Application Of A Vehicular Designed, Heavy Duty Gas Turbine

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THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS 346 E. 47 St, New York, N,Y. 10017 85-GT-125 The Society shall not be responsible for statements or opinions advanced in papers or in discussion 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 in an ASME Journal. Released for general publication upon presentation. Full credit should be given to ASME, the Technical Division, and the author(s). Papers are available from ASME for nine months after the meeting. Printed in USA. Copyright © 1985 by ASME Application of a Vehicular Designed, Heavy Duty Gas Turbine Engine to a Military Generator Set SAMUEL C. LAUX Allison Gas Turbine Division General Motors Corporation Indianapolis, Indiana ROBERT N. WARE U.S. Army Belvoir Research and Development Center Fort Belvoir, Virginia o the stability and transient response advantages of ABSTRACT The Patriot Air Defense Missile System (formerly SAM-D) is being deployed in Europe. The powerplant supplying electricity to the radar set and to the engagement control station is DOD Model D-424A, powered by the Allison Model GT-404 industrial gas turbine (IGT) engine. Designed as a vehicular engine, the application in a generator set is an interesting one, utilizing many of the following features originally intended to enhance the performance of trucks and buses: o Dual, rotating disk regenerators dramatically improve fuel consumption by transferring heat energy from the exhaust gas stream to compressor discharge. o Power transfer, intended to provide part load fuel economy in vehicles, is modified to furnish freeshaft start-fixed shaft run in generator sets. o Free-shaft starts allow successful operation down to -50°F without auxiliary heaters. The resultant gas turbine engine driven generator set--150 kW, transportable, skid mounted, alternating current 400 Hz, tactical--has met the military require ments for performance and reliability. the single shaft engine, while using the fast start and cold start capabilities of the two shaft engine through modification of the vehicular designed power transfer system o multifuel capability without adjustment o improved reliability o the ability to carry two 150 kW generator sets aboard the EPP, each having the capacity to supply the system load for 100% backup To prove that such a set could meet the stringent requirements of performance, size, and weight, Allison elected to build a demonstrator set (Figures 1 and 2), which was delivered for test to Belvoir Research and Development Center, Virginia, in January 1978. GT 404 FEATURES This basic industrial gas turbine engine consists of a gasifier assembly, a power turbine, a combustor, a regenerator system, a reduction and accessory drive gearbox, a power transfer system, and a fuel management INTRODUCTION The Patriot system replaces the Nike Hercules and Hawk systems and will be the primary air defense for the United States until 2000. The system is completely mobile. Electric power (400 Hz) is furnished to the radar set and to the engagement control station (ECS) by multiple turbine powered generator sets mounted on an Army 5-ton truck, called electric powerplant (EPP). The system was funded in 1976, and the name was changed from SAM-D to Patriot. In this same year, Allison and the Army recognized the EPP could be greatly improved if the advantages of the Allison GT 404 could be utilized in the prime mover for the generator sets. These advantages, many of which had been experimentally demonstrated, include the following: o dramatically lowered specific fuel consumption (SFC) through the use of twin, rotating disk regenerators Figure 1. Allison demonstrator set. Presented at the Gas Turbine Conference and Exhibit Houston, Texas — March 18-21, 1985 Downloaded From: http://proceedings.asmedigitalcollection.asme.org/ on 09/18/2017 Terms of Use: http://www.asme.org/about-asme/terms-of-use IGNITER PLUG HIGH TENSION IGNITER LEAD T 1 SENSOR COMBUSTOR T 4 THERMOCOUPLES (BOTH SIDES) LDP (P 2 ) AIR SUPPLY CLEANER EJECTOR TUBES (BOTH SIDES) SHUTOFF RETURN TO TANK OUTLET TO SECONDARY FILTER FUEL LEVEL SWITCHES FUEL TANK VENT INLET FROM PRIMARY FILTER DAY FUEL TANK 7E84-8741 Figure 2. Allison demonstrator set details. system. The primary structural frame of the engine is a two-piece cast-iron block. Air enters the singlestage radial compressor from an inlet filter. The air discharging from the impeller flows through a vane type diffuser and is then directed to the regenerator covers at the sides of the engine. The compressor discharge air then flows inward through the regenerator disks to the combustor. The gases from the combustor are