Steam turbine- stages, how much expansion?

[Jkrych]

Looking to pair a boiler to an engine to extract about 7 or 8 mechanical horsepower. Will be flash steam design, and will only need to supply maximum steam for approx 90 seconds or so. Thought about a traditional piston style, but I have rpm requirements that will place a piston design out of practicality- thus a turbine would be the best choice (I think). I'd like to get as much out of the steam as I can, so a single stage is out- BUT, I don't know what the increase in size(volume) should be in the turb to accommodate the steam expansion per stage. Anyone have some formulas or a link to some info that could steer me in the right direction?

 

[lohring]

I'm assuming you're building model turbines, not engineered turbines for commercial use. If so look at this:
http://xgjfet2zp.surge.sh/model-ste...for-model-makers-classic-reprint-jfet2zp.html

Lohring Miller

 

[Jkrych]

Thank you for the link. I have that very book on my kindle but most of the arithmetic has not survived the transfer from print to digital, and is unreadable. there is however a great example of simple construction of turbine wheels and an example of multiple pass turbine construction(albeit only a picture).

Perhaps a small 2 stage turbine suitable for testing is in order.