1 Steam Cars : Phorum
General Steam Car topics
Theoretical minimum steam rate
Posted by: tom ward (IP Logged)
Date: October 18, 2002 11:38PM
<HTML>Is there a theoretical minimum amount of steam per HP/hr? Assume an operating pressure of 1000 psi at 1000F.</HTML>
Re: Theoretical minimum steam rate
Posted by: George Nutz (IP Logged)
Date: October 19, 2002 06:11PM
<HTML>Tom,
Yes there is but expanding to absolute zero pressure is not possible as the engine would not exhaust into that same condensor pressure. If one were to theoretically take one pound of steam and calculate its "push"/constant enthalpy work it would produce .0605HP/#steam per hour exhausting into 0.00psia. Thus a 100% admission engine that had no enthalpy/expansive work done would have a steam rate of 16.53#/HP-HR. If one had expansion down to the saturated zone with 0% losses of any kind it would expand to 18.6psia and the additional work done by the enthalpy drop would be about
.1364 HP/#-HR. The total theoretical amount of work done would be .197#/HP-HR or a steam rate of 5.08#/HP-HR. It is amazing that the Williams engine, with its very low clearance volume, unaflow non-counterflow exhaust and automatic compression relief valve achieved something like 6.5#/HP-HR on a dyno, probably the lowest steam rate of any actual automobile engine. Engineer Jerry Peoples has written a theoretical paper on the Williams cycle that is available.
Best, George</HTML>
Yes there is but expanding to absolute zero pressure is not possible as the engine would not exhaust into that same condensor pressure. If one were to theoretically take one pound of steam and calculate its "push"/constant enthalpy work it would produce .0605HP/#steam per hour exhausting into 0.00psia. Thus a 100% admission engine that had no enthalpy/expansive work done would have a steam rate of 16.53#/HP-HR. If one had expansion down to the saturated zone with 0% losses of any kind it would expand to 18.6psia and the additional work done by the enthalpy drop would be about
.1364 HP/#-HR. The total theoretical amount of work done would be .197#/HP-HR or a steam rate of 5.08#/HP-HR. It is amazing that the Williams engine, with its very low clearance volume, unaflow non-counterflow exhaust and automatic compression relief valve achieved something like 6.5#/HP-HR on a dyno, probably the lowest steam rate of any actual automobile engine. Engineer Jerry Peoples has written a theoretical paper on the Williams cycle that is available.
Best, George</HTML>
Re: Theoretical minimum steam rate
Posted by: Caleb Ramsby (IP Logged)
Date: October 19, 2002 06:36PM
<HTML>On the same note. Assuming there are no heat loses inside the engine and a 5" stroke. Steam at 1000 psi. and 1000 F. What is the slowest operable/sustainable rpm that the engine could have?
Would this just be a matter of how little pressure(very little throttle) and short of a cutoff one could use?
Would the determining factor be how long the steam could be left expanding in the engine without becoming wet or condensing?
Thus a factor of the steam expansion rate to the piston speed?
Caleb Ramsby</HTML>
Would this just be a matter of how little pressure(very little throttle) and short of a cutoff one could use?
Would the determining factor be how long the steam could be left expanding in the engine without becoming wet or condensing?
Thus a factor of the steam expansion rate to the piston speed?
Caleb Ramsby</HTML>
Re: Theoretical minimum steam rate
Posted by: David K Nergaard (IP Logged)
Date: October 19, 2002 07:46PM
<HTML>The minimum sustainable speed is zero. The steam consumption at that speed is the sum of leakage past piston rings etc. and condensation due to heat losses from the cylinder.
For an engine to start from zero speed, at least one cylinder must be in a condition to receive steam (i. e. inlet valve open and exhaust valve closed) AND produce useable torque (i. e. not on dead center).
For a running engine, any cutoff that provides enough average torque to carry the load will work provided the momentum of the load and/or fly wheel is sufficient to keep things moving until the next time an inlet valve opens.
The minimum speed of an I. C. engine is set by the size of the fly wheel, it must have enough momentum to carry the engine over the next compreesion stroke.
With a multicylinder steam engine, with cutoff late enough so inlet valve openings over lap, a flywheel may not be needed.</HTML>
For an engine to start from zero speed, at least one cylinder must be in a condition to receive steam (i. e. inlet valve open and exhaust valve closed) AND produce useable torque (i. e. not on dead center).
For a running engine, any cutoff that provides enough average torque to carry the load will work provided the momentum of the load and/or fly wheel is sufficient to keep things moving until the next time an inlet valve opens.
The minimum speed of an I. C. engine is set by the size of the fly wheel, it must have enough momentum to carry the engine over the next compreesion stroke.
