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A pulse jet engine (or pulsejet) is a very simple form of internal combustion engine wherein the combustion occurs in pulses and the propulsive effort is a jet; a reaction to the rearward flow of hot gases. The internal combustion engine is an engine in which the combustion of fuel and an oxidizer (typically air) occurs in a confined space called a combustion chamber. ...
For other uses, see Pulse (disambiguation). ...
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A typical pulsejet comprises an air intake fitted with a one-way valve, a combustion chamber, and an acoustically resonant exhaust pipe. The valving is accomplished though the use of reed valves or, in a valveless pulse jet engine, through aerodynamics. Fuel in the form of a gas or liquid aerosol is either mixed with the air in the intake or injected into the combustion chamber. Once the engine is running it requires only an input of fuel, but it usually requires forced air and an ignition method for the fuel-air mix. Once running, the engine is self-sustaining. A check valve is a mechanical device, a valve, that normally only allows fluid to flow through it in one direction. ...
A combustion chamber is part of an engine in which fuel is burned. ...
This article is about resonance in physics. ...
Reed valves consist of thin flexible metal or fiberglass strips fixed on one end that open and close upon changing pressures across opposite sides of the valve much like heart valves do. ...
Valveless pulse jets were developed during the 1950s and 1960s and patented by Hiller-Lockwood in 1967. ...
This article does not cite any references or sources. ...
History Martin Wiberg (1826-1905) developed the first pulse jet in Sweden. Pulsejet engines are characterized by extreme simplicity, low cost of construction, poor fuel economy and very high noise levels. The high noise levels make them impractical for other than military applications and similarly restricted applications. Pulsejets have been used to power experimental helicopters, the engines being attached to the extreme ends of the rotor blades. One proposed design during WWII was the Focke-Wulf Fw Triebflugel, although the craft was never built. In this application they have the distinct advantage of not producing the usual reaction torque upon the fuselage and the helicopter may be built without a tail rotor and its associated transmission and drive shaft, greatly simplifying the aircraft (though it is still necessary to rotate the fuselage relative to the rotors in order to keep it pointing in one direction). Pulsejets have also been used in both tethered and radio-control model aircraft. The speed record for tethered model aircraft is 186 miles per hour (299 km/h), set in the early 1950s. Martin Wiberg (September 4, 1826 - December 29, 1905) was born in Viby, Scania enrolled at Lund University in 1845 and became a doctor of philosophy in 1850. ...
The Focke-Wulf Triebflügel was another in the line of German concept craft produced late, in this case 1944, during the Second World War. ...
The principal military use of the pulsejet engine was in the V-1 flying bomb, the engine's characteristic droning noise earning it the nicknames "buzz bomb" or "doodlebug". The V-1 was a German cruise missile used in World War II, most famously in the bombing of London in 1944. Pulsejet engines, being cheap and easy to construct, were the obvious choice for the V-1's designers given the Germans' materials shortages and over-stretched industry at that stage of the war. Modern cruise missiles do not generally use pulsejet engines but true rocket or gas turbine engines. The V-1 (German: Vergeltungswaffe 1) was the first guided missile used in war and the forerunner of todays cruise missile. ...
A Taurus KEPD 350 cruise missile of the Luftwaffe A cruise missile is a guided missile which uses a lifting wing and most often a jet propulsion system to allow sustained flight. ...
Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki TÅjÅ Casualties Military dead: 17,000,000 Civilian dead: 33,000...
For other uses, see Blitz. ...
1944 (MCMXLIV) was a leap year starting on Saturday. ...
A Soyuz rocket, at Baikonur launch pad. ...
This machine has a single-stage centrifugal compressor and turbine, a recuperator, and foil bearings. ...
Functioning
 Pulse jet schematic. First part of the cycle: air intake (1), mixed with fuel (2). Second part: the valve (3) is closed and the ignited fuel-air mix (4) propels the craft. The combustion cycle comprises six phases: Ignition, Combustion, Exhaust, Induction, Compression, and (in some engines) Fuel Injection. Image File history File links Pulse jet schematic. ...
