Shipping is an eco-friendly transport method. But it is also responsible for a large part of global emissions of toxic (NOX)gases.
Great efforts are therefore being made globally to reduce these emissions. A DTU researcher has developed a new software that can make shipping greener by limiting emissions of both black smoke and NOx gases.
Internal combustion engines in cars, lorries, and ships emit polluting gases, including NOx, to the surroundings.
NOx is a generic term for a number of gases, of which especially nitrogen dioxide (NO2) is toxic to inhale.
The rules on emission of NOx from ships have been made more rigorous 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. There is thus constant pressure to find technologies which can reduce NOx emissions further.
Exhaust Gas Recirculation (EGR)—in which part of the exhaust gas is recirculated to the engine—is one of the technologies that is already being used to reduce NOx emissions. During the development of EGR for marine engines, there was an unfortunate side effect with formation of large quantities of black smoke in connection with forceful accelerations of the ship.
This does not exactly reduce air pollution, and the smoke may also damage the engine, explains Casper Hededal Svendsen, Head of Emission Control at MAN Diesel & Turbo.
“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,” he says.
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 our other development activities, and we therefore decided to enter into industrial PhD collaboration with DTU to see whether that could bring us a step further,” says Casper Hededal Svendsen about the establishment of cooperation with PhD student Kræn Vodder Busk at DTU Electrical Engineering.
Black smoke can be avoided
The cooperation involved not only DTU Electrical Engineering—where researchers have extensive knowledge about automation and control—but also Linköping University, which has experts in engines for cars and trucks. This research served as inspiration for Kræn Vodder Busk.
“However, marine engines are very different. Sometimes they are two-stroke engines and not four-stroke engines, so it was not possible simply to copy the approach from car engines. I focused instead on developing a new method that is better suited to marine engines,” he explains.
If the EGR technology is to work properly, it is essential that there is quick regulation of the supply of oxygen to the engine when the ship accelerates. If the oxygen is supplied too slowly, the fuel is not combusted efficiently, resulting in black smoke.
Relatively early in the PhD process, Kræn Vodder Busk sailed on a large container ship to get a sense of how his research could 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—i.e. the oxygen level in the intake of the engine—that we wanted to improve.
Kræn Vodder Busk succeeded in developing a new software which can regulate the oxygen level under forceful acceleration. This creates the best conditions for effective fuel combustion in ship engines.
The technology was tested on several marine engines during the project, and it quickly turned out that the technology worked, so that formation of both black smoke and NOx was avoided, without this negatively affecting the manoeuvrability of the ship.
Kræn Vodder Busk is today employed as a development engineer with MAN Diesel & Turbo, where he is working to implement the new software in the company’s ship engines.