The Steampunk Forum at Brass Goggles
December 15, 2017, 06:46:14 pm *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with username, password and session length
News: Support BrassGoggles! Donate once or $3/mo.
 See details here.
 
   Home   Blog Help Rules Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: Steam science questions???  (Read 1328 times)
Redranger90
Deck Hand
*
United States United States


Steady as she goes!


« on: February 03, 2012, 04:00:39 pm »

Here's a question for some of the more engineering savvy  people who reside on this site.

Im planing on constructing a steam engine to possibly drive a number of things. I'm looking to get somewhere along the lines of 50 hp or close to. Problem is, I'm finding it hard to locate all of the math I need. I suppose what I'm asking is, at what cylinder bore with how much water boiled and with what kind of psi can get 50 hp at about 1000 to 1500 rpm, or are those numbers completely out of whack?

As well, I was thinking of what would be the easiest and most efficient means of a pressure vesicle, and I believe an enclosed boiler matrix would be a good idea, using heavy duty steel pipe, any suggestions or thoughts?

Also, I say a number like 50 hp, but I believe I is the torq that is more important, and I am looking for something along the lines of 80 ft/lbs.

This project is still in the early development stages, and I am still open for ideas and critiq, as well as open to collaboration.
Thanks,
Redranger 90
Logged

The original Redneck Steampunk
Mr. Boltneck
Zeppelin Admiral
******
United States United States


« Reply #1 on: February 03, 2012, 04:11:17 pm »

If you look around on Google Books, Gutenberg.org, and the like, you can find books from the early 20th and late 19th Centuries which deal with steam engine and boiler design, along with the related technologies like pumps and injectors. Some of these books have sections on estimating jobs, that is, figuring out roughly what sort of resources are needed to operate under a given set of conditions. There is also a reprint available of the old International Correspondence Schools book Steam Engine Design and Mechanism which has a fair amount of formulas and rules of thumb for working out the sizes of each element of a steam engine.
Logged
Narsil
Immortal
**
United Kingdom United Kingdom



WWW
« Reply #2 on: February 03, 2012, 04:53:09 pm »

Working from first principles:

(1) the force on the piston is the pressure in the cylinder multiplied by the area of bore. Depending on how your valves work the pressure may vary throughout the stroke, particularly at higher rpm.

(2)The torque is this force multiplied by the effective throw of the crank.

(3)The rate of steam consumption per cylinder is the swept volume of the cylinder multiplied by the rpm.

(4) The power is the torque multiplied by the angular velocity(ie rpm expressed as radians per second) of the crankshaft.

Now these figures are only really a starting point and there are quite a lot of other factors that they don't take into account, but they should at least give you a rough order of magnitude as a starting point. There will also be significant other losses from pumps, condensers etc these ancilliary power drains are considerably greater than in an IC engine for example. The other major complication is that if it gets too cold steam stops being a compressible fluid and turns back into a liquid.

Now one consequence of (1) is that you can get the same force from lower pressure steam by increasing the size of the cylinder bore. So using multi stage expansion, exhausting the first cylinder into one of larger bore can dramatically improve efficiency since you get to extract a lot more of the energy that you put into turning it into steam in the first place.

In terms of boiler performance you really need steam tables to start doing those calculations, these relate energy, pressure and temperature for steam and water vapour.

Logged







A man of eighty has outlived probably three new schools of painting, two of architecture and poetry and a hundred in dress.
Lord Byron
Drew P
Zeppelin Admiral
******
United States United States


« Reply #3 on: February 05, 2012, 05:56:15 am »

Dammit you're good Wink Smiley
Logged

Never ask 'Why?'
Always ask 'Why not!?'
Uncle Arthur
Zeppelin Captain
*****
United States United States



« Reply #4 on: February 21, 2012, 09:15:36 am »

Narsil? Can I swim on over to The UK and hang out in your shop for a couple weeks? My engineering training is all of the ' What part can I cobble in to this piece of junk to make it work without killing me" type.
Logged

If at first you don't succeed , CHEAT!
Kevin1632
Snr. Officer
****
United States United States

Steam breakfast of Champions


« Reply #5 on: April 20, 2012, 05:23:56 pm »

Here is what I use,

http://www.catskillarchive.com/rrextra/toc.Html

Notably chapter 26 has the math.

Steam has 100% torque at 0 rpm, Jay Lenos Doble steam car has a 20 hp engine and accelerates 0 to 75 in sixty seconds. BTW the car weighs 6000 lb.

Regards,
Kevin



Here's a question for some of the more engineering savvy  people who reside on this site.

Im planing on constructing a steam engine to possibly drive a number of things. I'm looking to get somewhere along the lines of 50 hp or close to. Problem is, I'm finding it hard to locate all of the math I need. I suppose what I'm asking is, at what cylinder bore with how much water boiled and with what kind of psi can get 50 hp at about 1000 to 1500 rpm, or are those numbers completely out of whack?

