Fig. 2.4.8-2 Section of HMG50 Type Reversing Device
2.4.9 Hitachi Zosen Corporation
(1) Development of new model
The series engines of 12K90MC type were produced from last year on, and the test of reduction in thermal load of piston and the test of new fuel valves coping with emission were carried out. As a result, the new design of combustion chamber was established, that is, in order to extend the penetration of fuel sprays and lower the temperature around the piston top land, the structure of piston crown was altered from the traditional deep bowl type to the camel back type.
Fig. 2.4.9-1 indicates the new structure of piston crown compared with the current one.
Fig. 2.4.9-1 Comparison of Piston Structures
(2) Annual results of manufacture
Total number of engines 52 sets
Total horse power 976,000PS
2.4.10 Makita Corporation
(1) Development of new model
Though there was no development of new model, the NOx reduction test was carried out on the low-speed 4-cycle L31M engine (cylinder diameter: 310mm, stroke : 600mm, mean effective pressure 2.03MPa, number of cylinders: 6, engine speed 320rpm, output : 1,471kW).
In 1996, the combination tests of injection timing retard and high compression ratio were carried out, aiming at reducing NOx without adding the special equipment to the engine. As a result, NOx reduction by 25% was achieve with no penalty in fuel consumption.
In 1997, the pre-injection type fuel injection system was developed in partnership with Japanese Marine Equipment Association as an undertaking supported by Japan Foundation, aiming at realizing the ideal combustion at constant pressure for more reduction of NOx.
In 1998, the pre-injection type fuel injection system developed in the previous year was tested continuously. As a result, the ideal combustion at constant pressure was realized and NOx reduction by 40% was achieved without any penalty in fuel consumption.
