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.
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
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.
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.
Cheers
lars
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.
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.
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
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.
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
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.
My sources indicate that the UP 4000 class could exert a starting tractive effort of 135,000 pounds. Of course, at speed the tractive effort would decrease. Best horsepower was obtained in the 35 to 40 mile per hour range. Slower than this, the engines were not using all the steam the boiler was capable of producing.
Steam locomotives (and other steam engines both reciprocating and turbine type) operate on the Rankine cycle. As with other thermodymanic cycles, there are four parts, compression, addition of heat energy at the high temperature, expansion, and extraction of heat energy at the low temperature. All can be modeled as either closed cycle, where the working fluid is used repeatedly, or open cycle, where the working fluid is used once and then must be replenished. A non-condensing steam engine is an open cycle machine.
The reason that the Rankine cycle was the first to be commercialized was due to several factors. First, the Rankine cycle involves a phase change in the working fluid. The fluid is condensed at the low temperature point from a gas to a liquid, and then the compression is done by means of a pump of some sort, either an injector or a conventional pump of some kind. Because the volume of the condensed water is so small compared to the volume of the evaporated steam, and because liquids are non-compressible for all practical purposes, the energy required for the compression part of the cycle is small compared to other cycles where the compression takes place with the working fluid in a gaseous state.
Second, a practical engine generating useful amounts of power could be made with simple materials and machinery that were available early in the history of the industrial age. There was no requirement for high speed parts or rapidly turning precision bearing types.
Thus the simpler open cycle machine was quite practical to build and the cycle itself is conceptually simple, simple enough to understand even before anything was really known about thermodynamics or modern physics. The use of water allowed the open cycle to easily dump the waste heat at the end of the cycle into the atmosphere, an inexhaustable heat sink, unlike some other machines such as the Stirling cycle, which needed a heat exchanger of some kind to dump waste heat into the atmosphere or a cooling jacket of some kind.
Practical machines could be built that didn't even require high pressure steam at all. The first machines such as Newcomen's design that was used to pump out coal mines, used steam at atmospheric pressure and operated by condensing the steam in the cylinder and using the resulting vacuum to operate the large diameter cylinder and lift water out of the mine. Efficiency was low, but it worked. Even the genius of James Watt, who used the steam expansively on a double acting piston, didn't like high pressure as the likelihood of boiler explosions was high with the primitive materials avaliable before 1800.
With the advent of high pressure steam, locomotive construction became practical. Pressures were low by modern steam standards, being no more than 100 pounds per square inch even by the late 1800s, but the increased pressure did two things. It increased the amount of expansive work that could be done by the steam and it also increased the upper temperature at which heat was added from the firebox. Both served to increase efficiency. Superheating allowed still higher temperatures to be achieved, reducing condensation losses in dry pipes, valves and cylinders and improving efficiency still further. With superheating, the next limit became the lubrication of valves and cylinders. Slide valves especially couldn't stand higher temperatures and pressures, so they were replaced with cylindrical valves. Compounding had the potential for improving efficiency as well, but except in the Mallet type it was mostly abandoned as presenting too much mechanical complexity for the rewards to be gained.
All of this depends largely on the benefits inherent with the Rankine cycle operating open loop. Attempts to operate railroad locomotives closed loop were limited, confined to places where water supply or quality were such to make prohibitively expensive open loop operation. The condensing locomotives used in South Africa were the most well known examples, but though quite successful, they required rather immense tenders to accomodate the large condensing surfaces to dispose of the waste heat into the atmosphere.
Brayton cycle engines (gas turbines being the best known example) operate open loop in railroad service, the Union Pacific gas turbines being the best example. They are capable of achieving very high horsepower in a relatively compact and lightweight package. However, they have a big disadvantage in that their efficiency drops off rapidly as they throttle down. This has to do with the reduction of pressure ratio (roughly equivalent to compression ratio in an internal combustion engine) as the engine speed spools down at part throttle, the only way to reduce the power output of an open cycle gas turbine. (Note that a Rankine cycle engine operates at approximately the same temperatures and pressures, and thus approximately the same efficiencies, no matter what the throttle setting.) This, as much as anything doomed the UP's turbines to retirement. By the way, it is a characteristic of the Brayton cycle that they have a large amount of "backwork", meaning that the work required to operate the compressor is a large fraction (typically about 2/3) of the work produced by the turbine. Clearly compressor and turbine efficiencies plays a large part in the overall efficiency of such a machine. Even the addition of regenerators (adding a lot of weight, space and mechanical complexity) do not overcome this fuel consumption problem and they are hard to incorporate in the limited space of a locomotive.
