Blade group arrangement as well as turbomachine
A blade group arrangement for a turbomachine in order to form a blade-row group, whereby a front blade and a rear blade each form an overlapping area that has a contraction ratio of at least 1.2, and it also relates to a turbomachine having such a contraction ratio between a front blade and a rear blade.
1. A blade group arrangement for a turbomachine in order to form a blade-row group, comprising:
a front blade and a rear blade arranged offset from each other in the axial and circumferential directions and forming an overlapping area running between a pressure side of the front blade and a suction side of the rear blade, the front and rear blades in the overlapping area converging with a contraction ratio KV of KV≧1.2 between an inlet surface D min,1 defined as a smallest distance between a leading edge of the rear blade and the pressure side of the front blade, and an outlet surface D min,2 defined as a further smallest distance between the suction side of the rear blade and the pressure side of the front blade.
2. The blade group arrangement as recited in claim 1 wherein the contraction ratio KV is ≦2.8.
3. The blade group arrangement as recited in claim 1 wherein the contraction ratio KV=1.7.
4. The blade group arrangement as recited in claim 1 wherein the suction side of the rear blade has a greater curvature downstream from the outlet surface D min,2 than upstream from the outlet surface D min,2 .
5. The blade group arrangement as recited in claim 4 wherein the curvature has a maximum ranging from 1.6 to 1.7 times a mean curvature of the suction side of the rear blade.
6. The blade group arrangement as recited in claim 5 wherein the curvature maximum amounts to approximately 5% to 25% of a relative skeleton line length behind the outlet surface D min,2 .
7. A turbomachine comprising at least one blade-row group having a plurality of blade group arrangements as recited in claim 1 .