| Under the dual pressures of fossil energy shortage and environmental pollution crisis, seeking renewable and clean fuels becomes a hot topic in the field of contemporary internal combustion engine. Pine oil is a biomass oxygenated fuel which is widespread in the earth. When compared to the diesel fuel, the pine oil is much better in terms of the low cetane number, the oxygen content and the boiling point.Besides, pine oil has a good solubility with diesel oil.With an equal calorific value to diesel oil, pine oil is a potential alternative fuel in the future.Therefore, the paper designed the program of pine-diesel fuel to reduce the limitation of the single fuel,firstly.And it then control the combustion process and realize the low temperature combustion in the cylinder by combining the injection strategies with EGR.The experiments were conducted on a high-speed, four-cylinder,turbocharged diesel engine and the rotate speed fixed at 1800rpm.four fuels were used,namely:PO (base diesel fuel), P20(blended 20% volume of pine oil), P40 (blended 40% volume of pine oil), P50(blended 50% volume of pine oil), respectively.Firstly the paper researched four kinds of fuels’ combustion performance and exhaust emissions operation at different loads and different EGR rate. The characteristics of load showed that:at full load condition, the output of torque were 293.5,292.7,290.1,287.2 N·m with different kinds of fuels(P0,P20,P40,P50),respectively.It was observed that pine oil can provided a comparable power output with diesel.The researching of EGR rate showed that:For the four fuels,when the EGR rate was less than 24.6%,with EGR rate increasing,the maximum pressure rise rate, Soot, CO and HC emissions had no significant changes,but NOx emissions decreased significantly. At the same EGR rate.There has less effect on NOx emissions by changing fuel characteristics by adding pine oil,while there has great impact on the maximum pressure rise rate;and the EGR rate was more than 24.6%,with EGR rate increasing,because excess air ratio reduced and delayed ignition postponed over,which leading to a sharp rise in Soot, CO and HC emissions.When the EGR rate was approaching 40%, NOx emission was almost close to zero.At the same EGR rate,because of the low cetane number and oxygen-containing with pine oil,soot emission reduce with increasing the blended ratio of pine oil, the soot emission of P50 is close to zero entire EGR rate.It has great impact on the nucleate mode particles (Dp<50nm) at small EGR rate,when accumulation mode particles (Dp>50nm) at large EGR.It can reduce the number concentration and mass concentration of soot particles effectively by blended pine oil in diesel.Secondly,applying the middle EGR rate (24.6%) to investigate the effect of injection strategies (main injection timing, injection pressure, pilot quantity, pilot timing) on the combustion and emission characteristics of four fuels. The results indicated that advancing the main injection timing made the peak of in-cylinder pressure increase, the start point of combustion advance and the brake specific fuel consumption decrease under single injection of certain injection pressure. Meanwhile, it increased the emissions of CO and THC, decreased the emissions of soot and NOx. Increasing the injection pressure can reduce the emissions of NOx, soot, CO and THC simultaneously with the EGR addition in the low temperature combustion under a single injection of certain injection timing. Besides, it reduced the count median diameter(CMD), particulate matter and soot particle number concentration efficiency. Applying pilot injection decreased the ignition delay of main injection fuel, the maximum pressure rise rate and the peak of heat release rate,which relieved the violence of main combustion. Selecting the pilot timing and pilot quantity reasonably can reduce NOx and soot emissions, and ensure that the THC and CO emissions will not be significantly increased. |
PDF Full Text Request