High torque engines

[Boston]

http://maggiesfarm.anotherdotcom.com/uploads/elco57.jpg

Im playing with the idea of a big steam launch and considering an engine that has the following statistics associated with it.

http://members.pioneer.net/~carlich/RSE/RSEengines-v4highpowertorque.jpg

the tricky part is that although it took a while, I figured out that this engines HP rating is based off of a watts/hp of 745.7 rather than the boiler HP of 9809.5 watts

( lovely that we have four ways to measure HP eh )

so at 100hp 740rpm 410psi I get a whopping 710 lb/ft of torque, which is substantially higher than what the standard diesel engine would ever turn out

so the question I've got for the group is a basic mechanical engineering one about propeller pitch and shaft speed

the vessel is an elco 57 flat top and with a 3.5 foot draft and 57' at the water line and a 13' beam, it normally cruises at 10 knots with two 210 hp diesels pushing it. Max speed is 14 knots. There horse power rating total is barely more than half, balls to the wind, what the big steam engine can do in its sleep but there shaft speed is higher. Apples to apples the big 4 cylinder steam engine can rock at 1000 rpm 200hp and 1050 lb/ft were as the diesels ( Cummins 6BT5.9 ) can do 403 ft/lb at 1000 rpm although thats not its best range http://www.cmdmarine.com/Products/Commercial%20Propulsion/6B/fr90761.pdf

they gear down
Im going to be gearing up

so the question is whats the optimal shaft speed and prop stats for pushing this hull and how does that effect the choice of engine

[mydauphin]

Consider a bigger prop.... Where is the prop....

[Boston]

prop size and speed is a complete mystery to me thats why I threw up all the data
to collect a consensus view of opinions
I would prefer to have a prop that operates most efficiently in the 700-800 rpm range
on a steam engine I can play with the valves and get it to run forward or backwards
although this particular engine is not set up that way
if that works out I may not need a transmission

[philSweet]

Boston, this is a single motor replacing the original two, correct?

[Boston]

so far thats what Im thinking Phil

best I can do is use one of the online calculators and I come up with for a slip of 20% or an 80% efficient prop
at 740 rpm on a 30 ton fully fueled boat at 57 feet a pitch of 21.41 for a speed of 12 knots
slightly better than I was hoping for in terms of speed
but what kind of torque does it take to drive that screw through the water

for a slip of 15% I get a pitch of 20.15
and for a slip of 25% I get 22.83 pitch
so I think Im in the ball park at a slip of 20% and a pitch of say 21 inches with this engine

concerning hp I get
50-HP = 15 in. pitch
70-HP = 17 in. pitch
100-HP = 19 in. pitch
200-HP = 23-inches or more. although the weight of the boat has got to have something to do with it
but thats bound to be considering diesels which have half the torque of steam

so whats an average slip I should be aiming for and whats up with this thing not mentioning diameter of prop



course its the idiots guide to props

[Guest625101138]

The boat pictured with the dimensions provided will require 115kW to do 10kts and 354kW to do 14kts using realistic prop efficiencies.

The ideal prop for 740rpm will not be achievable with the draft. You need to determine the largest diameter prop that can be fitted. Once you know this you can determine the power required with some accuracy.

Rick W

[philSweet]

20 percent slip at speed would be a good target number for high efficiency. Don't worry too much if you end up with 30 percent at 12 knots due to various constraints. How does this motor perform at "idle" or whatever you call a steam motor ticking over. Does it run right down to 0 rpm like an electric motor? I'd like to know you can go slow enough before figuring on cruising efficiency. It may be worthwhile to use more rpm at cruise, sacrificing a bit of efficiency, in order to gain some additional control at low speed. If the replacement motor was a 4 cylinder diesel replacing two 6 cylinders, I would expect trouble getting it to go as slowly as smoothly as the old setup. Of course you could always put a Kitchen rudder on it! I'm not trying to be awkward, I just have no sense of feel for the steam motor.

[Boston]

actually the steam engine is famous for slow speed high torque
basically it will not run quite as high a torque as an electric at low rpm but its close ( sorta )

the two diesels were 6 cylinders each and the new steamer is 4 cylinders which maxes out at 1000 rpm and typically would run at 400-800 rpm between about 500 and 900 ft/lbs

Rick thanks for dropping by
Im working on finding out the prop diameter for the original boat but its going to be difficult
Ill post it soonest
B

[Boston]

scaling it off the lines I have about 1.17' of room to cram a prop under this thing
that is really not enough space
I might have to modify the lines to fit a decently sized prop

here is a picture of the prop under the same hull configuration but a different deck plan

http://www.1929gidleyyacht.com/images/gallery/CD_exlaunch.jpg

here's a shot of the lines plan

http://i354.photobucket.com/albums/r420/maxtanks/sc031fa1c7.jpg

you can sorta make out the water line ( its the line with all the tick marks on it and the keel, that distance represents 3.5' so scaling that from the picture I come up with about 1.17 feet prop diameter

[Guest625101138]

prop size and speed is a complete mystery to me thats why I threw up all the data
....

And this from a fellow who argued that sailing directly downwind faster than the wind was impossible. Going back a couple of months you seemed to know everything there was to know about propellers!! You were the expert on the theory involved.

theoretical physics
I just patented plasma insulation
although most of the time I work as a general contractor cause it keeps me fed

........
B

I would have thought the calculations involved for a simple boat propeller would be a cinch for one so at ease with theoretical physics.

Rick W

[Guest625101138]

scaling it off the lines I have about 1.17' of room to cram a prop under this thing
that is really not enough space
I might have to modify the lines to fit a decently sized prop

Attached is what you would get if you could fit a 1m prop. It would be 40 x 26. This is larger than I think possible with a draft of 3.5ft without going for large shaft angle.

If this prop could be fitted then note the power is less than my original estimate. Torque for 83.5kW at 740rpm is 1077Nm.

Rick W

[Boston]

nah I was arguing that the amount of energy in a mass being used to power a sled at whatever gearing will only result in a transfer of kinetic energy equal to or less than the original energy applied. Which is sound physics

turns out I was wrong about that into the wind thing ( Im ok with admitting Im wrong from time to time, pretty sure we're all going to be completely wrong at some time or another ) you aught to hear folks going at it up a the university when there is a question about some of the finer points
and yes I did get the patent on plasma insulation ( I got the number round here somewhere if you want to look it up )
fat lot of good its doing me though
but I am far from a plasma physicist, I studied cosmology mostly ( thirty years ago ) theoretical astronomy in layman's terms
I knew Ild be hearing about that eventually
what I did on that one was take the guts out of a fluorescent light bulb, put em in a window frame, add argon to the space between the pains, and tune it using a harmonic resonance frequency tracking system out of a stereo amplifier to radiate at the optimal temp difference between inside and outside in order to create the lowest strength convection loop possible
worked
but your a good sport to be trying to help out cause you got me
I dont know **** about propellers
so no worries on calling me on being so wrong about that one
I was and Im ok with it
( I wasnt ok with thug spamming nor was I ok with those guys descending on our forum with the deliberate intent of tricking the folks here into there games, lets get real they could have come out and explained themselves like they were asked to from the start rather than refuse to give any explanations and launch into personal attacks because they themselves couldnt explain mathmatically how that thing worked after offering to do exactly that, I just called em on it, at least you and I went round and round over a physics issue. Those clowns were in it to pretend they invented something they didnt and patent it as such )
writing a paper on someone else's work is just plane plagiarism

props are a science in themselves and I have little experience in em so it never hurts to ask a few questions of people who have obviously studied them in the course of my self education in the subject

well that is one crazy conversion
11,669 N = 83.5 Klw
1 HP = 746 watts

83500/746 = 112 HP

15.7" what ?
pitch = 660 mm or 26"
at 70% efficiency

70% cannot be the best I can expect
what if I put a cowling around it shouldnt that improve efficiency

[Ad Hoc]

Boston

You're getting bogged down in too much propeller theory which you can't actually control or measure right now, and is bit of a red herring for your application.

