Stirling Engine Q&A Q51-Q100

Q&A from June 13, 1997 to April 19, 1998.

Q100: Excellent site, i like it very much. Other than a few mis-spellings it was very easy to understand. Don't know much about these engines, but plan on visting your site again.
19 April, 1998

A100: Thank you very mach.

A99: Sorry, I have not built the fluidyne or liquid piston Stirling engine yet. You can view the photos and figures in following web sites.

• Mr. Tsuchida's fluidyne engine page, Japan (in Japanese, but you can see his nice figures.)
• Mad Scientist's Lair, Australia

A98: I connected your web site. I seem that your Stirling engine is very beautiful. I would like to see the real engine, if I have a chance.

A97: It is difficult to help you for me. More 40 % efficiency is too high. I seem that you cannot fine such high performance engine.

A96: There are many kind of the beginner books. But, I recommend that you search the information on the internet.

A95: Yes, I had my mistake, and repaired it. Thanks.

A94: I think that one of the most important probrems for the low temperature difference Stirling engines is the heat exchangers with high heat transfer performance, as you said. When the heat exchangers with with high transfer performance are completed, the low temperature difference Stirling engine becomes small size and high engine speed. But I don't any good idea for the heat exchanger yet.
I think that the aluminum mesh is a good regenerator material, as you said. There are not a big probrem to locate in the displacer piston, because it is very light material.

    |--------|---------

  (--)     3 |        |

  |  |       |        |5

   ||----    |        |

 1 ||----  --|------/-| \

  |  |       |  ^   \---/4

  |  |     2 |  5    

1 these are the tin cans two coffy cans and a spray can
there are two beer cans inside the spray can
2 this is a post to support 3
3 this is a waking beam
4 this is a wooden fly wheel
5 these are the brass rods
the top coffey can is filled with water the bottom has an opening for an alcohol burner there is a tube coming off spray can which has another piston in it I have set the timing at 90 degrees and there is almost no friction what else could be wrong? by the way his does run.
20 March, 1998

A93: I think that your engine is very interesting, though I cannot understand the structure of the engine enoughly. I wonder that the performance of the seal device is no good. Is not there the gas leakage between the beer can and the splay can?

A92: I have not seen the ST-5, though I have heard about it. In my feeling, it is a very good performance engine. As my comments for the big engine, I think that the big engine is said the high performance, when the engine has one of the follows good characteristics.
(1) High efficiency,
(2) Use a low emission fuel with pollution-free,
(3) Compact size and high power.
I seem that the characteristic (2) is very good in the ST-5.

A91: In the case of the model Stirling engines, there are above methods for the throttle as you said. They have each advantages and defects shown in follows, so I can not decide the best way.
(1) Varying the phase angle; It can be constituted an easy mechanism with some gears as my proposal on my web site. But, this mechanism is not suitable for a high power engine, because there is a problem for strength of the gears.
(2) Varying the stroke; It has a high responce of the engine speed. But, the mechanism receives a too big load for varying the stroke. The mechanism needs any inventions in order to hold the load.
(3) Restricting the airflow; I think that this is no good.
On the other hand, the high power Stirling engine has used varying the engine pressure for th ethrottle. This has had good results, and I recommend this way is aoolyed for the model Stirling engine.

A90: It is difficult to answer for me in this session. When you calculate an engine performance with an isothermal model or Schmidt theory, you see it.
But 90 degrees may not be the best phase angle, when the performance of the heat exchangers are considered.

A89: I have not prepared the plans of ESE10 yet. But the basic constaruction of the engine is the same of LSE01. So, I recommend that you build the LSE01 first, and you reform the engine under your consideration.
Please find the syringes of 10mm diametaer. I think that you can get the glass syringes on the science goods shop which is selling test-tubes, flask and etc.

Now an idea for regenerators. Why not make small holes in the displacer piston and put steel shaving regenerators in these holes, rather than have a separate by-passing channel for the regenerator? It would decrease the weight of the piston as well.
12 February, 1998

A88: Thank you for your suggestions. I will try to reform my animations when I have enough time.
We have developed the Stirling engine which have the regenerator in the displacer piston. I think that such type engine has follows probrems.
(1) types of heater and cooler,
(2) connection between heater and displacer piston (cylinder).
If you are interested in the engine, please conatct HERE.
I am interested in the steel shaving regenerator. I would like to try it.

