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  • 21
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    A Survey of Current Rotorcraft Propulsion Health Monitoring Technologies (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A brief review is presented on the state-of-the-art in rotorcraft engine health monitoring technologies including summaries on current practices in the area of sensors, data acquisition, monitoring and analysis. Also, presented are guidelines for verification and validation of Health Usage Monitoring System (HUMS) and specifically for maintenance credits to extend part life. Finally, a number of new efforts in HUMS are summarized as well as lessons learned and future challenges. In particular, gaps are identified to supporting maintenance credits to extend rotorcraft engine part life. A number of data sources were consulted and include results from a survey from the HUMS community, Society of Automotive Engineers (SAE) documents, American Helicopter Society (AHS) papers, as well as references from Defence Science & Technology Organization (DSTO), Civil Aviation Authority (CAA), and Federal Aviation Administration (FAA).
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2012-217420 , E-18092
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 22
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    Baseline Experimental Results on the Effect of Oil Temperature on Shrouded Meshed Spur Gear Windage Power Loss (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Rotorcraft gearbox efficiencies are reduced at increased surface speeds due to viscous and impingement drag on the gear teeth. This windage power loss can affect overall mission range, payload, and frequency of transmission maintenance. Experimental and analytical studies on shrouding for single gears have shown it to be potentially effective in mitigating windage power loss. Efficiency studies on unshrouded meshed gears have shown the effect of speed, oil viscosity, temperature, load, lubrication scheme, etc. on gear windage power loss. The open literature does not contain experimental test data on shrouded meshed spur gears. Gear windage power loss test results are presented on shrouded meshed spur gears at elevated oil inlet temperatures and constant oil pressure both with and without shrouding. Shroud effectiveness is compared at four oil inlet temperatures. The results are compared to the available literature and follow-up work is outlined.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN45010 , ASME 2017 IDETC/CIE; Aug 06, 2017 - Aug 09, 2017; Cleveland, OH; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 23
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    Swept Volume Approach for the Characterization of Pumping Loss of Shrouded Meshed Cylindrical Gears (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: High speed rotorcraft transmissions are subject to load-independent power losses consisting of drag and pumping loss. Tightly conforming shrouds enclosing the transmission gears are often incorporated to reduce the drag component of the total load-independent losses. However, tightly conforming axial shrouding can result in an increase in the pumping loss component. Quantifying the pumping loss of shrouded gear transmissions has been the subject of many studies. This study presents a new approach for estimating pumping loss based on the concept of swept volume borrowed from the positive displacement pump and compressor industry. In this study, pumping loss of shrouded gear transmissions is considered to be related to the swept volume of the gear sets and the downstream flow resistance created by the shroud clearances. The drag loss and pumping loss of a spur gear pair have been determined through testing using the NASA Glenn Research Center Gear Windage Test Facility. The results from this testing have been compared to theoretical results using the formulations presented in this study. Good correlation exist between the test pumping power loss and the predicted pumping power loss for tightly conforming axial shroud configurations.
    Keywords: Aeronautics (General)
    Type: GRC-E-DAA-TN67693 , Annual Forum and Technology Display; May 13, 2019 - May 16, 2019; Philadelphia, PA; United States
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    NASA TECHNICAL REPORTS
  • 24
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    Experimental Investigation of Shrouding on Meshed Spur Gear Windage Power Loss (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-27
    Description: Windage power loss in high-speed gearboxes results in efficiency losses and increased heating due to drag on the gear teeth. Test results for meshed spur gear windage power loss are presented at ambient oil inlet temperatures, both with and without shrouding. The rate of windage power loss is observed to increase above a gear surface speed of 10,000 feet per minute (51 meters per second), similar to results presented in the literature. Shrouding is observed to become more effective above 15,000 feet per minute (76 meters per second), decreasing power loss by 10 percent at 25,000 feet per minute (127 meters per second). The need for gearbox oil drain slots limits the effectiveness of shrouding in reducing windage power loss. Windage power loss is observed to decrease with increasing gearbox temperatures and to increase with oil flow. Windage power losses for unshrouded meshed spur gears are 7 times greater than losses determined from unshrouded single spur gear tests. A 6- to 12-times increase in windage power loss is observed in the shrouded meshed spur gear data compared with shrouded single spur gear data. Based on this preliminary study, additional research is suggested to determine the effect of oil drain slot configurations, axial and radial shroud clearances, and higher gear surface speeds on windage power loss. Additional work is also suggested to determine the sensitivity of windage power loss to oil temperature and oil flow. Windage power loss for meshed spur gears tested in both the shrouded and unshrouded configurations is shown to be more than double versus windage power loss for the same spur gears run individually in the same shroud configurations. Further study of the physical processes behind these results is needed to optimize gearbox shrouds for minimum windage power loss.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2017-219536 , E-19395 , GRC-E-DAA-TN44777 , American Helicopter Society (AHS) Annual Forum and Technology Display (Forum 73); 9ý11 May 2017; Fort Worth, TX; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 25
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    Fatigue Crack Growth Behavior Evaluation of Grainex Mar-M 247 for NASA's High Temperature, High Speed Turbine Seal Test Rig (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: The fatigue crack growth behavior of Grainex Mar-M 247 is evaluated for NASA s Turbine Seal Test Facility. The facility is used to test air-to-air seals primarily for use in advanced jet engine applications. Because of extreme seal test conditions of temperature, pressure, and surface speeds, surface cracks may develop over time in the disk bolt holes. An inspection interval is developed to preclude catastrophic disk failure by using experimental fatigue crack growth data. By combining current fatigue crack growth results with previous fatigue strain-life experimental work, an inspection interval is determined for the test disk. The fatigue crack growth life of the NASA disk bolt holes is found to be 367 cycles at a crack depth of 0.501 mm using a factor of 2 on life at maximum operating conditions. Combining this result with previous fatigue strain-life experimental work gives a total fatigue life of 1032 cycles at a crack depth of 0.501 mm. Eddy-current inspections are suggested starting at 665 cycles since eddy current detection thresholds are currently at 0.381 mm. Inspection intervals are recommended every 50 cycles when operated at maximum operating conditions.