1) What is the maximum diameter you get safety get away with, or would like? (is it the 1.17ft prop mentioned above?...can you physically go measure or just use the old lines plan?)
2) What is the most advantageous RPM you wish to use, you have quoted several RPMs for given power above?
3) Do you have any actual performance data of this or sister vessels? Since this relates to the actual resistance of the vessel and hence what power gives what speed and at what displacement.

Without any of these, you wont have a target to aim at to design a prop for your SOR.

[mydauphin]

Fit largest propeller that fits under hull. Figure max rpm for shaft, number of blades and shape. Don't worry the pitch to get it perfect, it will be wrong. But then you have to something to do so real numbers from. You can't really guess the prop because you don't know how hull or engine will truly perform.

[Boston]

the original hull topped out at 14 knots with two 210 hp diesels and around 450+ ft/lbs of torque pushing one prop and eating fuel
the prop looks like it had a diameter of about 14" maybe 16"
I have no idea of the shaft speed
I can fit a pretty dam big prop under the hull but Im not sure how close to the surface I can run a prop without getting into other issues

I could gear up the shaft speed of the new engine Im considering with a transmission but given that steam engines run or can run in both directions I thought it would be kinda trick to leave off the tranny and just reverse the engine when needed

[mydauphin]

I have seem some steam engines that run engine in reverse. I would consider hidden electric engine for marina maneuvers. If I remember problem with steam was it taking time to develop steam. So a steam/electric would be a new concept. The bigger the prop the slow the turning the better for you idea of no tranny. At slow rpm you shouldn't get much cavitation. It looks like prop is pretty much tuck under hull.

[Boston]

ya the hull will be fitted with a electric torquedo 17 hp maneuvering thruster and two boilers one small and quicker to steam for slower speeds and one larger for cruising applications. Both can combine for flank speed. although it may end up advantageous to go with three of the smaller boilers adding each to the system as needed. Titanic ran 33 boilers for each engine and brought them on line as needed for efficiency. RIP.

[Guest625101138]

..... .......

well that is one crazy conversion
11,669 N = 83.5 Klw
1 HP = 746 watts

83500/746 = 112 HP

15.7" what ?
pitch = 660 mm or 26"
at 70% efficiency

The drag of 11669N is based on my quick sketch of the hull - see attached. The power on the hull to do 5m/s (a bit under 10kts) is 11669 * 5 = 58.3kW. Allowing for the 40 x 26 prop efficiency of 70% under these conditions, the shaft power works out at 83.5kW. I will take your word on the conversion to 112HP.

The pitch of 660mm is slightly more than 26". Don't worry about the other numbers.

The long keel aft will add a bit more drag but without getting detailed plans the results will be sufficiently accurate to do prop size comparisons. Interestingly I get a drag of 27160N at 7m/s (say 14kts) which gives very close to the installed power allowing for the prop efficiency.

Rick W

[Boston]

e gad does that mean that my first serious calculations and guessing engine size were roughly correct

40" of prop
thats huge
after reading all day on prop theory Im thinkin that the slow rpms ( 740 is nothing ) should result in higher efficiency

thing is
I got a ton of torque available in this engine
but I read little on the application of torque in a fluid medium
Im starting to think that if I gear the torque out of the system I might gain an advantage in a smaller prop that better fits this hull form

hp = Torque (rpm) / 5252

basically I can spend all that lovely torque and end up with hp by altering rpm

[Guest625101138]

........
40" of prop
thats huge
after reading all day on prop theory Im thinkin that the slow rpms ( 740 is nothing ) should result in higher efficiency

...

The slow rpm is only good if you have the room to swing a big prop.

My original figures were based on a 26" prop, which is about the maximum I thought you would get under that hull with the nominated draft. The best result with this is achieved with 1500rpm at 10kts. The required prop is 26 X 16. You will see the efficiency drops to 57% and the power climbs to 102kW. You start to see the advantage of big slow revving props but the penalty is more draft.

Splitting the power between two props where draft is constrained can be beneficial but then the boat needs to be set up for it.

Rick W

[Boston]

interesting
I just recalculated for a prop of 19" pitch with an engine speed of 880 rpm and a gearing ratio of .75 to 1 with a slip of 30%
that works out to an rpm of 1,173
but again this particular calculator isnt giving me prop diameter

gives me my mull speed at the optimal sustainable rpm range of the engine or about 75% of its available power

I thought that thing said a one meter prop
or 40"

an efficiency of 57% is downright grim
its your ball field but I thought that the normal efficiency range of a well designed prop was in the area of 70-75%

[Ad Hoc]

Boston

ok...so
1) as stated around 1.17ft?
2)...need to select an RPM...that the shaft will rotate at, for your most ideal speed. Either with an existing g/box, or a new one..but you need to select and RPM which you feel happy that the engine will do easily and your happy to let it for many hours..
3) Ok, at what displacement was this..roughly...is it about the same as your boat, if not roughly how much more or less?

Then a rough stab can be made.

As for getting too close to the surface, that where a quick calculation to establish the cavitation number comes into play.

As mydaulphin also noted too, you shouldn't worry too much since too many variables unknown or cant control...so just focus on the principal ones that do affect the design which you have some control over.

The key one being..who will make the prop?..if you are asking a supplier to make one, then all you need to do are these basic calc's to estbalish size and rough pitch and number of blades, then let the prop manufacturer sort out the details....if you are making it, hmmmm...different story!

[rasorinc]

Boston, have you priced a fully automatic hopper bin (fail safe) for your pellets? Also you will need bow and stern thrusters unless you always anchor out. With twin reversibe props operating seperatly you can delete the stern thrusters. I'm thinking what you save in fuel costs you might wind up a slave to your engine room. Also you need to really know your drive system costs. As a builder you know when building your own you keep adding and costs go up by the square factor.

[Boston]

http://www.hillpropellers.com/propcalc.html

is the calculator Im using

ya Im aware of needing to build a automated hopper feed system
no big deal they are all archenemies screws powered by small electrics
Ill use a toiled bowl float as a regulator if I have to but the thing should be simple to manufacture

Im thinking Im going to jam a 22" prop using Ricks numbers and going conservative

but dam that 57% efficiency is a pill to swallow

thing Im really curious about is all the conversions Ive done to get to this point
I started out calculating the joule's of energy used by the original engines and went from there
then I had to consider that the steam engine pounds out torque but at lower HP
bla bla bla
then there was the BTU value comparisons between pellets and diesel and the mass considerations
bla bla bla
this has turned into a bloody project to figure out if the engine size will work out
my initial guess about a month ago was that given that I could gear up the steam engine and use that torque for HP it would turn the appropriate sized prop

Mr Add
check out post # 21
its got the latest relevant answers
I think
this is going to change a lot before I get it all hammered out

oh
as I said
its going to have an electric torquedo thruster 17 hp on it
things not really designed to swivel but it will when Im done with it

[Ad Hoc]

well...57% is dream world stuff...you'll be lucky to get over 50%..i would aim at 45%. But if you wish you use software that just needs numbers, then that is your prerogative.

[Frosty]

When youve built the boat, you then need a propellor to push the boat at the design speed or a little more -what ever you want. The propellor man will then tell you what Hp you will need and what ratio would suit the propellor he has made to push your boat at the speed you want.

You do not choose an engine then a gearbox then ask the propellor man to get you out of the ****.

You are doing it backwards. The horse goes in front of the cart!!

[Guest625101138]

http://www.hillpropellers.com/propcalc.html

...........

Im thinking Im going to jam a 22" prop using Ricks numbers and going conservative

but dam that 57% efficiency is a pill to swallow

......

The 57% was for a 26" prop. If you can only jam in a 22" prop then the efficiency drops to 51% per the attached. So the pill is becoming even more bitter. Power to do 10kts now climbs to 114kW.

So roughly 50% of the hard won power from burning all the pellets just goes into churning the water and warming it up a tiny amount. As you are stoking the boiler you can think of one for the boat and one to warm the water. That starts getting you thinking about efficiency.

