Comments for Solar Heat Engines

Comment on Stirling Engine Simulator & Guide by James

James — Sat, 04 Sep 2010 06:11:51 +0000

you say that keep the pressure ratio less than or equal to the temperature ratio for successful stirling engine. What do you know that? and Can you tell me about theory or all of equation or something else that you use to make stirling engine simulator? The thing is,I want to design beta type stirling engine but I’m not assured of my desing that it can be success. I’m waiting for your reply.Thank you very much. You can send file to my e-mail.

Comment on Stirling Engine Simulator & Guide by admin

admin — Mon, 16 Aug 2010 16:36:52 +0000

The temperature ratio is the ratio of two temperatures measured on an absolute temperature scale (either degrees Kelvin or degrees Rankine). When I compute the temperature ratio in the simulator it will be T(hot)/T(cold).

Dead volumes are those volumes that are not swept by either the displacer or the power piston. The hot dead volume normally only occurs at the hot end of the displacer cylinder where there is some clearance to keep the displacer from striking the end of the cylinder. The cold dead volume is the same at the cold end plus any dead volume connecting the cold end of the displacer to the power cylinder. The cold dead volume would also include any clearance between the top of the power piston and the end of the power cylinder when the piston is at its extreme compression position.

Comment on Stirling Engine Simulator & Guide by James

James — Mon, 16 Aug 2010 15:16:31 +0000

I would like to ask you questions as follows;
- what is equation to be found the temperature ratio?
- what is the position of dead volume(hot and cold)?(Could you please present by picture?)

It is really important for my education. I would appreciate your urgent response.Thank you very much.

Comment on Engine 3F Efficiency Analysis part 4 by admin

admin — Mon, 26 Jul 2010 21:46:05 +0000

Thank you for your comments SP. You are correct that the internal energy change over a complete cycle is zero. In the last sentence of (2) I describe summing all the steps where heating takes place (as opposed to cooling). I’ve now emphasized it to avoid confusion.

The equation for internal energy U2-U1 = mCv(T2-T1) is valid regardless of whether the process is constant volume or not. If the process is constant volume, then there is only an internal energy change. If the process is not constant volume, then there will be PdV work involved in addition to the internal energy change. Due to your comment I realized I could include this amount (about a 7% change) and make the analysis more accurate. This is the reason for Rev 1.

The equation in the last part of your comment isn’t familiar and I haven’t figured out the derivation yet. Real engines add dead volume, don’t have constant volume heating and cooling, and don’t have isothermal compression and expansion. These changes get you pretty far from an ideal Stirling engine.

Comment on Engine 3F Efficiency Analysis part 4 by SP

SP — Mon, 26 Jul 2010 09:43:39 +0000

A very interesting and detailed analysis!
Although, I have a doubt regarding the way you calculate Q_required. Isn’t it inaccurate to talk of internal energy chance in a cycle as equal to the heat supplied into the cycle? delta_U (change in int. energy) for the cycle is zero isn’t it?

What you have done here seems to be for a constant volume process if I understand correctly?

Also, what do you think about the approach of comparing your ‘real stirling’ cycle with the ideal one by saying that Q_required_ideal is given by m*R*T_hot*ln(vol_ratio) ?

Thanks

Comment on Measuring a Stirling engine with 1 watt power output and 1.5% efficiency by Olle Welin

Olle Welin — Wed, 21 Jul 2010 08:28:13 +0000

Nice work.
I have made similar efficiancy test on my water pump stirling engine.
See: “Stirling engine water pump efficiency test 1.51W” on youtube at:
http://www.youtube.com/watch?v=3_65JfvC2qg&feature=related

I reach 2.05% efficiency and 1.94Watt at +133Celcius.
See the working princip animation at:
http://www.youtube.com/watch?v=W2Bbht7O2Hc&feature=related
Best Regards
Olle Welin
olle_welin@hotmail.com

Comment on Engine 3F Efficiency Analysis part 1 by admin

admin — Mon, 19 Jul 2010 20:31:20 +0000

Ryan, I don’t know if the linkage has a formal name. I think of it as quadrature phase linkage. A single crank drives two linkages that are 90 degrees apart. One link drives the long lever that drives the power piston. The other link drives an arm fixed on the shaft that the first lever rotates on. The shaft is also rigidly attached to the second long lever (counterbalanced) that drives the displacer. Let me know if this isn’t clear–I’ll put up a drawing.

Comment on Engine 3F Efficiency Analysis part 1 by ryan

ryan — Mon, 19 Jul 2010 18:24:22 +0000

Is there a name for the type of linkage you’re using? I can’t quite figure out how it works from the pictures.

Comment on Engine 3F Efficiency Analysis part 3 by ryan

ryan — Mon, 19 Jul 2010 18:20:40 +0000

I’m loving this analysis. Looking forward to your analysis of cycle losses and especially regenerator losses.

Comment on Stirling Engine Simulator & Guide by Solar Heat Engines » Blog Archive » Engine 3F Efficiency Analysis part 3

Wed, 07 Jul 2010 18:13:37 +0000

[...] Tc. Using these values yields the first computed row in the table below. This simulator makes some idealized assumptions that make it virtually impossible for the real engine to output more power than the simulator. I [...]