Steam Turbines - Cruise power

[MarchH...@hotmail.com]

If steam turbine powered warships were fitted with a secondary cruise
turbine then would not even greater efficiency be achieved by having a
secondary steam piston engine instead of a cruise turbine ?

The steam piston engine would have to be alongside the propshaft and
connected via a gearbox

Alternatively a chain drive and sprag one-way clutch

The benefits for cruise and loiter time would have been huge.

[Ray O'Hara]

<MarchH...@hotmail.com> wrote in message
news:l7l8a7pttt2fgfmh0...@4ax.com...

and more space taken up by macinery and an expanded armored box or machenery
left unprotected, and of course extra weight.
which means cutting back elsewhere.
it all has to balance out, change one thing and soon its ten things
changed.

[Eugene Griessel]

Hardly. A steam reciprocating engine is mechanically and thermally
less efficient than a turbine and quite a bit larger and heavier pound
per horsepower. Think of it - a steam piston (or any piston) is a
weight in motion that has to be stopped dead twice in every
revolution. Quite a bit of energy is expended doing that. A turbine
does not have that drawback.

Eugene L Griessel

If At First You Don't Succeed...blame Someone Else And Seek Counseling.

[Keith W]

MarchH...@hotmail.com wrote:
> If steam turbine powered warships were fitted with a secondary cruise
> turbine then would not even greater efficiency be achieved by having a
> secondary steam piston engine instead of a cruise turbine ?
>

No, steam turbines are better than 40% efficient while a quad expansion
recip will be lucky to hit 25%

The highest efficiency engines are the big low speed diesels which are
very large.

Keith

[Eugene Griessel]

On Sun, 23 Oct 2011 20:07:20 +0100, "Keith W"
<keithnosp...@demon.co.uk> wrote:

>MarchH...@hotmail.com wrote:
>> If steam turbine powered warships were fitted with a secondary cruise
>> turbine then would not even greater efficiency be achieved by having a
>> secondary steam piston engine instead of a cruise turbine ?
>>
>
>No, steam turbines are better than 40% efficient while a quad expansion
>recip will be lucky to hit 25%

Hmmm I'd like to meet that quad expansion managing 25% - 15% would be
bloody good.

>The highest efficiency engines are the big low speed diesels which are
>very large.

And tend to run at constant speed for a large part of their operating
time. Hardly useful in a warship. We used to start slowing down the
engine many hours before hitting port. One or two revs every thirty
minutes. Otherwise those cyclinder liners would suffer.

Eugene L Griessel

The meek shall inherit the earth -- they are too weak to refuse.

[Peter Skelton]

I think that the OP was considering the very early direct-drive period,
otherwise the suggestion makes no sense at all. The short answer is
that, if gearboxes could have been made to handle the necessary power,
it would have made more sense to put them on the turbines removing the
recips advantage completely.

--
Peter

[Eugene Griessel]

I have been pondering this reply and keep asking myself what advantage
recips had over turbines. I cannot think of any offhand. I have only
ever known one large steam recip personally - and it was a WW2 model
2000 hp triple expansion removed from a ship and mounted ashore for
some long-forgotten training function. Despite not being in service
in the fleet we used to flash the thing up from time to time for fun
more than anything. It impressed visitors on Navy Days as well,
thumping away squirting steam from every orifice and covering everyone
with a fine mist of oil.

Eugene L Griessel

Knowledge is an unending adventure at the edge of uncertainty.
Jacob Bronowski

[Dennis]

Eugene Griessel wrote:

> I have been pondering this reply and keep asking myself what advantage
> recips had over turbines. I cannot think of any offhand. I have only
> ever known one large steam recip personally - and it was a WW2 model
> 2000 hp triple expansion removed from a ship and mounted ashore for
> some long-forgotten training function. Despite not being in service
> in the fleet we used to flash the thing up from time to time for fun
> more than anything. It impressed visitors on Navy Days as well,
> thumping away squirting steam from every orifice and covering everyone
> with a fine mist of oil.

At one time at least on Wiki's article on the recip steam engine, I saw the
claim that for <= 1000 HP, a recip engine was much more efficient than a
steam turbine. I'm not sure why that would be; otherwise, I think a
turbine would be more efficient for a given steam pressure, temp, exhaust,
cycle, etc.

