68-GT-46

not be responsible for. state­ ments or opinions advanced in papers or in dis­ cussion at meetings of the Society or of its Divisions or Sections, or printed in its publications. Discussion is printed only if the .paper is published )~O in an ASME journal or Proceedings. Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1968/79870/V001T01A046/2389833/v001t01a046-68-gt-46.pdf by guest on 25 September 2021 $1.50 PER COPY Released for general publication upon presentation ¢ TO ASME MEMBERS Copyright © 1968 by ASME

Air Starting Systems for Marine Gas Turbine Engines

P. B. GARNER Project Engineer, AiResearch Manufacturing Co. of Arizona, A Division of The Garrett Corp., Phoenix, Ariz. Mem. ASME

B. A. FULMER AiResearch Manufacturing Co. of Arizona, A Division of The Garrett Corp., Phoenix, Ariz.

The advent of large gas turbine engines aboard marine vehicles has created a demand for starting systems suitable for marine application. This paper discusses marine requirements and describes and discusses applicable pneumatic starting sys­ tems. In addition, a comparison between pneumatic and other starting methods will be presented.

Contributed by the Gas Turbine Division of The American Society of Mechanical Engineers for presentation at the Gas Turbine Conference & Products Show, Washington, D. C., March 17-21, 1968. Manuscript received at ASME Headquarters, January 23, 1968. Copies will be available until January 1, 1969.

SOCIETY OF MECHANICAL ENGINEERS, UNITED ENGINEERING CENTER, 345 EAST 47th STREET, NEW YORK, N.Y. 10017 Air Starting Syste,ms for Marine Gas Turbine Engines

P. B. GARNER B. A. FULMER

INTRODUCTION Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1968/79870/V001T01A046/2389833/v001t01a046-68-gt-46.pdf by guest on 25 September 2021 that, in general, pneumatic equipment developed The increasing use of large gas turbine en­ for aircraft service should be readily adaptable gines aboard certain types of marine vessels, to marine service, The emphasis given to the notably high-speed craft, has resulted in a demand weight of aircraft equipment assures the lowest for lightweight, efficient, and reliable starting weight possible consistent with the requisite life systems. The pneumatic starting systems initially and reliability, Magnesium, used on some aircraft developed for aircraft turbine-propulsion engines components, is easily replaced by aluminum without logically provide the most excellent choices for significantly affecting weight or strength. The these starting applications. This paper describes resultant equipment, consisting essentially of ano­ and discusses various system concepts applicable dized aluminum and stainless steel, features low to marine installations and describes the opera- weight, strength, and corrosion resistance at high tion and traces the evolution of important starting temperatures. components from their aircraft system origins. In addition, a comparison between pneumatic, hydrau­ TURBINE STARTING lic, and electric starting methods will be pre­ sented. There are normally two possible methods for starting large gas turbine engines -- by applica­ MARINE REQUIREMENTS tion of direct shaft power to rotate the compres­ sor-turbine group, or by impinging air directly Many of the present marine installations of upon either the turbine blades or the compressor the gas turbine engine are found on high-speed blades to effect rotation (impingement method). craft, such as large planing-hull boats, hydro­ Starting by the direct-rotation method is foils, and ground-effect vehicles. These applica­ usually accomplished by utilizing shaft-power out­ tions place an emphasis on weight, in addition to put from electric motors, hydraulic motors, or bine the usual marine requirements of corrosion and pneumatic devices such as air turbine starters. effic fire resistance, The starting device is generally mounted upon the placE In displacement-type hulls, weight addition main-engine starter pad and, upon being energized, does not critically affect top speed. In large drives the appropriate gear train and motors the ment planing hull and hydrofoil applications, however, basic rotating group of the turbine engine. turbi maximum speed is power-limited, and weight addi­ Starting by the impingement method is accom­ capac tion reduces the maximum speed attainable. Simi­ plished by directing a large volume of low-pres­ with larly, weight is very critical on ground-effect sure air through a special starting nozzle ring vehicles due to the large lift-power requirements. that directs the air against a compressor blade and i Marine equipment must operate in a very cor­ section or a turbine blade section. The aerody­ Inc or rosive environment. Poor ventilation and the ever­ namic forces created result in an application of engin' present salt water conspire against corrosion­ torque about the axis of rotation and, consequent­ resul · sensitive materials. ly, result in rotation of the turbine-compressor gine. group. One final marine requirement that must be cause mentioned concerns fire-hazardous materials. The Representative torque-speed curves for air start.' presence of volatile fuels and the relatively poor turbine starters and large turbine engines are placen ventilation below deck on marine craft create the shown in Fig.I, that t situation where the presence of any additional An adc combustible material, such as hydraulic fluid, is PNEUMATIC STARTING SYSTEMS od occ undesirable. In this regard, pneumatic equipment existi is to be favored over hydraulic equipment. Impingement Starting pro vis The requirements outlined above suggest The impingement method for starting gas tur-

