CONVERSION OF SINGLE-SHAFT TURBOPROPA ENGINE TO TWO-SHAFT INDUSTRIAL TURBil\"E A
by
Gas Turbine.J. D.Marketing_ Horth Manager
Ingersoll-Rand Co. Phillipsburg, N.J.
compared to th e more common practice of relating re fohn Harth r_;raduated from Car duced te mperatures measured further along in the ex negie Tech with a B.S. in pansion cycle. There are thirty-two thermocouple J/echanical Engineering.in 1943 Fallow in g elements arranged in groups of two 132) the output of service in the Corp of Enr_;ineers in which is avera!!ed to the engine (2),tu rbine inlet � � tem- II, he has spent more than twen perature ITIT)� !rive ty-fiveWW years in the design, ap
plication( 25) and m arketing of Turbo The four turbine stages of the aircraft engine machinery. During this time, he was are a single assem( ..J.)bly, the power from which is transmit instrumental in the introduction of led forward. That not used for compressor section
the T-56 aircraft engine to i dustrial is available for mechanical work atthe the front end through
service, and its later conv ersnion to a the torque tube system. The assemblY of the turbine two-shaft model-the subject of this paper is cur· section is held together by through-bolts but torque is
ently Turbine Marketing Manager for. HeIngersoll transmitted through curvic coupling interfaces. Randr Company.Gas This engine was one of the first to employ internally cooled blades. Both the first stage nozzle and the first The GT-40 two-shaft industrial turbine is a direct rotating stage have this feature. The construction of off-spring of the T-56 Turbo Prop single shaft engine. these elements are shown in Figs. 2 and 3. This widely used aircraft power plant is illustrated in Fig. l. In the aircraft engine, roller bearings a;e provided As an aircraft power system, the T-56 consists of to support the turbine elemen t on each end. the turbine itself, a torque meter, gearbox and impeller. At the inlet end of the compressor section, four ( 4) This assembly has a takeoff rating at 60°F and sea level, pads are provided for shaft driven auxiliaries. These are of 5150 mechanical horsepower plus 800 pounds of jet gear driven from the shaft through the struts in the inlet thrust. As an aircraft engine, it is, of course, designed housing. for \vide versatility in terms of ambient pressure and temperature extremes from Arctic to Desert climates. The T-56 has a 14-stage compressor desigend for 32 lbs/sec of air at sea level and 60°F inlet and with a pressure ratio of 8.5:1. To maintain compressor stability at startup, bleeds are provided at the 5th and lOth stages. These are to be noted since they are significant for the conversion to an industrial turbine, as will be discussed later. Six ( 6) cannular combustion chambers are provided and these are designed for operating turbine inlet tern· COOLING peratures up to l970°F during take-off. AIR OUT An interesting feature of this engine is the use of direct reading thermocouples at the combustor outlet, as
Figure 1. Model T56-A-15 Tu bo prop Engine Appli a ion r . Figure 2. Vane Cooling Schematic. c t C-130. 20 CO:\YERSIO:\ OF A. :3!:\GLE-.SIL\FT TCRBOPROP E:\GI:\E
craft auxiliarv ,·omponents. addition uf i ustri l :c:o\·ernor .mel den:'lopment of a :.:as iuel '"·steanm tond replacea the aircrartliqui d fuel �\ :'tenL ln these applications. the
c· n!.>:ine ,- ,·rtlinued lo dri\·e throu:.:it the t o rque meter. pro·
\ · idin g ito power to industrial machiner�· instead of the
p ropelle r .
