A number of vehicles use a diesel-electric powertrain for providing locomotion. A diesel-electric powerplant includes a diesel engine connected to an electrical generator, creating electricity that powers electric traction motors.
This kind of power transmission is used by locomotives (see that article for details), used for pulling or pushing trains. Diesel-electric powerplants have also been used in submarines and surface ships and some land vehicles. In some high-efficiency applications, electrical energy may be stored in rechargeable batteries, in which case these vehicles can be considered as a class of hybrid electric vehicle.
Ships
When the diesel engine was first installed in submarines before the First World War, it revolutionized submarine tactics because its range (or operating time) far surpassed that of the gasoline engine, and the lower volatility fuel meant that fuel and vapors were far less prone to catch fire or explode if they leaked into a submarine cabin. The fuel was also easier to stow. In submarines, the engine is connected to generators to produce electric energy that is stored in batteries for running underwater where oxygen is not available to feed the engines. It had been standard for them to use a driveshaft directly connecting the diesel engine, generator and propellers. There were a variety of clutch mechanisms for various connections as well. However, the long driveshaft has often been a source of trouble, also producing noise and vibration.
Some Soviet submarines had three propellers, and could be used in a variety of ways: each running on its diesel engine; either the central one or the outer two could each be connected to a diesel engine with or without the other propeller running on electric; or the engines could via snorkel be recharging the batteries while the central propeller was quietly running on its electric motor; or all three could be running on electric motors.
The diesel engine performance was critical for a conventional submarine's success. Navies imported and copied successful designs. The Germans had some excellent diesel designs for their U-boats, but they also had some designs which were not so good. The Americans had a similar history; their last diesel engine design was radial in form, its driveshaft axis angled vertically. These designs were subsequently abandoned. Older submarines had to be cut in half through the engine room and proven engines installed in a lengthened hull section to replace the unreliable but space-efficient designed engine. Since the correction, European submarine diesels have shown advances.
Modern diesel-electric submarines don't have a direct connection of the diesel engine to the propeller anymore: The usually single propeller is driven directly by an electric motor. Two or more diesel-generators provide electric energy for loading the batteries and/or driving the electric motor. This mechanically insulates the noisy engine compartment from the outer pressure hull and reduces the acoustic signature of the submarine. Even some nuclear submarines decouple their reactor room this way, e.g. all French classes, like the Rubis and Redoutable and the Chinese Type 093 class, have turbo-electric propulsion.
Submarines
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