2 400

r--..... 300 ~ ~ i.,..--ATS ~ '~ 200

I I'-. I

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SPEED, RPM Fig.I Main engine and air turbine starter starting characteristics

bine engines has many limitations -- notably, low the engine to allow placement of a starting nozzle efficiency and initial design difficulties in ring, incorporation of the nozzle would be very placement and sizing of the starting nozzle ring. difficult. The large energy requirements of the impinge­ The system weight of an impingement start ment method (three to five times that of an air system is as high or higher than the weight of a turbine starter) necessitates use of a much higher low-pressure air turbine starter system, The capacity air source than direct shaft rotation weight of the starting nozzle ring approaches that with use of an air turbine starter. of the air turbine starter, but the weight of a Design problems involved in initially sizing gas turbine compressor air source sized for im­ and installing a starting nozzle ring are numerous. pingement is appreciably higher than a gas turbine Incorporation of a starting nozzle ring on a new compressor air source for air turbine starting. engine design requires accurate prediction of the resultant torque-speed characteristics of the en­ Air Turbine Starting gine, The aerodynamic mismatch that exists be­ Pneumatic starting by direct shaft rotation cause of the large difference in airflow between is accomplished by utilizing a pneumatic starting starting and engine operation requires accurate device known as an air turbine starter, Placement of the starting nozzle ring to ensure The air turbine starter (ATS) is a small ma­ that the required starting torque is generated. chine consisting basically of a nozzle ring and a An additional disadvantage of the impingement meth­ single-stage turbine. Compressed air is ducted od occurs when an attempt is made to retrofit an through a differential pressure regulator (control existing engine for impingement starting. Unless valve), and is directed by the nozzle ring onto Provision was made during the original design of the turbine wheel, which converts pneumatic energy Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1968/79870/V001T01A046/2389833/v001t01a046-68-gt-46.pdf by guest on 25 September 2021

er.

Fig.3 Air turbine starter (ATSlOO)

and Fig.2 Gas turbine compressor (GTC95-3) re1 poJ.: dra (pressure and volume) to mechanical (rotational) to energy to drive the main-engine rotating group. There are two modes of operation possible ing with the air turbine starter -- high pressure and c1u low pressure. Some air turbine starters have noz­ GTC zles sized for high-pressure operation; others wei have nozzles sized for low-pressure operation, and, by in addition, some have split nozzle rings designed car to operate on either high- or low~pressure air. dim The high-pressure starting method requires a len high-pressure source of compressed air (250 to 3000 Fig.4 Jet fuel starter (JFSlOO) psi), usually supplied by a reciprocating compres­ sor or other positive-displacement device. The compressed-air source charges air bottles, which, engine starting is the use of engine-mounted, low­ (JF after being charged, provide compressed air for pressure air turbine starters pneumatically driven ize starting. A disadvantage of the high-pressure by a remotely installed small gas turbine compres­ Fig starting method is the added weight of the high­ sor (GTC). The gas turbine compressor is started sta pressure compressor and storage system, in appli­ electrically, hydraulically, or pneumatically. sis· cations where there is no secondary requirement Low-pressure compressed air (30 to 60 psia) is turl for high-pressure compressed air. A more definite bled from the gas-turbine compressor and ducted to comi disadvantage is the hazard created by the presence a differential pressure-control valve, which pro­ turI of the high-pre'ssu1°e air system, vides the proper pressure and airflow to be ex­ Whi• One of the best means of large gas turbine panded through the single-stage air turbine start- gin,

