The rules on emission of NOx from ships have been tightened in recent years. Since 2016, there has been a requirement in North America to reduce emissions from large two-stroke diesel engines on new vessels by 75 per cent and in a few years, the same reduction will also be a requirement in the North Sea and the Baltic Sea.
“EGR technology is one way of reducing NOx emissions. However, the regulator for the EGR technology meant that black smoke was created in connection with rapid acceleration of the ship, which is undesirable and can damage the engine. The black smoke could be removed by manoeuvring ships differently, but we wanted to maintain the current sailing properties and solve the problem in a different way instead,” explains Head of Emission Control, Casper Hededal Svendsen, MAN Diesel Turbo.
Initially, the company tried conventional approaches, but, as this did not work, they decided they needed external assistance to meet the challenge.
“We found that there was a need for greater use of advanced technology. It was difficult to align the task with the other development tasks, and we therefore decided to enter into a business PhD collaboration with DTU to see whether that would help us proceed.”
Development of new state-of-the-art technology
The cooperation involved not only DTU Electrical Engineering who possess extensive knowledge about automation and control, but also Linköping University, who are experts in engines for cars and trucks. This research served as inspiration for PhD student Kræn Vodder Nielsen.
“However, marine engines are very different. Sometimes they are two-stroke engines and not four-stroke engines, so it was not possible to just copy the approach from car engines. I focused instead on developing a new method that is better suited to marine engines,” explains Kræn Vodder Nielsen.
MAN Diesel Turbo uses EGR technology, in which part of the exhaust gas is recirculated to the engine to limit NOxemissions. It is crucial in this context that the recirculation take place with the right quantity of exhaust so that enough is recirculated to reduce the formation of NOx and there is sufficient oxygen to combust the fuel – thus preventing black smoke when the ship accelerates or slows down.
Relatively early in the PhD process, Kræn Vodder Nielsen sailed on a large container ship to get a sense of how his research would ultimately be used.
“I found out that the academic methods for development of the control of a marine engine with EGR technology at that time were too complex. Therefore, it quickly became clear to me that I had to develop a simple model that includes only the critical part of the system that we wanted to improve. From there, we developed a new control that coordinates the recirculation and fuel injection without requiring too much tuning of other parts of the system,” explains Kræn Vodder Nielsen.
Kræn Vodder Nielsen succeeded in developing new state-of-the-art control technology, which was tested on a couple of marine engines during the project. This quickly showed that it worked, avoiding the formation of black smoke without affecting the vessel’s manoeuvrability.
Kræn is now employed by MAN Diesel Turbo, where he is helping finalise his software so that, from the end of the year, it can be implemented in new marine engines.
“Initially, I will go out and install it on the ships, but in the long term the plan is that I will write a guide so that shipbuilders and crews can fine-tune the system themselves,” explains Kræn.