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This announcement is not a solicitation; it is for informational purposes only. This announcement does not constitute an Invitation for Bid, Request for Proposal, or Request for Quotation and is not to be construed as a commitment by the Government. The Government will not reimburse any costs associated with attending the Industry Day or providing any information associated with this announcement.

Description of the Supplies/Services

BACKGROUND:

The Department of Aeronautics, United States Air Force Academy, has a requirement to repair the Trisonic Wind Tunnel (TWT). The TWT is a blown-down tunnel capable of operating from Mach 0.3 to 4.5 with dynamic pressures as high as 35 psi in the test section.

The tunnel is over 60 years old with a control system from the 1980’s. The TWT is powered by air stored in large tanks pressurized to 600 psig. The primary parameters that must be controlled are 1) the pressure in the stilling chamber at the upstream end of the wind tunnel and 2) the position of the model support system in the wind tunnel test section.

The pressure control system was installed in 1988 and consists of a Moog chassis containing a series of signal conditioners, controllers and amplifiers, and an Allen-Bradley programmable logic controller (PLC). These devices control hydraulic valves that open or close the pressure control valves and move the model support mechanism. The PLC also serves as an interlock to prevent operation of the wind tunnel unless required conditions are satisfied.

The existing model positioning system (MPS) is part of the permanently installed equipment of the TWT. The MPS is used to pitch a model in the tunnel while the tunnel is running. The TWT is used for both classroom demonstrations and funded research projects. The existing MPS pitches to + 30.0/-20.0 degrees. A new system shall be designed to control the pitch and roll of the model in the test section while supporting the model on the sting balance to collect force and moment data.

The TWT was built in 1959 with the Aeronautics Laboratory. The control system was last upgraded in the 1980s by Fluidyne, which is now owned by Calspan ASE. The TWT supports approximately 1,000 cadets per year across multiple courses such as Aero 315, Aero 210, Aero 241, Aero 442, and Aero 471. The TWT is critical for cadet research involving approx. $300k of externally funded research per year for organizations such as the Air Force Research Laboratory, the Missile Defense Agency, and NASA. Since the TWT is capable of near-hypersonic speeds, it is becoming more heavily used given the increased emphasis on hypersonic weapons in the National Defense Strategy. The TWT is also an important capability supporting the Department of Aeronautics recurring accreditation by the Accreditation Board for Engineering & Technology (ABET). In order to be accredited as an aeronautical engineering degree-granting institution, USAFA needs to retain a robust experimental fluids discipline which includes experimental facilities for student courses. The TWT is consistently highlighted as one of the unique capabilities of the aeronautical engineering program by the ABET accreditors and losing this facility would endanger the accreditation of the aeronautical engineering program.

SALIENT CHARACTERISTICS/REQUIREMENT SPECIFICATIONS:

• The contractor shall design, build, and install a control system capable of performing at least these functions:

1. Control the stilling chamber pressure


2. Position the model in the test section to include pitch and roll.


3. Prevent operation of the wind tunnel unless all systems are operable and in the proper state


4. Shut down the wind tunnel in the event of emergency conditions such as electrical power failure, loss of hydraulic pressure, excessive stilling chamber pressure or operator pressing an emergency stop


5. Warn personnel and operators if personnel are in potentially hazardous locations. Provide physical barriers and interlocks as appropriate to prevent operation of the wind tunnel if safety of personnel is at risk.


6. Provide control of all wind tunnel functions/parameters manually and through a computer interface


7. Seamlessly integrating with legacy measurement equipment in a modular approach

• The tunnel control system shall provide tunnel parameters (at least stilling chamber pressure and model position) to any contractor-provided data acquisition system and readable by an operator-provided legacy data acquisition system. It is recommended that these parameters be provided both via message-based communication (e.g., Ethernet) and analog voltage output for reading by an external data acquisition system.


• The contractor shall thoroughly describe and document the feedback control loop required to maintain the pressure in the stilling chamber within operator-specified limits and control the rise time of the pressure. This must include control signals sent to the existing hydraulic valves that control the actuators opening the valves to the high-pressure system


• The contractor shall work with Aeronautics Laboratory personnel to consider all potential emergency scenarios (loss of power, loss of hydraulic pressure, etc) and build into the design of the control system features to immediately shut off the wind tunnel in an emergency after returning the model positioning system to a “home” position. The home position should be adjustable by the tunnel operator.


