Reducing diesel engine emissions

Turbocharging technology

The application of two-stage turbocharging technology on Wärtsilä diesel engines has been developed through close cooperation between Wärtsilä and ABB Turbo Systems. Wärtsilä is focusing on developing advanced engine technology which, with the turbocharger, is able to reach the highest possible performance and become a cost-effective commercial solution. ABB Turbo Systems is delivering the turbocharging technology with defined performance in terms of airflow, pressure ratios and efficiency.

In the new engine design, two turbochargers are arranged in series to generate increased air pressure, airflow and a good turbocharging effect. This results in an efficiency rating of up to 76%. The increased air pressure, combined with the advanced engine technology, improves the engine output and power density by up to 10%. At the same time, both fuel consumption and CO₂ emissions are reduced.

Further emissions reduction can be achieved with additional engine systems or by the use of exhaust gas after-treatment. A precise combination of fuel consumption levels and reductions in CO₂ and NO_x emissions can be selected through detailed systems configuration. Intelligent engine control allows optimum operation of the advanced engine design over the whole load range, and a significant reduction in NO_x emissions can be reached.

At high altitudes, two-stage turbocharging technology ensures the engine’s operational performance by compensating for the reduced air density. The significant reductions in fuel consumption and emissions are the result of extensive joint testing of the two-stage turbocharging system on the Wärtsilä engine. The tests have taken place at Wärtsilä’s test facility in Vaasa, Finland, and the targets for the development program have been successfully met. Wärtsilä and ABB Turbo Systems are planning to initiate a major pilot project with a customer in the near future.

Another driving factor in this development work has been to significantly lower life cycle costs, and this target has been met. So, too, has the goal of lowering NO_x emissions. The market potential for this technology in power plants is believed to be big. Similarly, the advanced technology for combustion control developed by Wärtsilä will be beneficial to the shipping market, when the market requirements are in place. Here, in addition to costs, the compactness and cost-effective design are considered to be of importance. Calculations indicate that in certain power plant applications the investment in advanced two-stage engine technology could be regained in less than two years of operation.

“The conceptual design for the new power plant engine began three years ago,” says Mikael Troberg. “Testing of the concept, and verification of the technology, has been successfully carried out using four-stroke Wärtsilä 20 and Wärtsilä 32 engines. We see this technology as being a key for the next generation of Wärtsilä emissions-friendly engines. The technology has been developed for the four-stroke portfolio, in both marine and power plant applications. The next logical step is the two-stroke engine family for large vessels, typically as single-engine installations.”