Dan_s_young

iTrader: (1)

Hey,
Im in college to be a Automotive service tech.... We are currently covering the design of piston engines and everything about them.

My question is why is it that the rotary does not create vibrations from the 2 spark plug in one combustion chamber design? We learned that 2 flame fronts meeting each other ie preignition or detonation causes alot of vibration. So with the rotary engine there will be 2 flame fronts contacting will there not?

I understand there is 2 plugs for emissions purposes but I am curious as to why there is no vibrations from this?

Thanks
Dan_s_young

Project84

I'm sure there is some vibration but the two sparks occur 15 degree (crank rotation) apart, which is not that much. Im not sure if this would make a difference as compared to two sparks occuring at the same time and moving toward each other at an even rate. I'm not an engineer but I know that the rotary engine doesn't create the same mechanical vibration as piston engines because it doesn't have parts that stop and change directions the way pistons move back and forth.

Go to www.rotaryrefs.net and on the left, click on Misc Rotary Books and info. On the next page yo go to you will see "Rotary Engine" by Kenichi Yamamoto. Its old, but it has a lot of good and very detailed info on the principles and functions of the rotary engine. Its a PDF file and you can download it for free.

Hope that helps a little.

Carzy Driver

This may help you understand the rotary alittle bit better.

http://www.rotaryengineillustrated.com/animations.php

pmrobert

This is a somewhat complex subject. It's the abnormally rapid combusion of the AF mix that causes the knock, not necessarily just two flame fronts. Multiple flame fronts do exist in a preigniting or detonating engine but these are of abnormal origin and are characterized by an abnormally rapid burn rate - an excessively hot exhaust valve in the preignition case or chamber pressure too high for the octane fuel you're using in the detonation case among numerous other things. You can fire a normal pressure, normal temp chamber with multiple plugs and not have knock; rotaries, most aircraft piston engines, etc., do this routinely - the 26B (4 rotor LeMans racer of the early 1990s) fired 3 plugs per chamber. The rotary has a long, narrow, shallow combustion chamber that is not conducive to a fast burn; that's one reason to use multiple plugs, there were other reasons as well. See http://smrmicro.com/re-ky.pdf and http://smrmicro.com/re2.pdf ; there are sections in each of those that specifically discuss number and placement of plugs. Preignition and detonation are two different phenomenon, related but with different causes and cures, as you allude to above. See http://www.dynopower.freeserve.co.uk...reignition.htm
for a little history and technical description of what's involved.
HTH - Mike