1 Steam Cars : Phorum
General Steam Car topics
Regenerative Braking
Posted by: Peter Heid (IP Logged)
Date: February 11, 2003 12:01AM
<HTML>Lately there has been some disscussion about regenerative braking and I have a portion of an article from the 1930's describing a condensing steam locomotive with a compressor to recompress the exhaust steam. The trials were very sporadic as the experimenters had very little time to continue work or test the equiptment due to the regular train schedules they had to work around. The experiment was performed on a boiler of 180 psi with a consumptive exhaust fan turbine to promote draft. The turbine had to be carefully run as it could easily drop the boiler pressure under high loads, when it was needed the most. With this and a few other difficulties, the experiment was discontinued though not necessarilly a failure, some promising results had been obtained. I am still searching for the complete article and not getting far. Unfortunatly I don't even have the name of the railroad or the locomotive they experimented on.
Has anyone heard of this experiment and by whom it was performed ?
Peter Heid</HTML>
Has anyone heard of this experiment and by whom it was performed ?
Peter Heid</HTML>
Re: Regenerative Braking
Posted by: David K Nergaard (IP Logged)
Date: February 11, 2003 12:31PM
<HTML>There was a series on this subject in Light Steam Power. The idea was to recover the energy in the exhaust steam by recompressing it and feeding it into the boiler. I, for one, don't see how any energy gain can come from this, the mechanical work to do the compression must exceed the heat returned to the boiler. At any rate, it did not become used on any main line loco's.
There is a compression brake that was widely used since about 1900, the Le Chatelier water brake. For a current example, look at the engines used on the Mt. Washington Railway.</HTML>
There is a compression brake that was widely used since about 1900, the Le Chatelier water brake. For a current example, look at the engines used on the Mt. Washington Railway.</HTML>
Re: Regenerative Braking
Posted by: C Benson (IP Logged)
Date: February 11, 2003 01:24PM
<HTML>Hi ,,,,,, IF,,,,IF,,,,,the engine will develop torque enough to slip the wheels at full throttle,,,you'd need to drop boiler pressure to make this work,,,,AT ALL ,,Hmmmmm The cog rail fortunately is not plagued with this traction problem,,,,Cheers Ben</HTML>
Re: Regenerative Braking
Posted by: Peter Heid (IP Logged)
Date: February 11, 2003 06:17PM
<HTML>Cobern,
Some steam autos have varied the boiler pressure with demand. I think the Carter steam car is one using this technique.
Peter Heid</HTML>
Some steam autos have varied the boiler pressure with demand. I think the Carter steam car is one using this technique.
Peter Heid</HTML>
Re: Regenerative Braking
Posted by: Dick Vennerbeck (IP Logged)
Date: February 11, 2003 08:31PM
<HTML>What do you get when you recompress steam? Hmmm seems like the easiest method would be to water cool your brakes with your feedwater! Somehow regenerative steam braking does not sound useful in an automobile. If your workin your butt off to condense the steam back into water and throwing that heat away, what would you do with more heat..preheat the fuel maybe. simplest and probably more unique would be to wind up a big clock spring or spin a flywheel in a vacuum?</HTML>
Re: Regenerative Braking
Posted by: Peter Brow (IP Logged)
Date: February 12, 2003 10:01AM
<HTML>Hi David,
I haven't seen the articles in question, but somebody on this or the SACA forum said that a locomotive equipped with a diesel exhaust recompressor did show lower fuel consumption than the plain steam locomotive. However, as I recall, it was stated that the cost and maintenance of the equipment didn't justify the expense.
Energy is indeed lost in the compression process, so even if all the exhaust steam is recompressed, the diesel/steam hybrid would eat more fuel than a plain diesel operating at full load. Compared to a diesel engine operating at very low load, though, there might be an improvement, if the steam could be accumulated and the compressor cycled on/off with diesel engine operating only at full load. An exhaust steam accumulator would take up a lot of space though. Maybe if the exhaust steam were condensed by absorbing its heat into a storage medium, and then the heat turned back into low-pressure steam to recompress? This has more heat losses, though, and the whole procedure gets pretty Rube Goldberg, with lots of stages, loses, and costly extra equipment.
