<b>Turbines</b> The use of turbines to generate power in shipbuilding is not new. In the past it was usually steam turbines, today gas turbines are mainly used for the main propulsion. These are similar to those in aircraft construction. The turbine system is a fluid flow machine with a rotating drive part (rotor) to convert the energy of a flowing medium into mechanical energy. Fluid flows through it in the axial direction, which transfers its energy to the rotor. The speeds are in the range of around 3500 rpm. In many cases, gas turbines are also used in conjunction with diesel engines as a combined drive or as an energy generator to drive a generator that supplies the required voltage for an electric drive motor. In principle, the ship's turbine system is the series connection of two fluid energy machines, namely the compressor and the turbine: The air sucked in from the open space is pre-compressed in the compressor part, preheated and fed to the combustion chamber, in which the injected fuel is burned. For this purpose, the combustion air must be driven at a higher pressure than the combustion pressure in the combustion chamber. This is done using a multi-stage compressor that is driven by the turbine itself. The combustion chamber itself is not arranged radially around the rotor between the compressor and expansion part (as in jet engines in aircraft construction); ship's gas turbines have an external combustion chamber with gas lines from the compressor and to the expansion part (the actual turbine). Here, the exhaust gas is then expanded, releasing energy to the rotor. In the generator, the useful work of the process is converted into electrical energy for the drive motor. To achieve high levels of efficiency, the heat from the exhaust gas is transferred via a recuperator to the colder air coming from the compressor before it is fed to the combustion chamber.