Non-contacting pyrometer system optically measures surface temperature distribution on rotating turbine blade, comprising line-by-line scan via fiber optic probe. Each scan line output is converted to digital signals, temporarily stored in buffer memory, and then processed in minicomputer for display as temperature

Buchele, D. R.

Lesco, D. J.

English

NASA Technical Reports Server

August 1974	 B74-10068 
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 questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Rotating Turbine Blade Pyrometer 
S
The Problem: 
Jet engine performance is closely linked to the maxi-
mum operating temperature of the turbine blade material. 
When a blade is constructed with internal blade passages 
and surface perforations for the flow of cooling fluids, the 
surface temperature distribution can show significant 
changes over a distance less than one millimeter. Conven-
tional temperature measuring instrumentation comprises 
thermocouples attached to the blade to obtain tempera-
ture at a moderate number of points. Thermocouple 
installation is complex and time consuming. In those cases 
where turbine blades are of a thin wall or hollow wall 
construction, the installation of many thermocouples may 
have a deleterious effect on the blades. 
The Solution: 
A non-contacting pyrometer system for optically 
measuring surface temperature distribution on a rotating 
turbine blade, comprising, a line-by-line scan via a fiber 
optic probe. Figure 1 depicts the path of scan lines along 
the blade surface. Each scan line output is converted to 
Fig. 1. - Turbine blade surface scanned by 
optical probe.
digital signals, temporarily stored in a buffer memory, and 
then processed in a minicomputer for display as tempera-
ture. 
How It's Done: 
The pyrometer, shown in Figure 2, has a fiber optic 
probe with a row of 80 fibers focused on the blade in a 
radial direction. Each fiber has an image diameter of 0.05 
cm (0.02 in) at the blade. In operation, the rotating blade 
moves past a fixed point of focus, generating a raster of 
80 scan lines.
RADIATION RADIAT1EM 
ROTATING	 SINGUE-111111IN 	 REFERENCE CHOPPER - 
BLADE-
	
R(RBUNDLE- LAP	 \ .-A 
SHAFT-
	
MINI-	 HIGH SPEED A-D	 AMP. 
MOUNTED COMPUTER MEMORY 	 CONVERTER 
SENSOR 
Fig 2. - Turbine blade pyrometer. 
The flexible fiber bundle extends outside the engine to 
a box where radiation leaving each of the fibers in turn is. 
collected by a microscope and focused on a detector. The 
microscope views each fiber in sequence. by intermittent 
advance of the fiber row with an actuator. Thus the blade 
area is scanned line by line during a time of one to two 
minutes. A radiation chopper, synchronized and phased to 
the turbine rotation, intercepts the radiation during 
one-half of each revolution to provide a dark-input data 
sample. A shaft-mounted sensor generates a synchronizing 
pulse to precisely time the blade position and to select 
one blade for the start of measurement. Radiation from 
the internal reference lamp is transmitted by three fibers 
placed in-line with the row of 80 fibers at the fiber-
scanning actuator.
(continued overleaf) 
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Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that Such use 
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Each scan-line on the blade occupies a fraction of the 
turbine circumference. During this time, the detector 
output is digitally recorded in the high speed memory. 
Thus, during the greater part of each revolution, time is 
available for data handling.
I	 ' SILICON I	 I	 i	 H COMPARATOR	 MONITOR HOT-SPOT DETECTOR I
BUFFER MEMORY  
9-BIT	 I	 10-BIT 
AID	 I	 2STAGE	 DATA TO 
CONVERTER	 RECIRCULATING	 COMPUTER I	 SHIFT	 I 
REGISTER	 I 
TIMING &	 I	
I	 I CO DIA
	
_... VIJ CONTROL LOGIC	 NVERTER 
Fig 3. - Block diagram of signal 
conditioning electronics. 
Figure 3 is a block diagram of the signal conditioning 
electronics. The detector output is amplified and then fed 
to an analog-to-digital converter. The rapid production of 
digital data (two megahertz rate) is in excess of allowable 
computer input rates, thus requiring a data buffer 
memory. The memory can be loaded with data and then 
shifted into a computer at a slower rate. These tempera-
ture data can then be displayed on an oscilloscope for 
study.
Notes: 
1. The high speed digitizing rate results in resolution of 
better than 0.05 cm (0.02 in). Since blade tempera-
tures change quickly over short distances, the small 
spot diameter permits many temperature readings with 
greater fidelty and thus improves the measurement of 
true maximum temperature. 
2. An electrical trigger operated by the turbine shaft 
permits the selection of a test blade or blades for 
observation. 
3. Further information is available in the following 
report: 
NASA TM-X-68113 (N72-32459), Pyrometer for 
Measurement of Surface Temperature Distribution 
on 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: B74-10068 
4. Specific technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B74-10068 
Patent Status: 
Inquiries concerning rights for the commercial use of 
this invention should be addressed to: 
NASA Patent Counsel 
Mail Stop 500-113 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Source: D.R. Buchele and D.J. Lesco
Lewis Research Center
(LEW-12218)
is 
. 
S 
B74-10068	 Category 01


Rotating turbine blade pyrometer

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