Rotary Pulse Jet Engine


The GE Ecomagination Challenge 2011: Powering your home challenge officially came to an end on 15th. March 2011 and is now in the judging stage. As expected the Challenge has resulted in several noteworthy entries, including some in wind turbines, and solar. But there were more interesting and unusual ideas, that seem truly radical to the uninitiated.. Among those that caught the eye were A dual use power co-generation concept that describes a new type of rotary engine that uses a flywheel to store kinetic energy which can then be drawn off to power a home or a car, hence the term dual use. The inventor is at pains to explain that two different units would be needed to fulfill these different tasks, one in the car and one in the home. What is of interest in this concept is the scale of the power involved, it generates power in terms of KWh rather than in terms of mere watts as home solar and wind normally do.
The Flywheel Assisted Rotary Pulse Jet Engine uses intermittent rocket power to spin a rotor.
From RPJ
Thus, it is a rocket powered machine that functions in the same manner as an Internal Combustion piston engine. How is this possible ?
It is not only possible, says the inventor, but it is also based on one of the earliest inventions patented by Robert Goddard, the father of modern rocket science, although his version used solid propellant rather than liquid or gasified fuel, in contrast to the present invention. It is a reaction engine, rather than an expansion engine, like the steam engine or IC piston engine. In short pre-compressed air from a stored source is mixed with fuel and fed into two combustion chambers simultaneously, the compressed air/fuel mixture is ignited in the fully sealed combustion chamber and the hot gases of combustion are released through a venturi, turning the rotor in the opposite direction. This is based on Newtons Third Law of Motion: For every action there is an equal and opposite reaction. Here is an exploded view of the Rotary Pulse Jet Engine:
From RPJ
The normal drawback in the IC piston engine is the conversion from linear to rotary motion. In order to achieve this conversion a lever is needed. In the IC piston engine this lever is represented by the throw of the crank shaft. This length is governed by the ratio between the bore and the stroke of the engine, and in most cases is less than half this ratio. Thus if you have a 3 x 3 (bore and stroke) engine the maximum length of the crank throw can be less than half this or less than half an inch. Why or how, is this important? Archimedes of Eureka fame once stated : Give me lever that is long enough and I will move the world ! There are sound physical principles behind this statement. For instance, take a lever that is 1 ft long attached at one end to an axle ( imagine a spanner turning a nut) and exert a force of 1 pound at right angles and you generate a torque of 1 ft lb at the axle. Increase the length of the lever to 3 ft and the same 1 pound of force exerted on its end will result in a torque of 3 ft lbs being generated and so on. If the length of the lever is increased to 10 ft, the same 1 pound of force exerted on its end will result in a torque of 10 ft lbs being generated. In simpler terms a lever acts as a force multiplier. In the IC piston engine, because the length of the lever ( crank throw) is so short it acts as a force reducer. Thus if a force of 4000 lbs is exerted on the piston head by the expansion of gases of ignition a 1.45 inch ( lever 0.12 ft) will reduce this force to just:
483 ft lbs of torque, further since the force applied by the connecting rod is not at right angles but at a continuously changing angle as the piston moves down the cylinder and the fact that the exhaust valve opens at 15 20 degrees before BDC results in a further reduction by a factor of 0.173. So the initial force on the piston head is reduced to just 83 foot pounds of torque, this is a massive reduction and is one of the reasons that the IC piston engine is such an inefficient machine. By contrast the Rotary Pulse jet Engine uses a lever that is almost one and a half feet long it also exerts force at right angles, and so is far more efficient than anything that has gone before. . For example in the IC piston engine design a torque of 83 foot pounds as per the example given above requires a force of 4000 pounds to be exerted on the piston head, by contrast the Rotary Pulse Jet Engine would need a force of just 55 pounds to generate the same torque of 83 foot pounds. Experiments with the bazooka (invented in the U.S.A ) which works on exactly the same principle as the Rotary Pulse Jet Engine show that the difference in performance between a bazooka and a normal artillery piece of similar caliber is minimal although the bazooka does use two or three times the amount of propellant. This example serves to illustrate the fact that the Rotary Pulse Jet will exert almost the same initial force as the IC piston engine but will develop an exponentially greater amount of power. This fact is exploited by the Rotary Pulse Jet Engine. The extra power generated is used to impart kinetic energy to a flywheel and then this kinetic energy is slowly bled off to power a vehicle or a home depending on the sue to which the stored energy is used. Estimates show that the RPJ will take only 10 seconds to impart a kinetic energy of 6MJ to a flywheel this amount of energy will power a normal car for 10 minutes to 15 minutes. So that is the basic idea switch the engine on for 10 seconds, switch it off and power the vehicle for the next 10 15 minutes on the power that the engine generated in those 10 seconds. Maybe this engine is a step in the right direction, away from our dependence on the IC piston engine.

D. James is an inventor who is interested in Green Energy and its implementation.