Re: Uniflow Engines
Posted: Wed Jun 17, 2015 5:13 pm
Hey Fred
I am still not sure which direction I will go with boiler configuration, it depends on the tests I plan to do. This next weekend should see the start of actual projects “in” the shop and not the building “of” the shop.
What I had planned to do was build the engine, boiler, plumbing, pumps, reverse, forward gear box all mounted to a frame that can be lowered in place and bolted to the hull. As soon as I get the plans from Paul at Selway Fisher I will have a better idea just how big the frame will be.
By the time I finish the steam plant for the boat I will have finished a few other projects I have taking up floor space. At that point the shop will have plenty of floor space to build the hull and having the steam plant tested and ready to go will be a good motivator.
As far as the pump goes I was thinking a large diameter cylinder pump that has a large intake valve. The piston in the pump has two sizes to match the two sizes of the cylinder bore. When the pump cycles up water comes in through the large valve. When it cycles down the water goes through the piston to the other side which has a smaller chamber. Since the displacement of the chambers are different the pump moves water out the exit port during both the up and down stroke. With sufficient size I believe I can cycle the pump slowly to eliminate cavitation and still move the amount of water needed.
As far as the driver of the pump goes it will be pretty much setup as any steam driven feed pump. The only difference is that instead of being outside the boiler circuit envelope it will be inside. That way there are no external shaft seals to leak. I will be working on a prototype here sometime this summer to see if it is a possibility. If it works there will be two pumps mounted one on each side of the receiver tank. One works while the other is at standby. If one quits for some reason just shut the valves on one side and open the others. Bleed the steam into the condenser from the one non working pump and then open the flange and pull the whole pump out of the housing. Drop it overboard to cool and repair. We will see how it works out.
Yes I thought about the magnetic drive but eddy currents induced in the separation plate even if non magnetic posses a loss. The magnets would be very close to there upper max working temp. The hotter they get the less pump drive I would have. Once they reach that temp they become permanently non magnets. I am not exactly sure how well the setup would work as I do not know enough about it to speculate. The thoughts I did have would put the magnetic drive section in a small chamber connected by a shaft in a tube away from the impeller far enough so that the magnets would remain well below there max working temp. I do like the idea as this puts far fewer moving parts into the whole needing a water pump idea. That is why I asked about high temperature bearings. Even if the magnetic coupling was away from the heat the impeller would be right in the middle of it. And both bearings would be inside the boiler circuit with nothing but water for lube.
Cool filtered water could be fed into the magnetic drive section which would then move down the tube around the impeller shaft and out through the impeller bearings behind the impeller if heat was the only issue. But there again I don't know enough about bearings in that environment to speculate with much conviction.
A positive displacement plunger pump will displace X amount of water period. If the pump is moving then so is the water. The only bearings it has are the seals around the pistons which are already made to handle the heat. So you have a drive piston/plunger arrangement mounted on a common shaft so one moving part with two valves so add two more plus the valve arrangement. Not much to go wrong and pretty easy to fix.
The Mono tube has a pump as well that has to run or you get tube failure. Granted that pump has only the pressure of the system to deal with and not the heat as well but from what I have read the control systems are a lot harder to balance. You will also have a separator in the system which may as well be a holding tank like the LaMont. It's a good place to mount the site glass to keep the water level up in the system. Both need to keep the tubes full, both use pumps, both are smaller and lighter than there VTF counter parts, but the LaMont has a bit more leeway built in with the extra water in the system.
But there again I do not know enough about either a mono tube system or LaMont to settle on one or the other which will change while I experiment with pumps and these steam generators I have here.
Here are a couple pictures of the bigger heater unit. [img][IMG]http://i12.photobucket.com/albums/a222/ ... oe9zcc.jpg[/img][/img]
This is the coil out of the Landa burner. It has the same specs as the other smaller one save it will heat up to 10 GPM. With the adition of a super heater coil and an outter economizer this one would make a good monotube boiler I think. It will serve for the tests I will do to get a better idea of what exactly I do need.
On a side note can anyone tell me why I should not use an already made crankshaft like from a car or truck? I was thinking of starting with a 100mm stroked VW crank.