Dennis

[Keith W]

Eugene Griessel wrote:
> On Sun, 23 Oct 2011 16:05:51 -0400, Peter Skelton
>>

>> I think that the OP was considering the very early direct-drive
>> period, otherwise the suggestion makes no sense at all. The short
>> answer is that, if gearboxes could have been made to handle the
>> necessary power, it would have made more sense to put them on the
>> turbines removing the recips advantage completely.
>
> I have been pondering this reply and keep asking myself what advantage
> recips had over turbines. I cannot think of any offhand. I have only
> ever known one large steam recip personally - and it was a WW2 model
> 2000 hp triple expansion removed from a ship and mounted ashore for
> some long-forgotten training function. Despite not being in service
> in the fleet we used to flash the thing up from time to time for fun
> more than anything. It impressed visitors on Navy Days as well,
> thumping away squirting steam from every orifice and covering everyone
> with a fine mist of oil.
>
> Eugene L Griessel
>

They were cheap and a mature technology that didnt require
expensive gearing or astern turbines especially in small ships

In the UK they persisted in use with auxillaries such as the Victualling
Inshore Craft that developed from the Clyde Puffers and of
course the Flower Class Corvettes until the 1950's

Keith

[Eugene Griessel]

Beyond the Flower class - the Loch's had them too. The engine I was
talking about came from a Loch class frigate. Another "advantage" was
the level of technical skill needed to operate and maintain it was
lower than a turbine. However those advantages have nothing to do
with whether it was a better prime mover or not.

Eugene L Griessel

Don't use a big word where a diminutive one will suffice.

[Eugene Griessel]

On Mon, 24 Oct 2011 10:28:43 +0200, Eugene Griessel
<eug...@dynagen.co.za> wrote:

>Beyond the Flower class - the Loch's had them too. The engine I was
>talking about came from a Loch class frigate. Another "advantage" was
>the level of technical skill needed to operate and maintain it was
>lower than a turbine. However those advantages have nothing to do
>with whether it was a better prime mover or not.

I've been having a hard think about the installation we had and for
the life of me I cannot recall whether the admiralty 3 drum boiler
that was used had superheat. If I am correct then the triple
expansion engine ran on saturated steam. This would make for some
weight saving in the boiler - but lower thermal efficiency. I know
the same boiler on our W class destroyers and type 15 frigate had
superheat - of course it was providing steam for turbines.

Eugene L Griessel

History does not record anywhere at any time a religion that has a rational
basis. Religion is a crutch for people not strong enough to stand up to the
unknown without help. But, like dandruff, most people do have a religion
and spend time and money on it and seem to derive considerable pleasure
from fiddling with it.

[Dalesql]

The manufacturing practices of the day made it easier to produce the
reciprocating engines than turbines. Also, the very high precision
reduction gears needed by turbines also were harder to make than the
reduction gears used by reciprocating engines.

Until turbine manufacturing got advanced enough to achieve those very
close tolerances needed, the steam turbine lost a lot of energy to steam
getting around the ends of the fan blades.

--Dale

[Keith W]

Especially on a VIC or a Clyde Puffer where you a crew of
4 or 5

> However those advantages have nothing to do
> with whether it was a better prime mover or not.
>

I guess that depends on how you define best but turbines
were definitely more efficient.

Keith

[Eugene Griessel]

On Mon, 24 Oct 2011 12:37:17 +0100, "Keith W"

I define it in context of the original question asked here. There is
no real "best" for everything - just the best for the task at hand.

Eugene L Griessel

Never share a foxhole with anyone braver than you are.

[Peter Skelton]

I'm away from my books, if I get too far off the facts please flame gently.

Before WWI propellers seemed to work best in the range of 10 rpm/knot
(It's now much less 3 or 4?) so 20 knots meant 200 rpm or so. That's
high end for a VTE engine, they aren't that well balanced.

