TAIZAC -TAndem Injectors Zapping ACtivation- for Thermal Efficiency Improvement of Diesel Engine

In order to explore the potential of thermal efficiency improvement of diesel engines with injection rate shaping, TAIZAC (TAndem Injectors Zapping ACtivation) injector consisting of commercially available two common-rail injectors was developed in-house. A simple architecture adopted for TAIZAC injector consists of an upper injector connected to a high pressure source, a lower injector injecting into the cylinder and sealing parts between the two injectors. A fast response piezo-actuated injector (G3P) was employed as the upper one with an additionally drilled large axial orifice for faster fuel supply. A solenoid-actuated injector (G4S) was employed as the lower one for its applicability to inner volume reduction by body cut. Control of injection timing and duration of the upper injector realized not only the originally targeted inversed-delta injection rate shaping, but also sharper rise of initial injection rate and modulation of injection pressure among and during multi-injection pulses. Single cylinder diesel engine performance tests were conducted to demonstrate the effects of a combination of 100MPa low pressure pre and pilot injections, sharper rise of initial injection rate and inversed-delta rate shaping for 200MPa high pressure main injection. Compared to the case of conventional G4S injector, TAIZAC injector case exhibited 1.4pt improvement of indicated thermal efficiency mainly due to 2.3pt reduced cooling loss.