Steam & Excursion > Why pressure? Con’d.

On the surface,The coal lumps in heavy loaded carts soon got mired
the crude, muddy roads...

It was soon discovered that two
Parallel rails could more easily carry coal carts, pulled by horses...
In fact, a single horse could pull more than one coal cart..

Some ‘genius’ dreamed of a cranked axle, a steam cylinder,
A boiler, and chains ... leading to the invention of the “iron-horse”...

Pressure moved the carts, ingenuity
continued and trains of many uses
came into being...

In the 1880s an English inventor named Parsons built the first
Fin-powered, rotary shaft ‘engine’.
This ‘engine’ used a series of discs,
with angled fins on a rotating shaft
separated by fixed fins in between
multiple fin ‘stages’ of the rotating shaft...

The fins were contained in a cylinder shaped housing, steam admitted at one end... and exhausted out the other end.

The first flow of steam whistled right-through the fins... which slowly
Began to turn.... the spinning shaft
Soon produced great rotative force and the quantity of steam flow through the turbine dropped to a minuscule Amount...

The HEAT contained in the steam flow, Not it’s ‘pressure’ was doing the. ‘Work ‘...

That was the CRUCIAL concept
that led to the Industrial Revolution..

Parsons’ invention was key to the
Thermodynamics studies in schools and universities.... it soon led to other more effective ‘heat engines’
Out-pacing the need for old style
Boilers and cylinders...

In the early 20th century, locomotives. with many drivers on the rails were perfected so that
more freight cars could be hauled across America.... ‘pressure’ gets them started... “heat” is what accelerates them... superheating
separated the SuperPower steam
From the older, Iron Horses...

The reciprocating engines descended from Ford’s assembly lines... soon were replaced by
Jet-propelled engines and today’s
many turbine-based, powered
‘Engines’...

Heat powered, no longer ‘pressure
Powered’..

Now, go read a book: titled:
“From Watt to Clausius”...
To get schooled in the history
and the whys & wherefores
of Thermodynamics & heat Engines..

W.

Posted from iPhone



Edited 1 time(s). Last edit at 06/25/20 07:44 by wcamp1472.

Hmm, not sure you can really seperate pressure from heat...

What did you mean 'pressure moved the carts'?

While Parson gets credit for inventing the steam turbine, it wasn't until 1938 when GE first adapted it to a railway locomotive and tested it on the Union Pacific. To imply, as you have, that the steam turbine was adapted much earlier in the history of steam locomotion, is misleading. 

Arved Grass
Fleming Island, FL

#1. How much ‘pressure’ is in a “jet”
Engine that powers our modern
Aircraft? Very low pressure, compared to the amount of work produced... Admire the beauty
of jet-engine con-trails... that hang
Stable in the sky.


#2. “Pressure”, as applied in moving the carts... whether from legs/shoulders, hooves/harnesses,
or pistons & wheel cranks, or wheel rims and rails, or armatures & stators... ( sand helps)...

If you don’t apply pressure to the carts —- they aren’t moving...
that ‘pressure’ can be provided by all sorts of ingenuity, gravity works, too.

W.

Posted from iPhone

Let me try a couple of parts of the concepts being discussed:
Steam pressure is directed to the face of the piston.  For a given size of piston, more pressure results in more force acting on the rods and turning the wheels.
You can see this on compound locomotives where high boiler pressure steam is used on one set of cylinders and that exhaust steam is then directed, at a much lower pressure, to the larger diameter low pressure cylinde, those larger cylinders exerting something close to the same amount of force as the high pressure cylinders.  (Marine engines sometimes used more that two stages of expansion.)
Higher pressure means a higher boiling temperature for water in the confined space of the boiler thus there is more heat energy in higher pressure steam.
The efficiency of heat engines increases with a larger difference between the temperatures of the input and output. (Efficiency measured as the amout of useful work obtained from the heat energy or fuel input.)
Thus higherpressure and temperature means both higher efficiency and higher thrust on the cylinders.
The downside of higher pressure is more stress on all the steam system: bigger, stronger castings, boiler shell, pipes, etc.

What effect does superheating have on the steam used in recip locomotives?

Why?

How is it that Doyle can run the
4449 ( with 20 coaches), at 60-per, 300 psi in the boiler & with 140-psi at the steam chest and 700 deg. F. from the ‘units’, and about 30% cut-off?

