I think simple jam jars seem to have some important small characteristics. I'm not sure yet if these are all true. But I think they are on the basis of evidence of many posted experiences I've read. And if so, I'd like to use them.
1.)They need a stiff bottom and sides to reflect the pulse.
2.) They don't need a stiff top. In fact a flexible top may possibly help up to a small amount. It will however affect the needed orifice size, frequency and other system requirements.
3.) The thinner the metal surrounding the aperture, the better. This approaches the thin plate orifice ideal.
4.) A pipe tail has the effect of ejecting the exhaust in a directed line, while taking in air from all directions yielding a net thrust. reaction. This is similar to the action of pipes in a putt-putt toy steam boat motor. This same directing action on the outflow increases the "bark"
If 2 is true, then maybe I can use the top as a pseudo-valve. As well as a power diaphragm to take work out.
If the end of an external low pressure gas feed pipe nearly touches a flexible top it can still feed gas. If instead of a single aperture, five small holes are located outside and around the pipe diameter. the gas can enter those holes. If an explosion occurs in the jar, the top will be driven outward, cutting off the flow of gas, like a valve. When the pressure collapses in the jar, the valve is drawn away from the pipe and a mixture of air and gas is lip fed into the combustion chamber through the 5 holes.
With a gas, we need a source of ignition, unlike methanol, which remains burning in the bottom of the jar. Maybe a glow plug. Or, if the jar heats enough, that could do it. So we stop water cooling it and let it glow.
Yes?
- Schematic of valved jar combustor.
