Dear Alan,
have many thanks for your essay about steam-efficiency. But I disagree kindly about
Alan Robinson it (The A1) was perhaps the greatest steam locomotive ever constructed and was the pinnacle of steam design.
it (The A1) was perhaps the greatest steam locomotive ever constructed and was the pinnacle of steam design.
From a efficiency level, yes (the D&H achieved ~12% with their 2-8-0, also) - and I believe the Americans had all the knowledge to built "modern" steam locos, already.
But, except those "test-beds" nothing appeared in real live. Simplification was better, in my eyes.
This is why many people feel, that post '40 American steam-locomotives could not be developed further in a practically way.
With their casted, integrated roller-bearings machine-beds, free steaming boilers, they were rugged, reliable and competitive, making real money on the road.
Keeping them running in their most likely speed-range, they could have shown nice efficiency levels, also.
Cheers
lars
OK, I had a chance to search for Baldwin 60000 and came across the Altoona dynamometer test results.
The locomotives of Chapelon, the French railway engineer, were marvels of efficiency and power by anyone's standards. A 4-8-0 type achieved 40 indicated horsepower per ton in the 1930s, a number perhaps never exceeded. His 4-8-4 constructed in 1946 (a rebuild of an unsuccessful 4-8-2 simple type) achieved efficiencies of 12% (early diesels probably operated at a lower efficiency than this) and a cylinder power output of 5,300 horsepower. In operation it could make 4,000 drawbar horsepower at 62.4 miles per hour from an engine weighing just 146 metric tons. Coal consumption at this speed and power level were 2.641 lbs/hour/horsepower and water consumption was 14.31 lbs/hour/horsepower.
As you know, there is HP (indicated HP or "in the cylinders" HP, brake HP, drawbar HP), and then there is coal (varying BTU content), and then there is water consumption per HP-hr (with steam pressure and superheat conditions varying).
But a pound of water boiled somewhat around 300 PSI (gauge) pressure and 600 deg-F superheat temperature has enthalpy of about 1300 BTU/lb, water out of the feedwater heater at about 190 deg-F has about an enthalpy of 160 BTU/lb, water consumption of 14.31 lb/HP-hr corresponds to a heat rate of 14.31*(1300-160) = 16313 BTU/Hr, one HP-Hr is about 2550 BTU, so the thermodynamic efficiency indicated by the water consumption is 2550/16313 = 15.6 %.
Baldwin 60000, also a 3-cylinder compound as the Chapelon A-1, reported somewhere in the high 14's, low 15's lb water/HP-hr in the Altoona tests across a suprisingly wide range of cutoffs, throttle settings, and speeds, giving thermodynamic efficiencies in the 13-14 range.
However, a coal burn of 2.641 lb/hr is a BTU usage of 2.641*13,500 BTU/lb (again, that pesky question of what kind of coal?) = 35654 BTU/Hr, meaning the boiler efficiency on the A-1 was only 16313/35654 = 46% for an overall efficiency of 7.2 percent, about the same ballpark as Baldwin 60000. Yes, the Baldwin 60000 used a higher boiler pressure of 340 PSI instead of 300 PSI in a Big Boy or whatever they used in France, but that modest increase in boiler pressure results in only modest gains.
Maybe they use really low BTU coal in France, maybe there is a mixing of different HP values (IHP, BHP, DHP). But I am beginning to wonder of there is a mix of lore and wishful thinking in some of the efficiency claims.
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
timzerikemBy dropping the tonnage by 5%, the UP got 50% more speed and were less likely to stall on the hill.If you're talking about the Wahsatch climb, 5% less tonnage would mean something like 5% more speed.
erikemBy dropping the tonnage by 5%, the UP got 50% more speed and were less likely to stall on the hill.
timztimzerikemBy dropping the tonnage by 5%, the UP got 50% more speed and were less likely to stall on the hill.If you're talking about the Wahsatch climb, 5% less tonnage would mean something like 5% more speed.Careless thinking on my part. You're right, there could be some combination of speed and tonnage where 5% less tonnage would give 50% more speed-- 9 mph instead of 6 mph, maybe. I still rather doubt that the UP tests were an example of that.
Looking at the bottom right hand graph on page 21 of Kratville's book, the tractive effort declines slowly (declines by maybe 5,000 lb) from start to about 9-10 mph and then drops off much faster after that (i.e. there is a knee in the curve about 9-10 mph). Operation at a speed below the knee would make attainable speed very sensitive to trailing tonnage, but much less so above the knee.
timz timzerikemBy dropping the tonnage by 5%, the UP got 50% more speed and were less likely to stall on the hill.If you're talking about the Wahsatch climb, 5% less tonnage would mean something like 5% more speed.Careless thinking on my part. You're right, there could be some combination of speed and tonnage where 5% less tonnage would give 50% more speed-- 9 mph instead of 6 mph, maybe. I still rather doubt that the UP tests were an example of that.
The tests were against a 3 unit diesel set, but Kratville does not mentioned which one ( the test happened in 1943 - maybe it was a FT ? ), with various loads and fuel assingenments, but in all cases min. speeds were just around 13-16mph. The mentioned 5% less ton. giving 50% more speed are not valid in that case.
