Seeking advice regarding turbocharging monotube boiler.

Hi there, folks! I've been working on a steam engine and boiler for awhile now, and in the process of that I've had an idea I wanted to run by you guys to see if it's worth pursuing. My boiler is a straightforward monotube design. I'm using a blower converted from an automotive turbocharger that draws a fuel/air mixture through a carburetor, then ignites it in a ~5' tube.

If I were to pipe the steam line into another turbocharger's turbine housing (I would also have to fit a 12v pressure pump to pressurize the turbo's bearings with oil), I could spool it up and force quite a lot more air through the system, and generate a much hotter flame. I could then adjust the turbocharger's wastegate to open at a certain air pressure to let the steam pass freely once the desired airflow is achieved. The crux of my question is this: would doing so consume the energy in the steam, and not leave enough for the engine to run on? Do you think I would need to plan on reheating the steam to prevent condensation?

Thank you for any ideas and feedback you may offer!

I use a lief blower, it puts out enough air for combustion so far.
If you preheat the fuel enough you don`t need a carb.
Don

Hi Aristophonese,
You present an interesting question. I'm wondering what is the purpose of the steam engine? If it is for a stationary power unit or some steam powered vehicle.

Your question has a simple answer, if you use the exhaust steam from the engine to the turbo...it's a good idea. Any work or expansion before the engine is not gonna work very well. This is true even with a reheat.

Another idea that is tried and true is the steam blower. Please see the following link: Loco exhaust

I use a similar device on my steam powered scooter:
Rick's Steam Powered Scooter
Click on the picture to enlarge the video.

Let me know your thoughts?

Kind regards,
Rick

Don, I opted to use a carburetor because I was having a hard time getting the mixture right and finding an appropriate pump that was gasoline safe to push fuel through the spray nozzles. There is a lot I wasn't understanding. I'm a car guy, so I get carburetors. That, and the carburetor's ability to throttle the flame, were the reasons I went that route. Perhaps the whole thing could be a lot simpler, though!

Rick, this particular engine is for a car I'm building. I was hoping to be able to feed air to the boiler from the turbocharger so that I could simply shut off the electric blower and have it essentially self sustain, so long as fuel and water were available. I'd have to redesign my piston valve to harvest the exhaust, so perhaps this is an idea to save until I'm ready to redesign some more aspects of it.

Thank you for the feedback and knowledge!

Aristophanese
One more addition to the Turbine side. Use the burnt gas exhaust from the mono-tube boiler to the turbine along with the steam exhaust from the engine. Use the steam with a nozzle to help draw the gas exhaust into the turbine. Maybe even use a de Laval nozzle...you can look it up in google if interested.

Note that one thing that really brings a boiler to life is increasing the hot gas flow through it. A little technical explanation is that it increases its Reynolds number, turbulence, which greatly increases heat transfer.

On a personal note and as a BSME since 1984, it took me 9 years to build the Steam Scooter pictured above. This is a clean sheet design. I had many failures. My advice is to start with something smaller like a go-kart, bike or 3 wheeler to perfect the burner and mono-tube boiler. I'm just now starting my car build with the knowledge learned albeit the hard way in the Scooter Design. To start off building a mono-tube boiler with a clean sheet design is going to be challenging and think of the cost/effort to change on a full size car. Please don't miss understand me and I'm not trying to discourage you.

Also, you don't have to take my advice. Build it and try it out on your own. That's the best way to learn.

I don't know when we'll have our next steam meet. But when we do, please come and we'll share ideas and I definitely would like to see your progress.

Kind regards,
Rick

Honestly, I think the engine's steam exhaust should be more than sufficient ... assuming the turbo is properly sized. Jim Crank told me that Barber Nichols suggested using the turbo compressor end as the exhaust steam turbine because they felt it would be more efficient given the density of steam.

A stream engine is less efficient than an ICE, so it needs more combustion air. On the other hand, this lower efficiency requires more working fluid mass cycling through the engine.... all-in-all, I'd think it would be more or less a wash.

The nice thing about using the exhaust steam is that you are using what would other be waste energy, therefore improving overall system efficiency. It also gives you the option to fit a condenser, which you couldn't do if also routing exhaust gasses into the turbo.

Heck, a number of pressure fired boilers managed to function on just the exhaust gas pressure from the boiler, but in some cases they occasionally needed an electric boost.