With a multicylinder steam engine, with cutoff late enough so inlet valve openings over lap, a flywheel may not be needed.</HTML>
Theoretical minimum rate
Posted by: c benson (IP Logged)
Date: October 19, 2002 08:32PM
<HTML>And in fact the entire car effectivly becomes part of the ''flywheel'' mass as it is geared direct,,,/// Relative to gas cars,,on this,,,I rode w/6 people in a Packard V12 a '39 i think,,the owner Jack Sipel from Phillie/[who was at Harvard Med school then] in highgear at a slow walk,,, SLOW,,,steped on the brake,,,,,STOPPED,, Just momentarily,,,The cyl had pressure apon releasing the brake,,the piston was pushed down by the pressure in the cyl,,Just enough to allow the next cyl to fire [60 crank deg] and we were umder way,,,,XXXX we didnt believe what we had witnessed,,,,Jack being a good sport ,,did it again 2 more times,,,He had 2 Packards a '17 &39 SO what we can take from this is temp of cyl is important,,,an' how long U expect the cyl to hold pressure,,,But is this of any importance We usually want to do a HOLE SHOT ,,,an as long as its controlable to get it into a parkin spot its ok,, A user friendly Stanley throttle is controllable to the degree that to tell if U are moving or not , U may need to line up the edge of the running board w/ blades of grass,,,this I discovered when I drove Ralph VanDine's '13 10hp for the first time ,,,,,The word controllable comes to have a different meaning,,XXXX,The central drum on the LaMont probably could pass clean through a modern car//left to right[not lengthwise] if U got a sling shot powerful enough to launch, it,,,,,Yeh it could explode,,,but what pressure did you have in mind,,,,,Gas car flywheels also''explode'' but it is not a common occurance,,,,Cheers Ben</HTML>
Re: Theoretical minimum rate
Posted by: Caleb Ramsby (IP Logged)
Date: October 20, 2002 05:42PM
<HTML>So what it boils down to is that as long as the steam in the cylinder does not lose too much energy to convection through the engine. Then the steam will keep pushing against the expander even after a long while.
So the limiting factor must be the difference between the pressure applied against the expander from the steam and the resistance it is attempting to over come.
So if the expander was not under any load beside it's own parasitic forces then a very minute amount of steam at a throttled down pressure would still give a very slow expander movement.
I am just very curious about all of the dynamic actions that are involved in even the most absurd scenarious.
One reason I was wondering, is because I forsee the viable application of a steam engine in semi's. They need to be able to move at very slow speeds at times. I do belive though that a semi equiped with a steam engine will still require a three speed axle. First gear with a max speed of around 90 mph, highway, second gear with a max speed of 50 mph, town and a third gear that maxs out around 10 mph. The last gear would be for moving houses and such. No, I am not talking about mobile homes. I am talking about three story houses. I have personly seen many a semi pulling a house that blocked two lanes and the sholder, some being pulled up a good sized hill as well. The third gear would give the torque multiplication that would be needed to relieve the tremendous stress's that would be imparted upon the expander. Thus, not only increasing the engines usable power but giving the engine a longer life span as well.
Another application that I believe the steam engine would fit into VERY well is snowmobiles and motorcycles. These vehicles are almost never talked about in the same sentance as the steam engine. The bigest advantage that the steam engine would have over the IC engine would be silence! If the engine were to be condensed, the situation of snowmobiles and off road motorcycles adding to the ever growing noise polution would be great decreased. It is very hard to envision a snowmobile flying by without also envisioning the ear shattering sound of those very high piched engines.
I think that the small engine market has one of the greatest potentials for the implementation of the modern steam engine. With the heavy duty engines needed for industrial vehicles coming in second.
Benson,
The thing that bothers me about the Lamont boiler is all of that reserve energy being located in one place(danger). The pressure I would use is the greatest obtaniable without drasticly increasing cost of materials and inducing excessive weight but when steam is being discussed basicly any pressure above that of the atmosphere has the power to kill. Yes, a flywheel can explode and I have know a few gear heads that have had it happen to them. None of them were hurt much, besides the guy I heard about that hadn't installed a containment shield around the transmission and lost both his legs.
I see saftey as the most important consideration in the design of anything. I always try to conjure up the most tramatic situation that that any of my creations could encounter.
For a semi it goes like this, fifty years have gone by since the installation of the Lamont boiler. The boiler although being made of stainless has had some corrosion develop inside of the reserve tank. The boiler has had very little proper maintance if any at all. The driver has been pushing the boiler at 1 1/2 times the "maximum" pressure for many years(he modified the saftey valves). All of a sudden the burner gets stuck at full blast, being at a stop light the driver notices the rapidly rising pressure. He had mangled the saftey valves and now they have decided not to open at all. The driver knows he has to do something and desides to push the throttle wide open to realive the buildup of steam, hauling well over the legal limit of weight he thinks this will work for a while. This was a mistake because now the throttle won't close either. Because of the lack of maintance the usualy powerfull brakes of the semi can't stop it or even slow it down. So now the semi is going 60 mph and speeding up. Uh oh, the driver has a heart attack and the semi steers itself towards a very large brick building, which happens to be a school. School, coincidently, just let out and most of the kids are still hanging around outside the school. The kids run out of the way as the semi rams nose first into a corner of the very strong brick building. None of the kids were hurt by the semi physicly hitting the building and magicly the spraying bricks don't hit them, remember they ran out of the way. But, if in this scenario the reserve tank for the Lamont boiler didn't hold up, then I would consider it an unsafe design. Oh, don't forget the guy that a few years ago got angry with this particular semi driver and ground away a majority of the wall thickness of the reserve tank.
