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Emergency Power Unit Control for F-2 Fighter


Case Study

South Bend Controls

Integrated System: ServoidŽ Proportional Flow Control with Delta-P Regulator

Application: Emergency Power Unit control of Air/Fuel Mixture

Platform: Japanese F-2 Attack Fighter Aircraft (F-16 Fighting Falcon variant)

 

The Application

This integrated system component is used in Emergency Power Units on the Japanese F-2 aircraft (a variant of the F-16 Eagle), to meter the air & fuel mixture. Since air density is limited at 35,000 feet, this system carries its own air supply which is metered along with the Jet Propellant fuel to the combustion chamber by the ServoidŽ valves. This system operates in very extreme environments (-65°F to +300°F ambient, -190°F to +160°F media, with high vibration). The demanding nature of this application requires mission critical reliability, ensuring that the products work every time. If the engine should flame out, the pilot uses the Emergency Power Unit that contains the SBC valves, and has 180 seconds to regain control and restart the engine.

The physical constraints of aerospace applications were also a factor, as envelope space and weight requirements were major concerns. The South Bend Controls solution thus involved an integrated system approach, in order to combine multiple components into one package. This approach has many benefits inherent to the customer?s design, ranging from manufacturing and maintenance to engineering and procurement.

The Solution

In order to mitigate risk and develop a robust integrated system solution, the South Bend Controls Engineering Team exercised analytical models and proven development tools in order to develop an integrated component that met all application requirements. In addition, SBC was required to demonstrate specification compliance on every unit, resulting in the development and deployment of a Test Cell capable of simulating the extreme temperature environments (-65°F and the 300°F).

The Proportional Air Control Valve is comprised of three primary components: the ServoidŽ Driver, a Proportional Metering Valve and the Delta-P Regulator. The function of each component is as follows:

  • The ServoidŽ Driver, is a current-driven, proportional DC solenoid which responds to either analog or digital (1 kHz pulse width modulated) signals. Input current (0 to 500 mA) is translated into a specific displacement with infinite resolution. The displacement is applied to a precision metering spool with resulting flow control. ServoidŽ drivers also include suspended-armature construction with no sliding elements. This provides low hysteresis and long component life.
  • The Proportional Metering Valve is a proprietary pressure-balanced configuration providing extremely high flow capacity in a single stage.
  • The Delta-P Regulator is a pressure-reducing differential pressure regulator that maintains a constant pressure differential across the metering orifice. This pressure differential insures a constant net flow even while supply and downstream pressures vary, as is common with turbine engines.

In order to meter both the air and fuel to the Emergency Power Unit, a corresponding Fuel Metering Control Valve was also developed, so that the flow and ratio of air & fuel to airborne turbine auxiliary power units. These systems include complex feedback to account for a wide range of startup parameters. Servoid valves also function well under open-loop conditions with high repeatability. This valve can be used anywhere highly repeatable flow control of gaseous media is a requirement and similar valves are also available for control of liquids such as fuels, coolant, and solvents.

The Specifications

PROPORTIONAL FLOW CONTROL VALVE WITH DELTA-P PRESSURE REGULATION

  • Valve Type: Proportional, Pressure Compensated Flow Control
  • Media: Air
  • Pressure
    • Operating: 1,020 to 1700 +/- 15 psig
    • Proof: 3,000 psig
    • Burst: 4,250 psig
  • Internal Regulation: 300 psi differential
  • Temperature
    • Ambient: -40°F to +300°F
    • Media: -190°F to +160°F
  • Maximum Flow: 180scfm (85slps) at 300psid (at approx. 1000psi backpressure)
  • Minimum Flow: ~7scfm @ 1550 psig Inlet, 200 psig Outlet
  • Electrical
    • Coil Current: 0 to 500 milliamps
    • Coil Resistance: 20.5 O @ 77°F +/- 3 Ohm
    • Insulation Resistance: 1x108 O minimum
  • External Leakage: None
  • Weight: 4.90lbm [2.67 kg]