Turbines, on the other hand, liked to spin in the low thousands. The
faster a turbine spins, the more power it can develop for its size. If
the rpm is dropped too far, the efficiency goes to pot too (slippage in
the turbine is the culprit, I believe). Before reduction gearing (or
electric drive in the US), the turbine had to spin at prop speed ie. far
too slowly. Naval steam turbines are generally versions of turbines that
developed much more power ashore because they could run faster there.
They were huge by modern standards. When ships were reengined, savings
in the 5000 ton range were sometimes achieved on 30000 ton ships with
significant armour and armament weights.

The bottom line was that the direct drive turbines were run at the
ragged lower edge of their rpm range, when they dropped below fifteen to
eighteen knots, their efficiency was very poor, even worse than VTE's.

--
Peter

[Eugene Griessel]

On Mon, 24 Oct 2011 07:50:23 -0400, Peter Skelton

Forgive me if I'm wrong but reading the original question:

"If steam turbine powered warships were fitted with a secondary
cruise turbine then would not even greater efficiency be achieved by
having a secondary steam piston engine instead of a cruise turbine ?"

To my mind spells geared turbines and not direct drives.

.
Eugene L Griessel

There is no conclusive evidence of life after death. But there is no
evidence of any sort against it. Soon enough, you will know, so why fret
about it?

[Derek Lyons]

The best _available_ for the task at hand _within the schedule and
budget_. It's been alluded to upthread, but availability of machinery
and hands of the appropriate skill level factor (to name just of the
many) into the equation as well. Determining what is 'best' can be a
complex and uncertain task indeed.

D.
--
Touch-twice life. Eat. Drink. Laugh.

http://derekl1963.livejournal.com/

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

[Harry Bennett]

Turbines don't have to have superheated steam - they may like it but
they run quite well without it otherwise SSN's would have a problem.

Harry

[Keith W]

Indeed but as Eugene said this seriously lowers thermal efficiency
which is rather less of an issue when the heat comes from
fissioning atoms.

Keith

[Eugene Griessel]

Yes, I am aware of that - most turbines connected to reactors use
non-superheated steam. The disadvantages are a physically bigger and
slower turbine - with more chance of blade erosion.

Eugene L Griessel

The secret of success is sincerity.
Once you can fake that you've got it made.

[Tankfixer]

In article <rolca713rns8ufb1s...@4ax.com>, - Eugene
Griessel eug...@dynagen.co.za spouted !

Back on the subject of mixed powerplants, recip and turbine.
The Frence aircraft carrier Bearn had turbines on her inboard shafts for
speed (what little there was) and triple expansion engines on the
outboard for cruising.

[Eugene Griessel]

It is rumoured, by the malicious, that the Bearn's machinery was
dictated by the supreme unreliability of the French turbines rather
than for any advantages gained otherwise.

Eugene L Griessel

Marriage is a life sentence with partial remission for bad conduct.

[Keith W]

As I recall Bearn was originally laid down before WW1
as a Normandie Class Battleship powered by reciprocating
engines and turbines. The French lacked the facility to
produce the gearboxes needed for efficient turbine use
hence the recip engines for cruisng. This was not that
unusual , RMS Titanic had a mixed power plant too.

Keith

[Eugene Griessel]

She benefitted enormously from British input on carrier design but the
basic hull layout was, as you say, a Normandie class battleship. It
is however true that the French turbines of the era were notoriously
unreliable.

Eugene L Griessel

Our Government:
What do they _do_ all day long and why does it _cost_ so much?

[Dennis]

Harry Bennett wrote:

>> I've been having a hard think about the installation we had and for
>> the life of me I cannot recall whether the admiralty 3 drum boiler
>> that was used had superheat. If I am correct then the triple
>> expansion engine ran on saturated steam. This would make for some
>> weight saving in the boiler - but lower thermal efficiency. I know
>> the same boiler on our W class destroyers and type 15 frigate had
>> superheat - of course it was providing steam for turbines.
>

> Turbines don't have to have superheated steam - they may like it but
> they run quite well without it otherwise SSN's would have a problem.

Reciprocating engines also get better efficiency with superheated steam. A
few years back, I saw curves of tests of an old diesel engine that had been
converted to a recip 600 psig steam engine. The effect of superheat on
efficiency was quite dramatic!