Regenerative braking is a bit different. Even if it is relatively inefficient (whatever system is used), it wastes less energy than a total-loss friction braking system. Making it both continuously variable and economically feasible is the hard part, and though interested in the various possibilities, I have serious doubts.
Something like the proposed Ford hydraulic regenerative braking system (which I mentioned recently at the SACA forum) seems to me the most efficient/promising of the various options, or maybe a "big clock spring" like Dick suggests, which may not be as impractical as it sounds. The energy storage capacity needed for an automobile "regenobrake" system isn't too big -- enough to decelerate/accelerate the car one time from/to 65 mph, maybe a few hundred feet of travel.
Perhaps designing the steam engine to compress air properly to (help?) brake the car, and storing the air in a tank? Then the compressed air would run the engine briefly on acceleration. Storage tank might not have to be very big. Keeping air out of the steam/water system would be a must. Air from tank could run thru a tube coil preheated (to 300-500°F) by boiler or engine exhaust, to make up for some of the compression/expansion losses.
Haven't done the math, but depending on the air pressure and exhaust temp, that might "recoup" more energy than was put into compressing the air -- ie, brake for 200 feet, then run for 300 feet before switching back to steam. Or, decelerate from 60 mph, then accelerate to 70 mph on air, by recovering some extra waste heat in the process? Doubtful, though -- air compression temp would have to be lower than exhaust temp, and there are exhaust pressure losses.
For now, I'd bet on the hydraulic regenobrake system a la Ford. Still many problems, eg, you're only regen-braking with two wheels, how do you transition smoothly from 2-wheel regen braking to 4-wheel friction braking when the accumulator fills up, etc.. And will the equipment cost be less than that of the fuel saved? A worthwhile system seems way off in the future, if ever.
Intriguing possibilities, though. Ford claims their hydraulic system could increase city fuel mileage by 20-25%.
Peter</HTML>
I haven't seen the articles in question, but somebody on this or the SACA forum said that a locomotive equipped with a diesel exhaust recompressor did show lower fuel consumption than the plain steam locomotive. However, as I recall, it was stated that the cost and maintenance of the equipment didn't justify the expense.
Energy is indeed lost in the compression process, so even if all the exhaust steam is recompressed, the diesel/steam hybrid would eat more fuel than a plain diesel operating at full load. Compared to a diesel engine operating at very low load, though, there might be an improvement, if the steam could be accumulated and the compressor cycled on/off with diesel engine operating only at full load. An exhaust steam accumulator would take up a lot of space though. Maybe if the exhaust steam were condensed by absorbing its heat into a storage medium, and then the heat turned back into low-pressure steam to recompress? This has more heat losses, though, and the whole procedure gets pretty Rube Goldberg, with lots of stages, loses, and costly extra equipment.
Regenerative braking is a bit different. Even if it is relatively inefficient (whatever system is used), it wastes less energy than a total-loss friction braking system. Making it both continuously variable and economically feasible is the hard part, and though interested in the various possibilities, I have serious doubts.
Something like the proposed Ford hydraulic regenerative braking system (which I mentioned recently at the SACA forum) seems to me the most efficient/promising of the various options, or maybe a "big clock spring" like Dick suggests, which may not be as impractical as it sounds. The energy storage capacity needed for an automobile "regenobrake" system isn't too big -- enough to decelerate/accelerate the car one time from/to 65 mph, maybe a few hundred feet of travel.
Perhaps designing the steam engine to compress air properly to (help?) brake the car, and storing the air in a tank? Then the compressed air would run the engine briefly on acceleration. Storage tank might not have to be very big. Keeping air out of the steam/water system would be a must. Air from tank could run thru a tube coil preheated (to 300-500°F) by boiler or engine exhaust, to make up for some of the compression/expansion losses.
