SIIlI FiE COPT

ARL-AERO-PROP-TM-.40 AR-04'-563

NIe DEPARTMENT OF DEFENCE

y m DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION

AERONAUTICAL RESEARCH LABORATORIESMELBOURNE, VICTORIA

I

Aero Propulsion Technical Memorandum 4

THE VARIATION IN AIWRLOW COEFFICENT FOR

ALLISON TS& coNUSTOR LINERS (U)

by

F.W. Skidmoreand

W.H. Schofield D I~DTICELECTEi

DEC 0 71M

Appove D..*J pobli -Approved for Public Release

This work Is copyright. Apart from any fdr dealing for the purposeof study, research, criticism or review, as permitted under theCopyright Act, no part may be reproduced by any process withoutwritten permission. Copyright Is the responsibility of the DirectorPublishing and Marketing, AGPS. Inquiries should be directed to theManager, AGPS Press, Australian Government Publishing Service,GPO Box 8, Canberr, ACT 2,01.

(C) COMMONWE LTH OF AUSTRALIA I7OCTOBER 8107

8 8 12 6 087,

AR-004-563

DEPARTMENT OF DEFENCEDEFENCE SCIENCE AND TECHNOLOGY ORGANISATION

AERONAUTICAL RESEARCH LABORATORIES

Aero Propulsion Technical Memorandum 444

THE VARIATION IN AIRFLOW COEFFICIENT FOR

ALLUON T5B COMBW1.R LINES

by

F.W. SKIDMOREand

W.H. SCHOFIELD

SUMMARY

It is shown that it is possible to have a circumferential turbine inlettemperature variation in excess of 900 C in a correctly assembled T56 SeriesLI engine. A significant part of this variation is due to differences in airflowinto the liner caused by the variations in airflow area associated withmanufacturing tolerances. A simple technique is described that will enablematched sets of liners to be selected to build engines and thus avoid excessivetemperature maldistributions. Preliminary experimental results aredescribed.

(C) COMMONWEALTH OF AUISYAIJA 1987

POSTAL ADDRESS: Director, Aeronautical Research Laboratories,P.O. Box 4331, Melbourne, Victoria, 3001, Australia

Page No

1. INTIRODUCTION 1

2. THE ALISON T56 TURBOPROP ENGINE 1

3. THE EFFECT OF LINER MANUFACTURING TOLERANCES 6

4. COMBUTOR LINER CALIBRATION 7

4.1 Test Equipment 7

4.2 Operation 8

4.3 Theoretical Considerations 10

5. RESULTS 13

*6. DISCUSSION 14

* 8.1 Airflow Calibration 14

6.2 Further Work 14

7. CONCLUSIONS 14

ACKNOWLEDGEMENT 14

REFERENCE

DISTRIBUTION

DOCUMENT CONTROL DATA

gil0 Accessioni For

IITIS GFA&IDTIC TAB 0lUnnnounood 1Justification

By iuinDis-triuO

AvailabilitY CodesAvail and/or

Dtt p.cial

AA1

[11

1. INTRUDUCTION

Allison T56 engines operated by the RAAF are used to power the Hercules andOrion aircraft. These engines currently suffer hot section failures, particularly,turbine nozzle guide vanes and first stage turbine blades. In an effort to gain abetter understanding of the likely cause of the problem, the RAAF has decided to runa T56 engine on a mobile engine test stand in various builds and measure each of the18 individual turbine inlet temperatures separately. Three engine builds will beinvestigated; an unmodified condition; fitted with a matched set of fuel atomisersand rebuilt using the matched set of atomisers and a matched set of combustorliners.

This memorandum describes some initial work for this program. A techniqueand the equipment necessary to calibrate the airflow of a combustor liner isdescribed and some preliminary results carried out on liners drawn from various T56engines is reported.

2. THE ALLISON 156 TURBOPROP EN(INE

The Allison T56 turboprop engine has a 14 stage axial flow compressor with apressure ratio of 9.5:1, six canannular type combustors and a 4 stage axial turbine.The engine is designed to operate at a constant speed of 13820 RPM and drive apropeller through a reduction gearbox. The RAAF operate 3 models of the AllisonT56 engine, details of which are listed in Table 1.

TABLE 1

ALLISON T56 ENGINE OPERATED BY THE RAAF

ENGINE MODEL AIRCRAFT

SERIES II T56-A-7 C130ESERIES I T56-A-14 P3 ORIONSERIES UI T56-A-15 C130H

From a combustion system viewpoint the two Series III engines are identical.However, there are significant differences between the Series U1 and Ill engines,particularly in the airflow distribution through the combustors. A Series IIcombustor liner is shown in Figure Is and a Series III combustor liner in Figure lb.

