A diesel train is one that has a locomotive run by diesel fuel, in a manner of speaking. Actually the diesel fuel is only part of the equation. Electricity is the other part. In fact, it could be argued that a diesel train could be referred to as an electrical train.
A diesel train works by producing incredible horsepower. In fact, whereas most cars have an engine with, perhaps, 200 horsepower, a diesel engine can produce as much as 3,200 horsepower. It converts this energy into electrical energy, producing up to 560 kilowatts of electrical power. This is converted into thrust.
While the technology exists to run trains on other forms of fuel, diesel trains use diesel simply because it is more fuel efficient than gasoline. A diesel locomotive uses more than one gallon (3.75 liters) of fuel per minute, even just pulling a few cars. Therefore, any fuel efficiencies that can be realized become paramount.
The reason why a diesel train converts its energy to electricity is to remove the need to have a transmission. Cars need transmissions to change the gear ratio as they speed up and slow down because of the way a gasoline engine must be made. When a diesel train converts that to electricity, it is then sent to a motor at each gear which can produce the torque needed at any speed.
The diesel locomotive was invented by Rudolph Diesel, who also invented the diesel engine. It was invented in the 1890s. However, it did not come into widespread use until the 1930s. Today, in many parts of the world, seeing a diesel train is commonplace. The vast majority of trains are run by diesel, though other technologies are also coming into use.
After it started gaining in popularity, the diesel train quickly replaced the steam train for most of the world. However, steam locomotives are still in use in some locations, depending mainly on the technological achievement and wealth in the area. In Western countries, steam locomotives have been mainly relegated to sightseeing tours where the nostalgia of the engine is used to create a certain setting.
A diesel train has a number of advantages over a stream train. The energy conversion is much higher, meaning less wasted energy. It can also be safely operated by one person. Further, the operating environment for the engineer is much more pleasant, without having to constantly worry about the boiler and keeping it at a proper temperature.