Rick W

[Guest625101138]

i.........
an efficiency of 57% is downright grim
its your ball field but I thought that the normal efficiency range of a well designed prop was in the area of 70-75%

It is possible to get prop efficiencies over 90% but you have to have it lightly loaded and this is only possible with an easily driven hull or a massively large diameter prop on a small boat.

You have a relatively small prop on a relatively large boat designed for times when fuel just oozed out of the ground and no one bothered about conserving the filthy stuff.

Rick W

[Boston]

hey Rick I found a calculator that gives me your exact numbers with the engine running at 880 rpm and 150 hp at 895 ft/lb

interesting stuff
Ill send a link in case you want to check it out
things got every bell and whistle you can imagine

http://www.lystsejleren.dk/propel/propcalc.xls

=========================================
Rick the propeller inefficiencies aply to all power sources so I dont think its a black mark on steam

Frosty I gotta design a boat that will hold the engines and type of fuel Im considering so I gotta start somewhere and then double check to see Ive got enough power to do the job
which is were the prop comes in
Im working out some details in rough form so I am sure the hole concept even flies at all ( might just go the way of the Dodo depending on the numbers )
and hey
I've owned lots of horses
even wrecked a few buggies
and yes
several of those wrecks ended up with the horse in front

Addman
I had no idea props were so inefficient
thats crazy

Rick
so there would be a benefit of leaving the prop speed slow and going with a monster prop
I read about that earlier but didnt catch part about light loading
although I like the idea of 90% efficiency Im starting to get the idea that I wont be getting quite that

[Frosty]

So does your deisel fuel go into heating up air then within a split second be pushed out into atmosphere. The piston has to somehow absorb that expansion into reciprocating motion.

I think diesels are only 70% efficient. Petrol is less than that.

[rasorinc]

Perhaps, consider re-designing the bottom of the hull to a deep V. 3/12 up

[Boston]

Frosty
the pellet stoves claim huge efficiencies
Im not even comfortable quoting them until I get some references

the steam is condensed and reused without cooling it to far past the condensation point

and the engine runs way better if cooled and its not in any of the calculations

Ras
I been kicking round the idea of a tunnel in which the prop could spin
its a design consideration ive seen before but would need to research if it becomes evident Im stuck with a prop that offers to little efficiency
Rick suggested originally a one meter prop that was 69% efficient at the rpm of 740 wich also means I could forgo a transmission

Im just working out a few new ways to do some relatively old stuff so if I get a few things wrong in the process or if it seems Im redesigning the wheel
its just the beer talking and Ill see reason in the morning
har har har

cheers
B

[Ad Hoc]

Boston

If you think you'll get 69% efficiency on a prop on that boat, you're doing more than redesigning the wheel...

[Guest625101138]

.......
I been kicking round the idea of a tunnel in which the prop could spin
its a design consideration ive seen before but would need to research if it becomes evident Im stuck with a prop that offers to little efficiency
.......
B

The 22" prop is heavily loaded so benefits significantly from a well designed shroud. The attached shows the potential gain. There would be slightly increased drag with the shrouding but this would be a good solution.

Rick W

[Boston]

way to go Rick
I knew you would come up with something
ok
a 22" prop with a shroud is able to run at 84% efficiency
thats in the range I wanted

ok so one thing about these abbreviations
velocity of rotation in newtons
let me go look that up and see if its anything like RPM
which I need to know so I can calculate HP / torque and know my engine is compatible
ok RPM it is


11669 newtons ended up being 112 hp which is well within the range of this engine at this gear ratio
1600 rpm from 740 rpm equals a ratio of roughly 2.2
so were getting somewhere
matter of fact its so well within the design limit I could throw a few more gear into this system and create an azipod kind of scenario
Ild be eliminating the ruder but adding two geared connections and a swiveling nacelle could be advantageous but that is yet to be determined
also there are structural considerations that may make the system impractical

hp = T ( rpm ) / 5252

[Guest625101138]

..
velocity of rotation in newtons
let me go look that up and see if its anything like RPM
which I need to know so I can calculate HP / torque and know my engine is compatible

Speed of rotation is commonly given in rpm.

Force or thrust is given in Newtons (N).

Torque is given in Newton metres (Nm).

Power is torque by rotational velocity. For consistent units the rotational velocity needs to be in radians per second. rps = rpm/60 * 2 * pi. Torque in Nm times rotational speed in rps gives power in Watts.

Simple really. You do not need to worry about the amount of power a horse can produce or how many British Thermal bits are in the fuel pellets. Get the pellet energy stated in Joules so they are readily translated to watts. A watt is one joule of energy produced in one second.

Rick W

[Boston]

its metric Rick
I went to school when the dinosaurs roamed the earth
and around here that means quarts and ft/lbs and 1/32 inch
this metric thing is killing me

5 meters a second is 11.18 miles an hour acceptable spead at roughly 1/2 the engines peak capacity assuming the rpm is 1600

velocity of rotation as measured over one minute in N certainly has a rpm look to it but I got that its in radians a radian not being one complete revolution
nice touch
there are 6.28 radians pr each 360 degrees
thus 1600 / 6.28 = 254.7 which cannot posibly be right

define velocity of rotation in newtons
and how it related to rpm please

the calculator you used does not relate rpm

1 btu = 1055 J
good wood pellets contain 17,000,000 btu per ton at a cost of $175 to $225 each, works out to about half the cost per btu of diesel but its bulkier and weighs more

41 Kilowatt Hours = 147600000 Joules
pellets get 17 000 000 Btu per ton = 17 935 950 300 Joules per ton so 1 ton of pellets will drive the hull at hull speed for 121.5 hrs

thing is its not the fuel Im concerned about
nor the conversion factor to steam
its the power available from the engine at some reasonable percentage of its max capacity
without the prop rpm I cannot calculate that

[Guest625101138]

To get decent results from the prop shroud it needs to be designed to suit the operating conditions. It is not just a tube surrounding the prop.

It needs to take into account the increase in velocity through the prop. Hence the inlet is larger diameter than the outlet and the outer surface needs to be designed to offer low drag.

There are not many specialist suppliers in the field.

There has been a couple of recent threads on the topic.

Rick W

[Boston]

I read them but didnt participate cause my knowledge is limited in that area
I can make one or have one made once a determination is made as to the best configuration

I need to consider my gearing so I can calculate the hp needed to turn the prop
that boat had two 210 hp engines that produced about 500+ ft/lbs at peak efficiency each
they ran at about 1800 rpm to hit that although the gear ratio is unknown and ate 4.6 gallons an hour each
ends up being 137 kw/h each and 724 Nm also at 1800 rpm each
this was substantially more power than the boat originally had, but thats what they put in the rebuild to get it up to 10 knots cruising and 14 max
so the engine Im thinking of is slightly weaker
but Im willing to pull few tricks to get it up to speed if they work and are not to much torture
the key element that makes me think this engine will work is that when I compensate with gearing for the high torque and low engine speed I get
900 rpm at 150 hp and 900 ft/lb or 300hp at 1800 rpm and 450 ft/lbs which is about what the diesels are except for the torque
torque = kick in the pants or the amount of time it takes you to get up to speed
Im ok with that
I think

I might have done that wrong hp = T ( rpm ) /5252

900 x 1800 /5252 = 308.45 hp so ya I think I did the gearing right

if its not working out with the numbers and the prop size there are other solutions ( although I think I got it pretty close for a efficient set up )
I could go with two smaller steam engines 125 hp each for a slightly lower range but two large screws shrouded and spinning slower
the two smaller engines combined weight is about 500 lbs for the castings where as the one large engine weighs 700 lbs so I would actually be getting a higher power to weight ration
this is one reason I wanted to get things figured out for a single large engine
I like the simplicity of fewer moving parts but there might just not be enough go to a single larger engine

so now we get into two screws instead of one and thats another mystery
besides two smaller props spinning faster are less efficient eh
so it sounds like I want to stick with the largest props I can fit under the boat spinning slowly in shrouds
now were getting crazy

[Guest625101138]

The attached curve will give you an idea of how wasteful it is to push this hull over 9kts.

