Fluid reaction surfaces (i.e. – impellers) – Rotary skin friction type
Reexamination Certificate
1998-09-14
2002-04-23
Lopez, F. Daniel (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Rotary skin friction type
C416S155000, C415S004300, C415S908000
Reexamination Certificate
active
06375424
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates generally to systems for converting fluid-dynamic energy, such as from air and water, into mechanical energy. In particular, the invention relates to an open or closed field turbine in a wind tunnel, or hydrodynamic tunnel, for converting kinetic and potential energy into mechanical/electrical energy in an open eolian or hydrodynamic plant.
Furthermore, the invention relates to a closed system where the conversion of energy occurs in an environment where pressure is regulated and maintained above the atmospheric, level.
2. Background Art
Eolian and hydrodynamic energy offers many advantages. It is widespread all over the country and does not cause pollution. Compared with other kinds of alternative energies, such as solar or geothermal energy, it is easily available as mechanical energy and consequently can be converted into electric energy.
Unfortunately, present conventional wing-blade aerogenerators have a limited power coefficient and produce relatively unstable work with respect to time. Efficient use of wind energy is considerably limited by low energetic concentration with average annual values of power per surface unit stroked by the blade reduced to the minimum. Efficiency is also impacted by daily and annual irregularities and variables.
Eolian plants are over-dimensioned with respect to the power generated because of the aforementioned problems and also because of the low energetic density that is obtained from wind. Eolian plants also must have great mechanical strength to tolerate strong winds.
Wind energy is essentially the kinetic energy of the mass of air in motion due to barometric or thermobaric atmospheric events. Therefore, the power effective available is proportional to the cubic wind speed, but it is also in a direct relation with the potential energy of the air mass due to the earth's gravity force (10000 kg/m
2
—10 meters water column).
Dependence of power density on cubic wind speed sets forth the considerable influence that local ventilation characteristics have on technical and economic performances of an aerogenerator according to the prior art and makes the conversion of energy more complex. If the wind speed doubles, as it often happens for short periods, it is possible to obtain eight times the power and it is necessary to provide for a control system to skim the wind, reducing the blades stroke surface or lowering the efficiency of the rotor to avoid overloads. On the contrary if the speed reduces itself to one half, the converted power reduces itself substantially to an eighth, making it impossible to rely on the designed nominal power of the eolian plant.
Many kinds of rotors are known from the prior art, but the more tested recently have been rotors with a horizontal axis (parallel to the wind direction) that have fixed blades with a single blade, double blade, triblade, multiblade and cycloblade hub. Recently, the single blade system with a variable pitch terminal part of the rotor is being used in larger plants.
Conversion systems with a suitably shaped Magnus effect rotor that rotates with respect to the blade-holder hub, both central or peripheric, are not employed.
Patent RM 94 A 000529 owned by SILE/FLUID-SERVICE relates to a method for amplifying the dynamic surface pressure in mechanical machines where the dynamic surface pressure related to the fluid dynamic action of any gaseous or liquid composition is directed towards the external or lateral surfaces of an oppositely rotating thrust cylinder pair thus producing downstream of the cylinders themselves dynamic thrusts, which are greater than those obtained by means of a corresponding flat and static two-dimensional surface subjected to the same fluid dynamic thrust action.
Patent RM 94 A 000813 also owned by SILE/FLUID-SERVICE relates to a system for converting kinetic and potential energy in an eolian plant that channels fluid vein gathered by a concentrator into a central body where it interacts with the thrust rotors with an optimal incidence angle and where the reaction section with the rotors may be dimensionally regulated.
Furthermore, it is known that pressurization, a static method for filling a closed container with predetermined pressure according to the plant model, allows energetic density. This activates the kinetic component of the energy incident on a rotating element, to be increased when pressure and density are increased. Therefore, it is possible to work with low fluid speed and consequently low rotors speed even if working conditions are characterized by the same power and the same efficiency. In fluid-dynamics this may be related to the situation wherein, in a fall hydraulic system, the static head is a basic factor to define the dam power since flow rate is a fixed value that does not change with time. Therefore, if the hydrostatic basin supplies a limited power with the same section of fall tube, a greater fall pressure could be obtained by raising the basin.
Experimental work on Magnus effects started at the beginning of this century, and has been disclosed in a number of scientific international papers.
GB-A-2 031 072 discloses a wind energy exploitation system wherein the body of the blade does not rotate around its own axis but is hinged to a vertical shaft whose rotation movement generates electric energy. The blades lift when the wind speed increases in order to allow to take advantage also of weak winds.
In document GB-A-2 179 014, instead, the Magnus effect is exploited. This document uses this effect for the position control of a ship or for its propulsion, but not for generating energy.
U.S. Pat. No. 4,366,386 relates to a chiral turbine with “blades” which are perfectly cylindrical, and the turbine is placed in a non-pressurized environment.
Another example of the Magnus effect is the rotating cylinder used to power the Flettner and Cousteau rotor ship. Although cylindrical “blades” or “rotors” may be the best solution in the case of the Flettner and Cousteau rotor ship, they cannot be applied with practical and advantageous results in the case of a relative rotation between the “rotor” and the direction of the fluid in motion. This means, in particular, that the yield for the most common wind speeds over the course of the year (weak winds) would be low.
It should be noted that these solutions relate to an applicative method of the “translation” type, which involves a lift force distribution in KNm, in a parallel form, on the whole surface of the rotating cylinder.
According to the dynamical point of view, both in the eolian and hydrodynamic environment, a geometric configuration is not suited for a rotating blade that must also rotate on a rotation axis with different corresponding peripheral velocities that increase from the root of the “propeller” towards the terminal region of the blade, where the peripheral velocity has the largest value.
Consequently, a cylindrical configuration from the root to the end of the turbine (or propeller) is not adequate for the dynamical exploitation of all velocities related to the Magnus effect.
BRIEF SUMMARY OF THE INVENTION
The mathematical computation, the numerical simulation, and the already realized turbines, have demonstrated that, in order to obtain a dynamically correct form, the geometric configuration of the rotating rotor (blade) must assume a particular geometric shape, that is a “bulb” shape, on the distal end of the rotating blade itself.
The inventor generally refers to an inventive rotor having a bulb-shaped geometry as a “chiral rotor” or a “chiral turbine.” The meaning of the word “chiral” is an opposite dynamic action (180°) as will appear from the description (see for instance FIG.
4
).
The inventive chiral turbine is a new machine which is suited to exploit the dynamical components and the potential of any fluid substance in motion at slow velocity. Examples of these fluid substances include free air (wind), free water (rivers with low hydrostatic pressure and with a low speed of the water stream in m/s), gaseous com
Lopez F. Daniel
Sile S.R.L.
Smith , Gambrell & Russell, LLP
Woo Richard
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