John Magill

Exploring the Feasibility of Pulsed Jet Separation Control for Aircraft Configurations

This paper describes experiments aimed at demonstrating the effectiveness of pulsed vortex generator jets (PVGJs) in controlling separation on aircraft wings. The demonstration is accomplished by applying the jets to two relevant cone gurations and evaluating their effectiveness in a wind tunnel. The jet design and placement for both experiments was based on parametric studies described in a previous paper. In the e rst application, pulsed jets prevented separation over the wings on a three-dimensional lambda-wing e ghter cone guration at low speeds and high angles of attack. This experiment shows that the e ow control method can enhance the lift, and hence the maneuverability, of advanced e ghters in post-stall e ight. The lambda-wing experiments also demonstrated that jets can be operated asymmetrically for lateral maneuvering control at high angles of attack. The second set of experimentstestedhigherspeed ranges, applying jets to an airfoilsection in an M =0.3‐0.5 e ow.Thiscone guration is relevant to subsonic cruise. The results show that PVGJs can increase lift and lift-to-drag ratios, but they were less effectiveat supercriticalspeedswhereseparation isinduced by hingelineshocks. In all cases, thejetsincreased lift over their effective range although their drag effect was small.

Combustion Dynamics and Control in Liquid-Fueled Direct Injection Systems

Abstract : Experiments evaluating the performance of a closed-loop combustion stabilization algorithm show that the method can reduce the magnitude of pressure oscillations in a liquid-fueled combustor by more than 50%. This paper describes the gas-turbine type combustor facility used for the experiments, associated instrumentation, unsteady combustion experiments, and the control scheme employed to suppress the natural thermo-acoustic instability. The combustor exhibits a natural instability at 140 Hz, the result of dynamic coupling between the combustor pressure field and the combustion heat release. Experiments to characterize the influence of operating parameters on the behavior of the instability are described. The control algorithm, amplitude-based pulse-width modulation, is used to modulate flow through one stream of a dual-passage fuel injector at such a phase that the instability amplitude is reduced. The paper concludes with a discussion of the control experiments, showing that the algorithm was successful in reducing the pressure oscillation.

Experimental evaluation of an adaptive controller for a wind-driven pitch manipulator

The problem of control design for wind-driven manipulators is addressed, and results of an experimental controller evaluation are described. Successful control design is essential to the use of the wind-driven manipulator for simulating aircraft maneuvers in a wind tunnel. Several wind-driven manipulator configurations are described. A second-order nonlinear state model for a pitch only manipulator is derived and validated with experimental data. An adaptive feedback linearization algorithm for the pitch manipulator is described. Experimental results are presented to show actual controller performance.