A shrouded 22" prop only requires 41kW to do 9kts. This is 20% of what is required to do 14kts with a shrouded prop. That extra 5kts means you need to shovel pellets 5 times faster.

Rick W

[Boston]

dam
9 knots it is
thats funny
you want the lines for it

that brings it back into the relm of a single engine again

and no shoveling for me
some guy a few hundred years ago came up with electricity

those guys didnt even remotely need those two huge diesels given that your numbers are bound to be at least in the ball park
and it also means I could move down to a single 50 to 125 hp steam engine using 1/2 the lb/hr of steam and a single boiler system

the 125 hp engine turns at 1500+ rpm eats 1200 lbs of steam pr hour at max and should have 125= T ( 1500 )/5252
125/T= 1500/5252 or
125/t = .28560548
125/.28560548 = T
= 437.67 ft/lb at max output for a 125 hp engine at 1500 rpm

1 hp = .7457 Kilowatts
41 Kw / .7457Kw per hp = 55 hp
that's bloody incredible Rick
course there is an energy loss in there somewhere but still
thats not much to get this thing moving

so the efficiency was 84% so
100/84= 1.19 x 55hp = 65.5 call it 70 hp to cruise at about hull speed of 9,3 to 9.8 knots

thing is Ive got tons of torque at a 1:1 ratio and the larger prop shrouded say 14" advance and 22" diameter going ? rpm provided for a lot of efficiency
velocity of rotation in newtons 1600 1/min = ? rpm
that would have taken me a month to figure out Rick
points to you for being a good sport
B

maybe not
thing wont let me points you
said something about another beer before I can give any more reputation to people
imagine that


1 btu = 1055 J
good wood pellets contain 17,000,000 btu per ton at a cost of $175 to $225 each
works out to about half the cost per btu of diesel but its bulkier and weighs more

41 Kilowatt Hours = 147600000 Joules
pellets get 17 000 000 Btu per ton = 17 935 950 300 Joules per ton
so 1 ton of pellets will drive the hull at hull speed for 121.5 hrs
I think thats bound to be wrong
hmmmm
how about 121.5 x .84% efficiency = 102 hours or 938
still seems like to much
boiler efficiencies in the 90% range are not uncommon
my pellet stove claims an ash remaining of 1% which means there was a near impossible conversion to the gaseous state
to be safe Ill say a 80% boiler and burner efficiency rate combined
102 hours x .8 = 81.6 hours or 751 miles per ton of fuel

at the same speed and revs the diesels would be at there lower limits and burning 1.3 gallons an hour each or 2.6 gallons an hour for both
over 81 hours thats 210 gallons at $3 a gallon or $630
the pellets per ton to go the same distance cost about $175 - $225
although the diesels would most likely be pushing a smaller diameter prop of less efficiency and at a higher rate of consumption per hour to speed along
why, is my next question
instead of bombing around the bay like some fool in rut
how about slurping down a martini and wondering if the girls going to remember she is naked before that sail boat slides past and and there kids start screaming for grand dad to come see

[Boston]

answer is
for the small steam engine
22" prop with a 14"pitch spinning at about ? rpm


next trick is to go back and figure out the metric puzzle and how it relates to prop rpm

Power is torque by rotational velocity. For consistent units the rotational velocity needs to be in radians per second. rps = rpm/60 * 2 * pi. Torque in Nm times rotational speed in rps gives power in Watts.

Simple really. You do not need to worry about the amount of power a horse can produce or how many British Thermal bits are in the fuel pellets. Get the pellet energy stated in Joules so they are readily translated to watts. A watt is one joule of energy produced in one second.

rps = rpm/60 (2)(3.1416)
ok now I see it
somehow I blew right over that when I originally read it
thanks

whats the 2 in there Rick is that what brings me up to the number of radians in 360 degrees
kinda looks like it

1600 = rpm/60 * 6.2832
1600/6.2832 = rpm/60
254.6 = rpm/60
254.6 *60 = rpm
15,279 = rpm

hmmmm and that's got to be wrong
let me guess
rps isnt 1600

rps = radians per sec
velocity of rotation in newtons 1/min then does not equal rps
and once again the metric system nomenclature has kicked my ass

no worries
I want to take advantage of a steam engines ability to run forwards or backwards and run this thing without a transmission so I need to have the rpm's at the naturally occurring rpm range for the hp to drive the hull at typical cruising speed
thus I need to know what the rpm of the prop is
but Ive pretty much got this thing down except for that
my engine rpm at 70 hp is 625 on the big engine
for the large steam engine about 625 rpm so I would need to either recalculate the pitch or gear up the shaft speed
for the smaller engine about 1200 rpm at 94 hp and 900 lbs of steam pr hr is going to be my max cruising power sustainable

Im going to cheat and plug in the known parameters into my best prop calculator
we came up with a 22' prop and a 14" pitch shrouded at 83+% efficiency

calculated for the smaller steam engine spinning at 900 rpm and 70 hp the second set of numbers in { } is for the smaller engine at max potential
engine torque = 408 ft/lb { 438 }
shaft hp at prop = 68 ( no gear box ) { 121 }
prop rpm = 900 { 1500 }
prop torque = 396 ft/lb { 425 }
displacement = 25 tons
wl =57'
speed in knots = 9
speed length ratio = 1.192
shaft hp available = 68 { 121 }
pounds pr shaft hp available = 736 { 412 }
hp required at prop = 70
lb pr shaft hp required = 716
80% of max prop shaft rpm =720 { 1200 }
theoretical required prop pitch = 15.2 { 9.12 }
1) estimates slip of un-shrouded prop = 40.01%
2) estimated slip of shrouded prop = 17%
1) required un-shrouded prop pitch at 9 knots = 21" at 25" diameter rpm = 720 { 15" at 22" diameter rpm = 1200}
2) required shrouded prop pitch at 9 knots = 18" at 22" diameter rpm = 720 { 12" at 22" diameter rpm = 1200 }

way to go Rick your determination of a 22' prop with a 14" pitch is in the ball park ( rpm of ~ 1000 )
I knew you would be perfect for this conversation
cheers
B

[pistnbroke]

I am with frosty I think you are going about this back to front ..If I read this right you have a boat with twin prop shafts with propellers and you you want to rip this out re build the holes and then make another for a single shaft.....crazy .too expensive ..why not stick with the two shafts?? did I read you run this thing with only one engine going .......sounds like 1 steamer and a gearbox / two steamers /one steam and one exist diesel..........too much theory and not enough practical professer commented the students

[Guest625101138]

Running at 1000rpm at 9kts requires 22 x 18 prop per attached.

Rick W

[Boston]

thanks Rick
I figure the calculator I posted was in American Imperial so although I can relate to it better that way. you would probably stick to your own.
thing has a ton of information it gave me though
thanks again for the help

Mr Piston
the boat is still on paper and Im trying to work out some details so that as I bring the design along I will have as few surprises as possible. Im altering the original engines lay out and fuel source and so my take on it is to work everything out before I start cutting up timber rather than after. Its kinda a hobby of mine to work out a few details and then build rather than build a little, tear stuff apart and build a little more, then maybe rip more stuff apart and so on. I got this funny notion that my way ends up faster and better. Work it out ahead of time, build it once.
its got a ring to it

Ive been a general contractor for a long time and once upon a time played with a lot of math so my take on any project is I should be able to stand on the ground looking at the prints and calculate the length, cut and pitch of any rafter hip or peak on the roof pretty much using only a^2 + b^2 = c^2
( even jack and bastard rafters are no problem when calculated so )
and then yell at someone how to cut something.
should end up perfect unless some fool didn't follow the dimensions on the prints

every bodies got there own way of doing stuff
and this is just mine
cheers
B

without looking it up
can anyone tell me the substitute value for 12 if your calculating for a hip or valley rafter on say a 6/12 pitch
( even the carpenters in the squad have most likely have been using speed squares so long they wont get this one )

[pistnbroke]

well there you go then ...when these posts get over a page long often the confusion sets in in the readers mind ....good luck with it

[Boston]

ten pages is about my limit
after that the attention deficit sinks in and I have to come back to it
best
B
and hey
how did you like the boiler idea
turns out pellets are less than half the cost of the diesel pr btu
and everything including the lack of transmission is a huge savings
no gearing necessary and the steam is recycled
engines are about half the cost

Im working on stacking the boilers one on top the other so as to use the preheated exhaust gas of the boiler underneath to assist with the boiler above I can increase efficiency by I think about 20% that way but I need to work it all out
its kinda my next thing to work on but I need to complete the diagrams first

fun fun fun
B

[Ad Hoc]

pistnbroke

You can lead a horse to water....

