Quote:
Originally Posted by bpestilence
No it doesn't. A difference in pressure is what makes a turbine, any turbine, spin. If you were to pipe high pressure, cold air into a turbo it would still work. Divided housing turbines have been around in large turbos for a long time, and they do work well. By dividing the runners you maintain a smaller, higher pressure area on the turbine wheel to do more efficient work. This is also why higher compression engines spool turbos faster.
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The exhaust heat is resonsible for most of the kinetic energy that drives the turbine/rotating assembly in a turbocharger. This is becasue there is a large temperature drop across the turbo and this equates to a large pressure drop across the turbocharger. You can think of it as the opposite of what is happening in the compressor, the air is compressed and it heats up. Now the exhasut veolocity does of course contribute to the kinetic energy, but as I said before the mojority of this energy comes from the exhasut temperature drop. This is one of the reasons why you cermaic coat or wrap your exhasut manifold, to keep the exhasut as hot as possible when it enters the turbocharger.
Now as far as getting the turbo spinning with high pressure shop air, I'm not sure if you could get it upto proper operating speed, but you would not want too, becaue the temperature drop would cause the moisture in the shop air to freeze out and wreck the turbine wheel or freeze the turbine wheel to the housing, which is not good.
At school, in my senior design project, we test turbocharger bearings and we also are designing a test stand to test the turbocharger with compressed shop air. The hardest part of this was to see what tempearture we needed to get the air upto before it entered the turbine.
Bill