17t

(2)

FIG. l(a) ALLISON T56 SERIES II COMBUSTOR LINER

.i~ ...4... ....

FIG. 1(b) ALLISON T56 SERIES III COMBUSTOR LINER

131

In an engine six of these liners are installed within an annular pressure casingand linked together with interconnector tubes. Two of the combustors, located atthe top and bottom of the engine, have high energy igniters.

As seen in Figure la and lb there are several important differences in the designof the Series II and Series El liners; in particular the location of air holes in the linermidsection and the variations in the outlet sections that are necessary toaccommodate the particular turbine configuration.

Figures 2a and 2b indicate the distribution of air entering into the Series 11 andII engine liners respectively. These flows were estimated from measured areas usingthe coefficients of discharge for combustion systems described in Knight and Walter(1953) and Adkins and Gueroui (1986).

14.91. 9 .4. 9A 9.41. 9.41I.

5.4.

5.6.4. 0.5"1. 6A%/ .9I.

Priimery SwxI~r DJ.1utian14.3% 32.8 53.0t

I Can Ref. Drg. 6847712 (T56-A-7)

FIG. 2(a) AIRFLOW DISTRIBUTION OF T56 SERIES II COMBUSTOR LINER

I

!L ..1

141

1I,.2. 1O-O. 10.01. &91 8.9*1. 12.6% 8.1. 1.11.

31.4 .0.5'1 2.81. 2.21. 6.01. 2.21.

15.3% 33.0% 51.5%

can Ref. Drg. 6876880 (T56-A-14/15)

FIG. 2(b) AIRFLOW DISTRIBUTION OF T56 SEREES III COMBUSTOR LINER

Following the usual practice of dividing the liner into primary, secondary anddilution zones it was assumed that the primary zone included one third of the air thatenters the first cooling corrugation around the dome plus half of the air that entersthe first set of holes. The remaining part of these flows then forms part of theairflow for the secondary zone where combustion should be completed. Similarly thesecondary zone includes half of the air entering the holes in the third segment of theliner and one third of the air entering the third cooling corrugation with theremaining part of these flows becoming dilution air. This method was used byDetroit Diesel Allisons (1985) to assign and divide airflows between different zonesin a similar liner.

Fuel is injected into the dome of the liner via a duplex or twin orifice typeatomiser shown in Figure 3.

151

6.

FIG. 3 ALLISON T56 ATOMISER-ASSEMBLED AND UNASSEMBLED

The secondary stage of the atomiser has a pressure operated variable orifice in

the fuel passage to enable fuel to be shut off and also to provide an approximatelinear flow versus pressure characteristic. A typical flow calibration curve is shown

in Figure 4.

161

3000

40.

4) 000$40.44.4

0) 10100$D4CDIS 0

Fulfo)K.h

FI.4ALSNT5 TMSRFOWCAAT4n

3.TH FIG. 4F ALISN 6OER FLOWATUJN CHRACTERSI

Analysis of Allisons Drawing No 6876080 for manufacturing Series Incombustor liners shows that there is a maximum possible variation in flow area from(approximately) 4820 mm 2 to 5140 mm 2 at the extremes of the manufacturingtolerances.

- -- - - -- - --- -

171

For a combustor liner with exactly the nominal airflow areas at sea lvel takeoff and a turbine inlet temperature of 1077°C, the fuel/air ritio is 0.0212 . For acombustor liner on the lower airflow area limit of 4820 mm , the fuel/air ratio isincreased to 0.0219 which implies a turbine inlet temperature of 10970 C.Alternatively for the combustor liner on the higher limit of flow area the fuel airratio is decreased to 0.0205 which implies a turbine inlet temperature of 1055C.

This analysis assumes that each atomiser admits the same amount of fuel toeach liner which in practice does not occur. Allisoas allow for variations under sealevel take off conditions in atomiser calibrations of + 11 kg/hr in fuel flow. If thisvariation is applied to a matched set of liners, each with the same a w area thenthe implied turbine inlet temperature will vary from 10510C to 11010C . If, to takethe worst cases, a liner with minimum flow area was fitted with an atomiser with thehighest fuel flow and a maximum air flow liner Is fitted with a minumum fuel flowatomiser then the outlet temperatures from these liners would vary from 11230C to10320C. From this analysis it was decided to develop a procedure to calibrate theair flow of T56 liners so that each engine could be assembled with a matched set ofliners to minimise the circumferential temperature variation.

