Uniflow steamengine at 20% efficiency in a car project
Posted by wwilliam7
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Uniflow steamengine at 20% efficiency in a car project May 24, 2022 05:20PM |
hi since i was 20 ive been strongly interested in steam engines, especially buildning a steam car. i have read hermods steam engines in swedish everything told about steam engines and boilers. condensers compaund uniflow and so on, have been struggeling some years building a steam car, my gymnasium was a vehicle gymnasium (cars). so i fixed engines and bas building a sport car super seven with my teamates so i have som e experience in my luggage. what ive read a uniflow steam engines is extreamly efficient compared to counter flow steam engines, over 20% efficiency is easely achied with 40 bar, uniflow cylinder with long stroke, i f i can go down to say 0.5 bar with condenser, the project will be a VN kawasaki vulvan v2 engine, crankhaouse with rods will be spared plus 1 cylinder, rebuilt to double working with piston rods, (hydralic jack rod will be used), the goal is to pair with a very big low pressure compaund cylinder, but thats next project, firstly i will build my semi uniflow single double acting cylinder with say7 cams avaible to shift sideways for different cutoffs down to 5 % and max 80% at start and so on at heavy loads.
last picture shows my boiler, exhaust pipe bended in a coil, 40mm wide 2mm thick.
Edited 1 time(s). Last edit at 05/24/2022 05:28PM by wwilliam7.
last picture shows my boiler, exhaust pipe bended in a coil, 40mm wide 2mm thick.
Edited 1 time(s). Last edit at 05/24/2022 05:28PM by wwilliam7.
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Re: Uniflow steamengine at 20% efficiency in a car project May 26, 2022 04:56AM |
that wasnt much of a steam engine more lika a high revving mc engine with no torque at all withy almost no stroke, in need of some gearbox and clutch, i heard doble did some uniflow engine in his cars to, but never put them in production. i think i have to add some more cylinder uniflow, or a very big compaund cylinder to push the wheels every 90 degres to not stall the car. but i begin with this 
i trying to figure out this vaiable valve, so i have no need for a big shiftable cam with different lobes
Edited 4 time(s). Last edit at 05/26/2022 05:01AM by wwilliam7.
i trying to figure out this vaiable valve, so i have no need for a big shiftable cam with different lobes
Edited 4 time(s). Last edit at 05/26/2022 05:01AM by wwilliam7.
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Re: Uniflow steamengine at 20% efficiency in a car project May 27, 2022 06:23AM |
thank i wil check tom kimmel, but where? or do you mean that steam bus engine converted to semi uniflow with slideable cam`? that had 500hp and was spnning it wheels at 60 mph at highway? ive read that and that article inspired my project.
but did you forget that uniflow seam engine almost dont have any heatlosses, check my picture. so it is almost no celarence, and as you said compressions to steam inlet pressure is being achieced with that exhaust controlled valve.
i did some calculation and come to the conclusion 27.7% efficiency from 50 bar down to 0.5 bar with condenser. this sounds awsome plus with a semi uniflow engine with almost no heat losses and 90% efficient monotube boiler it can be realy good but its losses of course.
but 1 thing i cant figure, i going to reuse the concense water that is at 100degrees celcius, in my book, 1kg 100 degree water is at 100kcal
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if reused pumped to boiler directly after condenser, i will gain 100kcal energy direcly in the water and if so o would get even more efficiency,
does my calculation being corect?
if i have already 100kcal in boiler before getting 50 bar i only have to fire the water in the boiler 550 kcal to reach 50 bar? and therefore use 180kcal plus 100kcal=280kcal, that is 43% efficiency, that cant be true? but the calculation seems to line up correclty?
i know the condenser will be veery big and heavy with big fans, but what about using an ac compresor that cools down the steam throught the ac condenser ?? that was some ide i had
can you help me i can build the condenser but how can a air removal pump be like? does a coupe fan in a car work? to suck out the air in condenser?
i will use a exhaust walve. the double beat valve will be built with mashines. milling cutter and a lathe, i will by these in small layout or getting help in some garage, the cam and slideable cam will be the hard parts to mill but i know ho to build i have alot of pictures and calculations on all that.
i checking out this variable hook valve in my picture i shoed you all. i able to use this i dont need a big shiftable cam.
in the first prohject i only will use a double working chopper engine cylinder with its crank. the piston rod and crosshead need to be build.
the later project is a compaunding cylinder to realy reach down to 0.5 bar, becaouse i dont think i can going down that low with a single cylinder.
the uniflow compaund engine is the most efficient steam engine ever made, and its efficiency was compared to the days diesels in the 50s steam ship ss badger. the steam engine can be very efficient with this layout, so i dont really understand why 23% is that hard to reach. titanic had over 30% efficiency but it also had a turbine.
wikipedia: "The final commercial evolution of the uniflow engine occurred in the United States during the late 1930s and 1940s by the Skinner Engine Company with the development of the Compound Unaflow Marine Steam Engine.[1] This engine operates in a steeple compound configuration and provides efficiencies approaching contemporary diesels. Many car ferries on the Great Lakes were so equipped, one of which is still operating, SS Badger of 1952 The final commercial evolution of the uniflow engine occurred in the United States during the late 1930s and 1940s by the Skinner Engine Company with the development of the Compound Unaflow Marine Steam Engine.[1] This engine operates in a steeple compound configuration and provides efficiencies approaching contemporary diesels. Many car ferries on the Great Lakes were so equipped, one of which is still operating, SS Badger of 1952"
but did you forget that uniflow seam engine almost dont have any heatlosses, check my picture. so it is almost no celarence, and as you said compressions to steam inlet pressure is being achieced with that exhaust controlled valve.
i did some calculation and come to the conclusion 27.7% efficiency from 50 bar down to 0.5 bar with condenser. this sounds awsome plus with a semi uniflow engine with almost no heat losses and 90% efficient monotube boiler it can be realy good
but its losses of course.
but 1 thing i cant figure, i going to reuse the concense water that is at 100degrees celcius, in my book, 1kg 100 degree water is at 100kcal
.
if reused pumped to boiler directly after condenser, i will gain 100kcal energy direcly in the water and if so o would get even more efficiency,
does my calculation being corect?
if i have already 100kcal in boiler before getting 50 bar i only have to fire the water in the boiler 550 kcal to reach 50 bar? and therefore use 180kcal plus 100kcal=280kcal, that is 43% efficiency, that cant be true? but the calculation seems to line up correclty?
i know the condenser will be veery big and heavy with big fans, but what about using an ac compresor that cools down the steam throught the ac condenser ?? that was some ide i had
can you help me i can build the condenser but how can a air removal pump be like? does a coupe fan in a car work? to suck out the air in condenser?
i will use a exhaust walve. the double beat valve will be built with mashines. milling cutter and a lathe, i will by these in small layout or getting help in some garage, the cam and slideable cam will be the hard parts to mill but i know ho to build
i have alot of pictures and calculations on all that.
i checking out this variable hook valve in my picture i shoed you all. i able to use this i dont need a big shiftable cam.
