Got my parts back from the flowbench/coater . . .
08-19-2004, 11:47 AM
#31
Re: but why...
As the exhaust gas passes through the turbo it goes from high pressure (EM) to low pressure (downpipe); this pressure drop causes a large gain in the volume of the air.
At this point you want the air to cool off by transferring its remaining heat to the atmosphere through the walls of the exhaust pipe. This causes the gas to shrink in volume and reduces the flow losses of exhaust system; thus reducing the backpressure on the turbine.
This effect is not overly dramatic on performance but determental nonetheless.
If you want to protect areas from downpipe heat this is best done with heat shields.
At this point you want the air to cool off by transferring its remaining heat to the atmosphere through the walls of the exhaust pipe. This causes the gas to shrink in volume and reduces the flow losses of exhaust system; thus reducing the backpressure on the turbine.
This effect is not overly dramatic on performance but determental nonetheless.
If you want to protect areas from downpipe heat this is best done with heat shields.
08-19-2004, 11:50 AM
#32
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i'm not a MechE nor an Aero, but i think when air cools it will flow FASTER
...(given the same environment (pipe))
since it should be more dense and take up less space.
Qcrazy, what is being physically represented by the temps in the power equation you quoted... ie what is the temperature differential there for?
perhaps it is representing IAC density? ...or more accurately the delta in density due solely to temp change?
since it should be more dense and take up less space.
Qcrazy, what is being physically represented by the temps in the power equation you quoted... ie what is the temperature differential there for?
perhaps it is representing IAC density? ...or more accurately the delta in density due solely to temp change?
08-19-2004, 12:02 PM
#35
Re: i'm not a MechE nor an Aero, but i think when air cools it will flow FASTER
The temperatures more or less represent the difference in pressures across the turbine.
In isentropic flow there's an equation that can be used that directly relates the pressures and the temperatures. It's not an overly complicated equation...just more so than I can easily type here.
In isentropic flow there's an equation that can be used that directly relates the pressures and the temperatures. It's not an overly complicated equation...just more so than I can easily type here.
08-19-2004, 12:06 PM
#37
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cool. and Cp? coeff. of pressure (making this up)?? your sig makes me thirsty...
maybe i just want a slushy? i also miss winter.
thanks for the info...
i took a few thermo classes during my BS.
thanks for the info...
i took a few thermo classes during my BS.
08-19-2004, 01:07 PM
#39
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Equation assumptions? Always the catch...
Shouldn't that equation only be valid over the span of the turbine itself? I can't see the turbo caring at all how the exhuast cools once it has left the turbo. Your T4 figure should be calculated before the exhaust even enters the downpipe imho.
Then, personally, I'd want to send that heat out the tailpipe rather than back into the engine bay.
If there was a benefit to cooling the exhuast after the turbine, the manufactures would put cooling fins cast into the housing.
If not, I'd happily learn something new today
Then, personally, I'd want to send that heat out the tailpipe rather than back into the engine bay.
If there was a benefit to cooling the exhuast after the turbine, the manufactures would put cooling fins cast into the housing.
If not, I'd happily learn something new today