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  • Aircraft Propulsion and Power
  • 2005-2009  (88)
  • 1950-1954  (5)
  • 2005  (88)
  • 1953  (5)
  • 1936
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  • 2005-2009  (88)
  • 1950-1954  (5)
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  • 1
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    High-Frequency, High-Temperature Fretting Experiments (2005)
    In:  CASI
    Details
    Publikationsdatum: 2018-06-12
    Beschreibung: Fretting is a structural damage mechanism observed when two nominally clamped surfaces are subjected to an oscillatory loading. A critical location for fretting induced damage has been identified at the blade/disk and blade/damper interfaces of gas turbine engine turbomachinery and space propulsion components. The high-temperature, high-frequency loading environment seen by these components lead to severe stress gradients at the edge-of-contact. These contact stresses drive crack nucleation and propagation in fretting and are very sensitive to the geometry of the contacting bodies, the contact loads, materials, temperature, and contact surface tribology (friction). To diagnose the threat that small and relatively undetectable fretting cracks pose to damage tolerance and structural integrity of in-service components, the objective of this work is to develop a well-characterized experimental fretting rig capable of investigating fretting behavior of advanced aerospace alloys subjected to load and temperature conditions representative of such turbomachinery components.
    Schlagwort(e): Aircraft Propulsion and Power
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 2
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    Internal Mixing Studied for GE/ARL Ejector Nozzle (2005)
    In:  CASI
    Details
    Publikationsdatum: 2018-06-02
    Beschreibung: To achieve jet noise reduction goals for the High Speed Civil Transport aircraft, researchers have been investigating the mixer-ejector nozzle concept. For this concept, a primary nozzle with multiple chutes is surrounded by an ejector. The ejector mixes low-momentum ambient air with the hot engine exhaust to reduce the jet velocity and, hence, the jet noise. It is desirable to mix the two streams as fast as possible in order to minimize the length and weight of the ejector. An earlier model of the mixer-ejector nozzle was tested extensively in the Aerodynamic Research Laboratory (ARL) of GE Aircraft Engines at Cincinnati, Ohio. While testing was continuing with later generations of the nozzle, the earlier model was brought to the NASA Lewis Research Center for relatively fundamental measurements. Goals of the Lewis study were to obtain details of the flow field to aid computational fluid dynamics (CFD) efforts and obtain a better understanding of the flow mechanisms, as well as to experiment with mixing enhancement devices, such as tabs. The measurements were made in an open jet facility for cold (unheated) flow without a surrounding coflowing stream.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: Research and Technology 1996; NASA-TM-107350
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 3
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    Effect of Tabs on a Rectangular Nozzle Studied (2005)
    In:  CASI
    Details
    Publikationsdatum: 2018-06-02
    Beschreibung: In a continuing research program, jets from nozzles of different geometries are being investigated with the aim of increasing mixing and spreading in those flows. Flow fields from nozzles with elliptic, rectangular, and other more complex cross-sectional shapes are being studied in comparison to circular nozzles over a wide Mach number range. As noted by previous researchers, noncircular jets usually spread faster than circular jets. Another technique being investigated to increase jet spreading even further for a given nozzle is the use of "tabs" to generate vortices. A typical tab is a triangular-shaped protrusion placed at the nozzle exit, with the base of the triangle touching the nozzle wall and the apex leaning downstream at 45 to the stream direction. This geometry was determined by a parametric study to produce the optimum effect for a given area blockage. The tabs can increase jet spreading significantly. The underlying mechanism traces to a pair of counter-rotating streamwise vortices originating from each tab. These vortex pairs persist in the flow; and with the appropriate number and strength, they can increase spreading.