Cyruscosmo
I am still not sure which direction I will go with boiler configuration, it depends on the tests I plan to do. This next weekend should see the start of actual projects “in” the shop and not the building “of” the shop.
What I had planned to do was build the engine, boiler, plumbing, pumps, reverse, forward gear box all mounted to a frame that can be lowered in place and bolted to the hull. As soon as I get the plans from Paul at Selway Fisher I will have a better idea just how big the frame will be.
By the time I finish the steam plant for the boat I will have finished a few other projects I have taking up floor space. At that point the shop will have plenty of floor space to build the hull and having the steam plant tested and ready to go will be a good motivator.
As far as the pump goes I was thinking a large diameter cylinder pump that has a large intake valve. The piston in the pump has two sizes to match the two sizes of the cylinder bore. When the pump cycles up water comes in through the large valve. When it cycles down the water goes through the piston to the other side which has a smaller chamber. Since the displacement of the chambers are different the pump moves water out the exit port during both the up and down stroke. With sufficient size I believe I can cycle the pump slowly to eliminate cavitation and still move the amount of water needed.
As far as the driver of the pump goes it will be pretty much setup as any steam driven feed pump. The only difference is that instead of being outside the boiler circuit envelope it will be inside. That way there are no external shaft seals to leak. I will be working on a prototype here sometime this summer to see if it is a possibility. If it works there will be two pumps mounted one on each side of the receiver tank. One works while the other is at standby. If one quits for some reason just shut the valves on one side and open the others. Bleed the steam into the condenser from the one non working pump and then open the flange and pull the whole pump out of the housing. Drop it overboard to cool and repair. We will see how it works out.
Yes I thought about the magnetic drive but eddy currents induced in the separation plate even if non magnetic posses a loss. The magnets would be very close to there upper max working temp. The hotter they get the less pump drive I would have. Once they reach that temp they become permanently non magnets. I am not exactly sure how well the setup would work as I do not know enough about it to speculate. The thoughts I did have would put the magnetic drive section in a small chamber connected by a shaft in a tube away from the impeller far enough so that the magnets would remain well below there max working temp. I do like the idea as this puts far fewer moving parts into the whole needing a water pump idea. That is why I asked about high temperature bearings. Even if the magnetic coupling was away from the heat the impeller would be right in the middle of it. And both bearings would be inside the boiler circuit with nothing but water for lube.
Cool filtered water could be fed into the magnetic drive section which would then move down the tube around the impeller shaft and out through the impeller bearings behind the impeller if heat was the only issue. But there again I don't know enough about bearings in that environment to speculate with much conviction.
A positive displacement plunger pump will displace X amount of water period. If the pump is moving then so is the water. The only bearings it has are the seals around the pistons which are already made to handle the heat. So you have a drive piston/plunger arrangement mounted on a common shaft so one moving part with two valves so add two more plus the valve arrangement. Not much to go wrong and pretty easy to fix.
The Mono tube has a pump as well that has to run or you get tube failure. Granted that pump has only the pressure of the system to deal with and not the heat as well but from what I have read the control systems are a lot harder to balance. You will also have a separator in the system which may as well be a holding tank like the LaMont. It's a good place to mount the site glass to keep the water level up in the system. Both need to keep the tubes full, both use pumps, both are smaller and lighter than there VTF counter parts, but the LaMont has a bit more leeway built in with the extra water in the system.
But there again I do not know enough about either a mono tube system or LaMont to settle on one or the other which will change while I experiment with pumps and these steam generators I have here.
Here are a couple pictures of the bigger heater unit. [img][IMG]http://i12.photobucket.com/albums/a222/ ... oe9zcc.jpg[/img][/img]
This is the coil out of the Landa burner. It has the same specs as the other smaller one save it will heat up to 10 GPM. With the adition of a super heater coil and an outter economizer this one would make a good monotube boiler I think. It will serve for the tests I will do to get a better idea of what exactly I do need.
On a side note can anyone tell me why I should not use an already made crankshaft like from a car or truck? I was thinking of starting with a 100mm stroked VW crank.
Cyruscosmo