Haven't done the math, but depending on the air pressure and exhaust temp, that might "recoup" more energy than was put into compressing the air -- ie, brake for 200 feet, then run for 300 feet before switching back to steam. Or, decelerate from 60 mph, then accelerate to 70 mph on air, by recovering some extra waste heat in the process? Doubtful, though -- air compression temp would have to be lower than exhaust temp, and there are exhaust pressure losses.
For now, I'd bet on the hydraulic regenobrake system a la Ford. Still many problems, eg, you're only regen-braking with two wheels, how do you transition smoothly from 2-wheel regen braking to 4-wheel friction braking when the accumulator fills up, etc.. And will the equipment cost be less than that of the fuel saved? A worthwhile system seems way off in the future, if ever.
Intriguing possibilities, though. Ford claims their hydraulic system could increase city fuel mileage by 20-25%.
Peter</HTML>
Re: Regenerative Braking
Posted by: Pat Farrell (IP Logged)
Date: February 12, 2003 01:49PM
<HTML>Dear Peter, Two wheel braking? Seeing all of the 4WD SUVs running around, I would think that 4 wheel regenerative braking would not be such a challenge. The idea of keeping the compressed air out of the boiler doesn't make sense. Why keep it out? The compressed air could actually become as hot as the steam in the boiler once the air has been compressed. The compressed air could easily reach temperatures of 550 degrees F while being compressed. Coming down off the Trail Ridge Road in Estes Park, Colorado, I was using reverse braking and the temperature in my engine exceeded 550 degrees F. I know this to be a fact because my Cylestic TK1000 steam cylinder oil has a flash point of 550 degrees and it had became so hot that it had exceeded the flash point and the oil had turned to blue smoke coming from my engine. On compressing air, a great amount of heat is accumulated in the air while compressing the air and all air compressers have a cooling system to keep the generated heat to a minimum. Compressing the air without cooling the air, carrying the extra heat from the compressed air into the boiler couldn't do any harm to the reserve steam in the boiler as long as the compressed air temperature is at least up to the boiler's steam temperature. As Coburn Benson noted, since a steam engine with full steam pressure can spin the tires on a steamer, then it would be impossible for the same engine to put the same full air pressure back into the boiler with out wheel slippage. This is where a compound steam engine like the White steamer uses, could be used. The White used a simpling valve that changed the engine to either a simple engine or a compound engine. Using the simpling valve, one could drive the steamer simpled, and then the regenerative braking could be done in compound for the higher air pressure. Regenerative steamer braking is easier said than done, but it is feasible. I agree with David Nergaard with the Locomotive testing that was done, that economically speaking, the gains in fuel economy would not exceed the extra costs of the equipment and maintenance needed. SSsssteamer</HTML>
Re: Regenerative Braking
Posted by: Peter Heid (IP Logged)
Date: February 12, 2003 09:11PM
<HTML>My first attempt at regenerative braking will be electric just for the fact that it has been done many times and is well proven. Of course the vehicle will be required to have batteries enough for short term storage or the power will need to be bled off. From what I have gathered, there have been several steam vehicles that would have benefited from the application of this technology, Doble for one. Sure, you lose power with every conversion and costs go up with the addition of equiptment for the purpose but a 7% savings has been gained with electric brakes, better than throwing it away. There are some IC/electric hybrids designed with the smallest battery side possible and they work well. The control of electric braking can easily be acomplished with electric motor speed controllers that provide smooth, easily controlled braking at low cost. I have seen MOSFET speed controllers of 24 volt and 350 amp capacity sell for around $100.00 US on Ebay. When you consider the cost of the system, remember there are no wearing parts like brake pads or rotors with a purely electric brake. I can envision excess electrical power, beyond the battery storage capacity, used for heating or cooling purposes. Peltier junctions, though not very efficient can provide heat and cold for passanger comfort or other uses.
I don't expect regenerative braking to provide power for propulsion, only to ease the load of auxilliary equiptment and cut overall fuel consumption.
Peter Heid</HTML>
I don't expect regenerative braking to provide power for propulsion, only to ease the load of auxilliary equiptment and cut overall fuel consumption.
