Inlet Flow Control Technology: Learning from History, Reinventing the Future

摘要

The history, not only of air intake development, but of inlet flow control technology in turbine-engine powered aircraft is written in museum hardware from the P-59 to the YF-22 (e.g., USAF Museum). Inlet lines in all historic and current transonic/supersonic aircraft systems testify to the necessary control of inlet-related boundary layer in reliable high speed flight. In this paper the evolution of inlet flow control design features is discussed and related to the need for reduced inlet drag, especially inlet bleed drag, in future aircraft. Inlet boundary layer control will still be required to achieve lower drag inlet designs, but recent R&D suggests that boundary layers in air intake adverse pressure gradients can be controlled in many cases by sub-boundary-layer vortex generators that do not involve having to oversize the inlet in order bleed off and dispose of the flow needed for control. Inlet development over the past 50 years or so has been as much an experimental adventure as a design science. It has required enormous amounts of large scale wind tunnel and even flight test refinement to close on systems designs that have reasonable performance at an acceptable cost. What the authors suggest is that significant, even substantial, savings in the time and cost for inlet and inlet flow control design/development can be realized if we make proper use of a combination of 3-D viscous CFD performance predictions together with carefully crafted small-scale experimental tests of inlet sub-components and relevant flow control (both bleed and micro-vg) physics demonstrations. The consequent improvement of analytical predictions is expected to reduce the need for validation experiments in large-to-full-scale wind tunnel environments. These advanced methodologies will dramatically reduce the need for large/full scale component/subsystem testing, using such tests sparingly for validation, as opposed to extended, expensive developmental testing.