Design and Performance Features of the Marine LM1600 Gas Turbine

THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS P345 E. 47 St., New York, N.Y. 10017 90-GT-203 C The Society shall not be responsible for statements or opinions advanced In papers or In discusslon at meetings of the Society or of its Divisions or Sections, or printed in its publications. Discussion is printed only if the pape, is published In an ASME Journal. Papers are available from ASME fort fteen months utter the meeting. Printed in USA. Copyright 1990 by ASME Design and Performance Features of the Marine LM1600 Gas Turbine J. M. THAMES, H. B. STUEBER, and C. T. VINCENT General Electric Corp., Cincinnati, OH ABSTRACT The GE LM1600 gas turbine is a lightweight, efficient prime mover for commercial and military marine applications. This gas turbine is a derivative of the F404 fighter jet engine whose mission objectives strongly emphasize reliability and ease of maintenance in an austere marine environment. These objectives were important to the U.S. Navy because the F/A-18 fighter jets powered by this engine are based on aircraft carriers where parts warehousing and maintenance capabilities are limited. To achieve these objectives, component designs were simplified and the total number of components was substantially reduced. These features and its modular construction make the LM1600 attractive for marine applications. Numerous marine propulsion system configurations are possible, including various combinations with diesel engines and steam gas turbines as well as options for shaft or electric drive. The first commercial installation of the marine LM1600 gas turbine is in progress and sea trials will commence in late 1990. This paper describes the design, performance, installation, and maintenance features of the marine LM1600 gas turbine. now operating successfully (Thames, 1989). As of 31 December 1989, the LM1600 gas generators have accumulated 15,000 hours of operation. The first LM1600 marine gas turbine will be installed in a private, high-speed yacht. The gas turbine installation will be complete at the time of this paper presentation. In addition to this installation, a complete engine module and accessories package is being developed by MTU Friedrichshafen. This will be a rugged, lightweight module designed for military vessels (Beiner and Lattermann, 1990). GAS TURBINE DESCRIPTION Derivation The LM1600 marine gas turbine consists of a gas generator connected to a single-shaft power turbine by a transition duct. The gas generator has two concentric shafts connecting the low and high pressure compressor and turbine rotors. A cut-away drawing is shown in Figure 1. INTRODUCTION Small size, light weight, and low specific fuel consumption over a wide power range make the LM1600 an excellent match for marine applications. In addition to marine propulsion, LM1600 gas turbine applications include pipeline compression, offshore platform power, industrial power production, and cogeneration. The LM1600 can operate in simple cycle or in steam injected configurations (Thames, 1989) The first LM1600 gas generator went into service in 1988 in a pipeline compression application (Farmer, 1988) and several other industrial installations are FIGURE 1: LM1600 CROSS-SECTION 'Presented at the Gas Turbine and Aeroengine Congress and Exposition June 11-14, 1990 Brussels, Belgium

The LM1600 is derived from the F404 fighter jet engine, selected in 1975 by the U.S. Navy to power the F/A-18 Hornet. The Navy's mission objectives strongly emphasized reliability and ease of maintenance since the F/A-18 Hornets would be based on aircraft carriers with limited parts storage and maintenance capabilities. To achieve these objectives, a major design goal of the F404 was to simplify the engine design through significant reductions in the total number and complexity of parts and individual components (Fogg, 1984). The F404 design philosophy also departed from traditional convention in that the engine was designed and tested against the actual aircraft mission. The F404 entered service on 18 November 1978. One test requirement was a Simulated Mission Endurance Test which included U.S. Navy minimum reliability standards. The F404 completed this test on schedule in July 1980 with results that bettered the Navy's standards by a factor of 3.5:1. Since November 1978, over 1600 F404's have been shipped to support 600 active aircraft and these engines have accumulated more than 1.4 million flight hours. Reliability, as measured by in-flight shutdowns, is two to six times better than other, current in-service fighter engines. The LM1600 gas generator is a straightforward modification of the F404 and directly benefits from the F104's design, extensive testing (Pace, 1988), and accumulated operational experience. The component simplification was carried through to the LM1600 gas generator, resulting in a simple and rugged engine. A 22:1 pressure ratio is attained in ten compression stages and only a single stage each is required for the high and low pressure turbines. The LM1600 incorporates advanced aircraft engine technologies in aero-turbine design, cooling techniques, and materials; and as a result, is the most efficient engine in its power class. The light weight (gas generator weight is only 2,500 pounds and total gas turbine weight is 6,665 pounds) and modular construction of the LM1600 offer ease of maintenance as well as high availability. The durability in marine environments, high power-to-weight ratio, and simplified maintenance are important factors in marine service. Design HPC Module (2) LPC Combustor HPT LPT Module (1) Module Module Module (1) Includes LPC casing not shown (2) Includes HPC casing not shown FIGURE 2: GAS GENERATOR COMPONENTS Exhaust Frame A compressor variable geometry control and bleed air system are used for