Stirlingengineforum.com

Hello

I have did a lot of reading on hot air engines and I wanted to correspond with some persons with calculation and theory skills that could look at development drawings that I can transmit to them by email for advice,
starting out with the basic layout and building on that more detailed part drawings.
I have my own toolmaking business, cad drafting service and a vast array of equipment to use.
The design I am thinking of will be of modular design so I can pull it apart with ease and change the design of a section, so the engine will not be very compact.
The aim is to build the engine to burn sump oil which is legal to burn where I live.
I see many problems in the design but some of the solving I have seen so far seems to be limited to equipment, materials and amount work needed to achieve the end result.
The basic engine design would be 2 cylinder and have a bore size between 100 to 150 mm dia,
So any body want to help me with the theoretical side.
You can correspond with me via email or the forum.
Any body that helps me I will provide with a complete set of detailed drawings for their use but I would retain ownership of the finished design.

batt

Hi Batt.
Well, I am working on the V-twin compressor design stirling engine. Many people are following along, but I admit I don't have as much free time to develop it quickly. Burning oil would be most economical as a good heat source, and I have considered it for my engine, but will not be able to implement it at this stage, since soot is a major enemy. A clean burning fuel is a must, or a self cleaning heat exchanger would keep thermal efficiency high in such a system or even a molten salt system of heat delivery might be good, also.
Oh, and I suggest a short stroke with your design. 30mm-40mm would probably be about right, but I have no idea of what rpm you need to run at.

Batt, I think may be for you an important indication a done by Jimlarsen about a download possible of a book of Andy Ross, an important designer of SE, and original solutor for crankshaft mechanism.

Andy in his book (...dated), show the history of his design system, and relevant mistakes.
Andy is really genial for mechanical solution problems and, reading at fist step the book, seems a lot more less genial in thermal-thermodynamic phenomena and up scaling of engine.
But, by such honest and genuine close examination that Andy's self, is just to learn.
By, Ferraccio

jimlarsen wrote:Andy Ross recently started offering his book "Making Stirling Engines" as a free download. He has granted me permission to post links to his book on my website at
http://StirlingBuilder.com. Andy Ross is one of the leading Stirling engine designers of our time, and he loves to share his work so others can build and enjoy his well designed engines.

.....

The book to be downloaded is
Making Stirling Engines
by Andy Ross

Hello vile fly
Why do you recommend a short stroke ....
One of my ideas is to heat the cylinder along its length so a small dia with a long stroke would give a large heating surface and allow the air contained to be heated quikly and the same with cooling the other cylinder ...
The reason for using molten salt around the cylinder was to keep the heat very even over the whole cylinder.
The engine I am thinking about would be two cylinders side by side, double acting.
The piston rod ends of the heat cylinder would be insulated from heat by being water cooled on their ends, so that they could be sealed ... the same with the end caps ... both are extended for the cooling area to be away from the heat source and to allow as little heat to travel to the seal area there would only be an annular clearance of say .05 mm so as to keep to a minium the heat travelling to the sealing area.
The design for the piston ring assembly I have been thinking about would have spring loaded carbon segments, 2 rows consisting of 3 segments each which would be activated by a centre pin contained in the piston rod
and spring loaded which can be adjusted, this would be opposite end of crank.
This engine would not be compact as my prioriy would to be get the design working.
the piston rods would run in linear bearings ... the sliding end of the crank shaft would have its own linear slide block ... the piston rod would connect to the crank by contained washer plate contained by a housing on the crank sliding block so allowing it to be able to be misaligned radial but a minium clearance length wise.
Will no t be able to start on drawings for 2 weeks ... have to finish my web page first.
Batt

A short stroke is advocated to reduce friction, another thing is to have as greater length of connecting rod as possible, this reduces the angular thrust. The result is an increase in RPM.

Hello Batt,
I think you need to do some calculation, about exchange surfaces, before to do some drawings.
Normally are used stroke very short, and do not are used metallic sealing elements on pistons.
Some advanced engines use Rulon for sealing, however a process of honing and lapping 0,025 mm or less, do not need sealing, if are used some precautions
The way to increase the exchange surfaces is the finning, or pipes
On start from the smooth cylinder, like everyone else, for engines of small size, then, increasing the size of the cylinder can be finned externally, and then still finned internally as well.
The external fins increase the surface area of exchange between flame and metal, the inner surface increases the exchange between metal to the internal gas (air).

The external fins will not increase dead space, the inner rather increases it.
For larger engines I think that the tubes are inevitable.

The presence of a dead space is inevitable, ok to reduce it, but not too much emphasis on its importance, there are many other elements to reconcile, as said by Ian.
Ferraccio

Batt,
As said by Andy, the optimal combustion is a collateral question, that may be is addressed in parallel, and even later.
Not necessarily the combustion of exhausted mineral oil, produces soot or sludges.
Where I live, in a quite cold region -as is Cristhchurch-, a complex of (very large) three buildings (75 family apartments in total) is fully heated with a boiler that burns waste mineral and vegetal oils: combustion is absolutely perfect.
The question of a good combustion, using so different range of different fuels, is a separate problem.
Ferraccio (Sergio)

Ferraccio, do you mean "Christchurch", if you do the temperatures here on a few days during winter the temperature goes down to pehaps a little below minus 10 deg C, every few years (10 or so) we get a bit of snow and it gets a bit cooler for a few days, inthe summer the temperatures can go up to the mid 30 s, in general we have a temporate climate.
If I'm wronge forgive me, and you'v learned a bit about the climate in the South Island of New Zealand, Its proberbly not too different from the north of Italy. Ian S C