Coal Vs Oil

[Erik_Mag]

One could always set up the output of the hydrogen burner to be directly injected into the boiler with a little injected into the dry pipe for superheating...

After all, the ultimate proposed steam engine was the Aerojet M-1 engine that would have been good for 1.5m pounds of thrust.

[Overmod]

Erik_Mag

One could always set up the output of the hydrogen burner to be directly injected into the boiler with a little injected into the dry pipe for superheating...

I don't think I have explained things well enough.  What is desirable in a locomotive's radiant section is a long, luminous flame that does not touch the relatively cold walls enough to quench, and that *just* finishes the combustion causing the luminosity as the plume reaches the rear tubesheet, forward of the chamber.

Hydrogen is almost the antithesis of this: it burns very hot, very promptly, with a transparent flame with peaky spectrum, and while it is high-energy it is so light that a large volume is involved for high mass flow.

You may remember from anthracite discussions that there are problems vaporizing or levitating enough carbon to get the necessary rate of heat release for locomotive firing... at which point some parts of the firing system melt rather than act to transfer heat to steam.  A large hydrogen blowpipe can be expected to cause far more spot overgeating and differential expansion problems, even before we take up cumulative hydrogen embrittlement as a potential structural concern.

Use in separately-fired superheaters of proper design would make better sense, but again the required mass flow makes co-firing with something that optimizes proper heat transfer -- probably some high-carbon liquid -- desirable.  Besler tubes would be advisable, and while you might arrange hydrogen manifolding in them you'd need nanoinsulation inside, as Besler tubes are passive re-radiators.

After all, the ultimate proposed steam engine was the Aerojet M-1 engine that would have been good for 1.5m pounds of thrust.

If the reciprocating engine used hydrogen in internal combustion it would be one thing; if it could use reaction thrust like a glorified M-497 still better.  Unfortunately we're dealing with a practical extended Rankine cycle and heat balance, and rockets do very little good there...

[Erik_Mag]

My somewhat tongue in cheek proposal was that the heat transfer between the steam generated by burning hydrogen and the boiler water would be done by condensation of combustion products directly into the "boiler" water. Think charging up a fireless cooker. The "firebox" would resemble the combustion chamber of a small rocket engine as combustion would need to take place at somewhat above "boiler" pressure.

Makes a lot more sense to use hydrogen in fuel cells...

[Overmod]

Erik_Mag

My somewhat tongue in cheek proposal was that the heat transfer between the steam generated by burning hydrogen and the boiler water would be done by condensation of combustion products directly into the "boiler" water.

It is less tongue-in-cheek than you think: submerged burners are a 'thing' and they could certainly be made to work with stoich air-hydrogen flame.  (Now for true fun you would of course use LH and LOX via turbopumps, with some kind of hypergolic igniter or flameholding -- at appropriate scale of course.  Ouch, I seem to have bitten the tongue that was in my cheek with excitement...

However why bother with all that combustion nonsense and firing up and wasted heat when the Oxford cycle generates 11 molecules of steam at 885 degrees from every molecule of methanol?