startup and operation at low power levels. The gas turbine assembly also includes an inlet air bellmouth and bulletnose cover over the front frame hub to streamline air flow into the low pressure compressor. The combustor is the same machined ring design used in the F404. This is a short residence time, flow-through annular type combustor fitted with eighteen externally mounted fuel nozzles. Combustion air is brought in through swirl cups centered on each of the nozzles to thoroughly mix the fuel and air and attain high combustion efficiencies. Secondary air flows between the combustor liner and case and enters the liner through a series of primary and secondary dilution holes. This combustor represents a low pressure loss, high efficiency design with no smoke and very low unburned hydrocarbon emissions. The design and number of required bearings are important factors affecting in-service reliability. The gas generator has only 5 main bearings - 3 roller bearings and 2 ball thrust bearings. Figure 3 shows the gas turbine shaft arrangement and supporting bearings. Numbers 1 and 3 are the thrust (ball) bearings designed to absorb axial thrust during operation. No 6 No I No. 2 No 3 No 4 No 5 roller bearing The gas generator rotating elements are a three-stage low pressure compressor driven by a single-stage low pressure turbine and a seven-stage high pressure compressor driven by a single-stage high pressure turbine. All stages are axial flow. The single stage low and high pressure turbines are fully air cooled with low-aspect ratio blades. The gas generator components are shown in Figure 2. FIGURE 3: GAS GENERATOR SHAFT AND BEARING ARRANGEMENT

The power turbine is a two-stage uncooled design with a ball bearing for thrust loads and a roller bearing for shaft support (Figure 3). The power turbine assembly includes a transition duct which is attached to the gas generator exhaust frame extension through a rabbeted, bolted joint. Power is delivered through the shaft at the aft end of the gas turbine assembly. The power turbine design shaft speed is 7,000 rpm (clockwise rotation when aft looking forward into the output coupling flange) and can operate at either constant speed for electrical power generation or on a cubic load curve for mechanical drive applications. The power turbine exhaust gases pass through a diffuser and then are turned 90 degrees in the marine exhaust collector to exit in the vertical direction. The power turbine and exhaust collector are shown in Figure 4. The LM1600 gas turbine uses the same synthetic lube oil as the LM2500. In the LM1600, the gas generator and power turbine share the same synthetic lube oil reservoir and conditioning system, but are serviced by separate gas generator gearbox driven lubrication supply and scavenge pumps. Marinization Corrosion of gas turbine hot section components is a life limiting factor in marine service. The LM1600 is inherently corrosion resistant due to its base materials and hot section coatings. Its hot section component base materials are the same as those used in the highly successful and experienced marine LM2500. To further improve life in marine service, LM1600 hot section components are coated with the same corrosion resistant material applied to the LM2500 turbine nozzles. This coating is plasma sprayed on the LM1600 high pressure turbine nozzle and blades and the low pressure turbine blades. PERFORMANCE The LM1600 simple cycle thermal efficiency is greater than 37 percent (ISO). In addition to low specific fuel consumption, the engine offers advantages in ship service through its rapid start, acceleration, and deceleration capabilities. If needed, the LM1600 can be brought on-line and ramped to full power in less than two minutes. The LM1600 marine gas turbine, in new and clean condition, is rated as shown in Table 1. TABLE 1: LM1600 PERFORMANCE FIGURE 4: POWER TURBINE WITH MARINE EXHAUST COLLECTOR Output Brake Horsepower Specific Fuel Consumption Exhaust Gas Flow Exhaust Gas Temperature Power Turbine RPM Power Turbine Rotation 20000 HP (14914 kw) 0.383 'b/hp-hr (23 g/kwh) 102 lb/sec (46 kg/sec) 955 F (513 C) 7000 Clockwise, Aft Looking Forward Rating Conditions The external manifolds shown in Figure 4 supply air for sump pressurization and balance piston air to assist in relieving the aft forces on the power turbine bearings. The power turbine air manifold is attached to a mating connection on the gas generator by a simple "V" band clamp. Low temperature cooling air is taken from the low pressure compressor bleed casing cavity, and additional higher temperature cooling air is collected from the turbine inlet. For balance piston pressurization, the two flows are mixed in the manifold before entering the balance piston area (see Figure 3). The sump pressurization air is provided by the low pressure compressor air only. The balance piston and sump pressurization air are sent through tubes in the power turbine frame to the inner cavities. To prevent turbine flowpath gases from entering internal cavities, additional air flows to these cavities from the external manifolds through tubes inside each power turbine nozzle. Engine Inlet Air Temperature Ambient Pressure Intake/Exhaust Losses Relative Humidity Bleed Air Extraction Fuel LHV Average, New E Clean 59 F (15 C) 14.7 psi (1.013 bar) 0 60% 0 18,400 Btu/lb (42,800 kj/kg) Per GE Liquid Fuel Specification No. MID-S-0000-2 A performance map of LM1600 power variation as a function of compressor inlet temperature including lines of exhaust gas temperatures and flow rates is presented in Figure 5. A second performance map of power variation as a function of power turbine speed (representing a cubic load curve) is presented in Figure 6. This map also includes lines of specific fuel consumption. The information in these two figures is based on estimated average engine performance.

