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Basie Instrumentation of a Low Speed Axial Compressor
Sami Blidi, Hubert Miton
To cite this version:
Sami Blidi, Hubert Miton. Basie Instrumentation of a Low Speed Axial Compressor. Journal de Physique III, EDP Sciences, 1995, 5 (7), pp.919-924. �10.1051/jp3:1995168�. �jpa-00249362�
Classification Physics Abstracts
47.80v 47.32Ff 47.40Hg
Short Communication
Basic Instrumentation of a Low Speed Axial Compressor
Sarni Blidi and Hubert Miton
L-E-M-F-I- URA CNRS 1504, Universit4 P. & M. Curie (Paris VI) Bit. sll, Campus Univer- sitaire, 91405 Orsay Cedex, France
(Received 4 February 1994, revised 31 May 1995, accepted I June 1995)
Abstract, The flow modelling depending on test results allows
a best aerodynamic com- prehension. For this reason, a test bed of L.E.M.F.I.'s axial compressor has been set and
instrumented for
a detailed exploration of the flow in a four-st.age tiJrbomachine cba,racterised by a little spacing between blade rows. In this paper, first are given brief descriptions of the
geometrical characteristics of this compressor, the test bed's control system operation and the instrumentation set. Next, measures for the exploration of flow are discussed. Finally, typical
results concerning the global and local performance measurements and their analysis are pre-
sented. This work permitted to instrument the L-E-M-F-I-'s four-stage axial compressor test bed and obtain the flow steady and unsteady characteristics using the five-hole and hot film probes.
R6sum6. Les 4tudes de mod41isation de l'4coulement dans les compresseurs axiaux doivent
s'appuyer sur des r4sultats exp4rimentaux permettant une meilleure compr4hension des ph4nombnes a4rodynamiques et convenant h la validation des codes num4riques. I cette fin,
un banc d'essais de compresseur axial basse vitesse a 4t4 mis au point et instrument4 au L-E-M-F-I- Iii pour des
explorations d4tail14es de l'4coulement darts une machine comportant 4 4tages, caract4ris4e par le faible espacement entre les rang4es d'aubages. Dans cet article, nous d4crivons bribvement les caract4ristiques g40m4triques du compresseur axial, les systbmes de contr61e du fonction-
nement du banc d'essais et l'instrumentation mise au point. Nous parlons ensuite des moyens
d'explorations de l'4coulement utilis4s. Nous fournissons enfin des exemples de r4sultats de
mesure des performances globales et locales du compresseur et analysons bribvement ces rd-
sultats. Le travail eIfectu4 a perrnis de mettre au point et d'instrumenter un banc d'essais de compresseur axial basse vitesse au L-E-M-F-I- et rendu possible la d4terrnination des grandeurs
stationnaires et instationnaires de l'4coulement entre les rang4es d'aubages en utilisant des son- des clinom4triques de pression et des sondes £ films chauds.
1. The Axial Compressor CMEI
CMEI is a four stage axial flow compressor. The main characteristic of this machine is the
narrow spacing of the adjacent blades rows (10 mm). Such a distance is just sufficient to allow
the introduction of probes between these rows, The axial lenght of the four stages is equal to
© Les Editions de Physique 1995
920 JOURNAL DE PHYSIQUE III N°7
Fig. I. Axial compressor CMEI.
624 mm. the diameter of the casing is equal to 550 mm. On the hub, the diameter varies from 371 mm in the inlet plane to 410 mm in the outlet one (Fig, I). The following tables give the
main characteristics of the blades in the fir>t stage.
Radius Chord Thickness Stagger angle Camber angle
mm mm ° °
Hub 82 7.4 44.77 51.65
Middle 82 6.4 55.17 37.12
Ti 82 4.8 64.02 25.61
Rotorl
Radius Chord Thickness Stagger angle Camber angle
mm mm ° °
Hub 88 5.2 19.67 75.30
Middle 88 5.2 16.72 71.55
Ti 88 5.2 15.07 67.75
Stator
For the stages 2 to 4 the geometry of the blades is similar excepted the stagger angle. The values of the stagger at the hub is given below for these stages.
Rotor 17 1.027
Stator 24 0.682
Rotor 2 19 0.936
Stator 2 27 0,618
Rotor 3 19 0,950
Stator 3 27 0.626
4 Rotor 4 19 0.962
Stator 4 27 0.634
2. Test Bed AX200
The main components of the experimental set-up are represented in Figure 2, It is a test bed aspirating and discharging in the athmosphere. The power available is, at the present time, limited to 200 Kw and the maximum speed of rotation is 4500 rpm.
In view to reduce the duration of the tests programs, the systems of measurements have been fully automatized. The rotational speed of the compressor is regulated by the frequency of the current of the AC motor, This speed is controled using a optical detector fitted in the
casing in the plane of the first rotor, It gives a TTL type pulse for each passage of a moving blade. This apparatus also serves to the synchronisation of unstationnary measurements. The
Diaphragm Outlet
Flow Convergent
adjuster
Inlet
Filter *-
Fig. 2. Test bed AX200. Settling Chamber
n~~r~~ ~ ~~~~ ~
fi
RS 232 ~ ASCII ~ 'FA 100 anemometer
fi
interface (6channels) probe
~ fi
~ ~
measurement probe
(8cha~~ls)
~ ZOC is
~
multi-pressure ~ Pressure~ ~
~ff
~ ~
~~~~f~s
~"'~ ~
~ ~~
Flow rate Static and total
regulation
~
pressure plugs /
~
,/ Rotating speed
÷÷L card < rec°trier
~~~ ~~~~~~
> Probe azimuth
displacement
~
Fig. 3. Global configuration of the system.
mass flow rate of the compressor is controled using a diaphgram fitted in the exhaust duct and regulated by the axial displacement of the conical hub wall just downstream the outlet plane of the compressor. This wall is automatically driven by a DC motor. Inlet and outlet temperatures are obtained from platiniurn resistances gauges introduced radially in the inlet and the outlet planes of the compressor. The pressures are measured with Kiel rakes, radially
and circonferentially located. They are used to know the global pressure ratio of the compressor
an equally to detect the presence of stationnary distorsions in the inlet plane. Alls the operating
proccess (control of mass flora rate, speed of rotation) probes displacements, data acquisitions
are driven by a PC type computer. The global configuration of this system is shown in Figure 3.
