Method accurately determines actual coolant mass flow rate in cooling passages of rotating turbine blades. Total and static pressures are measured in blade base coolant passages. Mass flow rates are calculated from these measurements of pressure, measured temperature and known area

Liebert, C. H.

Pollack, F. G.

English

NASA Technical Reports Server

Xpril 1975	 B75-10017 
I	 NASA TECH BRIEF 
Lewis Research Center 
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 quest:ons relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington. D.C. 20546. 
A Method for Measuring Cooling Air Flow in

Base Coolant Passages of Rotating Turbine Blades 
E
A flow measuring method has been developed that 
accurately determines the actual coolant mass flow rate in 
the cooling passages of rotating turbine blades. Total and 
static pressures are measured in the blade base coolant 
passages. Mass flow rates are calculated from these 
measurements of pressure, a measured temperature and a 
known area.
STATIC PRESSURE 
,7 TUBE ENDS SEAL 
PROBES—' 
SECTION A-A 
AIRFOIL.,
PRESS E 
111,	 PROBES 
mp! ' A - ­ 	 I 
STATIC 
PRESSURE 
TAP 
BLADE 
BASE 
BLADE COOLING AIR
BLADE INSTRUMENTATION (NOT TO SCALE)
Static pressure is measured with small diameter (0.051 
cm (0.020 in)) taps that are mounted normal to the inside 
of the blade base air passage (see figure). Total pressure is 
sensed with two small diameter (0.051 cm (0.020in)) 
holes spaced 0.127 cm (0.050 in) apart in 0.0813 cm 
(0.032 in) tubing in each air passage. These tubes are 
centered in the air flow passages with the axes of the holes 
placed parallel to the direction of flow. 
The sensed pressures are ducted to variable reluctance 
differential pressure transducers mounted near the shaft 
centerline. These rotating transducers convert the pneu-
matic pressures into electrical signals that are transferred 
by a slip ring assembly to stationary recording equipment. 
The pressure differences indicated by the transducers are 
corrected for temperature, rotational effects on the air 
columns contained by the ducting, and, when relevant, 
rotational effects on the transducers. Mass flow rates are 
calculated from these corrected pressure differences. Shaft 
speeds of 0-9000 rpm and air mass flow rates of 0.0035 to 
0.039 kilogram per second (0.0077 to 0.085 lbm/sec) 
have been measured with this system. 
Conventional methods for determining cooling air mass 
flow rates through rotating turbine blades use instrumen-
tation located in the stationary portion of the coolant 
supply system. Coolant system leakages which may occur 
downstream of the measuring station are accounted for 
through use of calibrations and calculations. While it is 
usually possible to calibrate and/or calculate the coolant 
system leakage at cold stationary conditions, it is not 
possible to apply such procedures with a high degree of 
confidence when the turbine component is hot and 
rotating. Therefore, to obtain an accurate determination 
of the coolant flow rate being delivered to a rotating 
cooled turbine blade, it is desirable to make measurements 
at a point which is downstream of all potential points of 
coolant system leakage. 
Individual rotating flow measurements of blade mass 
flow rates using this new method agreed with correspond-
ing stationary flow measurements using a calibrated 
reference orifice within 10 percent at shaft speeds from 0 
to 9000 rpm.
(continued overleaf) 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19750000017 2020-03-19T19:58:24+00:00Z
Notes: 
I. Further information is available in the following 
report: 
NASA TN-D-7697 (N74-25950), Flow Measure-
ment in Base Cooling Air Passages of A Rotating 
Turbine Blade 
Copies may be obtained at cost from: 
Aerospace Research Applications Center 
Indiana University 
400 East Seventh Street 
Bloomington, Indiana 47401 
Telephone: 812-337-7833 
Reference: B75-10017 
2. Specific technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B75-10017 
Patent Status: 
NASA has decided not to apply for a patent. 
Source: C.H. Liebert and F.G. Pollack 
Lewis Research Center
(LEW-1 2433)
S 
B75.10017	 Category 03


A method for measuring cooling air flow in base coolant passages of rotating turbine blades

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