Diesels (Otto cycle) have many advantages for rail service. High compression ratios produce relatively high efficiencies and the required heavy construction necessary to cope with the high internal pressures are no disadvantage in railroad service. They maintain good efficiency except when they are heavily overloaded. As excess fuel is fed to a diesel, it produces very little additional power for the additional fuel. Thus, these engines really are horsepower limited, unlike a steam locomotive that can be overloaded quite heavily with comparatively smaller reductions in efficiency.
Stirling engines have never been very attractive for railway service as they are large for the horsepower produced and they require a low temperature heat sink to discard the waste heat. For high horsepower the required high and low temperature heat exchangers would become rather cumbersome.
The Carnot cycle is not a practical cycle for a real engine as it is incapable or producing power at a rate that would be useful for much of anything. It is incorrect to assume that any practical engine approximates the Carot cycle. None of the practical engines come anywhere near approaching reversible conditions. Isentropic operation would require more than no thermal or mechanical friction losses. It requires that the changing conditions in the working fluid (expansion, for example) occur in a manner that the flow has no internal losses, no internal friction, no swirls or turbulence. The flow must be perfectly smooth and laminar in nature. Normally this requires extremely low velocities, no sharp corners in passages, perfectly smooth walls, etc. This is simply not achieveable in a practical engine. It isn't even approximated. Thus, where a simple analysis of the theoretical efficiency of an engine (taken from an evaluation of the high and low temperature sinks) might show 50%, the actual efficiency due to the non-reversibilities would be less than 20%.
By the way, the idea that steam engines can only operate in the low single digit efficiencies is a fallacy. The best Rankine cycle engines (large stationary plants used to generate electricity) operate at 35 to 40% and supercritical plants do even better.
Boiler pressure isn't everything when it comes to efficiency. The temperature at which heat is transferred to the working fluid is what matters. This is why superheating gave such a boost to steam locomotive efficiency. The working fluid (steam) could be heated far above the temperature at which water in the boiler would change from liquid to gas. Stationary steam plants send the superheated steam through the high pressure turbine stage, and then back into the boiler combustion chamber where it is reheated again to the same superheat temperature but at a lower pressure. It is then sent to the medium pressure turbine stage. This same technique was tried in some compound locomotives with something called a smokebox reheater where the exhaust steam from the high pressure cylinders was reheated by sending the medium pressure steam through a reheater in the smokebox where it could pick up additional heat. Eventually, such reheaters were replaced with an additional set of superheater tubes that allowed for higher reheat temperatures and subsequent higher efficiencies. This is an analogous concept to reheating in a stationary steam plant between the high pressure stage and the medium pressure stage.
Why, then, couldn't a steam locomotive achieve the same high efficiency of a stationary steam plant? One issue is that a stationary steam plant really does operate at higher temperatures and pressures. A watertube boiler such as that used in a stationary steam plant has the high pressure water and steam on the inside of the tubes and drums. The expansive forces tend to keep the tubes round and intact. In a firetube boiler, the pressure of the steam within the boiler wants to collapse the tubes, and thus the boiler pressure is limited to what the tubes and flues can withstand. Another is that a stationary steam plant has room for large pipes with optimized dimensions for good flow conditions that simply aren't possible in the limited loading gauge of a steam engine. Remember, every, restriction in a passageway causes a pressure loss with a subsequent drop in temperature and thus efficiency. This is why your analysis of the exhaust temperature at the blast pipe is not a good approximation. A steam locomotive, with its losses in the many feet of pipe between the steam dome and the blast pipe, would have had much higher losses than you surmise. (Surprisingly, the efficiency of the fire tube boiler used in steam locomotives was very good. They could achieve efficiencies and steaming rates very rarely obtained in stationary boilers operating at the same temperatures and pressures.)