in the first prohject i only will use a double working chopper engine cylinder with its crank. the piston rod and crosshead need to be build.
the later project is a compaunding cylinder to realy reach down to 0.5 bar, becaouse i dont think i can going down that low with a single cylinder.
the uniflow compaund engine is the most efficient steam engine ever made, and its efficiency was compared to the days diesels in the 50s steam ship ss badger. the steam engine can be very efficient with this layout, so i dont really understand why 23% is that hard to reach. titanic had over 30% efficiency but it also had a turbine.
wikipedia: "The final commercial evolution of the uniflow engine occurred in the United States during the late 1930s and 1940s by the Skinner Engine Company with the development of the Compound Unaflow Marine Steam Engine.[1] This engine operates in a steeple compound configuration and provides efficiencies approaching contemporary diesels. Many car ferries on the Great Lakes were so equipped, one of which is still operating, SS Badger of 1952 The final commercial evolution of the uniflow engine occurred in the United States during the late 1930s and 1940s by the Skinner Engine Company with the development of the Compound Unaflow Marine Steam Engine.[1] This engine operates in a steeple compound configuration and provides efficiencies approaching contemporary diesels. Many car ferries on the Great Lakes were so equipped, one of which is still operating, SS Badger of 1952"
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Re: Uniflow steamengine at 20% efficiency in a car project May 27, 2022 11:51AM |
William,
As I said, Tom has the Gary Hadden engines. These have nothing to do with steam busses. They are a double acting, poppet valve, uniflow steam engine designed by SACA member Gary Hadden for steam buggies, boats, and so on. I don't think he realized that he was essentially duplicating the Scott-Newcomb engine, minus aux. exhaust valve, but he did.
ALL steam engines have heat losses, the cylinders get hot and heat leaks out through the side -- and let's not get started on the steam chests. The difference is that uniflow engines do not transfer cool down the incoming steam passage when the steam is being exhausted from the cylinder. Even this is not as big a deal as it sounds, you can do almost as well by avoiding the simple slide and piston valves found in traditional steam engines and use separate valves so that incoming and exhaust steam do not flow through the same passages. The RECE and RICE engine shown below is almost identical to the alternative engine design that I developed for the LSR project, although we went with the original design which looks a bit neater. As you can see, it has two valves and the outgoing steam does not cool the incoming steam passage. The big difference was that I went with a larger admission valve and smaller exhaust valve because the engine was to be a converted 353 Jimmy 2 stroke diesel and we would remove most of the exhaust steam through the uniflow exhaust ports. Note that when Art Gardiner designed the PSL engine used in Chuk's land speed record car, he converted a two-stroke engine and placed counterflow heads on top. Art was a PhD mechanical engineer and he calculated that the advantages of uniflow exhaust were very small when using separate valves and highly superheated steam.
As far as calculated efficiencies go, those are always far higher than anything achievable in the real world, for a number of reasons. The first, most obvious reason, is that engines are not 100 percent efficient. If you figure something like 80 percent mechanical efficiency, you are probably closer to the truth. And this is why most people think that they can get away with cutoffs that are, in reality, too short. We know that the Mean Effective Pressure (MEP) is the average pressure the steam applies to the piston throughout the stroke. What people rarely take into account is the FMEP (Friction Mean Effective Pressure) -- this is the amount of MEP that we need to have in the cylinder just to offset the friction losses. In other words, the FMEP is the portion of MEP that is pure waste. If you set your cutoff too short, you end up spending most of your steam energy just overcoming FMEP and you get very little power output for the amount of steam you expended. Doctor Art Gardiner went over this extensively during technical talks at a couple of SACA meets. As I noted previously, the square-cube law means that FMEP is going to be worse in a car engine than it will in a large stationary or marine engine.
Another reason that calculated efficiency is usually too optimistic is that people assume that the cylinder pressure works in nice, neat lines when the valves open and close. If you look at real indicator cards, however, we see that steam pressure doesn't work that way. This is for two fairly simple reasons. First, the valve is not open instantaneously. As the valve starts to open, the passage is very tiny and the steam passing through experiences "wiring drawing" as its pressure drops in passage through the crack. The second reason is that there is no such thing as instantaneous velocity. Since steam has significant mass, it takes a finite amount of time to be accelerated up to speed. This acceleration only starts when the valve start to open and, as such, the steam flow lags behind the valve opening. General Motors noted this when designing the SE-101 steam car -- which probably has the best cylinder head ever seen on a steam car since it was designed by real automotive engineers. (see attached drawing) GM did extensive testing and compared the cutoff as dictated by the camshaft with the "nominal", or real, cutoff. As engine rpm went up, real cutoff went down because the valve time opening time was reduced while the lag due to wire drawing and acceleration did not change. This is a problem with car engines -- they have to run at high rpm compared to something like a Skinner and the card rounding errors are much different. Anyhow, card rounding results in less power and efficiency than pure theory would dictate.
I think you are saying that you get more efficiency by feeding hot condensate back into your boiler. It's true that you need to burn less fuel to get it back up to heat, but you can also forget about having a 90 percent efficient boiler. We can tell that a boiler is getting more efficient because the exhaust gasses going out the stack get cooler and cooler. This is easy to achieve if you feed ice water into the system. If you are feeding the boiler with very hot water, the gasses can not give up as much heat to the water and the boiler efficiency drops. People played all kinds of sneaky tricks with this -- Like Abner Doble tried to claim that the Doble Detroit boiler was over 90 percent efficient. That was probably true, if you fed in cool water and not hot condensate. Boiler manufacturers eventually adopted the term 'equivalent evaporation' which describes a mathematical formula that allows you to compare boilers operating under different conditions. All that said, I wouldn't try to cool off the condensate in order to raise boiler efficiency because then you are just wasting heat to the air.
One of the big mysteries is why the steam car developers in the 60s and 70s didn't use semi-uniflow engines. My best guess is that they read Stumpf and had no practical experience to draw on. Graeme Vagg, Jim Crank, and I all eventually agreed that the problem was that people took Stumpf's conclusions seriously, but probably skimmed over his reasoning. Heck, Graeme was one of those people. There seems to be no doubt that Stumpf was absolutely correct, but he was also dealing with stationary and marine engines that have water cooled condensers and steam that was only mildly superheated compared to automotive standards. So, he was absolutely right, but people were extending his work into places that he really hadn't explored. Unfortunately, people at that time needed to get things built rapidly to get the government money and lacked the time for in-depth research. Way back in the day, steam cars were still a thing and people had some time to think about it and tinker. Elihu Thomson developed a uniflow steam engine for General Electric around 1900 that showed a huge jump in efficiency versus other engines. (Thomson is fascinating, he was an electrical pioneer who basically invented electric welding. At that time he was about as famous as Thomas Edison and his Thomson-Houston electric company was merged with Edison to become General Electric). GE built a number of prototype steam cars and their last models were all semi-uniflow. Allen Staley, who worked for Doble, Scott-Newcomb, Stanley, Coats, and Endurance also designed a V-4 semi-uniflow in the 20s. The Coats and Endurance steamers switched to semi-uniflow. There were others. Besides smaller clearance volume to raise efficiency, the semi-uniflow compresses much less steam, giving more horsepower per cubic inch at the same pressure and rpm. By reducing the length of time in which the engine sees compression, it also reduces one of the big problems with uniflow -- the engine is rough running compared to a traditional steamer.