LM1600 Gas Turbine Estimated Average Performance INSTALLATION AND APPLICATIONS Gas turbine advantages in ship propulsion include increased ship speeds, payloads, and mission capabilities at low fuel consumption, noise and exhaust emissions, and weight/space to power output..iui 1401 120 g II 1Z bill Fn 20 40 60 60 100 120 tb Compressor inlet air temperature - T2 deg F t.,1n4 0.t Vaa (fm4b) dry F _ ^ amlaa amn., 9 to. tw6) DR:. FIGURE 5: POWER vs COMPRESSOR INLET TEMPERATURE LM1600 Gas Turbine Estimated Average Performance The gas turbine can be packaged for diverse applications such as patrol boats and larger navy vessels, commercial ships (e.g. cruise liners, LNG carriers, container ships, and fast ferries) and private yachts. The propulsion system can be a gas turbine-only system, a combination gas turbine-diesel, or a gas turbine-steam system for driving traditional propellers or large water-jets. The ship propulsion system can be configured with mechanical drive as combined diesel and gas turbine (CODAG), combined diesel or gas turbine (CODOG), or gas turbine only (COGAG/COGOG), or gas turbine and steam (COGAS) arrangements. The engines can also be used in the newer Integrated Electric Drive (IED) arrangements. The first LM1600 marine installation uses a combined diesel and gas turbine (CODAG) system with three water jets; two wing jets for maneuvering on diesels and a large central jet for sprint with the gas turbine. This private yacht installation features a transom exhaust design which offers significant advantages in increased deck space and lowers ship cross-sectional profile. If uncooled, exhaust gas will be at relatively high temperatures and this must be considered in various ship harbor maneuvers. Analyses have been conducted for the first installation to establish air temperature versus distance from the ship stern and no operational problems are foreseen. 16000 2 14000 S 12000 C 10000 6000 w` Un.. 01 toadlk Nai (SFCtm4Rp-N The gas turbine can be installed as a complete module (Beiner and Lattermann, 1990) or can be installed in an engine room provided that adequate cooling is available. The gas turbine and its accessory components are capable of operation under the following conditions: Permanently trimmed a maximum of 5 degrees on either end from the normal horizontal plane. Permanently listed a maximum of 15 degrees on either side of the vertical plane. Momentarily (10 seconds duration) trimmed a maximum of 10 degrees up or down from the normal horizontal plane. 0 0 1000 2000 3000 4000 5000 6000 0000 Power turbine speed - XNSD, RPM FIGURE 6: POWER vs POWER TURBINE SPEED Momentarily (10 seconds duration) listed a maximum of 45 degrees to either side of the vertical plane. Major gas turbine component weights are summarized below and general dimensions are provided on Figure 7. 4

Optional Mounting Links (Typ) Component Weights Gas Generator with Bellmouth 2560 lb (1164 kg) Power Turbine with Diffuser 4100 lb (1864 kg) Exhaust Collector 1250 lb ( 565 kg) Compressor Inlet Screen 365 lb ( 165 kg) Uiinensions in inches (mm) MAINTENANCE FIGURE 7: MARINE LM1600 DIMENSIONS The light weight and modular construction of the LM1600 offer ease of maintenance as well as high availability. The LM1600 design incorporates modular construction techniques. The use of modular construction increases availability by simplifying maintenance as well as permitting on-board replacement of individual modules without a complete engine teardown. The LM1600 uses the "on-condition" maintenance concept which is maintenance based on observed condition, not on a fixed time interval. Maintenance work can be described by the following categories: Preventive Maintenance - Includes both on-line parameter monitoring and periodically scheduled preventive maintenance procedures and inspections. Compressor water wash is considered preventive maintenance. Corrective Maintenance - Maintenance required to correct an operating abnormality or to correct an observed out of limit condition. This can include anything from a simple leak correction to a complete gas turbine replacement. Scheduled Maintenance - Hot Section Refurbishment (HSR) and Overhaul (OH) fall into this category. HSR is replacement of the hot section components (as necessary) after a certain number of operating hours. The time between HSR is highly dependent on the ship mission profile; particularly the percentage of time at maximum power operations. In typical marine service, the gas generator will normally operate another 8,000 to 10,000 hours after a HSR at which time a second HSR would be performed. This pattern can continue until a total of 50,000 hours has been accumulated. Then, a complete gas turbine OH must be performed at a shore-based