I know that they did all sort of things to avoid condensation on the
cylinder walls - multiple expansion, uniflow, etc. Superheat and reheat
would be others.

Dennis

[Tankfixer]

In article <jihda7pf40rdmnm45...@4ax.com>, - Eugene

The reference I was reading last night suggested that...

[dott.Piergiorgio]

Il 25/10/2011 21:46, Dennis ha scritto:
> Harry Bennett wrote:
>
>>> I've been having a hard think about the installation we had and for
>>> the life of me I cannot recall whether the admiralty 3 drum boiler
>>> that was used had superheat. If I am correct then the triple
>>> expansion engine ran on saturated steam. This would make for some
>>> weight saving in the boiler - but lower thermal efficiency. I know
>>> the same boiler on our W class destroyers and type 15 frigate had
>>> superheat - of course it was providing steam for turbines.
>>
>> Turbines don't have to have superheated steam - they may like it but
>> they run quite well without it otherwise SSN's would have a problem.
>
> Reciprocating engines also get better efficiency with superheated steam. A
> few years back, I saw curves of tests of an old diesel engine that had been
> converted to a recip 600 psig steam engine. The effect of superheat on
> efficiency was quite dramatic!

huh ?

is actually possible to convert a diesel engine in an uniflow
reciprocating engine ?

Best regards from Italy,
dott. Piergiorgio.

[vaughn]

"dott.Piergiorgio" <chied...@ask.me> wrote in message
news:eD%pq.90270$GZ3....@tornado.fastwebnet.it...

> is actually possible to convert a diesel engine in an uniflow reciprocating
> engine ?
>

Yes! It would take some serious valve and cam re-engineering, but you could
possibly convert any piston IC engine to steam. Since the resulting steam
engine would likely be single expansion and because of other factors, efficiency
would likely be abysmal..

Vaughn

[William Black]

You can make just about any engine turn over by blowing a gas under
pressure through it.

It's more or less how a Coffman starter works...

And they still use those to start the big diesels used in UPS systems.

--
William Black

Free men have open minds
If you want loyalty, buy a dog...

[Dennis]

vaughn wrote:

> "dott.Piergiorgio" wrote in message

>
>> is actually possible to convert a diesel engine in an uniflow
>> reciprocating engine ?
>>
> Yes! It would take some serious valve and cam re-engineering, but you
> could possibly convert any piston IC engine to steam. Since the
> resulting steam engine would likely be single expansion and because of
> other factors, efficiency would likely be abysmal..

I'm not sure it would be a *uniflow* engine. A two-cycle diesel engine
would somewhat resemble a uniflow steam engine, but not really.

As Vaughn said, it would most likely be single expansion, unless you used
2-3 cylinders for the 2nd expansion, and then the expansion ratio would
most likely be wrong.

I don't remember that the efficiencies shown on the curves were so bad.
This was a high-temperature solar-energy project for 3rd world locations.

Dennis

[vaughn]

"Dennis" <tsalagi...@hotmail.com> wrote in message
news:Xns9F8AC2D79CA00ts...@130.133.4.11...

> I don't remember that the efficiencies shown on the curves were so bad.
> This was a high-temperature solar-energy project for 3rd world locations.

To get any kind of reasonable efficiency from a Rankine (steam) cycle engine,
you need a condenser and you need some way to continue to extract energy from
the steam as it expands all the way from the high pressure of the boiler to the
vacuum of the condenser.. As has already been noted, superheat also improves
efficiency.

That doesn't mean a steam engine is useless without all that stuff, it's just
inefficient. Look at an old railroad engine for an example of a damn useful,
but inefficient open-cycle single-expansion steam engine..

Vaughn

[Dennis]

vaughn wrote:

> "Dennis" wrote in message

>> I don't remember that the efficiencies shown on the curves were so
>> bad. This was a high-temperature solar-energy project for 3rd world
>> locations.
>
> To get any kind of reasonable efficiency from a Rankine (steam) cycle
> engine, you need a condenser and you need some way to continue to
> extract energy from the steam as it expands all the way from the high
> pressure of the boiler to the vacuum of the condenser.. As has
> already been noted, superheat also improves efficiency.