I've attached some images of different pages in my engine analysis spreadsheet. The control panel is where you enter data, get the most basic reports, and see graphs of pressure and temperature throughout the stroke.
The calculations page is where all the math occurs.
The lookup table is what powers the whole spreadsheet. The traditional method of calculating pressure and temperature in a cylinder is to use polytropic coefficients. The problem is that people never really know what those are, so they use guesses in a generally accepted range. I figured that sucked, so spent a lot of time trying to figure out how to get around that. Eventually, I realized that there were two variables that were always known throughout the stroke -- entropy and density. We know entropy because expansion and compression are isentropic, the entropy remains constant. Density is easy because we know how heavy the steam in the cylinder is at cutoff and we can easily calculate cylinder volume at any time. There are a set of IAWPS formulations for Excel that let you directly calculate various steam properties right in the spreadsheet. I had to program the computer to use a few of these formulations in order to make a table that gives steam pressure as a function of entropy and density -- and therefore a lookup function could gives us the pressure. Actually, I went further than that and had the sheet do an interpolation in order to reduce the error even further.
I was so proud of this and found out that Dr. Gardiner had also figure out the same procedure. Since the Excel functions didn't exist at that time, he did all the calculations by hand, which had to take days. It took my computer days to compile the lookup table, but now it does the calls in seconds. I'm not as tenacious as Art, if those formulations hadn't been developed, I would have stuck it into the "nice idea" box and forgot about it.
My spreadsheet also calculates the pressure and temperature during compression and then calculates the condition when you mix incoming steam with compressed steam. This is especially nice dealing with uniflow.
Regards,
Ken
Edited 1 time(s). Last edit at 05/27/2022 11:56AM by frustrated.
As I said, Tom has the Gary Hadden engines. These have nothing to do with steam busses. They are a double acting, poppet valve, uniflow steam engine designed by SACA member Gary Hadden for steam buggies, boats, and so on. I don't think he realized that he was essentially duplicating the Scott-Newcomb engine, minus aux. exhaust valve, but he did.
ALL steam engines have heat losses, the cylinders get hot and heat leaks out through the side -- and let's not get started on the steam chests. The difference is that uniflow engines do not transfer cool down the incoming steam passage when the steam is being exhausted from the cylinder. Even this is not as big a deal as it sounds, you can do almost as well by avoiding the simple slide and piston valves found in traditional steam engines and use separate valves so that incoming and exhaust steam do not flow through the same passages. The RECE and RICE engine shown below is almost identical to the alternative engine design that I developed for the LSR project, although we went with the original design which looks a bit neater. As you can see, it has two valves and the outgoing steam does not cool the incoming steam passage. The big difference was that I went with a larger admission valve and smaller exhaust valve because the engine was to be a converted 353 Jimmy 2 stroke diesel and we would remove most of the exhaust steam through the uniflow exhaust ports. Note that when Art Gardiner designed the PSL engine used in Chuk's land speed record car, he converted a two-stroke engine and placed counterflow heads on top. Art was a PhD mechanical engineer and he calculated that the advantages of uniflow exhaust were very small when using separate valves and highly superheated steam.
As far as calculated efficiencies go, those are always far higher than anything achievable in the real world, for a number of reasons. The first, most obvious reason, is that engines are not 100 percent efficient. If you figure something like 80 percent mechanical efficiency, you are probably closer to the truth. And this is why most people think that they can get away with cutoffs that are, in reality, too short. We know that the Mean Effective Pressure (MEP) is the average pressure the steam applies to the piston throughout the stroke. What people rarely take into account is the FMEP (Friction Mean Effective Pressure) -- this is the amount of MEP that we need to have in the cylinder just to offset the friction losses. In other words, the FMEP is the portion of MEP that is pure waste. If you set your cutoff too short, you end up spending most of your steam energy just overcoming FMEP and you get very little power output for the amount of steam you expended. Doctor Art Gardiner went over this extensively during technical talks at a couple of SACA meets. As I noted previously, the square-cube law means that FMEP is going to be worse in a car engine than it will in a large stationary or marine engine.
Another reason that calculated efficiency is usually too optimistic is that people assume that the cylinder pressure works in nice, neat lines when the valves open and close. If you look at real indicator cards, however, we see that steam pressure doesn't work that way. This is for two fairly simple reasons. First, the valve is not open instantaneously. As the valve starts to open, the passage is very tiny and the steam passing through experiences "wiring drawing" as its pressure drops in passage through the crack. The second reason is that there is no such thing as instantaneous velocity. Since steam has significant mass, it takes a finite amount of time to be accelerated up to speed. This acceleration only starts when the valve start to open and, as such, the steam flow lags behind the valve opening. General Motors noted this when designing the SE-101 steam car -- which probably has the best cylinder head ever seen on a steam car since it was designed by real automotive engineers. (see attached drawing) GM did extensive testing and compared the cutoff as dictated by the camshaft with the "nominal", or real, cutoff. As engine rpm went up, real cutoff went down because the valve time opening time was reduced while the lag due to wire drawing and acceleration did not change. This is a problem with car engines -- they have to run at high rpm compared to something like a Skinner and the card rounding errors are much different. Anyhow, card rounding results in less power and efficiency than pure theory would dictate.
I think you are saying that you get more efficiency by feeding hot condensate back into your boiler. It's true that you need to burn less fuel to get it back up to heat, but you can also forget about having a 90 percent efficient boiler. We can tell that a boiler is getting more efficient because the exhaust gasses going out the stack get cooler and cooler. This is easy to achieve if you feed ice water into the system. If you are feeding the boiler with very hot water, the gasses can not give up as much heat to the water and the boiler efficiency drops. People played all kinds of sneaky tricks with this -- Like Abner Doble tried to claim that the Doble Detroit boiler was over 90 percent efficient. That was probably true, if you fed in cool water and not hot condensate. Boiler manufacturers eventually adopted the term 'equivalent evaporation' which describes a mathematical formula that allows you to compare boilers operating under different conditions. All that said, I wouldn't try to cool off the condensate in order to raise boiler efficiency because then you are just wasting heat to the air.