Peter Heid</HTML>
Re: Regenerative Braking
Posted by: Peter Brow (IP Logged)
Date: February 13, 2003 09:58AM
<HTML>Pat: Agree with you & Ben on wheel slippage. On keeping air out of the boiler, I am mainly thinking about corrosion avoidance. Most boilers are oil-coated inside, which gives some protection, but lots of air on hot steel, with water around too, and I'd expect much shorter boiler life. A separate air tank could be insulated and/or exhaust-flue heated, and could be relatively small. Keeping the air hot is the way to go, esp since the air would usually be used pretty soon after compressing. Also tend to agree with you & David on the IC exhaust steam recompressor system. Seems to be proven, saves fuel, and runs, but the cost/benefit calculation, as with all new & alternative technologies, is crucial, and may not be favorable in this case.
Full-time 4WD with regenerative braking would solve the brake-distribution problem, and has other advantages, though it increases equipment cost & eats more fuel in the drivetrain. The hydraulic regenerative system seems the most efficient/promising, IMO.
Peter: Electric regenerative braking for auxiliaries might pay off. For a small hobby system, it is affordable to give it a try, and results should be interesting.
Peter</HTML>
Full-time 4WD with regenerative braking would solve the brake-distribution problem, and has other advantages, though it increases equipment cost & eats more fuel in the drivetrain. The hydraulic regenerative system seems the most efficient/promising, IMO.
Peter: Electric regenerative braking for auxiliaries might pay off. For a small hobby system, it is affordable to give it a try, and results should be interesting.
Peter</HTML>
Re: Regenerative Braking
Posted by: Rolly Evans (IP Logged)
Date: February 13, 2003 10:41AM
<HTML>I think the easiest thing to do on a steam car is to pump water. Use an electric clutch when the brakes are activated, to engage the pumps and pump water into a pressurized tank. (Air over water). If the tank is maintained with higher air pressure then the boiler, the water can be used as feed water as needed. If you really wanted to slow down you could have a bank of pumps controlled by how hard you press on the break.
Rolly</HTML>
Rolly</HTML>
Re: Regenerative Braking
Posted by: David K Nergaard (IP Logged)
Date: February 13, 2003 12:36PM
<HTML>Pat, I have to back up Peter on the air in the boiler bit. All steam power plants work very hard to keep air out of the system, even a very small amount of oxygen in the boiler water causes major corrosion problems. When I pull old steel tubes from my Stanley boiler, most of the corrosion I find is at the water level, just where the oxygen concentration is highest. (Oxygen is heavier than steam.)</HTML>
Re: Regenerative Braking
Posted by: Pat Farrell (IP Logged)
Date: February 13, 2003 01:33PM
<HTML>Dear David, That is a very interesting finding that you have discovered about the corrosion being at the boiler's water level. I would guess that you are referring to the operating water level established by your water level automatic. The small time that air would be in the boiler while steaming is very small as compared to the time that your Stanley's boiler sits rusting away without a head of steam on the boiler. Thank you for your insight. SSsssteamer</HTML>
Re: Regenerative Braking
Posted by: Dick Vennerbeck (IP Logged)
Date: February 13, 2003 02:33PM
<HTML>I'd like to throw in a couple of items for thought on using compressed air for regenerative braking. If you pump air into a boiler that is sitting at 600 psi you will get 43 times the amount of oxygen normally available. (43 atmospheres) Assume that the temperature of the air out of the compressor is 300 deg F and the temperature of the steam is 600 deg F. The air would try to expand by twice and increase the pressure (Boyles Law). The pressure increase in the boiler would depend on the volume of air you had injected. Now assume that we are coasting along with a whole lot of stream and air in the boiler and we open the throttle. I'm not sure what happens next. The steam will enter the cylinders and expand at the same time the air will scream through the valves and drop in pressure cooling the mix very rapidly. What's the net result?
