Evaluation of an Active Clearance Control System Concept

TITLE AND SUBTITLE:
Evaluation of an Active Clearance Control System Concept

AUTHOR(S):
Bruce M. Steinetz, Scott B. Lattime, Shawn Taylor, Jonathan A. DeCastro, Jay Oswald, and Kevin J. Melcher

REPORT DATE:
November 2005

FUNDING NUMBERS:
WBS-22-714-92-56

PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES):
National Aeronautics and Space Administration
John H. Glenn Research Center at Lewis Field
Cleveland, Ohio 44135-3191

PERFORMING ORGANIZATION REPORT NUMBER:
E-15226

SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES):
National Aeronautics and Space Administration
Washington, DC 20546-0001

REPORT TYPE AND DATES COVERED:
Technical Memorandum

SPONSORING/MONITORING AGENCY REPORT NUMBER:
NASA TM-2005-213856
AIAA-2005-3989

SUPPLEMENTARY NOTES:
Prepared for the 41st Joint Propulsion Conference and Exhibit cosponsored by the AIAA, ASME, SAE, and ASEE, Tucson, Arizona, July 10-13, 2005. Bruce M. Steinetz and Kevin J. Melcher, NASA Glenn Research Center; Scott B. Lattime, The Timken Company, 1835 Dueber Ave. SW, Canton, Ohio 44706; Shawn Taylor, University of Toledo, 2801 W. Bancroft Street, Toledo, Ohio 43606; Jonathan A. DeCastro, QSS Group, Inc., 21000 Brookpark Road, Cleveland, Ohio 44135; and Jay Oswald, J&J Technical Solutions, 14880 Timber Lane, Cleveland, Ohio 44130. Responsible person, Bruce M. Steinetz, organization code RSM, 216-433-3302.

ABSTRACT:
Reducing blade tip clearances through active tip clearance control in the high pressure turbine can lead to significant reductions in emissions and specific fuel consumption as well as dramatic improvements in operating efficiency and increased service life. Current engines employ scheduled cooling of the outer case flanges to reduce high pressure turbine tip clearances during cruise conditions. These systems have relatively slow response and do not use clearance measurement, thereby forcing cold build clearances to set the minimum clearances at extreme operating conditions (e.g., takeoff, reburst) and not allowing cruise clearances to be minimized due to the possibility of throttle transients (e.g., step change in altitude). In an effort to improve upon current thermal methods, a first generation mechanically-actuated active clearance control (ACC) system has been designed and fabricated. The system utilizes independent actuators, a segmented shroud structure, and clearance measurement feedback to provide fast and precise active clearance control throughout engine operation. Ambient temperature performance tests of this first generation ACC system assessed individual seal component leakage rates and both static and dynamic overall system leakage rates. The ability of the nine electric stepper motors to control the position of the seal carriers in both open- and closed-loop control modes for single and multiple cycles was investigated. The ability of the system to follow simulated engine clearance transients in closed-loop mode showed the system was able to track clearances to within a tight tolerance (≤ 0.001 in. error).

SUBJECT TERMS:
Seal; Active clearance control; Design; Leakage; Flow; Actuator; Clearance sensor; Turbine; High pressure turbine

NUMBER OF PAGES:
20

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