This may seem to most of you as an absurdly harsh scenario, which it is, but although I have only lived 23 years, I have learned that truth is much stranger than fiction. If I can come up with this situation with only my imagination, thus fiction, than there is a great chance that this is not the most torturous situation that a boiler could pheasibly encounter!
Caleb Ramsby</HTML>
So the limiting factor must be the difference between the pressure applied against the expander from the steam and the resistance it is attempting to over come.
So if the expander was not under any load beside it's own parasitic forces then a very minute amount of steam at a throttled down pressure would still give a very slow expander movement.
I am just very curious about all of the dynamic actions that are involved in even the most absurd scenarious.
One reason I was wondering, is because I forsee the viable application of a steam engine in semi's. They need to be able to move at very slow speeds at times. I do belive though that a semi equiped with a steam engine will still require a three speed axle. First gear with a max speed of around 90 mph, highway, second gear with a max speed of 50 mph, town and a third gear that maxs out around 10 mph. The last gear would be for moving houses and such. No, I am not talking about mobile homes. I am talking about three story houses. I have personly seen many a semi pulling a house that blocked two lanes and the sholder, some being pulled up a good sized hill as well. The third gear would give the torque multiplication that would be needed to relieve the tremendous stress's that would be imparted upon the expander. Thus, not only increasing the engines usable power but giving the engine a longer life span as well.
Another application that I believe the steam engine would fit into VERY well is snowmobiles and motorcycles. These vehicles are almost never talked about in the same sentance as the steam engine. The bigest advantage that the steam engine would have over the IC engine would be silence! If the engine were to be condensed, the situation of snowmobiles and off road motorcycles adding to the ever growing noise polution would be great decreased. It is very hard to envision a snowmobile flying by without also envisioning the ear shattering sound of those very high piched engines.
I think that the small engine market has one of the greatest potentials for the implementation of the modern steam engine. With the heavy duty engines needed for industrial vehicles coming in second.
Benson,
The thing that bothers me about the Lamont boiler is all of that reserve energy being located in one place(danger). The pressure I would use is the greatest obtaniable without drasticly increasing cost of materials and inducing excessive weight but when steam is being discussed basicly any pressure above that of the atmosphere has the power to kill. Yes, a flywheel can explode and I have know a few gear heads that have had it happen to them. None of them were hurt much, besides the guy I heard about that hadn't installed a containment shield around the transmission and lost both his legs.
I see saftey as the most important consideration in the design of anything. I always try to conjure up the most tramatic situation that that any of my creations could encounter.
For a semi it goes like this, fifty years have gone by since the installation of the Lamont boiler. The boiler although being made of stainless has had some corrosion develop inside of the reserve tank. The boiler has had very little proper maintance if any at all. The driver has been pushing the boiler at 1 1/2 times the "maximum" pressure for many years(he modified the saftey valves). All of a sudden the burner gets stuck at full blast, being at a stop light the driver notices the rapidly rising pressure. He had mangled the saftey valves and now they have decided not to open at all. The driver knows he has to do something and desides to push the throttle wide open to realive the buildup of steam, hauling well over the legal limit of weight he thinks this will work for a while. This was a mistake because now the throttle won't close either. Because of the lack of maintance the usualy powerfull brakes of the semi can't stop it or even slow it down. So now the semi is going 60 mph and speeding up. Uh oh, the driver has a heart attack and the semi steers itself towards a very large brick building, which happens to be a school. School, coincidently, just let out and most of the kids are still hanging around outside the school. The kids run out of the way as the semi rams nose first into a corner of the very strong brick building. None of the kids were hurt by the semi physicly hitting the building and magicly the spraying bricks don't hit them, remember they ran out of the way. But, if in this scenario the reserve tank for the Lamont boiler didn't hold up, then I would consider it an unsafe design. Oh, don't forget the guy that a few years ago got angry with this particular semi driver and ground away a majority of the wall thickness of the reserve tank.
This may seem to most of you as an absurdly harsh scenario, which it is, but although I have only lived 23 years, I have learned that truth is much stranger than fiction. If I can come up with this situation with only my imagination, thus fiction, than there is a great chance that this is not the most torturous situation that a boiler could pheasibly encounter!
