02-23-2009, 07:17 AM
There may be some additional regulation - I was recently reading an article on the design of PRR boilers which was really quite interesting. To get to the point, several references were made to air-hole size as one component of how much air is allowed into the grate area for combustion.
I'll have to dig that back up and get some more context. It discussed quite a few items that affect draft - air hole, grate area, the gap between the brick arch and the back wall of the firebox, diameter and number of tubes and flues (as noted by Sumpter), how flues packed with superheating elements affected it's ability to breathe and smoke box design (exhaust nozzle, spark arresting components, diameter of the lower end of the stack, the gap between it and the exhaust nozzle, the stack's internal shape). This is all I can remember at the moment - suffice to say that it added a lot of detail beyond my working level of knowledge about the stephenson steam locomotive.
Matt
I'll have to dig that back up and get some more context. It discussed quite a few items that affect draft - air hole, grate area, the gap between the brick arch and the back wall of the firebox, diameter and number of tubes and flues (as noted by Sumpter), how flues packed with superheating elements affected it's ability to breathe and smoke box design (exhaust nozzle, spark arresting components, diameter of the lower end of the stack, the gap between it and the exhaust nozzle, the stack's internal shape). This is all I can remember at the moment - suffice to say that it added a lot of detail beyond my working level of knowledge about the stephenson steam locomotive.
Matt
Matt Goodman
Columbus, Ohio
Columbus, Ohio