Machining of slot in turbine blades of axial flow turbines to provide flow path between pressure and suction surfaces is discussed. Slot configuration and improvements in blade performance are described. Diagram of blade slot to show geometry of modification is included

Taylor, W. E.

English

NASA Technical Reports Server

August 1972
	
B72iO484 
NASA TECH BRIEF 
Lewis Research Center 	
_4V 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Slot Configuration for Axial-Flow Turbomachinery Blades 
Figure 1. 
A slot, machined to provide a flow path between the 
pressure and suction surfaces, has been found to improve 
the range of operation and flow turning characteristics of 
hydrofoils arranged in various cascade configurations, 
simulating axial-flow blading geometries. Although slots 
have often been proposed to extend compressor blade 
operating ranges, in practice the slots have seldom 
achieved the objectives of increasing either the operating 
range or the flow turning angles. A slot geometry achiev-
ing these objectives, in a two-dimensional cascade, has 
recently been developed. 
The 8-degree converging-wall slot geometry, shown in 
Figure 1, uses a 16.7-percent chord radius (R) at the slot 
exit on the suction surface, a 1.67-percent chord slot lip 
radius (r) at the slot inlet on the pressure surface, a 
1.57-percent chord slot width (W) at the suction surface, 
and the slot centerline was located at the 45 percent 
chordal station (Z) with an angle of 23 0 between the 
slot centerline and the tangent to the blade surface. 
Blading which uses this slot geometry was tested in a
two-dimensional cascade. The improvements in turning 
angle (0) and loss coefficient () performance of this 
slot with the indicated cascade configuration are shown 
in Figure 2. The results show that the slotted blade 
turning angles increase linearly with increasing incidence 
angle. Slotted blade loss coefficients, although higher 
than those for the unslotted blade within the minimum 
loss region, are significantly lower at higher incidence 
angles. Thus, these slotted blades have a greater range of 
incidence angle operation. The improvements in perform-
ance obtained from the slots appear to be most signifi-
cant when the slotted blades are arranged in low solidity 
cascades. 
Notes: 
1. The following documentation may be obtained from: 
National Technical Information Service 
Springfield, Virginia 22151 
Single document price $11.50 
(or microfiche $0.95) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
(continued overleaf) 
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19720000483 2020-03-17T03:40:28+00:00Z
36	 0.10 
32	 0.09 
28	 0.08
Turning 
Angle 24 0.07 
3 20 0.06 
. 16 0.05 
C 
a 0 
.E 12
- 
0.04 
—J 
I-.
8 0.03
4	 0.02 
0	 0.01 
-4	 0
Loss
Coefficient 
LEGEND: 
Unslotted 
Slotted ---- 
- -20 -16	 -12	 -8	 -4	 0	 4	 8 
Incidence Angle-Degrees 
Figure 2. 
Reference: NASA CR.72870 (N72-24366),	 Patent status: 
Systematic Two-Dimensional Cascade Tests,
	
No patent action is contemplated by NASA. 
Vol. 3 - Slotted Double Circular-Arc Hydrofoils 
2. Techniàal questions may be directed to:
	 Source: W. E. Taylor of 
Technology Utilization Officer
	 United Aircraft Research Labs. 
Lewis Research Center
	 under contract to 
21000 Brookpark Road
	 Lewis Research Center 
Cleveland, Ohio 44135
	 (LEWA 1572)

Reference: B72-10484 
B72-10484 Category 07 


Slot configuration for axial-flow turbomachinery blades

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server