Active Stall Control in High Speed Compressors

Objective

The objective of the Active Stall Control program is to develop and demonstrate active control of rotating stall and surge in a high speed compressor stage. The effort is a joint NASA-MIT cooperative program and has been successful at reducing stalling mass flow by 11% performed at relative tip mach numbers of 1.0 and 1.5

The peak efficiency operating point of a turbine engine compressor is very near the compressor stall line as shown in the above figure. In order to prevent catastrophic stall from occurring during large transients, the engine is operated with a large safety margin. If the compressor can be safely operated closer to the designed compressor peak efficiency then it will result in increased engine efficiency and reduced engine cost leading to significant savings in aircraft fuel costs.

Approach

The compressor stall line can be moved up through active control thus allowing safe operation at peak efficiencies. The active stall control is obtained by sensing pressure changes at the inlet face of the compressor which will indicate flow distortion that is the precursor to stall, and activating high bandwidth flow valves located around the circumference of the compressor that blow high pressure air to counter the flow distortion before it builds up to stall. The challenges for implementation of active stall control are developing accurate models of the stall phenomenon that can be used for control design, developing high bandwidth (of the order of 500Hz) actuators for controlling flow valves and understanding the effectiveness of different actuating schemes for stall control.

High Frequency Injector

Benefits

• Improved performance near stall line
• Refined fluid theory and fluid models
• New system identification tools
• Better actuator effectiveness

Current Work in Active Stall Control

The active stall control program at NASA GRC is a cooperative program with industry and academia with strong participation from MIT (Massachusetts Institute of Technology). Active stall control has been demonstrated in the laboratory environment at NASA GRC for a single stage high speed compressor and experimental investigations are currently being conducted to demonstrate the technology on a multiple stage compressor in the presence of inlet distortion. NASA is working with industry partners to demonstrate the active stall control technology on a full scale engine test.

• MIT cooperative agreement towards active stall control in a single stage compressor with inlet distortion
• SBIR for identification of stall precursive modes in multistage compressors with inlet distortion
• NASA effort to identify stall precursors using a single sensor nonlinear technique
• 3D modeling effort to include actuation in a single stage compressor
• Forced response studies to indicate the role of high speed injection upon single stage and multistage machines
• Support of T-55 rig and engine forced response testing
• Support of ADP Fan I & II stall precursor studies

Accomplishments

• 3-D linearized, incompressible model developed
• 2-D linearized, compressible model developed
• 600 hertz actuators designed
• New casing for 35 fully instrumented
• Infinite line probes tested and installed
• Stall identification algorithm can sense stall precursive events 1000 rotor revolutions prior to stall
• Control and data acquisition logic in place

Participants

• NASA Glenn Research Center
• U.S. Army
• Massachusetts Institute of Technology
• Textron-Lycoming
• Pratt & Whitney
• UTRC

Personnel

• Project Contact:
  Sanjay Garg
  NASA Glenn Research Center
  21000 Brookpark Road, M.S. 77-1
  Cleveland, Ohio 44135
  Phone: (216) 433-2685
  email: sanjay.garg-1@nasa.gov
  

responsible official: sanjay garg
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last updated: 2.29.08