Yes, there were several types of feedwater heaters to capture some waste heat and preheat the water before it was injected into the boiler. This was to prevent "quenching" the evaporation of the water in the boiler as much as anything. A standard steam injector did heat the feedwater to some extent and was thus superior to the crosshead pump used previously. The exhaust steam injector could use exhaust steam for the same purpose, and was something of a "poor man's feedwater heater", but it had to be started using live steam first before shifting to exhaust steam. One disadvantage of this type of injector is that oil from the valves and cylinders would be injected into the boiler along with the feedwater where it could cause problems. This was also a potential problem with the "open type of feedwater heater where exhaust steam would come into contact with the supply water, as opposed to closed type feedwater heaters where the exhaust steam would not come into contact with the boiler feedwater. The closed types were preferred in the early days of feedwater heater use, but later, as methods of separating out the oil from the feedwater got better, the open types started to be preferred because of simpler construction and maintenance.
The best examples of steam locomotive efficiency were probably not achieved in any North American locomotive, or even in any production locomotive. 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. He did this by paying careful attention to the configuration of all the steam passages in the machine including the exhaust system and the valving as well, and by using a three cylinder compound design. This locomotive was designed for fast heavy express passenger service and from these numbers it is clear that all design objectives were met. Though only one was built, it was perhaps the greatest steam locomotive ever constructed and was the pinnacle of steam design.
Paul,
I came back to Baldwin`s 60000 web-page and had some fun with the numbers:
though, it had a Worthington feed-water, it contained some modern boiler aspects and achieved during tests coal/to water ratios of 6-7% and boiler efficiency of 50-70%.
The fun is, however, taken from the test on the ATSF
tests results show, BB (and other BIG articulates ) would produce more than double of HP in the speed of 10-14mph.
OK, blame me for this unfair comparison, but Baldwin 60000 is not a small loco at all, but BB is not double big either.
But nothing from the Baldwin was adapted to later built engines.
-edit-
Anyway, do locomotive compatible boiler-based steam-turbines exist?
Any propagation to put it on a locomotive frame?
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. It's not clear just what Le Massena was trying to say in that paragraph, but it we can't accuse him of saying 5% less tonnage means 50% more speed.
let us compare it with those test-data:
I made a mistake by writing min. speeds of all runs was 13-mph.
Actual with run no. 4004 it was 15.9mph (the lightest one with 3539tons).
The heaviest of this trio was 3883tons with engine 4016. Here the occasionally min. speed was 13mph, regularly 14mph on 1.14% grade (~4300hp).
Engine 4004 produced ~14% more speed with ~9% tonnage, Echo to Evanston: Water/Evap. per Coal 4.72% against 4.15% of engine 4016.
It is a difference, but not as big as the propagated 5% less tons and 50% more speed.
erikem This relates to La Massena's thesis in his article "The Big Engines". The UP could have made up their trains to make use of the Big Boy's peak tractive effort of a bit over 120,000 lb, but the train would have been slugging up the hill at less than 10 MPH. By dropping the tonnage by 5%, the UP got 50% more speed and were less likely to stall on the hill. I was also getting a figure of a bit over 4% for thermal efficiency from the Big Boys from the data in Kratville's book. I wonder what tractive effort and speed combination would give the best thermal efficiency? A WAG on my part would be say 40,000 lb at say 30 MPH, where the throttle would be wide open, the reverser hooked up as tight as can be to get maximum expansion. The locomotive would be running at less than maximum power which "should" help improve both combustion efficiency and heat transfer efficiency. - Erik
This relates to La Massena's thesis in his article "The Big Engines". The UP could have made up their trains to make use of the Big Boy's peak tractive effort of a bit over 120,000 lb, but the train would have been slugging up the hill at less than 10 MPH. By dropping the tonnage by 5%, the UP got 50% more speed and were less likely to stall on the hill.
I was also getting a figure of a bit over 4% for thermal efficiency from the Big Boys from the data in Kratville's book. I wonder what tractive effort and speed combination would give the best thermal efficiency? A WAG on my part would be say 40,000 lb at say 30 MPH, where the throttle would be wide open, the reverser hooked up as tight as can be to get maximum expansion. The locomotive would be running at less than maximum power which "should" help improve both combustion efficiency and heat transfer efficiency.