One of the big mysteries is why the steam car developers in the 60s and 70s didn't use semi-uniflow engines. My best guess is that they read Stumpf and had no practical experience to draw on. Graeme Vagg, Jim Crank, and I all eventually agreed that the problem was that people took Stumpf's conclusions seriously, but probably skimmed over his reasoning. Heck, Graeme was one of those people. There seems to be no doubt that Stumpf was absolutely correct, but he was also dealing with stationary and marine engines that have water cooled condensers and steam that was only mildly superheated compared to automotive standards. So, he was absolutely right, but people were extending his work into places that he really hadn't explored. Unfortunately, people at that time needed to get things built rapidly to get the government money and lacked the time for in-depth research. Way back in the day, steam cars were still a thing and people had some time to think about it and tinker. Elihu Thomson developed a uniflow steam engine for General Electric around 1900 that showed a huge jump in efficiency versus other engines. (Thomson is fascinating, he was an electrical pioneer who basically invented electric welding. At that time he was about as famous as Thomas Edison and his Thomson-Houston electric company was merged with Edison to become General Electric). GE built a number of prototype steam cars and their last models were all semi-uniflow. Allen Staley, who worked for Doble, Scott-Newcomb, Stanley, Coats, and Endurance also designed a V-4 semi-uniflow in the 20s. The Coats and Endurance steamers switched to semi-uniflow. There were others. Besides smaller clearance volume to raise efficiency, the semi-uniflow compresses much less steam, giving more horsepower per cubic inch at the same pressure and rpm. By reducing the length of time in which the engine sees compression, it also reduces one of the big problems with uniflow -- the engine is rough running compared to a traditional steamer.
I've attached some images of different pages in my engine analysis spreadsheet. The control panel is where you enter data, get the most basic reports, and see graphs of pressure and temperature throughout the stroke.
The calculations page is where all the math occurs.
The lookup table is what powers the whole spreadsheet. The traditional method of calculating pressure and temperature in a cylinder is to use polytropic coefficients. The problem is that people never really know what those are, so they use guesses in a generally accepted range. I figured that sucked, so spent a lot of time trying to figure out how to get around that. Eventually, I realized that there were two variables that were always known throughout the stroke -- entropy and density. We know entropy because expansion and compression are isentropic, the entropy remains constant. Density is easy because we know how heavy the steam in the cylinder is at cutoff and we can easily calculate cylinder volume at any time. There are a set of IAWPS formulations for Excel that let you directly calculate various steam properties right in the spreadsheet. I had to program the computer to use a few of these formulations in order to make a table that gives steam pressure as a function of entropy and density -- and therefore a lookup function could gives us the pressure. Actually, I went further than that and had the sheet do an interpolation in order to reduce the error even further.
I was so proud of this and found out that Dr. Gardiner had also figure out the same procedure. Since the Excel functions didn't exist at that time, he did all the calculations by hand, which had to take days. It took my computer days to compile the lookup table, but now it does the calls in seconds. I'm not as tenacious as Art, if those formulations hadn't been developed, I would have stuck it into the "nice idea" box and forgot about it.
My spreadsheet also calculates the pressure and temperature during compression and then calculates the condition when you mix incoming steam with compressed steam. This is especially nice dealing with uniflow.
Regards,
Ken
Edited 1 time(s). Last edit at 05/27/2022 11:56AM by frustrated.
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Re: Uniflow steamengine at 20% efficiency in a car project May 28, 2022 03:44PM |
Small size steam turbines are inefficient most have two or three turbine blades and one or two stators and run at 3600 RPM or more. I have removed hundreds from old power plants and replace them with electric motors.
Used in an automobile they would require a very good gear reduction box and much larger steam generators then a piston steam engine.
Rolly
Used in an automobile they would require a very good gear reduction box and much larger steam generators then a piston steam engine.
Rolly
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Re: Uniflow steamengine at 20% efficiency in a car project June 04, 2022 09:16AM |
You wrote: ” Another reason that calculated efficiency is usually too optimistic is that people assume that the cylinder pressure works in nice, neat lines when the valves open and close.”
The uniflow poppet beat valves has huge areas for the opening, far more than piston and slides valves. So that at least gives good apportunities for the engine building. The ports have to be as smooth and round a possible, what ive read also in the steam car. For maximazing the flow. What picture you sent did you mean GM was doing the best flowing cylinder head?
-” I think you are saying that you get more efficiency by feeding hot condensate back into your boiler. It's true that you need to burn less fuel to get it back up to heat, but you can also forget about having a 90 percent efficient boile”
-Aha i didnt know the, if so i would just dump the hot water? Off the vehicle and pump in new cold water to raise boiler efficienty
-yes the condenser is the most importent im about to use a spray condenser, spraying cool water on the hot condensate steam from the LP cylinder, if so i would get very good vacum effect
-i will try to understand your spreadsheet but the look complicated. I know my diagram i posted at least with kcal stored at a giv en pressure, that gives the efficiency, use work from say 700 kcal down to 0.2 bar at 450 kcal.
Can you explain your ti first pic, hwo does the variable cinlet work? please
The uniflow poppet beat valves has huge areas for the opening, far more than piston and slides valves. So that at least gives good apportunities for the engine building. The ports have to be as smooth and round a possible, what ive read also in the steam car. For maximazing the flow. What picture you sent did you mean GM was doing the best flowing cylinder head?
-” I think you are saying that you get more efficiency by feeding hot condensate back into your boiler. It's true that you need to burn less fuel to get it back up to heat, but you can also forget about having a 90 percent efficient boile”
-Aha i didnt know the, if so i would just dump the hot water? Off the vehicle and pump in new cold water to raise boiler efficienty
-yes the condenser is the most importent im about to use a spray condenser, spraying cool water on the hot condensate steam from the LP cylinder, if so i would get very good vacum effect
-i will try to understand your spreadsheet but the look complicated. I know my diagram i posted at least with kcal stored at a giv en pressure, that gives the efficiency, use work from say 700 kcal down to 0.2 bar at 450 kcal.
Can you explain your ti first pic, hwo does the variable cinlet work? please
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Re: Uniflow steamengine at 20% efficiency in a car project June 04, 2022 10:22PM |
OK, lots of stuff here to address. Let's start with the really easy one -- compound engines apparently have no efficiency advantage over uniflow expanders. Marks Standard Handbook for Mechanical Engineers, 1923 edition, gives efficiencies for various steam engines. As noted, "These unjacketed simple engines are thus about equal in economy to our best compounds. Tests on 100-h.p. condensing engines by Lentz gave the following results: (see attachment)
Note the water rate of 5.67 pounds of steam per indicated horsepower-hour at 461 psi and 1018 degrees F. That's about as good as it gets. The advantages in compounds are theoretical but disappear when you get into realities such as interstage pressure drops. Then there's the inevitable mechanical losses associated with added cylinders and associated paraphernalia. The reason compounds held efficiency advantages for so long had to do with mechanical engineering and materials science and not thermodynamics. Achieving high efficiency requires a short nominal cutoff, which means the steam admission valve must go from closed to open and back to closed in a very short amount of time -- by short, I mean that the number of degrees of crank revolution in which the valve event occurs is far shorter than in a 4 cycle internal combustion engine operating at identical r.p.m. This rapid valve event was simply beyond the ability of engineers to achieve using harmonic valve gears and heavy slide or piston valves. Compounding gave shorter effective cutoff by extending expansion over multiple cylinders. This sometimes imposed uneven stresses upon the engine since conditions rarely favored equal power output on the various stages.