Why wouldn’t the ‘pressure’ demands be higher?

W.

Posted from iPhone

wcamp1472 Wrote:
-------------------------------------------------------
> What effect does superheating have on the steam
> used in recip locomotives?

Superheating seriously increases the temp. of the steam supplied to the valves.

> Why?

Because it is the heat of expansion that REALLY does the work, i.e. horse power. If it wasn't for the increased steam temperature, then why bother with superheating? Superheating the steam does NOT raise the pressure.


> How is it that Doyle can run the
> 4449 ( with 20 coaches), at 60-per, 300 psi in
> the boiler & with 140-psi at the steam chest and
> 700 deg. F. from the ‘units’, and about 30%
> cut-off?

Because she is "running on the heat of the steam", and you can hear it from the VERY loud & sharp exhaust.


> Why wouldn’t the ‘pressure’ demands be
> higher?

Damned good question, for the "experts"!


> W.
 

Geez, after 55 years in the fluid power industry you're telling me that hot air or hot oil will give me more piston force than
cold oil or cold air? All you're doing with all that tripe about thermodynamics is writing an algo that describes the latent heat
of your steam as it changes through expansion. It's still the pressure on the face of the area of the cylinder that's providing
the force.

Out 

callum_out Wrote:
-------------------------------------------------------
> Geez, after 55 years in the fluid power industry
> you're telling me that hot air or hot oil will
> give me more piston force than
> cold oil or cold air?

No. As "hot air" and/or "hot oil" is a LOT different the hot, dry steam.

All you're doing with all
> that tripe about thermodynamics is writing an algo
> that describes the latent heat
> of your steam as it changes through expansion.
> It's still the pressure on the face of the area of
> the cylinder that's providing
> the force.
 
Yes, and that increased pressure on the face of the piston comes from the ever expanding, VERY hot, dry steam.

> Out 

Jeez, this thread is a hell of a mess...

1. The industrial revolution was started by turbines? Really?!

2. Carts are moved by pressure? No they're not, they're moved by a force. This is very basic physics.

3. The important equation for a lot of this discussion is the universal gas law, PV=nRT. Increase temperature and either the pressure or volume increases or both increase. Steam locomotives are ALL about pressure and temperature. Why do you think boiler explosions occur?

4. Can someone tell me what 'dry steam' is please? 



Edited 1 time(s). Last edit at 06/25/20 10:43 by exhaustED.

wcamp1472 Wrote:
-------------------------------------------------------
> #1. How much ‘pressure’ is in a “jet”
> Engine that powers our modern
> Aircraft? Very low pressure, compared to the
> amount of work produced... Admire the beauty
> of jet-engine con-trails... that hang
> Stable in the sky.
>

Have you got some numbers to back that up? So why do jet engines have incredibly stress resistant single crystal titanium blades, if they don't have to withstand much pressure?

Carry the analogy to the exhaust-driven, turbine powered super charger used current Diesel engines,
Rail & non-rail.... it is the remaining
HEAT of the exhaust stream that powers the turbo-supercharger...

The power to engine-drive a similar
Capacity supercharger is roughly
Equal to 50% of the output of the
Supercharged engine...

Replace the independent-engine
Driven supercharger... apply the exhaust-driven Turbo charger... and you get the 50% increased power

Turbo-charge a 2000 hp conventional engine, and you get
a 3000 hp capable engine...
And burn LESS fuel...

All engines ( prime movers) are
Heat engines. A typical example of Pressure driven equipment is air-powered tools.

They’re useful, but not really power capable...
Same with hydraulics..

“Pressure engines” are a ‘zero-sum’
game....

W.

Posted from iPhone

wcamp1472 Wrote:
-------------------------------------------------------
> Carry the analogy to the exhaust-driven, turbine
> powered super charger used current Diesel
> engines,
> Rail & non-rail.... it is the remaining
> HEAT of the exhaust stream that powers the
> turbo-supercharger...
>
> The power to engine-drive a similar
> Capacity supercharger is roughly
> Equal to 50% of the output of the
> Supercharged engine...
>
> Replace the independent-engine
> Driven supercharger... apply the exhaust-driven
> Turbo charger... and you get the 50% increased
> power
>
> Turbo-charge a 2000 hp conventional engine, and
> you get
> a 3000 hp capable engine...
> And burn LESS fuel...
>
> All engines ( prime movers) are
> Heat engines. A typical example of Pressure driven
> equipment is air-powered tools.
>
> They’re useful, but not really power capable...
> Same with hydraulics..
>
> “Pressure engines” are a ‘zero-sum’
> game....
>

I'm sorry but this is nonsense.

