Hey Bart

[barts]

The trick with oil burners is that for proper combustion you really want all the air admitted with the oil spray. It is difficult to use natural draft to do this; domestic oil burners mist the oil w/ 150 psi or so of pressure, and blow in combustion air, and steam atomizing burners typically achieve the same effect by using additional steam past that which is necessary to spray the oil. Little too much smoke - turn up the steam, and the mixture is adjusted.

I'm not sure how I'd rig an oil fire to handle automatically changing draft; I was very pleased when I added a homebuilt steam pressure regulator to Otter, since it made fire control basically trivial. I'm not quite ready to have the fire automatically increase whenever I open the throttle.

- Bart

[Lopez Mike]

Sheesh! By the time I add turbulators to the flues, an exhaust feedwater heater, an economizer, A stack blower and a supercharger forced draft system, I'll have so much power that I'll be on a plane and be so efficient that I'll have firewood popping out of the firebox door!

I'll think about a direct drive blower. My working range for needing more steam is 400-500 r.p.m. so the next thing will be to see how fast a shop vac turns. Obviously I don't need that sort of hoohaw going on in my firebox but, if my memory serves me at all, the output of a centrifugal blower goes up as something like the square or better of the r.p.m.

Scott, I wouldn't mind a picture of the gearing on one of those units you are talking about. Any idea what the ratio might be?

Mike

[Cyruscosmo]

Hey Mike

I have not counted the teeth yet I will do so and get ya a picture. The shop vacs we use turn about 8000 rpm if I remember correctly and that compressor tuns about the same. What I had planned to try was to replace the motor on the compressor frame with the shop vac compressor and extend the shaft on the big gear and drive that.

I am guessing at this point but the small gear is about 3/4 inch across and the big one is about 3.25. I will be heading back into the shop in the morning and will count teeth and get a picture then.

The experiment I am setting up for is to use a pot type vaporizer to burn the oil in and push air through that instead of pressurizing the oil. Sorta like a turbo charged version of the waste oil burners ya see all over you tube. Since the majority of the tubes in the boiler are over the flame and radiant heat going down is pretty much wasted I did not see the point in trying to make a classic teardrop shaped flame in the middle of the firebox. I am going to set the burner up so that it can be inserted in the boiler and removed easily so that I can use wood as the primary fuel.

The scenario would be something like this... I leave port with not quite as much wood as I thought I needed. Or I gets in a pickle and use more wood with oncoming wind or currents that I had not expected. I can slip the oil burner in place, plug in a fuel quick connect, flip the blower from air amplifier to oil pot blower and use the 10 gallons of waste oil stashed in a well fitted tank under a floorboard somewhere. I can squeeze ten gallons in places wood would not fit too well. The oil would be my backup or if I were going on a really L O N G trip (say up the inside passage) I could add some tanks and make the wood my backup.

I figured it would be best to build the engine and boiler first, get them on a frame and tested and then build the hull, so I am brainstorming what makes it hot. Anyway it gives me something to do that will benefit the Launch I wanna build while I am still not in a position to actually start that build.

Cheers,
Scott

[fredrosse]

"Centrifugal blowers have a delivery v.s. r.p.m. curve that is wildly non-linear. "

My job for the last several years has largely been draft systems design for steam power plants, and it is a fact that all centrifugal or axial fans/blowers have a flow rate that is very nearly a linear function of RPM, double the RPM, double the flow, etc.

[Lopez Mike]

Ah! I stand corrected. I was fooled by the horsepower curves of gasoline I.C. engines which show a giant increase in power as r.p.m. reaches the higher ranges. Direct driven superchargers, I mean. Obviously there is a more complicated interaction going on in those applications.

This gives me much more hope that I can get a reasonable amount of air flow at lower blower R.P.M.'s

Thanks Fred,

Mike

[barts]

Interesting centrifugal fan rules:

CFM (volume of delivered air) varies with directly (linearly) with RPM.
Pressure varies with the square of the RPM (e.g. doubling RPM delivers 4x pressure)
Power required varies with the cube of the RPM (e.g. doubling RPM takes 8x the power).

- Bart

[Lopez Mike]

Ah, that sheds some light on the non-linear power curves of those old racing engines. I.C. engines are very sensitive to inlet conditions. It was a given that crank driven centrifugally blown engines were good for Bonneville or big oval tracks but not so good for road circuits where there was a lot of going up through the gears. Also, they were known for flying to bits if over revved much. The cylinder pressure went through the roof.

They worked great on aircraft where the load v.s. r.p.m. relationship was more constant. The Merlin has a two stage centrifugal and the P-38 Allison used an exhaust driven centrifugal for a first stage and a crank driven centrifugal for a second stage.

This is a steam forum. Enough stink pot stuff!

I wish I could come up with an esthetically pleasing way to plumb in my air amplifier into my stack. All very bulky and clunky looking. A two inch duct is hard to hide. I wonder if the amplifier would survive in the stack? Maybe up nearer to the top where things have maybe cooled down a bit? And would it seriously impede my natural draft when not in use?

Mike


Mike

[DCSmith]

Have you considered machining one the diameter of the funnel, and using it at the base? You could have the benign qualities of induced draught, it shouldn't offer much resistance when not in use, and could be made to look good.

[Cyruscosmo]

Hey Mike

I set those pics up so you can see um here http://www.whisperedmyth.com/ I don't have a photo bucket site but I do have a place to park pictures.

As I said before I am just doodling around with this idea until I figure out if it is going to work or not. I still have to sort out the patent drawings and info for the oil burner. If it does what I hope the whole affair will be duplicated in something more like bronze.

As you can see there would be a good place to include a vacuum pump in that arrangement for the condenser system as well. Anyway I have a few of these things laying around the shop. My job there is fix anything they break and build any tools they need so I keep spare parts for everything.

Cheers,
Scott

[Lopez Mike]

Thanks for the pictures and the measurements, Scott. I build stuff with toothed belts all the time. I'll have to give this some thought.

Building an air amplifier that has an eight inch bore would be in interesting proposition. I think I might get in way over my head. The one I have in hand is two inches in diameter and the annular gap for the air or steam to enter the main passage is one a few thou. With one four times as large, the gap would have to be one forth as wide. Like about a thousandth of an inch? Of course maybe I don't know enough about air amplifier design to stick in a pig's eye. More than probable.

Getting too late at night to think about anything but popcorn and hot chocolate.

Mike