Dick</HTML>
Dick</HTML>
Re: Regenerative Braking
Posted by: Howard Randall (IP Logged)
Date: February 13, 2003 03:20PM
<HTML>I don't know without "doing the math" as they say. But as a precaution, better open the drip!</HTML>
Re: Regenerative Braking
Posted by: Pat Farrell (IP Logged)
Date: February 14, 2003 04:49AM
<HTML>From Stanley experience, air does not have the same expansion ratio as super heated steam by any means. It acts more like saturated steam than super heated steam. But it is still an expander of it's volume to achieve a lower pressure. No need to open the drip valve to vent the steam chest because of an oxygen enriched steam coming from the boiler. This would be a waste of steam cylinder oil of which the Stanley's slide valves need. "Still, when first steaming up, vent the steam chest to let out the lumps of water". On reverse braking, to releave the accumulated pressure in the steam chest by momentarily letting up on the reversing lever to "burp the baby", then push the reversing pedal back down to resume reverse braking. Do not open the steam chest Water that has been boiled, is lower on oxygen and is less apt to corrode the inside of the boiler than unboiled water. The point is, when you start your boiler out with a new filling of water, your steam is richer in oxygen immediately after the new filling, than later by occasionally adding compressed air to the oxygen depleted boiler water.</HTML>
Re: Regenerative Braking
Posted by: Tom Ward (IP Logged)
Date: February 19, 2003 04:14PM
<HTML>With 24 years of public transit driving behind me I believe that regenerative braking of any type is long overdue. At my transit system there is a full-time mechanic who works exclusively on brakes. Drums, rotors, shoes, and pads are used up at a much faster rate than a typical car. A bus rarely just cruises down the street but is either speeding up or slowing down. The ability to capture and reuse all that kinetic energy would definitely justify the capital cost probably within months.
There are roughly 75,000 new buses purchased by the federal taxpayers each year. The market is there for a steamer chassis that not only cuts pollution but also fuel and repair costs. Once the production lines for steam buses are up and running the cost of parts for hobbyists will drop.
As this discussion has shown there is no scientific reason a regenerative steam system isn't out there it's just political.</HTML>
There are roughly 75,000 new buses purchased by the federal taxpayers each year. The market is there for a steamer chassis that not only cuts pollution but also fuel and repair costs. Once the production lines for steam buses are up and running the cost of parts for hobbyists will drop.
As this discussion has shown there is no scientific reason a regenerative steam system isn't out there it's just political.</HTML>
Re: Regenerative Braking
Posted by: Caleb Ramsby (IP Logged)
Date: February 19, 2003 06:03PM
<HTML>I have given this issue some thought before and came upon the thought of using air a mediem and the expander as a pump. I had not given any thougth to containing the pumped air to use again just negating the usage of mechanical brakes.
I think that using a varying sized valve in the ports to control the effort the expander would require to move the air would give one a varience of braking effort. In other words if the valve was open larger it would let the air in easier and if it were smaller it would take more effort to fill up the chamber.
Pumping this air into a chamber that hold pressure and using that resistance would help also. I think that there would need to be a seperate system to contain and control the compressed air. If one wanted to use the compressed air to operate the engine again then things would get sort of complicated. Because as the air was used up the pressure exerted by it would drop and thus there would need to be a longer cut off or such to compensate for the drop in pressure to maintain the same power output. Then the crossover from air to steam would be a little tricky, if one wanted to keep the engine power and speed smooth.
Humm, what if one used a piston and sleeve to hold the compressed air. Then one could move the piston and change the chamber size to maintain the pressure wanted of the air. Then when it is filling the chamber could expand and when it is emptying it could contract. Thus having a predictable pressure to work with. What do you think about using a spring to hold the chamber at a given pressure? Mabey it would require a little motivation from a donkey engine? What do you all think about this idea?
Caleb Ramsby</HTML>
I think that using a varying sized valve in the ports to control the effort the expander would require to move the air would give one a varience of braking effort. In other words if the valve was open larger it would let the air in easier and if it were smaller it would take more effort to fill up the chamber.
