1 Steam Cars : Phorum
General Steam Car topics
Air Ejectors
Posted by: Peter Heid (IP Logged)
Date: September 17, 2002 07:44PM
<HTML>I can see the benifit of exhaust vacuum in a modern steam system especially if all the steam can be condensed. Not only are you raising the MEP but you are also increasing the efficiency of the condenser. A few difficulties arise including the increased volume of steam which inflates the overall system size. This can pose great difficulties when designing for a limited space such as vehicular transport. The vacuum conditions would limit the disolved gasses in the feed water that returns from the condenser, possably reducing system corrosion. When you look at the other side of the equation, you must consider the power consumed to generate and maintain a vacuum condition, its initial cost and cost of maintainance. Even with the most efficient equiptment used to generate a vacuum, a point of zero return will result if the vacuum costs more power than it saves. As you head toward this point, the returns begin to diminsh and an inefficient engine / system will bring you to this point sooner or in poor conditions you may start on the wrong side and realize no benefit only continued loss. On to my point, in the many power plant books I have collected, the steam ejector gets great reviews especially the 2 and 3 stage ejectors. They use no moving parts and most of the heat from the steam that drives it is returned to the boiler feed as it is used to condense the steam in the ejector. They take up little space and can provide a reasonable vacuum especially if in 3 or more stages.
Has anyone had their hands on one of these gems ? Are they suitable fore moble opperation if correctly sized ? How much energy do they actually use for the rated level of vacuum ?
Peter Heid</HTML>
Has anyone had their hands on one of these gems ? Are they suitable fore moble opperation if correctly sized ? How much energy do they actually use for the rated level of vacuum ?
Peter Heid</HTML>
Re: Air Ejectors
Posted by: tom ward (IP Logged)
Date: September 17, 2002 09:48PM
<HTML>Doesn't lowering the pressure inside the condensor also reduce the temperature fusion [condensation] which increases the latent heat and the exchange area needed for cooling? If the lowest absolute pressure of the entire steam circuit was kept above 60 psi condensation would occur at over 300F. This would cut the needed exchange area in half thereby cutting total weight. Of course to maintain thermal efficiency the temp of the superheated steam would also need to rise.</HTML>
Re: Air Ejectors
Posted by: David K Nergaard (IP Logged)
Date: September 17, 2002 10:34PM
<HTML>The usual steam jet air ejectors are built to handle the air infiltrating the condensors of major power plants. They use nearly 100 pounds of steam per hour, but by lowering the condensor pressure by one inch of mercury, they may save several thousand pounds of steam per hour in a multimegaWatt plant.
In automotive sizes, I suspect they would be very inefficient, bulky and useless. Primarily useless because auto's don't have a good cooling medium to get a good vacuum in the first place!</HTML>
In automotive sizes, I suspect they would be very inefficient, bulky and useless. Primarily useless because auto's don't have a good cooling medium to get a good vacuum in the first place!</HTML>
Re: Air Ejectors
Posted by: Terry Williams (IP Logged)
Date: September 17, 2002 11:49PM
<HTML>I can answer that I have spent many hours with these. They are one of only a few items off a full sized marine steam plant that would even fit in a steam auto. As someone mentioned, they use more steam than you'd probably want to spare. They could most llikely be sized down, but probably at some loss of efficiency. One of the problems with running a vacuum is pumping the condensate, it tends to flash back to steam unless you cool it (condensate depression). And of course the maximum vacuum is determined by the temperature of the condenser, not the vacuum/air pump, given you remove al lthe non condensable gasses. These generally exhaust into a separate condenser as the steam is contaminated.</HTML>
Re: Air Ejectors
Posted by: Mike Bennett (IP Logged)
Date: September 18, 2002 06:21PM
<HTML>Peter,
Have you tried the Penberthy Company?
Regards,
Mike</HTML>
Have you tried the Penberthy Company?
