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Comparison of Ceramic Vs. Advanced Superalloy Options for a Small Gas

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Comparison of Ceramic Vs. Advanced Superalloy Options for a Small Gas E AMEICA SOCIEY O MECAICA EGIEES 88G228 4 E. 4 S., ew Yok, .Y. 00 e Sociey sa o e esosie o saemes o oiios aace i aes o i is cusso a meeigs o e Sociey o o is iisios o Secios o ie i is uicaios. iscussio is ie oy i e ae is uise i a ASME oua. aes ae aaiae: ] om ASME o iee mos ae e meeig_ ie i USA Copyright © 1988 by ASME Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1988/79191/V002T04A010/2397688/v002t04a010-88-gt-228.pdf by guest on 28 September 2021 Comaiso o Ceamic s. Aace Sueaoy Oios o a Sma Gas uie ecoogy emosao . OEMISA, . AIE Susa uomac Sa iego ASAC requirements can be cost-effectively fulfilled by the simple cy- cle gas turbine operating at relatively low pressure ratio and The next generation of small gas turbines used as com- turbine inlet temperature without the benefits of multi-staging pact Auxiliary Power Units (APUs) in aircraft and mobile and turbine cooling as customary on larger propulsion engines. ground power applications will achieve higher power density The need to increase the power density without sacrific- than current installations by operating at substantially higher ing simplicity and cost demands higher pressure ratios and cy- turbine inlet temperatures. Ceramics vs. advanced/cooled su- cle temperatures resulting in a corresponding increase in stage peralloy designs are compared as alternate paths to improved loading and wheel tip speed. Figure 1 shows the estimated prfrn thrh nrd trbn nlt tprtr fr specific power output of a small APU as function of turbine the T-100 MPSPU (Multi-purpose Small Power Unit) technol- inlet temperature (TIT) and pressure ratio based on the ex- ogy demonstrator engine currently under development. pected component efficiencies. The increased aero-thermo re- Past experience at Sundstrand Turbomach in demonstrat- quirements require advanced structural materials, better (inno- ing ceramic and air cooled components is used to project level vative) utilization of the material properties and a reassess- of success expected in meeting the demonstrator engine per- ment of accepted cooling techniques. formance goals with either ceramics or advanced/cooled super- An advanced small gas turbine APU, the T-100 currently alloy radial turbine nozzle and turbine wheel. The alternate under development at the authors' company, will be used to designs are compared in terms of potential against such crite- investigate the feasibility of increasing the engine shaft power ria as performance, power density and cost. output by operating at higher turbine inlet temperature and IOUCIO shaft speed. Preliminary analysis of the engine performance indicated that the power output of the single-stage radial in- Future aircraft and armored vehicles will require more flow turbine can be practically doubled by operating at turbine secondary power with little or no allowance for a correspond- inlet temperatures in excess of 2000°F. Based on previous ing increase in size and weight of the power source: the small experience, two alternate design philosophies were selected, gas turbine Auxiliary Power Unit (APU). In addition to the high performance structural ceramic materials on the one hand high specific power output, the APU design criteria include and an air-cooled turbine nozzle in combination with a multi- such requirements as quick and reliable start, multi-fuel capa- alloy turbine wheel on the other. bility, self-sufficiency and high operational reliability while de- The final design and procurement of the test hardware is livering the optional electric and/or compressed air power un- in progress at the preparation of this paper. The design ap- der the most extreme environmental conditions of cold, heat, proaches and discussion of the two alternate designs are given humidity, dust and altitude. Past experience shows that these below. esee a e Gas uie a Aeoegie Cogess Amseam, e eeas—ue 6, 88 .0 0. S ( Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1988/79191/V002T04A010/2397688/v002t04a010-88-gt-228.pdf by guest on 28 September 2021 0.8 0. 