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How does hydraulic transmission transfer power in a diesel locomotive?

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diesel engine and precombustion chamber — diesel engine Diesel engine equipped with a precombustion chamber.

In a diesel locomotive, hydraulic transmission functions by using a fluid—typically oil—to transfer power from the engine to the wheels without a direct mechanical connection.12

The system utilizes a centrifugal pump or impeller, which is driven directly by the diesel engine. As the engine rotates the pump, it converts mechanical power into kinetic energy within the oil. This pressurized fluid is then directed against the blades of a turbine, forcing the turbine to rotate and ultimately move the locomotive.2

The efficiency and speed of this power transfer are dynamic: the faster the turbine blades move, the lower the relative speed of the oil impinging upon them, which allows the locomotive to increase its speed. Because there is no rigid mechanical link between the pump and the turbine, this method of transmission effectively prevents the transfer of shocks and vibrations from the track to the engine. This technology is frequently favored for diesel railcars and multiple-unit train-sets due to its smooth operation.21