4 COMPRESSED AIR GAS TURBINE JET FUEL SOURCE COMPRESSOR STARTER

AIR OR OR SUPPLY JFS +

IMPINGEMENT IMPINGEMENT Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1968/79870/V001T01A046/2389833/v001t01a046-68-gt-46.pdf by guest on 25 September 2021

ADDITIONAL ENGINE + STARTING CROSS BLEED CROSS BLEED

EMERGENCY 2ND APU JFSON STARTING 1"'"" AIR ""'"""'BOTTLE SECOND MAIN o5 0 ENGINE Fig,5 Pneumatic starting systems schematic comparison

er. Output torque is multiplied by an internal ing air from the first engine to drive the JFS speed reducer, and is transmitted to the engine free-turbine section or air turbine starters starter drive through an overrunning clutch and mounted on the additional engines. starter output shaft. Additional engines may be Fig.5 shows a schematic comparison between started by cross-bleeding from the first main en­ various pneumatic starting systems. gine to air turbine starters mounted on the other engines. OTHER STARTING METHODS The GTC/ATS system provides a lightweight and compact arrangement of components of proven Alternative starting systems remaining in­ reliability for starting, with utilization of a clude direct-shaft rotation of the main turbine en­ power source capable of providing pneumatic, hy­ gine by hydraulic or electric motors. draulic, or electrical auxiliary power in addition Hydraulic starting is accomplished by provid­ to starting power. ing hydraulic power to hydraulic motors mounted on Typical components that are capable of meet­ the main-engine starter pad or gearbox. The hy­ ing present-day turbine starting requirements in­ draulic pumps can be driven by whatever auxiliary clude the Models GTC95-3 and ATSlOO. The Model power is available, such as a small gas turbine GTC95-3, capable of 160 pneumatic horsepower, engine or a more conventional diesel engine. For weighs 297 lb and has dimensions of 20 in. in dia example, hydraulic starting was chosen for two by 36 in. in length, Fig,2. The Model ATSlOO, Pratt and Whitney FT-41s aboard the U.S. Coast capable of 100 hp output, weighs 26.5 lb and has Guard Cutter WPc-715 due to the availability of dimensions of 81/2 in. in dia by 101/2 in. in accessory shaft power for hydraulic pumps from length, Fig.3. diesel generator sets on board. The primary disadvantages of hydraulic Jet Fuel Starting starting systems are system complexity and system Main-engine starting by the jet fuel starter weight. Hydraulic system complexity is illus­ (JFS) represents a new concept. This method util­ trated by a typical aircraft installation, the izes a self-contained small gas turbine engine, U.S. Army YCH-5l+A helicopter. In addition to the Fig,4, which mounts directly on the main-engine basic components (APU, gearbox, gearbox-mounted starter pad or gearbox. The jet fuel starter con­ pumps, and engine-mounted hydraulic starters), its sists of a gas generator section (compressor­ system includes: three start-valves, two check s turbine) which burns jet fuel to yield products of valves, one relief valve, one pressure reducer, ed combustion. These gases are directed upon a free three filters, one hydraulic system reservoir, one turbine (i.e., not connected to the gas generator), hydraulic accumulator (for APU starting only), one x- Which produces shaft power to rotate the main en­ hand pump, and many high-pressure and low-pressure gine. Additional engines may be started by bleed- hydraulic lines, Fig.6. Contrast this system with

5 START VALVE HYD MAIN PUMP STARTER ENGINE

GEAR BOX

APU HYD PUMP STARTER Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1968/79870/V001T01A046/2389833/v001t01a046-68-gt-46.pdf by guest on 25 September 2021

