Hi there, I'm Attila Blade, a huge fan of the DIY Stirling and hot air engines. You are currently on the Blade's World channel's blog.
I made a lot of experiments in the past 20 years from the beer can engines to a nicely machined desktop gadgets also I worked in professional projects worldwide.
You will find here DIY projects, homemade Stirling engine tutorials and interesting experiments, monthly as possible.
THX any help!
It was an annular designed TASHE engine with conical shaped ends and it worked with membranes.
The membranes could help to reduce the Gedeon streaming in the loop.
That stream is a gas flow where the acoustic fluctuation goes.
It could reduce the cycle efficiency.
So the membrane could stop this flow and also it could substitute some gas volume because the gas in tube has mass and elasticity aka spring constant. So it is a spring-mass system.
My friend Tibsim is made an interesting video in his channel about how the gas "piston" moves in the tube
also how the heat start to amplificate this movement:
You could calculate how long could be a full wave length looped thermoacoustic engine at 20˙C and 50Hz.
343,4 m/s : 50 = 6,868 m
So it is a big circle.
The inner geometry and the membranes gives some possibility to reduce the loop's length drastically
because what we want
that is a pressure swing phase shift in the regenerator.
This is a complicate calculation originally few program could help to reduce the optimization,
but I found an easy way how to make a DIY simple
free piston TASHE (thermoacoustic Stirling heat engine) also I made a tutorial for that.
No calculations, no expensive tools, just a simple and working model.
The first working prototype was made with accordion piston, but I realise it is not available for everyone, so I started to develop a latex balloon version from this.
The frequency increased so much.
30--> 60+ Hz
The membranes tighteness and the mass on that is important to tune the frequency.
The engine works well and stable as possible with this low budget configuration.
If you want to build yours, please leave me a link bellow for your replications!
I'm pretty shure you heard the Ringbom as a type of the Stirling family,
but what that means single cylinder Ringbom or the Hybrid in the name?
First step first.
What is the real Ringbom type engine?
The ringbom Stirling engine has a free displacer with no connection rod to the crankshaft.
Ossian Ringbom patented in 1905.
When the pressure increase the rod lift up the displacer and the gas goes to the hot side.
It's push the power piston and the cycle started. When the pressure drop because the power piston moves to the other end via flywheel, the displacer's rod turn back and the whole gas goes to the cold side etc...etc...
That displacer rod works outside of the cylinder.
So the pressure on the outer side always 1 bar.
The configuration is Gamma.
They called it hybrid because the working method somewhere between the full kinematic
and the totally free Stirling engines.
But what about the single cylinder one?
It is a modern engine where the power piston works inline with the power piston.
Typically we call this Stirling configurations as Beta.
The sealed displacer moves on a thicker rod in the cylinder under the power piston.
Another configuration the displacer fixed on this rod and moves together,
usually across the power piston.
The modern people call it free piston Stirling engine
but the totally free psiton Stirling engines are essentially a constant frequency machine.
The displacer drive system (rod area and external spring) operate at resonance.
If the load change than the amplitude change but the frequency stable as possible.
With crank in a hybrid machine the piston amplitude is constant but the frequency is changeable.
The Ringboms could start in both directions with same speed.
The displacer piston's movement create a different mode in the Stirling cycle because the displacer moves with a flattened sinus wave.
It is called overdriven mode.
It means knok to the ends and still there a bit.
The speed of the engine deform the flattened curves near by the sinus wave.
So if the engine parameters are good enough the displacer piston could move near as possible sinusoidal as the power piston.
I haven't got too much space for the equations here, and those are complicated.
By the way the first single cylinder hybrid engine born around 1970 when it was rediscovered
by Walker and his colleagues
at the University of Calgary, William Beale, Jack Roberts and
John Kentfield
These are the old news, but today I want to show you a high speed one.
These guys works on a pretty low speed engine with overdiven mode.
I used some changes in the displacer.
I put in springs onto the ends.
I connected the power piston onto a flywheel with 7,5 mm from the center.
So the stroke was 15 mm.
The speed rich the 2100 RPM
Here it is the video about that simple glass syringe 'beta' hybrid 'Ringbom' engine:
Later I was boring with the flywheel so I change that for a rubber band.
Actually now it is a totally free piston Stirling engine.
NASA/Sunpower/Microgen are use this configuration.
Check this out!
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