"Pooh Bear" wrote in message
...


Ed Huntress wrote:

"carneyke" wrote in message
oups.com...
I think my point is for everything we do there
will always be a "bad" side and its a shame it gets so political. So
please accept my appollogy for being rude and as Jim wrote "Ignorant".
Sorry Jim.....

Gee, you must be coming from an awfully polite newsgroup. g

FWIW, most of the fuel you burn in your car goes out the tailpipe. A
super-efficient spark-ignition engine turns something like 24% of its
fuel
into motive power (if my memory of this number is not accurate, someone
please correct me; I haven't looked it up for years). Of that, something
like 60% makes it to the drive wheels. So a spark-ignition-engined car,
on a
good day, delivers somewhere around 15% of the thermal potential of the
fuel, as motive power to the wheels.

It doesn't get a lot better with other engine types. A large, efficient,
stationary diesel is good for something like 28% at the shaft. The
number is
similar for a huge, stationary, multi-stage steam turbine. And, believe
it
or not, also for a Stirling, running with helium or hydrogen for a
working
fluid, at very high internal gas pressure and with a high-efficiency
heat
exchanger at each end.

Sucks, doesn't it? And that's on a good day. d8-)

Even electricity generation is no better than 37% efficient apparently (
recent
UK figure ).

Graham

Well, even that is somewhat higher than I recall, because the steam-turbine
example above is for one engaged in generating electricity.

However, my memory isn't that precise, and is getting less so, and
technology no doubt has improved. A turbine's practical efficiency isn't a
factor of theoretical heat cycles as much as it is a matter of how much heat
and erosion it can tolerate.

In regard to gas turbines, I visited Pratt & Whitney's engine division
decades ago on a press junket, to hear them tell us how they'd raised the
operating temperature of a jet engine by roughly 100 degrees F, from 2,200
to 2,300 degrees. I remarked that didn't really sound very impressive. An
old P&W engineer sitting next to me said, "Son [I was much younger then
g]," there are men here who would sell their grandmothers for another
hundred degrees."

--
Ed Huntress