Effect Of Injection Parameters On The Performance In A High-pressure Common Rail Diesel Engine Fuelled With Waste Cooking Oil Biodiesel

Biodiesel is a kind of green, efficient and clean renewable energy and its physical andchemical characteristics is very close to diesel so that biodiesel is an effective alternativecompared with diesel fuel. High pressure common rail fuel injection system can greatlyimprove fuel economy and dynamic property, as well as reducing emissions and noisecompared with conventional injection systems.This paper studies how injection pressure and injection timing affect combustioncharacteristics and emission in a single-cylinder common rail direct injection diesel enginewhich is filled with biodiesel made by waste cooking oil and diesel respectively through aseries of tests. And then fatty acid composition and main combustion characteristics ofbiodiesel were studied and compared with diesel. Under two kinds of different load conditions（fuel injection quantity per cycle D:BD=20：22.1mg/cycle and D:BD=40：44.3mg/cycle）,this engine test is set into two kinds of injection pressure (80MPa and160MPa) and differentinjection timing (from-25oCAto0oCA). In this paper, the main conclusions are:(1) Under two different load conditions, fuel economy and emissions characteristics ofbiodiesel and diesel were studied under80/160MPa injection pressure and from-25to0degree injection timing respectively. The results show that, under the same conditions of theinjection pressure, the indication of fuel consumption rate of biodiesel is higher than diesel’s.Under most conditions, fuel economy deteriorates with injection pressure increasing. Undermost conditions, the CO emissions of biodiesel produced less than diesel. With increasing ofinjection timing, NOx emissions also increases. Injection timing change has little effect onHC emissions. At low speed, when injection pressure increases, HC emission from biodieselis less than diesel. At high speed, HC emissions of biodiesel is lowest when injection pressureis160MPa. When injection pressure is80MPa, HC emissions of biodiesel is higher thandiesel’s. Under all operating conditions, soot emission of biodiesel is lower than diesel’s.(2) In this test, fuel injection timing is set at15oCA as a precondition. The combustioncharacteristics of biodiesel and diesel were compared under80/160MPa injection pressure.The results showed that, in high-load conditions, combustion pressure increased withinjection pressure increasing. At the same injection pressure, the combustion pressure peak is almost equal between biodiesel and diesel. Under all the conditions, the curve of biodieselpressure rise rate shifts somewhat later than diesel’s. Under most conditions, the peak pressurerise rate of biodiesel is higher than diesel’s.(3) In this test, setting injection pressure at80MPa, combustion characteristics ofbiodiesel and diesel were studied under20oCA,10oCA and0oCA injection timing conditionsrespectively. Under most conditions, the peak combustion pressure of biodiesel is less thandiesel. Under high load conditions, except the peak pressure rise rate of biodiesel beinggreater than diesel’s under10oCA injection timing in1400rpm condition, the peak pressurerise rate of biodiesel is almost equal to diesel’s in the rest of injection time. Under800rpmlow load conditions, instantaneous heat release rate of biodiesel gets maximum but diesel’sgets minimum in10oCA injection timing. Under any injection timing conditions, the peak ofinstantaneous heat release rate of biodiesel is greater than diesel.