A87: I have heard that the biomass Stirling engines have been developed and used in Southeast Asia, though 100 % not sure information. Sorry, I don't know more detail information about them.
On the other hand, a 40 kW Stirling engine for wood chips has been developed in Technical University of Denmark. Its reference is;
H. Carlsen, J. Bovin: Field Test of 40 kW Stirling Engine for Wood Chips, 8th International Stirling Engine Conference and Exhibition, p.525-530.

A86: I think that the volume in the power piston can be included to the compression space, when we use an easy analysis method like an isothermal model. In detail, the volume in the power piston expands adiabaticly in the cycle, and decrease the gas temperature in the space. When we need to analyze the gas cycle in detail, the volume in the power piston must be considered as a separated space to the compression space.

A85: First of all, I don,t know the producer gas. I think that it is a kind of combustibility gas.
The theoritical efficiency of the Stirling engine, n is calculated by a next equation.
n=1-(Tc/Th)
Now, Th (Kelvin) is a temperature of hot heat source. And Tc (Kelvin) is a temperature of a cold sink.
If temperature of the combustion gas is 1200 K, and temperature of the cold side is 300 K, the theoritical efficiency becomes 75 %.
But there are many kind of thermal losses on the Stirling engine. Then a net efficiency of the high performance engine becomes about 20 - 30 %.

A84: Stirling engines can be cllasfyed two-piston-type and displacer-type. The two-piston-type equals the alpha-type generally. On the other hand, the displacer-type can be cllasfyed the beta-type and the gamma-type. On the beta-type, the displacer piston and the power piston are located in a single cylinder. On the gamma-type, these pistons are separated cylinders.

A83: You are welcome. I am happy if my web site is useful for you.

A82: Sorry, I cannot answer your request soon.
Have you connected to Ecoboy-SCM81 page?
There are some information of a practical Stirling engine, though it is not enough.

A81: You must decrease the gas leakage and the friction loss of the Can engine. Please make sure following points.
(1) Is the hole of the balloon too big?
(2) Have you putting on a drop of oil to the hole?
(3) Can the crank shaft work smoothly?
(4) Are holes of the frame and the connecting rods too small?
(5) Does not the mass weight touch the frame?
(6) Does not the displacer piston contact to the cylinder?
(7) Please adjust the weight in detail.

A80: I am veru happy that my web site was useful for you and your students.
Sorry, I cannot answer your request soon. Almost of my information of model Stirling engines are shown on my web site already. I will inform you the requested information on the web site, when I prepare it.

A79: If your engine has a small friction loss, next causes are considered.
(1) Large gas leakage.
The seal device between the piston and cylinder needs high quality.
(2) Small temperature difference.
In the case of the engine which the distance between the high and low temperature space is too short, the low temperature increase too high. Then the engine cannot work.

A78: You can decide the volume freely. But you must consider the capacity of heat exchangers. Please see Q6 and A6.

A77: You need to use Hot temperature, cold temperature, minimum volume and maximum volume, maybe.

A76: I have not build the steam engine yet. And I don't know the steam engine well. In my opinion, the maximum highest temperature of such 1000 watt class Stirling engine is very higher than that of the 5hp steam engine. So, nickel steel like stainless steel is needed as the heater material. If you can use welding work for the steel, you can build the large scale Stirling engine (in the very long process).
Sorry, my answer is not enough.

A75: I don't know if the 1-10kW Stirling engine is selling now. Follows comanies have been developping the engines. Please contact them.
(1) Stirling Thermal Mortors, Inc., USA
(2) TEM Stirling engines, Sweden
(3) Sigma Elektroteknisk A.S, Norway
(4) Whisper Gen, New Zealand

A74: I am happy that I accepted your hot message. I hope that you build the 'ambitious' Stirling engine.
I seem your failure will be useful for me and other Stirling developers.
I don't know about the brazing furnace. If someone know about it, please contact him or me.

