Looking for stationary steam engine power formulas

I remember in my physics class a formula called PLAN

P pressure in pounds per sq inch

L length of piston travel

A Area of piston

N number of strokes per minute

There might have been a constant to convert it to horsepower.

it's in all the old texbooks

Keep in mind that if its a double acting,engine,. the area on one side of the piston is diferent than the other because of the area of the piston rod that has to be subtracted. I remember that because I failed an exam because of that.;

Snakers

"Keep in mind that if its a double acting,engine,. the area on one side of the piston is diferent than the other because of the area of the piston rod that has to be subtracted. I remember that because I failed an exam because of that."

So. . . what if you deliberately increase the size of the piston rod until the ratio between the two cylinders is oh, say 1:2.25? Then you'd have the HP and LP cylinders in the same bore.

Then put the same thing on the other end of the piston rod with a Scotch yoke in the middle: http://en.wikipedia.org/wiki/Scotch_yoke

Now, put three of those on the same crankshaft at 120 degree offsets. That's four moving parts (not counting the valves.)

Mark -- Books on steam engine design published in the 50 or so years spanning year 1900 show up on ebay all the time at fairly low prices. Find one and study the subject of indicator diagrams. The valving of steam engines makes a difference in pressure and is hard to calculate from geometric information. So indicator diagrams that measure pressure vs. piston displacement are the way power is calculated. Also the older editions of mechanical engineering handbooks like Marks(6th or earlier, the earlier the better) treat the subject at a concise level that you should be able to follow.

Ed Weldon

I do not know how much i can directly help you- but you might want to look into the properties of steam, particularly in its relationship to pressure and temperature. You will need to know the energy imput in watts, the volume of water to be heated and to what temperature- as this will determine the pressure of saturated steam.

You should end up with something like 7929.49 seconds ( 132.158 minutes) to create 1450 psi steam of 29.28 cub inch of water @ 344 watt input

The pressure of the steam will determine the volume of space it displaces and how much water you will need to supply a desired output.

Superheated steam, saturated steam are some common names and most charts will list enthalpy and other good stuff you will need to dig through- and be ready for lots of conversion between bar, pascals, and psi.

As long as you are building a steam engine how about a solar powered steam engine? I read a story about one in a book that I think was titled "Modern Inventions" printed about 1900. This guy had built a parabolic structure lined with hundreds of mirrors aimed at a boiler in the middle. It beared an uncanny resemblance to a modern radio antenna that astronomers use. Its output was about five horsepower.

Thanks for the advice. I actually found some good texts on Google Books. Wow, take public-domain techincal books, scan them to .pdf and post them to the web.

As to the solar-powered steam engine, that sounds like a lot of capital investment for a small return.

For steam fuel, there is an organic technology device that uses solar energy to convert CO₂ from the atmosphere and water into the stable hydrocarbon C₆H₁₀O₅. The device is self-replicating and self-maintaining. I think it's called a "Tree".