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Post by tonyb on Feb 3, 2017 9:16:35 GMT
I seem to remember being taught that an explosion is just something burning ......... but rather quickly Absolutely correct but I think you will find that an explosion is defined by the speed the flame front propagates, as is burning. It is said that in a petrol engine we have uncontrollable burning (not so sure about diesel because the rate of injection will give some control) and uncontrollable burning has a slower flame propagation compared with an explosion. As I said we do get explosions in petrol engines when they detonate (pink) and the pinging sound is the shock waves hitting the metal of the engine. As you do not get this under normal running it follows that normally petrol engines do not have explosions in the cylinder - just very fast burning. Even so I do not think uncontrollable burning is a very helpful name for what is going on because during engine design great efforts are given to ensuing the fuel air mixture in petrol engines burns as the designers want while in diesels great efforts are taken to ensure the swirl in the cylinder/precombustion chamber are as required. So the burning is controlled to some degree by the engine design.
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Post by Deleted on Feb 3, 2017 9:30:15 GMT
Well they are not explosions. when a petrol engine suffers explosions in the cylinder it is called detonation and will eventually wreck the engine. I think it is impossible for a diesel engine running on diesel fuel to suffer explosions. The swirly should be even greater in a diesel. I suppose "explosions" is adequate for reader of the Mail but in reality the speed of the flame front is well short of that from an explosion and possibly slower in a diesel. Talking about Flame fronts, our 650cc enduro sidecar has a 101mm piston, it's a single cylinder two stroke - detonation was a nightmare if run on anything less than 99 octane fuel. The big Zabels were 700cc plus, absolutely on the limit of what was possible with high output piston ported two stroke singles. They make an incredible noise on full song though best i could find - not us i might add!
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Post by peterboat on Feb 3, 2017 10:13:19 GMT
Its cos they can rev unlike diesels petrol rules ok
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