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Farting at France

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So, a man in England by the name of Colin Furze has built the biggest valveless pulsejet EVAR in order to fart at France.

Best of luck?

The best example of an applied pulsejet is probably the V-1 Flying Bomb that was near the end of World War II. The Luftwaffe launched over 9,000 of the missiles at Great Britain and the Allies nicknamed the weapon the "Buzz Bomb" for the distinctive noise of the pulsejet. Unlike the pulsejet built by Mr.�Furze, the V-1 had a valved pulsejet. In this layout the pulsejet is a long tube. The nose end of the tube has a reed valve. These open to let air in, but then are forced closed during combustion in order to force the exhaust to the rear.

A computer-generated mock-up of a reed valve.

The problem with reed valves is that they are delicate and will be opening and slamming shut frequently. The V-1 operated at about 60 Hertz, but only had to be robust enough to survive the flight from the coast of France to London. Here's an animation of the operation of a valved pulsejet

A valveless pulsejet gets around this by using a u-shaped design to point the intake backwards, so the airflow from the vehicle cannot disrupt combustion. Here's a simple, clean diagram from Popular Mechanics:

The article is about New York's Madagascar School of Mechanical Arts and Ballistic Sciences (!). A valveless pulsejet is operated by spraying compressed air into the short end. The fuel injectors shoot fuel into the combustion chamber and a spark plug ignites it. The exhaust exists from both ends. This creates a low-pressure region in the combustion chamber which pulls fresh air in via the shorter leg while fuel is injected. Hot exhaust is also pulled in from the longer leg, and this ignites the mixture, repeating the process perhaps hundreds of times per second. Here's a video from PulseJetEngines.com:

These things are pretty popular with hobbyists because they can be built from scrap with simple techniques, then strapped to a car, a sled, or whatever. The air show came to Grand Junction a couple years ago and one of the performers was a guy in a rocket outhouse powered by a pulsejet. So yeah, taste does not walk hand in hand with pulsejets.

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