I think the curve was for the efficiency of the *engine* compared to an
isentropic (perfect) engine. Not the same as the thermal efficiency of the
overall cycle, which I believe did include some sort of condenser. The
curves did show the effect of various amounts of superheat on the
'efficiency' I just mentioned.

> That doesn't mean a steam engine is useless without all that stuff,
> it's just inefficient. Look at an old railroad engine for an example
> of a damn useful, but inefficient open-cycle single-expansion steam
> engine..

Yup. I think there were some later railroad engines that were double-
expansion. There were experiments with condensers. Someone here pointed
out a successful type of direct-drive railroad turbine locomotive.

Dennis

[ken...@cix.compulink.co.uk]

In article <Xns9F8AD8E31246Cts...@130.133.4.11>,

tsalagi...@hotmail.com (Dennis) wrote:

> Yup. I think there were some later railroad engines that were double-
> expansion. There were experiments with condensers. Someone here
> pointed out a successful type of direct-drive railroad turbine
> locomotive.

Compound engines were built in quantity in the UK by the Midland and
London Midland railways. The problem was that they were much more
expensive to build and not that more efficient than a properly designed
simple engine with variable cut of. Some of the Churchward engines could
run at 20% cut of which allowed the steam to expand for 80% of the
stroke.

An early experiment in marine steam compared a high cut off simple
engine with a compound. Power output was much the same and so was fuel
consumption but the simple engine fell apart.

The key is getting steam expansion and that can be done several ways.

Ken Young

[Andy Breen]

On Thu, 27 Oct 2011 09:47:36 -0500, kenney wrote:

> In article <Xns9F8AD8E31246Cts...@130.133.4.11>,
> tsalagi...@hotmail.com (Dennis) wrote:
>
>> Yup. I think there were some later railroad engines that were double-
>> expansion. There were experiments with condensers. Someone here
>> pointed out a successful type of direct-drive railroad turbine
>> locomotive.
>
> Compound engines were built in quantity in the UK by the Midland and
> London Midland railways.

And by the London and North Western and North Eastern Railways..

> The problem was that they were much more
> expensive to build and not that more efficient than a properly designed
> simple engine with variable cut of. Some of the Churchward engines could
> run at 20% cut of which allowed the steam to expand for 80% of the
> stroke.

Experiments in the late 1920s showed that the Midland-type engines were
badly throttled between HP and LP sides, degrading their efficiency.
Other countries with more progressive engineers (France, Austria)
produced much more efficient compound steam locomotives, though by marine
standards their thermal efficiency was still poor (bound to be, with no
condenser).

--
Speaking only for myself

[Andy Breen]

On Thu, 27 Oct 2011 09:47:36 -0500, kenney wrote:

> In article <Xns9F8AD8E31246Cts...@130.133.4.11>,
> tsalagi...@hotmail.com (Dennis) wrote:
>
>> Yup. I think there were some later railroad engines that were double-
>> expansion. There were experiments with condensers. Someone here
>> pointed out a successful type of direct-drive railroad turbine
>> locomotive.
>
> Compound engines were built in quantity in the UK by the Midland and
> London Midland railways.

And by the London and North Western and North Eastern Railways..

> The problem was that they were much more
> expensive to build and not that more efficient than a properly designed
> simple engine with variable cut of. Some of the Churchward engines could
> run at 20% cut of which allowed the steam to expand for 80% of the
> stroke.

[MarchH...@hotmail.com]

> Eugene Griessel <eug...@dynagen.co.za> wrote:

>
>>MarchH...@hotmail.com wrote:

>And tend to run at constant speed for a large part of their operating
>time. Hardly useful in a warship. We used to start slowing down the
>engine many hours before hitting port. One or two revs every thirty
>minutes. Otherwise those cyclinder liners would suffer.
>

Why would the cylinder liners suffer ?

[Eugene Griessel]

Three inch thick cast iron. Specifications called for no more than a
degree temperature change per hour or the things could crack. Very,
very expensively as they were about 12 foot tall and five foot in
diameter.

Eugene L Griessel

Smile, it's the second-best thing you can do with your lips.