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Originally Posted by drmiller100
interesting engine.
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I agree.
But like any 'prototype' ... it will be years before it is available ... if it even makes it at all.
Right now the prototype has decent performance ... ~20HP from ~20 Lbs ~140cc engine ... I wish they would have published with the other SAE stuff the BSFC chart , not just an average efficiency ... I would have liked to see the efficiency distribution over different load and rpm ranges from a BSFC chart.
Although it is their first prototype ... so maybe more details in a year or two , as they make refinements and such.
Quote:
Originally Posted by drmiller100
I'm a little puzzled how they are going to "overexpand" down to atmospheric pressures, unless they leave the exhaust valve open on the compression stroke?
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near atmospheric is different than at atmospheric ... for example what do they mean by 'near'.
In this case the current prototype undergoing testing has a ~1.5 over expansion ratio ... meaning that the expansion ratio is about ~1.5x more than the compression ratio... this is how they get to those lower pressures ... how close they get to atmospheric will depend.
Remember this is a hybrid cycle engine ... in it's operation it combines elements of the Oto cycle , the Diesel cycle , the Atkinson cycle , and the Rankine cycle ... it tries to combine all 4 into one engine cycle that has the best net results... or at least that's the intent.
Quote:
Originally Posted by drmiller100
For that matter, they could run this thing as a 2 stroke with a separate combustion chamber.
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I'm not clear on what you are fore seeing here? Can you elaborate?