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compound engines
Posted by: Kevin Harpham (IP Logged)
Date: January 21, 2003 06:33AM
<HTML>If someone could help me out here I would sure appreciate it.
Of the best compounds ever designed (best water rates compared to other compounds) what were their %cutoffs of the high pressure cylinders at rated load, what were their expansion ratios and water rates?
Kevin Harpham
Spokane, WA</HTML>
Of the best compounds ever designed (best water rates compared to other compounds) what were their %cutoffs of the high pressure cylinders at rated load, what were their expansion ratios and water rates?
Kevin Harpham
Spokane, WA</HTML>
Re: compound engines
Posted by: C Benson (IP Logged)
Date: January 21, 2003 12:31PM
<HTML>Volume I through vol.VIII,,may help some,,,,We have a 1893 E.P.Allis engine here in Boston,,it is real close in effeciency to a modern terbine,,,,But maintance is where it fell short on the bookeepers books,,,,so it is off line now,,,,30' from floor to top catwalk,,,crank line at floor,,,the rest is downstairs,,,,,bore 2--4--8 ft,,,,stroke 88'' 820HP at 15 RPM Its right next to a LEVETT pumping engine,,,,a horozontal Allis-Chalmers tandem is right beside,,,This is in the Chestnut Hill Pumping station Til some years ago they ran the E.P.Allis [1893] 24 or 48 hours a month thus keeping it on standby duty,,,,The whole interior is WALNUT paneling,,,wainscoat,,,,,ceiling an all,,,,2 of these engines were state of the art at the time and well documented,,,,,I cant recall the books tho,,,,Some of Walt Dunn's books are going on e/bay at present,,,,Walt joined as fireman on B& M RR before the war,,,,,He helped me buy a 1915 Pierce wrecker in 1954,,,,ooops rambling again,,,Big engine effency shouldnt be compared t small,,there is unlimited space an' wt limits on stationary applications,,,,XXXXXno snow,,clear,,,,temp -5 will be colder tonite,,,,Hey but its dry air,,,hahaha,,,Cheers Ben in Maine</HTML>
Re: compound engines
Posted by: Tom Ward (IP Logged)
Date: January 21, 2003 02:29PM
<HTML>We in Michigan don't mind the cold because it's a dry cold. IMHO the lower efficiency of smaller expanders is due to the cubed square rule: i.e. not enough volume for the surface area. Modern ceramics might overcome the limitations for those willing to pay.</HTML>
Re: compound engines
Posted by: Jerry Peoples (IP Logged)
Date: January 22, 2003 05:49PM
<HTML>According to Heat-Power Engineering, Part I, page 400, cutoff on the high pressure cylinder is typically 50 to 70 percent. For a two cylinder compound, without independent low pressure cutoff, the effective cutoff may be calculated by dividing the high pressure cylinder cutoff by one (1) plus the square of the ratio of the low pressure cylinder diameter to the high pressure cylinder daimeter. Thus, for a high pressure cutoff of 60% and a cylinder ratio 5 to 3, the effective cutoff would be 15.8 percent.
Jerry</HTML>
Jerry</HTML>
Re: compound engines
Posted by: Kevin Harpham (IP Logged)
Date: January 22, 2003 08:40PM
<HTML>Jerry,
Thanks for putting it simple. The books I have either show a picture and say ‘this is a compound’ or they are math intensive and worded in a fashion that I can’t follow well, if at all.
Still learning.
Kevin</HTML>
Thanks for putting it simple. The books I have either show a picture and say ‘this is a compound’ or they are math intensive and worded in a fashion that I can’t follow well, if at all.
Still learning.
Kevin</HTML>
Re: compound engines
Posted by: Martin Werbeck (IP Logged)
Date: January 28, 2003 09:21AM
<HTML>Hello Kevin !
One of the most efficient steam engines ever built was the experimental Schmidt quadruple-expansion engine from about 1921.
It worked at 804 psi /869 °F and expanded the steam all the way to
2,32 psi , then exhausting into a vacuum of 98 % (=0,29 psia).
The steam was reheated twice to avoid condensation in the low pressure cylinders.
The water rate was about 5,6 lb/ihphr giving an engine efficiency of 31,7 %
( probably without mechanical losses)
The engine was stationary and it is impossible to obtain a vacuum that high in an air-cooled car condenser.(Except when you run it at the north pole !)
I believe the best result from Doble`s triple expansion engine was 7,18 lb/bhp with about 9 expansions.
The problem is, that at low power outputs, with the steam throttled, the pressure drop may not be sufficient to run the low pressure cylinders, they would just pump the steam in and out. When the steam is reheated this would only result in very hot low pressure exhaust steam , greatly reducing the efficiency.
