two-stroke engines
48-bore model completes RT-flex series
Wärtsilä’s proven common rail RT-flex technology is now available across its low speed range
by Doug Woodyard W
ork on applying common rail RT-flex systems to all bore sizes in its low speed engine programme was recently completed by Wärtsilä with the testing of a six-cylinder RT-flex48T model at the facilities of the Chinese licensee QMD. The 480mm-bore design is offered in five to eight- cylinder versions to cover a power band from 5,100kW to 11.64MW for propelling small bulk carriers and tankers, including Handysize and Handymax tonnage. Structurally
based on the established
camshaft-controlled RTA48T engine, the new model benefits from the electronic control of fuel injection and exhaust valve actuation by RT-flex common rail technology. Significantly lower emissions and fuel consumption are realised, along with smokeless operation at all engine load levels.
The precise control of fuel injection and a high injection pressure at all speeds also foster steady running, while electronically-controlled exhaust valve opening and closing enables engine tuning to be optimised to the individual rating. Common rail and supply units taken from
the RT-flex50 engine comprise a CR pipe for fuel injection and another for the system oil driving the exhaust valves. Both are integrated within the rail unit, located just below the cylinder covers and running along the full engine length, where all pipework and components are easily accessible from above. The first Wärtsilä X35 low speed engine was also run last November by another Chinese licensee, Yuchai Marine Power,
at its new
48,000m2 factory on the southern estuary of the Zhujiang Delta in Guangdong Province. YCMP has reportedly secured substantial orders for the 350mm-bore electronically-controlled engine type which, along with the 400mm-bore X40 design, represents Wärtsilä’s renewed challenge in the smaller two-stroke propulsion arena. Originally introduced as the RT-flex35 and
RT-flex40 models, the X-generation series was relaunched last May with designations
www.mpropulsion.com
A 480mm-bore design has finalised the RT-flex programme, headed by this six-cylinder RT-flex48T-D model from Chinese licensee QMD
consistent with the overall product portfolio. The Finnish group’s proven common rail
RT-flex technology is exploited, with other features addressing changing market demands. An extra long stroke, for example, promotes improved fuel economy and enables propeller requirements to be satisfied within the rating field.
Coastal and river vessel propulsion is a particular target for the engines, making China a key market and YCMP committed to being
WÄRTSILÄ RT-FLEX48T Bore Stroke
Stroke/bore ratio Cylinders
Output/cylinder, MCR Power range
Speed range (R1-R3) Mean piston speed (R1)
Mean effective pressure (R1)
Maximum cylinder pressure
Sfc, full load (R1-R2) 480 mm
2,000 mm 4.16:1 5-8
1,455kW
5,100kW-11.64MW 102-127 rpm 8.5m/s 19 bar
160 bar 164-170 g/kWh
a dedicated manufacturer of the X-series. The licensee also signed the first contracts for X40 engines in November.
Wärtsilä has already strengthened its mid-bore low speed engine programme with new 620mm and 720mm designs promising high propulsion efficiency, reliability and low cost of ownership for bulker, tanker and feeder container ship operators. The first 62-bore engine will be available for delivery in September 2013 and the first 72-bore engine approximately a year later. In January-September 2011, Wärtsilä reports,
its share of the low speed engine market rose to 18 per cent from 17 per cent in the previous period. References were boosted by an order for eight RT-flex60C engines from Shanghai-based licensee Hudong Heavy Machinery, the first of which will be delivered this year. The engines will power a series of 1,700 TEU feeder container ships building at the Guangzhou Wenchong yard for Buss Shipping of Hamburg (four) and Eastern Mediterranean Maritime (four). • A 10-year extension to an existing agreement enables Doosan Engine of Korea to build Wärtsilä low speed engines under licence from 2012 to 2021. MP
Marine Propulsion I February/March 2012 I 31
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