The development of an advanced measuring system which measures the rapidly varying gas temperature at the exit of an aircraft jet engine combustor during ground based testing of hot section components was identified. Sensor guidelines, technical approach/program schedule, and the accomplishments are reviewed. The environment of a present generation combustor is shown. The method uses two beadless junctions type-B thermocouples to measure heat transfer coefficient in situ. Heat conduction effects are shown by a finite element model of the thermocouple

Elmore, D.

English

NASA Technical Reports Server

INTRODUCTION 
DYNAMIC GAS TEMPERATURE MEASUREMENT SYSTEM 
Dennis Elmore 
Pratt & Whitney Aircraft 
Government Products Division 
The objective of this effort is to develop an advanced measuring system which 
is capable of measuring the rapidly varying gas temperature at the exit of an 
aircraft jet engine combustor during ground based testing of hot section 
components. The following presentation gives a brief review of the oontract 
objectives/sensor guidelines, the technical approach/program schedule, and 
the accomplishments to date. 
The Sensor must be designed for installation in an annular jet engine combustor 
operating with jet A fuel and air, and must have a compensated frequency 
response up to 1 K Hz. The environment of present-generation combustors is 
detailed in Table I. The program goals for measurement uncertainty are 5% 
or less for frequencies up to 200 Hz and 10% or less from 200 Hz to 1000 Hz. 
The Program is organized into eight tasks" with the technical effort concentrated 
into the following six tasks: 
Task 1 - Study and Selection of Methods 
Task 2 - Analysis of Methods and Selection of the Most Promising Method 
Task 3 - Review 
Task 4 - System Design and Test Plan Formulation 
Task 5 - Fabrication and Tests 
Task 6 - Analysis of Results 
The contract was initiated on 10 August 1981 and will run for an 18 month 
period. Tasks 1 through 4 have been completed and Task 5 is currently in 
process. The results of these efforts are briefly discussed in the follqwing 
paragraphs. 
PROGRESS 
Task 1 consisted of identifying and evaluating candidate measurement concepts. 
The effort included performing a literature survey using the Lockheed Dialog, 
the NASA Recon and the Defense Technical Information Center information 
retrieval systems. A list of candidate measurement methods is shown in Table 
II. These candidates were evaluated against contract technical criteria and 
rated either acceptable or unacceptable. Results of the evaluation revealed 
that only two concepts meet all contract requirements: a) The dual-wire 
passive thermocouple and b) single-wire pulse" heated thermocoup~e. 
The dual-wire passive thermocouple concept uses two different diameter, 
beadless-junction thermocouples to measure heat transfer coefficient in-situ 
and thereby compensate thermocouple response. The single-wire pulse heated 
thermocouple concept uses an electrically-pulsed over-temperature condition 
to determine the time constant from the pulse decay rate. Construction 
techniques are very similar for both designs. Both approaches use type B 
wire elements with beadless welded junctions to provide a uniform cylinder 
in cross flow geometry which is easily analyzed. Both are mounted similarily 
in high temperature ceramic insulators. The length to diameter ratio for 
thermocouple elements of both designs is less than 20 to 1. 
75 
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The two concepts were further analyzed in Task 2. Each concept was analyzed 
for structural, thermal, and data acquisition/reduction requirements. Both 
concepts were rated acceptable structurally and thermally. The single pulse-
heated concept would have to be pulsed near the melting temperature of the 
tnermocouple material. In addition, the pulse-heating amplitude was not large 
enough to obtain the contract accuracy requirements using a reasonable number 
of decay pulses and sampling times. Based on these results, the dual passive 
thermocouple concept was selected for use in the remaining tasks involving 
detailed design, fabrication and testing. 
, 
The qnalyses also revealed that both concepts-had end conduction losses which 
could not be ignored and would have to be corrected during the data analyses. 
Task 4 efforts consisted of: 1) design of a temperature measuring system 
based on the dual-wire passive thermocouple approach, including sensor 
detailed design and design of the data acquiSition/reduction system; and 
2) the definition of the test plans. 
The sensor design effort was based on the thermal and structural analyses 
of Task 2. The final probe configuration was designed for installation in 
an F100 engine bores cope plug location at turbine inlet. The probe was 
designed structurally to P&WA design criteria and the final thermocouple 
wire element lengths were reduced from preliminary designs due to higher 
aerodynamic loading in the full scale engine. 
The final data acquisition/reduction system design was also based on results 
of Task 2. The computer software was modified from a simple first order 
system to a program using a finite element model which accounts for sensor 
wire end conduction losses. The data acquisition system records each thermo-
couple signal on FM tape through AC coupling and low noise differential 
amplifiers (Preston DX-A3). Data reduction system consists of an FM tape 
reproduce and a Hewlett Packard Model 5451 C Fouri.er Analyzer. 
The data reduction process consists of computing the theoretical response (gain and phase) of each thermocouple over a range of discrete frequency 
points (generally between 2 Hz to 40 Hz) as a function of heat transfer 
coefficient using the finite element analysis. The range of heat transfer 
coefficient is selected to cover the anticipated value for the engine test 
conditions. From these theoretical data, the transfer function (ratio of 
gains) of the. two thermocouples for the same discrete frequency points as a 
function of heat transfer coefficient is derived. 
Engine test data for both T/C's is digitized (4 Khz sampling rate) into 
the Fourier system and- converted to temperature using an NBS curve fit. 
From these data the transfer function of the two thermocouples is computed 
vs. frequency using FFT techniques. This measured transfer function data is 
used to determine the in-situ value of heat transfer coefficient from the 
theoretically derived relationships of the transfer function of the two 
thermocouples as a function of heat transfer coefficient. 
The in-situ value of heat transfer coefficient is then used to compute the 
theoretical response of the 76J.Lm T/C to the gas stream temperature fluct-
uations using the finite element analysis. Gain and phase response is 
computed at discrete frequencies from 2 Hz to 2Khz. This response curve is 
then used to compensate the 76J.Lm thermocouple engine data to yield a 
compensated frequency spectrum. The compensated frequency spectrum can be 
Fourier-transformed to yield the compensated temperature time wave form. 
76 
The test plans consist of three test series: 1) System shakedown laboratory 
tests; 2) Laboratory burner tests; and 3) An engine test. 
A summary of environmental conditions for each of these tests is shown in 
Table III. 
The system shakedown lab tests will verify system function. The testing will 
be done in a laboratory using an electrically heated air blower. The accuracy 
of the compensation will be verified using an electrical analog of the therm&-
couple finite element array using first order low pass RC filters which 
correspond to the individual time constants of each node. These filters will 
then be substituted for the thermocouple and a random noise signal will be 
input to simulate the thermocouple signal levels. 
The second test series will be conducted using a laboratory burner test rig. 
These tests will allow evaluation of the sensor and measurement system in an 
elevated temperature combustor environment. 
The third test series will be performed by installing and evaluating on a 
non-interference basis in an experimental F100 engine test. The sensor will 
be installed in the turbine-inlet borescope plug. These tests will provide 
the final evaluation of the sensor at the required environmental conditions. 
The program status as of the first of October 1982 was that Tasks 1 through 
4 has been completed and Task 5 was in process. The sensor fabrication and 
software program were completed. 
FUTURE WORK 
Future work will complete the three test series described above and process 
the data taken. The test program is a stepwise, iterative approach which 
allows for necessary problem-solving and technical flexibility. At the 
present rate, data acquisition should be complete by the end of 1982 and 
final data reduction/analysis should be well underway. 
SUMMARY 
An approach to dynamic temperature measurement has been identified. The 
method uses two beadless junction Type B thermocouples to measure heat 
transfer coefficient in-situ. Heat conduction effects are accounted for 
using a finite element model of the thermocouple. Fabrication of thermo-
couples is complete. A test program which verifies measurement system. 
function will be accomplished in the next few months. 
77 
...... 
