Studies on combustion and exhaust emissions in a high speed diesel engine. (1st report. Reduction in exhaust NO_x)

The authors have been conducting studies on the reduction of exhaust emissions using a high speed diesel engine with a bore of 110 mm and a maximum speed of 2 500 rpm. By applying composite countermeasures consisting of five items ; 1) timing retard, 2) optimization of fuel injection system, 3) water-in-oil type emulsified duel, 4) application of ignition improver and 5) an increase in air flow quantity, an exhaust NO_x level about a half of the original was attained while retaining the original low levels of fuel consumption, smoke density and engine noise. Especially, in combustion tests on water-in-oil type emulsified fuel, it is clearly demonstrated that not only exhaust NO_x but also smoke density are significantly reduced due to an increase in the excess air ratio of the fuel spray.