922 JOURNAL DE PHYSIQUE III N°7
3. Global Performance of the Compressor
The basic components of the performance of the compressor are:
the mass flow rate the rotational speed
the total pressure ratio
The results of the global performance of the CMEI axial compressor are represented in
Figure 4.
Measurements has been performed using the instrumentation mentionned above:
Keel probes rakes and temperature resistors probes for pressures and temperatures, di- aphragm for mass flow rate. With such instruments, the relative incertitude as calculated in
reference iii are closed to:
1.1% for mass flow rate o.1% for pressure ratio
np 30
25
Surge ~
20
line
~
/ 5
/
lo
~
rPm
.05 ~~~~ ~~°~
3000 rpm
00
4 5 6 7 7
Qm(k9/S)
Fig. 4. Compressor global performance.
4. Instrumentation for Velocity and Pressure Measurements in the Stages of the
Compressor
4.I. FIVE HOLE PRESSURE PROBES "COBRA" (FIG. 5). These five hoie-probes give the three components of the velocity, static an total pressures at the location of measurement.
Each hole is connected to a pressure transducer (pressure scanner SCANIVALVE ZOC 16:
range ~5 psi). However these datas are values averaged/time, through a characteristic mode
depending on the geometry and on the installation of the probe. Then, data collected by such probes, in a strongly unsteady flow, close to the rotating blades, are to be considered with a great care.
Yaw plane ())
Pitch planela)
20
14
6
Fig. 5. Five-hole pressure probe.
9QO
'~ ' /
' ,, 38, 501
~~j ~7§~ -~._,
~
10 i,0yP<cdl Spacinc041
Fig. 6. Hot films probe.
4.2. HOT FILMS PROBEB (FIG. 6). These probes includes two quartz wires, each of them
supporting a platinium film (TSI 1240). They can be used in airflows with velocities up to 350 mIs and temperatures limited to 150 °C. The cut-off frequency is 250 kHz. They give the
unsteady components of the velocity in the plane parallel to the two wires. The problem of the third component of the velocity is quite complex. Indeed, it requires a third wire. It is very difficult to integrate such a third wire in a small sized probe, due to the interactions between the wakes generated by the pins supporting the wire and the other wires.
These hot films probes are linked to a constant temperature anemometer (TSI IFA 100), including 6 channels. It talks with the computer through RS232 protocol.
4.3. USE OF THE COBRA AND HOT FILMS PROBES FOR INVESTIGATIONS OF THE FLOW
BETWEEN THE BLADE Rows. Cobra probes and and hot films probes are calibrated in
a convenient wind tunnel specially setted up in LEMFI; calibration procedures are described in details in reference ill and reference [2]. These probes are used only in the planes defined
924 JOURNAL DE PHYSIQUE III N°7
~~
~
p
caner <
Hw
"..
Statorj
~
l'..,, ~'
-~
~
hub
/
Fig. 7. Five-hole probe replaced in a blade to blade Field.
by a constant axial position between the rows of blades. Indeed, due to the size of the probes
relatively to that of the blades channels, it would be out of sense to use these probes in view of velocity and pressure measurements in the stators blades channels for exemple.
The probes are introduced radially between the rows and moved both in tangentiel and radial directions (Fig. 7). The spatial grid of measurement is identical for the two types of probes, including 150 points (10 along radius and 15 in the direction of rotation).
The "Cobra" probes allow steady measurements only; average /time values are obtained from sets of 50 pressure datas collected at a frequency of10 Hz.
For the hot wires probes, sets of 4096 voltages from each wire, are collected at a frequency
of10 kHz. Then, the measurement duration represents about 30 revolutions of the rotor.
Conclusions
The present paper reports the set-up of a test bed of axial compressor and the development of its basic instrumentation including sytems of exploration of the flow like "Cobra" probes and hot films probes to be used between the rotating and static rows of blades. These systems of
instrumentation are suitable for measurements restricted to regions between the rows of blades.
At this time, other techniques are in development in view of detailed investigations of the flow
along the walls of the stator blades: unsteady static pressures with miniature transducers and heat flux with hot films, for a better knowledge of the unsteady boundary layer behaviour, from the leading to the trailing edge of the blades.
References
[Ii Blidi S., Mise au point et instrumentation d'un compresseur axial 4 4tages basse vitesse, Thbse U-P-M-C-, Paris 6 (Janvier 1993).
[2] Treaster A-L- and Yocum A-M-, The calibration and application of five-hole probes, ISA Trans.
18 (1979) 23-24.
[3] Miton H., Blidi S. and Ayaz Y., Mesure des 4coulements en environnement machine dans un
compresseur axial multi-4tages basse vitesse, Rapport de synthbse finale, D-R-E-T- N°89-217 (1990).
