Forced induction (was variable (non variable) whatever...)

[Joe Boucher]

I haven't followed this thread, but allow one mech eng to backup another mech eng.
The gas also looses pressure as it expands through the turbine.  For an x amount of
atoms to have less pressure they must occupy more space.  The gases also cool while
they spin the turbine but the pressure loss is the greater effect.  Look at the
return line versus the pressure line of a refrigeration system.  The return line is
always bigger even though the return gases are cooler than the pressure gases. The
pressure is much lower at that point.

Another way to look at the situation.  If you drew an imaginary line at the inlet
and outlet of the turbine and counted the molecules as they flowed past these
lines, the amounts would be the same (mass flow in equals mass flow out).  But the
velocities are different.   The inlet is much faster.  The internal energy (heat
energy) of the molecules is used to spin the turbine so the internal energy of the
molecules is lower at the exit. The volume occupied by the gas is expanded as part
of the process to convert the gas heat energy to spin the turbine.  The velocity is
slower.  Therefore, the crossection of the exit pipe must be larger to flow the
same amount.

Joe (I don't understand hole and electron flow) Boucher

'70 RS/SS Camaro  '81 TBI Suburban

Darryl Snover wrote:

> Hmmm....But doesn't (don't) gases contract as they cool, thus making the
> actual volume less (and thus making Mikes statement more or less true)?
>
> >  This cannot be correct by your own explanation.  The mass flow of
> >exhaust is the same whether at the beginning of the exhaust system or the
> >end.  Mass doesn't disappear when the energy it contains is removed >from
> >the exhaust, it simply comes out the other side of the turbine in a denser
> >package.  Yes, more energy is present when there is more gas(ie higher
> >mass flow), and thus a higher flow rate, but is worthless without the heat
> >transfer(ie expanding the gas).
> >
> >Pete Datcuk
> >Mechanical Engineer
> >Sewell, NJ
> >'87 Fiero, soon to be Northstar'ed :-)
> >'67 Jeep Commando, to be risen from the dead ;-)
> >
> >
> >-----Original Message-----
> >From:  Nimpoc at aol.com
> >Sent:  Tuesday, February 24, 1998 1:35 PM
> >To:    diy_efi at esl.eng.ohio-state.edu
> >Subject:       Forced induction (was variable (non variable) whatever...)
> ><snip>
> >Turbines derive their power from the mass flow of the exhaust, not just the
> >heat nor the pressure. Some also claim they can derive power from the acoustic
> >energy present... don't know about that. Sure a turbine won't make as much
> >power at the end of the exhaust than at the manifold, look at how much volume
> >is lost due to temp.
> ><snip>
> >Mike Kent
>
> Best Regards,
>
> Darryl Snover
> Senior Programmer
> Technologies Plus, Inc.