- Erik
Thank you Erik,
as you mentioned it, does somebody know what peak tractive effort BB could excert? With a 4000tons train it was 115.000lbs, final ratings were 4450tons, 10percent more, so 126.500lbs? I could never figure it out, my guess that would lug BB down to 5-10mph.
Kratville stated, "later, they performed so well... in the final years of steam they were given 4450 tons". The 4450 tons rating occured 1948, btw. However the book leaves us railfans pretty alone about that.
Paul MilenkovicSo 115,000 lb tractive effort at 14 MPH works out to about 4300 HP -- somewhat less than the max 6000 HP, but to be expected at "grade climbing speed."
So 115,000 lb tractive effort at 14 MPH works out to about 4300 HP -- somewhat less than the max 6000 HP, but to be expected at "grade climbing speed."
10 tons of 10,000 BTU/lb coal at 4300 HP works out to about 5.5% coal-to-tractive-effort efficiency -- about in the ballpark of those mentions of efficiency in the mid 4% range.
Paul MilenkovicI remember some time in the late 1960's living in Boulder, Colorado and hanging out with the local model railroaders and railfans, and hearing something about a "steam ejector" that "could have saved steam." Not to get the "should have kept steam longer" debate going again, but you have to remember that 1969 was just 10 years after Norfolk and Western dropped the fire on their last Y-class, and Colorado narrowgauge steam was a going concern until the mid 60's? Years later I think they were talking about Kylchap or Giesel or whatever kind of improved exhaust drafting nozzle, and I always wondered how what I considered to be minor modifications to the boiler draft could make that big a difference for what was inherently a low boiler pressure, non-condensing, inefficient steam cycle.
Years later I think they were talking about Kylchap or Giesel or whatever kind of improved exhaust drafting nozzle, and I always wondered how what I considered to be minor modifications to the boiler draft could make that big a difference for what was inherently a low boiler pressure, non-condensing, inefficient steam cycle.
The trains article was on the Giesel ejector. The advantage was not so much how much more draft it could produce, but how much less back pressure was needed for the draft. Think advantages of using a condenser on a steam turbine versus exhausting at atmospheric pressure.
Paul, as you started this thread about thermal efficiency about feedwater-heaters,
I would like to ask everbody interested, following:
is it true that in post '40 era. the Railroads tendencies were using commonly more simple parts like Type A super-heaters and Worthington feed-waters without hardly notable performance decrease?
Paul, have you already googled for baldwin's 60000 test results, if not this may interest you.
carnej1Lars Loco Right on Paul, but please consider, as you mentioned it, a steam-turbine-electric was never successful (water and electricity packed close together on a locomotive frame... ouch!). In addition, UPRR did some serious own research about designing good draft systems. In case of BB, the second run to Green River was easier and may have shown better boiler-performance. Instead of putting "fancy" gadgets on steamlocomotives, running lighter trains with them could habe been a better alternative. Cheers lars While your statement holds true for the N&W and C&O coal fired steam turbines my understanding is that the GE and Westinghouse oil burning turbine electrics were technically successful. They were not however, economically competitive with their biggest oil burning competitor, the diesel electric locomotive..
Lars Loco Right on Paul, but please consider, as you mentioned it, a steam-turbine-electric was never successful (water and electricity packed close together on a locomotive frame... ouch!). In addition, UPRR did some serious own research about designing good draft systems. In case of BB, the second run to Green River was easier and may have shown better boiler-performance. Instead of putting "fancy" gadgets on steamlocomotives, running lighter trains with them could habe been a better alternative. Cheers lars
Right on Paul,
but please consider, as you mentioned it, a steam-turbine-electric was never successful (water and electricity packed close together on a locomotive frame... ouch!). In addition, UPRR did some serious own research about designing good draft systems. In case of BB, the second run to Green River was easier and may have shown better boiler-performance. Instead of putting "fancy" gadgets on steamlocomotives, running lighter trains with them could habe been a better alternative.
While your statement holds true for the N&W and C&O coal fired steam turbines my understanding is that the GE and Westinghouse oil burning turbine electrics were technically successful. They were not however, economically competitive with their biggest oil burning competitor, the diesel electric locomotive..