Regards,
Mike</HTML>
Re: Air Ejectors
Posted by: Dick Vennerbeck (IP Logged)
Date: September 18, 2002 09:18PM
<HTML>Pennberthy and Buffalo Companies both make steam ejectors and eductors. These are are usually used for moving/pumping liquids from one point to a second point that is at less than the steam operating pressure. These are not suitable for your application. The amount of steam consumed would be considerable for the partial reduction in pressure achieved. The maximum gain in effective working pressure by exhausting into a vacuum is probably 7 psi or less. The vapor pressure of the water will decrease at the condensate temperature increases. Remember that the best vacuum you can get is 760mm of Hg. or about 14 psi. In my early vacuum engineering days there were still a few steam "roughing pumps" being used to rough out large industrial vacuum chambers prior to using a diffusion pump for hi vac. They were usually fed by the industries boiler heating system or a stand alone boiler. Most of the steam boating folks use a semi closed system with an engine driven pump to provide vacuum and condensate return. Fortunately we are floating in one of the best mediums to cool our condensers. Big power plants usually have this same luxury.</HTML>
Re: Air Ejectors
Posted by: Rolly Evans (IP Logged)
Date: September 19, 2002 12:07PM
<HTML>If you use a baffle plate or cyclone oil separator in the exhaust steam line, this will also separate air to some extent. Liquids (oil) can be drained to a sump or ejected from the system with traps. The air can also be vented but the control for this may be a problem. I’m not sure of the benefit verses cost.</HTML>
Re: Air Ejectors
Posted by: Jim Crank (IP Logged)
Date: September 19, 2002 01:13PM
<HTML>Peter,
Yes, tried a Penberthy ejector in my old Stanley once.
It took too much steam, didn't produce any usable vacuum and soon got the water tank boiling. Good for bilge pumping though.
Much better is a no internal compression vacuum pump, like a small Roots. They give a whopping good vacuum, the moisture helps seal them up, and they take little power for the high vacuum they can deliver.
Jim</HTML>
Yes, tried a Penberthy ejector in my old Stanley once.
It took too much steam, didn't produce any usable vacuum and soon got the water tank boiling. Good for bilge pumping though.
Much better is a no internal compression vacuum pump, like a small Roots. They give a whopping good vacuum, the moisture helps seal them up, and they take little power for the high vacuum they can deliver.
Jim</HTML>
Re: Air Ejectors
Posted by: Dick Vennerbeck (IP Logged)
Date: September 19, 2002 06:35PM
<HTML>Jim is absolutely right. I used a small gear pump driven off the crank in my first steam powered launch. I set it up with check valves that would allow it to work with the engine running in either direction. The condensate provided a very good seal and with cold water gave me over 23" of vacuum. Cliff Blackstaff rode in my boat and asked me if I thought the the operation of the vacuum pump could be done by the 8 psi differential that I saved. Good point....I wonder, it did make it easier to get the water back into the hotwell to remove the oil.</HTML>
Re: Steam Ejectors
Posted by: Rolly Evans (IP Logged)
Date: September 20, 2002 08:55AM
<HTML>Steam ejectors, they won’t work on air.
Dick I also use them on both my boats for bilge pumps, as well as most other Stanley owner to fill the water tank from a pond or river. They do heat the water that is pumped. A lot of them are used in the food processing industry for that very reason. I thought of using a large two inch one for a bow thruster on my big boat, but never did. By the time I get to the dock I have full 275 PSI pressure and 35 gal of water in the boiler. I hate to put holes in the hull below the water line, and was not sure if there would be enough thrust.</HTML>
Dick I also use them on both my boats for bilge pumps, as well as most other Stanley owner to fill the water tank from a pond or river. They do heat the water that is pumped. A lot of them are used in the food processing industry for that very reason. I thought of using a large two inch one for a bow thruster on my big boat, but never did. By the time I get to the dock I have full 275 PSI pressure and 35 gal of water in the boiler. I hate to put holes in the hull below the water line, and was not sure if there would be enough thrust.</HTML>
Re: Air Ejectors
Posted by: Jim Crank (IP Logged)
Date: September 20, 2002 01:21PM
<HTML>Dick,
It certainly does improve the power of a steam engine for it to exhaust into a vacuum. ESPECIALLY a compound.
During my education with Bill Besler, he had Barney Becker and I measure the water rate and horsepower of the second airplane engine, a V-2 compound.
We also had the electronic PV indicator hooked up on both cylinders so we could see the PV diagram as the engine was running. The vacuum pump in the lab was run by a variable speed electric motor, so we could get whatever vacuum we wanted, up to 26" Hg. The engine dumped into a big water cooled condenser and the vacuum pump was, of course, on the discharge of the condenser.
I don't recall the exact numbers; but with backpressure it was one thing, and we could actually see the higher compression pressure in the cylinders.
With 26" the bottom line of the PV diagram shot almost off the scope and the dyno was reading a significant more horsepower. If I recall correctly the water rate went from around 15-17 down to 11 with a high vacuum. Same cutoff used for all measurements.
If the pump is made of the right material, water alone will certainly help seal it up. Vacuum pumps take little power as long as the right one is being used.
Jim</HTML>
It certainly does improve the power of a steam engine for it to exhaust into a vacuum. ESPECIALLY a compound.
During my education with Bill Besler, he had Barney Becker and I measure the water rate and horsepower of the second airplane engine, a V-2 compound.
