As you can see on this picture (FIG. 1), if you need to close a thermoacoustic standing wave engine, then the closed resonator part (right side) should be same length as left side, the sound generator base.
The whole system is a half wavelenght thermoacoustic engine.
The stack's center on the λ/8 exactly.
But what we can do with a mechanical resonator?
We can replace the whole resonator tube length( λ/4=4/8 of whole tube length) + the volume between the cold heat exchanger to the resonator tube ( λ/16= 1/8 length).
So what we can do?
We can replace the whole length 5/8th part.
That is nearly 2/3 of full length!
After we get a short engine like this:
Where the 104 is a buffer volume. This volume help for the gas flow going trough the 112 stack
also the 108-110 heat exchangers.
114 is the piston and the back side is a generator also "gas spring volume", or solid spring of course.
the next post will be very interesting for you! :)
friend Simi112's developed an engine what I called "Metronome".
engine had a good torque, and the frequency was so stable.
modified a water piston Ringbom engine.
The water piston is the power piston in a basic Ringbom constructions as you know. Simi112 changed the pistons, and created a big diameter piston to move the displacer, and a smaller one with water in a tube for phase changing. The engine works well! (check below the video) In March of 2014 I've seen an interesting engine on Dreisotech's youtube channel. He called it Very Simple High Frequency Engine (VSHFE). This engine is same as Metronome the only different is the phase changer piston, because the piston is air here. This construction is faster than the water piston version. When I showed the video to Simi112, we start to develope this construction and we found a little suprise there. The tube could be tune the engine's frequency also we can tune up the whole engine to a resonant frequency, where the amplitude is maximised, and the torque is great! So this engine is a moving displacer thermoacustic engine too! What??? How??? Is this possible? But the cycle is really changed! Not Stirling as in a Ringbom! The tube has a greater resistance than the power piston and the engine works closely as a Manson engine. The tube works like a gas-diode valve. It looks like a fully open engine, but when the pressure increase in the cylinder, then the gas push out the power piston first, and after can „wide open” the gas-diode.
When the "valve" is "opened", the gas piston start to move out with a great momentum and created a vacuumised cylinder after start to cool down the gas in the cylinder. When the inward phase coming and the gas diode "open" again then the gas piston create a pressurised section in the cylinder before the gas start to heat up! It is really interesting and strange. Because the power piston has an increased power under the whole strokes as like Manson!!! But when the "valve" is "open" then the gas piston pre-vacuumise, also pre-pressurise the cylinder in the working method.
The Manson has only pressure relief sections! So...we have an engine with Manson cycle (more or less) with a bigger working pressure intervall. I'll try to show you what I mean about the p-V diagram