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Two types of high pressure injection equipment, which can produce a pressure of 250MPa, have been developed. One is a hydraulic pressure intensified type, having a “GRADUAL RISE AND SHARP CUT” injection rate pattern. The other is a pressure accumulator type, having a “SQUARE” injection rate pattern. These equipments have been evaluated with a high pressure vessel for analyzing the effect of injection pressure and injection rate upon the characteristics of non-evaporating fuel spray. High speed photography, shadow photography, holography and image analysis techniques were used for these studies. It was found that the fuel injected under high pressure forms finer droplets and produces a leaner mixture. It was also found that several differences exist in the structure of fuel spray between the accumulator type and the pressure intensified type. The reasons for these differences are discussed herein.

A high pressure injection equipment (HPIE), which is an electronically controlled. hydraulic pressure intensified system that can produce 250MPa, has been developed. This equipment has been evaluated with shadow photographs for analyzing non-evaporating fuel spray characteristics. It was found that the fuel injected at high pressure forms a finer and more homogeneous spray. Then the HPIE has been fitted to a naturally aspirated 2 liter single-cylinder diesel engine and tested. It was found by the test that black smoke and particulate emissions decreased extremely, under suitable injection timing for low NOx emission. The emission test data at 220MPa of injection pressure shows that more than 80% reduction of particulate emission has been realized at the same NOx level as with a conventional jerk pump. These results indicate that the high pressure fuel injection is an effective means for reducing NOx, smoke and particulate emissions at the same time.