Is the torque at stall why steam engines hung on in locomotives long after disappearing from anything but stationary applications? Were they the last of the reciprocating steam engines? My memories of the 40’s are hazy, but I can’t think of any thing else moving under steam power then or since. They aren’t still building steam calliopes are they? Steam shovels and steam rollers were diesel by then weren’t they or electric?
Wikipedia says marine steam engines (reciprocating engines) saw “their last years of large-scale manufacture during World War II.” The WWII Liberty ships had triple-expansion reciprocating engines, for example.
I guess I forgot about marine applications. Everything is turbines now aren’t they? In the 40’s I lived in Western Pennsylvania far from the ocean in a town where the larges employer was a diesel engine factory. I vaguely remember there being few diesel locomotives. Then in the 50’s on a visit to Erie being surprised to the the Nickle Plate RR still running steam engines.
NO everything is diesels. Higher efficiencies.
The Liberties were recips because they could be made faster. In the early war years theturbines t were put in warships because of the time to make the gears. The Victory ships were all geared turbine.
There is a proposal to build “duel mode” locomotives in the UK. The idea is that when “running under the wires” they will act as an electric locomotive, drawing current externally. Then when the train reaches the end of this overhead wiring, an on-board diesel engine would start up to complete the journey. They would be used on such journeys as London to Inverness. This route is only electrified as far as Edinburgh.
Critics point out that for most of the journey the locomotive would be hauling a very heavy lump of metal, in the form of the diesel engine, increasing the electricity consumption. Also you end up with a much more complicated piece of kit. A much simpler solution is to just to attach a diesel locomotive on to the train in Edinburgh and complete the journey that way. In fact that happens already on some routes without any problems.
I don’t know which is more efficient - diesel engine or gas turbine - but I will note that gas turbines are prevalent in many large, late-model US Navy vessels (and I’m not talking about nuclear-powered aircraft carriers, which run on steam turbines). Example here, the USS Michael Murphy.
There is a huge difference between a gas turbine and a steam turbine. A steam turbine is run off boilers, and is a technological replacement for a steam engine. A gas turbine is a modified jet airplane engine. They have huge power to weight ratios and utterly appalling efficiency. So bad that use of them on military ships is usually measured in hours, versus the weeks that a steam turbine or diesel will run for. (To be fair, this low run time is also because they are producing a jaw dropping amount of power in that short period, utterly eclipsing the main power unit.) A ship sized diesel is about the most efficient engine we know how to make with efficiencies around the 50% mark. A steam turbine can get into the 40’s, especially with condensers capable of essentially running the back end of the turbine into a vacuum, but nothing beats the thermal efficiency you get with the high combustion temperature of a diesel.
I think it is a toss. Not all new ships are diesel some are gas turbine, you are right.
This sort of setup is, or was, used for passenger-train locomotives going to/from New York City and IIRC a few other major metropolises, where terminals were within the central city (Grand Central and Penn Stations, for example) and entraining occurred below grade. The locomotive(s) would run “under the wires” until exiting the tunnels outside the city, then engage Diesel engines to provide the power for the long surface runs. Does Amtrak still do this?
Yes, but they use third rai into Penn Station instead of overhead (Empire Routing):Amtrak GE P32-Dual Modes
The dual mode buses are gone from Seattle, replaced with regenerative diesel-electric hybrids. Part of the reason why they used them in the first place was because they had to run on electric power in the bus tunnel, but since they ran the light rail through the tunnel, the overhead wires are no longer compatible with the buses.
Supposedly the hybrid buses are cheaper to operate even though they don’t have the full-electric mode and are clean enough to run in the tunnel on diesel power, but some folks are skeptical of those claims and/or just miss the trolley buses.