directed to the gasifier turbine nozzle by the turbine inlet plenum. After the gas expands through the gasifier turbine, it flows through the diffuser transition to the power turbine. After expansion through the power turbine, the gases are diffused and directed outward through the two regenerator disks. The gases then exit from the regenerator covers into the exhaust pipes. The mechanical general arrangement of this engine is depicted by the drawing shown in Figure 3. The gasifier assembly mounts into the front of the block with the axis of rotor rotation on the engine centerline. This rotor consists of a single-stage, cast--aluminum, compressor impeller at the front and a single stage, axial flow gasifier turbine wheel attached to a common shaft. The rotor is supported by a ball thrust bearing behind the impeller and a spring-loaded ball bearing in front of the turbine wheel. The two bearings mount into a cast-iron gasifier support that also houses shaft seals and gasifier lube system components. A vane type compressor diffuser mounts between a castiron compressor cover and the gasifier support. The air-cooled gasifier turbine nozzle is supported and piloted at the aft end of the gasifier support. Sheet metal heat shielding surrounds the gasifier support Figure 3. Allison Model GT 404 industrial gas turbine engine. 2 Downloaded From: http://proceedings.asmedigitalcollection.asme.org/ on 09/18/2017 Terms of Use: http://www.asme.org/about-asme/terms-of-use and also serves to duct compressor discharge air to the gasifier turbine nozzle to satisfy cooling require ments and shaft seal environment control. A single can type combustor mounts into the top forward section of the block with its axis aligned on the engine vertical centerline. The combustion gases are directed to the gasifier turbine by means of a sheet metal plenum that encircles the gasifier support. The single fuel nozzle and igniter are attached to a sheet metal combustor dome. This dome also supports the combustor. Internal surfaces of the block that would be exposed to hot gases and radiation from the combustor and turbine inlet plenum are protected by insulation material and sheet metal liners. The single-stage axial flow power turbine, which is aligned with, and is to the rear of, the gasifier turbine, consists of a nozzle assembly, supported from the block center bulkhead, and a rotor, supported on two bearings. These two bearings, a ball thrust bearing immediately behind the turbine wheel and a roller bearing at the aft end of the rotor shaft, are mounted in the forward case of the gearbox. A sheet-metal exhaust diffuser encircles the power turbine rotor support structure. The regenerator system consists of two metal matrix disks, disk seals, cast-iron regenerator covers, and a disk-drive system. A disk is mounted in each side of the block so the axis of rotation is on the engine transverse horizontal centerline. The regenerator drive gearbox mounts to and is driven from the front case of the main engine gearbox. The regenerator covers bolt to the block and direct compressor discharge airflow from the block, inward through the forward portion of the disks and direct turbine exhaust gas outward through the rear portion of the disks, to the exhaust pipes. The main engine gearbox contains the reduction gearing between the power turbine rotor and the engine output shaft and gearing for accessory drives. The engine lube pump, fuel pump, regenerators, and related drive system are driven by the gasifier rotor. Other accessories can be mounted to the gearbox to be driven by the power turbine. A shaft that attaches to the rear of the gasifier rotor and extends through the power turbine rotor into the gearbox provides the drive from the gasifier rotor. This shaft is interconnected by suitable gearing to an oil-cooled, oil-pressuremodulated, multiple -plate clutch that in turn is geared to the power turbine rotor. This system constitutes the mechanical portion of the power transfer system. When the clutch is fully locked up, the engine operates as a single-shaft engine. The principal components of the fuel management system are an electronic control, relay box, electric fuel metering valve, electric clutch servovalve, compressor inlet temperature sensor, thermocouples, and speed pickups. This system provides automatic sequencing of engine starting functions, automatic scheduling of fuel flow and turbine inlet temperature, automatic programming of power transfer clutch engagement, and automatic shutdown protection against abnormal conditions during starting and operation. The system is designed to operate on either 12 or 24 Vdc power. Excellent performance characteristics, high reliability, long endurance life, low