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3 PROPULSION
Pages 46-60

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From page 46...
... Revolutionary advances, especially in engine materials and combustor technology, will be required to design a propulsion system that satisfies performance requirements in terms of emissions, noise, vibration, thrust, weight, fuel efficiency, service life (durability) , and reliability.
From page 47...
... Certerbody Fan Compressor Combustor High Pressure Low Pressure Turbine Turbine
From page 48...
... . Each HSCT propulsion system unit which consists of an air intake, turbofan engine, and exhaust nozzle would be about 50 feet long, weigh 8 or 9 tons, and produce on the order of 60,000 pounds of thrust.
From page 49...
... Second, HSCT propulsion system components will be required to operate at A Turbine airfoil cooling r Single-crystal nickel airfoils Thermal barrier coatings Low emission combustor No-film CMC con~bustor li;;~, Fa'' containment system \ FIGURE 3-2 HSCT engine and exhaust nozzle. Source: NASA.
From page 50...
... The life goal for the turbine airfoils is 18,000 hours. The life goal for the thermal barrier coating is shorter, and it is anticipated that airfoils will be replaced and reused, as necessary, following refurbishment and the application of a new thermal barrier coating.
From page 51...
... Recommendation 3-1. The HSR Program should expand its efforts to develop suitable alloys and thermal barrier systems during Phase II to increase the probability that the airfoil system will satisfy durability and lifetime requirements and to prepare for the recommended technology maturation phase.
From page 52...
... Early in the recommended technology maturation phase, which would follow Phase II, the HSR Program should manufacture and destructively test representative full-scale disk components to verify that manufacturing technologies are feasible and that measured material properties are consistent with design data generated from small samples. Disk performance should be demonstrated in a full-scale engine later in the technology maturation phase.
From page 53...
... Because of this strong dependence, the NOX emissions from an HSCT engine equipped with a conventional combustor would be very high, in the range of 40 to 50 g/kg during supersonic cruise operation. (During cruise, the compressor discharge air temperature is very high in excess of 1200F.)
From page 54...
... Film air cooling is unacceptable because the cooling air would create stoichiometric fuel-air mixtures, which produce high levels of NOx in regions close to the liner. Most of the air flow in RQL combustors bypasses the rich first stage and is introduced further downstream to complete the combustion process.
From page 55...
... Testing is in progress using module and sector test rigs, and NOx emission levels at or near the target value have been demonstrated with versions of both concepts. The HSR Program expects to collect enough data to select a preferred combustor design concept by the scheduled date of May 1998.
From page 56...
... However, nickel alloy liners may not achieve life goals in HSCT applications because of oxidation-induced coating spallation; thermal fatigue and distortion; creep; and melting. Combustor Conclusions The development of ultralow NOX combustor technology will require major advances in both combustor design and associated material technologies.
From page 57...
... Recommendation 3-3a. During the recommended technology maturation phase, the HSR Program should test a full-scale demonstrator engine to reduce uncertainties regarding the viability of the selected ultralow NOx combustor design.
From page 58...
... In order to meet aircraft and propulsion system weight goals, the HSR Program has established performance and weight goals for the nozzle that cannot be achieved using materials, designs, or manufacturing processes typically used for engine exhaust nozzles. The main components of the engine exhaust nozzle are the primary structure, convergent flaps, divergent flaps, noise absorption system, and thermal blanket.
From page 59...
... For this reason, and because of the historical risk involved in developing advanced supersonic engines, an HSCT program launch decision seems quite unlikely unless risk is reduced by demonstrating satisfactory performance of a full-scale, fully integrated engine (during the proposed technology maturation phase) and a full-scale, fully integrated propulsion system (during the proposed advanced technology demonstration phase)
From page 60...
... For example, as part of the AESA project, NASA has made in-flight measurements of emissions from the Concorde. However, an HSCT engine is likely to have a very different thermodynamic cycle from the Concorde's Olympus engines, and NOx emissions from an HSCT engine are expected to be considerably different (NRC, 1997~.


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