How Efficient Were the "Big Three"?

[NW Mailing List]

The original poster will find a recent writeup on steam locomotive efficiency the book in “The Steam Locomotive Energy Story” by Walter Simpson, published by the C&OHS and available in the N&W Commissary. I don’t recall if it covers the N&W locomotives specifically. Trains magazine covered the topic in the article “Did we Scrap Steam Too Soon?” published in the 1970’s, and it’s addressed in a couple of contemporary books from the forties and fifties (those are harder to source). 

However, the same night I read John Rhodes response, I happened to be leafing through the November, 1927 N&W Magazine, which had an article called “Improving our Mallet Locomotives” by C.H. Paris, Engineer, Motive Power Department. Coincidentally, he covered this very topic in nice 1927 detail. Part of the article discussing the benefits of feedwater heaters is definitely worth a share in this thread. 


It may be surprising to know that of the total energy produced in the firebox of an average modern locomotive, by the combustion of coal, only 6 per cent or slightly more than one-twentieth is delivered as useful work at the drawbar. Of the total potential energy of the coal used, about 4 per cent is lost through unburned coal to the ashpan; about 8 per cent is lost as unburned cinders through the stack; 5 per cent is lost by radiation; 6 per cent is used by auxiliaries, such as stoker, air pumps, turbo-generator, etc.; about 4 per cent is lost as unburned gases and soot through incomplete combustion; 14 per cent is lost as heat in the furnace gases; about I per cent is lost as machine friction of the locomotive, and 52 per cent, or more than half of the total heat energy, is lost in the heat of the exhaust steam which is rejected by the cylinders and discharged through the smoke-stack.

There are several distinct advantages that are obtained from the use of feedwater heaters, and they may be summarized as follows: First, there is a recovery of a considerable amount of waste heat from the exhaust steam as stated above. This results in a saving of the amount of coal required to be burned, which may amount to as much as 10 or 12 per cent of the total coal used; second, for any given locomotive, delivering a given amount of power, a reduction in the amount of coal burned results in greater boiler efficiency, because, with less forcing of fires, combustion is more perfect and the rate of heat absorption by the heating surfaces is reduced and it is well known that the greatest economy in heat absorption or boiler efficiency is obtained when the locomotive is worked at less than its full coal-burning capacity; third, the exhaust steam

condensed in an open heater, such as we are using, results in a considerable saving of water, as all such steam condensed is returned with the feedwater to the
boiler. This reduces the tender capacity required, or what is probably more important, for any given tender capacity. the length of time between stops for water may be increased; fourth, the effect of a steam condensing chamber connected directly to the exhaust passages of a locomotive produces a sucking action which lowers the back pressure on the pistons and increases the cylinder horsepower.
<snip>
The effect of all these economies from the use of feedwater heaters on the practical operation of a locomotive is to increase steaming capacity <snip>.


Matt Goodman


> 
> On Friday, October 6, 2023, 02:09:14 PM EDT, NW Mailing List <nw-mailing-list at nwhs.org> wrote:
> 
> 
> Most revenue service steam locomotives maxed out at about 6% thermal efficiency. Energy of fuel used versus drawbar horsepower.  A modern AC diesel is about 30%.  It gen diesel about 20%.
> 
> The most efficient revenue steam locomotives where the Andre Chapelon compound passenger 4-8-0s in France.  High single digit thermal efficiency.  There where prototype steam engines that hut thermal efficiency over 10% but steam was dying and it wasn't pursued.
> 
> Best Regards 
> John Rhodes 
> 
> 
> On Fri, Oct 6, 2023, 10:31 AM NW Mailing List <nw-mailing-list at nwhs.org <mailto:nw-mailing-list at nwhs.org>> wrote:
> Greetings,
> 
> In the rudimentary research I've done on N&W's big three (J, A, Y6/a/b), I've gotten the impression that they were among if not the most efficient steam locomotives built in the United States, in some cases outperforming the first-generation diesels. But exactly how efficient were they? From what I've heard the maximum fuel efficiency of a steam locomotive is about 15%. Did any of the big three have the abil
> 
> Eli Santinity to reach this efficiency level?
> ________________________________________
> NW-Mailing-List at nwhs.org <mailto:NW-Mailing-List at nwhs.org>
> To change your subscription go to
> http://list.nwhs.org/mailman/options/nw-mailing-list
> Browse the NW-Mailing-List archives at
> http://list.nwhs.org/pipermail/nw-mailing-list/
> ________________________________________
> NW-Mailing-List at nwhs.org <mailto:NW-Mailing-List at nwhs.org>
> To change your subscription go to
> http://list.nwhs.org/mailman/options/nw-mailing-list
> Browse the NW-Mailing-List archives at
> http://list.nwhs.org/pipermail/nw-mailing-list/
> ________________________________________
> NW-Mailing-List at nwhs.org <mailto:NW-Mailing-List at nwhs.org>
> To change your subscription go to
> http://list.nwhs.org/mailman/options/nw-mailing-list
> Browse the NW-Mailing-List archives at
> http://list.nwhs.org/pipermail/nw-mailing-list/
> ________________________________________
> NW-Mailing-List at nwhs.org
> To change your subscription go to
> http://list.nwhs.org/mailman/options/nw-mailing-list
> Browse the NW-Mailing-List archives at
> http://list.nwhs.org/pipermail/nw-mailing-list/

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://pairlist6.pair.net/pipermail/nw-mailing-list/attachments/20231008/27aa7632/attachment.htm>