4. COMMUSB r lINER CA RATIN

4.1 Test Equipment

A schematic layout of the test equipment used to calibrate the T56 combustorsfor airflow coefficient is shown in Figure 5 and photographed in Figure 6. Theequipment consists of a wooden box which has a cut out shaped to accept a liner. Alljoints are sealed to prevent air leaking into the system except through the liner. Thebox is connected to a centrifugal blower via a section of 100 mm tubingincorporating a venturi meter. Pressure drop across the venturi is measured using anaircraft airspeed indicator. This is used to set the airflow being drawn through theliner to the same value for each test. Airflow is controlled by a butterfly valve onthe outlet of the blower. The pressure drop across the liner is measured using aninclined water manometer. The pressure insida the combustor is tapped using arubber stopper, that has been drilled through to accept an 8 mm tube, inserted intothe atomiser boss in the dome of the liner. Both the Interconnector tubes in thecombustor liner and the Igniter bown are sealed with rubber stoppers.

1 Temperatures and fuel air ratios were determined from NGTE produced charts of

combustor temperature rise at constant pressure versus fuel/air ratio.

2 Rheaume (1987) discusses the practical problems of the T56 atomisers in detail.

____ I

181

4.2 Operation

The liner to be tested is inserted into the box and sealed at a point just belowthe last dilution hole as shown in Figure 5. The blower is then started and thebutterfly valve adjusted to give a predetermined reading on the airspeed indicator.After the airflow has stabilized, the pressure drop across the liner is measured on theinclined manometer.

Care is required to ensure that no extraneous leaks are present and that thesame setting is used on the airspeed indicator at each change.

Inclined J

Manometer

Interconnectors and ignitor boss sealed withrubber stopperA ict

vlSealCombustor liner under test

Vnuiair meter N I

o~i'Li

~Sealedaircase

Blower

j Airspeed indicatorS Butterfly control

~valve

FIG. 5 SCHEMA77C LAYOUT OF UJNEP. CALIBRATING EQUIPMENT

191

Liner under test Inclined water manometer

Venturi Centrifugal blower

FIG. 6. LINER CALIBRATION RIG

[101

4.3 Theoretical Considerations

The mass flow through a combustor liner in the equipment shown in Figure 5 willbe given by

Nd~p wr I pAV

n=1 n

where rhr is the total mass flow

p is the air density

An is the effective flow area of each of the holes 1 to N and

Vn is the velocity through each of the holes 1 to N.

For convenience we write

r = p ArVT (1)

where AT is a total effective flow area through the liner as a whole and VT is theequivalent velocity through that effective flow area.

The pressure drop across the liner caused by the airflow induced through theliner can be written

1 2pL - Cl 1 PVT

where again C1 is an effective or overall drag coefficient of the liner holes.

Replacing A PL with h, the pressure measured with the inclined manometer we have

h - C2 P VT2 (2)

In comparing a set of liners from an engine, we are primarily interested in thepercentage variation in airflow around the engine.

Equation (2) can be written

v - h

which when substituted into (1) gives

P Ar ~h 7-(3)P2

or Ar - p h

if the mass flow is held constant

• l -- ---- R ~ mmnmunum mmmml n nll- naIim llnIli

or h (4)

av

which gives the required variation from the average.

5. RESULMS

ARL had six combustor liners from an Allison T56-A-11 engine. These linerswere similar to the liners from a T56-A-7 engine used in the C130E aircraft and werein good condition. They were tested using the equipment and procedure described inSection 4.1 and 4.2. The results are presented in Table II.

ARL also had 2 Series I liners out of the T56-A-14/15 engines. These linerswere unserviceable due to cracks and buckling but were also tested. The results forthese liners are presented in Table HI.

!I

__ _

(12 1

Liner h avx 100 Fuel/Air T.L.T.

Serial NO. Scae BeadingFA Ratio3 OC

3655 15.9 99.7 0.02i26 1078

1669 15.4 101.3 0.02093 1068

3554 15.7 100.3 0.02114 1074

6573 16.7 97.3 0.02179 1094

3882 15.6 100.6 0.02107 1072

1671 15.5 101.0 0.02099 1069

AVERAGE 15.8 100 0.02120 1076

TAMLE JUL BERM H1 UER CALIBRA'IIN AND PREDICIONOF TURBINE RUMK TEIMMEATURE FOR EACH

Liner h100 Fuel/Air TJLT.

SerI NO. Scal Reading Ratio OC

AA5904 16.2 100.6 0.02107 1072

KH2148E 16.8 99.4 0.02126 1078

TABLE, M. SEuRS M LINER REULIS

3.Actual airflow into each liner is reduced or increased from the average by

the percentage x 100. Liner fuel/air ratio is therefore calculated from

the overall engine fulair ratio of 0.02120 x Tubn inletemperature was determined from NOTE charts of Combustor Temperature rise

at constant pressure versus fuel/air ratio.

