Swiss marine power company WinGD and Japanese Mitsui E&S DU Co (MESDU) have developed variable compression ratio (VCR) for ships to enable optimal combustion when using multiple fuels.
As informed, the new engine technology will be installed on a vessel powered by an X62DF engine and then rolled out across selected engines of the X-DF engine portfolio.
An engine’s compression ratio is usually a fixed parameter, playing a direct role in power and fuel efficiency.
Because fuels have different ideal compression ratios, in dual-fuel engines designers have had to select which fuel to optimise for. With VCR, the engine adjusts to each fuel’s optimal compression
According to the partners, in trials conducted on a 6X72DF test engine at MESDU’s facilities in Japan, VCR reduced fuel consumption and CO2 emissions by 6% when running on diesel mode.
Although the engine had previously been optimised for gas mode, improvements were also evident when using LNG, with fuel consumption and emissions reduced by 3%.
The improvement was achieved because the engine was originally configured to a compression ratio that favoured LNG while still offering good diesel performance. With VCR, this compromise is no longer required, the companies emphasized.
“This breakthrough, the result of several years of work with MESDU, comes at a crucial time in the maritime industry as operators increasingly look for the ability to switch between fuels without sacrificing power, efficiency or emissions,” Marcel Ott , General Manager Application Engineering, WinGD, said.
As well as optimising compression ratios for different fuels, VCR can also benefit engines operating under different ambient conditions and intake air compositions, such as when using exhaust gas recirculation.
Specifically, compression ratio is altered by changing the piston position to adjust combustion chamber volume.
According to WinGD, the simple mechanical configuration has no impact on engine footprint or installation requirements. VCR can also be adjusted for part load operation, meaning relatively larger savings can be achieved at the low speeds that operators may consider to further reduce their emissions. WinGD plans to introduce VCR as an option for its X72DF, X62DF and short-stroke X62DF-S engines, with retrofit packages available after the technology is introduced for newbuilds.