What's Wrong With This Joke was TandemSpeed Limit 2154

alt.folklore.computers

(posted to afc only - my isp is objecting to sci.optics)

For simple arithmetic, whatever you do, any real (irreversible) heat engine can't be more efficient than a Carnot cycle machine running between the same temperatures. Effy = (Thot-Tcold)-Thot (T in degrees K or R). With a bit of math, you can derive the theoretical efficiency for any cycle, for the gas turbine it's effy=1-T1(T4-T1-1)-(T2(T3-T2-1), and with a bit of manipulation it turns out to depend on the pressure ratio and specific heats ratio.(not that you can do much about Cp-Cv if using air as the working fluid.)

For gas turbines, GE is claiming 45% for a 100MW industrial with intercooler. RR has 42% for the Industrial Trent with water injection. 30% for ye olde RR Industrial Avon, 41% for a Mirrlees 15" bore diesel of similar vintage and about half the Avon's power.

My PPOE just couldn't resist the temptation to build a gas turbine loco in 1960. (before my time there.) It used an EM27 (2700hp) industrial turbine with direct gear drive to 6-coupled wheels. It was not one of their more successful projects. :) I never did find out if it had a reverse gear.

Regards,

David P.