Turbocharger systems and strategies are being used to both reduce the installed power on ships and to overcome the acceleration challenges that reduced power requirements can bring

As the energy efficiency challenges on shipping escalate, more sophisticated measures for reducing emissions are coming into play. The turbocharger has a role on both improving engine efficiency and in recovering energy potentially wasted through heat.

Mitsui Engineering & Shipbuilding first developed its turbo hydraulic system (THS) to recover waste heat from turbochargers in 2008. The first engine with THS was delivered in 2014 and the company has since delivered the system for 19 sets of engines.

While many waste heat recovery systems aim to return recovered heat energy in the form of electrical power generation, the idea behind THS is to reduce fuel consumption by assisting engine rotation through the use of hydraulic technology. The main circuit consists of hydraulic pumps connected to the shaft end of the turbocharger by a reduction gear. The high-pressure oil pressurised by the pumps is delivered to a hydraulic motor directly connected to the engine crank shaft. Having driven the motor, the hydraulic oil is then returned to the pumps to be pressurised again.

According to tests on Mitsui’s test engine and at shop trial on commercial engines, THS delivers a fuel oil consumption cut of up to 3% without increasing NOx emissions.

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