CHECK VALVE & ORIFICE

HYD MAIN START STARTER ENGINE VALVE START VALVE

RESERVOIR

ACCUMULATOR Fig.6 Hydraulic starting system

r:.. PERMANENT MAGNET GENERATOR

ATS MAIN APU ENGINE START_/ VALVE c q STARTER rr. LOAD CONTROL VALVE d

[ MAIN ENGINE BLEED VALVE t

t i h BATTERY MAIN ENGINE ATS e g CHECK VALVE J START VALVE g Fig.7 Pneumatic starting system t s g the typical pneumatic starting system shown in a maximum starting torque requirement of approxi t i Fig.7. mately 45 ft-lb, compared with representative The weight of hydraulic starting systems for torque requirements, depending on the installa­ i small turbine engines, as in the example just tion, of 275 ft-lb for the Pratt and Whitney FT­ T cited, is competitive with other systems. How­ and 250 ft-lb for the GE LM-1500 -- engines that s ever, the JT-12A engines on board the YCH-54A have are currently being considered for marine propul 0

6 Table l Starting System Weights Comparison

ELECTRIC HYDRAULIC PNEUMATIC

APU WEIGHT ( INCLUDES ) STARTER/GEN. 128 130 150

ADDED GEARBOX WEIGHT 10 10 Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1968/79870/V001T01A046/2389833/v001t01a046-68-gt-46.pdf by guest on 25 September 2021 ELECTRIC GENERATOR/ HYDRAULIC 100 28 PUMP

STARTER <2> 260 130 53

ADDITIONAL SYSTEM * WEIGHT 10 25 20**

TOTAL WEIGHT POUNDS 508 323 231

* INCLUDES RESERVOIR **INCLUDES 2 STARTER VALVES

sion applications. The increase in weight of hy­ EVOLUTION AND GROWTH OF THE GAS TURBINE draulic components due to increasing power re­ COMPRESSOR AND AIR TURBINE STARTER quirements is considerably higher than with pneu­ matics. Thus, it is to be expected that the hy­ The advent of turbine-powered military air­ draulic starting systems for marine turbine en­ craft in the mid-1940ts caused the U.S. Navy Bureau gines being installed at the present time are con­ of Aeronautics to propose development of the air siderably heavier than comparable pneumatic sys­ turbine starter (ATS) in conjunction with small tems would be. This is demonstrated in Table 1. auxiliary gas turbine compressors (GTC) to provide Secondary, but by no means minor, disadvan­ low weight-to-horsepower ratio starting units. tages of hydraulic systems include the flammabil­ The end products of this program were the first ity of hydraulic fluids and the existence of the air turbine starter, the Model ATS35, and a gas high-pressure hydraulic lines (3000 to 4000 psi). turbine compressor, the Model GTC43/44, both manu­ Electric starting would be accomplished by factured by AiResearch. electric motors mounted on the main turbine en­ Sinc1 this development work in 1947, over gines. The electric power could be provided by 50,000 starters have been built. These starters generators driven by auxiliary power engines. At have been used or are being used on the majority the present time, however, there are no electrical of USAF and USN aircraft and on all major commer­ starting systems for large marine gas turbine en­ cial airlines. Starters are available today that gines. The large starting power requirements of range in power from 15 to 400 hp and in weight these engines result in electrical equipment that from 4 to 50 lb.

\Te is much too heavy and too costly for consideration The original starters, which evolved from in comparison with other possible starting means. the Model ATS35, were designed to meet military Table l shows the weights of starting systems de­ specifications that had life requirements on the signed to meet the minimum starting requirements order of 600 starts and 500 hr of main-engine op­ Of the GE LM-1500 engine. eration. At the present time, with an accumula-

7 COMPRESSOR AIR INLET COMBUSTOR Q

TAP F AIRS Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1968/79870/V001T01A046/2389833/v001t01a046-68-gt-46.pdf by guest on 25 September 2021 EMER STAR" --j=> TURBINE EXHAUST

