the measured results for t wo newly designed inlet and exit cascades are presented and compared t o the pertinent results of conventionally designed cascades. Thereby t he most important results of these investigations become evident, name ly: With the newly developed cascades it is demonstrated that the low loss inlet angle range can be increased by 260% in case of the inlet c ascade, by 150% in case of a single row exit cascade and by 250% in ca se of the double row or tandem exit cascade with variable stagger blad es in the first row.