How the Rotary Pulse Jet Engine works

Working of the RPJ
	The Rotary Pulse Jet Engine works on the same principles as the internal combustion engine. Namely it ignites a mixture of compressed air and fuel in order to provide power. There the similarity ends. While the Internal Combustion piston engine uses a piston to compress air, the Rotary Pulse Jet engine uses pre-compressed air from an external tank to fill the combustion chambers (rocket pods) with air at a pressure of 125 psi which gives a compression ratio of approximately 9 : 1. An IC Engine uses the forces of expansion of gases to force the piston down the cylinder, thus after the fuel/air mixture is ignited it expands, this expansion of gases pushes the piston down the cylinder. It is a design that has remained unchanged since it was first invented by Nicholas Otto in 1865. The RPJ engine by contrast uses the reactive forces of the hot gases of combustion escaping at speed through the convergent divergent nozzle (CDN) in order to create power. This is in keeping with Newton's third Law : "For every action there is an equal and opposite reaction...." It is is the principle on which all rockets work. The Rotary Pulse Jet Engine can therefore be considered as an intermittent or pulsed rocket engine, in which the rocket pods fire only intermittently and not continuously. The Rotary Pulse Jet may therefore be considered as the first rocket type of engine that yields a good fuel economy. The Rotary Pulse Jet Engine uses a rotary union (see article) to supply fuel and air to the combustion chambers, without the use of a rotary union it would be absolutely impossible to implement this design. A rotary union enables fluids (air/petrol etc.) to be supplied to a rotating object while itself remaining stationary. The rotary union is fixed directly onto the main shaft and supplies compressed air and fuel to the combustion chambers through passages in the rotor. Without a rotary union, the fuel lines and compressed air lines would get twisted and shredded to bits and it would be impossible even to conceive of such a simple design wherein the engine consists basically of just a rotor with a diameter of 8"-12" and a width of 5" and little else! It is the use of a Rotary Union that makes possible such a brilliant and simple engine design.. Rotary unions are commercially available that can withstand pressures of 10000 psi and 20,000 rpm. Similarly the air in the compressed air tank is constantly replenished by a commercially available compressor of dimensions 8" by 5" capable of continuously supplying 8 cu ft of compressed air at 125 psi. Thus the air in the main compressed air tank is constantly being replenished as it is used up.
Rockets
	Rockets are the most powerful engines yet developed, they are the only engines that are capable of developing enough power to break free of the earth's gravity and enter space. No other engine, either steam, piston or turbine can achieve this. Weight for weight rockets are the most powerful of all types of engine designs. Yet they have their disadvantages, continuous combustion at very high temperatures and pressures means that they place huge stresses on materials and use up enormous amounts of fuel. The challenge faced by the Rotary Pulse Jet Engine is to extract power from a rocket type of engine while maintaining a relatively cool running temperature and a good fuel economy.
Calculation of power from a Rotary Pulse Jet Engine:
	The rocket pods (combustion chambers ) are filled with a fuel air mixture at a pressure of 125 psi, this yields a compression ratio of 9 : 1. This compressed fuel/air mixture is then ignited using a piezo-electric sparking device. As soon as the fuel/air mixture is ignited the pressure within the combustion chamber rises to 500psi and the temperature reaches 2000 ⁰ Centigrade. Almost simultaneously a valve to the CDN is opened and the hot gases of combustion rush out of the convergent divergent de laval nozzle at speeds in excess of 5,000 ft/sec. this thrust drives the rotor in the opposite direction. Assuming that the combustion chamber is in the form of a cylinder with a diameter of 2.5" the pressure on the back plate can easily be calculated by multiplying the area of the back plate by the internal pressure within the combustion chamber. This yields 1.25²x 3.14 x 500 = 2453.12 lbsf on the back plate, this force is multiplied by two since both combustion chambers are firing simultaneously and contributing their force in the same direction. Thus the total force on the back plates = 2 x 2453.12 = 4906.25 lbsf. When the valve to the CDN opens this pressure is converted into kinetic energy.
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