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Air Starting Systems for Marine Gas Turbine Engines

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Air Starting Systems for Marine Gas Turbine Engines 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 I Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1968/79870/V001T01A046/2389833/v001t01a046-68-gt-46.pdf by guest on 25 September 2021 ,__ "' I u.. 100 "'~ I _,"" \ LU' I :J MAIN ENGl~-.!E Cf l/v 0"" 0 IY- " ,__ t \ i\ )- -100 I I \ I I I I -200 ~ I I I\ ! \• -300 ~ 1000 2000 3000 4000 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,
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