As well, I was thinking of what would be the easiest and most efficient means of a pressure vesicle, and I believe an enclosed boiler matrix would be a good idea, using heavy duty steel pipe, any suggestions or thoughts?

Also, I say a number like 50 hp, but I believe I is the torq that is more important, and I am looking for something along the lines of 80 ft/lbs.

This project is still in the early development stages, and I am still open for ideas and critiq, as well as open to collaboration.
Thanks,
Redranger 90
Logged

Utilitarian Prototype
Snr. Officer
****
Denmark Denmark


Trust me - I'm a Marine Engineer


« Reply #6 on: April 22, 2012, 06:46:51 pm »

Also some sort of cylinder lubrication should be considered to avoid scuffing, and the fact that things have a tendency to expand in the heat, a lot of stuff must be taken in to calculation, just so you avoid putting the contraption together and having it seize up or explode
Logged

Marine Engineer 2nd Class STCW III/2 and V/1
Professor J. Cogsworthy
Zeppelin Captain
*****
United States United States


Aude Aliquid Dignum


« Reply #7 on: April 22, 2012, 06:49:07 pm »

Also some sort of cylinder lubrication should be considered to avoid scuffing, and the fact that things have a tendency to expand in the heat, a lot of stuff must be taken in to calculation, just so you avoid putting the contraption together and having it seize up or explode

I wonder if a turbine style engine would be safer for the beginner hobbyist to build and still give enough power to do something
with it.

( not trying to talk you out of this just letting my mind wander... )
Logged

No, no no, a thousand times no. Its pronounced - lah-BOHR-ah-tor-ee
Utilitarian Prototype
Snr. Officer
****
Denmark Denmark


Trust me - I'm a Marine Engineer


« Reply #8 on: April 22, 2012, 07:12:11 pm »

Turbines can be tricky too, you need to get the blades right plus the angle created by the the diminishing wheels in relation to the inside of the housing. Also the gaskets to avoid steam leaking in disproportionate amounts, and a whole slew of other things.

I am by no means trying to discourage anybody at all either, quite the contrary, I applaud almost any attempt at engineering, but also remember that working with steam you are working with great powers so caution is advised  Wink
Logged
Narsil
Immortal
**
United Kingdom United Kingdom



WWW
« Reply #9 on: April 22, 2012, 07:48:14 pm »

While not impossible a steam turbine is certainly starts much more towards the high tech end than a reciprocating piston engine.

A piston steam engine can be made to work acceptably well with fairly slack tolerances as they work at relatively low speeds turbines on the other hand need to rotate at very high speeds to work at all which puts much greater demands on manufacturing quality in terms of things like balance and bearings. When they do break it is likely to be quite catastrophic since a turbine rotor is essentially a high speed flywheel covered in knives.

The other issue with steam turbines is that they need very dry steam, any droplets of water which condense out will erode the blades very quickly indeed and this adds considerable extra complexity to the whole cycle.
Logged
von Corax
Squire of the Lambda Calculus
Moderator
Immortal
*
Canada Canada

Prof. Darwin Prætorius von Corax


« Reply #10 on: April 23, 2012, 03:01:09 am »

You could also try building a Tesla turbine; much simpler, lacks the knives Narsil mentioned, and apparently has a tendency to not explode during a rotor failure.
Logged

By the power of caffeine do I set my mind in motion
By the Beans of Life do my thoughts acquire speed
My hands acquire a shaking
The shaking becomes a warning
By the power of caffeine do I set my mind in motion
The Leverkusen Institute of Paleocybernetics is 5838 km from Reading
Utilitarian Prototype
Snr. Officer
****
Denmark Denmark


Trust me - I'm a Marine Engineer


« Reply #11 on: April 23, 2012, 11:25:18 am »

I must agree with Narsil, a turbine, while not impossible requires vastly more caution and engineering knowledge than a reciprocating steam engine, as they do tend to fail spectacularly if not made and maintained to a very high standard.
Logged
Professor J. Cogsworthy
Zeppelin Captain
*****
United States United States


Aude Aliquid Dignum


« Reply #12 on: April 23, 2012, 01:14:24 pm »

Oh... ok. Thanks for the answer.


While I'm not sure it scared me enough to never try one myself, the exploding water
heater from Mythbusters has given me a healthy respect for the power of trapped
steam.
Logged
von Corax
Squire of the Lambda Calculus
Moderator
Immortal
*
Canada Canada

Prof. Darwin Prætorius von Corax


« Reply #13 on: April 23, 2012, 03:09:28 pm »

Tesla. Turbine.

Seriously. Search Instructibles; you'll find a crapton of Tesla turbines, probably a metric craptonne of them, mostly using old CDs for the rotors.

Does anyone besides me remember the, er, "anti-hysteria device" which showed up two or three years ago, that was powered by a Tesla turbine whose rotors were spent Dremel cut-off disks?
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.20 | SMF © 2013, Simple Machines Valid XHTML 1.0! Valid CSS!
Page created in 0.269 seconds with 17 queries.