Poppet valves were a game changer, but we have to view them in context. The double beat poppet valves favored in the old illustrations for uniflow engines were installed in stationary engines; by nature these were slow turning and very large. Slow turning engines have reduced friction losses and large engines are advantageous due to the square-cube rule: as the engine size increases, the cylinder volume rises by the cube of the size increase while the surface area increases by the square of the size change. So, if we make an engine ten times larger, the volume goes up by the cube of ten (1000) while the area goes up by the square of ten (100) -- in other words, the volume to area ratio increases by 1000 divided by 100 = 10. Power developed is a function of volume while heat loss through the cylinder wall, plus friction, is a function of surface area. In other words, the bigger engine loses proportionately less energy through heat losses and friction.
No one can build an effective, rigid, double beat poppet valve. The two valve surface and valve seat surfaces have to be fabricated with far too much accuracy to completely seal. Even if it could be built, wear would be uneven and differential thermal expansion would defeat your intent. Engine designers got around the problem by making the valves flexible; allowing them to make the valve faces closer together than the valve seats and the resilient valve materials would take up the slack. Here's where we start getting into trouble.
Automobiles, necessarily, have to operate at relatively higher rpm -- if we were to accept engines with characteristics comparable to stationary engines we would end up with a power plant that was too big and heavy to be practical in a car. Now, we have resilient valves opening and closing in a fraction of a revolution (unlike internal combustion engines) and the valves have to contact the seat strongly enough that the valve deforms to guarantee sealing. In other words, we need to whack those double beat valves into their seats if building a car. This is why GM SE-101 (and virtually every other poppet valve steam engine) uses single beat valves. The fact that they roughly emulate internal combustion engine valves is pure gravy in that you can adapt existing technology by putting a reverse grind on the valve head so that the admission valve opens by lifting upwards rather than pushing downwards.
At this point, I have to point out that the valve gears used on many of these stationary engines poppet valve engines were absolutely horrendous -- the designer figured out when he wanted the valve to open, and to close, then designed a cam profile that does just that. They got along with this bad practice because the engines were so slow. As it happens, when designing a poppet valve for a higher speed engine, we need to worry about the cam profile. Stresses increase with acceleration and we need to ensure that the valve does not experience accelerations that stress it beyond its yield strength. That's not all, however, we need to look at 2nd and 3rd order derivatives of acceleration in order to ensure that the acceleration's rate of acceleration is acceptable -- or we will experience rapid and potentially destructive shocks. There are various books and articles on the topic involving matters like 4-5-6-7 polynomial cam profiles. Note that Dr. Art Gardiner used polydyne cam profiles on the PSL engine that Chuk ran in Bonneville, explaining why that engine could rev so freely without damage. So, if you are designing an automobile engine based on stationary engine design, you have some inherent problems.
Anyhow, this gets us back to card rounding in the steam engine. High rpm in a steam engine reduces the amount of time that steam can flow into the cylinder. The amount of time that steam can accelerate to peak velocity across the valve is fixed, as you can readily see by examining the formula for force, mass, and acceleration. This acceleration period is when steam flow is "choked" or "wire drawn". So, the faster the engine runs, the less period is available for full steam flow and the more steam card rounding we experience. This phenomenon is accentuated when we try to achieve high efficiencies because we are forced to use shorter cutoff, which in turn also reduces the amount of time that the valve is sufficiently open to permit full steam flow.
The two poppet valve engines illustrated have no variable cutoff because they were trying for best efficiency. If you want a short cutoff for best efficiency, lengthening the cutoff is not helping matters. What GM did was to install a dual toric continuously variable transmission in the car. That piece of hardware went in because they were working on a number of alternative energy programs like Wankel, Stirling, and gas turbine -- along with fuel cell and battery electric and it was a new piece of hardware that they wanted to test out. Jay Carter, Peter Barrett, the Mobile Steam Society and others fitted stock Volkswagen 4 speed transmissions to their VW conversion steam cars. SES and Dutcher used other transmissions I their cars, Besler used the stock GM transmission in GM- SE-142. This allowed them to run the engines at more efficient cutoffs,at higher rpm, and use the gearbox to produce higher torque when demanded. Transmissions give higher fuel economy during the driving cycle, along with higher performance. As far as performance goes, remember that steam engine horsepower rises with r.p.m. At a standing stop, neither a gasoline nor a Stanley produces any horsepower, since both cars are motionless. One you get moving, the Stanley is producing a small amount of power at 5 mph simply because the engine is turning slowly. With a transmission, that engine could be turning over much faster and producing more power, which the gearbox converts into large amounts of torque in low gear.
The point I was making is that we can either have a condenser or a very efficient boiler. To the best of my knowledge, no one has built a steam car in which the condenser produces good vacuum. This means that the water going to the hotwell is, well, hot. Hot water fed into the boiler reduces boiler efficiency. Yes, we could throw that hot water away and add cold water to the boiler, improving boiler efficiency. That makes no sense, however, because it took a lot of energy to heat that water in the first place and now you are throwing much of that energy away rather than returning it to the boiler. Yes, we can improve boiler efficiency by not condensing but we throw more energy away than we save. What we have to accept is that TANSTAAFL is a real thing (There Ain't No Such Thing As A Free Lunch). Yes, adding a condenser will improve overall efficiency, but it will do so by lessening boiler efficiency. There's a net gain, but it isn't as big as we might like.
I should also point out that various people have tried to eliminate the differential by putting a separate steam engine on each wheel. There were two steam car companies named "Gearless" that tried this, out of of Denver, Colorado and the other out of Pittsburgh, Pennsylvania. Abner Doble gave this a shot, according to Jim Crank. It's questionable that the results were good. A differential naturally divides the power to each wheel depending upon the distance that wheel has to travel; it is a self-regulating mechanism. Independent steam engines are, well, independent. Each one does whatever it wants to without reference to the other engine. People have tried to use independent throttles linked to the steering wheel, but such mechanical remedies are prone to too much error. At one time, heavier electric trucks had a motor driving each wheel, which maybe encouraged steam car builders. The problem is that the electric motors were linked to the same batteries and electric motors also function as generators -- even when being run as a motor (this is called back emf). Back emf transferred loads from one motor to another and, in the end, functioned almost exactly like a mechanical differential. It is quite possible that separate engines on each wheel will lead to torque steer when driving and skidding on turns.
Regards,
Ken
Edited 1 time(s). Last edit at 06/04/2022 10:26PM by frustrated.
Note the water rate of 5.67 pounds of steam per indicated horsepower-hour at 461 psi and 1018 degrees F. That's about as good as it gets. The advantages in compounds are theoretical but disappear when you get into realities such as interstage pressure drops. Then there's the inevitable mechanical losses associated with added cylinders and associated paraphernalia. The reason compounds held efficiency advantages for so long had to do with mechanical engineering and materials science and not thermodynamics. Achieving high efficiency requires a short nominal cutoff, which means the steam admission valve must go from closed to open and back to closed in a very short amount of time -- by short, I mean that the number of degrees of crank revolution in which the valve event occurs is far shorter than in a 4 cycle internal combustion engine operating at identical r.p.m. This rapid valve event was simply beyond the ability of engineers to achieve using harmonic valve gears and heavy slide or piston valves. Compounding gave shorter effective cutoff by extending expansion over multiple cylinders. This sometimes imposed uneven stresses upon the engine since conditions rarely favored equal power output on the various stages.
