VALVELESS
The 'Chinese Pulse jet'/Focused wave Pulsejet
Thermojet
Lockwood-Hiller Pulsejet
A valveless Pulsejet works by having a combustion chamber with two tubes leading off it of unequal length and diameter; an exhaust (larger tube) and an intake (smaller tube). A fuel/air mixture is combusted in the chamber (so-called) creating two spurts of hot expanding gas that travel mainly down the exhaust but some down the intake-this creates thrust. This leaves a void in the combustion chamber and as the hot expanding gasses are travelling down the exhaust, they have momentum and continue to travel down the tube even when the pressure in the combustion chamber drops below atmospheric. This creates a partial vacuum in the chamber. Because the pressure of air is now greater outside the pulsejet, air is pushed into the combustion chamber through the shorter intake tube and mixed with fuel. The hot gasses still in the exhaust are partially drawn back and cause this mixture to reignite. This cycle repeats at around 250 times a second in small pulsejets. The intake tube of a Valveless engine is usually faced backwards so expanding gasses don't create negative thrust. (7.1) (image-10)
VALVED
Valved designs are all very similar in general shape/geometry; the main differences are the type of valve used:
Petal Valved
V-valve
Rotary Valve
Valved designs run on the same principal but have mechanical valves at the front to control the expanding gasses; they close when the gasses are expanding so they only go down the exhaust, and open when the pressure drops letting fresh air into the engine, a new mixture being created, it igniting, and the cycle repeating. (1.4)
(11)I will explore all of these designs/types before comparing them and making a decision on which I will base my own on.
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