Comparative analysis of emission characteristics between LLC cycle and other transient cycles based on heavy-duty diesel engine
Low load conditions of urban vehicles account for a large proportion of real-world driving situations,but they are easily overlooked.To further investigate the differences in emission characteristics between Low Load Cycles(LLC)and other cycles,emission tests on the engine bench using a heavy-duty diesel engine were conducted.At first,LLC,World Harmonized Transient Cycle(WHTC),and China Heavy-duty Transient Cycle(CHTC)tests were performed one by one.Engine speed and torque were measured by a dynamometer.Volume fractions of NOx,Hydrocarbon(HC),and CO were measured through a direct emission analyzer.Emission factors of PN were measured by a Particulate Number(PN)counter.Secondly,the specific emission values were calculated according to the method described in the China Ⅵ standard.Then,speed-torque distribution characteristics,load distribution patterns,and differences in specific emission results of the three cycles mentioned above were compared.Additionally,after selecting data points for high-emission conditions,the high-emission condition distribution characteristics of the above cycles were analyzed.Finally,the emission characteristics of the LLC cycle under cold and hot start conditions were compared.The results show that when the engine runs LLC cycle,the data points in idle speed and 1 600-2 200 r/min below 400 N·m are more distributed than those in other cycles,and the distribution of load range of 0-5％is higher.The NOx-specific emission result of the hot LLC cycle is 1 572.13 mg/(kW·h),and the requirements for NOx emissions are more strictly under the LLC cycle and CHTC cycle conditions.The overall exhaust temperature of the LLC cycle is relatively low.The cold start conditions result in a particularly significant increase in NOx emissions under low load and low-speed range.The high PN emissions of LLC and CHTC cycles mainly occur in the 0-10％load range,while the CHTC cycle also has high emission peaks in the 50％-60％load range,and the overall distribution of PN high emissions in the WHTC cycle is relatively average.The low exhaust temperature of the LLC cycle harms the Selective Catalytic Reduction(SCR)conversion efficiency,and it further intensifies under cold start conditions,resulting in the NOx emission level of the LLC cycle far exceeding the level of the WHTC and CHTC cycles.
environmental engineeringdiesel engineLow Load Cycle(LLC)transient cyclenitrogen oxidesparticulate number
万方数据
维普
