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Labyrinth Seal Flutter Analysis and Test Validation in Support of Robust Rocket Engine DesignHigh energy-density turbomachines, like the SSME turbopumps, utilize labyrinth seals, also referred to as knife-edge seals, to control leakage flow. The pressure drop for such seals is order of magnitude higher than comparable jet engine seals. This is aggravated by the requirement of tight clearances resulting in possible unfavorable fluid-structure interaction of the seal system (seal flutter). To demonstrate these characteristics, a benchmark case of a High Pressure Oxygen Turbopump (HPOTP) outlet Labyrinth seal was studied in detail. First, an analytical assessment of the seal stability was conducted using a Pratt & Whitney legacy seal flutter code. Sensitivity parameters including pressure drop, rotor-to-stator running clearances and cavity volumes were examined and modeling strategies established. Second, a concurrent experimental investigation was undertaken to validate the stability of the seal at the equivalent operating conditions of the pump. Actual pump hardware was used to construct the test rig, also referred to as the (Flutter Rig). The flutter rig did not include rotational effects or temperature. However, the use of Hydrogen gas at high inlet pressure provided good representation of the critical parameters affecting flutter especially the speed of sound. The flutter code predictions showed consistent trends in good agreement with the experimental data. The rig test program produced a stability threshold empirical parameter that separated operation with and without flutter. This empirical parameter was used to establish the seal build clearances to avoid flutter while providing the required cooling flow metering. The calibrated flutter code along with the empirical flutter parameter was used to redesign the baseline seal resulting in a flutter-free robust configuration. Provisions for incorporation of mechanical damping devices were introduced in the redesigned seal to ensure added robustness
Document ID
20100022029
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
El-Aini, Yehia
(Pratt and Whitney Rocketdyne West Palm Beach, FL, United States)
Park, John
(Pratt and Whitney Rocketdyne West Palm Beach, FL, United States)
Frady, Greg
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Nesman, Tom
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Date Acquired
August 24, 2013
Publication Date
May 3, 2010
Subject Category
Spacecraft Propulsion And Power
Report/Patent Number
M10-0284
Meeting Information
Meeting: 57th JANNAF Joint Propulsion Meeting
Location: Colorado Springs, CO
Country: United States
Start Date: May 3, 2010
End Date: May 7, 2010
Sponsors: Department of the Air Force, Department of the Navy, NASA Headquarters, Department of the Army
Distribution Limits
Public
Copyright
Other

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