Clean marine engine

2 min read

Finnish marine propulsion giant Wärtsilä has unveiled a shipping engine that it claims will offer improved reliability, reduced maintenance, greater fuel efficiency and lower emissions.

The RTX-4 full-scale, low-speed research engine is being tested in a rig more than 5m high at the company's Diesel Technology Centre in Winterhur, Switzerland.

The set-up has been designed so additional components and technologies can easily be fitted to assess their effectiveness. This will include sophisticated exhaust cleaning components such as particulate filters and air scrubbers.

The development of new efficient marine engines is important as the world's shipping fleet now carries 90 per cent of international freight, producing an estimated 1.21bn tonnes of emissions a year, which makes up 4.5 per cent of global totals.

Part of the drive for lower-emission shipping engines stems from stringent local regulations such as those put in place by the US Environmental Protection Agency, which will significantly reduce the allowable output of particulate matter and nitrogen oxides (NOx).

To achieve these targets, the engine has an exhaust gas after-treatment plant that includes a selective catalytic reaction unit. This set-up can reduce the NOx content of exhaust gases by more than 90 per cent compared with the level at the engine outlet, while also significantly reducing CO2 levels.

Another advantage of the flexible engine design is that it can be run on any type of heavy fuel oil now used for shipping. It will also be tested for its ability to burn lower grades of fuel that may need to be used in the future.

Wärtsilä manufactured the RTX-4 research engine in co-operation with Croatian company 3 Maj Shipbuilding Industry. It is a four-cylinder, low-speed, two-stroke engine with a 600mm cylinder bore capable of producing 10,160kW of power at a nominal speed of 114rpm. The adaptable design of the engine means the power output can be increased in future for ships that need it.

The engine uses Wärtsilä's RT-flex common-rail (a diesel direct-fuel-injection system) technology that has integrated fully-electronic control of all engine processes, including fuel injection, exhaust valve operation, cylinder lubrication and air starting.

Standard Wärtsilä RTA low-speed engines have a mechanical camshaft, gear drive, fuel injection pump units and mechanical control gear but use electronically-controlled common-rail systems.

The initial test programme will validate the design of the engine and optimise its thermodynamic properties. Wärtsilä will then use the RTX-4 for ongoing research into efficiency, emission reduction technologies, ease of manufacturing and lowering maintenance costs, to inform future designs.

The Diesel Technology Centre is Wärtsilä's centre of excellence for low-speed, two-stroke marine diesel engines. The company uses it to trial technical improvements and changes to production engines and to verify new designs before field testing and commercial application.

Test engines are run at much higher loads than production engines to identify risks quickly and discover any design limitations before moving to the next production stage.

During tests on the RTX-4, researchers can monitor and control the ancillary systems and the dynamometer from a dedicated control room via an integrated marine automation platform.

The sophisticated test environment takes 100 measurements/sec over more than 1,000 channels with interfaces to the emission measurement systems and a telemetry system for temperature measurement. There is also a dynamic measurement system with a data exchange interface to the automation platform, which can take up to 36,000 individual measurements over each engine revolution.

Berenice Baker