The heat on its own cannot apply a force. It transfers energy and a force to spin the turbo because hot gases have just been exhausted from the cylinders (the pressure in those cylinders is high) and those gases exit the cylinders with a lot of kinetic energy. That kinetic energy of the gas exerts a force on the turbine blades. I don't know for certain but there may be quite a high pressure due to volume restrictions in the turbo which also helps to power it as the gases are undergoing further expansion as they exit to the exhaust.

A turbocharged engine is more efficient because as well as using the pressure from the initial expansion in the cylindres, it captures some kinetic energy from the exhaust. 

“Pressure engines” are a ‘zero-sum’ game.... What the flaps does that mean?!



Edited 3 time(s). Last edit at 06/25/20 11:21 by exhaustED.

Mr. exhastED,

I don't know anything about a GE or ALCO turbocharged diesel engine, but I do know that the EMD turbocharger is a thermal reaction type, i.e. it is the HEAT of the exhaust gas that determines the speed of the turbine wheel. For an example, in the marine industry, the EMD diesel engine is connected to a very large gear reduction box, i.e. 900 RPM full load speed of the crankshaft produces a gear box out-put shaft speed of around 100 to 120 RPM. So, the design of the boats propeller (called the 'wheel') vs. the hull design, pretty well limits the wheel speed and diesel engine speed. That said, working sort of "lightly" at full engine speed & wheel speed produces only a moderately hot exhaust gas temp.. When really working hard, still at 900 RPM engine speed, the Captain can still increase fuel to the engine, and the exhaust temps raise dramatically, and as a result the turbocharge speed REALLY increases (actually screams in the engine room). All these associated temps.; each cylinder's exhaust leg temp., exhaust temp. into the turbo, and turbine wheel speed are all monitored by the Chief Engineer of the boat, and also visible to the Captain in the wheel house. My point is, the exhaust gas flow/pressure is NOT increased, bu the temperature of the exhaust gas is seriously increased.

The internal design of the EMD turbocharger uses the heat of the exhaust gas through each individual nozzle, which forces against each individual turbine blade (or bucket). The higher the temp. the more power into the turbine blades.

Oh BS, if heat were a diect factor on the turbo it would spin by itself in a heated room. Temperature increases gas pressure because of increaced
molecular movement. It is that increased gas pressure due to heating that spins the turbo faster. A turbo wheel spins faster because of increased
pressure on the wheel not because it's hotter! Oh and GE and Alco turbos work the same way, along with Rajay, Airesearch and everyone else
that's built an exhaust driven turbo.

Out 

HotWater Wrote:
-------------------------------------------------------
> Mr. exhastED,
>
> I don't know anything about a GE or ALCO
> turbocharged diesel engine, but I do know that the
> EMD turbocharger is a thermal reaction type, i.e.
> it is the HEAT of the exhaust gas that determines
> the speed of the turbine wheel. For an example, in
> the marine industry, the EMD diesel engine is
> connected to a very large gear reduction box, i.e.
> 900 RPM full load speed of the crankshaft produces
> a gear box out-put shaft speed of around 100 to
> 120 RPM. So, the design of the boats propeller
> (called the 'wheel') vs. the hull design, pretty
> well limits the wheel speed and diesel engine
> speed. That said, working sort of "lightly" at
> full engine speed & wheel speed produces only a
> moderately hot exhaust gas temp.. When really
> working hard, still at 900 RPM engine speed, the
> Captain can still increase fuel to the engine, and
> the exhaust temps raise dramatically, and as a
> result the turbocharge speed REALLY increases
> (actually screams in the engine room). All these
> associated temps.; each cylinder's exhaust leg
> temp., exhaust temp. into the turbo, and turbine
> wheel speed are all monitored by the Chief
> Engineer of the boat, and also visible to the
> Captain in the wheel house. My point is, the
> exhaust gas flow/pressure is NOT increased, bu the
> temperature of the exhaust gas is seriously
> increased.
>
> The internal design of the EMD turbocharger uses
> the heat of the exhaust gas through each
> individual nozzle, which forces against each
> individual turbine blade (or bucket). The higher
> the temp. the more power into the turbine blades.

