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  • 2015-2019  (9)
  • 1
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    Gear Tooth Wear Detection Algorithm (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: Vibration-based condition indicators continue to be developed for Health Usage Monitoring of rotorcraft gearboxes. Testing performed at NASA Glenn Research Center have shown correlations between specific condition indicators and specific types of gear wear. To speed up the detection and analysis of gear teeth, an image detection program based on the Viola-Jones algorithm was trained to automatically detect spiral bevel gear wear pitting. The detector was tested using a training set of gear wear pictures and a blind set of gear wear pictures. The detector accuracy for the training set was 75 percent while the accuracy for the blind set was 15 percent. Further improvements on the accuracy of the detector are required but preliminary results have shown its ability to automatically detect gear tooth wear. The trained detector would be used to quickly evaluate a set of gear or pinion pictures for pits, spalls, or abrasive wear. The results could then be used to correlate with vibration or oil debris data. In general, the program could be retrained to detect features of interest from pictures of a component taken over a period of time.
    Keywords: Aeronautics (General)
    Type: NASA/TM-2015-218830 , E-19102
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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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
  • 3
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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
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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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
  • 5
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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 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 cite 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-TN39397 , 2017 ASME Power Transmission and Gearing (PTG) Conference; Aug 06, 2017 - Aug 09, 2017; Cleveland, OH; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Jetting Phenomenon in Meshed Spur Gears (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: Rotorcraft gearbox transmissions are required to efficiently transfer power from the turbine engine to the main and tail rotor blades. Losses in transmission efficiency impacts mission payload and aircraft range. These systems are expected to deliver high power with high gear pitch line velocities. More recently, shrouding has been employed to reduce windage power losses associated with the high gear rotational speeds. However, recent experimental results from tests conducted by the authors show the negative impact of close clearance shrouds on windage power loss, particularly at the meshed region where flow is ejected, or jetted, from the collapsing tooth spaces. A literature review was conducted to gain further insight into the phenomenon of gear mesh jetting and strategies to mitigate and control the associated losses. A discussion on observed trends follows with suggestions on future research.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN56977 , E-19538 , NASA/TM-2018- 219920
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Grainex Mar-M 247 Turbine Disk Life Study for NASA's High Temperature High Speed Turbine Seal Test Facility (2015)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: An experimental and analytical fatigue life study was performed on the Grainex Mar-M 247 disk used in NASA s Turbine Seal Test Facility. To preclude fatigue cracks from growing to critical size in the NASA disk bolt holes due to cyclic loading at severe test conditions, a retirement-for-cause methodology was adopted to detect and monitor cracks within the bolt holes using eddy-current inspection. For the NASA disk material that was tested, the fatigue strain-life to crack initiation at a total strain of 0.5 percent, a minimum to maximum strain ratio of 0, and a bolt hole temperature of 649 C was calculated to be 665 cycles using -99.95 percent prediction intervals. The fatigue crack propagation life was calculated to be 367 cycles after implementing a safety factor of 2 on life. Thus, the NASA disk bolt hole total life or retirement life was determined to be 1032 cycles at a crack depth of 0.501 mm. An initial NASA disk bolt hole inspection at 665 cycles is suggested with 50 cycle inspection intervals thereafter to monitor fatigue crack growth.
    Keywords: Metals and Metallic Materials
    Type: NASA/TM-2005-213873/REV1 , ARL-TR-3528 , E-15243 , GRC-E-DAA-TN19913
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    The Jetting Phenomena in Meshed Spur Gears (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Rotorcraft gearbox transmissions are required to efficiently transfer power from the turbine engine to the main and tail rotor blades. Losses in transmission efficiency impact mission payload and aircraft range. These systems are expected to deliver high power with high gear pitch line velocities. More recently, shrouding has been employed to reduce windage power losses associated with the high gear rotational speeds. However, recent experimental results from tests conducted by the authors show the negative impact of close clearance shrouds on windage power loss, particularly at the meshed region where flow is ejected, or jetted, from the collapsing tooth spaces. A literature review was conducted to gain further insight into the phenomenon of gear mesh jetting and strategies to mitigate and control the associated losses. An analysis was conducted on windage losses in the mesh region. Test results are given for a modified shroud configuration. Finally, a discussion on observed trends follows with suggestions on future research.
    Keywords: Aeronautics (General)
    Type: GRC-E-DAA-TN54362 , AHS International''s Annual Forum and Technology Display; May 15, 2018 - May 17, 2018; Phoenix, AZ; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
    facet.materialart.
    Unknown
    Experimental Investigation of Shrouding on Meshed Spur Gear Windage Power Loss (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Windage power loss in high-speed gearboxes result in efficiency losses and increased heating due to drag on the gear teeth. Meshed spur gear windage power loss test results are presented at ambient oil inlet temperatures both with and without shrouding. The rate of windage power loss is observed to increase above 10,000 ft.min., gear surface speed, similar to results presented in the literature. Shrouding is observed to become more effective above 15,000 ft.min., decreasing power loss by 10 at 25,000 ft.min. The need for gearbox oil drain slots limits the effectiveness of shrouding on reducing windage power loss. Also, windage power loss is observed to decrease with increasing gearbox temperatures and to increase with oil flow. Windage power losses for the unshrouded meshed spur gears are 7x more than losses determined from unshrouded single spur gear tests. A 6x to 12x increase in windage power is observed comparing shrouded single spur gear data with shrouded meshed 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 of meshed spur gears tested in both the shrouded and unshrouded configurations is shown to be more than double versus the same spur gears run individually in the same shroud configurations. Further study of the physical processes behind these results is needed for optimizing gearbox shrouds for minimum windage power loss.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN42435 , American Helicopter Society (AHS) International Annual Forum and Technology Display; May 09, 2017 - May 11, 2017; Fort Worth, TX; United States
    Format: application/pdf
    Location Call Number Expected Availability
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    NASA TECHNICAL REPORTS
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