life-cycle cost, good maintainability, low emissions, and competitive production cost are prime design goals for this engine. Also, the engine is sized and configured to meet the requirements of the intended applications. DEMONSTRATOR UNIT OBJECTIVES The demonstrator unit objectives included full--authority electronic fuel control with isochronous load sharing governor, load sense, and load pulse. This control was already under development. Control of power transfer clutch was also needed so that start sequencing would occur in the free shaft mode, affording the following advantages: o smaller starter requirement o rapid acceleration of gasifier, causing more rapid acceleration of the driven load to synchronous speed (Clutch lockup occurs and the generator set accelerates fixed shaft to 100% speed, as illustrated in Figures 4 and 5) o better cold start capability o better stability and transient response capability Another objective was tailoring of power turbine speed so that generator set operating speed would fall at the maximum point on the horsepower versus speed curve. In the vehicular designed engine, maximum power occurred at 85% of design power turbine speed. To realize maximum power, the power turbine gear train ratios were altered so that at generator set operating Cooled Exhaust Compessed Air Heated Compressed Air Power Turbine Load Compressor Impeller Modulated Clutch Engagement Figure 4. Power transfer--improved part load fuel economy. Clutch lockup 100 - Turbine inlet temperature I 2000 1600 80 s 60 speed 1200 u_ .1 '5 t c, a ai 7Ta - 800 a E m 40 a F- 400 20 0 1 2 3 4 5 6 7 8 9 Time--seconds 10 11 12 0 TE84 - 8744 Figure 5. Model 404 generator set typical starting characteristics. 3 Downloaded From: http://proceedings.asmedigitalcollection.asme.org/ on 09/18/2017 Terms of Use: http://www.asme.org/about-asme/terms-of-use speed (100% gasifier) the power turbine turns at 85% of design speed. Three-phase alternating current 400 Hz generator development was another objective. To meet the stringent requirements of size, weight, and performance, Delco Products Division of General Motors agreed to develop a special 3000 rpm, 16-pole alternator having an aluminum mainframe and end frame. Existing components and parts were used wherever possible. The electronic control for the alternator incorporates advanced electronic design and features highly reliable digital displays for volts, amps, hertz, and kilowatts. To meet the generator set weight limitation (4650 lb/2109 kg)--another objective the skid base, enclosure, and control cabinet are fabricated of tempered aluminum. The engine-generator assembly is hard mounted to the skid base, utilizing the rigidity of the engine generator to help stiffen the entire structure, again saving weight. Where feasible, castings such as the rear gearbox and exhaust elbows were changed to aluminum. To meet the length requirement (96 in./244 cm), it was necessary to bring combustion air in through right and left air inlet louvers, through self-cleaning inertial particle separators on each side, into a central plenum, and then into the engine inlet. Electrical and mechanical tests were conducted at Belvoir; electromagnetic interference (EMI) tests were run at Aberdeen; and durability and environmental tests were conducted at Allison. The test program served the dual purpose of confirming that the demonstrator met the basic requirements and pinpointing areas of deficiency requiring correction. In mid-1978, a contract was let for design, development, and construction of five militarized generator sets and some testing of the sets. The objective of this design effort was to militarize the generator set fully while addressing the deficiencies revealed in testing the demonstrator set. o reduce the number of malfunction indicators to 11 o rearrange controls for Army human engineering compliance o reduce height of module to allow larger cooling air inlet o add document compartment o add full-time voltage display o separate short-circuit and overload indicator battery charging alternator--protect from battery 6. polarity reversal, suppress for radio frequency interference (RFI)/EMI These objectives were incorporated into the redesign effort along with corrective action for all other areas of deficiency identified by military testing. Testing of the five militarized sets included the following: o roadability and railroad impact testing at Aberdeen o completion of mechanical and electrical tests and retests where appropriate at Belvoir o environmental tests at Eglin AFB o system development testing (DT) at White Sands Missile Range o system operational testing (OT) at White Sands At the conclusion of DT/OT II testing in the summer of 