TURBINE

c=::> AMBIENT AIR cr::r¢> COMPRESSOR AIR COMPRESSOR r::=> TURBINE GAS Fig,8 Gas turbine (GTCP95-2) flow path stage, lo ca tE radial tion of over 46 million starts and 81 million hr enginE of operation on previous models, newer air turbine starters are experiencing an overhaul life ranging produc from 2500 to 6000 starts and 5000 to 12,000 hr of grams, engine operation. In addition, a life-between­ qualif overhaul expectancy of 1000 starts and 3000 hr elever (main-engine operation} under severe environmental 72, wl:. conditions is anticipated on new military units. ma tic On commercial aircraft, AiResearch air-turbine Model starters are experiencing a premature removal rate flow o of less than 0,20 per 1000 hr of engine operation. day co As an example of the evolution of small gas Percen turbine compressors since their introduction in flow a the late 1940's, the development and growth of one GTCP95 particular series of AiResearch engines is dis­ Power cussed here. lnin (1 The present line of moderate-sized gas tur­ bines suggested for large turbine engine starting ~ange ! Lncludes the Model GTC95-3 (160 air horsepower} tfally Uld the Model GTCP95-2 (combined 160 air horse­ CJ;>aft . _>ower or 200 shaft horsepower) engines. These ar engine Fig,9 Gas turbine engine (GTCPl65) single-shaft, constant-speed engines with a two- for bo1

8 GAS TURBINE ENGINE

LOW PRESSURE) ( AIR SOURCE

LOAD CONTROL AND CHECK VALVE

TAP FOR SHIPS AIR SUPPLY Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1968/79870/V001T01A046/2389833/v001t01a046-68-gt-46.pdf by guest on 25 September 2021 EMERGENCY CONTROL VALVE\ MAIN ENGINE START SYSTEM ~ BLEED AIR ->@,:------f ATS

\CHECK VALVE

ATS

Fig.10 Marine starting system

stage, centrifugal compressor, a tangentially Another engine type worthy of discussion located single-can combustor, and a single-stage, here is the larger APU, capable of providing rea­ radial-inflow turbine. The airflow path of these sonable shaft-power output simultaneous with main­ hr engines is depicted in Fig.8. engine starts, and capable of higher shaft power 'bine These engines have evolved from a series of output under normal running conditions. A typical iging product-improvement and performance-upgrading pro­ engine capable of this type of operation is the ' of grams, beginning with the Model GTC85-10 that was Model GTCPl65, Fig.9, designed as an auxiliary 1- qualified by the United States Navy more than power unit for the Lockheed C-5A Aircraft, This eleven years ago and continuing through the GTC85- engine consists of a single-stage centrifugal com­ mt al 72, which has also been used extensively for pneu­ pressor, an annular combustor, and a two-stage ;s. matic starting purposes in the Navy, The new axial-flow turbine, It is capable of providing Model GTC95-3 has a minimum, full-load bleed air­ 165 lb per min (2160 SCFM) of bleed air or 118 lb rate flow of 140 lb per min at 59 F, standard sea-level per min (1540 SCFM) combined with 150 shp at 59 F, ;ion. day conditions (1830 SCFM). This represents a 20- standard sea-level day conditions. gas percent increase over the Model GTC85-72 bleed The Model GTCPl65, designed specifically to .n flow at 2 in. Hg higher pressure, The Model operate under wide variations in bleed and shaft~ GTCP95-2 is capable of providing 200 hp shaft power loads, represents the type of engine that is ,_ power with no bleed flow or 100 shp and 110 lb per well suited to the demands of future marine appli­ min (1440 SCFM) combined load. cations, Over 15,000 gas turbine engines in this size An essential component in the GTC/ATS start­ range have been built. The major application, ini­ ing system is the control valve. This is a pneu­ .) tially, was installation on ground carts for air­ matically operated, so1enoid-control1ed differen­ craft starting, At the present time, this type of tial-pressure-regulator that also acts as a shut­ engine is being used extensively aboard aircraft off valve. These valves are sized to the require­ ro- for both starting and auxiliary power purposes. ments of the system.