[Jimbo1490]

If it's steam you want, maybe you should look into a steam engine that runs at higher speeds to begin with.

http://www.greensteamengine.com/licenses.htm

They are also very light weight and compact and look very easy to build, with surprisingly few parts to machine from stock.

Jimbo

[Landlubber]

without looking it up
can anyone tell me the substitute value for 12 if your calculating for a hip or valley rafter on say a 6/12 pitch


NUP, we are boatbuilders not bloody house builders, why would we want to pitch a roof on the boat? We use CAMBER.

[Boston]

Hey Jim
I looked at those early on in my search for an engine type.
The acentric engine designs have a lot of advantages as you pointed out, but they have one huge disadvantage, however, it's obvious when you think about it, they impart huge vibrational forces the there surroundings. The high speed attempts to counteract that but that would mean I'd need a transmission and that's kinda one of my favorite parts to the low speed engines, with the 0-1500 rpm reversible engine being perfect for low speed high efficiency shrouded screws.

Turns out its not the engine thats the tricky part. The have had those down for years, its the boiler thats were you win or loose the game. Looks so far like a monotube boiler running on pellets is only available as a low pressure home system

Landlubber
got you on that one eh

cheers
B

[Jimbo1490]

Boston,

You've hit on the chief advantage for the Greene engine; it operates on ridiculously low pressures and still maintains practicality. His engines will make useful power as low as 2 psi. If you want more power on less pressure, you simply install bigger pistons. This greatly influences boiler design, certification standards and cost, obviously.

Jimbo

[Boston]

Ill go give em a second look
but that vibration looks like a frame killer to me

the lower pressure was why I was looking at em in the first place
but they dont look all that reliable to me with that wonky spin they have
seems like it would shake itself apart

[Jim_Hbar]

Boston:

My engineering education occurred right during the transition between metric and imperial - early courses used metric units and the later, more specialized engineering courses were still in imperial units. Coincidentally, the slide rule disappeared in the same time frame, and hand-held calculators were introduced and became programmable during that time period. Anyway, to the point...

In your posts #37 and #42, it is apparent that you are(were?) confused regarding Rick's use of the units of "N" for Newtons, and "n" for rpm (revs/min, or 1/min), and you are assuming that those n's are the same units - they are not....
n (small case n) is a variable that is expressed in the units of 1/min (revs/min, rpm) and is a measure of rotational velocity.
T (thrust) is a variable (calculated result) that is expressed in units of N (upper case N, for Newton(s)), and is a measure of force - equivalent/proportional to the imperial units of lbf (pounds force), poundals, and slugs.

So in those posts, you are confused (rightly so) on how to convert thrust to RPM.

Please note that it is metric convention to use capital letters for units named after a person ie, Newtons, Watts, Joule, etc.., when you look at Rick's prop summaries, you will see he uses kW for kiloWatts. And it is also convention to use capital letters to indicate calculated values ie: Ricks use of the captital "T" for thrust.

Having lived on the fence between metric and imperial systems for the past 30 years, I've had to understand and use both systems, and deal with the people that are entrenched in both camps.
Really, it is a matter of carrying the units and making sure that it all makes sense, and understanding what the metric "named" units are.

I hope that helps, and doesn't confuse the issue.

Another Jim.

[Boston]

my god I remember slide rules
when I started school I was kinda the idiot savant and ended up in all the higher math classes
the testing process was usually no calculators but slide rules were ok

metric kills me
I know its a better system and once you know it its easier
but
I dont know it very well and hardly ever use it
I do with that the usa would convert to it though
it is easier being base ten instead base anything
thanks
I didnt know about the big N little n

it clearly kicked my ass

glad you noticed

cheers
B

recently picked up two jobs
I have one I'm volunteering at that Im hoping hires me ( fingers crossed its at a very prestigious establishment, they chose about 30 of about 6000 applicants for this position )
its with a bunch of scientists and biologists who work exclusively in metric
the other is exactly the opposite and the guys there would shoot me if I tried to interject anything even sounds like metric

[Boston]

anyone ever heard of a stirling engine

thing leaves the water part out of a steam engine
and just runs on the thermal expansion and subsequent contraction properties of superheated air

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/dtbbeLe2CjM&hl=en&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/dtbbeLe2CjM&hl=en&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>


<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/-UwT0TEv5co&hl=en&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/-UwT0TEv5co&hl=en&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

so far it looks like it wouldnt put out enough power but its got style

[rasorinc]

Any idea what materials (metals) are being used.

[Boston]

nothing spectacular just aluminum and copper is what it looks like

if they were to stick an ice cube on the top of the cold side cylinder it would run like a banshee

Im just not convinced it can be made to pound out any torque

[Jimbo1490]

Stirling engines are quite old yet still maturing. A type of Swedish military submarine (http://en.wikipedia.org/wiki/Gotland_class_submarine) uses a Stirling engine. Stirlings boast the highest thermal efficiency of any engine type, and can have nearly perfect Carnot cycle efficiency. Their chief disadvantage is poor weight to power ratio. A big advantage is that they are external combustion engines so they can burn anything, or even use a non-combustion heat source, like solar. Also, the inevitable engine degradation from combustion by-products simply does not happen, so they are very maintenance free. With no periodic explosions going on or high pressure gases venting, they are also eerily quiet.

Jimbo

[Boston]

The performance of the engine can be calculated a P-V diagram. The volume in the engine is easily calculated by using the internal geometry. When the volume, mass of the working gas and the temperature is decided, the pressure is calculated using an ideal gas method as shown in equation (1).

(1)

The engine pressure can be calculated under following assumptions:
(a) There is no pressure loss in the heat-exchangers and there are no internal pressure differences.
(b) The expansion process and the compression process changes isothermal.
(c) Conditions of the working gas is changed as an ideal gas.
(d) There is a perfect regeneration.
(e) The expansion dead space maintains the expansion gas temperature - TE, the compression dead space maintains the compression gas temperature - TC during the cycle.
(f) The regenerator gas temperature is an average of the expansion gas temperature - TE and the compression gas temperature - TC.
(g) The expansion space - VE and the compression space - VC changes according a sine curves.

Table 1 shows symbols used the Schmidt Theory.

http://www.bekkoame.ne.jp/~khirata/academic/schmidt/img00150.gif

http://www.bekkoame.ne.jp/~khirata/academic/schmidt/schmidt.htm

the real question Jim is
who has a working model of a man sized Stirling engine and or plans for sale of same along with performance data


oh
they are not that quiet
those valves seem to make quite a racket in the videos

and what is the power to weight ratio
cause if I went with this type of engine I would not need boilers ( boilers of the size needed for the engines Ive specified weigh 350 lbs each dry
and I need three of em for engines that only weigh 250 lbs each
ttl weight of the typical steam engine and boiler group that I would need 1550 lbs with a ttl of 250 hp at absolute max and more like 180 ttl sustainable hp
or 8.6/1hp not including water or all the condensation systems

so the constraint of poor power to weight ratio may not be so bad if I knew what it was

[Rangerspeedboat]

Being a steam fanatic on another forum, I can tell you alot about steam engines.

First Stirling engines are known for high speed but no torque. There isnt any application for a stirling unless you want to run a small generator off of steam exhaust.

A good triple expansion steam engine would probably supply enough power for what you want. A triple expansion engine would save steam and not sacrifice too much power.

What kind of boiler were you thinking of using?

I am very interested in this project.

