Emission Optimization And Control Of Biodiesel Engine By Miller Cycle

Energy crisis and environmental pollution are two major problems that becoming more and more obvious.As a kind of renewable and environment-friendly fuel,biodiesel has become a hot topic in various countries.At the same time,it is not uncommon to see the phenomenon of waste cooking oil returns back to table in recent years,that brings great harm to human’s health.The development of waste cooking oil diesel not only ensure national energy security and reduce emission pollution,but also is an effective way to turn waste oil into treasure.In this paper,4JB1 diesel engine is used as the research object to analyze the influence of different volume ratio of blended fuel on the power,economy and emission of diesel engine.Study found torque deteriorate and NO_x emission significantly increase with blended fuel.In order to ensure the torque,this paper selected the volume ratio of 30%blended fuel(B30 for short)for study,and use the Miller cycle-early Intake-valve closing to control and optimize emissions of biodiesel fuel under the condition of constant torque.First of all,compared the effects of the original machine with two kinds of Miller cycle,Vary CAM Timing was chosen to combine with waste oil biodiesel.In high and medium speed,chose the intake valve close angle to make NO_x and Soot emissions with B30 close to pure diesel emissions under different load.Due to the control effect is not ideal under low speed,combined variable turbo section supercharger(VGT)with Miller cycle to achieve multi-objective optimization with DOE test design.Research shows that:(1)Under the premise that no adjustment with structure of diesel engine,the maximum engine torque reduces by 6.2%with blended fuel in 40%volume ratio.Under 25%load,fuel consumption rate showing strongest growth at 12.7%,NOx emission increases by 27.7%,Soot emission decreases by 40%.(2)Under the maximum torque point,with the decreasing of the intake valve close angle,two kinds of Miller cycle have almost the same change trend.While,Vary Valve Overlap Miller cycle was more obvious.When the intake valve close Angle is 60°CA,torque with Vary Valve Overlap Miller cycle began to deteriorate.At this time,NO_x concentration with the Vary Valve Overlap Miller cycle and the Vary CAM Timing Miller cycle reduced by 83.7%and 83.7%respectively.(3)Without affecting the torque,chose the intake valve close angle to make NO_x emission and Soot emission with B30 is roughly equal to pure diesel emissions under medium and high speed.(4)Using B30 under the low speed with 100%and 50%load.When the intake valve close angles are 98°CA and 85°CA;VGT valve angles are 0.25 and 0.16,the Objective function value is optimal,NO_x emission decreased by 23.17%and 8.2%than the former.Though Soot emission has increased,but still be roughly equal to pure diesel’s Soot emission.