Caleb Ramsby</HTML>
Re: Theoretical minimum rate
Posted by: Mike Bennett (IP Logged)
Date: October 20, 2002 06:05PM
<HTML>Yea, Fred Marriots' boiler tumbled down Daytona Beach and did not explode!?!</HTML>
Relativ' trivia ??
Posted by: c benson (IP Logged)
Date: October 20, 2002 09:44PM
<HTML>The semi drivers are to a man,,more responsible than the lot of 4wheel/skimbobile thrill-seekers around these parts,,,,,I'll take my chances w/ the semi lot,,,,,,gasoline cars,,,where did that expression Crash in' burn come from??? XXXX Tranny,is necessary in your extreme use,,,WHEN a steamer breaks traction it usually spins the wheel around 3 or 4 times before steam chest pressure gets below spinning wheel friction,,,,that is rolling friction has a better bite than after its broken loose,,,,so once its loose it continues for a rev or 3,,,,THERE is however wonderful control RIGHT up to this point,,,,Then the suprise,,,,,chuf chuf chuf chuf very fast,,,The old timers will remember the sound as a loco would break traction gettin' under way,,,,,music to us kids,,,,I can still remember the steamers on the main line ,,Boston to Troy NY When the side rods got to 3/8'' play on the crankpins they were sidelined to yard duty I could hear em leave the station 4 mi away,,,,Wonder what the impact loadin on the crank was,,,Experience not engineering here I think,,,Cheers Ben</HTML>
throttle control/burn out
Posted by: Caleb Ramsby (IP Logged)
Date: October 20, 2002 10:30PM
<HTML>Mike,
You are completely correct. One possible difference is that Fred Marriot's boiler was most likely modified to accept the high pressure that he used, although I could be wrong. His boiler was also most likely new and made soley for his race car. Either way I have always been most impressed with the fact that at the estimated 180 mph the boiler did not explode.
Sorry about the excessive bable about explosions but if I were to tell a person who is completely ignorant about anything steam that the boiler in the car they are about to ride in can explode although it would take forces that excede those known to man. They would only hear the "explode" part.
I think that a boiler that is constructed of varous high circulation clusters of tubes would be free from "explosion" yet still contain the reserve energy that makes a steam vehicle so great.
Benson,
Yeah, I would definatly trust a semi driver over a snowmobiler just after a thrill. I wrote about a semi driver because a snowmobiler would only effect a deer.
I was in no way implying that steam vehicles are more dangerous than IC vehicles. There was just recently a recal and repair issued for police cars that would literly burst into flames when struck from the rear end.
I think that either diesel fuel because of availability and greatly decreased chance of explosion or kerosene for a steam car.
So after the locomotives engineer broke the wheels loose with excess power did he immediatly decrease the throttle so the wheels didn't keep on spining although at that point the wheels could actualy transfer more power to the rails. In varous old west movies and programs about locomotives I once saw a train that started spining it's wheels like mad, at least 15 times. Any ideas what was going on there?
3/8" play on the crankpins!!! That is awesome! That was when things were made to take it and not talk back. How did they keep the siderod and crankpin asembly oiled with that much clearence. Actualy I wonder how much they oiled them at all. I have seen water fountains that(the ones that you drink from) could spray their stream of water right between the siderod asembly. Mabey that is why they would fix them at that point.
One of my buddies has a Searay that has a fiberglass hull. It was their first model to have one and they made the hull thickness about 3-4 times as thick as needed because they just didn't know. Great for cutting waves!
Caleb Ramsby</HTML>
You are completely correct. One possible difference is that Fred Marriot's boiler was most likely modified to accept the high pressure that he used, although I could be wrong. His boiler was also most likely new and made soley for his race car. Either way I have always been most impressed with the fact that at the estimated 180 mph the boiler did not explode.
Sorry about the excessive bable about explosions but if I were to tell a person who is completely ignorant about anything steam that the boiler in the car they are about to ride in can explode although it would take forces that excede those known to man. They would only hear the "explode" part.
I think that a boiler that is constructed of varous high circulation clusters of tubes would be free from "explosion" yet still contain the reserve energy that makes a steam vehicle so great.
Benson,
Yeah, I would definatly trust a semi driver over a snowmobiler just after a thrill. I wrote about a semi driver because a snowmobiler would only effect a deer.
I was in no way implying that steam vehicles are more dangerous than IC vehicles. There was just recently a recal and repair issued for police cars that would literly burst into flames when struck from the rear end.
I think that either diesel fuel because of availability and greatly decreased chance of explosion or kerosene for a steam car.
So after the locomotives engineer broke the wheels loose with excess power did he immediatly decrease the throttle so the wheels didn't keep on spining although at that point the wheels could actualy transfer more power to the rails. In varous old west movies and programs about locomotives I once saw a train that started spining it's wheels like mad, at least 15 times. Any ideas what was going on there?
