The Steamboating Forum

Is the air amplifier really better than a simple steam nozzle aimed up the stack? It seems way too good to be true.

I had always discarded the idea of pressurizing the ash pan for fear of a face full of soot. Perhaps some simple interlock. In fact, if I mount the air amplifier on the fire door, the pressure will be dropped automatically when I open the door for firing. Would it work? No, it needs to be on the ash pan door. On the fire door it will blow over the fire.

So my fire door is hinged on one side and the ash pan/air control door is right below it hinged at the upper edge. I suppose a simple linkage that cuts the steam supply to the amplifier when I open the fire door? Perhaps a linkage to a small valve so that when I lift the fire door latch it shuts off the steam supply. The simpler the better.

The fire door is a fairly good fit. Perhaps a gasket as well.

Mike

Mike,

I too would keep it that simple and quiet... Suggestion 1: Carry on board a bag with special fuel (small sticks of dry wood, pine cones or the like) which you would only use in special situations. Suggestion 2: Take a look at this picture - no electronics, no mechanical complications...



Albert

Ram air intake?

Ram air. Right. I think I move a bit slowly for that to help much. I have thought of one of those chimney fittings that turn with the wind. Barbara took one look and, quite rightly, vetoed it!

I do carry some special 'racing wood'. I threw a half a tube of old 5200 caulk in there once. Whoooo! Hot stuff. And no one steamed downwind of me for a bit.

I do have some electronics. A hand held VHF in the tool box along with a flashlight. Oh, yeah. I made a bicycle speedometer in to a tach. If anyone wants the details of that, I can post the calibration number.

Among other things, I make a living using microcomputers in machines. Thus none in my boat.

Mike

You could use a fan in the stack to power a forge blower under the grate

Is the air amplifier really better than a simple steam nozzle aimed up the stack? It seems way too good to be true.

Yes, it is better, because it does a better job in converting the pressure energy in steam to velocity... same reason injectors have cones inside,
rocket engines use DeLavel nozzles, etc.

I had always discarded the idea of pressurizing the ash pan for fear of a face full of soot. Perhaps some simple interlock. In fact, if I mount the air amplifier on the fire door, the pressure will be dropped automatically when I open the door for firing. Would it work? No, it needs to be on the ash pan door. On the fire door it will blow over the fire.

Yup... ash pan, or pull a vacuum on the stack.

So my fire door is hinged on one side and the ash pan/air control door is right below it hinged at the upper edge. I suppose a simple linkage that cuts the steam supply to the amplifier when I open the fire door? Perhaps a linkage to a small valve so that when I lift the fire door latch it shuts off the steam supply. The simpler the better.

You could just arrange the valve so that open ball valve handle locks the ash pan door

- Bart

My father has a turbocharger on his launch, which is exhaust driven and unaffected by the direction the engine is turning nor is there any water loss, unlike a shaft driven fan or a stack blower. It is noisy due to the open compressor side intake.. One could make an air box to alleviate most of the noise, and some day that might just happen.

He originally had the compressor discharge piped into the ash pit pointed upwards. This effectively pressurized the firebox, allowing more fuel (oil)to be burnt. The downside was mainly smoke issuing from the poorly sealed firebox door and smoke hood, gassing the engineer and helmsman. The issue of opening the firebox door and having a blast furnace in your face was fixed by a simple flap that one could quickly put over the compressor intake of the turbo... no air in, no air out.

Due to the noxious fumes my father changed it up, inducing draft by the turbo blowing through a venturi aimed up the stack. This works OK, as there are no longer any nasty fumes and we can still burn more fuel. Unfortunately more draft isn't really necessary with a vertical fire tube and an 8' stack, so a lot of that extra heat energy goes into burning the paint off the stack.

It's hard for him to get his head around doing a better job at sealing where the smoke leaks out and doing it the right way, rather than doing it the easy way and allowing all extra heat energy to go right up the stack.

The Navy developed what is known as the "Pressure Fired Boiler". They were 1200psi, developing around 35,000hp, and were half the size and weight of a conventional boiler of similar capacity. This was accomplished in several ways. As the name implies the combustion chamber operated at 50psig. The higher pressure greatly increased the heat transfer rate allowing for fewer tubes and less water. The vertical down fired combustion chamber was fully lined with tubes which reduced the refractory needs to about 2000lb. The higher combustion pressures also made it practical to use the exhuast to run a turbocharger to provde the combustion air which eliminated the steam load of the forced draft blowers, being as much as 10% of full load. The generating tubes stood vertical, with natural circulation from the steam drum though downcomers to the two circular headers at the bottom. There were 17 escorts built with these boilers.

The Knox Class ships like I was on were originally slated to be pressure fired, but technical problems, later resolved, pushed desginers to opt for the proven D-type boilers. With the advent of high horse power controlable picth propellers, the gas turbine became the prime mover of choice, and further development of light steam plants for the Navy ended.

How's that for increasing out put with alot of hot air!

Dave

Note that a truck turbo might be just the thing for a small boat version of such a boiler - 30 psi of boost, pumped circulation for extra fun.... the heat transfer per sq ft is likely to be pretty amazing... just the thing for a world record attempt.

of course, a Navy engine room at full tilt isn't exactly quiet ....

Back to the exhaust driven blower....

Wesley, on a larger boat I'd be inclined to pull the intake air from around the stack so that we could pre-heat the air going into the boiler; might as well save a few waste BTU... what about lube oil? Car turbos rely on a pressure fed lube - what does your dad do on his boat?

- Bart

Bart,

Pulling the intake air from around the stack might reduce the stack temperature, thus deteriorating the natural draft. It could be improved by adding some length to the stack, at the expense of degraded optics... Anyway, the stack should consist of two concentric tubes with a good insulation between them. This measure rendered a better draft on my boat.

Albert