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MHI turbocharger combines electric-assist and variable turbine functionality

5 June 2014

Mitsubishi Heavy Industries (MHI) announced a successful sea trial of the world’s first hybrid turbocharger that combines the electric-assist function with variable turbine geometry.

The MET66MAG-VTI turbocharger was tested onboard of a vessel that ran its sea trial from April 17th to 22nd and proved the world's first electric-assist turbocharger function on actual ship, said MHI. The turbocharger was manufactured by Mitsubishi Heavy Industries Marine Machinery & Engine Co., Ltd. (MHI-MME).

This ship is a car carrier built by Shin Kurushima Dockyard Co., Ltd. The ship operator has decided to adopt the same MET66MAG-VTI turbocharger to its next two car carriers. In total, MHI-MME has received orders for six units of the new turbocharger.

By using the electric-assist function, the ship should be able to save energy consumption at slow steaming, by reducing the amount of time of auxiliary blower operation. During slow steaming, a separate auxiliary blower is typically necessary for assisting the turbocharger rotation. The electric-assist turbocharger incorporates an electric motor that assists the driving of the turbocharger, reducing the operation cost for low load operation of the engine.

The turbocharger combines the electric-assist with the function of electric generation as a hybrid turbocharger and with that of variable turbine inlet (VTI). By utilizing the exhaust gas waste energy, the hybrid turbocharger can provides up to 5% of the main engine output—according to MHI—further reducing the ship fuel consumption.

The variable turbine inlet features a special nozzle ring which is cylindrically divided into outer and inner part. The gas passage to the inner part has a control valve which shuts off gas flow into it. The system is integrated with the gas inlet casing, which enables two-step variation of the turbine capacity, enabling flexible turbocharger operation, especially at low load.

The VTI, as described by MHI, seems to have some similarities (though it doesn’t appear to be identical) to the variable flow turbine depicted in Figure 24 of the DieselNet VGT paper.

The VTI package is also available as a retrofit.

Source: Mitsubishi Heavy Industries