Japan Engine Corporation is pinning its post-2020 hopes on an engine that bucks the multi-fuel trend
The UE range of two-stroke engines has not stood still since former owners Mitsubishi Heavy Industries Marine Machineries & Engine Co merged its engine division with that of long-time licensee Kobe Diesel Co in April 2017. Under the new name of Japan Engine Corporation (J-ENG) the company has already launched several new UE models in the 33-60 cm bore size. It has also developed low-pressure NOx abatement solutions (both exhaust gas recirculation and selective catalytic reduction) for engines with a bore of 50 cm or more. But its latest project is even more innovative.
In December, the first UEC50LSJ-EGR engine was built at J-ENG’s factory, where it is now undergoing verification testing. This engine was developed with the support of The Nippon Foundation to address, in a very unusual way, the challenge posed by the IMO sulphur cap.
According to Chikara Matsuda of J-ENG, the sulphur cap brings three specific challenges: the first is around fuel oil consumption and balancing emissions requirements when choosing to comply with low-sulphur fuel oil.
“There is a trade-off between NOx emissions and fuel consumption,” says Mr Matsuda. “[For Tier III NOx compliance] consumption gets worse than ever and this in turn means that complying with the Energy Efficiency Design Index becomes more challenging.”
This interplay between the various emission demands is just one challenge. Capital cost is also a concern where owners plan compliance with scrubbers and LNG. For these options, engineroom layout is also tricky; scrubbers or LNG fuel gas supply systems require a huge engineroom, design becomes more complicated and cargo space may be compromised.
All these challenges led J-ENG to develop a new concept for an engine running solely on marine gas oil (MGO). The idea is to enable compliance with both NOx and SOx emissions while still reducing specific fuel oil consumption – therefore reducing fuel cost and making MGO competitive with the other compliance options.
J-ENG believes that the new UEC50LSJ offers several benefits to owners and operators. Fuel oil consumption is 5% less than the equivalent conventional engine. In the case of a UEC50LSJ equipped on a handysize bulk carrier with fuel oil consumption of around 20 tonnes a day, the fuel oil saving would be approximately one tonne a day. In the case of an MR tanker with consumption at around 30 tonnes a day, the saving would be 1.5 tonnes a day.
The engine is highly reliable and can reduce maintenance because MGO contains few residues and so does not lead to deposits in the combustion chamber and turbocharger. There is also less risk for cold corrosion due to the very low sulphur content in MGO.
Because it is a mono-fuel engine, there is no fuel oil changeover, cutting workload for crew and possible related human error. For the same reason, a simpler auxiliary system is required, with more straightforward tank arrangements. And because of the low viscosity of MGO, no heating system is needed, so the engineroom design can be simplified compared to one housing a conventional engine.
Four-pillars of JUMP
The concept – which the company calls JUMP (for ‘J-ENG Unique Marine Power’) – is based on four pillars. The first is low fuel consumption, which the company believes it can achieve through optimising swirl flow by scavenging air ports, optimising the fuel injection valve atomiser and making the combustion cycle more efficient.
Reducing NOx is achieved in two steps: IMO Tier II is met by a stratified water injection system, while the more stringent Tier III is met using low-pressure exhaust gas recirculation (EGR). The final step is to secure global SOx compliance, which is achieved using MGO only.
The most unusual part of J-ENG’s mono-fuel engine is the use of water injection to reduce combustion temperature and therefore limit NOx production. Once it had decided to use this approach, J-ENG had three such technologies to choose from.
Emulsion fuel injection systems make a water/fuel emulsion upstream of the fuel injection pump. This is supplied to the combustion chamber through fuel injection pump and valve. The only additional equipment needed is simple emulsification apparatus. The drawbacks of this method are that the ignitability of the fuel spray is unstable, especially on engine start up, and controlling the water/fuel ratio to match engine loads is difficult.
Independent water injection uses a conventional fuel injection valve and a separate water injection valve on the cylinder cover. The fuel and water are injected individually, dramatically simplifying the control mechanism for injection. But matching the water injection nozzle pressure over all engine loads is challenging.
A stratified water injection system offers the best of both worlds, with two water injection pumps injecting water through the fuel injection valve. Water is injected into the fuel during the interval between every fuel injection cycle. After the two water layers are inserted, the fuel injection pump lifts and layers fuel and water is injected into the combustion chamber through the fuel injection valve. The layered water efficiently catches the flame because the water is injected through the same injection holes.
J-ENG already had experience with this unusual injection system, having built four engines with stratified water injection. In the marine market, a 6UEC52/105D engine was integrated with the water injection system and on-board verification tests carried out for approximately 2,000 hours on Ginga Maru, the training ship owned by the Japanese Maritime Education and Training for Seafarers agency.
For the mono-fuel engine, the stratified water injection system was re-designed completely. The water injection pump and actuating system are also completely re-designed, and the engine control system has been made more flexible, with control modes including EGR system control.
Before the UEC50LSJ began running, the function and reliability of the injection system was tested on a test bench comprising one fuel injection pump, two water injection pumps, three fuel injection valves, piping, the hydraulic system and controller – the same configuration as the cylinder injection system on the real engine. The functioning of the water and fuel injection system was tested and confirmed. Next, an endurance test was run and after around 600 hours the water pump was inspected. The running surface and other functional parts were found to be in normal condition.
In the shop tests, Tier II and III engine performance tests were carried out. Fuel consumption at full load met the planned specific fuel oil consumption within a 5% tolerance of the IMO Tier II NOx emission limit. This means that the consumption at Tier III NOx would also be cleared.
After running with stratified water injection for around 80 hours, piston ring condition and cylinder liner condition were inspected. The running surface, piston head and land condition were all normal.
J-ENG reports that verification testing of the new engine has confirmed high reliability and compliance with both NOx and SOx regulations and an endurance test is ongoing. Verification of performance and reliability in field conditions will be carried out after the first engine enters service, expected in 2020.