New high power stirling engine design.

[Josephkaisner]

Hi! I have been interested in stirling engines for over a year.
Right now I'm designing a small high power engine. I would like some input on my ideas; I do not have any (many) specifications yet. Here are some new additions that I have come up with that I have not seen on any other engines:

Some kind of heating coil (maybe just stainless steal tubing) surrounding the hot cylinder (I'm alpha here!).
A finned AND water jacketed cold cylinder.
One thought that I had is: Dead space doesn't mater if it is being used to help generate a massive temp diff. Is this idea correct?

My engine would be pressurized to around 110 psi. It would be an automatic pressurization system.

Another thought: many small cylinders will provide more power and higher rpms than a few (one) large cylinder(s). I think this because: smaller cylinders will heat and cool more rapidly than a large cylinder.

My cylinder configuration will be: v6 alph (meaning: six hot and cold cylinder sets).

Joseph Kaisner

[Josephkaisner]

i am 13. so any advice is extremely appreciated!

[Ian S C]

Joseph,One power cylinder per displacer is best, if you start using multiple cylinders per displacer, you introduce more friction, and friction is the biggest killer of Stirling Engines. A pressurised engine would require heating to a reasonably high temperature, 600*C +, a dull red on a stainless steel hot cap, so the best heating is usually LPG or similar gas, or a pressure burner with Kerosene/Parafin. For the type of motor you are proposing you will need a machine shop, and a TIG welder would be handy.
My ALPHA motor is of the Ross Yoke type, unpressurised, and without a regenerator, the cold cylinder, and the bottom of the hot cylinder have a water jacket, but I don't use it, the motor will run all day on a gas flame, and not over heat. Here's a photo of it driving a power hacksaw with a Junior Hacksaw blade, it does work, but with 5 Watts of power it takes a long time to cut a steel bar.
Ian S C
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[Josephkaisner]

Ian,
Thanks so much! I chose Lp because here in Illinois, a gallon costs $.99. LPG is going to be more expensive. Do you have Amy thoughts about my theories?
I'm sorry for a lack of clarity about the cylinders: what I meant was that one cold cylinder would be connected to one displacer cylinder. There would be six sets of that configuration. Another idea about the coils - I do not like having the hot cylinder heated directly, this would cause enormous expansion and contraction on the part of the piston - if my dead space theory is right, then: a heating coil separate from the hot cylinder would lower friction, increase power, and heating surface. I really dislike the cylinder v idea because I feel like it massively increases the friction in the horizontal cylinder. I believe, if my dead space theory is correct: both Pistons could be vertical; employing the coil heater separately from the hot cylinder, no heat would be directly applied to the hot cylinder. Btw I have access to any almost machine tool.

Joseph Kaisner

[Josephkaisner]

I am a sort of "atv mechanic" so I think in terms of a crankshaft rather than a yoke. If I use a crank shaft I will use eccentrics instead of machining cranks. My problem with that is how to keep the eccentrics from fretting on the shaft?

Joseph Kaisner

[Josephkaisner]

Your engine looks awesome please send me a video of it.

[PlaniTechic]

Joseph,
Regarding your V6 plan (what I think would be really cool), I would suggest that you start with a one cylinder engine first. Once you get that one to run the way you want it and get all bugs sorted out make a 6 Cylinder version of it to get more power.

Plani

[Josephkaisner]

Thanks Plani,

My idea was to make (because it will use sets of two pistons) multiple cylinder units that can be bolted together. Because I'm part farmer I want everything to be EASY for the operator. I can understand why people leave stirling engines alone. They r so complex! Current models I mean, the stirling engine's commercial value is in a machine developed to the point of contemporary IC engines.

[Ian S C]

First, find and down load Andy Ross's book "Making Stirling Engines", there is about 60 pages, no plans, lots of information, and it's free.
Next, if you don't put much heat (energy) into the motor, you can't get much energy out of it, a low temp motor that is going to give any power is going to be very large, there is one study (when I last looked it was incomplete), on "high power" LTD motors from the Canterbury University New Zealand (a major centre for the study of Stirling Engines).
I think you idea of eccentrics instead of conventional cranks will introduce more friction (the last thing you want.
Lucky you only paying $.99 for LPG, last time I filled my 5Kg cylinder it cost $NZ 17.00/about $US 15.00. **** sorry no vidios ****
The main advantage of the Ross Yoke is that there is virtually no side thrust on the piston, It can be used in an ALPHA motor, with an equal yoke, or on a GAMA motor with an asymmetric yoke.
Please build a small conventional Stirling Engine (even a kit)so that you under stand it's working in practice.
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This is the Ross Yoke motor with the seal cover removed (normal running at atmospheric pressure) with a generator attached instead of the hacksaw.
Ian S C

[Josephkaisner]

Thanks for all the advice! I'll do what you both suggested. I have read Andy Ross's book as well as some by James Rizzo and Roy Darlington also Carroll smith. please tell me what u think about my thoeries.

Joseph Kaisner

[Ian S C]

By the way Joseph, the Ross Yoke motor does actually use a crankshaft, The apex of the yoke is on the crank pin.
If you have read Andy's book you will understand that quite a small pressurized motor, with a well designed burner can develop quite a bit of power, enough to power a bike (well get it to move).
As far as heating from SS tube wrapped around the hot cap, you could heat it with molten sodium salts (the same system in reverse to the cooling system in aircraft engine exhaust valves [Prat & Whitney R- 1830]), but direct heating would be more efficient. Designing an improved Stirling Engine is an exercise in advanced thermodynamics.
Ian S C

[Josephkaisner]

If you have sketchup I will post my first drafts for a basic alpha engine.

[Ian S C]

Joseph, I do 99% of my sketching in my head, then just get cutting metal. First of course you must fully understand the workings of the engine you want to build.
You do understand the difference between a Stirling Engine, and an ALPHA type hot air Engine?
Ian S C

[Josephkaisner]

Ian,

To answer your first thought, i have come up with my plans ( and most of the specifications ) in my head. The machine tools i can use are mostly computer operated. So some degree of a CAD is required. From what i have read, the difference between the stirling and alpha engines is that the stirling engine has its displacer loose fitting and in close proximity to the power piston. The alpha on the other hand, has, essentially two power pistons. Booth have a good seal in their own cylinders.

[Ian S C]

Yes you got that right. In the ALPHA motor the hot piston has a light weight piece similar in construction to a displacer on top of the hot piston, this is the Heylandt Crown, and at TDC this extends into the hot cap, it also protects the top of the piston from direct heat.
With the BETA motor the displacer, and power piston can come within a mm of each other in some motors, where as in the GAMMA motor the displacer, and power piston are in separate cylinders, and may be an inch or two apart.
As far as CAD is concerned, "that's your problem", sorry I'm just not into computer drafting and machining.
Ian S C