With respect, you're ignoring the most basic physics principles. PV=nRT The universal gas law... it applies EVERYWHERE.
Look at that equation. If you increase temperature on the right hand side then something on the left hand side has to increase as well to keep the equation balanced. So volume or pressure increase as the temperature of a gas increases. The physical volume of the engine doesn't change therefore the pressure in that fixed volume HAS TO INCREASE.

I'll say it one more time... You can't increase the temperature of a gas in a confined space and not increase its pressure.

Hmmmm, Ya know, I think you can run a turbo on Compressed Air........It is the speed (pressure if you will) of what pushes on the blades that make it all go.
There, now you have MY 2 cents !!!
Dave

Well then, I didn’t think my question would turn into THIS thread lol. Thanks Jack and Wes. You guys gave me the answers I was working for. As for the debate: I do understand superheaters and their function, so yes, you can increase temps without increasing pressure and get more work. ExhaustED, I wanted to point out a few things with turbine engines since that’s my area of expertise. Wes is right, they produce massive amounts of force with small pressures but huge temp gains. The GE9X is the newest on the market. First off, it’s got 16 carbon fiber fan blades, not titanium. Inside the high pressure side of the compressor temps can soar to about 1,350°F but pressures only reach 100-120psi. This seems like it could be high but this is also an engine that’s physically huge (fan diameter is a little over 11 1/2 feet)! It’s not unusual to see an 80 psi boost on a typical Cat Diesel engine on a semi and they’re capable of more than that. They’re kind of connected but if you have a little pressure then temps can make a huge difference.

Posted from iPhone

JP86 Wrote:
-------------------------------------------------------
> Well then, I didn’t think my question would turn
> into THIS thread lol. Thanks Jack and Wes. You
> guys gave me the answers I was working for. As for
> the debate: I do understand superheaters and their
> function, so yes, you can increase temps without
> increasing pressure and get more work. ExhaustED,
> I wanted to point out a few things with turbine
> engines since that’s my area of expertise. Wes
> is right, they produce massive amounts of force
> with small pressures but huge temp gains. The GE9X
> is the newest on the market. First off, it’s got
> 16 carbon fiber fan blades, not titanium. Inside
> the high pressure side of the compressor temps can
> soar to about 1,350°F but pressures only reach
> 100-120psi. This seems like it could be high but
> this is also an engine that’s physically huge
> (fan diameter is a little over 11 1/2 feet)!
> It’s not unusual to see an 80 psi boost on a
> typical Cat Diesel engine on a semi and they’re
> capable of more than that. They’re kind of
> connected but if you have a little pressure then
> temps can make a huge difference.
>

There you go, you've answered your own question on the pressure situation in a turbine... yes the pressures aren't enormous but they don't need to be because the engine is enormous so the overall force generated is very big.
Force = pressure x area.

But if there's no pressure, there's nothing generated.



Edited 2 time(s). Last edit at 06/26/20 03:02 by exhaustED.

The basics say that higher pressures are a higher temperature, the work of a steam engine is done off of the expansive value that is related to and  obtained by a given temperatiure of the steam.

If we have 30 psi of boiler pressure, and try and move the locomotive, it probably doesn't move. If we have 200psi in the boiler and throw 30psi into the steam chest, it moves. 30psi of boiler pressure on a saturated engine loses some pressure and temperature as it travels, no temperature  and poor expansive value. 30 psi coming from a hotter temp in the boiler at the source has more temp and expansive value.

We throw in superheat temperature, we know much hotter steam at the cylinders then in the boiler does more work.

Development found saturated steam does only so much work and we lose value on its travels to the cylinders, besides the condensation problem as the temperature is a bit lower when at the cylinders. Superheat doesn't condense and creates more efficient work, the higher temperature steam is what is desired, that coupled with proper operation makes for some good efficiency as a whole...

The pressure assigns a temperature to the steam -  Heat does our work - expansive value is the key that runs our locomotive (if I said this in a good creative way)

In my words....



Edited 2 time(s). Last edit at 06/27/20 23:01 by 1003-2719-1385-engr.