3/8" play on the crankpins!!! That is awesome! That was when things were made to take it and not talk back. How did they keep the siderod and crankpin asembly oiled with that much clearence. Actualy I wonder how much they oiled them at all. I have seen water fountains that(the ones that you drink from) could spray their stream of water right between the siderod asembly. Mabey that is why they would fix them at that point.
One of my buddies has a Searay that has a fiberglass hull. It was their first model to have one and they made the hull thickness about 3-4 times as thick as needed because they just didn't know. Great for cutting waves!
Caleb Ramsby</HTML>
Re: throttle control/burn out
Posted by: David K Nergaard (IP Logged)
Date: October 20, 2002 11:33PM
<HTML>15 revs of spin! THAT was for the camera! No real engineer would let that happen if he could avoid it. I remember an "Iron Horse Ramble" on the Reading line where the engine hit some wet leaves going about 40 mph. Still only a couple of turns and he was shut off.
As for Marriott's boiler, it was a special light weight version, not nearly as strong as the production versions. Still, no boiler failure in the accident although carrying 1300 psi.
I have always considered a gasoline tank as a pontential bomb. But now they talk of nateral gas and hydrogen tanks...</HTML>
As for Marriott's boiler, it was a special light weight version, not nearly as strong as the production versions. Still, no boiler failure in the accident although carrying 1300 psi.
I have always considered a gasoline tank as a pontential bomb. But now they talk of nateral gas and hydrogen tanks...</HTML>
Re: throttle control/burn out
Posted by: David K Nergaard (IP Logged)
Date: October 21, 2002 11:07AM
<HTML>How about this as an alternative to a multi-speed transmission: the following figures are for a uniflow engine using steam at 800 psi. and atmospheric exhaust.
Torques are in proportion to the Mean Effective Pressure.
0-8 mph. 75 % cutoff, MEP about 700 psi. efficiency; poor but acceptable.
0-25 mph. 25 % cutoff, MEP 335 psi. efficiency; good, better than a Stanley.
0-50 mph. 12 % cutoff, MEP 200 psi. efficiency; better than a White.
0-? mph. 6 % cutoff, MEP 90 psi. efficiency; very good, possibly better than a Doble.
A nearly 10-1 range in torque without change of gear!
As for the suggested crash senario, is the truck not fitted with an "ignition" switch? Can't the driver simply turn off the switch and kill the burner? In any case, the automatic boiler controls should have shut down the burner long before it reaches the pressure where the safety would blow. As an example, Stanley automatics are usually set to shut off the burner at or less than 600 psi. but the safety valve is set for about 700.</HTML>
Torques are in proportion to the Mean Effective Pressure.
0-8 mph. 75 % cutoff, MEP about 700 psi. efficiency; poor but acceptable.
0-25 mph. 25 % cutoff, MEP 335 psi. efficiency; good, better than a Stanley.
0-50 mph. 12 % cutoff, MEP 200 psi. efficiency; better than a White.
0-? mph. 6 % cutoff, MEP 90 psi. efficiency; very good, possibly better than a Doble.
A nearly 10-1 range in torque without change of gear!
As for the suggested crash senario, is the truck not fitted with an "ignition" switch? Can't the driver simply turn off the switch and kill the burner? In any case, the automatic boiler controls should have shut down the burner long before it reaches the pressure where the safety would blow. As an example, Stanley automatics are usually set to shut off the burner at or less than 600 psi. but the safety valve is set for about 700.</HTML>
Re: throttle control/burn out
Posted by: Caleb Ramsby (IP Logged)
Date: October 21, 2002 01:21PM
<HTML>David,
The fuels that "they" are trying to get used in cars is absurd! Most of their alternative fuels are harder to produce and require a tank that is much more dangerous than an old fire tube boiler.
One interisting fuel that is rarly discused is boron. There is a great site all about it. [www.eagle.ca] It is an interisting fuel but it has many draw backs which in a way make it so great. If I recal correctly it requires 100 bar of pressure to ignite and burns most effeciently with pure oxygen! This is good and bad. It makes the use of it very complicated and diffecult but it can be stored in boxes and even survive being in a fire. It would be used in the form of a coil of wire.
The various cutoff's would defenitaly be usefull and would supply the increased torque. But, it would not relieve the stresses exerted on the engine in extreme conditions. For semi's the use of a multi speed axle that is hydralicly shifted would be utilising standard equipment.
In cars, motorcycles, snowmobiles and even mass transit bus's there would be no real need for anything more than a single gear with a variety of cutoff's for various conditions like you described.
In any hyphothetical senario I alawys assume that what should work and happen doesn't and what shouldn't happen does.
Caleb Ramsby</HTML>
The fuels that "they" are trying to get used in cars is absurd! Most of their alternative fuels are harder to produce and require a tank that is much more dangerous than an old fire tube boiler.
