Abstract: Ultrasonic flaw detection uses a phased-array ultrasonic-flaw-detection probe. The flaw detection probe is placed such that the center of curvature of the flaw detection probe coincides with a reference center of curvature of a subject. The flaw detection probe is translated along a scan direction. The flaw detection probe emits an ultrasonic beam such that the position upon which the ultrasonic beam converges coincides with the center of curvature of the curve of the outline of the cross section of the subject at the scan position, receives the resulting reflected beam, and estimates the length of a flaw in the circumferential direction of the subject. In addition, the estimated length of the flaw is corrected using a correction coefficient corresponding to the distance between the center of curvature of the reference scan position and the center of curvature of the scan position in the thickness direction of the subject.

Abstract: A combustion chamber of a direct fuel injection type diesel engine has a cavity at the crown of a piston, within which a swirl occurs and onto which fuel is injected from a multi-orifice fuel injection nozzle toward a inner side wall of the cavity. The cavity is regular polygonal in horizontal cross-section. The inner side wall is so inclined inwardly of the cavity as to provide a restriction at the opening of the cavity. The inner side wall and the injection nozzle are so arranged that the fuel jet is distributed to the downstream side of the swirl after being impinged the inner side wall, whereby the distribution of the injected fuel is improved to provide ideal mixture in the cavity, resulting in reduced amount of pollutant emissions.