Image File history File links Pulse jet schematic. ...
Starting at ignition within the combustion chamber, a high pressure is raised by the combustion of the fuel/air mixture. The pressurized gas from combustion cannot exit forward through the one way intake valve and so exits only to the rear through the exhaust tube.
It is the inertial reaction of this gas flow that causes the engine to provide thrust, this force being used to propel an airframe or a rotor blade. The inertia of the traveling exhaust gas causes a low pressure in the combustion chamber. This pressure is less than the inlet pressure (upstream of the one-way valve), and so the induction phase of the cycle begins.
In the most simple of pulsejet engines this intake is through a venturi which causes fuel to be drawn from a fuel supply. In more complex engines the fuel may be injected directly into the combustion chamber. When the induction phase is complete a reflected high pressure wave from the tailpipe compresses the charge, which is ignited by residual heat from the previous cycle. A copper aspirator. ...
Valved Design There are two basic types of pulsejets. The first is known as a valved or traditional pulsejet and it has a set of one-way valves through which the incoming air passes. When the air/fuel is ignited, these valves slam shut which means that the hot gases can only leave through the engine's tailpipe, thus creating forward thrust.
The cycle frequency is primarily dependent on the length of the engine. For a small model-type engine the frequency may be typically around 250 pulses per second — whereas for a larger engine such as the one used on the German V1 flying bomb, the frequency was closer to 45 pulses per second.
Valveless Design The second type of pulsejet is known as the valveless pulsejet. This name is really a misnomer. These engines have no mechanical valves, but they do have aerodynamic valves, which, for the most part, restrict the flow of gases to a single direction just as their mechanical counterparts. Indeed they have no mechanically moving parts at all and in that respect they are similar to a ramjet. A ramjet, sometimes referred to as a stovepipe jet, is a type of jet engine. ...
With these engines, the intake and exhaust pipes usually face the same direction. This necessitates bending the engine into a "U" shape (the Lockwood-Hiller design is made this way) or placing a 180 degree bend in the intake tube. When the air/fuel mixture inside the engine ignites, hot gases will rush out both the intake tube and the exhaust tube, since the aerodynamic valves "leak". If both tubes weren't facing in the same direction, less thrust would be generated because the reactions from the intake and exhaust gas flows would partially cancel each other. This idea was the brainchild of a French propulsion research group named SNECMA. Snecma was one of the worlds leading aerospace corporations which merged with SAGEM to form SAFRAN. Snecma is now a subsidiary of the SAFRAN Group and previous Snecma subsidiaries have been reorganised within the wider group. ...
The advantage of the aerodynamically valved pulsejet is simplicity. Since there are no moving parts to wear out, they are easier to maintain and simpler to construct. However, they are more difficult to optimize. Moving parts are the components of a device that undergo continuous or frequent motion, most commonly rotation. ...
Outlook Pulsejets survive today in target drone aircraft, flying model aircraft, fog generators and home heating equipment. Some experimenters continue to work on improved designs. The engines are difficult to integrate into manned aircraft design due to high fuel consumption, noise, and vibration. A Die Cast Boeing 747-800 static model. ...
The Pulse detonation engine (PDE) marks a new approach towards non-continuous jet engines and promises higher fuel efficiency compared even to turbofan jet engines. Pratt & Whitney and General Electric now have active PDE research programs. This article does not cite any references or sources. ...
Schematic diagram of high-bypass turbofan engine CFM56-3 turbofan, lower half, side view. ...
Pratt & Whitney is an American aircraft engine manufacturer whose products are widely used in both civil and military aircraft. ...
“GE†redirects here. ...
See also This article does not cite any references or sources. ...
Valveless pulse jets were developed during the 1950s and 1960s and patented by Hiller-Lockwood in 1967. ...
External links - http://www.pulse-jets.com/ - An international site dedicated to pulsejets, including design and experimentation. Includes an extremely active forum composed of knowledgeable enthusiasts.
- http://www.Beck-Technologies.com/ - A site for hobby jet propulsion, specifically valved and valveless pulsejet engines. They offer many plans, and have a lot of useful information
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