Ingersoll-Rand. as a manufac turer of compressors and pumps. has been emploving aircraft derivati\·e tur bines to drive their products in industrial service for a number of years. In thev sought a ISO v horsepo11·er industrial prillJme/0. move-r. and made 4000a compr e hensive review of the aircraft engines available that might be emploved. The T-56 had established the outstanding record of operating in industrial service in excess of :)0.000 hours without overhaul. and thereby appeared to highlv qualified for the purpose intended. It suffered befro m one handicap however-the fact that it was a single shaft engine. This limited its usefulness in two (2) ways : l. Speed \ ariation was onh· 12/L
2. .-\s a sinde shaft engine. it could not be used
for a p plicati ons ;uch as liq�id pumps that require a high starting torque capabilitY. �lanv of the potential
uses for a ri ver in this size range are in liquid pump· ing, such asd oil pipelines. A detailed study of the T-56 revealed that bv fortunate coin cidence the thermody Figure 3. Turbin e namics of the r;ower secion of the turbine split almo.s t Air-Cooled Blade. perfecth· between the 2nd and ::lrd turbine stages. In other 11·ords, the power of the first two stages was ade quate for driving the compressor section and the power The T-56 engine completed initial tests and went in to of the 3rd and 4th stages was available as mechanical production in 1956. Since then, more than units shaft output. D DAD was, therefore, approached for a have been built by Detroit Diesel Allison, 10Div.000ision of program of modifying the engine, and agreement was General Motors (DDADl . These power such craft as the reached between the two companies in June of 1970 to Lockeed Electra, Hercules and PB-3 shown in Fig. 4-. proceed with a joint development. The resultant engine By 1963, this engine had demonstrated high reli is shown in Fig. 5. As will be noted, it appears remark abilitv as an aircraft propulsion unit and the manufac ably like the original T-56. The same compressor, com turer decided to offer it for industrial service. It was. bustors and turbine rotor elements are used in both. therefore, introduced into gas pipeline and electric gen � In fact. in the critical aero-dmamic cascade the only erator applications in the original single shaft version . changes are: (a.) A two-degree alteration of the 3rd stage Changes at that time were limited to removal of the air- vane angle ; and (b.) An increase in the stage spacing between the 2nd and 3rd turbine stages of less than lJ:! ". The power turbine takes the 3rd and 4th turbine wheels from the T-56 and moun ts them in an overhung configuration from a separate shaft. The wheels ar� joined by through-bolts as before. and torque is carried through curvic connections. This required the addition of a cun·ic element on the back of the last turbine wheel and removal of the same element from the 2nd and 3rd stage interface. The wheel assemblies and the stator elements continue to be made by DDAD to minimize : I hardware change and to take advantage of quantity pro - _ ·I '- , duction. i ' The power turbine rotor is mounted on two (2) tilting shoe radial bearings in a conventional manner, and a Kingsbury thrust is provided.
Outboard of the thrust bearing, a gear system is built in for driving auxiliaries. These consist of lube oil, compressor seal oil and hydraulic service gear pumps. The gas generator now referred to as the 501-K16
