24 research outputs found
Propulsion System for Very High Altitude Subsonic Unmanned Aircraft
This paper explains why a spark ignited gasoline engine, intake pressurized with three cascaded stages of turbocharging, was selected to power NASA's contemplated next generation of high altitude atmospheric science aircraft. Beginning with the most urgent science needs (the atmospheric sampling mission) and tracing through the mission requirements which dictate the unique flight regime in which this aircraft has to operate (subsonic flight at greater then 80 kft) we briefly explore the physical problems and constraints, the available technology options and the cost drivers associated with developing a viable propulsion system for this highly specialized aircraft. The paper presents the two available options (the turbojet and the turbocharged spark ignited engine) which are discussed and compared in the context of the flight regime. We then show how the unique nature of the sampling mission, coupled with the economic considerations pursuant to aero engine development, point to the spark ignited engine as the only cost effective solution available. Surprisingly, this solution compares favorably with the turbojet in the flight regime of interest. Finally, some remarks are made about NASA's present state of development, and future plans to flight demonstrate the three stage turbocharged powerplant
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NACA Research Memorandums
Report presenting a study of four short annular diffusers with different diffuser passage area variations and with various combinations of straightening vanes, vortex generators, splitters, and boundary layer suction for flow control. Results regarding turbine discharge whirl, diffuser passage modification, and boundary layer control are provided
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NACA Research Memorandums
From Introduction: "The purpose of the investigation conducted at the NACA Lewis laboratory and reported herein was to determine the improvements possible in full-scale turbojet-engine performance when a single-annular combustor with slotted air-inlet orifices was used.
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NACA Research Memorandums
Report presenting an investigation at conditions of zero ram and seal-level pressure to determine the effect of inlet temperature and humidity on turbojet engine performance with injection of water and water-alcohol mixtures at the compressor inlet
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NACA Research Memorandums
An investigation was made comparing the performance of JFC-2 fuel and unleaded, clear gasoline in a 3000-pound-thrust turbojet engine. The JFC-2 fuel was a blend of percent diesel fuel and 25 percent aviation gasoline. Engine combustion efficiency was equal to that obtained with gasoline at rated engine speed and altitudes up to 35,000 feet, but at lower engine speeds or at higher altitudes the JFC-2 fuel gave lower combustion efficiency. No discernible difference was obtained in starting or low-speed combustiion blow-out characteristics of the two fuels. Turbine-discharge radial temperature profiles were nearly the same at altitudes up to 35,000 feet