Experimental Study On Highly Premixed Charge Combustion (HPCC) Of N-butanol/Biodiesel Dual Fuel

The research of new types of combustion and bio-fuels has been an importantdirection of the efficient and clean inner combustion engine combustion investigation.Dual-fuel high premixed charge combustion (HPCC) is a new type of combustionmode based on the new generation of combustion mode, like HCCI, PCCI. HPCCshows a compound combustion characteristics of different combustion modes atdifferent load conditions, but they share a common feature: the inlet fuel is injected toform a large proportion of the pre-mixed gas (above60%), showing a high proportionof premixed combustion. In this paper, n-butanol and biodiesel HPCC test was carriedon an internal combustion engine applied to the extended range electric vehicle.On a modified single-cylinder diesel engine, with bio-diesel direct injection andthe inlet jet of n-butanol, a reasonable choice of bio-diesel injection timing andn-butanol ratio achieve the HPCC. The influence of n-butanol ratio，biodieselinjection strategy and EGR rate on HPCC characteristic and emissions is studied at afixed speed high load condition.The results indicated that n-butanol ratio、EGR rate and biodiesel injectionstrategy affect HPCC characteristic and emissions by the influence of the chemicalreactivity and the chemical reactivity stratification of cylinder mixture. HPCC is acompounded combustion model comprised of multi combustion style.Higherproportion of n-butanol (about80%) and biodiesel single early spray can effectivelyadjust the chemical reactivity distribution in cylinder, and the suitable EGR rate (40%)is effective to control the pressure rise rate, so that the pre-mixed low temperaturecombustion proportion increased.Then ultra low NOx and smoke emissionsmeanwhile with high efficiency could be achieved by varying the biodiesel injectionstrategy,EGR rate and n-butanol ratio. Due to the use of bio-fuels, soot emissions arevery low throughout the test.The rate of pressure rise is the constraints of expanding load when biodiesel issingle injected. Biodiesel twice injection strategy studies show that reasonableadjustment of the main injection timing, the main injection quantity and the n-butanolratio can effectively adjust the chemical reactivity in cylinder, which control the the HPCC process in order to obtain a higher thermal efficiency and low NOx and sootemissions, while significantly reducing the maximum rate of pressure rise. Furtherresearch in the expand of load show that the appropriate injection timing withincreasing the proportion of n-butanol and the main fuel injection, can expand HPCCoperating conditions to a heavier load conditions and achieve the lower NOx and sootemissions the same time.