I Made an Ofeldt Boiler Calculator/Simulator

[Jasonharker]

Hello Everyone!

My name is Jason. Thank you for letting me join! I have long been interested in steam engines and boilers and I come froma background in Model T engine rebuilding and programming. I'm currently working on building my first boiler, which is an ofeldt boiler. I have tried to gather information online, and from various old books and put them into a single working 'calculator' that helps me design and understand how the boiler will perform.

https://hardlyhumanfx.com/ofeldt_calculator.html

I would really appreciate it if you knowledgable fellows could please play with my calculator and tell me if the outcomes line up somewhat with reality. I would really appreciate the feedback. There are 3 tabs. Tab 1 is boiler specifications. Tab 2 is engine specs and water pump specs. Tab 3 is Simulation where you can test how it performs over time. The system assumes one is using propane as fuel, as my first iteration will use that for simplicity. Full disclosure, I'm not building a boat but a little buggy. But you folks are really the most knowledgeable and active steam people around! I'm still learning how to use your forum so apologies if I am a little slow.

Thank you again!

Jason

boilerscreen2.jpg (120.13 KiB) Viewed 64711 times

[fredrosse]

Your work here is quite good, using the older conventions for steam engine sizing and performance, with only single expansion engine types. I do have some suggestions relating to your program:
1. The sliders for defining various inputs (bore, stroke, etc.) limit the user to fixed values, and I would guess that the majority of these parameters would not match the parameters of current build projects. Why not just allow the user of the program to just type in the values, rather than using limited range sliders? I have known real steam engines having a bore as small as 0.125 inches, and up to 98 inches. While these extremes are indeed unusual, why limit your program with a short range of values? Both of my current steamboat engines will not fit into your program.
2. Engine displacement is given as “gallons”. As far as I have ever seen, engine displacement is given as “cubic inches” in the USA, or “Cubic Centimeters / Liters” in Europa. As an aside, Gallons is undefined unless you specify “US Gallons” or “Imperial Gallons”.
3. Engine types are limited to “Single or Double Acting” plus “Single or Double Cylinder”. While this covers many engines, why not allow the user more latitude here. I am currently building two engines, one a three cylinder 1000cc machine, plus a 3 liter 5 cylinder machine, but your program does not allow these to be evaluated.here. In the “PLAN” formula, the parameter “N” is the number of power strokes per minute, please just allow the user to input this value.
4. It is not clear to me as to how the maximum boiler pressure is determined. Is this based on some allowable stress? Copper tubes? Steel Tubes? Drum or tubes or drum heads? The several parts of boiler design all require proper strength calculation, and should be defined rather than just giving a “Maximum PSI”.
5. Steam exhaust pressure has a performance influence, but I did not see this as an input parameter.

[Jasonharker]

Your work here is quite good, using the older conventions for steam engine sizing and performance, with only single expansion engine types. I do have some suggestions relating to your program:
1. The sliders for defining various inputs (bore, stroke, etc.) limit the user to fixed values, and I would guess that the majority of these parameters would not match the parameters of current build projects. Why not just allow the user of the program to just type in the values, rather than using limited range sliders? I have known real steam engines having a bore as small as 0.125 inches, and up to 98 inches. While these extremes are indeed unusual, why limit your program with a short range of values? Both of my current steamboat engines will not fit into your program.
2. Engine displacement is given as “gallons”. As far as I have ever seen, engine displacement is given as “cubic inches” in the USA, or “Cubic Centimeters / Liters” in Europa. As an aside, Gallons is undefined unless you specify “US Gallons” or “Imperial Gallons”.
3. Engine types are limited to “Single or Double Acting” plus “Single or Double Cylinder”. While this covers many engines, why not allow the user more latitude here. I am currently building two engines, one a three cylinder 1000cc machine, plus a 3 liter 5 cylinder machine, but your program does not allow these to be evaluated.here. In the “PLAN” formula, the parameter “N” is the number of power strokes per minute, please just allow the user to input this value.
4. It is not clear to me as to how the maximum boiler pressure is determined. Is this based on some allowable stress? Copper tubes? Steel Tubes? Drum or tubes or drum heads? The several parts of boiler design all require proper strength calculation, and should be defined rather than just giving a “Maximum PSI”.
5. Steam exhaust pressure has a performance influence, but I did not see this as an input parameter.

Hi Fred! Thank you for the feedback! If you go to the calculator now, you will see I have edited it with your suggested changes. https://hardlyhumanfx.com/ofeldt_calculator.html Since your feedback was user interface heavy, I assume the rest of the calculator seemed to be behaving close to real world expectations for the boiler? I appreciate it!

[fredrosse]

A couple more suggestions:
1. In the PLAN/33,000 = HP, to determine "N"

A. Engine Number of cylinders Input (any Integer value)
B. Single or Double acting (gives a value of 1 or 2)
C.Design RPM (any value)

Calculated Value, N = A x B x C

The path delineated above is a clarification for some, or you could just ask for the number "N" (Number of power strokes per minute) to be directly input.

2. Allow direct input of engine RPM without slider input limits.

3. The requested "Number of faces", I presume you mean the number of piston faces recieving steam pressure per revolution of the engine? If so,please define this within the program, and also check your math.

4. Steam consumption per horsepower-hour. The best I have seen in single acting steam engines is about 21 LBm/HP-hr for a uniflow engine. The realistic maximum for a decent engine of about 50-60 PPH/BHP (Pounds Per Hour / Brake Horsepower )

Best wishes and good luck.

[addiator]

This is very interesting and impressive. As someone who dabbles in the thermodynamic modelling of engines and other things professionally I think it would be interesting if you shared how it works on the back end - what formulas and calculating procedures were used. I am especially interested in how the heat transfer is evaluated in the boiler and if wall effects are taken into effect in the engine? How is the dynamic simulation performed?

I also think it would be useful if a metric version existed. I personally cannot wrap my head around imperial units.

Very interesting project indeed. I love this.