Why are multiple engines different?

Mxsmanic wrote:
cjcampbell writes:

A turborprop
increases safety, but now you are talking real money, both in
acquisition cost and in fuel and maintenance.

Why are turboprops so much more expensive? I thought gas turbines
were supposed to be simpler and more efficient.

They are simple, but much less efficient than piston engines. Every
teaspoon of fuel has a fixed number of calories. Efficiency is measured
by what percentage of these calories is translated to thrust. The
reason turbines generate so much power despite their inefficiency is
that they can burn a lot more fuel even though they waste much of the
energy in the fuel. The inefficiency translates into incompletely
burned fuel, waste heat, exhaust, and pollution. Basically, this means
that you have to burn more fuel to generate 100hp in a turbine engine
than you do in a piston engine. A jet engine loses even more efficiency
in the translation of hp to thrust. A turboprop is more efficient than
a pure jet because of its propeller, but it still is not as efficient
as a piston engine. Turbines will probably never be as efficient as
piston engines. This is why gas turbine automobiles have never become
popular. People don't want a car that gets less than 10mpg unless it is
a Rolls Royce. Plus, acceleration is terrible. Chrysler built a batch
of gas turbine concept cars back in the early '60s and lent them to
ordinary consumers as a test. People hated them, not least because of
the annoying, high-pitched whine. I remember seeing them at car shows
back then. But, hey: it would burn anything -- gas, diesel, jet fuel,
vegetable oil, even perfume (and how long will it be before the price
of gas approaches that of perfume, either as fuel or otherwise -- and
what is it with cars and perfume, anyway?).

The reason we use jet engines is that they are inherently more powerful
and they can operate at high altitudes where the efficiency penalty
compared to piston engines is less. At high speeds, drag is a more
important factor in fuel economy than engine efficiency, so jet
airliners get their best fuel economy at high altitude. But for short
hauls where it would just be a waste of fuel to climb to high altitude
and descend again, a turboprop will deliver more power than a piston
engine with greater fuel economy than a jet.

cjcampbell wrote:
Mxsmanic wrote:
cjcampbell writes:

A turborprop
increases safety, but now you are talking real money, both in
acquisition cost and in fuel and maintenance.
Why are turboprops so much more expensive? I thought gas turbines
were supposed to be simpler and more efficient.

They are simple, but much less efficient than piston engines.

Plus, parts are a lot more expensive and when things go very bad, the
maintenance costs are a lot more than a piston. That alone scares a lot
of operators off.

Ok, actually, I don't know much about turboprops, but that's the case
for turbofans.

Emily wrote:
cjcampbell wrote:
Mxsmanic wrote:
cjcampbell writes:

A turborprop
increases safety, but now you are talking real money, both in
acquisition cost and in fuel and maintenance.
Why are turboprops so much more expensive? I thought gas turbines
were supposed to be simpler and more efficient.

They are simple, but much less efficient than piston engines.

Plus, parts are a lot more expensive and when things go very bad, the
maintenance costs are a lot more than a piston. That alone scares a lot
of operators off.

Ok, actually, I don't know much about turboprops, but that's the case
for turbofans.

From a maintenance standpoint, just think of a turboprop as being a
turbofan with a lot less blades.

cjcampbell wrote:
Emily wrote:
cjcampbell wrote:
Mxsmanic wrote:
cjcampbell writes:

A turborprop
increases safety, but now you are talking real money, both in
acquisition cost and in fuel and maintenance.
Why are turboprops so much more expensive? I thought gas turbines
were supposed to be simpler and more efficient.
They are simple, but much less efficient than piston engines.
Plus, parts are a lot more expensive and when things go very bad, the
maintenance costs are a lot more than a piston. That alone scares a lot
of operators off.

Ok, actually, I don't know much about turboprops, but that's the case
for turbofans.

From a maintenance standpoint, just think of a turboprop as being a
turbofan with a lot less blades.

LOL...yeah, the whole gas generator and power tubine thing seems a
little to complex. I'm sure at some point I understand it, but you
forget what you don't use.

All internal combustion engines work the same. A turbine
just does it as a series of continuous events in different
sections of the engine and a piston engine does one at a
time so power is produced only 1/4 of the time in a 4 cycle
and 1/2 the time in a two cycle.
I'm going to print some T-shirts...

"SUCK
SQUEEZE
BANK and
BLOW

Get your mind out of the gutter, it is an engine"


The P&W PT6 is perhaps the most popular turboprop. It uses
air coupling between the power and reduction gear section.
Makes it better in many ways, but there is a loss of
efficiency.