is bolted by external flanges to the power turbine. Trun- · nions on the power turbine casing provide the main sup port for the turbine through a mounting pedestal as illustrated in Fig. 6. Further support is provided above Figure 4. T-56 Applications. the gas generator center of gravitv by a flexible hanger, PROCEEDI:l' POWER TURBINE EXHAUST TWO·STAGE POWU TURBINE Con Be Rotated for flel.bility . Pro�n Design-Centerline Support) Of COUPliNG CONTIHUOUSLV lUBRICATED ACCESSORY GEAR BOX FUEL METERING VAlVE ACCESSORY DRIVE GEAiOOX CURVK COUI'tiiiG CCM!IfcnON FOI LUll SEAl PUMPS BETWHH DISCS & SHAFT & HYDUULK ( 5. Figure GT--f.O Gas Turbine. its purpose being to carry weight only and allow com ports are manifolded to a single modulating valve for plete freedom of movement. Within the power tu rbine. each of the two ( 21 stages at which bleed takes place. the bearing assembly at the hot end is supported from The modulating valves are scheduled as a function of the casing by a system of struts attached tangentially to RPM and compressor inlet temperature. The range of the bearing casing. The rear bearing is essentially sup full op�n to full close is approximately 900 RPM as ported by a flexible plate mounted under the avxiliary illustrated in Fig. 8. The full gas generator operating �ear casin !r. The turbin e diffuser an d exhaust collector speed range is from 10,000 to l-1-,500 RPM correspond �re suppo;ted by struts from the inter-bearin� housing ing to a 1000 to 1-J.,SOO RPM range for the power in the se�tion surroundin g the th rust bearin g. turbine. Because the output drive is now taken from the left The gas generator lube system, combustors and end of the turbine rather than from the front. the me thermocouples remain unchanged from the T-56. The ;_..· .. · ch anical ou tput th rough the gas generator nose has been gas generator turbine blading is unaltered from the T-56 removed. This simply meant leaving off the torque tube and the only significant change in this area is in the and adding a small nose cone to cover the openin�. wheel mounting system. starter drive was needed since the aircraft en�ine Previously, the gas generator turbine had bearing� starterA had been mounted on the propeller gearbox. As on both sides of the wheels. The gas generator turbine mentioned earlier, the engine has four ( -l-1 pads at the stages are now overhung using the same through-bolting compressor inlet for shaft driven auxiliaries. For the and curvic connections as before. The only maj or modi GT--1-0, one of these was used to mount a starter gearbox fication, therefore, was in the bearing. In thesing le developed for the purpose. This box provides a 1:1 shaft engine, this is a 60mm ro# 3ller bearing with a ring ratio to a vane type starter. On the forward face, the spring for vibration suppression between the bearing gearbox carries an electrical speed pickup for control support and the bearing retainer. The ring has twelve purposes. Again, existin g hardware was employed to ( 12 ) lands on the and twelve ( 12) alternately provide the drive from the shaft outward to the starter located lands on the 0.0.I.D. The 0.054 inch thick ring :;earbox . between lands provide the dampening property. When the engine was modified to the two-shaft The bleed connections at the 5th and lOth stages version, it was necessary to enlarge the shaft in this consist of four ( 4) equally spaced ports for each. In �ection to carry the turbine wheels in the cantilevered airc raft service, these are operated full open or full closed arrangement. The bearing diameter was, therefore, in during the acceleration cycle. This system, however, was creased to lOOmm. The design was otherwise retained no� suitable for an industrial prime mover with a wide including the mounting system and the hardware was power and speed range. With only full open or full obtained from the same source as before. Operation closed positions, a void band existed in the power plot. has demonstrated this alteration to be fully satisfactory. The answer lay in modulating the opening of th ese valves in order to eliminate this gap. Fig. 7 shows the 50l Obviously, a basic premise of this program has been K16A gas generator as built. As will be seen, the bleed to minimize alteration from the aircraft engine to take ------.. _ I ��,------· 7-- -_ , ,., ""-" '·'·. · ·. " /'-" .. r r- ··�' -'·' . · . . . I , , -: . ,.. ." ., ..� .-::1- I >'> .- ""t :' 1.4 '• -S l.. U'"'to• �._1<:"� �"11.. 11.• � .. ... ,. �·� - ! • J O ...f.lot (.OJittlll.. I •: " 0 z < M c.o... "l'qo._ ,...... c._ :::0 Ul >--< H,:-. 