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In an effort to protect the earth's environment, emission regulations in the diesel engine field are becoming increasingly strict. One way of meeting these regulations is to atomize the fuel spray by using a fuel injection system with high-pressure injection, which activates engine combustion. With current in-line pump systems, however, it is still possible to satisfy the demand for cleaner emissions by improving the fuel spray, through measures such as reviewing high-pressure injection and initiating improvements in the nozzle. This report describes the new in-line pump system for medium duty diesel engines to meet future emission regulations. In this report, we will describe how analytical technology, such as computer simulation, was used on the pump side to make improvements for higher injection pressure.

This paper describes the Nippondenso in-line pump system designed for U.S. 1991 emissions regulation for medium duty diesel engines. With the combined use of the further improved in-line pump, NB-S and the multi-hole nozzle with a smaller orifice diameter, the required injection pressure of 100 MPa to 120 MPa at the nozzle can be achieved. However, some problems to be resolved exist in the subject fuel injection system: (1) secondary injection, (2) cavitation erosion of injection pipe, (3) higher pressure sealing of fuel, (4) undesirable fuel delivery curve vs. pump speed (called “Trumpet Shape” fuel delivery curve) Thus technical measures to cope with those problems are explained in details.