[Boston]

http://www.boatdesign.net/forums/propulsion/these-turbine-alternaters-easy-make-26738-new-post.html

hit the link above and you will see how I ended up at the conclusion that a pellet fired steam engine was pretty much the lowest cost and most environmentally friendly way to get from point a to point b and still be sipping a martini on a yacht

been working out details and am at the boiler part of the problem. I had given double expanding steam engines some thought I had yet to find one in the size range I am looking for

nice to have you drop by

cheers
B

last page of that thread is a good summery of were things ended up so far

nice idea about the steam exhaust
would be a cool novelty piece in the engine room

there is a particularly good explanation of these engines at http://www.google.com/url?sa=t&source=web&ct=res&cd=4&url=http%3A%2F%2Fwww.animatedengines.com%2Fvstirling.shtml&ei=BwD5SfyENMvJtgeWqoCfDw&rct=j&q=regenerator+stirling+engine&usg=AFQjCNFuy9YslDQQztfBFqDGMbE1V30Usw&sig2=NniTp--myDYv7Qa6yp9a-g

[TollyWally]

Boston,
LOL without looking it up, 16.97 or call it 17 in the field. Mr. Swanson was a genius.

[Boston]

lmao
I honestly thought I would stump the whole squad with that one
thats pretty old school there mate
Ill throw you a few points for that one
no one actually knows how to use a square these days
kinda went the way of slide rules

cheers
B


in the 70s Ford made a 180 hp swashplate sterling engine as an experiment to replace some car engine
it worked but they never did anything with it

and there is a french submarine out there with a 1700 hp engine in it

a normal flame will induce rpm of about 3000 in a small 100 Kw sterling engine

[imrankhaled]

any body can say where can i find a 700hp diesel engine with suitable gearbox dxf drawing

[Boston]

and if you add up all those 6.7 billion anybodies you end up in the mess we're in now
there is a brave new world outside the box and I say its a better world
all one has to do is rub a few brain cells together
my two cents
(steps off off soap box and bows)
B

[Boston]

Stirling Powered Ships

the Erickson (sp?) built by John Erickson in the late 19'th century. Unfortunately a big portion of my Stirling engine library is out on loan right now so I can't give you the specifics. If memory serves, the engine was intended to put out 600 hp (447 kW) but only put out about 300 hp (223 kW). The pistons and cylinders were big enough and slow enough moving that a reporter got on them and rode up and down on the pistons.
More recently the French research sub Saga was powered by two 75 kW Stirling engines (200 hp total) and the Swedish military manufacturer Kockums installs two to four 75 kW Stirling engines (~100 hp each) in their submarines. These engines act as "top-off" auxillary engines allowing the submarines to stay stealthy on the bottom for weeks instead of days.

Philips also put a 75 hp (55 kW) Stirling engine in a small cabin cruiser. You can read about that project in "The Philips Stirling Engine" by Hargreaves. Unfortunately it's out of print.

-- Brent Van Arsdell, February 19, 2003

When the Ericsson was built...

I found the right book. The keel was laid in April 1852 and the ship was launched on September 15, 1853. There is a great account of this story and others in "Hot Air, Caloric and Stirling Engines" by Robert Sier. The ISBN # is 0 9526417 12. Published in Great Britain by: L.A. Mair, 20 Pines Road, Chelmsford, Essex CM1 2DL United Kingdom.

the sterling engine seems best suited to electrical generation
so one possibility is to go back to the electric engine powered rather than steam power system but replace batteries as a storage device

[Jimbo1490]

http://www.boatdesign.net/forums/propulsion/these-turbine-alternaters-easy-make-26738-new-post.html

hit the link above and you will see how I ended up at the conclusion that a pellet fired steam engine was pretty much the lowest cost and most environmentally friendly way to get from point a to point b and still be sipping a martini on a yacht


cheers


In terms of what??? There's NO WAY you're going to get lower BSFC numbers with steam than a modern diesel.
BSFC is king because it means less fuel for more power, and also less CO2, soot, wasted btus per HP.

Show me some numbers for BSFC that prove a steam setup is more efficient (and therefore environmentally friendly) than diesel.


Jimbo

[Boston]

there are both calculations on this page and on the these turbine alternators are easy to make thread that clearly show the per penny cost of each btu is cheaper in wood pellet form than in diesel form

the only remaining question is how to apply that cheaper btu to a drive system

the external combustion engine
IE
steam
or maybe the stirling engine
being examples of external combustion

as for carbon contribution
as long as the source of the fuel being burned is grown harvested and used as fuel during the average life cycle of co2 in the atmosphere then the source is carbon neutral
IE
if a tree locks up x amount of co2 in its growth process over say fifty years
and we harvest the tree for fuel
and we know the basic co2 life span in the atmosphere is say 200 years
then the net effect after the 51 or 52 years it takes us to cycle that carbon from atmosphere to plant to fuel to atmosphere to plant is net zero gain in atmospheric carbon
thats carbon neutral

where as if you burn oil that has been sequestered for millions of years adding billions of tons of co2 to the atmosphere that were not previously part of the typical cycle
there is likely to be a dramatic rise in co2 in the atmosphere
as we have had in since the start of the industrial age

for god sakes man
its a no brainer
combustion of a renewable energy source rather than a fossil one is not the premise of the debate
the question was at least
how to best apply power from a low speed high torque engine to the water

been answered
( thanks Rick for the help )

now we have digress sufficiently that I thought I would start a new thread
concerning this new engine consideration

it is not necessary that a particular renewable energy be more efficient than fossil fuels
its that the allure of the convenience be weighed against the detriment to the environment and the value of sacrificing some elements of that convenience for the benefit of our kids
who will be having to deal with the mess we have made of things

cheers
B

[pistnbroke]

Just a thought ..if you have all this torque applied to the prop will there not be an equal and opposite reaction causing the boat to lean??? With such a large craft you carnt just stand to one side of the helm to balance it !!
Perhaps you need to build in a canted deck ..!!

[Boston]

its not that much torque that its a problem
about 400+ ft/lbs at say 80 or 90 hp each engine and say 1000 rpm
just enough to make a big slow prop work perfectly

certainly not enough to transfer so much twist that it becomes an issue

[Jimbo1490]

Boston,

Your explanation of how something is to be considered "carbon neural" is total mental masturbation, similar to purchasing carbon credits. CO2 lasts 5-10 years in the atmosphere, not more. That a fuel is cheaper is another point altogether; you can get lots of free wood, at least right now. But will you get more btuh per unit of soot/CO2 or any other efflux? No way, no how.

Jimbo

[Boston]

looks like there are lots of similar explanations as to the definition of carbon neutral to me

Being carbon neutral, or carbon neutrality, refers to achieving net zero carbon emissions by balancing a measured amount of carbon released with an equivalent amount sequestered or offset. ...
en.wikipedia.org/wiki/Carbon_neutral

Having an overall zero carbon footprint after carbon emissions trading has been taken into account
en.wiktionary.org/wiki/carbon_neutral

that absorbs the same amount of carbon dioxide as it produces
en.wiktionary.org/wiki/carbon-neutral
A product or process that does not add carbon dioxide to the atmosphere over its life cycle.

www.bigskyco2.org/whatisit/glossary
The state of reducing a person’s carbon emissions as much as possible and balancing the remaining carbon emissions by offsetting them with ...
www.dummies.com/how-to/content/green-living-glossary.navId-323612,pageCd-C.html

The idea of helping consumers, organizations, and businesses neutralize their personal or corporate greenhouse gas (GHG) emissions (their ...
www.tcnj.edu/climate/GlossaryofTerms.htm

Entities seeking to become carbon-neutral can: -Limit energy usage and emissions from transportation, buildings, equipment and processes; - Obtaining energy from renewable sources either directly by generating it or by selecting an approved green energy provider, and by using low-carbon ...
www.solardesign.com/library/glossary.php

When a fossil fuel is burned it releases carbon (as carbon dioxide - CO2) that was used by plants millions of years ago. ...
www.altrabiofuels.com/Glossary.cfm

When CO2 emissions of an individual, group, organisation or activity have been entirely "cancelled out" through a process of calculation, reduction and offsetting.
www.mondovisione.com/index.cfm