We also had the electronic PV indicator hooked up on both cylinders so we could see the PV diagram as the engine was running. The vacuum pump in the lab was run by a variable speed electric motor, so we could get whatever vacuum we wanted, up to 26" Hg. The engine dumped into a big water cooled condenser and the vacuum pump was, of course, on the discharge of the condenser.
I don't recall the exact numbers; but with backpressure it was one thing, and we could actually see the higher compression pressure in the cylinders.
With 26" the bottom line of the PV diagram shot almost off the scope and the dyno was reading a significant more horsepower. If I recall correctly the water rate went from around 15-17 down to 11 with a high vacuum. Same cutoff used for all measurements.
If the pump is made of the right material, water alone will certainly help seal it up. Vacuum pumps take little power as long as the right one is being used.
Jim</HTML>
Re: Air Ejectors
Posted by: Peter Heid (IP Logged)
Date: September 21, 2002 03:39PM
<HTML>Thanx Everyone for the information. It's great to have the forum when you don't have a chance to experiment with everything, someone probably has tried it and all you have to do is ask.
Peter Heid</HTML>
Peter Heid</HTML>
Re: Air Ejectors
Posted by: Jim Crank (IP Logged)
Date: September 23, 2002 12:50PM
<HTML>Peter et al,
Just for the fun of it. Years ago, SACA member and Stanley owner Carl Guth showed me an old diagram for a steam system that was as far out in left field as one could get. Exhaust steam from an engine was induced with a steam powered ejector into only a superheater coil, then back into the engine.
The idea was once you got the contraption going, you then never had to deal with the heat of vaporization loss. Chew on that one, guys!!
Jim
P.S. Your e-mail address got kicked back. Thanks so much for the separator paper, really good stuff.</HTML>
Just for the fun of it. Years ago, SACA member and Stanley owner Carl Guth showed me an old diagram for a steam system that was as far out in left field as one could get. Exhaust steam from an engine was induced with a steam powered ejector into only a superheater coil, then back into the engine.
The idea was once you got the contraption going, you then never had to deal with the heat of vaporization loss. Chew on that one, guys!!
Jim
P.S. Your e-mail address got kicked back. Thanks so much for the separator paper, really good stuff.</HTML>
Re: Air Ejectors
Posted by: William L. Petitjean, P.E. (IP Logged)
Date: September 27, 2002 01:34AM
<HTML>Hi Peter:
I am back. Typically steam ejectors are used to pump non-condensible gases from the condenser when under vacuum. The primary vacuum producer is the collapse in steam volume when the vapor is condensed to a liquid. However, dissolved gases in the feed water get purged in the boilers and are carried with the steam through the prime mover. When these gases and air leakage into the vacuum side of the system build up in the condenser they can gradually cause a loss of vacuum. So they must be pumped out continually.
There is no efficiency gain by artificially producing a vacuum in excess of the natural vacuum. The use of a steam ejector to produce a primary vacuum would take enormous amounts of steam and this is not practical. If you look through your power plant books you will find a section on multi-jet condensers. This is the only practical vacuum condenser for a small automobile steam plant.
I also posted a description of this type of condenser arrangement some time ago, but don't remember the date.
Bill Petitjean</HTML>
I am back. Typically steam ejectors are used to pump non-condensible gases from the condenser when under vacuum. The primary vacuum producer is the collapse in steam volume when the vapor is condensed to a liquid. However, dissolved gases in the feed water get purged in the boilers and are carried with the steam through the prime mover. When these gases and air leakage into the vacuum side of the system build up in the condenser they can gradually cause a loss of vacuum. So they must be pumped out continually.
There is no efficiency gain by artificially producing a vacuum in excess of the natural vacuum. The use of a steam ejector to produce a primary vacuum would take enormous amounts of steam and this is not practical. If you look through your power plant books you will find a section on multi-jet condensers. This is the only practical vacuum condenser for a small automobile steam plant.
I also posted a description of this type of condenser arrangement some time ago, but don't remember the date.
Bill Petitjean</HTML>
Re: Air Ejectors & Jet Condensers
Posted by: Jim Crank (IP Logged)
Date: September 27, 2002 01:05PM
<HTML>Peter, William,
Decades ago there was a raging argument goin on the best way to condense the steam in an automotive powerplant.
1) Just use an air cooled condenser with a fan and vacuum pump and deal with the heat of vaporization phase change load in that condenser. This needs a large surface area.
2) Use a jet condenser and then flow the water through the now radiator and have the big heat of vaporization phase change load done in the jet condenser and not in the radiator.
OK. the two questions that never got answered were:
1) Does the jet condenser idea give one a much reduced radiator size, thanks to the better heat transfer between water and air vs a steam to air cooled condenser, to make it worth while?