One interisting fuel that is rarly discused is boron. There is a great site all about it. [www.eagle.ca] It is an interisting fuel but it has many draw backs which in a way make it so great. If I recal correctly it requires 100 bar of pressure to ignite and burns most effeciently with pure oxygen! This is good and bad. It makes the use of it very complicated and diffecult but it can be stored in boxes and even survive being in a fire. It would be used in the form of a coil of wire.
The various cutoff's would defenitaly be usefull and would supply the increased torque. But, it would not relieve the stresses exerted on the engine in extreme conditions. For semi's the use of a multi speed axle that is hydralicly shifted would be utilising standard equipment.
In cars, motorcycles, snowmobiles and even mass transit bus's there would be no real need for anything more than a single gear with a variety of cutoff's for various conditions like you described.
In any hyphothetical senario I alawys assume that what should work and happen doesn't and what shouldn't happen does.
Caleb Ramsby</HTML>
Re: Theoretical minimum rate
Posted by: tom ward (IP Logged)
Date: October 21, 2002 02:11PM
<HTML>I wouldn't build a boiler without a layer of carbon fiber epoxied to its shell. One thin layer has a burst strength of 58,000 psi!</HTML>
Re: Theoretical minimum rate
Posted by: Mike Bennett (IP Logged)
Date: October 21, 2002 02:46PM
<HTML>Tom,
Great Idea! If you are going around a circumference, why not band a layer of unidirectional kevlar under the CF? The are synergistic together, as the Kevlar has a high tensile and can be compatable with some of the same epoxies as the CF.
Regards,
Mike</HTML>
Great Idea! If you are going around a circumference, why not band a layer of unidirectional kevlar under the CF? The are synergistic together, as the Kevlar has a high tensile and can be compatable with some of the same epoxies as the CF.
Regards,
Mike</HTML>
Re: Theoretical minimum rate
Posted by: Tim Senior (IP Logged)
Date: October 21, 2002 05:42PM
<HTML>Small query. Whats the maximum working temperature of epoxy resin</HTML>
Re: Theoretical minimum rate
Posted by: George Nutz (IP Logged)
Date: October 21, 2002 05:52PM
<HTML>Tom,
Better check the ability of the epoxy to hold it together @ 500 degrees F saturated temperature. The old wire wrapping routine is much stronger, piano wire has a strength of over 300,000psi. A 8" pipe drum/schedule 80/thickness .500" would have a 4/1 factor of safety @ 1000psi based upon its minimum yield strength without any additional coating for SA-53 low carbon steel. The wire allows one to prestress in compression the drum to give it a bigger factor of safety whereas the epoxy would not, check the relative coefficients of thermal expansion of whatever you apply----stresses must be calculated at operating temperature.
Anyone crazy enough to take a pick axe to a boiler drum(it wouldn't penetrate) might as well practice on a oxygen bottle at full pressure(it was not you). As others have said the gasoline tank on a conventional car is more dangerous. This thread is going way off the thread topic by the way.
A boiler control/safety thread would be more ideal for some of it and we do have many previous threads more in line where this "theoretical steam rate" thread possibly is not a an appropriate title. This website is such a goldmine of information and discussion that everyone has the opportunity to "read up" on the older threads where so much has already been posted. I find myself going back at times to re-read some of the very valuable input of others.
Best, George</HTML>
Better check the ability of the epoxy to hold it together @ 500 degrees F saturated temperature. The old wire wrapping routine is much stronger, piano wire has a strength of over 300,000psi. A 8" pipe drum/schedule 80/thickness .500" would have a 4/1 factor of safety @ 1000psi based upon its minimum yield strength without any additional coating for SA-53 low carbon steel. The wire allows one to prestress in compression the drum to give it a bigger factor of safety whereas the epoxy would not, check the relative coefficients of thermal expansion of whatever you apply----stresses must be calculated at operating temperature.
Anyone crazy enough to take a pick axe to a boiler drum(it wouldn't penetrate) might as well practice on a oxygen bottle at full pressure(it was not you). As others have said the gasoline tank on a conventional car is more dangerous. This thread is going way off the thread topic by the way.
A boiler control/safety thread would be more ideal for some of it and we do have many previous threads more in line where this "theoretical steam rate" thread possibly is not a an appropriate title. This website is such a goldmine of information and discussion that everyone has the opportunity to "read up" on the older threads where so much has already been posted. I find myself going back at times to re-read some of the very valuable input of others.
Best, George</HTML>
Re: Theoretical minimum rate
Posted by: Rolly Evans (IP Logged)
Date: October 22, 2002 08:12AM
<HTML>Maximum Allowable Working Pressures for common boiler tube sizes, SA178A or SA192, where expanded into drums or headers. From ASME Boiler & Pressure Vessel Code, Section I, Table PWT-10. For 1.250 OD boiler tube with .105 Wall is rated at 1980 PSI.
The power plant on the Cape cod Cannel operates at 4000 PSI and 1200F. The one on L street in Boston is 3600 PSI at 1200F.
