Fuel Efficiency

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In the late forties, the N&W compared the fuel efficiency of coal vs diesel from an economic perspective. The railway used equal dollar amounts of each fuel and then determined how much work could be produced at the rail. While it used what Gary said below to get at that answer, it determined that coal produced more work at the rail/drawbar than the diesel at that time for equal dollar amounts of fuel--ie, for each one dollar of coal and of diesel fuel, there was so many BTU's available. Then the railway determined how many BTU's ended up as work at the rail. The N&W's coal-burning locomotives could do better than the diesel AT THAT TIME.

Obviously the diesel got larger and more powerful since then, and fuel costs today are nothing like the late forties. This was strictly comparing costs of fuels without taking into consideration the maintenance costs associated with each type of power then. 

In the N&W's steam vs diesel tests of 1952, one comparison was the fuel costs for each thousand gross ton-miles. In 1952, this was about a stand-off being a little advantage for coal with the Class A on Scioto Division and a slight advantage to the diesel over the Y6b on the Pocahontas Division. By 1955, the technology of the diesel had advanced enough that the scales were tipped in favor of the diesel and its electric drive.

I think the N&W did consider the fuel efficiency of coal vs diesel.

Bud Jeffries
  ----- Original Message ----- 
  From: nw-mailing-list at nwhs.org 
  To: NW Mailing List 
  Sent: Thursday, January 26, 2006 10:05 AM
  Subject: Fuel Efficiency


  Ed:  Fuel efficiency between steam and diesel would be the specific fuel consumption in lbs. per hp per hr.



  In general terms, the diesel will have much better thermal efficiency- better use of the heat created for some simple reasons based on the overall cycle temperatures.  No to drift off into a general discussion of the thermodynamics, but the thermal efficiency is a function of the temperature differences in the cycle.  In this case, it is the burning temperature of the diesel fuel and its exhaust temperature (like 3000 degrees F to about 400 degrees F) compared to the peak superheated steam temperature of about 900 degrees then down to about 150 F after expansion.  That the diesel burns its expanding gas directly where the steam locomotive burns outside its steam and adds heat to the steam makes a big difference.  That heat transfer step causes a lot of losses.



  Once you add the heat to the expanding gas, you have to look at converting that energy packed into the gas/steam into mechanical work.  This conversion process (cylinders, rods and wheels or electrical generation and conversion to rotary motion in the motors) has many inefficiencies.



  Roughly you are converting 3-6% of the energy into useful work.  Modern diesel-electrics with computer controls probably convert 6 to 12 % of the energy into useful work.  Steam or Diesel, it is REALLY important to run at the optimum output speed and conditions to keep the overall fleet usage of fuel at the most efficient.  The illustration is the C&O running the H-8 Alleghanies as luggers; they were bleeding money in the fuel bills.  Steam or diesel, it is REALLY important to run at constant speed especially at the unit's optimum speed.  Very tough to run the railroad and achieve that!  



  By the way, the N&W took great pains to arrange the trackage to achieve the optimum speed over the road.  That is the main reason for owning the dynamometer car!  I have file from the N&W in the 1920's where they measured Y-3's performance hauling the coal trains through Chillicothe, Ohio with the sole purpose of determining how to revise the curves and grades so that the locomotive did not slow down past its optimum speed range.



  See the past ARROW articles on the EMD Class A and Class Y-6 tests to get the details of the performance in those days. 



  G Rolih, Cincinnati 



  -----Original Message-----
  From: nw-mailing-list-bounces at nwhs.org [mailto:nw-mailing-list-bounces at nwhs.org] On Behalf Of nw-mailing-list at nwhs.org
  Sent: Wednesday, January 25, 2006 11:30 PM
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  N&W did many studies of this type.  I believe one is in the new N&W - GIANT OF STEAM.  It was in the old one, too.



  EdKing

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    From: nw-mailing-list at nwhs.org 

    To: nw-mailing-list at nwhs.org 

    Sent: Wednesday, January 25, 2006 7:34 PM

    Subject: Re: Whither the Link and Pin ?



    Not much has changed I guess. Kind of like fuel economy numbers in cars.  Speaking of fuel economy, has anyone ever looked at the fuel efficiency of steam (ie coal) vs. diesel fuel on a strictly fuel efficiency basis?  That is, don't take into consideration maintenance on steam vs. diesel motive power?

    Ed Svitil
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