Electric Wheelchair Vsi Conroller

Wind Energy Wind

STRUCTURAL Resistance SUBJECT TO A PROFILE OF CENTRIFUGAL FORCE

The biggest problem of the blades of a turbine is the ultimate runaway propeller caused either by excessive wind speed or lack of reaction from the alternator issue that we have discussed previously. Sudden changes in wind direction or speed of response threaten the control systems are often ineffective in these circumstances although not very frequent enough to be presented only once to produce the collapse of the blades.

In general when a turbine has a manual brake and the manufacturer warns that "the unit must be stopped when wind speed is great," exempting from any responsibility for breakage of the blades caused the lack of response to that warning, is recognizing that the control system is ineffective. It is understood that the charge of the operation has no possibility of a permanent control nor does it have the right tools to make the decision of when to be stopped and even having them, just the anemometer detects a speed burst when the collapse occurred. In other words, to control the braking mechanism to be truly effective the operation must also be fully automated and capable of absorbing power, often catastrophic, the wind power into play. Remember that wind power is proportional to the cube of its speed (energy * of fluids in motion, CD2), thus, a wind of, say, 100 km / hour this a few times a year and only a few moments, only bursts, has a thousand times more energy to one of 10 Km / hour or 8 times higher than a 50 km / hour. It is impossible to counter such power or electro-mechanical means as claimed in some models that have already shown their ineffectiveness. The control must be streamlined with some caveats as we have seen. Within these mechanisms is the change in position of the plane of rotation of the propeller on the wind direction (see * speed control, CD1), that automatically placed to 90 degrees reduces to zero the exposed surface and therefore stop turning him back to the front position. The mentioned mechanism is used in large wind turbines but the operation is completely automatic and a signal (Pitot tube) is sent to the computer and puts swivel flag immediately until the situation normalizes. The mechanical inertia of these units, whose total weights of the parts subject to rotation, technically called the GD square, including the propeller, gears, patches and generator rotor is so high that gives time for the system of rotation to place a banner before the occurrence of the catastrophic increase in speed. Wind Turbines Small is also used to change the plane of rotation or also horizontally or laterally. However, this mechanism has limitations as the influence of the gyroscopic effect begins to be critical to propeller dimensions, both in weight and geometric, prevents a reaction fast enough to change the plane of rotation when the bursts are sudden and violent and gyroscopic inertia prevents the change of direction. The limitation of this system depends on the physical dimensions of the propeller, material, etc. but broadly speaking we can say that does not go beyond 2 to 3 meters in diameter. In other words, the control system rpm by change of plane of rotation is the result of a delicate balance between the inertia of the parties under rotation (GD2) and the gyroscopic effect resulting from a balance between the weight of the material and the diameter of the blades. For those who can not understand the gyroscopic effect dedicate a paragraph mentioning the application of it in some motorcycles that despite its unstable equilibrium resulting from the lack of a third point of support on the ground (third round), can be kept vertical time enough to allow the change of light at traffic lights. Even easier to spin that maintains its plane of rotation despite being supported on one point: to high-speed stability. To avoid this problem in larger propeller speed limits should not be subject to the change of plane of rotation. Between traditional systems is the windcharger maintaining the fixed blade pitch but, overcoming a spring system opens up Chicana aerodynamically braking the blades keeping the plane of rotation. Aerowatt stall also slows but changing the pitch of the propeller. In the same way our system has a wing for each blade due to centrifugal force overcomes a spring and moves out while touring the help of a trapezoidal thread losing performance and maintain its constant speed, regardless of load gyroscopic inertia or wind speed and immediate response necessary condition for the restriction is effective. The three systems mentioned, Aerowat, Windy West windcharger or act that way.

The destruction of the blade operates as a result of centrifugal force, through an instantaneous increase the speed of rotation overcomes the resistance of the material, not prepared for that contingency. Needless to say, this speedup also promotes increased thrust, as is the case in a gyroplane or helicopter, resulting in a bending moment on the root of the blades adds to the traction force centrifuge.


Analysis of centrifugal force and its strong balance

hereinafter called dfc caused by centrifugal force on a rod of a given material of tensile strength σ subject to rotate at a speed of rotation ω

where dm is the mass corresponding to infinitesimal dR , section S of the rod and specific gravity ρ the material of the same

thus total centrifugal force and the integral

mks Using the metric system is speed in meters over seconds when the resistance is in kg / m 2, the specific gravity of the rod in kg / m3 and the acceleration of gravity in meters on second squared

From this formula follows that the speed of collapse of the blade depends on the square root of the relationship between the tensile strength of the material and the specific gravity of it and inversely with the square root of the relationship natural logarithm, base e, the outer radius of the rod against the radius chosen for calculation. With these considerations, it is easy to see that the materials most suitable for shovel manufacturing reinforced plastics are starting with the polyester fiberglass, followed by the carbon fiber with the same resin or epoxy and the maximum ratio epoxy and Kevlar

Analysis on the influence of the terms .

A helicopter blade is made from an aluminum alloy A7075 A 2024 or whose specific weight is about 2.8 and whose resistance is between 50 to 58 kg/mm2.

The blade is hollow plate made of only a few tenths of thick and filled with special polyurethane foam, so that the stress in the root of the blade is minimal. We have attached a photo with the propeller at rest where one can appreciate its flexibility. You can imagine what happens at work: if the helicopter blades should hang its own weight and were so distorted at rest, how is it possible that are capable of staying up nearly horizontal when the weight exceeds rise over thousand times its own weight?. The answer is obvious: the resultant of the lift force and the centrifugal is almost horizontal, ie the centrifugal force is much greater than the lift.

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