    Schlagwort(e): Aircraft Propulsion and Power
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 4
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    Fuel-Cell-Powered Electric Motor Drive Analyzed for a Large Airplane (2005)
    In:  CASI
    Details
    Publikationsdatum: 2018-06-02
    Beschreibung: Because of its high efficiency, fuel cell technology may be used to launch a new generation of more-electric aeropropulsion and power systems for future aircraft. Electric-motor-driven airplanes using fuel-cell powerplants would be beneficial to the environment because of fuel savings, low noise, and zero carbon-dioxide emissions. In spite of the fuel cell s efficiency benefit, to produce the same shaft drive power, a fuel cell- powered electric-drive system must be definitely heavier than a turbine-drive system. However, the fuel-cell system s overall efficiency from fuel-to-shaft power is higher than for a turbine-drive system. This means that the fuel consumption rate could be lower than for a conventional system. For heavier, fuel-laden planes for longer flights, we might achieve substantial fuel savings. In the airplane industry, in fact, an efficiency gain of even a few percentage points can make a major economic difference in operating costs.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: Research and Technology 2004; NASA/TM-2005-213419
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 5
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    Liquid-Hydrogen-Cooled 450-hp Electric Motor Test Stand Being Developed (2005)
    In:  CASI
    Details
    Publikationsdatum: 2018-06-02
    Beschreibung: With growing concerns about global warming, there is a need to develop pollution-free aircraft. One approach is to use hydrogen-fueled aircraft that use fuel cells or turbogenerators to produce electric power to drive the electric motors that turn the aircraft s propulsive fans. Hydrogen fuel would be carried as a liquid, stored at its boiling point of 20.5 K (-422.5 F). Conventional electric motors, however, are too heavy for aircraft propulsion. We need to develop high-power, lightweight electric motors (highpower- density motors). One approach is to increase the conductivity of the wires by cooling them with liquid hydrogen (LH2). This would allow superconducting rotors with an ironless core. In addition, the motor could use very pure aluminum or copper, substances that have low resistances at cryogenic temperatures. A preliminary design of a 450-hp LH2-cooled electric motor was completed and is being manufactured by a contractor. This motor will be tested at the NASA Glenn Research Center and will be used to test different superconducting materials such as magnesium diboride (MgB2). The motor will be able to operate at speeds of up to 6000 rpm.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: Research and Technology 2004; NASA/TM-2005-213419
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 6
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    Discrete Event Supervisory Control Applied to Propulsion Systems (2005)
    In:  CASI
    Details
    Publikationsdatum: 2018-06-02
    Beschreibung: The theory of discrete event supervisory (DES) control was applied to the optimal control of a twin-engine aircraft propulsion system and demonstrated in a simulation. The supervisory control, which is implemented as a finite-state automaton, oversees the behavior of a system and manages it in such a way that it maximizes a performance criterion, similar to a traditional optimal control problem. DES controllers can be nested such that a high-level controller supervises multiple lower level controllers. This structure can be expanded to control huge, complex systems, providing optimal performance and increasing autonomy with each additional level. The DES control strategy for propulsion systems was validated using a distributed testbed consisting of multiple computers--each representing a module of the overall propulsion system--to simulate real-time hardware-in-the-loop testing. In the first experiment, DES control was applied to the operation of a nonlinear simulation of a turbofan engine (running in closed loop using its own feedback controller) to minimize engine structural damage caused by a combination of thermal and structural loads. This enables increased on-wing time for the engine through better management of the engine-component life usage. Thus, the engine-level DES acts as a life-extending controller through its interaction with and manipulation of the engine s operation.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: Research and Technology 2004; NASA/TM-2005-213419
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 7
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    Intelligent Life-Extending Controls for Aircraft Engines Studied (2005)
    In:  CASI
    Details
    Publikationsdatum: 2018-06-02