From a theoretical standpoint, UPRR steam turbine 1+2 from 1939 were successful, too and could have been further improved, but they never made real money on the road (maybe some bucks for the GN, though)
Lars
Railway ManLars LocoRight on Paul, but please consider, as you mentioned it, a steam-turbine-electric was never successful (water and electricity packed close together on a locomotive frame... ouch!). In addition, UPRR did some serious own research about designing good draft systems. In case of BB, the second run to Green River was easier and may have shown better boiler-performance. Instead of putting "fancy" gadgets on steamlocomotives, running lighter trains with them could habe been a better alternative. Cheers lars A better alternative to what? Are you saying the railway would have made more money if it ran its trains faster?RWM
Lars LocoRight on Paul, but please consider, as you mentioned it, a steam-turbine-electric was never successful (water and electricity packed close together on a locomotive frame... ouch!). In addition, UPRR did some serious own research about designing good draft systems. In case of BB, the second run to Green River was easier and may have shown better boiler-performance. Instead of putting "fancy" gadgets on steamlocomotives, running lighter trains with them could habe been a better alternative. Cheers lars
A better alternative to what? Are you saying the railway would have made more money if it ran its trains faster?
RWM
Hello Rail-Way Man,
yes, certainly, not on all conditions but generally yes.
It could make better sence, to operate a couple of trains more per day and keep the mainline busy and fluid.
This is, from what I understand, are showing the results of BB test runs.
Let's have a look, the lightest train with engine 4004 and 3539tons took Wasatch with a good clip of 21,2 mph, and needed 20min less than the other two runs (approx 4hours for 75miles). And as written, this time "the 4004 really rolled them that evening, because the high iron was loaded with many trains..."
In all cases, the minimum continuous speed was 13-14mph from milepost 942 eastward to 928 at a continuous grade of 1,14%, keeping the train one hour working there.
That performance is OK in my eyes,
Otherwise, just put some more hundred tons on the train, it than maybe working two hours on the grade with 7-8mph and wasting fuel and low economical performance.
Instead of putting "fancy" gadgets on steamlocomotives, running lighter trains with them could habe been a better alternative. Cheers lars
That is probably a contributor to the proliferation of steam locomotive "types" and wheel arrangements, and by contrast, Diesels are more standardized. My guess is that a Diesel gets more thermally efficient the more time it spends at max power settings, and as such, you can lug Diesels down until they stall and tie up the railroad line before fuel costs start increasing -- in fact, you have higher fuel costs for putting enough power on your trains. This need to operate "at the golden mean" with steam whereas Diesels can be loaded down until you stall or burn up the traction motors may also have contributed to the need for more helper districts with steam rather than some intrinsic inability to build steam locomotives with enough powered axles (consider the "double Garratt" proposals).
One thread running through accounts of the history of steam is that the "fancy" gadgets (apart, perhaps, from Schmidt's superheater) never caught on -- even if the "gadgets" (compound expansion, higher boiler pressure) were workable, what they save in fuel never seemed to balance out what they cost in increased maintenance.
High pressure boilers are one of the "fancy gadgets that never caught on." The C&O coal-fired steam turbine did not use a particularly high boiler pressure, but the N&W Jawn Henry used a somewhat higher boiler pressure (500 PSI?) and I thought the oil-burning condensing turbine electric tested on the UP used a 1000 PSI water tube boiler, although I believe that one was condensing so they could afford to use demineralized water to get around the scaling and foaming problem of the common quality of water used once-through in most steam locomotives.
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
OK.
10,000 gal water/hr evaporated times 8 lb/gal times (1314 - 150) BTU/lb = 105 million BTU/hr.
The number 1314-150 is the enthalpy of steam at 315 PSI absolute (300 PSI gauge), 600 deg-F superheat temperature, minus the enthalpy of water at about 180 degrees, which I am assuming is the temperature of the feedwater with whatever feedwater device they had. Enthalpy is this fancy name for the energy in a system at constant pressure but you allow the volume to change -- when you boil water, you want to know the enthalpy change because boiling takes place at constant pressure but allows the volume to change.
