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An Integration of the Turbojet and Single-Throat Ramjet
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Author and Affiliation:
Trefny, C. J.(NASA Lewis Research Center, Cleveland, OH United States);
Benson, T. J.(NASA Lewis Research Center, Cleveland, OH United States)
Abstract: A turbine-engine-based hybrid propulsion system is described. Turbojet engines are integrated with a single-throat ramjet so as to minimize variable geometry and eliminate redundant propulsion components. The result is a simple, lightweight system that is operable from takeoff to high Mach numbers. Non-afterburning turbojets are mounted within the ramjet duct. They exhaust through a converging-diverging (C-D) nozzle into a common ramjet burner section. At low speed the ejector effect of the C-D nozzle aerodynamically isolates the relatively high pressure turbojet exhaust stream from the ramjet duct. As the Mach number increases, and the turbojet pressure ratio diminishes, the system is biased naturally toward ramjet operation. The common ramjet burner is fueled with hydrogen and thermally choked, thus avoiding the weight and complexity of a variable geometry, split-flow exhaust system. The mixed-compression supersonic inlet and subsonic diffuser are also common to both the turbojet and ramjet cycles. As the compressor face total temperature limit is approached, a two-position flap within the inlet is actuated, which closes off the turbojet inlet and provides increased internal contraction for ramjet operation. Similar actuation of the turbojet C-D nozzle flap completes the enclosure of the turbojet. Performance of the hybrid system is compared herein to that of the discrete turbojet and ramjet engines from takeoff to Mach 6. The specific impulse of the hybrid system falls below that of the non-integrated turbojet and ramjet because of ejector and Rayleigh losses. Unlike the discrete turbojet or ramjet however, the hybrid system produces thrust over the entire Mach number range. An alternate mode of operation for takeoff and low speed is also described. In this mode the C-D nozzle flap is deflected to a third position, which closes off the ramjet duct and eliminates the ejector total pressure loss.
Publication Date: Nov 01, 1995
Document ID:
19960016375
(Acquired Apr 10, 1996)
Accession Number: 96N22181
Subject Category: AIRCRAFT PROPULSION AND POWER
Report/Patent Number: NASA-TM-107085, E-9963, NAS 1.15:107085
Document Type: Conference Paper
Meeting Information: 1995 Airbreathing Propulsion Subcommittee Meeting; 5-9 Dec. 1995; Tampa, FL; United States
Contract/Grant/Task Num: RTOP 466-02-01
Financial Sponsor: NASA Lewis Research Center; Cleveland, OH United States
Organization Source: NASA Lewis Research Center; Cleveland, OH United States
Description: 14p; In English; Original contains black and white illustrations
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: No Copyright
NASA Terms: CONVERGENT-DIVERGENT NOZZLES; HYBRID PROPULSION; RAMJET ENGINES; TURBOJET ENGINES; THROATS; COMPRESSORS; AFTERBURNING; ENGINE PARTS; EXHAUST GASES; EXHAUST SYSTEMS; SUPERSONIC INLETS; SPECIFIC IMPULSE; MACH NUMBER; PRESSURE RATIO; DUCTS
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