0 L'; 0 •=a - 1-=-� <>o, · :'. -..1._ >-rj ...... io....--...t__ � -:.... -- ;"-�' 'I ' - < --- i: � -1 - --- ..... +· ' :.=..-...: .j "- TI0 . -- -4-. .•� U- ..:. " .. -i >--< 8� I � 6. Pipeline Compressor Package. Figure GT-40 '"' c." PROCEEDIXGS OF THE SECOXD Tl:RBO:\IACHIXERY SY:\IPOSI"UI SOl-Kl6 GA S GENERATOR 5th Bleed Vibration Pick-up Jl lO th Stage Bleed Ducting Ch ip uf' tec tor Pressure C.I.T. Probe Ad jus tmen t Figure 7. Gas Generator. 50J .K16 advantage of quantity production but even more com facturer for performance and mechanical integrity. These pelling reason was to receive the benefit of the total expe· tests were conducted under load a!!aiL nst calibrated noz· rience of the T.56. On 10,000 units mon itored over a zles. This practice continues to be followed for produc period of years, this experience is considerable and tion units. The completely assembled GT-40 then under· places the en17gi ne far down on its learning curve. There· went a test program at loaded by a shop water brake. fore, all elements of the basic aircraft turbine useful in Approximately 300 hour1-sR were accumulated before ship industrial applications have been kept the same wherever ment of the first unit in late 19 71. Th ese tests closely practical, including metallurgy. One important area is confirmed predictions on the unit output, which woul the knowledge gained from Naval programs on handling be expected since the aero·dynamic components were ofd salt air corrosion (sulphidation ). This is particularly known characteristics. The characteristic of the engine valuable for the many offshore platform applications is sh own in Fig. <) for ISO conditions at sea level and to which the industrial engine will be applied. This 60°F. will be noted, this turbine has an unusually engine was the first to pass a 3000 hour Naval Endurance broad ranAsge of speed at maximum power. The rating Test in !!estin!!� salt.laden air. From that extensive test is based upon a T.I.T. of l800°F. This is a deration ing p rogram, current practice of INC0-738 blading and of 170°F from aircraft take·off levels and with the bene vanes with Alpak coating was developed for units fits of intern ally cooled blades results in an average metal X--Wdestin ed for use in marine environments. temperature in the first stage of approximately 15l0- Conversely, it is interestin g that the aircraft engines 15200F, which is within the creep limits and stress rup have benefited from the industrial program because of ture parameters for the metals used for a targeted life in the accelerated calendar time from which they accumu excess of 100,000 hours. late long hours of operation. During the shop prototype test. only minor modifi. The first 501 gas generator was delivered in the cations were found necessary. These included some summer of 1971 following prototYpe testing by the manu- alteration of the flexible support and pipin g on the COXYERSIOl\ OF .-\ SIXGLE-SH.-\FT TCRBOPROP EXGIXE • F CIT 12 0 ·- �::i�:�: i � I 0 0 ��=�:::+:�::::�: /-�=J::::��=L::· :::)?�;:::.:::::f::::�::: ::::; :�t> ::t::· .. :: :/ i := --::::..... --+-- - :uz: 80 60 40 + 20 0 -20 ··.. ::: .f:. 40 0 0 0 0 0 0 It) It) 0 N 0 0 0 0 0 It) 0 0 0 It) 0 N N ,.., � N I RPM " Figure 8. 501-K16A Engine-rl ccelera tion Bleed System Actuating Range. coupling end of the power turbine, an alteration of the turbine by itself remains an academic curiosity method of mounting the auxiliary gear pinion on the unlessA supported bv a broad design effort to apply it in power turbine shaft, and a change in the support of the a useful manner. This involves a carefully engineered bleed leading from the modulating \·alves to the program of comprehensive packagi ng with driven equip turbineduc e:-chaust.t ment, and a discussion of this turbine develo pment pre sents only a partial picture without a few words about The first unit was placed in industrial service in this supporting effort. Fig. 6 shows the general config of Cities Service as a gas pipeline uration adopted for the