[steamer_ctn]

Hi Dave,

Genma Saotome, on 28 January 2015 - 10:18 AM, said:

Well.. a very nice discover: Johnson's Steam Locomotive (1945) has been digitized and given full view. Feedwater discussion begins on page 101.

Thanks for that.

Looks like a good reference book.

I will think about how to include a representation of feedwater heating, though it will probably be while, as there a few other things on the list.

[Lindsayts]

A couple of random points in for the discussion.....

Injectors heat the feed water, the heat comming from the steam supply thats doing the injecting.

Another way of doing feed water heating using waste steam is exhaust steam injectors data from the UK hall class boiler table......

Live steam injector, boiier at 22,000 lbs / hour, coal consumption 3760 lbs/hr

Exhaust steam injector, boiler at 22,040 lbs/hour, coal consumption 2690 lbs/hr



You cannot raise water temperature above boiling point UNLESS the water is under pressure



Figures I have for locomotive boiler effieciences show they usually run around 75 percent efficeint. Boilers in power stations usually run in the 85% or higher category.



Most locomotives boilers can be pushed, ie loco boilers do not have a fixed output.
At high steaming rates its possible to push much more air through the fire and burn more fuel. The usual limit being the maximum fuel temperature.
It being easily possible to get the flue temperature so high these can damage the boiler. The damage will usually be leaks or cracks in the tube plate caused by the pressure of the high temperature flues expanding length wise.
Needless to say such damage these days is not well liked by locomotive maintenence people, who have spent many thousands of hours caring for theses machines and of course do NOT like crews vandalising the locos that way.

Because of this ability for crews to push boilers in the end the amount of power one can get out of a steamer depends totally on how much the railway will spend on the maintence budget.
It usually being possible to get 30 to 40 percent more power out of the machine than the designers intended, one sadish point is that the locos DO sound good when being pushed so hard.

LIndsay

[Genma Saotome]

Lindsayts, on 28 January 2015 - 12:36 PM, said:

At high steaming rates its possible to push much more air through the fire and burn more fuel. The usual limit being the maximum fuel temperature.

The Johnson book -- a must have reference book for sure -- mentions the air speed in a stationary boiler is often around 10mph whereas in a locomotive it is often several hundred mph. He then observes in the later case it was not unusual for a particle of unburnt fuel to pass thru the tubes in a tiny fraction of a second... potential heat energy lost forever. The problem became worse as train speeds increased in the early 20th century and the design solution was to increase the size of the grate area so as to increase the odds the particle would be burned before entering the tubes.

And so "modern" steam locomotives not only produced more steam by virtue of having a larger firebox they tended to make better use of the fuel that was put into the firebox.