Steam doesn’t come out the smokestack of a coal burning steam engine, smoke does. The steam is release at the cylinders.
My bad. So maybe there is a conspiracy on Sodor after all?
After expansion, the spent steam is channeled to the stack, where the venturi effect draws the combustion gases to clear the firebox for fresh air. Next time you see a steam locomotive, watch the stack. It “puffs” when the slide valves release the spent steam. That is also why steam locomotives needed to constantly refill with water, as they only used the steam one, and the water was lost to atmosphere.
white water vapor also is released from the top portion from the relief valve and whistle. I think the confusion relates to how diesel engines emit cleaner emissions which are lighter colored than the heavy, dark smoke from a coal-fired steam train.
“Steam doesn’t come out the smokestack of a coal burning steam engine, smoke does.”
Actually a lot of steam does exhaust through the smokestack. The reason for doing this is to increase the draft. The faster the engine runs, the more steam goes up the stack, the higher the draft, and the hotter the fire.
A positive feedback to make sure the fire draws sufficient air. It’s a design that began with the very first steam locomotives and continued until the demise of steam and the rise of the evil and boring diesel.
There’s a tube called a blastpipe that discharges exhaust steam from the cylinders directly into the smokebox below the stack. More modern locomotives also employ an auxiliary blower that routes steam directly into the smokebox without going through the cylinders, for times when increased draft is needed and the amount of exhaust from the cylinders isn’t sufficient.