GT--lO. coFebruarympressor driver.1912 byTo date, this engine has accumu lated over hours. Subsequen tly, nineteen ( The change from the front drive of the single shaft units were 12.0made00 operable on Oasis Pipeline in the 19\fall turbine to an aft drive and the location of the auxiliary of gear at the coupling end of the turbine has permitted 1912. location of the inlet filter-silencer on the bedplate and a Experience with the turbine to date has been highly straight flow path into the turbine bellmouth. The stan gratifying. No problems have been uncovered in the dard filter configuration has been designed to accept design of the gas generator portion. In the power either inertiaL replaceable media, or mist eliminator fil turbine section. the basic system has likewise pro\·en tering elements. Within this configuration, various de sound. The one area that has required correction has grees of silencing are available depending upon the re been in the auxiliarY gearbox. Several failures were quiremen ts of the jobsite. The inlet system can also be experienced in this section. These were fatigue failures equipped with evaporative cooling for applications with of the gear teeth particularly between the idler and the a dependable low dry bulb temperature. For such ap pump pinion for the seal oil pump. Simultaneously, plications, a power increase of 15 7c or more is possible. there were several ruptures of flexible oil lines connect ing these shaft driven pumps to the system. The units can be furnished \l·ith sound enclosures around the turbine or without. The same applies for These difficulties proved to be caused by pulsations enclosures around the driven apparatus. originating in the gear type oil pumps that were trans mitted to the gears by splined couplings of limited flexi The lubrication system is common for the gas gen bility used in the original design. The situation h as erator, the power turbine and the driven equipment. A been corrected by softening the system through replace reservoir is built into the baseplate and oil filters and ment of the coupling with more flexible types and intro other equipment are included within the section adj acent duction of more flexible hosing on the oil lines. As to the control panel. Because this is an ai rcraft deriva insurance. the gear faces were widened by 5/16 ins. to tive turbine, svnthetic lubricants meeting EMS-53 are reduce tooth loading. employed. PROCEEDIKGS OF THE SECO:\"D TCRBO�IACHI:\"ERY SYMPOSIU:i\I ------� -- -:::.....:··- - -:- : ------·- ··---:---:- - . . ------___ _.;,__..___:':'_-: - -� --:------ 4500 - - c-·- ., --�- :- --·------· ··------: � · ·-·-· .. :·�-�1;--:-�:=-r ..·: - � · : ...-� ��:-:- :::::i 7 ··· 2 4000 ---�� --- -'�------· --_;:.--�:.:_ ��----�----�-�- ·-- � . _ �3 . -�- < <= ��- �------:------�'- �-,.: ------_ ------��,>.; : . . . . � :: .. '-::- -�. : ..._:-�c __;_::::�:_-...:::-'< :...:.:.. : '-:c"�-:.:?1- : 1 •• ------. - -·-- . •. . . --- - - ,_4-:._..:_ : : � ' .. - .. . . ------. --'--··:-:--. ·. . "----- ..�� . , . . . . -- · .. .. '--,c:-· :>--'-::-:" �=:"-:-::---?:---. ; �-:;:: 500 : . ·/ : _.. .. . : , ·-- : '·• ·\·::{+<� :·: . 'L::�·::::- j'� .:.::�!6:1 : : ., : __ ,.. . ; · . : . : \ - :.:� ... .. � . :, : :::�_: ______3 :--�-:-7 --- �------:..,�_____ :.___ .:..�--.:-:---: ,:.::-- :--�--:-::-����:._ . . . . . - . . - . . f-:-··· ··· . :: . - \ ------... - - . .... ·--·- - . -...___� """' ·- �·.:-·- --�-�- ���------� 26 ... ���·==--- : c •.. ·\. 