Ratio b/t displacer and power piston

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Ratio b/t displacer and power piston

Postby depasha » Tue Sep 03, 2013 9:32 am

Hi i am new in this forum
can anyone suggest me .if swept volume ratio b/t displacer is =2.7 of powerpiston then its effect the efficiency of stirling engine
sorry for bad english
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Re: Ratio b/t displacer and power piston

Postby Ian S C » Wed Sep 04, 2013 1:55 am

depasha, the 2.7:1 ratio would be OK for a motor running on a medium temperature as a tin can motor does, for a low temperature motor, the ratio might be anywhere from 10:1, to 20:1. A high temperature motor should be around 1.5:1, unless it's an ALPHA motor, in which case the ratio is 1:1. Ian S C
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Re: Ratio b/t displacer and power piston

Postby depasha » Wed Sep 04, 2013 12:36 pm

thanks Ian SC
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Re: Ratio b/t displacer and power piston

Postby Osama » Thu Sep 05, 2013 1:38 am

Hey Ian!

We are using a solar parabolic dish and have achieved a temperature of 250 degree Centigrade for the hot end. Can you please suggest what swept volume ratio should we use and what should be the size of the displacer and power piston?

Osama
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Re: Ratio b/t displacer and power piston

Postby Ian S C » Thu Sep 05, 2013 5:06 am

I can tell you about one of my motors, it's in my gallery as "my second engine", its based on James G. Rizzo's Dyna, from his book "The Stirling Engine Manual". With gas/LPG it has developed 5 Watts, and using a large freznel lens (made for magnifying a TV set), about 5.5 Watts, this BETA motor has a bore of 1 3/4", a power piston stroke of 3/4", and a displacer stroke of 1 3/16", best speed for power 600 to 700 rpm, and it has exceded 2000 rpm, it has done well over 2000 hours. It will produce about 2.5 to 3 Watts at 12Volts on the generator, enough to power a cooling fan on the radiator, and a transistor radio, or a power hacksaw, the one that is fitted to my Ross Yoke engine in the gallery.
An estimate of power can be about 1 watt per cc (I think, or was it per cu inch), what ever, it's probably optimistic. Ian S C
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Re: Ratio b/t displacer and power piston

Postby Osama » Fri Sep 06, 2013 6:27 am

I am building a gamma stirling engine and was considering using a 100 cc displacer cylinder an a 70 cc power piston. But that is just an assumption. I have no clue how to decide the volume of the displacer and power piston cylinders. So any help would be appreciated
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Re: Ratio b/t displacer and power piston

Postby Ian S C » Fri Sep 06, 2013 7:20 pm

You would have to subtract the volume of the displacer from the cylinder to find the displacer side volume. them that should be 1.5 times the swept volume of the power cylinder. Ian S C
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Re: Ratio b/t displacer and power piston

Postby depasha » Sat Sep 07, 2013 3:29 am

hi Ian sc
tell me about some parameter about engine when we calculate the ratio of powerpiston and displacer so either diameter of displacer or bore of displacer cylinder take into calculation.
thanks in advance.
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Re: Ratio b/t displacer and power piston

Postby Ian S C » Sat Sep 07, 2013 4:38 am

If for example the power cylinder has a swept volume of 10 cc, the displacer cylinder should have a volume of 15 cc. A reasonably designed solar system will, on a sunny day, give you more heat than LPG gas, so it does depend on which part of the world you live in. I live in New Zealand which is mostly just north of 45* South, it's better that you are either north of this, or south of 45* north for best running, if you adjust things to suit, most places are ok, some places if you are generating power, you may need a larger battery bank to cover the non charging times, you just have to try it and see what happens. Ian S C
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Re: Ratio b/t displacer and power piston

Postby depasha » Thu Sep 12, 2013 3:37 am

hi Ian
tell me about what the area required for the passage of air move between the powerpiston cylinder and displacer cylinder
my engine parameters are displacer cylinder dia=61mm
piston cylinder dia =42mm
my some experiance is that if area of passage of air is small so the powerpiston move to and fro hardly .
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Re: Ratio b/t displacer and power piston

Postby Ian S C » Fri Sep 13, 2013 3:23 am

See your other thread. Ian S C
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