In order to increase the brake thermal efficiency and reduce NOx emissions of an industrial diesel engine, a direct injection (DI) combustion system, which consists of a combustion chamber with a high compression ratio and a fuel injection system with a high injection pressure, was installed in a 6 cylinders engine with 102 mm bore and 130 mm stroke, and it was tested to investigate its potential and fundamental characteristics. The high compression ratio was proven to become advantageous on the point of the brake thermal efficiency and NOx emissions. The high injection pressure by means of small nozzle hole diameter promoted the diffused combustion and reduced smoke emission under the high compression ratio and the retard of fuel injection timing.
