Talk:Steam turbine locomotive
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[edit] Comment on efficiency
There is nothing inherent in turbines which makes condensers essential; it is merely simpler to make a turbine which will blow down to a vacuum than it is a reciprocating engine (there isn't space for triple expansion on a locomotive). The purpose of the condenser is to minimise the minimum cycle temperature to about 30 Centigrade, as opposed to 100 Centigrade corresponding to exhausting to atmosphere.
The reasons for the condenser are traced to the Second Law of Thermodynamics, which shows that maximum efficiency is achieved by maximising the ratio of the highest to lowest temperatures of the cycle. A reciprocating engine and turbine operating between the same temperature source and sink should have similar thermal efficiency.
Loss of efficiency arises because turbine performance is very sensitive to speed, whilst positive displacement engines work well over a wide speed range, and hence are inherently better suited to wheeled transport. Gordon Vigurs 11:36, 29 May 2006 (UTC)
- Why don't you incorporate this into the main article? I think it would make a good addition to the text. --DV8 2XL 11:45, 29 May 2006 (UTC)
- I think the article is fine as it stands. It is a reasonable comment that the poor mechanical efficiency when running away from the optimum operating point needs to be offset by raising the thermal efficiency by using a condenser. I am being a bit pedantic. Gordon Vigurs 07:06, 31 May 2006 (UTC)