[131

6. D XI*ON

6.1 Airflow Calibration

'.e airflow tests carried out on the liners from the T56-A-11 engineshow that there can be a considerable variation in mass flow induced througha combustor liner (Table UD and if this variation was applied to the Series Imaximum operating turbine inlet temperature of 1O77°C with a perfectlymatched set of atomisers, then the circumferential variation oftemperatures around the six liners would range from 10680 C to 10940 C. Itmust be stressed, however, that the sample of liners tested was small, andthat it is likely that a larger sample would show a greater variation. Inaddition, variations in atomiser flow rates would increase thecircumferential temperature variation.

The results for the Series it liners show that temperature variations canbe expected in this case also. However, with a sample of two liners noconclusions can be drawn.

6.2 Further Work

In order to establish the full extent of airflow variation for T56 liners alarge number of liners will need to be tested. With the variation established,liners should be grouped into 4 or 5 ranges of mass flow to enable engines tobe built with a more uniform fuel/air ratio between combustion chambers. Ifthis is carried out with selective fitment of atomisers, as discussed byRheaume (1987), then a minimal circumferential temperaturemaldistribution in Allison TM engines will be realised. This procedure shouldcontribute to the extension of life of hot end components such as the turbinenozzle guide vanes and first stage turbine blades.

7. CONCAlu

A simple technique has been developed to enable matched sets of T56combustor liners to be fitted to engines. Preliminary calculations and testsshow that a circumferential temperature variation of at least 900 C ispossible. It is anticipated that a greater variation than this will exist in thepresent RAAF inventory of TM engines. Circumferential temperaturevariations in engines will be minimised if the technique described in thismemorandum is adopted and is combined with selective fitment ofatomisers.

ACKNOWMKMOR

The authors wish to acknowledge the assistance given by Mr N.J.Repacholi in building up the equipment used to calibrate the liners andassisting with the tests.

p

[141

REFERENCE

1. Knight, H.A. and R.B. Walker, 1953: The Component Pressure Losses inCombustion Chambers. NGTE R.143.

2. Adkins, R.C. and D. Gueroui, 1986: An Improved Method for AccuratePrediction of Man Flows Through Combustor Liner Holes. Journal ofEngineering for Gas Turbines and Power Vol 108, pp 491-497.

3. Detroit Diesel Allims, 1985: T56/501D Series I Low SmokeCombustor. Proposed EPN No 5633.4.12.

4. Rheaume, J.F., 1987: To be published as an ARL Aero Prop TechMemorandum.

'*

..... .I

Department of Defence

Defence CentralChief Defence ScientistAssistant Chief Defence Scientist, Operations (shared copy)Assistant Chief Defence Scientist, Policy (shared copy)Director, Departmental PublicationsCounsellor, Defence Science (London) (Doc Data Sheet Only)Counsellor, Defence Science (Washington) (Doc Data Sheet Only)S.A. to Thailand MRD (Dc Data Sheet Only)S.A. to the DRC (Kuala Lumper) Doc Data Sheet Only)OIC TRS, Defence Central LibraryDocument Exchange Centre, DISB (18 copies)Joint Intelligence OrganisationLibrarian H Block, Victoria Barracks, MelbourneDirector General - Army Development (NSO) (4 copies)

Aeronautical Research LaboratoryDirectorLibraryChief Aerodynamics and Aero Propulsion DivisionHead - Aero PropulsionBranch File - Aero PropulsionAuthors: F.W. Skidmore

W°H. SchofieldD.A. FrithL.W. HillenS. HenbestG.F. PearceJ.L. FowlerN.J. Repacholi

Materials Research LaboratoryDirector/LibraryDr G. Johnston

Defence Science and Technology Organisation - SalisburyLibrary

WSRLMaritime Systems Division (Sydney)

Navy OfficeNavy Scientific Adviser (Doc Data sheet only)Aircraft Maintenance and Flight Trials UnitRAN Tactical School, LibraryDirector of Naval Aircraft Engineering

lI

... .... _ _ __ __ __

r

Army OfficeScientific Adviser - Army (Doc Data sheet only)Engineering Development Establishment, LibraryUS Army Research, Development and Standardisation Group

Air Force OfficeAir Force Scientific AdviserAircraft Research and Development Unit

Scientific Flight GroupLibrary

Engineering Division LibraryDirector General Aircraft Engineering - Air ForceDirector General Operational Requirements - Air ForceHQ Operational Command

