Re: re Re: Ceramic coating EM's - II

[quk@isham-research.demon.co.uk (Phil Payne)]

In message <A955A4BCA8F8D011AE1C0000F804A88A0413C6C5@emss05m02.sanders.lmco.com> "Smith, Kirby A" writes:

>> No, it converts kinetic energy into heat.  The fact that exhaust gas
>> is hot has nothing to do with it - it would be just as happy with
>> cold gas input.
>
> Hmmm Phil, I'm not sure I would embrace this perspective.  Your first
> sentence is literally true over the entire system.  The exhaust kinetic
> energy is used to perform work on the exhaust turbine (which is attached to
> the intake side compressor of course, pressurizing the intake manifold and
> in the process generating heat).  If the gas kinetic energy is partially
> used, the temperature of the gas will fall for that reason, as well as due
> to the drop from any pressure fall across the turbine.

Kinetic energy is mass times velocity.  Mass cannot be altered outside
of nuclear reactors - only velocity is available.  The blades are spun
effectively by pressure - a differential between the manifold and the
downpipe.  Heat has absolutely nothing to do with turbine operation -
it's just a way of expanding the volume of an available gas to make it
do physical work.  Once combustion is complete, the temperature of the
gas starts to fall - to the point where you can put your hand in the
tailpipe stream.

Heat is a form of potential energy, but there's no way of using it in
a turbine.  In such a device, it's merely a nuisance.

> I do not believe your second sentence agrees with my understanding of turbos
> from books I have read.  I believe the shape of turbines, whether jet engine
> or in turbosuperchargers, is designed to use both flow and temperature.
> This may all be semantic, as heat is kinetic energy in a gas.  The kinetic
> energy is both random and directional, and both may be used in a heat
> engine.

What physical effect exploits the temperature of the gas?  No water is
boiled to make steam.  The effects are purely physical - the exertion
of pressure against the blades.

--
 Phil Payne
 UK Audi quattro Owners Club
 Phone: 07785 302803   Fax: 0870 0883933