MET turbochargers has introduced a number of updates to its range, which offer increased power from a more compact and durable unit
SMM 2018 was an important occasion for MET turbochargers, which is updating its turbocharger units following the changes that took place within Mitsubishi Heavy Industries group, after the creation in April this year of a new company (J-Eng) to handle the engine-making side of the group's business.
The MET turbocharger line-up currently consists of MET-MA/-MB (axial type) for two-stroke marine propulsion engines and MET-SRC series (radial type) for four-stroke main and generator engines.
At SMM 2018, MET introduced some logical progressions to these turbochargers.
Discussing the development of this product range, Mitsubishi Heavy Industries Marine Machinery & Equipment president Toshiaki Hori noted: "Generally, a new turbocharger has a design cycle lasting three or four years from conception, prototyping, testing and manufacturing.”
There are four main driving forces in turbocharger development: high pressure ratio; a compact unit; high response; and maintainability.
MET team leader and senior engineer in the radial turbocharger division Yushi Ono explained how these elements impact design and development. Higher pressure, explained Mr Ono, was required by those engine manufacturers seeking to meet the demands of emissions regulation. The engine system needs a higher air charge to burn the fuel more completely, to reduce NOx emissions.
The need for physically smaller turbochargers is driven by a desire to reduce the weight of the propulsion unit, which coupled with the smaller size, increases the deadweight capacity of a given vessel.
By shortening the turbocharger’s response time, it should be possible to reduce shock loadings which are a consequence of turbo lag (the time required for the turbocharger to reach an efficient operating level).
Maintainability is a key factor; the capital cost of a turbocharger is relatively insignificant compared to the long-term cost of maintenance. Evolving, rather than radically redesigning, existing units is beneficial as the service network has built up considerable experience and tooling with the current range, which would become redundant if a completely new design emerged.
The mainstay of MET radial turbocharger range is the MET-SR series
Over 15,000 MET-SRC units are in operation and it has a reputation for being easy to maintain and repair, according to Mr Ono. MHI received an order from Hyundai Heavy Industries (HHI) for its MET30SRC radial-type turbochargers to be mounted on its HiMSEN 6H32/40 medium-speed, four-stroke engines. It has already completed delivery of the first of these turbochargers, which are the very first MHI-MME radial turbochargers to be mounted on a HiMSEN engine.
The MET-ER series features a newly designed turbine wheel and a highly efficient impeller. The turbine valve nozzle is coated with a metal spray and the rotor shaft journal induction is hardened. The new series is compatible with heavy oil and no water cooling or air vents are required. The series fits a wide range of diesel engines, from 400-4,400kw.
Noise levels are an issue in machinery spaces and the new unit is equipped with a lightweight silencer, which takes very little energy out of the system. It is interesting to note that MET and Yoshi Ono are listed as having patented a noise reduction system for radial turbochargers.
Mr Ono reported that a very important aspect of the development of the MET-ER series is size, notably that for the same compression and engine requirement, the frame size is reduced. In other words, a smaller MET-ER turbocharger can now be specified over the MET-SR unit that may have previously been required.
A welcome side effect of the more compact frame is that the number of individual parts has reduced by 30%, which will have a long-term effect of maintenance costs.
"There are four main driving forces in turbocharger development: high pressure ratio; a compact unit; high response; and maintainability"
MET axial turbocharger developments for two-stroke engines
MET team leader and senior engineer in the axial turbocharger division Yoshikazu Ito discussed the development of MET’s axial turbocharger range for two-stroke engines. He noted the first units in the early 1960s were capable of producing an air charge of around twice atmospheric pressure (ratio 1:2). The same driving forces of higher pressure, compactness, high response and ease of maintenance impinge on the axial turbocharger side of the business.
MET axial turbochargers are licensed to three major engine manufacturers in Korea, while the MET turbocharger is mounted on two-stroke engines used by Mitsubishi, MAN Energy Solutions and WinGD. MET says its market share among two-stroke marine propulsion engines is around 40%.
In addition, WinGD recently approved the MET turbocharger to be mounted on its dual-fuel X-DF engines. MET66MB turbochargers will sit on two W5X72DF engines manufactured by HHI that will be delivered to Daewoo Shipbuilding & Marine Engineering (DSME) for installation in an 180,000 m3 LNG carrier, commissioned by a shipping company backed by Itochu Corporation and Mitsui O.S.K. Lines, Ltd.
The current iteration of the MET-MB is suitable for heavy oil and a wide range of large marine and stationary engines. Advances in the MET-MBII series include a more aerodynamic turbine design, based on hundreds of hours of tests and analysis, and improvements to reduce noise levels.
The turbocharger has a robust bearing pedestal design and an integrated lubricating oil head tank. To ease maintenance, the design features a detachable gas inlet inner casing.
Yushi Ono (MET): The new development means for the same output a smaller frame can be used, saving weight
With the new compressor design, the MET-MBII offers a 16% increase in air flow and the unit can maintain higher levels of efficiency for longer. This allows customers to specify a smaller turbocharger to cover that same engine output.
The current MET-MB range was increased to 10 frames with the launch of the MET37MB earlier in 2018. Designed to fit between the MET33MB and MET42MB products, it optimises capacity for engines such as the WinGD in-line X35-B and the 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 system. The engine will provide the propulsion for a 600 TEU container vessel built by Taizhou Kouan Shipbuilding.
The MET-MBII retains the 10-frame sizes, but the increase in compression and reduced weight could allow an engine manufacturer to specify up to two drops in frame size.
As it contains fewer components compared to the MET-MB, the MET-MBII is said to produce less noise. Mr Ito declined to specify exactly which components had been changed and how, but it was clear that the turbine wheel had fewer blades than the MET-MB.
The MET-MBII will go on sale in 2019, according to Mr Ito.