Example of two performance maps available for manual selection via the control system on a common rail engine with ECOMAP capability.

“We have the most powerful, proven dual-fuel engine on the market, the 51/60,” said Sokrates Tolgos, responsible for sales to the cruise and ferry market for MAN Diesel & Turbo. He told Cruise Industry News that the dual fuel engine is based on the 48/60 series, but has a larger bore. Generating 1,000 kW per cylinder, it is already employed in LNG carriers.

“The first dual-fuel electric powerplant was delivered in 2010. We now have installations on several LNG carriers and almost four hundred thousand hours of marine field experience with that engine,” he added.

Meanwhile, MAN is also focused on optimizing its diesel engines. “We provide our engines with a full common rail electronic injection system and, since the middle of this year, with the ECOMAP function,” Tolgos explained. “This means that as a conventional engine has standard fuel consumption and power output characteristics at 85 percent load, we can program a common rail engine to operate along different performance curves having their optimum efficiency at different load points. This offers owners a huge potential for fuel savings in combination with an intelligent power management system, enabling the engines to run around optimal efficiency points regardless of the power requirements.”

He said engines with ECOMAP capability have already been ordered by Carnival Cruise Line and Star Cruises. The system is available for the company’s medium-speed, four-stroke 48/60 CR and 32/44 CR series engines. The 48/60 common rail series is suitable for cruise ships typically above 100,000 gross tons whereas the 32/44 common rail series is for smaller vessels. An ECOMAP version has also been ordered for a ro-ro vessel.                

Tolgos added: “The ECOMAP has been described as break-through by cruise line executives looking for technology innovation. Also, the competition has acknowledged this achievement.”

Other technologies available to improve fuel consumption for four-stroke engines include two-stage turbocharging, which will be offered very soon, according to Tolgos. Up to this point, MAN diesel engines have been offered with single-stage turbocharging. “When we go into Tier III requirements, there is another aspect to fuel savings we cannot forget,” Tolgos said. “When engines are run in combination with SCRs, it is not so much the fuel consumption of the engine as such that matters, but the fuel consumption the engine can provide in combination with the catalyst. The catalyst needs a certain exhaust gas temperature to operate, but if you get too efficient, the exhaust gas temperature gets too low for the catalyst to work properly,” he explained.

Thus, MAN has been pursuing its own catalyst development. “We have taken a lot of in-house experience from the automotive sector as we belong to the Volkswagen Group. The basic technology is in many respects is the same for automotive or marine applications, only our engines are bigger. We have developed intelligent methods for how we can combine engines with our own SCR and minimize the adverse impact on system efficiency.           

“When considering Tier III compliance, you should not only look at the fuel consumption of the engine itself, but what the engine can do in combination with the catalyst. So in the end it is the system that counts not just the engine,” Tolgos added.

He is also a believer in powerplants consisting of larger and smaller engines. “If a vessel ramps up the power, a combination of big and small engines gives you more possible options and keeps them at a load point closer to their optimum. “Maybe the power requirement for a ship is such that you can have two 12 cylinder and two eight cylinder engines, meaning you can shut down an eight and start a 12 when you need more power. If you have all the same engines, you have nothing in between, and less possibility to match a vessel’s power requirement in an optimal way.”

Deciding factors in determining how much power will be needed include the cruise product itself and the vessel size. According to Tolgos, for a cruise ship around 100,000 tons, there is no need for five engines, it can cope very well with four engines, compared to for instance 170,000 tons which may need five or six engines. He said it all depends on the owner’s philosophy.

“In general the trend is toward a higher specific power output from the engines,” he said, “which is a result of making engines more attractive cost-wise. More specific power means lower initial cost for the owner. It is not that the power requirements go up, it is more driven by cost aspects. At the same time, one must not compromise on the reliability of the engines.”

In addition to Carnival and Star, current MAN orders also include another Norwegian Breakaway-plus vessel. All the Breakaway-class ships have MAN engines.