4

thus opened up for controlling different load modes and fuel qualities, even allowing injection retardation when lower NOx emission values are demanded.

A contribution to reliability by the fuel pump design comes from splitting the plunger loading between two cams and rollers, thus lowering the loading on these components and underwriting safe operation at injection pressures up to 2000 bar. The associated tappets for these components are both integrated in the same housing as the tappets for the inlet and exhaust valves.

The high pressure fuel system was designed and endurance tested at 2000 bar; an actual injection pressure of around 1400 bar thus represents a substantial safety margin. No lubricating oil is required for the pump element since the plunger has a wear-resistant low friction coating. A profiled plunger geometry keeps the clearance between the plunger and barrel small, allowing only minimal oil to pass down the plunger; the small leakage is collected and returned to the fuel system. Any chance of fuel mixing with the lube oil is eliminated. Both the nozzle and nozzle holders are made of high grade hardened steel to withstand the high injection pressures and, combined with oil cooling of the nozzles, to foster extensive nozzle lifetimes.

Low pressure fuel system safety is underwritten by the Wartsila-patented multi-housing concept. The fuel line consists of channels drilled in cast parts which are clamped firmly on the engine block and connected to each other by simple slide-in connections for ease of assembly and disassembly. The pumps are connected together to form the complete low pressure fuel line with both feed and return channels; any need for welded pipes is eliminated. Safety is further enhanced by housing the entire low pressure and high pressure systems in a fully covered compartment.

Turbocharging system: based on non-cooled turbochargers with inboard plain bearings lubricated from the engine's lube oil system. The Spex (single pipe exhaust) turbocharging system is standard, with the option of exhaust waste-gate or air bypass according to the application. Spex, which exploits the pressure pulses without disturbing the cylinder scavenging, is described in the Wartsila 46 engine section above. The interface between the engine and turbocharger is streamlined, eliminating all the adaptation pieces and piping formerly used.

Cooling system: split into separate high temperature (HT) and low temperature (LT) circuits (Figure 27.33). The cylinder liner and cylinder head temperatures are controlled through the HT circuit; the system temperature is kept at a high level (around 95°C) for safe ignition/ combustion of low quality heavy fuels, including operation at low loads. An additional advantage is maximum heat recovery. To further increase the recoverable heat from this circuit it is connected to the high temperature part of the double-stage charge air cooler. The HT water pump is integrated in the pump cover module at the free end of the engine; the complete HT circuit is thus virtually free of pipes.

Air separator

Air separator

Figure 27.33 Cooling water system of Wartsila 64 engine

Figure 27.33 Cooling water system of Wartsila 64 engine wArtsilA

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