00 
! a .. 
e UNITED TECHNOLOGIES PRATT&WHITNEY AIRCRAFT 
DYNAMIC GAS TEMPERATURE 
MEASUREMENT SYSTEM 
Host Annual Contractor Workshop 
NASA-LEWIS Research Center 
Prepared Under Contract NAS 3-23154 for 
NASA-LEWIS Research Center 
Presented by 
Denny Elmore 
Assistont Project Engineer 
19 October 1982 
GOVUHMENT "OOUCJS DIVISION 
..0 .... *1 
w .. ''''IIood\.''' UoI02 
DYNAMIC GAS TEMPERATURE 
MEASUREMENT SYSTEM 
Objectives 
GP 12-613 
To develop an advanced measuring system capable of 
measuring the rapidly varying gas temperature at the 
exit of an aircraft jet engine combustor during 
ground-based testing of hot section components 
AYIIOII4 _ .... 
DYNAMIC GAS TEMPERATURE 
MEASUREMENT SYSTEM 
Overview 
• Contract objectives and sensor guidelines 
• Technical approach/program schedule 
• Program status 
DYNAMIC GAS TEMPERATURE 
MEASUREMENT SYSTEM 
A~""'-.ze 
Table I sensor design and environment guidelines 
Geometry: Annular combustor, 2 c:m < H < • c:m 
Temperat ... : i - 14000 K 12080°F); T - soooK 1800°f) 
Frequency reapon .. : 1 kHz 
Pr ...... : 10 < P < 20 ATM 
FJow: v - 150 mil;" - 50 mil 
GIl compoIItlon: Fuel (nominal jet A, and air 
SenIOl' Ute: 5 hi' minimum 
Accuracy: Temperatur. un<:ertalnly S 5% lor • S 200 Hz 
Temperlt ... un<:ertalnly 10% .or 200 Hz < • < 1 kHz 
Spatial ra.olutlon: 0 S 0.5 c:m 
Vibration 109 
---
'-I 
1.0 
DYNAMIC GAS TEMPERATURE 
MEASUREMENT SYSTEM 
Technical approach/program shcedule 
Task - description 
t - Study and selection 
01 methods 
2 - Analysis 01 methods 
3-RevIew 
4 - System design and 
test plan 
5 - Fabrication and test 
6 - Analysis of result. 
-
DYNAMIC GAS TEMPERATURE 
. MEASUREMENT SYSTEM 
Table" concepts evaluated 
Sif'gle wire thermoc:oupIe 
• Passive 
• Pulse-heated 
Dual wire thermoc:oupIe 
• Passive 
• Pulse-heated 
Resistance thernIcImet. 
• Wire. 
• Film 
Uttrasonlc therrnorneler 
Ruldlc resonator 
Ga. sampling 
Johnson not .. thernIcImet. 
PIezoeIec:trlc ,_tor 
Vibrating wire 
Radiation pyrometry 
High Ipeed photography 
Coherent ant .... tok .. ,aman epectrOlCClpy 
1-------. 
Av..-~ ... 
A~""_ 
DYNAMIC GAS TEMPERATURE 
MEASUREMENT SYSTEM 
Task 1 - Study and selection of methods 
Literature survey 
• Concepts Identified 
Evaluation/screening 
• Selected - dual passive thermocouple 
- Single pulse-heated thermocouple 
DYNAMIC GAS TEMPERATURE 
MEASUREMENT SYSTEM 
Dual passive thermocouple concept 
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T1rno 
T1rno 
A..-r .... _ 
t 
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DYNAMIC GAS TEMPERATURE 
MEASUREMENT SYSTEM 
Single pulse-heated thermocouple concept 
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T_ 
T ... 
DYNAMIC GAS TEMPERATURE 
MEASUREMENT SYSTEM 
Task 2 analysis results 
"Structural 
Thermal 
Data ecqulaltlon 
and reduction 
Single-wire 
pulse-healed 
Acceptable: 
d>O.OO8CM(O.OO3In) 
UO<20 
Acceptable: 
end-conductlon 
correction necesaary 
(pulse approaches 
wire melting point) 
Unacceptable: 
pulse-heating amplitude 
required Is too large lor 
required accuracy and condltlOlll 
no. 
.. -".-TII,,!lr 
AV1tD311 IZ240I a' .. 
Dual-wire 
passive 
Acceptable: 
d>O.OO8CM(O.OO3ln) 
UO<20 
Acceptable: 
end-conductlon 
correction neceasary 
Acceptable: 
A~ ...... n .. 