A73: I seem it very interesting idea. I think that the Stirling engine can work using the temperature difference between the hot room and the cold air, as you said. In my opinion, it is difficult that the engine gets an effective power using such low temperature difference.

A72: Please contact to the link page on my web site. I have informed about many model and commercial companies.
The Stirling engine can work using the solar or spring water. I hope that the engine is developed using such natural energy in near future.
I sure that the practical engine for the generator is developed soon.

A71: You are welcome. Your information is very useful for me and other persons who will build the model Stirling engine. Thank you.

A70: My drawings are no good, then you may misunderstand the structure of the rotary displacer type engine. The minimum clearance of the real engine between the displacer and the power piston is 0.5 mm. Also, the flywheel does not have any holes. The holes, you said are located between the displacer space and the power piston space, maybe.

A69: Sorry, I cannot understand this question.

A68: Thank you for your veri interesting information. I cannot compare the Can Stirling engine and the Tailor engine, because I don't know the Tailor engine at all. The Can engine is able to run about 60 rpm.

A67: I think that you can use the metal piston and cylinder, when the piston is not too hot temperature. If so, I recommend that Teflon material is used as its piston rings. Generally, an expansion piston of the two piston alpha type Stirling engine is located near the heater. But it is not good for the piston seal, it lead to a lot of friction loss or much gas leakage. When the metal piston is used, the displacer type engine is better. Because the piston seal of the displacer piston does not need few gas leakage.

A66: It is difficult to answer this question for me. I cannot answer soon, sorry.

A65: Recentry, I don't know what company is developing the Stirling engines for the cogeneration. A few years ago, several companies had developed the engine for such application in Japan. But I don't know that they have been developing it now.

A64: I have heard that the Stirling engine using the steam as the working fluid was developed. The power of the engine was increased. But, I seem that it is difficult to keep the steam in the engine. Also, I wonder that the pressure loss in th eheat exchanger is increased.

A63: It is difficult to answer this question. I am one of the Stirling enthusiasts, then I believe the Stirling engine will be used on the world wide in near future.

A62: I am very happy that I can hear your message. I hope that your engine will be pleased your family and friends.

A61: Sorry, I don't know about the markets in detail. I cannot answer this question well.

A60: Thank you for your information. I would like to descrive suce philosophy(?) related the Stirling technology.

A59:
(1) Your cylinder does not cause any problem. Please make sure that the displacer piston does not contact to the cylinder, and keep the clearance between the displacer piston and the cylinder to about 3~5 mm.
(2) The mass must be located to opposite of the engine stopping position. ( Sorry, I cannot explain well.)

A58:
(1) The piston ring of the Stirling engine is used 3-piece-type or 4-piece-type generally. The material is Teflon based. They are high seal performance thatn that of the internal combustion engines.
(2) As you said, the torque of the pressurized engine is large. But I think that it is not a big problem, because the compression ratio of the Stirling engine is very lower than that of the internal combustion engine.

A57: I don't have any information about the table. Please contact him or me, if anyone have the information.

A56: Yes, I do. I have seen the test tube engine and it is veru interesting. There is more information on a following web site.
Omniscience Futureneering

A55: It is difficult to answer this question. The displacer must be light weight. On the low temperature Stirling engine of Saitama university, the material of the displacer is polyurethane. The regenerator material is piled mesh made by brass. I think that more beter regenerator material is found after more consideration.

A54: Thank you for your suggestion. I will find my error and reform it.

A53: I don't know about the marble engine. Sorry.

A52: The Stirling engine and the steam engine are the same internal combustion engine. But they are diffrent type engines at all. The Stirling engine has no valves, and is a closed cycle. The steam engine has some valves, and is a open cycle.

A51: I cannot understand a construction of the Bomin's HEATPULSE enough. I think that it is a free piston or liquid piston type engine. If so, it is possible to "self starting", maybe. In my opinion, the engine with the self starting mechanism cannot keep a high engine speed. Because the engine must have a low compression.
Thanks again for your information of the papers of IECEC. I will be able to get the papers, though I need enough time.

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