Research On The Effect Of PODE Blending Ratio On Diesel Engine Performance And DOC+CDPF+SCR Aftertreatment System

Due to the common requirements for energy security,energy diversity,and sustainable development,biomass fuel has attracted more attention from the public and scholars than ever before.However,the application of polymethoxy dimethyl ether(PODE) as a new fuel in diesel engines and its impact on after-treatment systems of diesel engine is not as extensive as methanol,n-butanol,dimethyl ether and biodiesel.DOC+CDPF+SCR is one of the diesel engine after-treatment technologies required by China VI regulations.Studying the effect of PODE on the performance and action mechanism of DOC,CDPF,SCR and other after-treatment systems has important practical significance for the popularization and application of this biomass oxygenated fuel.In addition,with the further tightening of emission regulations in the future,the application of clean biomass-oxygenated fuel coupled after-treatment technology is one of the feasible purification strategies of internal combustion engines.In this paper,a D30 high-pressure common rail diesel engine is used as the research model,a DOC+CDPF after-treatment device is installed,a test bench is set up,and PODE/diesel blended fuels with different PODE blending ratios are formulated(the volume fraction of PODE is recorded as P0,P10,P20,and P30 from 0%to 30%,respectively).Engine bench tests and one-dimensional numerical simulation techniques were used to study the effects of PODE blending ratio on diesel engine performance and DOC+CDPF+SCR after-treatment system performance.The power,fuel economy,and emission characteristics of a diesel engine using PODE/diesel blended fuel are studied.The results show that the blending of PODE can improve the brake thermal efficiency(BTE)of the diesel engine at low speed and heavy load conditions.For example,when using P30 at 1000 r/min,the BTE is about2.1%higher than P0.However,due to the lower heating value of PODE,the higher the PODE blending ratio,the higher the brake specific fuel consumption under the same torque output.In addition,blending PODE in diesel can significantly reduce CO emissions at low speeds,but increase CO emissions at high speeds.In the medium and low speed high load conditions,when the PODE blending is relatively high,the specific emissions of NOx and HC will increase significantly.Under the full-load conditions of 1800 r/min,the specific NOx emissions when using P10,P20,and P30are about 13.3%,22.2%,and 40.0%higher than P0,respectively.The DOC+CDPF conversion efficiency,temperature rise,and pressure drop characteristics of diesel engine using PODE/diesel blended fuel are studied.The results show that the overall conversion efficiency of DOC+CDPF to CO is close to 100%under the full-load conditions.However,when P30 is used,the conversion efficiency of DOC to CO is low at a low speed range,about 54.5%.In the low speed range,the temperature rise of DOC and CDPF is not obvious when P0 is used,and the temperature rise of DOC and CDPF is obvious when P10 and P20 are used.When P30is used,the temperature rise of DOC and CDPF is between P20 and P0.The load characteristic test shows that under low load conditions,when P0 and P10 are used,the concentration of NO₂ in the back end of the DOC is higher,and the DOC and CDPF are significantly heated.When P20 and P30 are used,because the soot accumulation in the CDPF carrier is less,the temperature rise is smaller.When P30 is used,the average exhaust pressure before CDPF is 0.3 to 0.5 k Pa lower than when P0 is used,indicating that the blending of PODE effectively reduces PM emissions for diesel engines.One-dimensional simulation was used,and the SCR conversion efficiency of diesel engine using PODE/diesel blended fuel was studied.The results show that when P10 is used,the SCR conversion efficiency can be similar to that when P0 is used.While at low load of 2400 r/min,the SCR conversion efficiency of the P10 is only about one-third of the P0 due to the lower exhaust temperature.P20 and P30 have low exhaust temperature at low load and high speed conditions,and the NO₂/NOx ratio is less than 7%,so the SCR conversion efficiency is less than 40%.At high speed and low load conditions,the SCR conversion efficiency of P0 and P10 increased from 60.8%and 22.9%to 81.9%and 40.9%by increasing the cell density and total length of the SCR carrier.However,when P20 and P30 are used,because of the lower exhaust temperatures,the optimization of the structural of the SCR carrier has only a limited effect on improving the SCR conversion efficiency.