- #1
Physics_Kid
- 173
- 11
i have a question about a turbocharger (air compressor).
a turbo's function is to compress the exit air so that more air can fill the cylinders. let me give an example which will help setup my question:
XYZ motor pumps 10000cfm normally aspirated (1ATM) at max power (lets says 6500 rpm). to double max power the motor needs to combust twice the fuel along with twice the air, so we need to process 20000cfm @1ATM at 6500 rpm. so we need a compressor and the turbo will do that for us and we need 2ATM on the turbo exit to get 2x(na) into the motor.
so my question is, if i stick a flow meter on the inlet and exit of the turbo and run the turbo at 2ATM (aka 2PR or +14.7psi boost) do the flow meters read the same value (given area of inlet and exit tubing is equal). my initial thoughts are no, but some others are saying flow is the same. for a liquid pump i see flow rate is preserved because of incompressible fluid, but the turbo compresses the gas.
i said no because the turbo exit is attached to the inlet of another pump which has fixed physical pumping volume at 6500 rpm (and the compressor itself needs to have mass air preservation across the compressor, mass air(in) = mass air(out)). the turbo has to suck in 20000cfm (2x the NA motor) and compress that air 2x (2ATM) on the exit side. this equates to 2x(na) mass air exiting the turbo. i mentioned "mass air" but I'm only asking about volume rates.
so does P1V1=P2V2 hold true for the turbo where constant P1=1ATM(turbo inlet), V1=Xcfm, constant P2=2*P1, and V2=Ycfm. so if the motor can pump 10000cfm(@6500rpm) i need to fill that same space with a gas that has been compressed 2ATM, doubling the mass air being pumped into the motor. so does 20000cfm @1ATM = 10000cfm @2ATM ?
i may be wrong, just need a explanation.
thanks.
a turbo's function is to compress the exit air so that more air can fill the cylinders. let me give an example which will help setup my question:
XYZ motor pumps 10000cfm normally aspirated (1ATM) at max power (lets says 6500 rpm). to double max power the motor needs to combust twice the fuel along with twice the air, so we need to process 20000cfm @1ATM at 6500 rpm. so we need a compressor and the turbo will do that for us and we need 2ATM on the turbo exit to get 2x(na) into the motor.
so my question is, if i stick a flow meter on the inlet and exit of the turbo and run the turbo at 2ATM (aka 2PR or +14.7psi boost) do the flow meters read the same value (given area of inlet and exit tubing is equal). my initial thoughts are no, but some others are saying flow is the same. for a liquid pump i see flow rate is preserved because of incompressible fluid, but the turbo compresses the gas.
i said no because the turbo exit is attached to the inlet of another pump which has fixed physical pumping volume at 6500 rpm (and the compressor itself needs to have mass air preservation across the compressor, mass air(in) = mass air(out)). the turbo has to suck in 20000cfm (2x the NA motor) and compress that air 2x (2ATM) on the exit side. this equates to 2x(na) mass air exiting the turbo. i mentioned "mass air" but I'm only asking about volume rates.
so does P1V1=P2V2 hold true for the turbo where constant P1=1ATM(turbo inlet), V1=Xcfm, constant P2=2*P1, and V2=Ycfm. so if the motor can pump 10000cfm(@6500rpm) i need to fill that same space with a gas that has been compressed 2ATM, doubling the mass air being pumped into the motor. so does 20000cfm @1ATM = 10000cfm @2ATM ?
i may be wrong, just need a explanation.
thanks.
Last edited: