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Reply to "Question for the Steam Experts"

smd4 posted:
MELGAR posted:
TM Terry posted:
MELGAR posted:

 

 The boiler and reciprocating expander (engine) ran at a steam pressure of 1600 PSI and a superheated steam temperature of 1600 deg-F - both much higher than anything ever contemplated in a steam locomotive. The high temperature was needed for thermal efficiency (fuel economy) and the high pressure allowed the engine to be compact. 

MELGAR

Could you explain further where your 1600 degrees F is used?

Boiler produced superheated steam at 1600 deg-F, 1600 psi. This was the working fluid supplied to the reciprocating expander which admitted steam through sequential poppet valves and exhausted through ports into a condenser. I did thermodynamic analysis but not metallurgy... Ceramic pistons and cylinder liners were considered as a means of further increasing efficiency.

MELGAR

I'm not sure where you're getting these numbers.

I don't have high-pressure steam experience, but I doubt the pressure and temperature would be the same number. Indeed, in an on-line steam calculator, if I plug in a pressure of 1600 psig, the calculator tells me the temperature would be 606 degrees F.

I shall answer your question and then end my part in this discussion since thermodynamics is not the subject of this thread.

The temperature you have determined (606 deg-F) is the saturation temperature of water at a pressure of 1600 psia. This means that if water is pressurized to 1600 psia, it will change state from liquid (water) to vapor (steam) when heated to 606 deg-F. It can then be heated further (superheated) in the vapor state, to 1600 deg-F, as was done for this engine. Thus, the steam had 994 deg-F of superheat. 

ASME Steam Tables (5th Edition) show steam properties only up to 1500 deg-F, so they are not sufficient in this case.

“Engineering Thermodynamics” by J.B. Jones and G.A. Hawkins lists properties (Table A-1.3E page 752) for superheated steam at 1600 deg-F and pressures of 1500 psia and 1750 psia. Linear interpolation of the Table values gives the following thermodynamic properties of steam at 1600 deg-F, 1600 psia:

  • Specific volume = 0.7597 cubic-feet per pound mass
  • Specific Internal Energy = 1619.0 Btu per pound mass
  • Specific Enthalpy = 1842.6 Btu per pound mass
  • Specific Entropy = 1.7958 Btu per pound mass per deg-F

I worked on this project and analyzed the thermodynamics of this steam engine for three years. End of discussion for me.

MELGAR

Last edited by MELGAR

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