1980, an excessive number of relevant mission essential (RME) failures had been scored against the EPP and the generator set. It was, therefore, decided to implement all known corrective actions for the deficiencies revealed in the DT/OT test program, which were the following: o incorporate fuel day tank float switch with higher frequency response o incorporate Zener diode to limit voltage spike in cranking motor circuit o deactivate lube dump solenoid o incorporate finer primary fuel filter in a pressurized location o install proven manual fuel shutoff valve o install captive fasteners in generator regulatormonitor o reinforce skid base for roadability o center generator rotor at installation to improve balance o install structurally stronger oil cooler Subsequent to these actions, a reliability, availability, maintainability demonstration (RAM/DEMO) was conducted by Army personnel and was run from September 1980 to October 1981. During that time 5418 generator MILITARIZED UNIT OBJECTIVE The objectives for the militarized unit (Figure 6) included the following: redesign skid base 1. o utilize 4-in. (10.16 cm) height increase made possible by removal of truck bed from EPP o increase fork tunnel height o incorporate removable engine front support o add tie-down rings o add ground stud o add chain hook slots 2. redesign enclosure o incorporate roof section in two pieces for improved access and easier handling o simplify compartment bulkhead design and accommodate changes required to move oil cooler plumbing out of the rear (electrical) compartment o improve door sealing for noise reduction and electromagnetic pulse (EMP) resistance o add military paddle latches to all doors o relocate cooling air inlet from rear side panels to lower rear panel plumbing changes--redefine fuel, air, and oil 3. hoses and fittings to preclude improper installation safety shielding--add safety shielding to high4. voltage ac electrical connections and to dc battery connections redesign control module 5 o eliminate engine gages 4 Downloaded From: http://proceedings.asmedigitalcollection.asme.org/ on 09/18/2017 Terms of Use: http://www.asme.org/about-asme/terms-of-use o Patriot demonstrator, Allison • Patriot demonstrator, Ft. Belvoir set hours were logged at a mean time between failure (MTBF) of 417 hr. Since this performance exceeded the minimum requirement, the system testing resumed with such test programs as the following: o component design confirmation (CDC) o system design confirmation (SDC) o collective training o follow-on evaluation (FOE) 120 m o - Patriot procurement spec 110 MIL-STD-1474A Category C Category D 0 - _ -2 100 - RESULTS 0 The following initially recognized advantages of the GT 404 have been realized: o Specific fuel consumption was dramatically lowered. The pre-GT 404 EPP I consumed 48 gal/hr at system load. EPP II consumes 16 gal/hr. o Frequency stability at rated load at 0.1% and frequency transient response to meet the Patriot system requirements, proving the superior performance of the fixed-shaft engine in generator set applications, were demonstrated. o Free-shaft start allowed starting to -50°F without heaters and contributed to rapid acceleration to running speed. o Multifuel (diesel, JP, gasoline) capability without adjustment was demonstrated. o Generator set reliability requirements were met and are being further improved. o Sound power level requirements were met with only the attenuation of the regenerators and the enclosure (Figure 7). o All performance requirements of the Army Purchase Description were met or resolved. In December 1981, delivery of production generator sets began; over 200 generator sets are planned. Over 30,000 hr have been logged on production sets, and de ployment to the U.S. Army Europe has begun. The development, testing, and production of the D-424A generator set, employing a prime mover designed -0 c z 90 - d .._. °• Li '-' • I._._. 80 70 63 250 1000 4000 dBa Octave band center frequency--Hz TE84-8746 Figure 7. Allison generator set noise levels at operator position. primarily for vehicular application, is an example of the excellent results that can be achieved through realistic cooperation between Government and industry. BIBLIOGRAPHY Best, G. C., and Flanigan, E. E., "Allison GT 404- The VIP Engine-Versatile Industrial Power," American Society of Mechanical Engineers (ASME) paper 72-GT-93, March 1972. Flanigan, E. E., and Nigro, D. N., "Field Experience with the Detroit Diesel Allison 404/505 Industrial Gas Turbine Engines," Society of Automotive Engineers (SAE) paper 790129, March 1979. 5 Downloaded From: http://proceedings.asmedigitalcollection.asme.org/ on 09/18/2017 Terms of Use: http://www.asme.org/about-asme/terms-of-use