facility. Scheduled/Preventative Maintenance Tasks The only planned maintenance in the first interval before HSR will be the routine operational parameter monitoring, preventive maintenance tasks, and any corrective maintenance that is necessary to correct operational faults. Preventive maintenance tasks which require an engine shutdown are scheduled on a semi-annual basis. Completion of these tasks typically requires 8 hours and two people. The only special tools that are required for the LM1600 preventive maintenance program are a boroscope set, an optional boroscope inspection drive motor, a digital multimeter, and an adapter set for the exhaust gas thermocouple (T48) harness. These can be provided by GE. Also, an inventory of spare parts is maintained in GE's Product Support Distribution Center at the Cincinnati International Airport for all current LM products to provide rapid delivery worldwide. The list of specific preventative tasks to be performed are shown in Table 2. Task TABLE 2: PREVENTIVE MAINTENANCE TASKS Monitor operational safety parameters Walk around visual inspection Lube system filters (duplex) Waterwash Gas path inspection (boroscope) Inlet inspection Lube system chip detector inspection Lube system strainer inspection Sample lube oil Ignitor inspection Visual inspection of all piping and brackets Inspection of inlet guide vane linkage Inspection of HP compressor variable geometry linkages Inspection of variable bleed valve linkages Exhaust gas thermocouple resistance check Inspection of gas turbine mounting system Hot Section Repair Scheduled Frequency Continuous Weekly or after long shutdowns On-Condition On-Condition A HSR may be accomplished on-board using a rotatable hot section module, available from GE under the On-Site Hot Section Refurbishment program, or by removing the hot section module and sending it to a repair shop for refurbishment. At the users option, the complete gas generator could be sent to a repair shop for accomplishment of a HSR. The rating point defined in the Performance section of this paper has an estimated hot section repair interval (HSRI) of 2,000 hours; this assumes that the gas turbine runs only at the full power rating point for the entire 2,000 hours. In typical marine applications, the operation time at full power is small compared to the operation time over the entire power range. This mission profile extends the HSRI. The HSRI for typical marine mission applications is estimated to be in excess of 8,000 hours, dependent on specific engine rating conditions and ship operating profile.

SUMMARY The LM1600 gas turbine will enter marine service in 1990 backed by engineering expertise from the F404 fighter jet program and industrial operating experience. The very high power-to-weight ratio and high simple cycle efficiency make this engine an excellent match for marine propulsion needs. The simple and modular construction features increase availability and simplify maintenance which is a significant advantage for shipboard servicing. REFERENCES Farmer, R., "GT-60 Turbine Powered by an LM1600 Gas Generator is Rated at 18,000 Hp", Gas Turbine World, December 1988. Fogg, H.E. and Miller, H.E, "GE LM1600 Aircraft-Derivative Gas Turbine System" GE Gas Turbine Reference Library Document No. GER-3466, 1984. Beiner C. and Lattermann, R. "A nouncing the LM1600 Marine Gas Turbine Module", 35t n ASME International Gas Turbine and Aeroengine Congress and Expositions, June 1990. Pace, R.A., The Industrial Aeroderivative Gas Turbine: Beneficiary of Extensive Aircraft Engine Testing", 1988 ASME COGEN-TURBO, 2nd International Symposium on Turbomachinery, Combined-Cycle Technologies and Cogeneration, IGTI-Vol.3, September, 1988. Thames, J.M., Casper, R.L, and Vincent, C.T., "Efficient, Clean Cogeneration with the GE LM1600", 1989 ASME TURBO-COGEN Conference, 3rd International Symposium on Turbomachinery, Combined-Cycle Technologies and Cogeneration, IGTI publication no. 1-00291, September, 1989. Thames, J.M, and Coleman, R.P, "Preliminary Performance Estimates for a GE Steam Injected LM1600 Gas Turbine", ASME Paper No. 89-GT-97. CONVERSION FACTORS CONVERSION FABLE FROM ENGLISH TO STANDARD INTERNATIONAL UNITS Multiply By To Obtain ( in) Inch 2.54 x 10-2 Meter (ft) Feet 0.3048 Meter (um) Microns 10-6 Meters (lbs) Pounds (Mass) 0.4535924 Kilograms (psi) Pounds per square inch 6894.757 Newtons per square meter (ksi) 1000 Pounds per square inch 9894757 Newtons per square meter (fps) Feet per second 0.3048 Meters per second (9pm) Gallons per minute 6.30902 x 10-5 Cubic meter per second (Btu) British thermal units 1055.056 Joules (btu) Heating value 3.7259 x 10-4 Joules per cubic water at TUATT 288.150, 101.3509 ('F) Degree Fahrenheit (*F + 459.67) Degrees kelvin