A useful hint on types of supercharging for the main and auxiliary diesel engines.
1. Supercharging with a constant partition of gases at the turbine inlet, p = const. It is used in the main engines, mainly operating under constant load, but it is also found in the auxiliary diesel engines (electric ships). The advantage is in the simplicity of design; the lack is weak efficiency at light loads.
2. Pulse supercharging – is found in the main and auxiliary diesel engines. At start-up and variable loads due to strong fluctuations in pressure a large amount of energy is fed on the blades of the turbine. The systems may be of two-, three-, four-pulse. I’d like to note that the two-pulse system is almost not found in modern engines. The system is not suitable if the supercharging pressure is above 2.5 bar. Also the use of the two-pulse system involves the installation of nozzle holes in the cross-section of the exhaust pipe, which sometimes leads to vibration of the turbocharger.
3. Combined supercharging or modular “SPEX” – is an aggregate of pulse supercharging and supercharging at a constant pressure. The volume of the exhaust-gas receiver is substantially less than in the system of p = const. Exhaust pulses move tangentially and movement of gas along the receiver acquires a rotational motion. The advantage of the system is in the simplicity of its installation and maintenance compared to other pulse systems. The modular system is also known as Modular Pulse Converter, MPC (Pielstick), Single Exhaust Line (Sulzer).