9 GENERATOR

START INITIATION MAY BE FROM GAS TURBINE ENGINE BAl.ERY. AIR BOTTLE. OR HYDRAULIC ACCUMULATOR WITH HAND PUMP

LOW PRESSURE) ( AIR SOURCE

EMERGENCY STARTING FOR

GAS TURBINE GENERATOR SETS Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1968/79870/V001T01A046/2389833/v001t01a046-68-gt-46.pdf by guest on 25 September 2021 BLEED VALVE

ATS HI-LO STARTER

MAIN ENGINE BLEED AIR

r PRESSURE REGULATING VALVE I

SHUTOFF AND REGULATOR VALVE TO PSIG> \ <3.000 35

3.000 PSI

HIGH PRESSURE -<1' STORED AIR ~-~---- 3.000 PSI

Fig.11 Marine starting and auxiliary power system

MARINE APPLICATIONS (4) USS Hartley, D. E. Class - starter and valve for an There are presently nine notable marine ap­ press or. plications in which pneumatic starting systems are (5) USS Dennison, used for turbine engines, These applications can turbine compressor and pneumatic start system. be categorized by: (a) high-pressure air for (6) ESSO Zurich, Commercial Tanker - starting turbine prime movers; (b) high-pressure and valve for a small gas-turbine-driven ballast air for starting large auxiliary power units; (c) pump. a gas turbine compressor for engine starting only; (7) USS America, Aircraft Carrier - Gas and (d) a gas turbine engine for main-engine turbine engines driving load compressors starting and for supplying auxiliary and/or emer­ craft starting. gency power. Figs,10 and 11 illustrate possible (8) Royal Danish Navy Frigate marine installations. Starters and valves for the P and WA (1) AGER Hydrofoil - Gas turbine compres­ (9) USS Kingbird, Minesweeper - Dual-mode sors and air turbine starters for General Electric starters and valves for two Orenda OT-41s, LM1500 Engines. (2) DeHavilland FHE 400 Hydrofoil - Gas VERSATILITY OF THE GAS TURBINE turbine compressor/emergency power unit and COMPRESSOR-AUXILIARY POWER UNIT starter for the Pratt and Whitney FT4 Engine. (3) High-pressure starters and valves for The gas turbine auxiliary emergency electric power units aboard 18 DLG class lightweight and compact source of power ships. any combination of shaft-power and c

10 needs. It can operate reliably under very adverse by bleed from the APU. conditions on almost any type of liquid or gaseous (b) Engine Starting, Emergency Mode -- High­ bydrocarbon fuels. Gas turbine engines can pro­ pressure compressed air, stored in air bottles pre­ vide almost any combination of hydraulic or elec­ viously charged by ship-supplied, high-pressure tric power and high-pressure compressed air, and compressed air, would start one main engine through low-pressure compressed air can be provided by the high-pressure port and nozzle section of a integral bleed from the engine compressor section, dual-mode air turbine starter, The second main The small gas turbine auxiliary power unit engine could be started by cross-bleed from the (APlJ), used in combination with air turbine start­ first engine. ers mounted on main turbine engines, provides many (c) Auxiliary or Emergency Power Supply -­ combinations of starting modes and auxiliary or The APU would supply low-pressure compressed air, Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1968/79870/V001T01A046/2389833/v001t01a046-68-gt-46.pdf by guest on 25 September 2021 emergency power, For example, an APU with a hy­ hydraulic power, and electrical power for auxili­ draulic pump and an electric generator, and with ary or emergency needs. air turbine starters mounted on each of two main (d) Propulsion Power -- The APU, in addi­ turbine engines, could be operated in all of the tion to providing some auxiliary power, would pro­ following modes: vide shaft power for propulsion, (a) Engine Starting, Normal Mode -- The APU The redundancies inherent in such a system, would supply low-pressure bleed air to start one combined with the proven reliability of the system main engine, The second main engine could then be components, would result in high system relia­ started by cross-bleed from the first engine, or bility.

1ress ne c

Gas m. Star last

as air kram ine. mode

s a