I see no reason to abandon good standards that have maintained safety for so long.</HTML>
The power plant on the Cape cod Cannel operates at 4000 PSI and 1200F. The one on L street in Boston is 3600 PSI at 1200F.
I see no reason to abandon good standards that have maintained safety for so long.</HTML>
Re: Theoretical minimum rate
Posted by: David K Nergaard (IP Logged)
Date: October 22, 2002 10:55AM
<HTML>In Re: "extreme stresses": a uniflow engine is designed to take steam at full boiler pressure during each and every stroke. Thus, the stresses are not significantly worse at long cutoff than at short, they merely endure for a longer percentage of the stroke. There is only one advantage to be gained by using a transmission; the ability to use a more efficient cutoff when moving slowly. This is significant only if you intend the primary use to be slow drags but insist on going at turnpike speeds between jobs and the jobs are a thousand miles apart!</HTML>
Re: Theoretical minimum steam rate
Posted by: tom ward (IP Logged)
Date: October 22, 2002 06:23PM
<HTML>Perhaps my understanding of physics may be off.
1 HP/hr = 2545 btu
steam at 1000 psi and 1000F needs 1505 btu/lb
2545/1505 = 1.69
Carnot efficiency at 1000F source and 100F sink comes to 61%
Inverse of 61% =1.63
1.63 x 1.69 = 2.77 lbs/HP-hr</HTML>
1 HP/hr = 2545 btu
steam at 1000 psi and 1000F needs 1505 btu/lb
2545/1505 = 1.69
Carnot efficiency at 1000F source and 100F sink comes to 61%
Inverse of 61% =1.63
1.63 x 1.69 = 2.77 lbs/HP-hr</HTML>
Re: Theoretical minimum steam rate
Posted by: George Nutz (IP Logged)
Date: October 22, 2002 07:50PM
<HTML>Tom,
"You ain't gonna get there from heah" as thay would say in New Hampshire.
My first sentence of previous post says why. Good luck on expanding to 100% water to get that great steam rate of 2.77#/HP-HR ;>). Unfortunately in real life we have all that exhaust heat to be subtracted from the 1505, possibly I misconstrued your question to begin with.
Best, George</HTML>
"You ain't gonna get there from heah" as thay would say in New Hampshire.
My first sentence of previous post says why. Good luck on expanding to 100% water to get that great steam rate of 2.77#/HP-HR ;>). Unfortunately in real life we have all that exhaust heat to be subtracted from the 1505, possibly I misconstrued your question to begin with.
Best, George</HTML>
Re: Theoretical minimum steam rate
Posted by: tom ward (IP Logged)
Date: October 24, 2002 07:09AM
<HTML>The key word in the original question is THEORETICAL. I doubt that 2.77 will be seen in the next hundred years. This is more of a thought experiment to discover an ideal to measure real experiments against. Reaching 3 times that rate would be a more reasonable goal.</HTML>
Re: Theoretical minimum steam rate
Posted by: George Nutz (IP Logged)
Date: October 24, 2002 10:30AM
<HTML>Tom,
Than you are correct if you could make an engine expand down to 32 degrees F with zero enthalpy and converting all the steam to icy water which is impossible as the total expanded volume would be the water volume that was admitted as steam! However you only gave starting conditions and not ending ones so I had to choose one. We could make an ice engine.. Even this figure is questionable as steam tables give relative enthapies and not absolute enthalpies to minus 463F so you are looking at a relative theoretical figure. My "theoretical" number was for an engine without friction/heat loss/any irreversability that would be capable of working without getting into the wet range as stated.
Best, George</HTML>
Than you are correct if you could make an engine expand down to 32 degrees F with zero enthalpy and converting all the steam to icy water which is impossible as the total expanded volume would be the water volume that was admitted as steam! However you only gave starting conditions and not ending ones so I had to choose one. We could make an ice engine.. Even this figure is questionable as steam tables give relative enthapies and not absolute enthalpies to minus 463F so you are looking at a relative theoretical figure. My "theoretical" number was for an engine without friction/heat loss/any irreversability that would be capable of working without getting into the wet range as stated.
Best, George</HTML>
Re: Theoretical minimum steam rate
Posted by: William L. Petitjean, P.E. (IP Logged)
Date: November 30, 2002 05:13AM
<HTML>Hi Tom:
The best way to check minimum theoretical steam rates is to get a good, large copy of the Mollier Chart and learn to read it. The best you can do is go vertically from your inlet conditions to the exhaust condition (constant entropy, or "isentropic expansion"). This gives you the maximum BTU's that can be extracted as work in a Rankine cycle heat engine. Since 2,454 BTU's equal 1 horsepower hour, you can calculate the steam rate in lbs per hp. hr. from the maximum "available energy" obtainable at your conditions.
