Further Development and Experimental Analysis of a New Common Rail Fuel Injection System without Accumulator

An innovative hydraulic layout for Common Rail (CR) fuel injection systems (FIS) without accumulator was further developed and assessed. The rail was removed and replaced by a high-pressure pipe junction to have faster dynamic system response during engine transients, smaller pressure induced stresses and reduced production costs. Compared to a commercial rail, whose internal volume ranges from 20 to 40 cm3 , the junction provided a hydraulic capacitance of about 2 cm3 with the main function of connecting the pump delivery to the electroinjector feeding pipes. The modified injection system was realized and subjected to experimentation under engine-like working conditions on a high performance Moehwald-Bosch test bench. The injection performance of the new system with different hydraulic layouts was shown to be generally similar to those of a commercial CR system. Besides, for multiple injections, the new layout dynamics were substantially improved by a reduced dependence of the overall injected fuel amount on dwell-time (DT) during sequential injection events. This was achieved by selecting injector supplying pipes with an internal diameter and length out of the present production range. The results supported the findings that the rail capacitance was not a key parameter in pressure wave disturbance attenuation.