Wartsila

The 380 mm bore/475 mm stroke W38 design was developed by Wartsila Diesel's Dutch subsidiary Stork-Wartsila Diesel as a replacement for its ageing TM410 engine (see Chapter 28), filling a power gap in the group portfolio between the Vasa 32 and W46 designs. The W38 series was introduced in 1993 with a specific rating of 660 kW/cylinder at 600 rev/min to cover a power band from 3960 kW to 11 880 kW with six, eight and nine in-line and V12-, 16- and 18-cylinder models (Figure 27.17).

The design was distinguished by a new combustion philosophy applied to achieve a high thermal efficiency and reduced NOx emissions (down by 50-70 per cent) without compromising fuel economy. The key parameters are a stroke/bore ratio of 1.25:1, a maximum cylinder pressure of up to 210 bar and a maximum fuel injection pressure of 1500 bar. Such parameters provide the flexibility to select a compression ratio, injection timing and injection rate that allow the desired low NOx values to be attained.

A completely new fuel injection system was developed with the following characteristics: suitable for continuous 1500 bar injection pressure; closed barrel; optimized constant pressure valve design for

V18 Engine Bracket
Figure 27.17 V18-cylinder version of the Wartsila 38 engine

short injection period and high brake mean effective pressure; no mixing of lubricating oil and fuel between plunger and barrel to avoid lacquering and sticking; separation of leakage fuel from the oil sump to avoid lubricating oil contamination; integrated low pressure fuel supply lines; fuel injection valves with uncooled nozzles; and shielded high pressure lines and connections. The fuel injection system is fully covered by the hot box, and possible low and high pressure leakages are detected by alarms.

The fuel pump has an integrated low pressure channel which means there is no low pressure pipe to fit to the pump because the fuel pipes are fitted directly to the fuel pump foundation. Integrated fuel pulse dampers in the fuel supply lines ensure low pressure pulses on the system side. Each fuel pump is equipped with a flow distribution throttle. The high pressure fuel pipe is shielded and fitted with a leak alarm. Maintenance is facilitated by a locking device flange on the cylinder head for the high pressure pipe.

The engine starting system incorporates a starting fuel-limiter to secure a smooth and safe start. Each fuel pump is equipped with an overspeed trip cylinder to ensure that the fuel rack is pushed to zero in the event of overspeed. Additional safety is provided by an extra stop cylinder turning the regulating shaft to zero in the event of overspeed. Overall compactness and lightness were prime targets for the W38 engine designers. Component integration resulted in 40 per cent fewer parts than the older generation TM410 engine, with many of the traditional bolted-on elements now incorporated in the main block casting (for example, lines and piping for lubricating oil, cooling water and fuel).

Simplicity of maintenance and extended overhaul intervals were other design goals, with only a modest envelope required for servicing and dismantling. Engine-driven cooling and lubricating oil pumps as well as engine-mounted coolers and filters simplify installation and release machinery space. integrated brackets are provided for resilient mounting systems. The bending stiffness and torsional rigidity of the engine block and crankshaft allow savings in the specification of flexible couplings, torsional vibration dampers and elastic elements for resilient mounting.

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