Optimization for the Starting Process of Turbofan Engine Under High-Altitude Environment

A potential need has been identified for a High Altitude Long Endurance (HALE) aircraft to augment current surveillance and engagement capability. HALE platforms offer mission flexibility and survivability which can complement ground based surveillance and engagement systems. Current mission requirements include a loiter altitude of 45,000 to 60,000 feet and a loiter time of 12 to 24 hours. The HALE aircraft will also be required to carry a sensor payload weight between 50,000 and 100,000 pounds. This paper will evaluate the potential of several propulsion system candidates. Engines to be examined include the “classical” turbofan engine with bypass ratios up to eight, the “ultra high bypass ratio” turbofan with bypass ratios up to 20, General Electric’s Unducted Fan (UDF) and the turboprop in a pusher and tractor configuration with single and counter rotation propfans.

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Modeling of a Turbofan Engine Start Using a High Fidelity Aero-Thermodynamic Simulation

Volume 1: Aircraft Engine; Ceramics; Coal, Biomass and Alternative Fuels; Controls, Diagnostics and Instrumentation ◽

10.1115/gt2012-70141 ◽

2012 ◽

Cited By ~ 4

Author(s):

Igor Fuksman ◽

Steven Sirica

Keyword(s):

Thermodynamic Simulation ◽

Operating Regime ◽

High Fidelity ◽

Iterative Solver ◽

Turbofan Engine ◽

Conservation Of Energy ◽

Directional Flow ◽

Modeling Techniques ◽

Starting Process ◽

Engine Start

Simulating the thermodynamics of a multi-spool turbofan engine during engine start can present challenges to the conventional high fidelity aero-thermodynamic simulation. The conventional high fidelity aero-thermodynamic simulation uses an iterative solver technique to preserve flow continuity and conservation of energy based on component maps and subsystem characteristics. Traditionally, operation of such simulations have been limited to regions from self-sustaining idle to maximum power, where component and subsystem representation has been well defined and engine operating pressures are sufficient to ensure one-directional flow. However, simulating transient operation which initiates from engine “off” condition followed by starter engagement and fuel introduction, presents a new set of challenges. These include the modeling of the engine “off” state itself, as well as two aspects of the starting process particular to a multi-spool turbofan: the modeling of the flow passing through the entire core stream even though only the high pressure shaft is rotating, and the modeling of the flow split into the bypass stream when the fan is not rotating. This paper discusses the modeling techniques that have been developed to overcome these challenges in order to ensure the smooth operation starting with engine off and continuing through the regions of starter engagement, fuel addition, and starter disengagement leading to normal engine operating regime.

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Development and Testing of a Commercial Turbofan Engine for High Altitude UAV Applications

10.4271/2001-01-2972 ◽

2001 ◽

Cited By ~ 1

Author(s):

Maurice Weinberg ◽

John Wyzykowski

Keyword(s):

High Altitude ◽

Turbofan Engine

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Contrast of Filament Bright Rims

International Astronomical Union Colloquium ◽

10.1017/s0252921100025628 ◽

1994 ◽

Vol 144 ◽

pp. 365-367

Author(s):

E. V. Kononovich ◽

O. B. Smirnova ◽

P. Heinzel ◽

P. Kotrč

Keyword(s):

High Altitude ◽

Line Profile ◽

Line Center ◽

Magnetic Structures ◽

The Mean

AbstractThe Hα filtergrams obtained at Tjan-Shan High Altitude Observatory near Alma-Ata (Moscow University Station) were measured in order to specify the bright rims contrast at different points along the line profile (0.0; ± 0.25; ± 0.5; ± 0.75 and ± 1.0 Å). The mean contrast value in the line center is about 25 percent. The bright rims interpretation as the bases of magnetic structures supporting the filaments is suggested.

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Clean Electron Microscope Substrate Films Used for Micrometeorite Collection and Study

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100061847 ◽

1967 ◽

Vol 25 ◽

pp. 366-367

Author(s):

D. M. Davies ◽

R. Kemner ◽

E. F. Fullam

Keyword(s):

Thin Film ◽

Electron Microscope ◽

High Altitude ◽

Amyl Acetate ◽

Temperature Variations ◽

Film Forming ◽

Film Specimen ◽

Particulate Contaminants

All serious electron microscopists at one time or another have been concerned with the cleanliness and freedom from artifacts of thin film specimen support substrates. This is particularly important where there are relatively few particles of a sample to be found for study, as in the case of micrometeorite collections. For the deposition of such celestial garbage through the use of balloons, rockets, and aircraft, the thin film substrates must have not only all the attributes necessary for use in the electron microscope, but also be able to withstand rather wide temperature variations at high altitude, vibration and shock inherent in the collection vehicle's operation and occasionally an unscheduled violent landing.Nitrocellulose has been selected as a film forming material that meets these requirements yet lends itself to a relatively simple clean-up procedure to remove particulate contaminants. A 1% nitrocellulose solution is prepared by dissolving “Parlodion” in redistilled amyl acetate from which all moisture has been removed.

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