Part II
In any system we are always talking about managing energy for our greatest
benefit. So it is important to consider if our CONSUMPTION of energy is
being put to a greater benefit. I am greatly simplifying things here so I
can see things clearly. It has already been mentioned about parasitic losses
(bearings), and there are also pumping losses. Many things come into play
that can tilt the energy equation negatively but they are not considered
here so as not to confuse the principals.
As mentioned the piston does most of the work exhausting the mix. However,
such is not the case for ingesting the air/fuel. All the piston can do is
create a depression or a lower delta P and atmospheric pressure is
responsible for pushing (filling) the cylinder volume. We all know that
volumetric efficiency (VE) is LESS than 100% except in highly developed
systems. So anything you can do to increase VE is an improvement. Contrast
this to the exhaust side of things where the piston ALWAYS gives 100%
volumetric exhaust. (We are talking about the volume of the cylinder only,
not the combustion chamber or the port).
So how does all this balance out. The turbo and your ES all take horsepower
used to drive the compressor. The turbo is an exhaust driven air compressor.
Not much different from your garage compressor. If you want to compress (or
store energy) it takes HP to do it. The turbo is consuming HP but it is
returning it in spades by creating a denser (thanks Dave) intake mix.
Remember, anything you can do to pressurize the intake will INCREASE
CYLINDER FILLING and that is where HP is made. The more HP available to the
turbo the greater it can compress the intake mix. That is a winner and you
don't want to do anything to subtract from the turbine-driving-HP. There is
only so much HP in the exhaust flow. Let's say it is 50 hp. All of that can
be used to compress the mix. However, if you want to use 30% of that hot gas
HP to drive your ES, you will get an improvement in exhaust port depression
but you have robbed the intake compressor of 30% hp. Filling that cylinder
is extremely important. Remember the piston gives 100% cylinder volume
exhaust but only slight help in cylinder filling. So where would you want to
direct your available HP? I have dismissed is an incredible amount of detail
in your question. Exhaust dilution of the intake charge, thermodynamics,
CFD. Materials developments, etc. All of it is doable but the effort is
probably directed in the wrong direction.
-Elon
_______________________________________________
Land-speed mailing list
http://autox.team.net/mailman/listinfo/land-speed
|