| Energy crisis and environmental pollution are two major problems faced by the society at present,while finding renewable energy is an effective way to solve these two problems.Therefore,the combustion and emission characteristics of the diesel engine fueled with iso-butanol and biodiesel blends are investigated by means of the combination of experimental and numerical simulation from the perspective of fuel design in this study.Firstly,blended fuels with different iso-butanol blending ratios(IB0,IB10,IB20,and IB30)were investigated on a diesel engine under different engine loads,fuel injection timings and EGR ratios.Results indicated that(1)the addition of iso-butanol could prolong the ignition delay and shorten the combustion duration.The combustion of IB30 would deteriorate when the fuel injection timing was 2.5°CA BTDC.At 1.13 MPa engine load,the addition of iso-butanol could increase the brake thermal efficiency and reduce the brake specific fuel consumption.(2)iso-butanol addition could reduce CO emissions of the diesel engine and increase NOx emissions when the engine loads higher than 0.13 MPa.While HC emissions would increase with the rise of iso-butanol blending ratio under the entire engine load condition.In addition,EGR could reduce NOx emissions significantly but increase HC and CO emissions.(3)1,3-butadiene was raised gradually with the rise of iso-butanol blending ratio when the engine load was 0.13 MPa.Iso-butanol addition could reduce benzene emission but increase acetaldehyde emission.With the rise of EGR ratio,1,3-butadiene and acetaldehyde emissions were decreased first and then increased gradually,while the benzene emission was increasing gradually.Besides,acetaldehyde emission was impacted greatly by the EGR ratio.(4)Iso-butanol addition could reduce accumulate mode particle concentration,the geometric mean diameter of the particle and the particulate mass concentration,but the nucleation mode particle emissions were increased.The nucleation mode concentration of particle would decrease under the influence of EGR,while the accumulation mode concentration of particle and particulate mass concentration would increase.Secondly,the numerical simulation of premixed low-temperature combustion of IB0 and IB20 was calculated by AVL-Fire software.The simulation results showed that the in-cylinder pressure and the mean temperature of IB0 and IB20 would increase sharply under the premixed low-temperature combustion mode,the peak in-cylinder pressure and the mean combustion temperature would decrease with the rise of EGR ratio.The emission of NO pollutants and the peak of Soot concentration decreased significantly under the higher EGR ratio,while CO pollutants increased significantly.Under the premixed low-temperature combustion mode,it was found that the post-injection strategy could improve the in-cylinder pressure and the mean temperature in the later combustion period.The in-cylinder pressure and the mean temperature in the later combustion period would decrease gradually with the post-injection timing away from top dead center.CO and NO emissions could be reduced by post-injection strategy,but the peak of Soot concentration would be increased.In addition,the peak of Soot concentration would be increased gradually as the post-injection timing was away from the top dead center.The combustion and emission characteristics of iso-butanol/biodiesel blends were made a deep research through the method of the combination of experimental and numerical calculation,which provide a reference for the application of iso-butanol/biodiesel blends on the diesel engine. |
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