Aeronautics and astronautics – Aircraft sustentation – Sustaining airfoils
Reexamination Certificate
1998-09-23
2001-06-19
Eldred, J. Woodrow (Department: 3644)
Aeronautics and astronautics
Aircraft sustentation
Sustaining airfoils
C244S130000
Reexamination Certificate
active
06247671
ABSTRACT:
1. FIELD OF THE INVENTION
The present invention relates to a method and apparatus for reducing aerodynamic drag and the intensity of the shock waves produced by aerodynamic members for example the wings of aircraft.
It is also taught herein that such method and apparatus may be employed on the leading edges of devices and projectiles emanating from cannon and the like and the nose cone of rockets.
When an aircraft is moving through the air at a speed exceeding the speed of sound, sonic (or shock) waves build up at the leading edges of the wing and other aerodynamic surfaces of the aircraft producing a phenomenon known as “sonic boom”. This is objectionable not only because of resulting shock effects producing objectionable noise and doing physical damage to structures on the ground, but also because it results in an aerodynamic drag effect which retards the speed of the aircraft and requires more power to propel it through the air.
It is the object of the present invention to provide a method and apparatus for reducing shock waves and aerodynamic drag in an effective yet simple and economical manner.
A number of prior art thinkers have attempted to solve the problem of mitigating the effects of the shock wave at the leading edge in a fluid flow environment. For instance, in U.S. Pat. No. 3,162,398 to Clause et al the patentees employ a magnetohydrodynamic system for producing electrical currents within a moving air mass to control the position of a sonic wave relative to a flight vehicle.
It is well known that the total friction to movement of a body through a gas for a given Reynolds number depends largely upon the aerodynamic design of the particular body concerned. On an airfoil, for example, the optimum design is such as to delay the transition from laminar to turbulent air flow along the surface as much as possible as the speed of the airfoil increases. At moderate speeds, it has been possible to eliminate substantially all turbulent flow by proper design; at relatively higher speeds, however turbulent flow invariably results, with the attendant disadvantage of a sudden increase in the drag and decrease in the lift.
Much of the difficulty at high speeds is a direct result of frictional heating of the airfoil surfaces. This heating causes discontinuities in the layer of air immediately adjacent the hot airfoil surfaces, known as the boundary layer. These discontinuities in the boundary layer upset the normal path of the streamlines characterizing laminar flow. Thus, even with optimum present day aerodynamic designs, it has been difficult if not impossible to eliminate all turbulent flow and thereby reduce friction and attendant high heating at extremely high speeds.
Therefore, it is another object of the present invention to provide a novel method and apparatus for reducing the density of the air in the boundary layer whereby much higher Reynolds numbers may be realized without turbulent flow.
2. DESCRIPTION OF THE PRIOR ART
In patent U.S. Pat. No. 3,392,941 to Cason III, the patentee teaches the use of magnetohydrodynamic effects to achieve ionization of gases about a reentry nose cone thereby causing the ionization to provide an electromagnet to react with the ionized gases.
U.S. Pat. No. 3,360,220 to Meyer is also to a magnetohydrodynamic method and apparatus wherein a magnetic field is impressed upon an electrically conductive fluid medium to alter the flow pattern of the fluid.
In U.S. Pat. No. 3,446,464 to Donald, the patentee applies an electric field to the air in the vicinity of a leading edge air frame. For this purpose, electrodes are provided adjacent to the leading edge and a difference of potential is applied to the electrodes to establish an electric field between them.
U.S. Pat. No. 5,669,583 to Roth discloses a method and apparatus for covering an aircraft with a uniform glow discharge plasma which is said to affect the aerodynamic properties. It is stated that plasma is a partially ionized gas composed of ions, electrons and neutral species. It is produced by the action of either very high temperatures, or strong direct current or radio frequency electric fields.
U.S. Pat. No. 3,713,157 to August discloses the use of radiostotopes that produce ions that are injected into an air stream detailed to reduce a radar signature.
The prior art has not yet achieved the capability to provide acceptable drag reduction in a very efficient, practical and easily implemented fashion.
SUMMARY OF THE INVENTION
This invention is directed to an apparatus and method for modifying and controlling an air (or other gas) flow by selectively doping portions of the flow with ions. It is known that the performance of a high speed air or ground vehicle or engine is largely determined by the air flow around the vehicle and through its engine(s). This air flow is usually determined by the geometry of the vehicle, the shape and location of its control surfaces, the design of the flow path, engine, inlets, and nozzles. Depending on the desired speed and performance, a variety of different aerodynamic shapes, control surface designs, engine geometries, subsonic and supersonic flow paths, inlet and nozzle geometries, and thrust vectoring systems have been developed. These geometric techniques are, however, limited by the physical properties of the air such as its pressure, density, temperature, and velocity; and the size, mass and collision characteristics of its molecules. It would therefore be highly desirable to develop an apparatus and method to further enhance and control the air flow around the aircraft and through its engine(s) by modifying the physical properties of the air.
An apparatus according to this invention modifies the physical properties of the air by selectively doping the air flow ahead of an aerodynamic member with ions. The repulsive Coulomb forces between the ions in the doped region add to the normal kinetic forces between the air molecules in the doped region; facilitating and/or controlling the air flow, and modifying the sonic waves around the aircraft and its control surfaces, and through its flow path, engine(s), inlets, and nozzles.
For supersonic flows, doping the region between an aerodynamic member and the sonic wave produced by the supersonic flow ahead of the aerodynamic member with ions, reduces the intensity of the sonic wave. This reduces the pressure and density of the air in the region between the sonic wave and the aerodynamic member, which reduces the pressure against the front of the aerodynamic member and the density of the air in the boundary layer along the surface of the aerodynamic member, reducing both pressure and friction drag on the aerodynamic member.
For subsonic flows, doping the region ahead of an aerodynamic member reduces the density of the air in the boundary layer along the surface of the aerodynamic member, reducing the friction drag on the aerodynamic member.
In both cases drag reduction is achieved by modifying the properties of the air ahead of the aerodynamic member without employing electric or magnetic fields to change the velocity or direction of the air flow. As such, the energy required by our method and apparatus to reduce the drag on an aerodynamic member is minimized.
An apparatus to implement the drag reduction system is composed of an ion source and a mechanism for controlling the location of the ions ahead of the aerodynamic member. The mechanism for controlling the location of the ions ahead of the aerodynamic member may employ electric and/or magnetic fields to apply a force to the positively charged ions, and/or a gas flow to move the ions to the desired location.
Since ions are normally produced by removing one or more electrons from a neutral molecule, the ion source is normally composed of a plasma source which produces a gas of ions and electrons from neutral molecules, combined with a mechanism for extracting the ions from the electrons. The plasma source may take the form of an electric discharge (DC, RF, microwave, laser, etc.) which partially ionizes the air, producing ions and electron from the air mo
Carlton Lindley A
Kunhardt Erich E
Pap Robert M
Saeks Richard E
Accurate Automation Corporation
Eldred J. Woodrow
Schellin Eric P.
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