Tesla Turbine - Engineering Seminar Report

INTRODUCTION

Interestingly, using the word “turbine” to describe Tesla’s invention seems a bit misleading. That’s because most people think of a turbine as a shaft with blades — like fan blades — attached to it. In fact, Webster’s dictionary defines a turbine as an engine turned by the force of gas or water on fan blades. But the Tesla turbine doesn’t have any blades. It has a series of closely packed parallel disks attached to a shaft and arranged within a sealed chamber. When a fluid is allowed to enter the chamber and pass between the disks, the disks turn, which in turn rotates the shaft. This rotary motion can be used in a variety of ways, from powering pumps, blowers and compressors to running cars and airplanes. In fact, Tesla claimed that the turbine was the most efficient and the most simply designed rotary engine ever designed.

Tesla’s new engine was a bladeless turbine, which would still use a fluid as the vehicle of energy, but would be much more efficient in converting the fluid energy into motion

MAIN PARTS OF TESLA’S TURBINE

The Rotor
In a traditional turbine, the rotor is a shaft with blades attached. The Tesla turbine does away with the blades and uses a series of disks instead. The size and number of the disks can vary based on factors related to a particular application. It contain a “plurality” of disks with a “suitable diameter.”

Each disk is made with openings surrounding the shaft. These openings act as exhaust ports through which the fluid exits. To make sure the fluid can pass freely between the disks, metal washers are used as dividers. Again, the thickness of a washer is not rigidly set, although the intervening spaces typically don’t exceed 2 to 3 millimeters.

A threaded nut holds the disks in position on the shaft, the final piece of the rotor assembly. Because the disks are keyed to the shaft, their rotation is transferred to the shaft.

The Stator
The rotor assembly is housed within a cylindrical stator, or the stationary part of the turbine. To accommodate the rotor, the diameter of the cylinder’s interior chamber must be slightly larger than the rotor disks themselves. Each end of the stator contains a bearing for the shaft. The stator also contains one or two inlets, into which nozzles are inserted. Tesla’s original design called for two inlets, which allowed the turbine to run either clockwise or counterclockwise.

This is the basic design. To make the turbine run, a high-pressure fluid enters the nozzles at the stator inlets. The fluid passes between the rotor disks and causes the rotor to spin. Eventually, the fluid exits through the exhaust ports in the center of the turbine.

One of the great things about Tesla turbine is its simplicity. It can be built with readily available materials, and the spacing between disks doesn’t have to be precisely controlled. It’s so easy to build, in fact, that several mainstream magazines have included complete assembly instructions using household materials.

Tesla’s Turbine Operation

You might wonder how the energy of a fluid can cause a metal disk to spin. After all, if a disk is perfectly smooth and has no blades, vanes or buckets to “catch” the fluid, logic suggests that the fluid will simply flow over the disk, leaving the disk motionless. This, of course, is not what happens. Not only does the rotor of a Tesla turbine spin — it spins rapidly.

The reason why can be found in two fundamental properties of all fluids: Adhesion and Viscosity. Adhesion is the tendency of dissimilar molecules to cling together due to attractive forces. Viscosity is the resistance of a substance to flow. These two properties work together in the Tesla turbine to transfer energy from the fluid to the rotor or vice versa. Here’s how:

·         As the fluid moves past each disk, adhesive forces cause the fluid molecules just above the metal surface to slow down and stick.

·         The molecules just above those at the surface slow down when they collide with the molecules sticking to the surface.

·         These molecules in turn slow down the flow just above them.

·         The farther one moves away from the surface, the fewer the collisions affected by the object surface.

·         At the same time, viscous forces cause the molecules of the fluid to resist separation.

·         This generates a pulling force that is transmitted to the disk, causing the disk to move in the direction of the fluid.

The thin layer of fluid that interacts with the disk surface in this way is called the boundary layer, and the interaction of the fluid with the solid surface is called the boundary layer effect. As a result of this effect, the propelling fluid follows a rapidly accelerated spiral path along the disk faces until it reaches a suitable exit. Because the fluid moves in natural paths of least resistance, free from the constraints and disruptive forces caused by vanes or blades, it experiences gradual changes in velocity and direction. This means more energy is delivered to the turbine. Indeed, Tesla claimed a turbine efficiency of 95 percent, far higher than other turbines.

The Future of the Tesla Turbine

Tesla always was a visionary. He did not see his bladeless turbine as an end itself, but as a means to an end. His ultimate goal was to replace the piston combustion engine with a much more efficient, more reliable engine based on his technology. The most efficient piston combustion engines did not get above 27 to 28 percent efficiency in their conversion of fuel to work.

Tesla never saw the car produced, but he might be gratified today to see that his revolutionary turbine is finally being incorporated into a new generation of cleaner, more efficient vehicles. One company making serious progress is Phoenix Navigation and Guidance Inc. (PNGinc), located in Munising, Michigan. PNGinc has combined disk turbine technology with a pulse detonation combustor in an engine the company says delivers unprecedented efficiencies. There are 29 active disks, each 10 inches (25.4 centimeters) in diameter, sandwiched between two tapered end disks. The engine generates 18,000 rpm and 130 horsepower. To overcome the extreme centrifugal forces inherent to the turbine, PNGinc uses a variety of advanced materials, such as carbon-fiber, titanium-impregnated plastic and Kevlar-reinforced disks.

Clearly, these stronger, more durable materials are critical if the Tesla turbine is going to enjoy any commercial success. Had materials such as Kevlar been available in Tesla’s lifetime, it’s quite likely that the turbine would have seen greater use. But as was often the case with the inventor’s work, the Tesla turbine was a machine far ahead of its time.