Abstract
In order to decrease the necessary number of units and cylinders for a given power and reduce the maintenance costs of diesel engine, SEMT has eagerly continued to obtain the more powerful units by increasing the cylinder bore and specific performance of engine. Concerning the above, PC4 type large bore medium speed diesel engine - 1500 ps/cyl. - was developed and tested successfully during 5, 000 hours and then the improvement for easier maintenance operation has been achieved. Also the two stage supercharging engines were completed without increasing the max. combustion pressure by adoption of the low compression ratio and, the power 1000 ps/cyl, on PC2 engine and 550 ps/cyl. on PA6 engine were obtained as a result of the above.
On the other hand, reducing the maintenance costs and decreasing the lub. oil and fuel consumption were studied in order to improve the competitivity of the medium speed engine to the low speed engine. Moreover, this paper shows the results of study in the field of exhaust gas emission, especially nitrogen oxides and the important modifications - recycling of the exhaust gas and pre-injection etc. - have been introduced to reveal their influence on the pollution.