2) Is there a gain overall in the two pump loads vs the big condenser fan and vacuum pump load of an air cooled condenser?
These never got resolved.
Jim</HTML>
Decades ago there was a raging argument goin on the best way to condense the steam in an automotive powerplant.
1) Just use an air cooled condenser with a fan and vacuum pump and deal with the heat of vaporization phase change load in that condenser. This needs a large surface area.
2) Use a jet condenser and then flow the water through the now radiator and have the big heat of vaporization phase change load done in the jet condenser and not in the radiator.
OK. the two questions that never got answered were:
1) Does the jet condenser idea give one a much reduced radiator size, thanks to the better heat transfer between water and air vs a steam to air cooled condenser, to make it worth while?
2) Is there a gain overall in the two pump loads vs the big condenser fan and vacuum pump load of an air cooled condenser?
These never got resolved.
Jim</HTML>
Re: Air Ejectors & Jet Condensers
Posted by: Peter Heid (IP Logged)
Date: September 27, 2002 06:42PM
<HTML>Jim,
I think the first question can be answered for conditions specific to a steam auto becuase all the variables are known for a suitable answer. We know transfer rates and have information on the actual operation of the two types of condensing systems. The second question is tougher and without anything operational in this size range, experimentation might the only way to determine actual gains or losses. I believe a properly designed steam/air condensor is the way to go just for simplicity sake and they can be placed at multipule locations. Either can also be used to provide propulsion as in a jet engine, after all we are heating air, lets use that expansive force also. One trouble I often notice is the use of what is just a radiator designed for a IC auto. The IC auto radiator is designed to increase the air temperature by only 15 or 20 degrees as it passes through. I may be wrong but my books lead me to believe that it should be around twice that for a steam heat exchanger design. I could never figure out why an IC auto would blow hot air from the radiator back into the engine compartment it was trying to cool.
Peter Heid</HTML>
I think the first question can be answered for conditions specific to a steam auto becuase all the variables are known for a suitable answer. We know transfer rates and have information on the actual operation of the two types of condensing systems. The second question is tougher and without anything operational in this size range, experimentation might the only way to determine actual gains or losses. I believe a properly designed steam/air condensor is the way to go just for simplicity sake and they can be placed at multipule locations. Either can also be used to provide propulsion as in a jet engine, after all we are heating air, lets use that expansive force also. One trouble I often notice is the use of what is just a radiator designed for a IC auto. The IC auto radiator is designed to increase the air temperature by only 15 or 20 degrees as it passes through. I may be wrong but my books lead me to believe that it should be around twice that for a steam heat exchanger design. I could never figure out why an IC auto would blow hot air from the radiator back into the engine compartment it was trying to cool.
Peter Heid</HTML>
Re: Air Ejectors & Jet Condensers
Posted by: tom ward (IP Logged)
Date: September 27, 2002 07:50PM
<HTML>According to the New Cathecism of Steam (circa 1900) a jet condensor must inject at least 5 lbs of water to condense 1 lb of steam. I've considered an air/injection hybrid condensor. Put large rectangular headers on the top and bottom of a row of radiator cores and inject cooled water into the top header and steam into the bottom header. Add a high volume, low pressure pump driven by exhaust steam to circulate the water from the reserve tank to the injectors.</HTML>
Re: Air Ejectors & Jet Condensers
Posted by: David K Nergaard (IP Logged)
Date: September 28, 2002 10:55PM
<HTML>To keep the condensor/radiator as small as possible one needs to keep the temperature difference as large as possible. If one uses water to condense the steam, one then has to cool a large amount of liquid that must in turn, already be cooler than the steam. Thus, using a jet condensor on a car will require a larger radiator. Plus pumps etc.!
Condening the steam directly in an air cooled condernsor/radiator is the logical way to go. 73 DK</HTML>
Condening the steam directly in an air cooled condernsor/radiator is the logical way to go. 73 DK</HTML>
Re: Air Ejectors & Jet Condensers
Posted by: tom ward (IP Logged)
Date: September 29, 2002 09:01AM
<HTML>Dave, that takes us back to my orignal point of keeping the entire water/steam circuit above 60 psia.</HTML>
Re: Air Ejectors & Jet Condensers
Posted by: Jean Vezina (IP Logged)
Date: September 30, 2002 12:10AM
<HTML>
According to Karl Petersen, a spray condenser should allow to reduce
the radiator size:
See:
[www.firedragon.com]
But there aren't any quantitative measurements shown here.
Regards,
Jean Vezina</HTML>
According to Karl Petersen, a spray condenser should allow to reduce
the radiator size:
See:
[www.firedragon.com]
But there aren't any quantitative measurements shown here.
Regards,
Jean Vezina</HTML>
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