| With the pressure of world’s energy crisis and environmental protection, Manystrategies have been widely investigated all over the world to meet the requirements of thehigh efficiency and low emissions on internal combustion engine. Homogeneous ChargeCompression Ignition(HCCI) combustion mode is one of the typical. However, the controlof ignition timing and burning rate of HCCI is more difficult than the conventional dieselengine, resulting in limited operating range of HCCI engine. In this study, a dual-fuelengine using direct injection of diesel and a port injection of gasoline was practicallyattempted to achieve very low NOxand Soot emission in a wider operation range thanHCCI.Gasoline injection system and control units,including hardware circuit design, controlprocedures as well as upper PC control software, were developed to suit for dual-fuelPPCI mode. In the last, the static flow rate of the gasoline injector was calibrated. theresults show that the system can well meet the test requirements and can flexible controlof fuel injection parameters.The experimental and CFD simulation researches of dual-fuel PPCI were made basedon this4-stroke diesel engine. Simulation results show that, the timing of direct injectionof diesel is very important to dual-fuel PPCI combustion. this can be an effective methodto solve the control of igniton timing in this combustion mode. The experimental resultsshow that, the dual-fuel PPCI combustion has the potential to reduce the NOxand Sootemission at the same time. That means the problem of NOxand soot trade-off can besolved by this method. When the gasoline percentage varys from0to0.8, the fluctuationof gross thermal efficiency is within5%, but the NOxand Soot emissions decreased rapidly. Both of them were almost zero emission when the gasoline percentage is over0.8,but in the same time, THC and CO emissions were increased very much.Exhaust Gas Recirculation (EGR) is one of the most important ways to reduce theNOxemission. in this study, intake charge compositions were investigated by means ofsimulation and experiments. The results show that, under the same oxygen volumefraction, the dilution effects of CO2and N2give a similar effectiveness to the reduction ofNOx, but the intake air with larger Moore constant can apparently inhibit the formation ofSoot. |
