UP Turbines

[Acela026]

In the summer issue of Classic Trains, there were many articles on UP's Turbine locomotives.  One of the articles mentioned that they did not run as well in hot weather.  What was the reason for this? It seens kind of odd, since most engines run better (up to a certain point) in hot weather.

Thanks!

Acela026 

[Captaincog]

I can only speak using my experience with turbochargers, but some principles cross over. Colder air is always better for any engine since this denser air allows for more fuel to be introduced and then more power to be produced. The turbines do not like heat much like a turbocharger or supercharger since there is a limit to the volume of air that can be taken in regardless of density. Most turbocharged engines use intercoolers to cool the intake charge and allow variable rates of boost with computers trying to get obtain optimum power, but once the ambient air temp gets up there power starts to fall off since the heat has expanded the air beyond the limits of the engine/control systems to overcome the heat. So, the turbines simply were not designed for very hot ambient temperatures. Had their development continued, this issue would have been overcome.

[Acela026]

Thank you Captaincog!

[timz]

Acela026

One of the articles mentioned that they did not run as well in hot weather.

It was always known that the turbines themselves (as distinct from the locomotives) could produce more power at lower temperatures. Trains said the big turbines were supposed to be able to produce 8500 hp at... 90 F at 6000 ft altitude as I recall, but if the generators/motors could handle it the turbines themselves could do 10000+ hp in denser air. So maybe that's all the article meant-- they ran fine on hot days, just not as powerfully?