SMAINTSOMOPSTOPS

HQ Support CommandSLENGOAIRENG2AIRENG2B

HQ RAAF RichmondHQCO. No. 36 SquadronCO. No. 37 SquadronCO. No. 486 Squadron

RAAF Resident Engineer Qantas

Department of Administrative ServicesBureau of Meteorology, Library

Department of Transport and CommunicationLibraryFlight Standards Division

Statutory and State Authorities and IndustryAero-Space Technologies Australia

ManagerLibrary

Australian Nuclear Science and Technology OrganisationAustralian Airlines, LibraryQantas Airways LimitedGas & Fuel Corporation of Vic., Manager Scientific ServicesSEC of Vic., Herman Research Laboratory, LibraryAmpol Petroleum (Vic) Pty Ltd., Lubricant Sales & Service MgrAnsett Airlines of Australia, LibraryAustralian Coal Industry Research Labs Ltd, DirectorBHP, Melbourne Research LaboratoriesBP Australia Ltd, LibraryHawker de Havilland Aust Pty Ltd, Victoria, LibraryHawker de Havilland Aust Pty Ltd, Bankstown, LibraryInstitute of Fuel, Australian Branch, SecretaryMajor Furnace and Combustion Engineers Pty Ltd, Manager

Australian Institute of Petroleum Ltd

Rolls Royce Of Austaml Pty Ltd, Mr C.G.A. Dailey

Uiesities and Colleges

AdelaideBarr Smith Libraryprofessor of Mechanical Engineering

FlindersLibrary

La TrobeLibrary

MelbourneEngineering Library

MonashHargrave Libraryprof I.. Polmear, Materials Engineering

NewcastleLibrary

New EnglandLibrary

SydneyEngineering LibraryHead, School of Civil Engineering

NSWphysical Sciences LibraryProfessor R.A.A. Bryant, mechanical EngineeringProfessor G.D. Sergeant, Fuel TechnologyLibrary, Australian Defence Force Academy

QueenslandLibrary

SwinburneLibraryDr J. Perry

TasmaniaEngineering Library

Western AustraliaLibraryAssociate Professor J.A. Cole, Mechanical Engineering

RM1T

Library

CANADA

Laval University QuebecD. KretchmerJ.F. Rheaume

SPARES (10 copies)

TOTAL (120 copies)

hiL 20 DW I or DIVCZM P=CLSICOM

DOCUMENT CONTROL DATA ~ iIa. M M ~ i 2. Dac 3. UM WNM

AR-004-563 AR-AERO-PROP- 15 OCTOBER 1987 AIR 89/567IX L III lmCIMI~m .NO A

THE VARIATION IN AIRFLOW (NAM ArinWM UMIw nr 15ff FIIENT F2R ALLISON T56i BM(a).i. () .C

El El FF.W. SKIDM4ORE Not Applicable.

W.H. SCHOFIELD

AERONAUTICAL RESEARCH LABORATORY BrwP.O. BOX 4331, MELBOURNE VIC 3001 m _________

j ~12. um ommx 8nMMW (VMW aMET Approved for Public Release.

uwm SUCI az M ni. OF vinu. CuMinz WMr. MOMu. AM 24011ka. wno W z 1W =N =us= = m mminsa m m Toai ....No Limitations

M~. awm m ppn(U. CRALPinw ) I! E33rtO SPO 3k

14. 901min,0 15. MW

obustion chamber liners) 0081DTemperature distribution.Allison T56 engine 'Q~. d)

is. aiNInM It is shown that it is possible to have ~Aircumferentialturbine Inlet temperature variation in excess of 904C/In a correctlyassembled T56 Series III engine. A significant part of thisvariation is due to differences in airflow into the liner caused bythe variations In airflow area associated with manufacturingtolerances. A simple technique is described that will enable matchedsets of liners to be selected to build engines and thus avoidexcessive temperature maldistributions. Preliminary experimentalresults are described. C~-~ I,~O- at - --

UNLSSFED

TNI8 PAiN IS 20 22 USED TO RCO X0afZWf WHICH IS 93Q013M M? 2WU ?UINU IOUITS OWN 9 UST WHICH WILL NUN OR AMD TO INU DINTIS DATA CUMU SnPCI]PICILT RZOURSTED.

17. nffqU

AERONAUTICAL RESEARCH LABORATORY, MELBOURNE

18. DOCOUt 3==MR NOMO 19. conCw 20. TIh Cr ME AM

AERO PROPULSION 1 43 1230 OE

TECHNCIAL MEMORANDUM 444

22. DMeNumMra Mr. *(a)

C2/203 C2/147

23. mnscm I mnm(mn1nw