"Emily" wrote in message
...
| cjcampbell wrote:
| Emily wrote:
| cjcampbell wrote:
| Mxsmanic wrote:
| cjcampbell writes:
|
| A turborprop
| increases safety, but now you are talking real
money, both in
| acquisition cost and in fuel and maintenance.
| Why are turboprops so much more expensive? I thought
gas turbines
| were supposed to be simpler and more efficient.
| They are simple, but much less efficient than piston
engines.
| Plus, parts are a lot more expensive and when things go
very bad, the
| maintenance costs are a lot more than a piston. That
alone scares a lot
| of operators off.
|
| Ok, actually, I don't know much about turboprops, but
that's the case
| for turbofans.
|
| From a maintenance standpoint, just think of a turboprop
as being a
| turbofan with a lot less blades.
|
| LOL...yeah, the whole gas generator and power tubine thing
seems a
| little to complex. I'm sure at some point I understand
it, but you
| forget what you don't use.

spelling correction
"Jim Macklin" wrote
in message news:MMYWg.2126$XX2.1083@dukeread04...
| All internal combustion engines work the same. A turbine
| just does it as a series of continuous events in different
| sections of the engine and a piston engine does one at a
| time so power is produced only 1/4 of the time in a 4
cycle
| and 1/2 the time in a two cycle.
| I'm going to print some T-shirts...
|
| "SUCK
| SQUEEZE
| BANG and
| BLOW
|
| Get your mind out of the gutter, it is an engine"
|
|
| The P&W PT6 is perhaps the most popular turboprop. It
uses
| air coupling between the power and reduction gear section.
| Makes it better in many ways, but there is a loss of
| efficiency.
|
|
| "Emily" wrote in message
| ...
|| cjcampbell wrote:
|| Emily wrote:
|| cjcampbell wrote:
|| Mxsmanic wrote:
|| cjcampbell writes:
||
|| A turborprop
|| increases safety, but now you are talking real
| money, both in
|| acquisition cost and in fuel and maintenance.
|| Why are turboprops so much more expensive? I
thought
| gas turbines
|| were supposed to be simpler and more efficient.
|| They are simple, but much less efficient than piston
| engines.
|| Plus, parts are a lot more expensive and when things
go
| very bad, the
|| maintenance costs are a lot more than a piston. That
| alone scares a lot
|| of operators off.
||
|| Ok, actually, I don't know much about turboprops, but
| that's the case
|| for turbofans.
||
|| From a maintenance standpoint, just think of a
turboprop
| as being a
|| turbofan with a lot less blades.
||
|| LOL...yeah, the whole gas generator and power tubine
thing
| seems a
|| little to complex. I'm sure at some point I understand
| it, but you
|| forget what you don't use.
|
|

Jim Macklin wrote:
All internal combustion engines work the same. A turbine
just does it as a series of continuous events in different
sections of the engine and a piston engine does one at a
time so power is produced only 1/4 of the time in a 4 cycle
and 1/2 the time in a two cycle.
I'm going to print some T-shirts...

"SUCK
SQUEEZE
BANK and
BLOW

Is there a reason you continually post information that I already know
in my direction?

"Emily" wrote in message
. ..
Jim Macklin wrote:
All internal combustion engines work the same. A turbine just does it as
a series of continuous events in different sections of the engine and a
piston engine does one at a time so power is produced only 1/4 of the
time in a 4 cycle and 1/2 the time in a two cycle.
I'm going to print some T-shirts...

"SUCK
SQUEEZE
BANK and
BLOW

Is there a reason you continually post information that I already know in
my direction?

Emily, PLEASE............this is a family oriented newsgroup!

Karl

Yes, I lazy, old and skip a lot of the posters, I do read
yours and so I post stuff that pops into my weak, perverted
mind, you should take offense. BTW, you left the context
statement off, I also corrected the spelling to BANG. For
those not into engines...
induction,compression, ignition-power and exhaust.


"Emily" wrote in message
. ..
| Jim Macklin wrote:
| All internal combustion engines work the same. A
turbine
| just does it as a series of continuous events in
different
| sections of the engine and a piston engine does one at a
| time so power is produced only 1/4 of the time in a 4
cycle
| and 1/2 the time in a two cycle.
| I'm going to print some T-shirts...
|
| "SUCK
| SQUEEZE
| BANK and
| BLOW
|
| Is there a reason you continually post information that I
already know
| in my direction?

cjcampbell writes:

The reason we use jet engines is that they are inherently more powerful
and they can operate at high altitudes where the efficiency penalty
compared to piston engines is less. At high speeds, drag is a more
important factor in fuel economy than engine efficiency, so jet
airliners get their best fuel economy at high altitude. But for short
hauls where it would just be a waste of fuel to climb to high altitude
and descend again, a turboprop will deliver more power than a piston
engine with greater fuel economy than a jet.

There are still the questions of simplicity and reliability, which I
thought were both higher for gas turbines. They are certainly more
reliable; and I should think they'd be simpler, too.

--
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