VALVED DESIGNS

When it comes to valved designs, the shape can be calculated using using calculations in Tharratts paper.

Valved engines have the benefit of a good power to weight ratio and are compact.
However they are more difficult to build (valves to manufacture).
(8.1)

The main factor that is to be chosen is the type of valve design to be used from:

Petal Valve-A thin piece of shaped metal attached to a plate with holes in. When the plate experiences a negative pressure (from the chamber after combustion), the metal 'petals' flex upwards exposing the holes underneath and allowing fresh air in. (1.3)









(12.1)

V-Valve-This is a valve similar to the petal valve but the valves are in a 'V' shape to provide a straighter root for the incoming air to travel down. These are: More efficient than petal valve, easier/cheaper to repair (valves can be replaced individually), easy to scale up or down by changing the number of valves, more complex/expensive than petal valves.(1.8)

This type of valve is very similar to the type used on the V1 bomb. (14)


A v-valve is also very similar to the reed valve on a 2-stroke engine:

(15)

Rotary Valve-A spinning plate on the front of the jet with holes that line up in sync with the engine cycle: Holes are created when the Pulsejet needs a 'breath' of air and are blocked when the gasses are combusting. (1.7)

The Enthusiasts Guide has also given me an insight into the mathematical work that has been performed on pulsejets (1.9); a large amount of work was done by Tharrat in his paper 'The Propulsive duct'. This is easy to find on online (12.2) and describes relationships between measurements and power output etc. This allows one to calculate the measurements of a pulsejet through the desired characteristics.
Fredrik Westberg also gives calculations that can be used to design a valved pulsejet with details such as valve area etc. (5.1)

For the purpose of deciding a design, I am going to treat all valved designs as one to evaluate against other designs.