Assuming 12,000 BTU/lb coal
10 (short) tons times 2000 lb/ton * 12,000 BTU/lb = 240 million BTU (per hour)
That means the combustion or boiler efficiency is 105/240 = 43.8 percent.
I remember some time in the late 1960's living in Boulder, Colorado and hanging out with the local model railroaders and railfans, and hearing something about a "steam ejector" that "could have saved steam." Not to get the "should have kept steam longer" debate going again, but you have to remember that 1969 was just 10 years after Norfolk and Western dropped the fire on their last Y-class, and Colorado narrowgauge steam was a going concern until the mid 60's?
But if you are running your boiler at 44 percent combustion efficiency, there is a lot of money left on the table, or perhaps a lot of money simply going up the stack. One school of thought is that if steam was to have modernized and kept up with the emerging Diesel competition, one would have had to go to what the electric utility people did: high boiler pressure, condensing, steam-turbine electric drive, and so on -- the closest thing was that GE condensing steam turbine that ran on the UP and other places in the 1940's. The other school of thought is that even within the confines of an "inefficient" thermodynamic cycle, improvements in the boiler draft, combustion arrangement, boiler and cylinder insulation, steam circuit pressure drops, that the accumulation of such "little" changes could bring large improvements. Chapelon and later Porta and Wardale were in that camp. Simply bringing efficiency from 4% to 8% would cut coal and water use in half, with important logistical savings in supplying that much coal and water out on the railroad lines.
Thank you RWM for correcting this.
You are right on, I did not looked up where these mines sit now, but was not aware of those great regional differences of quality of coal in Wyoming/Utah.
I just cited those values, to have a start for Paul's calculations.
Yet, we still do not know what coal was used (maybe UP's coal companies sold the better coal for customers, leaving the worse coal for their engines?).
I do not think that would lead to so false conclusions at all:
Paul calculated 5,5% efficiency with 10.000Btu/lb., with ~12.000Btu/lb, those mentioned 4,5 - 4,7% efficiency would be still in the ballpark, wouldn't it?
Paul, have you interest to re-run your calcs with 11.500Btu/lb. and 12.500Btu/lb.?
Lars LocoDear Railway Man, at UPRR's homepage, a table of current operated Wyoming coal mines (here: http://www.uprr.com/customers/energy/coal/coalspec.shtml ) show a value of 9700- 9800 btu/lb. They are not necessarily the mines that supplied fuel for steam-engines (Hanna / Rock Springs is not listed anymore), but give a course of how low the grade of coal in this area is. Anybody wonder now, why some steam engines smoked so badly? Cheers, lars
Dear Railway Man,
at UPRR's homepage, a table of current operated Wyoming coal mines (here: http://www.uprr.com/customers/energy/coal/coalspec.shtml ) show a value of 9700- 9800 btu/lb.
They are not necessarily the mines that supplied fuel for steam-engines (Hanna / Rock Springs is not listed anymore), but give a course of how low the grade of coal in this area is. Anybody wonder now, why some steam engines smoked so badly?
Cheers,
Dear Lars: I am sorry, Wyoming is not a uniform state with uniform coal values. Nor does any U.S. state produce uniform coal with uniform values.
The Wyoming mines you have cited above are in the Gillette Field of the Powder River Basin Coal Region, and those mines produce sub-bituminous B or C coal of 8,500 to 9,800 BTU -- mostly more in the 8,500 range. These mines never produced coal for railway fuel for Union Pacific Railroad, and these mines produced none for any railway locomotive at all as none of these mines even existed until the 1970s. There was some mining in the Gilette field prior to the 1970s, particularly in the Glenrock area, but it was not a major source for railway fuel except for some branch lines and short lines in the area.
Union Pacific Railroad purchased its railway fuel from mines extracting coal from the Rock Springs and Hanna Fields of the Green River Coal Region, and the Kemmerer Field of the Hams Fork Coal Region, which is an entirely separate, unrelated, geologic formation, located several hundred miles distant. These mines typically produce a high-volatile bituminous C or mid-volatile bituminous coal with heating values in the 11,500 to 12,500 BTU range. These mines produced from circa 1870 to present, though most of their eastbound utility market disappeared after 1985.
