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Solution for Slow Steaming ― MHI-MME's VTI Turbocharger maximizes and optimizes efficiency during slow steaming under a low load


VTI Turbocharger

We have developed a variable turbine inlet (VTI) turbocharger that maximizes and optimizes efficiency while slow steaming under a low load.

By installing a variable turbine nozzle in the exhaust gas inlet area, the size of the nozzle throat is narrowed to improve fuel efficiency by 2 to 3 g/kWh.

Because the structure of the VTI Turbocharger is simple, we are able to maintain high reliability while achieving low cost and easy maintenance.

Background and Details

Streamlined operation - Turbocharger cut-out

The volatile oil price has forced many shipping companies to run their ships at slower speeds. One of the methods used to implement slow steaming is turbocharger cut-out. This allows an engine equipped with several turbochargers to stop a single turbocharger during partial load operation. For example, when one of four turbochargers is stopped, exhaust gas is distributed to the remaining three turbochargers, which increases the scavenging air pressure and improves fuel efficiency.

By installing panel sheeting at the air outlet and an exhaust gas inlet, turbocharger cut-out can be achieved without the need to extract the rotor. Furthermore, as lubricating oil continues to be supplied to the offline turbocharger during cut-out, there is no impact on the bearings.

Usually, turbochargers generate their own sealing air to prevent the leakage of oil. When turbocharger cut-out is implemented, however, the offline turbocharger no longer generates this sealing air. To prevent oil leaks in the offline turbocharger, we have redesigned the seal on the turbocharger's compressor to enable sealing air to continue to be supplied from the online turbochargers. When returning to high-load operation and bringing all turbochargers back online, the seal can be restored to its normal condition by simply removing the blind flange.

Streamlined operation - VTI Turbocharger

Turbocharger cut-out is an operational measure and slow steaming can also be achieved through hardware streamlining. In response to ship owners' requests for higher fuel efficiency, we took a fresh look at our product development to incorporate a variety of solutions and new ideas.

These efforts resulted in the development of the VTI Turbocharger. Generally speaking, operating an engine at partial load during slow steaming reduces the scavenging air pressure of combustion air thereby lowering fuel economy. Our VTI Turbocharger increases the scavenging air pressure so that the pressure is maintained even during partial load operation, improving the fuel efficiency of the engine.

VTI Turbocharger feature 1: Variable turbine nozzle

Opening and closing nozzle throat

The VTI Turbocharger incorporates a mechanism to switch the nozzle between two stages, enabling an operation similar to that of a turbocharger cut-out. Reducing the nozzle area increases the pressure of the scavenging air being fed to the engine, which reduces the fuel consumption under a low load by about 3 to 5 g/kWh. *1

*1 Value calculated when the VTI Turbocharger is used with 6UEC60LSE-Eco-A2 engine.

VTI Turbocharger feature 2: Simple structure

Structure of VTI Turbocharger

Turbocharger manufacturers today are competing fiercely to develop new products. However, all too often turbochargers have a complex structure that make them difficult and time consuming to maintain, unless the maintenance is carried out by experienced and skilled personnel.

To solve this problem, our VTI Turbocharger features a simple structure, allowing for easy inspection and maintenance work. Conventional turbochargers can also be retrofitted, by simply replacing the gas inlet casing and nozzle, with a gas inlet casing that incorporates a valve and a nozzle designed especially for the VTI. *2

*2 This is possible for MET-MA and MB types.

VTI Turbocharger feature 3: Easy maintenance

Our VTI Turbocharger incorporates a number of new ideas and devices, such as a modified nozzle. A ring was added to the existing nozzle to divide the nozzle into inner and outer sides in order for maintenance work to be performed as easily as before.

Exhaust gas flows from the engine to the casing and this casing also has a unique feature. Turbochargers manufactured by other manufacturers have a turbocharger and casing that are monolithic, meaning that the gas inlet casing and the pipes on the engine side also have to be removed in order to inspect the turbine. The engine becomes especially hot and the casing cannot be removed easily which poses a danger unless handled by expert personnel. With our MET Turbocharger however, the gas inlet casing is divided into two parts, and the turbine blades and nozzle can be inspected and cleaned by removing the inner casing only, facilitating maintenance work. Since our VTI Turbochargers have the same structure as MET Turbochargers, maintenance work can also be performed easily by simply removing the inner casing, reducing the time required to open and inspect the turbocharger and thereby cutting maintenance costs.

With its simple structure, low cost and easy maintenance features, our VTI Turbocharger has been well received by customers, who have noted its simple structure allows for hassle-free maintenance that even the ship's crew can handle, simultaneously praising its strong reliability.

MHI-MME: a strong turbocharger manufacturer

We currently have a market share of around 40% in marine two-stroke engines.

Product reliability is vital to ship owners who of course need ships that are able to operate with as few interruptions as possible. Our track record of a large number of our products in use in the industry attests to the high confidence ship owners have in us.

Our greatest asset is our experience. Thanks to many years of accumulated manufacturing and product development experience, MHI-MME's in-house expertise is second to none and our technologies are at the cutting edge of design.

Successful product development comes from our research team's constant brainstorming, testing, probing and proving their ideas.

Our VTI Turbocharger was a product of exactly this kind of environment.

Strategies for the Future

Everything we do is focused on achieving customer satisfaction and meeting their needs and requirements.

The next goal for MHI-MME turbochargers is to achieve higher performance and larger capacity. This will allow us to develop more compact products, at lower prices, with smaller installation footprints.

We will continue our efforts to further refine solutions that effectively combine our products to meet the real and present need of our customers to increase operational efficiency.