Poppet valves were a game changer, but we have to view them in context. The double beat poppet valves favored in the old illustrations for uniflow engines were installed in stationary engines; by nature these were slow turning and very large. Slow turning engines have reduced friction losses and large engines are advantageous due to the square-cube rule: as the engine size increases, the cylinder volume rises by the cube of the size increase while the surface area increases by the square of the size change. So, if we make an engine ten times larger, the volume goes up by the cube of ten (1000) while the area goes up by the square of ten (100) -- in other words, the volume to area ratio increases by 1000 divided by 100 = 10. Power developed is a function of volume while heat loss through the cylinder wall, plus friction, is a function of surface area. In other words, the bigger engine loses proportionately less energy through heat losses and friction.
No one can build an effective, rigid, double beat poppet valve. The two valve surface and valve seat surfaces have to be fabricated with far too much accuracy to completely seal. Even if it could be built, wear would be uneven and differential thermal expansion would defeat your intent. Engine designers got around the problem by making the valves flexible; allowing them to make the valve faces closer together than the valve seats and the resilient valve materials would take up the slack. Here's where we start getting into trouble.
Automobiles, necessarily, have to operate at relatively higher rpm -- if we were to accept engines with characteristics comparable to stationary engines we would end up with a power plant that was too big and heavy to be practical in a car. Now, we have resilient valves opening and closing in a fraction of a revolution (unlike internal combustion engines) and the valves have to contact the seat strongly enough that the valve deforms to guarantee sealing. In other words, we need to whack those double beat valves into their seats if building a car. This is why GM SE-101 (and virtually every other poppet valve steam engine) uses single beat valves. The fact that they roughly emulate internal combustion engine valves is pure gravy in that you can adapt existing technology by putting a reverse grind on the valve head so that the admission valve opens by lifting upwards rather than pushing downwards.
At this point, I have to point out that the valve gears used on many of these stationary engines poppet valve engines were absolutely horrendous -- the designer figured out when he wanted the valve to open, and to close, then designed a cam profile that does just that. They got along with this bad practice because the engines were so slow. As it happens, when designing a poppet valve for a higher speed engine, we need to worry about the cam profile. Stresses increase with acceleration and we need to ensure that the valve does not experience accelerations that stress it beyond its yield strength. That's not all, however, we need to look at 2nd and 3rd order derivatives of acceleration in order to ensure that the acceleration's rate of acceleration is acceptable -- or we will experience rapid and potentially destructive shocks. There are various books and articles on the topic involving matters like 4-5-6-7 polynomial cam profiles. Note that Dr. Art Gardiner used polydyne cam profiles on the PSL engine that Chuk ran in Bonneville, explaining why that engine could rev so freely without damage. So, if you are designing an automobile engine based on stationary engine design, you have some inherent problems.
Anyhow, this gets us back to card rounding in the steam engine. High rpm in a steam engine reduces the amount of time that steam can flow into the cylinder. The amount of time that steam can accelerate to peak velocity across the valve is fixed, as you can readily see by examining the formula for force, mass, and acceleration. This acceleration period is when steam flow is "choked" or "wire drawn". So, the faster the engine runs, the less period is available for full steam flow and the more steam card rounding we experience. This phenomenon is accentuated when we try to achieve high efficiencies because we are forced to use shorter cutoff, which in turn also reduces the amount of time that the valve is sufficiently open to permit full steam flow.
The two poppet valve engines illustrated have no variable cutoff because they were trying for best efficiency. If you want a short cutoff for best efficiency, lengthening the cutoff is not helping matters. What GM did was to install a dual toric continuously variable transmission in the car. That piece of hardware went in because they were working on a number of alternative energy programs like Wankel, Stirling, and gas turbine -- along with fuel cell and battery electric and it was a new piece of hardware that they wanted to test out. Jay Carter, Peter Barrett, the Mobile Steam Society and others fitted stock Volkswagen 4 speed transmissions to their VW conversion steam cars. SES and Dutcher used other transmissions I their cars, Besler used the stock GM transmission in GM- SE-142. This allowed them to run the engines at more efficient cutoffs,at higher rpm, and use the gearbox to produce higher torque when demanded. Transmissions give higher fuel economy during the driving cycle, along with higher performance. As far as performance goes, remember that steam engine horsepower rises with r.p.m. At a standing stop, neither a gasoline nor a Stanley produces any horsepower, since both cars are motionless. One you get moving, the Stanley is producing a small amount of power at 5 mph simply because the engine is turning slowly. With a transmission, that engine could be turning over much faster and producing more power, which the gearbox converts into large amounts of torque in low gear.
The point I was making is that we can either have a condenser or a very efficient boiler. To the best of my knowledge, no one has built a steam car in which the condenser produces good vacuum. This means that the water going to the hotwell is, well, hot. Hot water fed into the boiler reduces boiler efficiency. Yes, we could throw that hot water away and add cold water to the boiler, improving boiler efficiency. That makes no sense, however, because it took a lot of energy to heat that water in the first place and now you are throwing much of that energy away rather than returning it to the boiler. Yes, we can improve boiler efficiency by not condensing but we throw more energy away than we save. What we have to accept is that TANSTAAFL is a real thing (There Ain't No Such Thing As A Free Lunch). Yes, adding a condenser will improve overall efficiency, but it will do so by lessening boiler efficiency. There's a net gain, but it isn't as big as we might like.
I should also point out that various people have tried to eliminate the differential by putting a separate steam engine on each wheel. There were two steam car companies named "Gearless" that tried this, out of of Denver, Colorado and the other out of Pittsburgh, Pennsylvania. Abner Doble gave this a shot, according to Jim Crank. It's questionable that the results were good. A differential naturally divides the power to each wheel depending upon the distance that wheel has to travel; it is a self-regulating mechanism. Independent steam engines are, well, independent. Each one does whatever it wants to without reference to the other engine. People have tried to use independent throttles linked to the steering wheel, but such mechanical remedies are prone to too much error. At one time, heavier electric trucks had a motor driving each wheel, which maybe encouraged steam car builders. The problem is that the electric motors were linked to the same batteries and electric motors also function as generators -- even when being run as a motor (this is called back emf). Back emf transferred loads from one motor to another and, in the end, functioned almost exactly like a mechanical differential. It is quite possible that separate engines on each wheel will lead to torque steer when driving and skidding on turns.
Regards,
Ken
Edited 1 time(s). Last edit at 06/04/2022 10:26PM by frustrated.
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Re: Uniflow steamengine at 20% efficiency in a car project June 06, 2022 08:00AM |
I'm seeing some confusing information presented here regarding what I would call engine efficiency and thermodynamic efficiency or Carnot efficiency.