Pumping this air into a chamber that hold pressure and using that resistance would help also. I think that there would need to be a seperate system to contain and control the compressed air. If one wanted to use the compressed air to operate the engine again then things would get sort of complicated. Because as the air was used up the pressure exerted by it would drop and thus there would need to be a longer cut off or such to compensate for the drop in pressure to maintain the same power output. Then the crossover from air to steam would be a little tricky, if one wanted to keep the engine power and speed smooth.
Humm, what if one used a piston and sleeve to hold the compressed air. Then one could move the piston and change the chamber size to maintain the pressure wanted of the air. Then when it is filling the chamber could expand and when it is emptying it could contract. Thus having a predictable pressure to work with. What do you think about using a spring to hold the chamber at a given pressure? Mabey it would require a little motivation from a donkey engine? What do you all think about this idea?
Caleb Ramsby</HTML>
Re: Regenerative Braking
Posted by: Caleb Ramsby (IP Logged)
Date: February 19, 2003 08:19PM
<HTML>Thinking more about this system. I believe it would work well to have two seperate feed lines to the steam chest, one from the boiler and one from the compressed air container. With a valve in each line near the steam chest one could switch from air to steam with a conected link system between the two valves. When the air container(piston in cylinder) get's close to empty the movement of the piston in the air container could be made to close the air valve and open the steam valve at the same time producing a smooth and automatic switch.
There would need to be a seperate actuater conected to the valves to switch when braking is done. There might need to be multiple containers or just one large one.
I have been trying to figure out how one could move the piston in the air container maintaining the wanted amount of pressure with the varying volume and think that a spring with a constant pressure should work very well. When the pressure of the air drops when the air is used the spring would push the piston in to keep the pressure the same and when the air is admited the spring would compress and expand the chamber keeping the pressure the same. The spring would obivously not need to be powered. Any other way of moving the piston I can think of would require power to move and control.
Do you guys see any problem with this idea?
What do you guys think about varying the valve opening during intake and exhaust of the air during braking to control the amount of resistance given by the expander(engine)?
I also think that along with the bus's, semi's would be a viable market for a good regenerative, quite, powerfull and clean burning steam system!
I think that in the semi and bus there would be a requirement for a donkey engine to run the lights and various systems when the vehicle is at idle. Which in a semi, is very often.
I think we may be on to something here!
Caleb Ramsby</HTML>
There would need to be a seperate actuater conected to the valves to switch when braking is done. There might need to be multiple containers or just one large one.
I have been trying to figure out how one could move the piston in the air container maintaining the wanted amount of pressure with the varying volume and think that a spring with a constant pressure should work very well. When the pressure of the air drops when the air is used the spring would push the piston in to keep the pressure the same and when the air is admited the spring would compress and expand the chamber keeping the pressure the same. The spring would obivously not need to be powered. Any other way of moving the piston I can think of would require power to move and control.
Do you guys see any problem with this idea?
What do you guys think about varying the valve opening during intake and exhaust of the air during braking to control the amount of resistance given by the expander(engine)?
I also think that along with the bus's, semi's would be a viable market for a good regenerative, quite, powerfull and clean burning steam system!
I think that in the semi and bus there would be a requirement for a donkey engine to run the lights and various systems when the vehicle is at idle. Which in a semi, is very often.
I think we may be on to something here!
Caleb Ramsby</HTML>
Re: Regenerative Braking
Posted by: Andy Patterson (IP Logged)
Date: February 25, 2004 08:45PM
<HTML>You can compress steam into water with rejecting a lot of heat some ware. Expansion and compression progress along a constant entropy line. The differance between expansion and compression is direction of work conversion. During compression you are converting mechanical energy into heat. The steam temperature increasses during compression. I have heard this story before. It must be getting confused with what they were actually doing.
Though I think that regenerative breaking could be possable with some type of cold water pressurized accumulator. Breaking would pump water into the accumulator.</HTML>
Though I think that regenerative breaking could be possable with some type of cold water pressurized accumulator. Breaking would pump water into the accumulator.</HTML>
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