As it seems, no other test probably ever occoured in books about BB (or other engines) again, 'though many tests runs at Wasatch and Sherman were performed later. A couple of years ago, I asked UPHS about that, and was granted with a very nice mail and some further explanations.
With 4450tons (this was not stall weight!), they would probably run beyond 10mph, so approx. ~20% more tonnage with 50% less speed in comp. 3600tons @ 15mph.
Kind Regards
Paul Milenkovic OK, I had a chance to search for Baldwin 60000 and came across the Altoona dynamometer test results. The locomotives of Chapelon, the French railway engineer, were marvels of efficiency and power by anyone's standards. A 4-8-0 type achieved 40 indicated horsepower per ton in the 1930s, a number perhaps never exceeded. His 4-8-4 constructed in 1946 (a rebuild of an unsuccessful 4-8-2 simple type) achieved efficiencies of 12% (early diesels probably operated at a lower efficiency than this) and a cylinder power output of 5,300 horsepower. In operation it could make 4,000 drawbar horsepower at 62.4 miles per hour from an engine weighing just 146 metric tons. Coal consumption at this speed and power level were 2.641 lbs/hour/horsepower and water consumption was 14.31 lbs/hour/horsepower. As you know, there is HP (indicated HP or "in the cylinders" HP, brake HP, drawbar HP), and then there is coal (varying BTU content), and then there is water consumption per HP-hr (with steam pressure and superheat conditions varying). But a pound of water boiled somewhat around 300 PSI (gauge) pressure and 600 deg-F superheat temperature has enthalpy of about 1300 BTU/lb, water out of the feedwater heater at about 190 deg-F has about an enthalpy of 160 BTU/lb, water consumption of 14.31 lb/HP-hr corresponds to a heat rate of 14.31*(1300-160) = 16313 BTU/Hr, one HP-Hr is about 2550 BTU, so the thermodynamic efficiency indicated by the water consumption is 2550/16313 = 15.6 %. Baldwin 60000, also a 3-cylinder compound as the Chapelon A-1, reported somewhere in the high 14's, low 15's lb water/HP-hr in the Altoona tests across a suprisingly wide range of cutoffs, throttle settings, and speeds, giving thermodynamic efficiencies in the 13-14 range. However, a coal burn of 2.641 lb/hr is a BTU usage of 2.641*13,500 BTU/lb (again, that pesky question of what kind of coal?) = 35654 BTU/Hr, meaning the boiler efficiency on the A-1 was only 16313/35654 = 46% for an overall efficiency of 7.2 percent, about the same ballpark as Baldwin 60000. Yes, the Baldwin 60000 used a higher boiler pressure of 340 PSI instead of 300 PSI in a Big Boy or whatever they used in France, but that modest increase in boiler pressure results in only modest gains. Maybe they use really low BTU coal in France, maybe there is a mixing of different HP values (IHP, BHP, DHP). But I am beginning to wonder of there is a mix of lore and wishful thinking in some of the efficiency claims.
This diagramm is from Baldwin 60000' site,
... as far as I understand, it just shows steam-locomotive boilers should not be pushed too hard.
To go back to earlier questions on the thread, the Kalmbach Model Railroader Cyclopedia Volume 1 Steam Locomotives has some interesting diagrams of the installation of feedwater heaters and injectors, from page 14 onward. It is intended for modellers, but the purposes of the pipes, and pumps are identified and mean a bit to anybody interested.
I haven't found any better explanation of feed water heaters. I remember a bit from my engineering course where we had a fairly close study power station feed water heaters, more than thirty years ago.
Chapelon's book isn't very helpful about feed water heaters, although he saw them as a help in improving power output.
To return to closer posts, I am a bit concerned from reading Chapelon (in the English translation) that he does seem to take the most positive view of results. In particular, I don't think he has attempted to standardise his comparisons with other tests.
In particular the curves for Chapelon's French tests differ from German tests of equivalent locomotives.
I'm happy for them to be better or worse developing power or using fuel, but I'd expect the trends to be the same, the characteristic shape to be the same. But they aren't. I've checked German sources and the data is the same as Chapelon displays.
All the German tests follow the same trends and the French tests follow the same trends, but they don't seem to be strictly comparable.
Also, I don't think the improvements obtained with compounds were achieved with simples.
Chapelon's compounds were found to be less rugged and less reliable in service compared with the 141Rs for example, and these more basic locomotives outlasted those theoretically more efficient.
M636C
After the tests of 1943 the exhaust nozzle and firebox arrangement was changed to make the draft more efficeint. The "waffle" exhaust nozzle that was used did not seal the stack making the loco not as efficent as it could be. There was a flurry or different exhaust trials until the four port nozzle was used. This increased the draft, in turn making the fire burn cleaner getting more heat out of the fire, increasing the HP of the overall locomotive, while using the same ammount of coal. Hence, they were able to lug longer trains up the Wasatch grade. Also, the coal being used out of Odgen was from the mines in Utah with a btu around 11,000 to 12,000, not the wyoming coal that was 8,000 to 9,000 btu. If you look at a lot of the freights, there is a line of loaded coal gons tucked behind the engine for the coal towers at Echo and Evanston. The Park City local also hauled a daily train of coal to Echo.
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