For a car , a simple expansion engine with separate inlet and exhaust ports and small clearance volume, ist probably the best.
This has also the advantage that the average temp. is lower than in the high-pressure cylinder from a compound, making lubrication easier at high steam temperatures.
Regards, Martin</HTML>
One of the most efficient steam engines ever built was the experimental Schmidt quadruple-expansion engine from about 1921.
It worked at 804 psi /869 °F and expanded the steam all the way to
2,32 psi , then exhausting into a vacuum of 98 % (=0,29 psia).
The steam was reheated twice to avoid condensation in the low pressure cylinders.
The water rate was about 5,6 lb/ihphr giving an engine efficiency of 31,7 %
( probably without mechanical losses)
The engine was stationary and it is impossible to obtain a vacuum that high in an air-cooled car condenser.(Except when you run it at the north pole !)
I believe the best result from Doble`s triple expansion engine was 7,18 lb/bhp with about 9 expansions.
The problem is, that at low power outputs, with the steam throttled, the pressure drop may not be sufficient to run the low pressure cylinders, they would just pump the steam in and out. When the steam is reheated this would only result in very hot low pressure exhaust steam , greatly reducing the efficiency.
For a car , a simple expansion engine with separate inlet and exhaust ports and small clearance volume, ist probably the best.
This has also the advantage that the average temp. is lower than in the high-pressure cylinder from a compound, making lubrication easier at high steam temperatures.
Regards, Martin</HTML>
Re: compound engines
Posted by: Kevin Harpham (IP Logged)
Date: January 31, 2003 04:28AM
<HTML>Martin,
Thanks for the info.
I agree that there are better routes to take than a compound. What interests me is how well some of these engines did considering the added friction, the drop losses, all that surface area and throttling.
I like to learn as much as possible about different engines. I recently ordered a book from Alibris and received word back that it was no longer available. If I remember correctly, it was an instruction booklet for the operation and maintenance of a marine engine called the Ajax compound uniflow.
Any idea how it works?
If I had to guess I would say it is a normal compound or triple with a uniflow low-pressure cylinder, I don’t see how it could be the other way.
Maybe someday I will come across some info on it or a cutaway.
Kevin</HTML>
Thanks for the info.
I agree that there are better routes to take than a compound. What interests me is how well some of these engines did considering the added friction, the drop losses, all that surface area and throttling.
I like to learn as much as possible about different engines. I recently ordered a book from Alibris and received word back that it was no longer available. If I remember correctly, it was an instruction booklet for the operation and maintenance of a marine engine called the Ajax compound uniflow.
Any idea how it works?
If I had to guess I would say it is a normal compound or triple with a uniflow low-pressure cylinder, I don’t see how it could be the other way.
Maybe someday I will come across some info on it or a cutaway.
Kevin</HTML>
Re: compound engines
Posted by: David K Nergaard (IP Logged)
Date: January 31, 2003 12:52PM
<HTML>I don't know about the Ajax, but the Skinner compound uniflow is written up in "Modern Marine Engineers Manual", Cornell Maritime Press, 2nd edition. They did not prove to be as reliable as the normal Skinner uniflow marine engines and were only marginally more efficient.</HTML>
Re: compound engines
Posted by: Peter Heid (IP Logged)
Date: January 31, 2003 10:12PM
<HTML>Kevin,
The Ajax compound is mentioned in many marine engineering books I have run across. Though I can't tell you much about it without looking it up, I will find a couple book titles with details on the engine if you like. It is comon to see it listed in marine manuals from around WW2.
Peter Heid</HTML>
The Ajax compound is mentioned in many marine engineering books I have run across. Though I can't tell you much about it without looking it up, I will find a couple book titles with details on the engine if you like. It is comon to see it listed in marine manuals from around WW2.
Peter Heid</HTML>
Re: compound engines
Posted by: Kevin Harpham (IP Logged)
Date: February 01, 2003 06:24AM
<HTML>David,
I just placed an order for the manual you mentioned. Thanks for the reference.
Peter,
I would appreciate a couple book titles I can chase down. Also you might be able to just tell me if the Ajax is of similar design to the Skinner David just mentioned. I have information about the Skinner on the way.
Kevin</HTML>
I just placed an order for the manual you mentioned. Thanks for the reference.
Peter,
I would appreciate a couple book titles I can chase down. Also you might be able to just tell me if the Ajax is of similar design to the Skinner David just mentioned. I have information about the Skinner on the way.
Kevin</HTML>
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