Effects of Pressure Altitude on Steam Engine Efficiency

[NW Mailing List]

Hi Christopher. I’ll take a swing at this. My initial thought on this is that given the boiler is a pressure vessel, atmospheric pressure would not come into play with regard to internal steam pressure or temperature. Externally, it would seem that at higher altitudes more combustion air would be have to move through the firebox to supply the same amount of oxygen for fuel combustion (for a given heat output). 

But that’s a layman’s point of view. I checked the book “The Steam Locomotive” by M.E. Johnson (Baldwin’s Chief Engineer), courtesy my dad’s library. Mr Johnson makes no reference to altitude from a boiler performance standpoint, which leads me to believe it wasn’t a substantial factor.

Matt Goodman
Columbus, Ohio, US 

> On May 27, 2021, at 1:17 AM, NW Mailing List <nw-mailing-list at nwhs.org> wrote:
> 
> 
> While on vacation on in AZ, we were paralleling some rails from Winslow to Flagstaff.  Knowing that water boils at a lower temperature at a relatively lower pressure, how did this principal apply to the operation and performance of a steam engine operating in lower pressure altitudes (higher elevations)?
> 
> Christopher J. Bunsey
> 
> 
> 
> 

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