A company, person or action either not producing any carbon emissions or, if it does, having been offset elsewhere
www.urj.org/green/101/glossary/

Carbon Neutral means offsetting carbon dioxide emissions from everyday life such as from driving and flying, by reducing consumption and utilising alternative energy sources, so that there is no carbon footprint. Alternatively, there are tree planting schemes which help to offset carbon emissions.
www.biomass.uk.com/glossary.php

A voluntary mechanism where an activity, event, household, business or organization is responsible for no net emissions of greenhouse gases and can therefore be declared carbon neutral in that specific area. ...
fsd.monash.edu.au/green/climate-change-glossary-key-terms

A company, entity, or process producing zero carbon emissions.
www.nada.org/green/getinvolved/glossary/

Reducing emissions from all GHG sources produces a carbon neutral result through energy efficiency, renewable energy purchases and carbon offset purchases.
www.emit-markets.com/content/view/32/114
i
s "the potential for net carbon emissions to be zero, all else being equal. For operational activity, this would involve some form of offset, with the question of ‘additionality’ (?? Check) being central. ...
www.epaw.co.uk/carbon/glossary.html

if you read through the thread you can clearly see that the fuel costs per btu have been calculated along with the various efficiencies of various ways of putting those btu's to use

if you want to come back with an informed contrary argument feel free
but the btu to steam % conversion in a domestic pellet boiler system is extraordinary
with good pellet boilers running at an efficiency often in excess of 90%



A good boiler will have an efficiency in excess of 90% and be able to regulate its output to match the heat requirement of the house without losing efficiency. Its necessary that the boiler has some way to measure combustion efficiencies, usually using a lambda probe or equivalent.

The latest generation of boilers fuelled by wood or corn pellets or wood chips are highly efficient, clean burning and totally automatic, saving you time and money. Moreover they use a sustainable, renewable resource, unlike their oil or natural gas fired counterparts.

Pellet and wood chip boilers can be used to provide central heating or process heating for virtually any premises, from a family home to a large commercial or public building or an industrial process. They can be installed alongside, or to replace, existing gas, coal or oil boilers. No modifications to the heating system are necessary.

Today, many of the small boilers on the market use a two-stage combustion process, come equipped with ceramic refractory lining, and are combined with a hot water tank for heat recovery. This kind of configuration allows the boiler to work at optimal load with sufficient air and high process temperatures independent of the heating demand. The result, over the last ten years, has been an improvement in boiler thermal efficiency from an average of 60% to 80-90% and a major drop in emission of products of incomplete combustion.

For a single family house, a pellet boiler of 8 kW (27,000 BTU/hr) will burn 3,200 kg (7,000 lb) of pellets to cover the heat needs over the year. This amount requires a storage space of approximately 5 cubic meters (177 cubic feet).


so it stands to reason that if I combine what amounts to a carbon neutral fuel source with one of the most efficient and simple methods of converting that fuel source to steam and running a steam engine that I would end up with the most btu cost effective and environmentally friendly ratio of btu/hp

diesel on the other hand is in the ball park of 50~60% efficient

from
http://hyperphysics.phy-astr.gsu.edu/Hbase/thermo/diesel.html
For an air standard engine with g = 1.4 , compression ratio rC = 15 and expansion ratio rE = 5, this gives an ideal diesel efficiency of 56%.

you then need to consider a transmission for diesel the where there need be none withe low rpm high torque reversible steam engine and the additional energy losses and costs associated
and the expensive fuel tanks and delivery apparatus that can be replaced with simple and cheep hoppers for the pellets and Archimedes screw type delivery systems that are so cheep and easy to construct DIY

you might also consider that all calculations were for a diesel cost of $3 per gallon and we both know thats only going up
and a pellet cost of $225 per ton

if you then also consider the chance of a boiler explosion ( although modern boilers are engineered to have a safety factor of 4 )
you can maybe see how I then tried to apply a steam less heat engine to the exorcise

you were doing so well Jim
did you miss me over on the climate thread
I kinda took a vacation from the efforts of so many, to convince so few, of the realities of what we have done to our climate
even so
lets keep the boating threads about boating
and leave the climate argument to those who visit the climate thread

if you want to argue the efficiency of an actual steam engine then you need to specify what type of engine with or without cogeneration
the variations being anywhere from 1% to 90% efficient

In practice, a steam engine exhausting the steam to atmosphere will typically have an efficiency (including the boiler) in the range of 1% to 10%, but with the addition of a condenser and multiple expansion, it may be greatly improved to 25% or better.
A power station with steam reheat, economizer etc. will achieve about 20-40% thermal efficiency. It is also possible to capture the waste heat using cogeneration in which the waste heat is used for heating a lower boiling point working fluid or as a heat source for district heating via saturated low pressure steam. By this means it is possible to use as much as 85-90% of the input energy.

beautiful part being that there in a closed loop system not just water need be considered for the transfer medium

and I havent even begun on that posibility yet
and wont until I work out the sterling option

[Jimbo1490]

But ultimately, BTUH is just the beginning of the food chain in a heat/expansion engine, because in the end, we want to spin a shaft to drive a propeller, right?

Boilers may have great conversion efficiency, but unless you also want to make a bunch of hot water to heat a house or some such, the conversion efficiency to SHP is not going to be good. If it were all that, there would still be lots of steam piston engines around, despite all their other eccentricities.

Whenever we see a modern steam powered something or other, it uses a turbine, because you can get good conversion to SHP. Of course the normal 'reaction' type of turbine (with little buckets or airfoils) is very difficult to manufacture.

But there is another type of turbine that's fairly easy to build and has surprisingly high conversion efficiency. It was invented by Tesla and aptly named Tesla Turbine (http://en.wikipedia.org/wiki/Tesla_turbine)

Now that would be a novel way to power your boat! Your project would make all the industry rags for sure!

Jimbo

[Boston]

dam Jim thats a great idea
let me see how its stacks up and if anyone still produces them

low rpm and high torque is ideal for a transmission's system so if the turbine is ultra high rpm as most are then it will present practical difficulties

although Im starting to lean back towards an electric engine running on a bank of Stirling generators
simple and no boiling water and so 10% loss of energy just in the conversion process
also I could run the Stirling generators directly to the electric motors with only a few batteries to buffer the load variations
so Im almost back to were I started from with the electric instead of steam configuration

[Boston]

way to go Jim
I like this thing
would make a great generator power source
runs on low pressure steam or air
and dam simple to construct

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/yk-_IGd4xYE&hl=en&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/yk-_IGd4xYE&hl=en&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/E30md1iPUfQ&hl=en&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/E30md1iPUfQ&hl=en&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/Yf7vgq3vyGA&hl=en&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/Yf7vgq3vyGA&hl=en&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

or could run on low pressure steam
the bigger ones seem to run at about 1000lbs inlet pressure

[Rangerspeedboat]

I have seen those videos, I like the simplicity of the tesla turbine. You could run that off the exhaust of a steam engine, save steam and make power.

Whats going on with the steam engine idea? are you using an engine to power the thing or a electric motor powered by a steam engine?

[Boston]

well Im still working things out so I know what my design parameters are
the only thing the steam engine has going against it at this point is the high steam pressure requirement
I found one new cost 2000 for the castings ( I have a machine shop available to me )
it puts out 125 hp at 400+ ft/lbs and 1500 rpm max and 600lb working pressure
Ild need two of em and they would need three boilers ttl
the ttl weight of both engines and boilers is about 1550 lbs not including water

so that is the bench mark that an alternative system will have to meet in order to be seriously considered
thing is the lower I can get that steam pressure the happier I am

the Sterling engine seems to be a gutless wonder in terms of power so Im now on to considering the T turbine
thing is the Stirling runs on heat
the T requires steam and so boilers

should it not be practical to adapt either engine to meet the capabilities of the typical steam engine

then Ill just go with the original steam engine idea
speaking of which
do you know who makes a new triple expansion steam engine in the 125 hp range

[Rangerspeedboat]

I dont know where to get a 125 hp steam engine, but I have an idea that has been tested and will probably be much cheaper than buying a steam engine.