• The contractor shall design an interlock system to provide suitable warning to personnel that the tunnel is ready to run or that any systems are in a potentially hazardous state.


• The contractor shall thoroughly document the logic necessary to require all systems to be functional and in proper states before the valves in the high-pressure system can be opened.


• The contractor shall repair the Model Positioning System (MPS). The MPS is defined as the electronic hardware, software and mechanical linkages/parts required to control the vertical location and attitude of the model. The existing MPS is designed only to provide pitch motion. The replacement MPS shall provide, at a minimum, pitch, roll and vertical translation. Yaw motion is desirable but can generally be obtained through a combination of pitch and roll.


• The MPS shall be capable of setting the pitch and roll angles to within 0.1 degrees of the desired setpoint. The MPS shall retain the existing pitch limits and achieve at least +90/-90 degrees in roll.


• The MPS must be able to vary the center of rotation of the model between 6 and 17 inches upstream of the existing pod pivot pin.


• The MPS shall be able to plunge, meaning translate vertically in the test section while maintaining desired pitch and roll angles.


• Pitch, roll and plunge should be individually controllable. The control system and MPS should be able to execute commands to move to a specific pitch, roll and vertical position at a minimum of 10 deg/s in pitch, 30 deg/s in roll, with a vertical translation rate of at least 2 inches/s, simultaneously or in sequence as specified by the operator or computer interface.


• The MPS and any data acquisition shall operate in a move-pause or continuous sweep mode. When in move-pause mode, the MPS will provide a digital signal that the specified position has been reached and data acquisition can start for that position. When in continuous sweep mode, the position shall be reported at sufficient rate to record the motion of the model. The control system for the MPS shall allow operator-specified rates and maximum acceleration.


• The MPS shall not increase the blockage of the wind tunnel and the system must support a load of 2,000 pounds applied one foot in front of the pivot point.


• The existing MPS includes a “pod” mounted to a “blade”. The blade translates vertically, and mechanical linkages move the pod to angle of attack. Force balance wires and pressure tubing pass through the pod and down the inside of the blade to the bottom of the wind tunnel. The pod accepts a “sting” that either interfaces directly with the model or with a force balance that is internal to the model. The MPS must provide provision for similar instrumentation wiring and tubing and provision to accept existing and legacy sting and balance hardware. The MPS shall allow at least the same amount of tubing and wiring as the existing hardware.


• The MPS must be modular enough in design that modifications to the model mount are possible without redesign of the whole MPS.


• The contractor shall thoroughly describe and document the feedback control loop required to maintain the operator-specified pitch, roll and vertical position of the MPS. This must include control signals sent to the valves or actuators that control the MPS.


• The contractor shall provide a pressure rake which can measure the flow quality, including flow angularity, in the test section.


• The contractor shall repair the air leak in the storage tanks.


• The contractor shall assess and repair the diffuser section including the track, seals, flap settings, and gearing and counters.


• Priced separately as an option, the contractor shall modify the nozzle block exchange process to include a simpler and safer means of removing and replacing the tunnel side wall.


• Priced separately as an option, the contractor shall repair the transonic cart to include optical access.


• Priced separately as an option, the contractor shall provide a Mach 5 nozzle for the wind tunnel.


• On-site training shall be provided to train up to 3 personnel on the operation of the new control system.


• The contractor shall produce a document illustrating the required function of a control and interlock system for the wind tunnel. This must include:
  
  
  
  • Control of the stilling chamber pressure
  
  
  • Position of the model in the test section to include pitch, roll, yaw and vertical position.
  
  
  • Manual control of all operator-controllable features
  
  
  • An interlock to prevent operation of the wind tunnel unless all systems are operable and in the proper state
  
  
  • Systems to ensure shutdown of the wind tunnel in the event of power failure, loss of hydraulic pressure, emergency stop or excessive stilling chamber pressure
  
  
  • An interlock system to include physical barriers or warning systems to prevent operation of the tunnel if personnel are in potentially hazardous locations.
  
  
  
  


• The installation shall come with a 2-year warranty with on-site support to troubleshoot and correct any malfunctions.


• The contractor shall inspect and repair the Mach 2.5, 3.5 and 4.5 nozzle blocks (three pairs of blocks) to ensure they mate with the tunnel wall correctly with no distortion of the flow surface.

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