You cannot exceed the maximum available energy shown on the Mollier chart because you can only convert heat to mechanical work if it exhibits a sensible change of temperature and volume that will push a piston to turn a crankshaft. The very significant latent heat of vaporization cannot be utilized because it changes the energy state of water without any sensible temperature or volume change -- this energy must be discharged to the heat sink (atmosphere) and therefore must be charged to the engine with a resulting reduction in thermal efficiency.
If you get a Mollier Chart I can help you decipher the myriad lines that drive many people mad.
Bill Petitjean</HTML>
The best way to check minimum theoretical steam rates is to get a good, large copy of the Mollier Chart and learn to read it. The best you can do is go vertically from your inlet conditions to the exhaust condition (constant entropy, or "isentropic expansion"). This gives you the maximum BTU's that can be extracted as work in a Rankine cycle heat engine. Since 2,454 BTU's equal 1 horsepower hour, you can calculate the steam rate in lbs per hp. hr. from the maximum "available energy" obtainable at your conditions.
You cannot exceed the maximum available energy shown on the Mollier chart because you can only convert heat to mechanical work if it exhibits a sensible change of temperature and volume that will push a piston to turn a crankshaft. The very significant latent heat of vaporization cannot be utilized because it changes the energy state of water without any sensible temperature or volume change -- this energy must be discharged to the heat sink (atmosphere) and therefore must be charged to the engine with a resulting reduction in thermal efficiency.
If you get a Mollier Chart I can help you decipher the myriad lines that drive many people mad.
Bill Petitjean</HTML>
Re: Theoretical minimum steam rate
Posted by: William L. Petitjean, P.E. (IP Logged)
Date: November 30, 2002 05:16AM
<HTML>Hi Tom:
Oops! There are 2,545 BTU per hp. hr., not 2,454 as I posted a few minutes ago.
Bill Petitjean</HTML>
Oops! There are 2,545 BTU per hp. hr., not 2,454 as I posted a few minutes ago.
Bill Petitjean</HTML>
Re: Theoretical minimum steam rate
Posted by: G. B. Gilbert (IP Logged)
Date: December 02, 2002 05:00AM
<HTML>There are some Mollier charts in English and metric units here:
[www.chemicalogic.com];
[www.chemicalogic.com];
Re: Theoretical minimum steam rate
Posted by: Andy Patterson (IP Logged)
Date: April 15, 2004 08:12PM
<HTML>Hi Bill
Bill, "The very significant latent heat of vaporization cannot be utilized because it changes the energy state of water without any sensible temperature or volume change"
There is a volume change. Latent heat of vaporization does work. You can figure the work done by a Rankine using the conseveration of energy principal or by calculating the work done by the seperate processes that make up the cycle. The work done during inlet at constant pressure is actually coming for that "Heat of vaporazation". The work done during the expansion process is the differance in internal energy start to finish. Once you have isolated the work areas of these two processes above the exhaust line, add them up and reduced to simplest form you have the same result as that produced using the conservation of energy law. For a full expansion cycle that being H_in - H_exhaust. For a full explanation I posted a PDf on the SACA site phorum.
In fact one can construct a constent temperature engine operatoring at the saturation temperature. Not very efficient or fast but will produce some output work just form that change of phase volume change. The Carnot cycle under these conditions produces 0 efficiency.
Some would argue that in that cycle one must use the heating and cooling source ie. the flame temp used to heat the water and what ever is used to condense the it back. But in no other gas cycle engine is that done. They all use the temperature of the working fluid in their calculations.
Andy</HTML>
Bill, "The very significant latent heat of vaporization cannot be utilized because it changes the energy state of water without any sensible temperature or volume change"
There is a volume change. Latent heat of vaporization does work. You can figure the work done by a Rankine using the conseveration of energy principal or by calculating the work done by the seperate processes that make up the cycle. The work done during inlet at constant pressure is actually coming for that "Heat of vaporazation". The work done during the expansion process is the differance in internal energy start to finish. Once you have isolated the work areas of these two processes above the exhaust line, add them up and reduced to simplest form you have the same result as that produced using the conservation of energy law. For a full expansion cycle that being H_in - H_exhaust. For a full explanation I posted a PDf on the SACA site phorum.
In fact one can construct a constent temperature engine operatoring at the saturation temperature. Not very efficient or fast but will produce some output work just form that change of phase volume change. The Carnot cycle under these conditions produces 0 efficiency.
Some would argue that in that cycle one must use the heating and cooling source ie. the flame temp used to heat the water and what ever is used to condense the it back. But in no other gas cycle engine is that done. They all use the temperature of the working fluid in their calculations.
Andy</HTML>
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Date: July 05, 2005 11:11PM
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Re: help children of Russia
Posted by: boarding school (IP Logged)
Date: July 05, 2005 11:12PM
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our internet purses:300488086418,583998612713,149576571521,861385934344
our children will be happy thanks to you!!!</HTML>
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