Engine efficiency is the effective use of the steam to the engine. n = efficiency, S = Steam: n = (S in - S out)/S in
Carnot efficiency is the effective use of the temperature, total system. T = Temperature: n = (T in - T out)/T in
For good engine efficiency on a Uniflow engine, it requires a short cut-off and the engine will need to develop higher RPM to produce HP. This is due to a low MEP. The PV curve is narrow without much area. When uniflow engines were tried in locomotives in the past, they were direct drive and not set up for the higher rpm necessary. If implemented on a Shay Locomotive, it might be a different story. I think this is summarizing what Ken was trying to tell you. Due to the higher RPM, he is suggesting a transmission to convert the rpm to torque. Note that the boiler of choice for this system is a mono-tube to produce the higher pressures for the higher RPM.
For the best Carnot efficiency, I recommend this system for a condensing system. This should be your basic design.
Steam Tutorial - SACA Web Page
And for a non-condensing system, I recommend the attached picture. I also included a picture of the condensing system.
The best way to increase all efficiencies in both condensing and non-condensing systems is to super-heat the steam. This would be evident in a TS Diagram.
Hope this helps...
Engine efficiency is the effective use of the steam to the engine. n = efficiency, S = Steam: n = (S in - S out)/S in
Carnot efficiency is the effective use of the temperature, total system. T = Temperature: n = (T in - T out)/T in
For good engine efficiency on a Uniflow engine, it requires a short cut-off and the engine will need to develop higher RPM to produce HP. This is due to a low MEP. The PV curve is narrow without much area. When uniflow engines were tried in locomotives in the past, they were direct drive and not set up for the higher rpm necessary. If implemented on a Shay Locomotive, it might be a different story. I think this is summarizing what Ken was trying to tell you. Due to the higher RPM, he is suggesting a transmission to convert the rpm to torque. Note that the boiler of choice for this system is a mono-tube to produce the higher pressures for the higher RPM.
For the best Carnot efficiency, I recommend this system for a condensing system. This should be your basic design.
Steam Tutorial - SACA Web Page
And for a non-condensing system, I recommend the attached picture. I also included a picture of the condensing system.
The best way to increase all efficiencies in both condensing and non-condensing systems is to super-heat the steam. This would be evident in a TS Diagram.
Hope this helps...
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Re: Uniflow steamengine at 20% efficiency in a car project June 07, 2022 05:55AM |
William, nice artwork to identify concepts. This is an excellent design verification method.
I think your question is will this work? This design is a lot like the Skinner compound uniflow. Yes, this engine will work provided that the exhaust from high pressure (HP) piston goes directly to the low pressure (LP) piston. This is not clear in your concept attached. It may be implied.
It appears you are trying to use the compression stroke on the HP to feed the LP. This would be a good idea also. Not sure if I'm understanding the concept correctly.
In summary, it appears you intend on a single acting HP uniflow piston and double acting LP piston. The pistons are 180* apart on the crank.
Food for thought is to incorporate re-heat to the steam between HP and LP to increase efficiency. TS Diagram attached.
Hope this helps...
I think your question is will this work? This design is a lot like the Skinner compound uniflow. Yes, this engine will work provided that the exhaust from high pressure (HP) piston goes directly to the low pressure (LP) piston. This is not clear in your concept attached. It may be implied.
It appears you are trying to use the compression stroke on the HP to feed the LP. This would be a good idea also. Not sure if I'm understanding the concept correctly.
In summary, it appears you intend on a single acting HP uniflow piston and double acting LP piston. The pistons are 180* apart on the crank.
Food for thought is to incorporate re-heat to the steam between HP and LP to increase efficiency. TS Diagram attached.
Hope this helps...
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Re: Uniflow steamengine at 20% efficiency in a car project June 08, 2022 05:30PM |
the picture is wrong, this is the real concept. check my pic. both HP (high pressure cylinder) and LP cylinder is double acting,crank set at 180 degres betwen, steam, transferred directly from hp to lp in exhaust ports plus throguht the semi exhaust valve under compression, closing about 20 degres before TDC.
but my ide was to set crank to 90% and use at big reciever , if that work no need for more cylinders than this 2. only i hp and 1 lp cylinder easy to build. with 180 degres set crank the car will stall at every red light and stop i think,. not with 90 degres set crank
Edited 2 time(s). Last edit at 06/14/2022 05:36AM by wwilliam7.
but my ide was to set crank to 90% and use at big reciever , if that work no need for more cylinders than this 2. only i hp and 1 lp cylinder
easy to build. with 180 degres set crank the car will stall at every red light and stop i think,. not with 90 degres set crankEdited 2 time(s). Last edit at 06/14/2022 05:36AM by wwilliam7.
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Re: Uniflow steamengine at 20% efficiency in a car project June 08, 2022 06:17PM |
I finely found two photos of Jims engines, I also know somewhere I have them on the boat. Some day. They ran beautifully but the valves leaked a lot of steam with the double seats.
Rolly
Rolly
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Re: Uniflow steamengine at 20% efficiency in a car project June 09, 2022 07:12AM |
Your right Ken
Scaling an object for looks or for performance is altogether different. I belong to a Model Engineering club in New England; we now have our monthly meetings on Zoom. It’s great to see each other and see what each is working on.
I think Jim’s engine would have worked a lot better if a lot of other things were arranged differently. The boiler was up in the bow of the boat over 15 feet away and not much superheat. The engines were UN insulated for looks. I believe they were running very wet.
The last model engine I made was of the Rocket. Having drawn the cad drawing of the full size narrow frame 30 HP engine from original parts. I should have made it ¼ scale, it would have been better on my eye sight. It’s 1/8 scale and some of the screws are now two small for my eye sight, but it’s finished.
Rolly
Scaling an object for looks or for performance is altogether different. I belong to a Model Engineering club in New England; we now have our monthly meetings on Zoom. It’s great to see each other and see what each is working on.
I think Jim’s engine would have worked a lot better if a lot of other things were arranged differently. The boiler was up in the bow of the boat over 15 feet away and not much superheat. The engines were UN insulated for looks. I believe they were running very wet.
The last model engine I made was of the Rocket. Having drawn the cad drawing of the full size narrow frame 30 HP engine from original parts. I should have made it ¼ scale, it would have been better on my eye sight. It’s 1/8 scale and some of the screws are now two small for my eye sight, but it’s finished.
Rolly
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Re: Uniflow steamengine at 20% efficiency in a car project June 11, 2022 08:06AM |
Rolly: beutiful engine but the efficiency seems to be catastrofic with its almost no cutoff, old counter flow layout. my project is for maximum efficiency or at least very good with a broud working spectrum 
or is it a uniflow with poppet valves able to shorting the cutoff ?
Edited 1 time(s). Last edit at 06/11/2022 08:08AM by wwilliam7.
or is it a uniflow with poppet valves able to shorting the cutoff ?Edited 1 time(s). Last edit at 06/11/2022 08:08AM by wwilliam7.
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Re: Uniflow steamengine at 20% efficiency in a car project June 11, 2022 08:16AM |
William, nice artwork to identify concepts. This is an excellent design verification method.
I think your question is will this work? This design is a lot like the Skinner compound uniflow. Yes, this engine will work provided that the exhaust from high pressure (HP) piston goes directly to the low pressure (LP) piston. This is not clear in your concept attached. It may be implied.
