GE-F101 Afterburner

When I was first introduced to CAD modeling in 2004 I enjoyed having the ability to draw anything in 3D. One of the most complex projects I undertook was to model the afterburner of the General Electric F101 engine, the engine used on the Rockwell B-1B Lancer bomber. The afterburner functions to dramatically increase the thrust of a jet engine by pumping additional fuel into the exhaust. The adjustable nozzle allows the engine to control the exit velocity of the jet. At non-afterburning throttle settings, the engine nozzle shrinks to increase the velocity of the jet. However, when afterburning, the pressure inside the afterburner increases sufficiently to drive the flow through the narrowest portion of the nozzle (called the throat) to supersonic speeds. Such a supersonic flow behaves opposite to subsonic flow in that supersonic flow will accelerate as the cross-sectional area increases. This is why in order to maintain maximum thrust, the nozzle has to be capable of changing from a contracting diameter to an expanding diameter as a function of throttle settings.

And here is the SolidWorks CAD model of GE-F101 engine's afterburner. Since no drawings were available, all dimensions were extrapolated based on a rough estimate of engine diameter and nozzle length. Many detailed pictures served as a guide. After modeling the mechanism, much of the functionality of each component became evident.

Here is an animation showing the mechanism of the nozzle design and the model's functionality. As the pistons retract, rollers in the ring force the cammed surfaces toward the center of the engine, constricting the nozzle's "throat" (narrowest portion of the nozzle). The long tie rods serve as the 4th link of the four-bar linkage that controls the expansion ratio of the nozzle in afterburning mode. Click on the "3D PDF" Link below to view the model in 3D (must have Adobe Reader or Acrobat installed).