DYNAMIC GAS TEMPERATURE 
MEASUREMENT SYSTEM 
Task 2 - Analysis of methods and selection of the· most 
promising method 
• Structural analysis 
• Thermal analysis 
• Data acquisition/reduction analysis 
DYNAMIC GAS TEMPERATURE 
MEASUREMENT SYSTEM 
Task 4 - System design and test plan formulation 
Sensor design 
• Mechanical 
• Structural 
• Thermal 
Data acquisition and data reduction system 
. Test plan 
AVIIGII1 ID4DI mae 
. ......... 
co 
...... 
DYNAMIC GAS TEMPERATURE 
MEASUREMENT SYSTEM 
Probe designed for F100 turbine installation 
Combustor 
f1ow-
DYNAMIC GAS TEMPERATURE 
MEASUREMENT SYSTEM 
Completed sensor 
",IiM.4ao;4£ 
Case 
A.,.... .... _ 
. hi '*ek'" '·,i81 
A'nIIDII 121'" _ 
DYNAMIC GAS TEMPERATURE 
MEASUREMENT SYSTEM 
Sensor tip geometry 
0.076mm 
0.508 mm (0.020 In.) 
dla Type B wlra 
0.254 mm (0.010 In.) 
dla Type B wire 
~:3BI:lr:la -n-tu , 1 'ur)) 1 
0.361 mm 
(0.015 In.) dl8 
Type B Wire 
0.476 em (0.188 ·In.) dI8 
eoorsAD·99 
ceramic stick with leM 
0.078 em (0.031111.) dl8 holes 
..--r-Cerama-dlp 
538 cement 
or Sennetel P.1 
---
DYNAMIC GAS TEMPERATURE 
MEASUREMENT SYSTEM 
Data acqulstlon system 
78,.m 
TIC -... . ... ---------1 
ACcoupIlng 
2~bm-... .)1 
Average 
temperature 
low noise 
dlflerenUeI 
ampliller 
low noise 
dlflerentlel 
ampliller 
g 
FMtape 
recorder 
O.-.ral purpoee 
dlflarentlal amplllIer 
AYJ111t7 __ _ 
();) 
I\,) 
DYNAMIC GAS TEMPERATURE 
MEASUREMENT SYSTEM 
Data playback system 
Oscilloscope 
. Fourier System 
graphics terminal 
Intarmedlate band 
reproduce amp 
Low pua muItI-poie 
elliptical 
anti-aliasing finer 
Fourier Analyzer System • 
computar, 64K, word memory, 
12 bit ADC,2.5 megaword 
moveable head disk 
DYNAMIC GAS TEMPERATURE 
MEASUREMENT SYSTEM 
Table 1/1 test plan summary 
System Ihakedown 
i i 
AVIIOMUHII .... 
Lab Full-Ide 
and compenaatlon burner engine 
Crtterla verilication rig I .... 
T emperalure (1900' K peak; j: 500' K flU(;tuatlona) X 
Frequency reepon18 (1000Hz c:ompenaated) X X X 
Preaaure (10 10 20 aim) X 
Flow (15Om/. with j: 5Om/. fluctuatlonl) X 
Gu compoaltlon (prodU(;I' of combultlon and air) X X 
SenIOr Hletlme (5 hr minimum) X X 
Accuracy X 
Vibration (lOg loading up to 500Hz) X 
Avne. .... _ 
DYNAMIC GAS TEMPERATURE 
MEASUREMENT SYSTEM 
Compensation method 
• Compute theoretical response (761'm and 2541'm TIC's) vs heat transfer 
coefficient (finite element conduction effects Included) over 
frequency range 
• Measure (data) response of 761'm and 2541'm TIC's over frequency 
range (using FFT techniques) 
• Determine actual heat transfer coefficient from computed and 
measured response 
• Generate theoretical response of 761'm TIC for actual heat transfer 
coefficient for frequency range 
• Compensate 761'm TIC data in frequency domain 
• Inverse fourier transform to time domain 
DYNAMIC GAS TEMPERATURE 
MEASUREMENT SYSTEM 
Program status 
Completed Tasks 1 through 4 
Task 5 In process 
• Hardware fabrication 
• Software programming 
• Testing 
A~"''''' 
A~1""_ 


Dynamic gas temperature measurement system

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