Converting a 4 cycle gas engine to steam. A new head and cam, and viola. Complete with oil pump and water pump. Get one out of an old car in a junkyard, then just do some modifications. It would not be double acting, but the 4-8 cylinder would make it as powerful. It can withstand the pressure, be replaced with ease, and parst are readily avaible at a low cost.

This has been done before, it powered a car though.

If you want more info, just ask. I can basicly explain the whole process, I have done this conversion with much success on a small 2 hp and 5 hp briggs.

[Boston]

whats the steam pressure required to give the needed 125 hp for say a chev. 350

[Jimbo1490]

The B/S and especially R/S ratios will be WAY wrong for anything like optimum performance if you try to convert a gasoline engine over to steam. Maybe a low speed stationary diesel, maybe, since it will have a long stroke and long con rods. But a gasoline engine will suck for steam. I'm not saying it won't run; it will run. It will just be very sub optimum.

Jimbo

[Guest625101138]

whats the steam pressure required to give the needed 125 hp for say a chev. 350


On the basis that the head is replaced to give power on every downstroke, you only need 625kPa at 1800rpm. If you want the power at slower revs then increase the pressure in proportion to change in revs.

Will require about 3000kg/hr of steam so something like 10% overall efficiency.

Rick W

[Boston]

and so died the idea of converting an engine
I think the Stirling engine idea died as well

seems the triple expansion steam engine is closing in on being the winner with maybe a bank of Tesla Turbine generators powering an electric engine running a distant second
the T turbines are unbelievably noisy according to everyone who mentions what they sound like
and Im after some peace and quiet
although it may be possible to balance the load with the input pressure to reduce the rpm sufficiently to eliminate the noise issue
but T turbines tend to develop hp and have low starting hp ( like nearly non existent )

I saw a performance chart for a test series of T turbines
a set of I think 15 plates spaced at .02 inches and 12 inch diameter at an unlisted working pressure resulting in 10,000 rpm yielded about 20 h
T turbines have varying efficiency claims from 60~90%



the efficiency of the steam engine is all about the condenser and single, double or triple expanding design
it takes 972 btu to vaporize water at 100C
if the engine uses 1200 lbs of steam at max 1500 rpm and 125 hp then it takes 1,166,400 btus per hour to feed and produces at 125 hp or 318,000 btu
or 27.5% efficient for the reliable steam enigne companies single expansion 125 hp engine running a 100% efficient condenser
Im off to find a triple expansion engine

I think the goal needs to be to find an engine of at least 35% efficiency in order to keep the system on pace
or at least on pace to outperform diesel monetarily
from an environmental standing any carbon neutral energy outperforms a fossil fuel source

the diesels in the elco 57 flat top rebuild were 6BT5.9-m
at 1400 rpm had 134 hp and ate 2.7 gallons pr hour
134 hp = 746wx134 = 100,000 watts out and
2.7 gallons diesel contains 130,500 btu per gallon or 352.350 btu's ttl = 352,350 x 0.293 = 103,238 watts
100,000 watts out and 103,238 went in
dam I did something wrong
or these guys lied about there fuel consumption/power output
diesels typically have an efficiency of about 40% if I remember it and at best maybe 60

For an air standard engine with g = 1.4 , compression ratio rC = 15 and expansion ratio rE = 5, this gives an ideal diesel efficiency of 56%.

Engines using the Diesel cycle are usually more efficient, although the Diesel cycle itself is less efficient at equal compression ratios. Since diesel engines use much higher compression ratios (the heat of compression is used to ignite the slow-burning diesel fuel), that higher ratio more than compensates for the lower intrinsic cycle efficiency, and allows the diesel engine to be more efficient. The most efficient type, direct injection Diesels, are able to reach an efficiency of about 40% in the engine speed range of idle to about 1,800 rpm. Beyond this speed, efficiency begins to decline due to air pumping losses within the engine.

logic being that if the pellet fuel costs half as much the engine can be half as efficient before it becomes financially disadvantageous to use in place of diesel

ergo a diesel of 40~60% efficiency could be replaced with a steam engine of 20~30% efficiency run on pellets
the engine being considered having a max efficiency of about 27.5% with a return condenser temp of 100C

dam
looks like its working so far

so
why did the efficiency calculation of basic energy in and energy out not work when run from the industry provided numbers

[mydauphin]

I think the steam engine was replaced because the fuel took to much space in the ship. In other words unless your build a freight train with various fuel cars or a ship willing to sacrifice 50% of its volume to fuel, your not going to get very far... I think batteries potentially can store more energy per cubic foot than power pellets. Something to think about. There are many forms of efficiency.

[Frosty]

There is quite a bit of kick in a tube of tooth paste. I ran out of deoderant and I err put some under my arm pits, well we live and learn.

I not saying you can run a car off it,--can you?

[Boston]

I worked out the volume issue way earlier
I think its twice the volume per btu
pellets are ~64 cubic feet per ton at 17~22 million btu per ton
the boiler is 90% efficient
the prop is 85% efficient
there is no transmission
and the engine is 27.5 % efficient as a single stage single acting engine with subsequent designs getting substantially more than that
but for the sake of this study I went with a readily available simple inexpensive steam engine produced locally and using common off the shelf components in the rotating assembly

diesels are about 40% efficient and require a transmission
transmission is say 95% efficient but expensive
prop is 85% efficient for the slower turning steam engine but the diesels faster turning prop will be 50~60% if the norm is followed
and the fuel tanks for obvious reasons need to be big and heavy to hold a ton of fuel, also very expensive
a ton of fuel = 300 gallons

Im considering this application of alternative fuels for an elco 57
which has tons ( har har ) of room so fuel volume is less of an issue

so far baring a few more things to work out
its cheaper to install
cheaper to run
cheaper to maintain
and better for the environment

http://maggiesfarm.anotherdotcom.com/uploads/elco57.jpg

given that the fuel is bagged rather than liquid form it can be fit into every nook and cranny the vessel has to offer without the expense of huge tanks or expensive delivery systems and pellets are clean, you can spill em and no big deal they stoke themselves from hoppers that are automatically filled

yup there are some draw backs but at half the cost per btu of diesel considering diesel at $3 a gallon (which it wont be at for long) the steam engine can be half as efficient and the steam engine still has advantages if you are willing to tolerate the disadvantage of bulky but safe cheap fuel and a roaring fire in the belly of the beast. not to mention the chance of explosion

I say change is good and thinking outside the box is even better
diesel wont be round for much longer
if we are lucky fossil fuel will run out tomorrow
pellets are completely renewable and available on nearly every continent
cheap

If it works out that a pellet fueled boiler can be made to run an economical energy transfer system then its worth doing it simply because its cheaper per btu for the fuel.


toothpaste as deodorant eh
Ild have gotten you a pint were we in the pub and you told me that story

as for running a car off it
think of it this way

why did the audio industry bring us up through all the nifty gadgets to play our music on and then once they had sold us a new system every ten years or so finally introduce what they had forty years ago
music stored on a chip
they wanted to be able to sell you a new system on a regular business
why
its a business

same way the automobile companies are going to introduce complex unnecessary technology in an effort squeeze as many sales out of a trusting and hopeful public

when a simple cheaper but technologically inferior solution is likely to, or probably already has presented itself.

its a sales gimmick to laud the conveniences of the norm in order to maintain the status quo
the status quo being the perpetuation of the oil and gas guzzling engines

there are alternatives
they will be found
and they will be found by people who look for them
and not by the beneficiaries of the status quo

my two cents

[TollyWally]

I sure appreciated those clips of the tesla turbine. I've been fascinated with those things for years but it is hard seperating fact from fiction when dealing with Tesla. A brilliant yet eccentric fellow.

[Boston]

guy was a whack job
swore off woman and said they distracted him
were he standing in front of me Id tell him "pull your head out man, they distract all of us, thats what the're here for"
that and beer baseball and boats

he disillusioned his investors with wild claims that although probably he was capable of pulling it off
he should have saved for a more advantageous moment
basically he was the worlds worst business man and died broke after most of his inventions had been stolen by others