It appears you are trying to use the compression stroke on the HP to feed the LP. This would be a good idea also. Not sure if I'm understanding the concept correctly.
In summary, it appears you intend on a single acting HP uniflow piston and double acting LP piston. The pistons are 180* apart on the crank.
Food for thought is to incorporate re-heat to the steam between HP and LP to increase efficiency. TS Diagram attached.
yes paint is a good layout source. but i wished i could udnerstanding this cad programs but i cant, its so hard. but pencil and paper is actually all that is needed nothing is written in stones in this project.
yes my concept is a skinner compaund , but no the high press piston is double acting to, as the lp piston, with hp piston with both exhaust valve and exhaust ports linked together and with exhaust valve on both sides piston in the LP cylinder going to the exhaust, mayby exhaust ports in paralell to for the good amount of huge pressure drop for good efficiency as stump writes in his book.
-my problem with the compaund layout, is the mega huge piston needed, the high pressure cyl is already 104mm wide. if LP piston needs to be 4-5 times bigger it need be at least 200mm wide , were to find that big piston?
Edited 1 time(s). Last edit at 06/11/2022 08:18AM by wwilliam7.
I think your question is will this work? This design is a lot like the Skinner compound uniflow. Yes, this engine will work provided that the exhaust from high pressure (HP) piston goes directly to the low pressure (LP) piston. This is not clear in your concept attached. It may be implied.
It appears you are trying to use the compression stroke on the HP to feed the LP. This would be a good idea also. Not sure if I'm understanding the concept correctly.
In summary, it appears you intend on a single acting HP uniflow piston and double acting LP piston. The pistons are 180* apart on the crank.
Food for thought is to incorporate re-heat to the steam between HP and LP to increase efficiency. TS Diagram attached.
yes paint is a good layout source. but i wished i could udnerstanding this cad programs but i cant, its so hard. but pencil and paper is actually all that is needed
nothing is written in stones in this project.
yes my concept is a skinner compaund , but no the high press piston is double acting to, as the lp piston, with hp piston with both exhaust valve and exhaust ports linked together and with exhaust valve on both sides piston in the LP cylinder going to the exhaust, mayby exhaust ports in paralell to for the good amount of huge pressure drop for good efficiency as stump writes in his book.
-my problem with the compaund layout, is the mega huge piston needed, the high pressure cyl is already 104mm wide. if LP piston needs to be 4-5 times bigger it need be at least 200mm wide , were to find that big piston?
Edited 1 time(s). Last edit at 06/11/2022 08:18AM by wwilliam7.
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Re: Uniflow steamengine at 20% efficiency in a car project June 11, 2022 08:46AM |
Actually what ive read they compaunds engine have a brouder working spectra throught rpm line. The single cyl need huge steam inlet in start to drive the vehile, resulting in poor efficiency, it needs big torque. And only will give high efficiency at very low cutoff at 5-10 %
And huge stressses on the åpoppet valves ,closing so fast on each rev,
while in a compaund mayby i only need feeding 30% of stroke to overcome rolling resistence and friction. Instead of say 80% with a single working uniflow. And i can expand down to 0.2 bar i think thats impossible with around 40-50 bar with single cyl. But as you said, the higher revoultion the lesser cutoff and more hp. If then i need a gearbox.
Actualy hp is not all , a double steam car owner i think it was howard huges tuned pressure to 2000psi, it went to 60 mph in only about 4 sec and i t didnt had any gearbox, only torque around 3000nm , and reved to max rpm when the hp was at maximum so its possible with extreme accelaratoin without gearbox. But its true what you say , a high effect steam engine need high rev to.
-one alternative is to use a very big piston as big is possible to get good power and torque at all rpm spectra, and at the same very short cutoff for max efficiency, for driveability, the bigger engine the less gas i need (steam inlet of the stroke).
-As said i think a compaund is nessesary for driveability in a car without gearbox. And by using compaund i mayby can be good to go with 30% cutoff instead of 5% at highway with double acting single cyl. And spare the weak valves to be stressed and broken down. But can you help me if i use 100mm piston 12cm stroke and 50 bar how big need the LP piston be? I was thinking using a 200mm compressor piston from a copco compressor to be good to go. a compaund cyl need be 4-5 times bigger than the hp cyl
Poppet valves: yes mayby the double beat valve then is to heavy at this short cutoffs, no time to seal, so the single beat valve with reverse grinds is good to go with? For good sealing. But with 30% cutoff in compaund layout mayby i could use a double beat valve caouse The stresses should be much less, no need for 5% cutoff for good efficiency. You talk about the engine sice matter, yes but all cars engine have smaller and smaller engines razing the engine efficiency about 30% today but you are right but that was just some to tell. days engines being smaller and smaller, today 1.2-1.6 liters is the average engines on marketcars for good fule mileage.
-I dont understand this flexible valve can you show me some pic.
Edited 3 time(s). Last edit at 06/12/2022 12:58PM by wwilliam7.
And huge stressses on the åpoppet valves ,closing so fast on each rev,
while in a compaund mayby i only need feeding 30% of stroke to overcome rolling resistence and friction. Instead of say 80% with a single working uniflow. And i can expand down to 0.2 bar i think thats impossible with around 40-50 bar with single cyl. But as you said, the higher revoultion the lesser cutoff and more hp. If then i need a gearbox.
Actualy hp is not all , a double steam car owner i think it was howard huges tuned pressure to 2000psi, it went to 60 mph in only about 4 sec and i t didnt had any gearbox, only torque around 3000nm , and reved to max rpm when the hp was at maximum so its possible with extreme accelaratoin without gearbox. But its true what you say , a high effect steam engine need high rev to.
-one alternative is to use a very big piston as big is possible to get good power and torque at all rpm spectra, and at the same very short cutoff for max efficiency, for driveability, the bigger engine the less gas i need (steam inlet of the stroke).
-As said i think a compaund is nessesary for driveability in a car without gearbox. And by using compaund i mayby can be good to go with 30% cutoff instead of 5% at highway with double acting single cyl. And spare the weak valves to be stressed and broken down. But can you help me if i use 100mm piston 12cm stroke and 50 bar how big need the LP piston be? I was thinking using a 200mm compressor piston from a copco compressor to be good to go. a compaund cyl need be 4-5 times bigger than the hp cyl
Poppet valves: yes mayby the double beat valve then is to heavy at this short cutoffs, no time to seal, so the single beat valve with reverse grinds is good to go with? For good sealing. But with 30% cutoff in compaund layout mayby i could use a double beat valve caouse The stresses should be much less, no need for 5% cutoff for good efficiency. You talk about the engine sice matter, yes but all cars engine have smaller and smaller engines razing the engine efficiency about 30% today
but you are right but that was just some to tell. days engines being smaller and smaller, today 1.2-1.6 liters is the average engines on marketcars for good fule mileage.
-I dont understand this flexible valve can you show me some pic.
Edited 3 time(s). Last edit at 06/12/2022 12:58PM by wwilliam7.
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