0.E 0 80 0 00 0 20 0 40 0 SECIIC OSEOWE (sIS IG . SECIIC OWE A UE COSUMIO AS UCIO O UIE IE EMEAUE A ESSUE AIO WI COSA COMOE SIE. UAE 00 EGIE ECOOGY sections discuss background and experience with ceramic and EMOSAIO cooled radial turbine components at Sundstrand Turbomach. The T-100 MPSPU is a gas turbine technology demon- ISOY O CEAMIC ECOOGY O strator under development at Turbomach with sponsorship EOMACE UAIG A UOMAC from the Aviation Applied Technology Directorate (AATD) of the U.S. Army Aviation Research & Technology Activity Uprating of small radial turbines using ceramic materials (AVSCOM). The MPSPU program will provide the technology began at Turbomach in 1972 with the testing of hot pressed base for small gas turbines in the 50 HP to 100 HP range, silicon nitride vanes the 100 HP Titan gas turbine (Ref. 1). compatible with applications in airborne or armored vehicle Although the primary intent of using ceramic vanes was im- auxiliary power units and mobile tactical shelter Integrated proved erosion resistance, the favorable high-temperature Power and Environmental Control Systems (IPECS). This pro- properties of ceramics offered the capability for increased TIT. gram involves a wide range of technology advances including In single-stage radial inflow turbines, the nozzle vanes--being improved aerodynamics for low specific fuel consumption, an exposed to the highest gas temperatures--are the prime candi- integral inlet particle separator, advanced combustor, digital dates for ceramic application. electronic control system with diagnostic capability and im- The early demonstration led to work on ceramic compo- proved durability, reliability and maintainability; all supporting nents for the Turbomach Gemini turbine shown in Figure 2. the concept of lower cost of ownership for Army users. The The Gemini is rated up to 45 SHP with single-stage rotor unit production cost goal for the baseline (50 HP) MPSPU speed of 93,800 RPM and turbine wheel diameter of 4.4 inches power module is approximately two-thirds of similar size (112 mm). Under a U.S. Army Mobility Equipment Research units. The durability goal includes capability to ingest three and Development Command sponsored research project, a full pounds each of 'C-Spec' and AC coarse sand with less than ceramic turbine nozzle was successfully tested for 200 hours 10% power loss. The reliability goal is 3000 hours minimum and 50 starts in a Gemini engine (Refs. 2, 3 & 4). Also, the mean time between removals (MTBR). erosion resistant ceramic vane Gemini nozzle concept was car- The uprated version of the T-100 MPSPU of nominal ried through a low-cost manufacturing feasibility demonstra- 100 SHP considered in this paper will be designed and demon- tion with qualification hardware completing over 2000 hours of strated along two parallel concepts: one using high-tempera- engine test (Refs. 5 & 6). (See Figure 3.) ture ceramic materials and the other with nozzle cooling in Demonstration of ceramic vanes, a full ceramic nozzle combination with an advanced tri-alloy metallic turbine wheel. (Figure 4) and all ceramic static components in the entire hot This effort will provide the unusual opportunity to evalu- section was followed by the design and testing of ceramic tur- ate and compare an advanced ceramic design and an advanced bine wheels in the Gemini engine in 1985 and early 1986. This metallic design throughout the development process. At this project was carried out as the first task of the internally funded writing, each of these schemes are in the preliminary analysis long-range Ceramic Technology Development Plan. and design stage. Each will be implemented as hardware and The T-20G10C ceramic Rotor No. 1 (Figure 5) was be carried through development tests. tested for 100 hours at 100 percent speed, 1800 ft/sec tip speed In order to provide a better perspective on the two tech- and full engine power output at a TIT of 1850°F (1010°C). nology options for uprating the T-100 MPSPU, the following Rotor No. 2 was subjected to cycling tests: 50 cold start cycles 2 turbine wheel into small pieces. The wheel burst was barely noticeable, characterized by a light thump and the loss of en- gine power. Hardware damage was limited to the turbine noz- zle. Examination of the turbine section after wheel burst clearly showed that the failure was completely contained and that containment can be easily accomplished with a ceramic wheel. The progression of ceramic hardware demonstrations in the Gemini engine is summarized in Figure 6. The results of Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1988/79191/V002T04A010/2397688/v002t04a010-88-gt-228.pdf by guest on 28 September 2021 these tests have demonstrated the future potential of ceramic 4- components in small gas turbine engines and the need for im- proved materials, design and manufacturing methods. Current efforts at Sundstrand Turbomach are continuing for the design and testing of ceramic static and rotating compo- nents operating at temperatures in excess of 2000°F (1090°C). The ceramic technology development tasks include the devel- . r opment of new design and analytical techniques, nondestruc- tive and destructive material evaluation methods and the fabri- tn nd f r nn hrdr n l pr IG 2. UOMAC GEMII GAS UIE tion with the suppliers of the ceramic parts. EMEAUE UAE MEA AOY to full load in less than ten seconds were followed by 50 full AEAIES load-no load cycles. After successful completion of the cy- cling tests, the rotor was subjected to an endurance test at full During the past 35 years, the intensive materials re- engine speed (93,800 RPM) and an estimated TIT of 1900°F search--primarily driven by the needs of the gas turbine indus- (1038°C).
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