Mitsubishi raises its game with new two-stroke generation
Mitsubishi is sometimes overlooked in the area of large two-stroke engine design and development, but the Japanese company is keeping up with current trends by introducing a super-long-stroke family in keeping with current operational practices, as discovered by David Tinsley.
As the sole competitor to MAN Diesel & Turbo and Wärtsilä in the large, two-stroke propulsion engine stakes, Mitsubishi Heavy Industries (MHI) has added another string to its bow by unveiling a new design developed specifically to suit slow-steaming practices.
The UEC-LSH series will assume first form in a 500mm-bore model, scheduled to be ready for service in early 2015 as the UEC50LSH-Eco-C2. The subsequent stage in the roll-out of the LSH generation may entail a 600mm-bore engine, depending on the outcome of current market investigations.
The super-long stroke UEC50LSH-Eco has been conceived mainly for Supramax and Handysize bulkers, medium-range (MR) tankers, vehicle carriers and smaller classes of containership, where slow-steaming is integral to the operating profile. In its highest output configuration, the engine will deliver 1,780kW/cylinder at 108rpm. However, an exceptionally wide rating field confers a high degree of application flexibility in terms of output and speed combinations, down to 1,030kW at 85rpm at the P4 rating point.
Complementing MHI’s extensive portfolio of UEC-LSE, UEC-LSE-Eco and UEC-LSII diesels covering bore sizes from 330mm to 800mm, the UEC50LSH-Eco engine is claimed to offer superior fuel economy to that of other manufacturers’ similarly-powered, 500mm-bore models. In its six-cylinder configuration, delivering 10,860kW maximum continuous output at 108rpm, specific fuel oil consumption (SFOC) is stated as 164g/kWh. The special slow-steaming capability, distinct from the low-load operation allowability of the latest marine engines, gives an extra edge to efficiency and long-term maintenance benefits.
MHI advised The Motorship that a letter of intent had been received from a Japanese shipbuilder for the first example of the new engine type. For reasons of confidentiality, the newbuild project cannot be identified, but it does involve a Japanese shipowning principal.
Electronically-controlled, Eco variants of mechanically-driven LSE engines have been in service since June 2005. The UEC50LSH-Eco represents an adaptation of the concept, in that electronically-controlled fuel oil injection system is combined with camshaft-controlled exhaust valve actuation. Hydraulic oil for the Eco system is supplied by electric pump.
An improved trade-off between SFOC and nitrogen oxide (NOx) emissions has been achieved by optimising fuel injection pressure and rate, while the new engine incorporates the Low Load Optimisation (LLO) tuning mode successfully applied in UE engines to reduce SFOC at part load.
The turbocharger is arranged on the exhaust side, reflecting shipyard requirements. A variable turbine inlet (VTI) version of the proprietary MET turbo is available as a cost-effective option for slow-speed operation. The LSH generation has been conceived for continuous low-load operation down to 20% load, and promises smokeless performance across-the-board. Developed in-house, the advanced electronically controlled lubrication (A-ECL) system trims lube oil consumption by reducing the feed oil rate, especially under part-load conditions, by adapting the supply in accordance with mean effective pressure.
Besides the key objectives of increased energy efficiency and correspondingly lessened environmental impact, MHI’s design technicians set new goals with regard to maintainability and reliability, and ease of installation. The company’s shipbuilding and ship technology knowledge has undoubtedly fed into the engine design process. The LSH engine’s relative compactness is an important feature, and could potentially facilitate retrofit as well as newbuild projects.
The new design is said to reduce the need for countermeasures relating to torsional vibration and the second order moment, while the Eco system element contributes to lessened installation work.
The addition of the LSH to MHI’s UE portfolio follows last year’s seagoing debut of the new, 800mm-bore UEC80LSE-Eco engine and the delivery of the first 350mm-bore UEC35LSE-Eco type, expressing renewal of the range at both ends of the power spectrum.
Targeted at VLCCs and very large ore carriers (VLOCs), the UEC80LSE-Eco yields a maximum output of 4,440kW/cylinder at the top rating, representing a 15% advance in power relative to the engine which it is intended to eventually succeed, the 850mm-bore UEC85LSII, the largest in the UE family. Unlike a conventional, mechanically-actuated engine, the UEC80LSE-Eco employs solenoid valves, rather than a camshaft, to control fuel injection quantity and timing. The exhaust valves and starting air are also solenoid-actuated.
The UE offering is set to be expanded in 2015 by a dual-fuel two-stroke type, designated the UEC-LSGi. It is understood that LSGi technology will initially be applied to a 600mm-bore engine, to serve the 11,000-18,000kW power band.
With effect from the start of October 2013, the development, design, sales, after-sales service and licensing of MHI’s marine engines, turbochargers, boilers, steam turbines, deck machinery, steering gear, propellers, stabilisers and other equipment was vested in a separate undertaking, MHI Marine Machinery & Engine Company (MME). While MHI-MME maintains close collaboration with its parent in key spheres such as research and development (R&D), procurement, and manufacturing, the rationale behind its formation has been to create a more pro-active business in the marine engineering and ships’ equipment market, achieving faster decision making and responsiveness to new opportunities and customer requirements.
