New model extends MHI’s established range of turbochargers
Mitsubishi Heavy Industries (MHI) of Japan has added a new frame size to its turbocharger range with the launch of the MET37MB. Designed to fit between the MET33MB and MET42MB products, this provides a more optimised capacity for engines such as the WinGD in-line X35-B and X40-B series. It is also well matched to the Japan Engine Corporation (J-ENG) 6UEC33LSE-C2 engine, which has now seen its first delivery with a commercial selective catalytic reduction (SCR) system. The engine will provide the propulsion for a 600 TEU container vessel built by Taizhou Kouan Shipbuilding.
Originally developed in 2008, the MET-MB series is now available in 10 frame sizes. MET turbochargers now claim the world’s largest market share for two-stroke marine engines and maintain an excellent reputation with both shipowners and operators. In support of this, MHI announced in January of this year that its production of MET-MB series turbochargers had passed the 2,000-unit level. Shortly afterwards, this was followed by the news that over 15,000 radial type MET turbochargers had been produced, following steadily-increasing levels of production to over 1,000 units per annum in recent years.
In response to demands for increased energy efficiency, MHI has also developed hybrid turbocharger technology, working in association with Calnetix Technologies of California, USA. A high-speed permanent magnet electric generator, integrated into the turbocharger construction, enables electrical power to be generated from the engine exhaust. This is often sufficient to satisfy ship power requirements without the operation of an auxiliary generating set, significantly reducing operating costs. The Calnetix Magnaforce generator is housed within the turbocharger air inlet silencer, resulting in the total package length being only 313 mm greater than for a standard MET-MB turbocharger.
When the engine is running at full load, the generator can deliver electrical power up to the equivalent of 5% of the main engine power output. Furthermore, when the vessel is slow-steaming, the generator can act as a motor to boost the turbocharger’s speed, enhancing engine performance and reducing fuel consumption. The hybrid unit is fully controlled through state-of-the-art power electronics, which connect the generator to the ship’s grid and manages both power-out and power-in modes. Hybrid technology is currently available as an option for seven MET-MB series turbocharger frame sizes.
An alternative solution for slow-steaming is the adoption of an MHI variable turbine inlet (VTI) turbocharger, to maximise turbocharger efficiency at low load conditions. Using the VTI system, the area of the nozzle throat can be narrowed to increase boost and improve fuel efficiency by 2-3 g/kWh. Compared with a turbocharger cut-out arrangement, VTI offers a simple, reliable and flexible solution for increasing the scavenge air pressure of two-stroke engines during partial-load operation, improving the engine’s fuel efficiency.
The VTI mechanism switches the nozzle between two conditions, based on the addition of a ring to divide the nozzle into inner and outer sections. By closing a valve on the inlet casing, flow to the inner ring is shut off, effectively reducing the nozzle area. A simple construction, however, is retained and the MET turbocharger construction also allows turbine blades and nozzle to be inspected and cleaned by removing only the inner section of the turbine inlet casing. This reduces the time and effort required for inspection and maintenance, therefore cutting in-service costs.
VTI is available on the seven largest products in the MET-MB series, with the largest frame size able to deliver a maximum airflow of 65.8 kg/sec at 3.5:1 pressure ratio, or 64.2 kg/sec at 4.2:1. These products can also be equipped with MHI’s integrated exhaust gas bypass system, which can be provided as a retrofit kit for existing applications if required. Further products in the MHI portfolio include MET-MA, MRC and MRII Series turbochargers, with information available on the MHI website.