Valve timing

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gallanach
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Valve timing

Post by gallanach » Sat Mar 31, 2018 3:53 pm

I am doing some work on my 10hp LIFU compound engine, running the low pressure cylinder as a single on air results in very lumpy running, on measuring I find that the piston valve is closing 20 degrees before TDC and BDC. I realise that some cushioning is a good idea but what is the recommended amount?

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Nigel
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dampfspieler
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Re: Valve timing

Post by dampfspieler » Sun Apr 01, 2018 6:50 am

Hi Nigel,

to test a steam engine with compressed air to find out how it works is a very bad idea and practice because air and steam are very different "in expansion". There are also a lot of differences in materials at air and steam-temperatures. I think the angels are right.
By testing with compressed air you can only check its free running. The only successful way to find out how it works is to test the engine with steam.

The asked angel you can only change by redesigning the geometry of the slide and the eccenter.

Regards Dietrich
Lionel Connell
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Re: Valve timing

Post by Lionel Connell » Mon Apr 02, 2018 1:40 am

I realise that some cushioning is a good idea but what is the recommended amount?
The idea is to compress the remaining steam in the cylinder up to near the pressure of the inlet steam. To calculate this one needs to compare the swept cylinder volume with the unswept volume. The unswept volume is the space that is left at the top of the cylinder when the the piston is fully up plus the volume of the steam port between the cylinder and the valve face. Every engine is different, but 20Deg BTDC is not out of the ballpark.

Lionel
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