Heavy Fuel Oils
Another important step in strengthening the status of the diesel engine in marine propulsion was R&D enabling it to burn cheaper, heavier fuel oils. Progress was spurred in the mid-1950s by the availability of cylinder lubricants able to neutralize acid combustion products and hence reduce wear rates to levels experienced with diesel oil-burning. All low speed two-stroke and many medium speed four-stroke engines are now released for operation on low grade fuels of up to 700 cSt/50°C viscosity, and development work is extending the capability to higher speed designs.
Combating the deterioration in bunker quality is just one example of how diesel engine developers—in association with lube oil technologists and fuel treatment specialists—have managed successfully to adapt designs to contemporary market demands.
Figure I.10 Direct fuel injection system introduced by Sulzer in 1930, showing the reversing mechanism and cam-operated starting air valve. Airless fuel injection had been adopted by all manufacturers of large marine
1930s: a major drawback of earlier engines was the blast injection system and its requirement for large, high pressure air compressors which dictated considerable maintenance and added to parasitic power losses engines by the beginning of the
Figure I.10 Direct fuel injection system introduced by Sulzer in 1930, showing the reversing mechanism and cam-operated starting air valve. Airless fuel injection had been adopted by all manufacturers of large marine
1930s: a major drawback of earlier engines was the blast injection system and its requirement for large, high pressure air compressors which dictated considerable maintenance and added to parasitic power losses engines by the beginning of the
Figure I.11 Cross-section of Sulzer SD72 two-stroke engine (1943). Each cylinder had its own scavenge pump, lever driven off the crosshead. The pistons were oil cooled to avoid the earlier problem of water leaks into the crankcase
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