Any conclusions drawn about locomotive performance on UP using the characteristics of the coal you cite above would be incorrect conclusions, but I feel like I am tilting against railfan windmills here. If you really want to know about railway coal use, and its relation to railway locomotive performance, read the book "Railway Fuel," by Eugene McAuliffe, who was the president of the Union Pacific Coal Company (many railways owned their own mines).
Note that Northern Pacific Railway did use Powder River Basin coal extracted from a company mine at Rosebud, Montana, which is the poor-coal end of the basin with values in the mid-8000 BTU range. This is a sub-bituminous C coal but railfans often incorrectly call it lignite. Lignite is a lower grade of coal yet, typically with BTU values in the 6,000 range.
Dear Paul,
with big interest read your calcs. We also have to consider some variable factors (cold weather, slippery rails occured, non so feasible conditions). They also used 3 different throttle/cut-off settings during the tests, the lightest train at 3500tons showing better fuel consumption results. This fits nicely to the originally task of taking a 3600tons train unassisted to Wasatch and not to overload steam-locomotives.
We only may ask, what did they had in their mind to set the ratings at Wasatch up to 4450tons later? Any plausible explanation?
Lars Loco Dear Railway Man, at UPRR's homepage, a table of current operated Wyoming coal mines (here: http://www.uprr.com/customers/energy/coal/coalspec.shtml ) show a value of 9700- 9800 btu/lbs. They are not necessarily the mines that supplied fuel for steam-engines (Hanna / Rock Springs is not listed anymore), but give a course of how low the grade of coal in this area is. Anybody wonder now, why some steam engines smoked so badly? Cheers, lars Paul, if you read somewhere BB used 40t coal, that was the overall consumption from Ogden to Wasatch/Evanston. BB used 10 tons coal per hour, with 28t in the tender this was ample load for a 1 hour call, then covering the 40miles to Echo within one hour and 40 min and a reserve for occasionally stops on sidings for more priority trains or traffic. At Echo, they were reloaded within 20min, then they worked hard up the grade, including 15miles or so on continious 1,14% to Wasatch within 2hours, covering 30 miles. Engine 4016 exerted a cont. TE of up to 115.000lbs at 14mp/h with almost 4000tons freight. That was BB's run. Cheers lars
at UPRR's homepage, a table of current operated Wyoming coal mines (here: http://www.uprr.com/customers/energy/coal/coalspec.shtml ) show a value of 9700- 9800 btu/lbs.
if you read somewhere BB used 40t coal, that was the overall consumption from Ogden to Wasatch/Evanston.
BB used 10 tons coal per hour, with 28t in the tender this was ample load for a 1 hour call, then covering the 40miles to Echo within one hour and 40 min and a reserve for occasionally stops on sidings for more priority trains or traffic. At Echo, they were reloaded within 20min, then they worked hard up the grade, including 15miles or so on continious 1,14% to Wasatch within 2hours, covering 30 miles. Engine 4016 exerted a cont. TE of up to 115.000lbs at 14mp/h with almost 4000tons freight.
That was BB's run.
Evaporating 10,000 gal/hr of water to 300 PSI boiler pressure (315 PSI absolute) to 600 degree-F superheat temperature, about 1300 BTU/lb water according to my steam tables, assume 150 BTU/lb heat recovery from an exhaust steam boiler feed injector, works out to 11.9% thermodynamic efficiency. This puts the boiler efficiency at 46%, low compared to the reported value of 60%, but perhaps reasonable under conditions of "hard working" where one probably is losing some fuel as carbon particles in the exhaust smoke.
For 315 PSI (absolute) boiler pressure, 600 deg-F superheat temperature, 50 percent cutoff, 20 PSI (absolute) exhaust back pressure, the theoretical thermodynamic efficiency computed from steam tables works out to 14.2 percent.
For the actual thermodynamic efficiency (steam-to-tractive-effort) to be within 80% of the theoretical thermodynamic efficiency seems very good. For the boiler to be operating below 50 percent efficiency (below the 60 percent value quoted earlier but above Don's estimate of 30 percent for some steam engines) seems not so good, and perhaps the best place to work on improvement.
Our community is FREE to join. To participate you must either login or register for an account.