Patent Application
20090159754
The present application relates to a rotary-wing system with increased efficiency through manipulation of a boundary layer.
A propeller system is limited in effectiveness and power density by the maximum speed achievable at the blade tip without separation and the associated drag and vortex generation. Since the speed of the remainder of the propeller is limited by the tip speed, the overall efficiency of the propeller is thereby limited. Likewise, as the propeller forward speed changes relative to the surrounding fluid, the effective velocity and vector at the tip changes which further limits the rotational speed achievable without separation.
A rotary-wing system according to an exemplary aspect of the present invention includes: a rotary-wing rotatable about an axis of rotation; at least one emitter mounted to the rotary wing; and at least one attractor mounted to the rotary wing adjacent to the at least one emitter to generate a directed ion field therebetween to control at least one boundary layer characteristic.
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently disclosed embodiment. The drawings that accompany the detailed description can be briefly described as follows:
The propeller system 10 includes an ion flow control system 16. The system 16 includes a set of at least one emitter 18 and at least one attractor 20 on each rotary-wing 14. Each of the emitters 18 and the attractors 20 in the illustrated non-limiting embodiment may be powered from a power source P capable of producing, for example only, pulsed DC power, constant DC power or an alternative power source. It should be understood that the duty cycle of a pulsed DC power source can be optimized for maximum efficiency.
Referring to
In one non-limiting embodiment, the emitters 18B, 18C and respective attractors 20B, 20C may be located in a mid-span region and trailing edge region. Still further, at least one additional emitter 18D, 18E and attractor 20D, 20E sets may be positioned along a lower surface 14M of the rotary-wing 14. It should be understood that other emitter/attractor network arrangements may alternatively or additionally be provided. It should further be understood that any number of sets may be mounted to each rotary-wing 14 so as to generate a desired boundary layer modification.
Each of the emitters 18 and each of the attractors 20 may be manufactured of an electrically conductive material such as, for example only, carbon fiber material or nanotubes. Each emitter 18 operates as an ion source and each attractor 20 operates as an ion collector such that the emitter/attractor network may be utilized to create a directed ion field (
A concentrated field around each emitter 18 ionizes the adjacent atmosphere which is accelerated towards the less concentrated attractor 20 mounted further aft on the rotary-wing 14 (
Through variation in boundary layer control (including reduced or reversed flow) across various portions of the rotary-wing 14, various additional effects such as steering, braking, increased lift, and stability may alternatively and additionally be accomplished in addition to drag reduction. As generally understood, the definition of a boundary layer as utilized herein is a thin layer of fluid immediately next to a solid body that flows more slowly than the rest of the fluid. It should be understood that although boundary layer is described herein as being controlled, since the fluid adjacent the solid body such as the rotary-wing is accelerated faster than the rest of the fluid, that area may understood as not actually being part of the boundary layer as generally understood. In other words, the present invention does reduce the boundary layer and also affects the fluid beyond the boundary layer.
Referring to
After the directed ion flow is generated within the fluid, the boundary layer velocity loss characteristics are altered as schematically illustrated in a second shaded region F2. The second shaded region F2 illustrates the reduction in velocity loss of the fluid in the boundary layer after the influence of the directed ion field. In the illustrated example of
Reduction of the boundary layer has the effect of reducing the parasitic drag and inhibiting boundary layer separation. Boundary layer separation occurs primarily at a tip of the rotary-wing to create an air gap between the boundary layer and the upper surface 14U of the rotary-wing 14, i.e., a wake vortex can be created which results in a decrease in performance characteristics of the rotary-wing 14 whether driven or driving. That is, operation of the system 16 reduces the boundary layer thickness or build up as well as inhibit flow separation to increase the efficiency thereof.
Referring to
The NO control boundary layer characteristic illustrates the thickness of the boundary layer without the application of any control (such as F1 in
Referring to
When constructing a rotary-wing 14 it is typically necessary to account for non-optimal airflow conditions by, for example, varying forward speed, tip speed, and pitch. Implementing boundary layer control on the surface of the rotary-wing 14 such as described herein minimizes the impact of adverse conditions and allows for the rotary-wing 14 to be operated at a higher efficiency than is possible without boundary layer control.
Referring to
It should be understood that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are with reference to the normal operational attitude of the vehicle and should not be considered otherwise limiting.
It should be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit from the instant invention.
Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present invention.
The foregoing description is exemplary rather than defined by the limitations within. Many modifications and variations of the present invention are possible in light of the above teachings. The disclosed embodiments of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.