3000 ::��---�� 0 •• _c - / ·""-·-·-·:: --�-; 25 ' : -C�S�-- -E�J-� 7 8 9 1 0 11 12 13 14 - PO�R TURB INE SPEED 1000 RPM Figure 9. GT-4/J Gas Turbine. ISO Performance (60°F at Sea Level) . TIT = 1800°F. Exhaust silencing can be provided to meet various high degree of factory packaging also requires noise requirements as specifi ed. The package configura· a capabilitA y for full factory testing since the principle tion includes a support structure for the exhaust when function is one of minimizing field labor and field needed. correction of flaws. Each unit, therefore, is shop tested Controls are furnished for complete automatic oper· along with its own driven device-pump or compressor. ation. These can be mounted on the baseplate in explo In program of this type, it is sometimes possible to sion-proof housings or they can be mounted off the base· a use existing pumps and compressors from the manufac plate, if preferred. In any event, the baseplate is fully turer's prior designs. To obtain maximum benefit, how wired, and for the remotely located panels all leads are ever, new driven machines are also needed. 10 brought to an explosion proof terminal box on one end. illustrates a pipeline compressor developed for directf; g ,con Because of the variety of fuel requirements encoun nection to this high speed turbine. This compressor is tered, gas, liquid and automatic dual fuel systems have intended for gas volumes and ratios commonly encoun been developed. tered in Gas Transmission and can accept from one (l) .... . I N NER CAS lNG (HORI ZONTHL LY SPLIT) I N NER CA SING RETENTION RING '--- , r'S ihJ' ' r- rm 1 0vu1 BARREL TYPE / CAST STEEL Ct- (1200 PSIG SING-----+----- D ESl��J ) 0 PRECISION C/AST IMPELLERS 0 z < M ::0 [f) I\1EC HAl IIU> l SEAL_ H RE FERE NCE 0 �(OIL F- 1L fv1 I fPl ) GAS � 0 ":1 � [f) H HYDRAULICALLY z MOUNTED COUPLING Cl l' M TILT lNG SHOE if,� q -.�I)-\!_ BEARINGS I :;.:)��I wt'\1� :< --Jij "1 >-l >-l r. ;::1 td OUTER BE ARING AND 0 SEAL DRAIN____/ "d ;::1 0 INNER DRAIN "d SEAL M OIL SUPPLY :/, DRUM Cl H % M RENEWABLE LABYRINTH SEALS INTERSTAGE DIA PHRAGMS VA NE S Figure 10. CDP-416 Compressor Assem bly. '"' -l :2:3 PROCEEDINGS OF THE SECO).'D TL"REG::\IACHIXERY SYl\IPOSIU;\I r - Figure Centregal Compressor. Fi�ure New 250-passenger Hydrofoil Designed by 11. � Boeirz g Com13. pany. to four 1 -t I stages of compression in series or two stages in parallel at higher volumes. will handle flows of ICFM or less at compression Of particular interest is the high compression ratio ratios up to 3000With the very small flows encoun centrifugal with the trade name ·'CENTREGAL" design tered, particularly25-30:1. toward the top of the compression ed to make the turbine useful in ranges, heretofore, large cycle, higher than normal speeds are required for the ly limited to reciprocating machinery. This unusual best aerodynamics. The number rotor in the case oper machine is illustrated in Fizs. and 12. It consists of ates at and the 2nd andl 3rd elements run at three l multi-stage cent:-ifu11gal compressor casings . 20,000RPl\'1. RPMThe particular virtues of this compressor mounted( 3 in a single bundle and directly connected to the 30,000are high efficiency combined with the elimination of turbine a built-in speed increasing gear. This machine couplings between multiple casings strung out in a line. b\- Intercoolinz, of course, is required between casinzs on � ' high ratio applications and this is done external to the compressor. A total of thirteen impellers can be installed or a lesser number if lesstl than3) maximum ratio is needed. novel feature of this compressor is the introduction of drAy face seals in place of conventional oil seals gen used in high pressure gas compressors. The dry erallyseal el iminates the complexities of the seal oil system. Another interesting use for this turbine has been to drive small ships. Fig. illustrates the new, pas- ( senger hydrofoil designed13 by the Boeing Company.250 Pro- pulsion of the ship will be provided by two of these turbines driving water jet pumps. (2) Two shaft turbines of this size have manv uses throughout the world including gas pipelines, oii pipe lines, gas and oil production platforms, LNG plants and other processes. In less than two years of these THIRD STAGE units have been sold for such applications(2) and100 increasing ROTOR useage is anticipated, particularly in rapidly expanding remote areas of the world where pre-engineered, packag DISCHARGE ed compressors and pumps are needed to combat the Figure 12. Centregal Compressor Flow Schematic. energy crunch.