MHI-MME is taking forward the three basic strategies set in train by the forerunner marine machinery and engine division. These entail globalisation through collaboration with both domestic and overseas manufacturing partners, increased emphasis on the after-sales service business and customer relationships, and the ambitious Project MEET strategy. The far-reaching MEET initiative, the acronym for the Mitsubishi Marine Energy and Environment Technical Solution System, is focused on delivering new, energy-saving ‘green technology’-themed solutions, stretching across all the product areas covered by the company.
A key aim of MEET is to draw the group’s specialised areas of know-how together to foster the provision of innovative, integrated solutions, with ‘packages’ or complete shipboard systems delivered, guaranteed and supported under the responsibility of a single company, MHI-MME.
The development of the LSH series of next-generation UE machinery, as with the nascent LSGi gas-injected design, is an outcome of the accelerated technology drive that underpins the MEET programme.
“The MEET project team encompasses employees involved in every facet of marine machinery, who pool their collective resources in an ongoing quest to respond to the energy and environmental demands for the ships of tomorrow,” stated MHI. Three major categories are addressed, wherein MEET-1 relates to solutions offering significant energy savings and attendant reductions in CO2 emissions, MEET-2 concerns NOx and SOx abatement, and MEET-3 is concentrated on the use of LNG as marine fuel.
Besides UEC Eco engine technology, which MHI contends affords the world’s highest thermal efficiency, the MEET-1 solutions category includes the Mitsubishi energy recovery system (MERS), Organic Rankine Cycle (ORC)-based power recovery, the hybrid MET turbocharger and variable turbine inlet (VTI) turbo, and proprietary MAP Mark-W propellers. VTI turbochargers, like the electro-assist turbos currently under development by MHI-MME, offer particular merits in slow-steaming applications, by improving engine performance under low loads.
In the electric power-assisted turbocharger, a drive shaft with a powerful permanent magnet is attached directly to the end of the rotor axle of a conventional MET turbo. A coil that provides the torque is attached to the outside of the body. By sending power during slow steaming that is optimal to the speed, the turbocharger rotor is accelerated, ensuring the requisite air pressure and volume, even at low speeds.
The Mark-W version of the Mitsubishi Advanced Propeller (MAP) series is reckoned to give 2% better fuel consumption than conventional MAP propellers, with extra performance gain when matched to slow-steaming requirements. Pivotal to the attributes of the Mark-W design is the modified shape of the blade tips, improving propeller efficiency without sacrificing cavitation margins.
MERS is a novel energy-saving turbo generator system that recovers and reuses energy from the main engine’s exhaust gas, optimising efficiency by automatically adjusting the output according to the onboard electricity demand. Improvements of up to 10% in fuel consumption are claimed for MERS, which has attracted substantial sales. MERS steam turbine generator (STG) installations have been specified for Maersk’s Triple-E generation of 18,270teu containerships ordered from the Daewoo yard in Korea.
MEET-2 covers leading-edge emission abatement technologies to ensure compliance with IMO Tier III NOx limits. In addition to selective catalytic reduction (SCR), MHI has developed an exhaust gas recirculation (EGR) system that incorporates a high-performance scrubber designed to remove up to 98% of SOx and particulate matter(PM) as well as curbing NOx by 80%.
The recent nomination of MHI-developed UST steam turbine propulsion plant for a series of LNG carriers contracted by Petronas of Malaysia from Hyundai Heavy Industries testified to the competitiveness of the powering solution in the face of the widespread uptake of dual-fuel diesel-electric systems. At the time of the deal, last November, USTs were already under manufacture for eight ships on order with MHI.
The adoption of a reheating and regenerative cycle in the UST design results in an efficiency improvement of approximately 15% compared to conventional steam propulsion plant. This, together with the long-term maintenance benefits of a steam turbine relative to a multi-engine, multiple-cylinder DFDE installation, and the latent popularity and deep experience of steam within the LNG tanker community, is stimulating fresh consideration and investment in the steam turbine mode.
Under the MEET project, the UST is proposed as an advanced gas combustion propulsion plant, given its suitability for oil, gas and dual firing. Besides its thermal efficiency advantage over conventional steam plant, UST is also claimed to offer improved economy relative to a DFDE powering and propulsion arrangement since it results in minimal power transmission and transfer losses. The current development of a gas-injection UE engine, the UEC-LSGi, will augment the solutions available under the MEET-3 category.
Clearly, the MEET initiative in conjunction with corporate restructure underscores MHI’s intention to play to the group’s strengths in a more integrated manner than before.
MAIN PARTICULARS: Mitsubishi UEC50LSH-Eco-C2 engine
Cylinder bore, mm 500
Piston stroke, mm 2,300
Stroke-to-bore ratio 1.780
Max output per cylinder(P1 rating), kW 1,780
Max speed(P1 rating), rpm 108
Number of cylinders 5,6,7,8
Max power range(P1 rating) 8,900-14,240kW
Brake mean effective pressure(BMEP), bar 21.9
SFOC, 100% load, g/kWh 164.0
Lowest rating field, P4 @85rpm 5,150-8,240kW
BMEP, bar (P4) 16.1
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