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  • 1
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    Closed Loop Active Flow Separation Detection and Control in a Multistage Compressor (2005)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Active closed loop flow control was successfully demonstrated on a full annulus of stator vanes in a low speed axial compressor. Two independent methods of detecting separated flow conditions on the vane suction surface were developed. The first technique detects changes in static pressure along the vane suction surface, while the second method monitors variation in the potential field of the downstream rotor. Both methods may feasibly be used in future engines employing embedded flow control technology. In response to the detection of separated conditions, injection along the suction surface of each vane was used. Injected mass flow on the suction surface of stator vanes is known to reduce separation and the resulting limitation on static pressure rise due to lowered diffusion in the vane passage. A control algorithm was developed which provided a proportional response of the injected mass flow to the degree of separation, thereby minimizing the performance penalty on the compressor system.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2005-213553 , AIAA Paper 2005-0849 , E-14993 , 43rd Aerospace Sciences Meeting and Exhibit; Jan 10, 2005 - Jan 13, 2005; Reno, NV; United States
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  • 2
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    Experimental Investigation of Rotating Stall in a Research Multistage Axial Compressor (2007)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A collection of experimental data acquired in the NASA low-speed multistage axial compressor while operated in rotating stall is presented in this paper. The compressor was instrumented with high-response wall pressure modules and a static pressure disc probe for in-flow measurement, and a split-fiber probe for simultaneous measurements of velocity magnitude and flow direction. The data acquired to-date have indicated that a single fully developed stall cell rotates about the flow annulus at 50.6% of the rotor speed. The stall phenomenon is substantially periodic at a fixed frequency of 8.29 Hz. It was determined that the rotating stall cell extends throughout the entire compressor, primarily in the axial direction. Spanwise distributions of the instantaneous absolute flow angle, axial and tangential velocity components, and static pressure acquired behind the first rotor are presented in the form of contour plots to visualize different patterns in the outer (midspan to casing) and inner (hub to mid-span) flow annuli during rotating stall. In most of the cases observed, the rotating stall started with a single cell. On occasion, rotating stall started with two emerging stall cells. The root cause of the variable stall cell count is unknown, but is not attributed to operating procedures.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2007-214978 , ARL-TR-4126 , E-16134 , 18th ISABE Conference; Sep 02, 2007 - Sep 07, 2007; Beijing; China
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  • 3
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    Experimental Results of Performance Tests on a Four-Port Wave Rotor (2007)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A series of tests has been performed on a four-port wave rotor suitable for use as a topping stage on a gas turbine engine, to measure the overall pressure ratio obtainable as a function of temperature ratio, inlet mass flow, loop flow ratio, and rotor speed. The wave rotor employed an open high pressure loop that is the high pressure inlet flow was not the air exhausted from the high pressure outlet, but was obtained from a separate heated source, although the mass flow rates of the two flows were balanced. This permitted the choice of a range of loop-flow ratios (i.e., ratio of high pressure flow to low pressure flow), as well as the possibility of examining the effect of mass flow imbalance. Imbalance could occur as a result of leakage or deliberate bleeding for cooling air. Measurements of the pressure drop in the high pressure loop were also obtained. A pressure ratio of 1.17 was obtained at a temperature ratio of 2.0, with an inlet mass flow of 0.6 lb/s. Earlier tests had given a pressure ratio of less than 1.12. The improvement was due to improved sealing between the high pressure and low pressure loops, and a modification to the movable end-wall which is provided to allow for rotor expansion.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2007-214488 , E-15779 , ARL-TR-4044 , 45th Aerospace Sciences Meeting and Exhibit; Jan 08, 2007 - Jan 11, 2007; Reno, NV; United States
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  • 4
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    Hybrid Exhaust Component (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: An exhaust includes a wall that has a first composite material having a first coefficient of thermal expansion and a second composite material having a second coefficient of the thermal expansion that is less than the first coefficient of thermal expansion.
    Keywords: Aircraft Propulsion and Power
    Format: application/pdf
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