Editing Pulsejet (section)

===Valved designs===
[[File:Pulse Jet schematic.svg|thumb|Pulsejet schematic. First part of the cycle: air flows through the intake (1), and is mixed with fuel (2). Second part: the ignited fuel-air mix expands, closes the valve (3) and exits through the exhaust pipe (4), propelling the craft.]]

Valved pulsejet engines use a mechanical valve to control the flow of expanding exhaust, forcing the hot gas to go out of the back of the engine through the tailpipe only, and allow fresh air and more fuel to enter through the [[intake]] as the inertia of the escaping exhaust creates a partial vacuum for a fraction of a second after each detonation. This draws in additional air and fuel between pulses.

The valved pulsejet comprises an intake with a one-way valve arrangement. The valves prevent the explosive gas of the ignited fuel mixture in the [[combustion chamber]] from exiting and disrupting the intake airflow, although with all practical valved pulsejets there is some 'blowback' while running statically or at low speed, as the valves cannot close fast enough to prevent some gas from exiting through the intake. The superheated exhaust gases exit through an acoustically [[resonance|resonant]] exhaust pipe.

The intake valve is typically a [[reed valve]]. The two most common configurations are the daisy valve, and the rectangular valve grid. A daisy valve consists of a thin sheet of material to act as the reed, cut into the shape of a stylized daisy with "petals" that widen towards their ends. Each "petal" covers a circular intake hole at its tip. The daisy valve is bolted to the manifold through its centre. Although easier to construct on a small scale, it is less effective than a valve grid.

The cycle frequency is primarily dependent on the length of the engine. For a small model-type engine the frequency may be around 250 pulses per second, whereas for a larger engine such as the one used on the German [[V-1 (flying bomb)|V-1 flying bomb]], the frequency was closer to 45 pulses per second. The low-frequency sound produced resulted in the missiles being nicknamed "buzz bombs."