    Keywords: Mechanical Engineering
    Type: NASA/TM-2008-215287 , E-16529-1
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 26
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    Turbine Seal Research at NASA GRC (2011)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: Low-leakage, long-life turbomachinery seals are important to both Space and Aeronautics Missions. (1) Increased payload capability (2) Decreased specific fuel consumption and emissions (3) Decreased direct operating costs. NASA GRC has a history of significant accomplishments and collaboration with industry and academia in seals research. NASA's unique, state-of-the-art High Temperature, High Speed Turbine Seal Test Facility is an asset to the U.S. Engine / Seal Community. Current focus is on developing experimentally validated compliant, non-contacting, high temperature seal designs, analysis, and design methodologies to enable commercialization.
    Keywords: Mechanical Engineering
    Type: E-663258 , NASA Seal/Secondary Air System Workshop; Nov 29, 2011; Cleveland, OH; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 27
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    Integrating Condition Indicators and Usage Parameters for Improved Spiral Bevel Gear Health Monitoring (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The objective of this study was to illustrate the importance of combining Health Usage Monitoring Systems (HUMS) data with usage monitoring system data when detecting rotorcraft transmission health. Three gear sets were tested in the NASA Glenn Spiral Bevel Gear Fatigue Rig. Damage was initiated and progressed on the gear and pinion teeth. Damage progression was measured by debris generation and documented with inspection photos at varying torque values. A contact fatigue analysis was applied to the gear design indicating the effect temperature, load and reliability had on gear life. Results of this study illustrated the benefits of combining HUMS data and actual usage data to indicate progression of damage for spiral bevel gears.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2013-217896 , E-18665-1 , AHS International Annual Forum and Technology Display; May 21, 2013 - May 23, 2013; Phoenix, AZ; United States
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  • 28
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    Erosive Wear Characterization of Materials for Lunar Construction (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: NASA s Apollo missions revealed that exhaust from the retrorockets of landing spacecraft may act to significantly accelerate lunar dust on the surface of the Moon. A recent study by Immer et al. (C. Immer, P.T. Metzger, P.E. Hintze, A. Nick, and R. Horan, Apollo 12 Lunar Module exhaust plume impingement on Lunar Surveyor III, Icarus, Vol. 211, pp. 1089-1102, 2011) investigated coupons returned to Earth from the Surveyor III lunar probe which were subjected to lunar dust impingement by the Apollo 12 Lunar Module landing. Their study revealed that even with indirect impingement, the spacecraft sustained erosive damage from the fast-moving lunar dust particles. In this work, results are presented from a series of erosive wear experiments performed on 6061 Aluminum using the JSC-1AF lunar dust simulant. Optical profilometry was used to investigate the surface after the erosion process. It was found that even short durations of lunar dust simulant impacting at low velocities produced substantial changes in the surface.
    Keywords: Astronautics (General)
    Type: NASA/TM-2012-217706 , E-18343 , 1243291 , STLE 67th Annual Meeting and Exhibition 2012; May 06, 2012 - May 10, 2012; St. Louis, MO; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 29
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    Leakage and Power Loss Test Results for Competing Turbine Engine Seals (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Advanced brush and finger seal technologies offer reduced leakage rates over conventional labyrinth seals used in gas turbine engines. To address engine manufacturers concerns about the heat generation and power loss from these contacting seals, brush, finger, and labyrinth seals were tested in the NASA High Speed, High Temperature Turbine Seal Test Rig. Leakage and power loss test results are compared for these competing seals for operating conditions up to 922 K (1200 F) inlet air temperature, 517 KPa (75 psid) across the seal, and surface velocities up to 366 m/s (1200 ft/s).
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2004-213049 , GT2004-53935 , E-14452 , Turbo Expo 2004; Jun 14, 2004 - Jun 17, 2004; Vienna; Austria
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 30
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    Strain-Life Assessment of Grainex Mar-M 247 for NASA's Turbine Seal Test Facility (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: NASA s Turbine Seal Test Facility is used to test air-to-air seals for use primarily in advanced jet engine applications. Combinations of high temperature, high speed, and high pressure limit the disk life, due to the concern of crack initiation in the bolt holes of the Grainex Mar-M 247 disk. The primary purpose of this current work is to determine an inspection interval to ensure safe operation. The current work presents high temperature fatigue strain-life data for test specimens cut from an actual Grainex Mar-M 247 disk. Several different strain-life models were compared to the experimental data including the Manson-Hirschberg Method of Universal Slopes, the Halford-Nachtigall Mean Stress Method, and the Modified Morrow Method. The Halford-Nachtigall Method resulted in only an 18 percent difference between predicted and experimental results. Using the experimental data at a 99.95 percent prediction level and the presence of 6 bolt holes it was found that the disk should be inspected after 665 cycles based on a total strain of 0.5 percent at 649 C.
    Keywords: Mechanical Engineering
    Type: NASA/TM-2004-212985 , ARL-TR-3178 , GT2004-53939 , E-14460 , Turbo Expo 2004; Jun 14, 2004 - Jun 17, 2004; Vienna; Austria
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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