The two types of supercharging processes, either with turbocharger or with mechanically driven compressor are the two systems known to be used on diesel engines for submarines. Each of these two systems has its own limitations.
A two stage supercharging system has been investigated and developed by S.E.M.T. Pielstick. This system is based on a turbocharger used as a low-pressure stage combined with a high-pressure stage compressor which is mechanically driven by the engine.
Test bench results are compared with those obtained with the classical systems.
The new system with two-stage compression has an advantage particularly for the following main points:
- specific power,
- air and fuel specific consumptions,
- capability to sustain high exhaust back pressures as well as low suction pressures and low sensitivity to their fluctuations,
- safety against engine stalling in case of loss of submersion control.