Regards,

Ken

Quote

A stream engine is less efficient than an ICE, so it needs more combustion air.

How so?
I found a stream engine that does not require air, but was unable to find an ICE engine with no air requirement.

OK, ya got me, Scott!

Thank you for you ideas, Rick and Ken! I'll do some more research. I definitely like your idea of spooling the turbo with the spent burner exhaust and assisting with the steam exhaust.

I tend to jump in way over my head and learn along the way. I've had many design failures and learned so much already, but that really pales in comparison to what I have yet to learn in this project -- I appreciate your wisdom in that regard. I do wish I started much smaller, but that opportunity has passed, unfortunately. I will upload some images soon so you have a better idea of what I'm working with.

I've attached two pictures of my project thus far. The engine itself is a two cylinder 2" bore, 6" stroke double acting. I managed to destroy my water pump, so I'm trying my hand at building a new one and can't run it on steam until then (and until the crossheads are built...). I'll be the first to admit that everything is pretty rough, but I hate to fully finish something only to find it wont work as I intended, so I try to move around through the project instead of focusing on one thing.

Here are few technical papers on this topic:

1) Design and Testing of a 10KW Steam Turbine for Steam Turbochargers
[asmedigitalcollection.asme.org]

2)Cycle efficiency of air cooled steam power plants
[ntrs.nasa.gov]
3)Critique of Rankine automotive powerplants report
[ntrs.nasa.gov]
4)An assessment of the technology of Rankine engines for automobiles (piston and turbine steam cycle passenger automobiles)
[books.google.com] (downloadable pdf report)

5)Lightweight (1800 lbs with water) steam turbocharged steam boiler for high altitude (40000ft) 5000hp steam turbine aircraft engine
[patentimages.storage.googleapis.com]

6)Fast response automotive steam generator
[patentimages.storage.googleapis.com]

7)Aircraft power plant supercharger driven by exhaust gas heated closed cycle steam turbine
[patentimages.storage.googleapis.com]

8)Auxiliary steam plant for aircraft

[patentimages.storage.googleapis.com]

9)Condensers and boilers for steam-powered cars - A parametric analysis of their size, weight, and required fan power

[ntrs.nasa.gov]



Edited 1 time(s). Last edit at 04/06/2020 06:27PM by novice.

Thanks for the links, Novice! There's some pretty interesting ideas in there!

Turbocharged steam generators were originally proposed for aircraft powerplants. The best designs had weight of 0.35 lbs for 1 hp.
In steam automobiles turbocharged steam generators can help to boost average powerplant net efficiency from 15% to 20-25% by providing power to steam condenser fan, boiler water pump, air conditioner and other auxiliaries from gas turbocharger.

Hi Aristophanese,
I like the pictures of your project. You have some real engine design going on there. A couple of questions: does the one piston valve control both cylinders? The crank is not visible and probably 180 Deg apart? Can we see the crank area and more pictures of the engine?

Have you run the engine on air?

Really love the wheels...some type of wagon wheel?

Nice project and I would like to see it up close some day.

Kind regards,
Rick

Hi Aristophanese,
I recommend checking out the "Tutorial" on the main Steam Automobile website. This was made by Ken, our president. It is an excellent explanation of a good working condensing system. Note that there is a feed water heater where the steam exhaust heat is exchanged with the feed water into the boiler. This has one of the best effects to making your system work.

Best wishes,
Rick

Thanks for the kind words, Rick. Yes, the piston valve controls both cylinders, and the crank is 180 degrees apart. I have run it on air, but it did so with some reluctance. I have yet to install a crosshead and piston rings, so it loses a fair bit of pressure. It turns out McMaster Carr carries some piston rings that will work for my purposes -- I was dreading having to make piston rings.

The wheels I picked up from an old farmer, and they're off a tractor from what I understand. The rear wheels still have what I assume to be a sprocket for powering other equipment.

I'll be sure to read through that tutorial on the main page, thanks!

Hi Aristophanese,
You ran the engine on air with no cross head or piston rings?

I did, very briefly. I was concerned that I was wasting my time building something I didn't even know would run outside of my own head, so I tweaked the timing and ran it very briefly to assuage my concerns.

Are you using these seal rings? If so which ones; the plain PTFE or the bronze filled PTFE?

Lohring Miller

I was, in fact, thinking of the bronze filled rings from McMaster!

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