    Beschreibung: Current aircraft engine controllers are designed and operated to provide desired performance and stability margins. Except for the hard limits for extreme conditions, engine controllers do not usually take engine component life into consideration during the controller design and operation. The end result is that aircraft pilots regularly operate engines under unnecessarily harsh conditions to strive for optimum performance. The NASA Glenn Research Center and its industrial and academic partners have been working together toward an intelligent control concept that will include engine life as part of the controller design criteria. This research includes the study of the relationship between control action and engine component life as well as the design of an intelligent control algorithm to provide proper tradeoffs between performance and engine life. This approach is expected to maintain operating safety while minimizing overall operating costs. In this study, the thermomechanical fatigue (TMF) of a critical component was selected to demonstrate how an intelligent engine control algorithm can significantly extend engine life with only a very small sacrifice in performance. An intelligent engine control scheme based on modifying the high-pressure spool speed (NH) was proposed to reduce TMF damage from ground idle to takeoff. The NH acceleration schedule was optimized to minimize the TMF damage for a given rise-time constraint, which represents the performance requirement. The intelligent engine control scheme was used to simulate a commercial short-haul aircraft engine.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: Research and Technology 2004; NASA/TM-2005-213419
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 8
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    Low-Speed Active Flow Control Laboratory Developed (2005)
    In:  CASI
    Details
    Publikationsdatum: 2018-06-02
    Beschreibung: The future of aviation propulsion systems is increasingly focused on the application of control technologies to significantly enhance the performance of a new generation of air vehicles. Active flow control refers to a set of technologies that manipulate the flow of air and combustion gases deep within the confines of an engine to dynamically alter its performance during flight. By employing active flow control, designers can create engines that are significantly lighter, are more fuel efficient, and produce lower emissions. In addition, the operating range of an engine can be extended, yielding safer transportation systems. The realization of these future propulsion systems requires the collaborative development of many base technologies to achieve intelligent, embedded control at the engine locations where it will be most effective. NASA Glenn Research Center s Controls and Dynamics Technology Branch has developed a state-of-the-art low-speed Active Flow Control Laboratory in which emerging technologies can be integrated and explored in a flexible, low-cost environment. The facility allows the most promising developments to be prescreened and optimized before being tested on higher fidelity platforms, thereby reducing the cost of experimentation and improving research effectiveness.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: Research and Technology 2004; NASA/TM-2005-213419
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 9
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    Model-Based, Multiscale Self-Tuning Controller Developed for Active Combustion Control (2005)
    In:  CASI
    Details
    Publikationsdatum: 2018-06-02
    Beschreibung: New challenges concerning system health-monitoring and life-extending robust controls for the Ultra-Efficient Engine Technology Project, as well as other advanced engine and power system concepts at NASA and elsewhere, have renewed the control community s interest in smart, model-based methods. In particular, these challenges have further motivated efforts at the NASA Glenn Research Center to exploit the versatility and superiority of the dynamic features extraction of multiscale analysis for controls--such as with "wavelets" and "wavelet filter-banks.' The accomplishments reported herein pertain to the active suppression of combustion instabilities in liquid-fuel combustors via fuel modulation. The fundamentals and initial success of this innovation were reported for a unique demonstration of active combustion control (a research collaboration of NASA Glenn with Pratt & Whitney and the United Technologies Research Center, UTRC). This demonstration, conducted in 2002 at UTRC on the NASA single nozzle rig (SNR) combustor, was the first known suppression of high-frequency instability with a liquid-fueled combustor. The SNR is based on a high-powered military engine combustor that exhibited well-known instabilities.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: Research and Technology 2004; NASA/TM-2005-213419
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 10
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    Adaptive Technologies Developed and Demonstrated for Extending the Stable Operating Range of Compressors (2005)
    In:  CASI
    Details
    Publikationsdatum: 2018-06-02
    Beschreibung: The operational envelope of gas turbine engines is constrained by the stability limit of the compression system. The dangers of exceeding this limit are severe, with the potential for engine failure and loss of the aircraft. To avoid such failures, compressor designers provide an adequate stability (stall) margin in the compressor design to account for inlet distortions, degradation due to wear, throttle transients, and other factors that reduce compressor stability from the original design intent. In some cases, the required stall margin results in the compressor operating line being below the maximum efficiency potential of the compression system. Current approaches to increasing stability tend to decrease the efficiency of the compressor. The focus of this work is to increase the stall margin of compressors without decreasing their efficiency.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: Research and Technology 2004; NASA/TM-2005-213419
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
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