Auxiliary blower

An auxiliary blower is an electrically driven fan that supplies scavenge air to a two-stroke engine at low load and during starting, when exhaust energy is too weak to spin the turbocharger fast enough. Engines carry two blowers that start automatically on low scavenge pressure and cut out once the turbocharger compressor takes over, usually above about 10 to 30 percent load, with non-return flaps then sealing the blower branches. Without them a large crosshead engine could not start or maneuver, because combustion needs scavenge air the turbocharger cannot yet produce. They draw from the engine room switchboard and are sized in the tens of kilowatts.