| With the energy crisis and environmental pollution problems have become increasingly prominent, the development of emission control technology and the development of alternative fuel received widespread attention. EGR technology was one of effective measures to reduce NOx emission of diesel engine. Biodiesel and bio ethanol was a renewable and clean fuel. Blend biodiesel and bioethanol and diesel into oxygenated biomass fuel (BED) which could reduce the particulate emission of diesel engine. EGR technology and oxy fuel technology, could give full play to the advantages of both to solve the problem of emission of diesel engine in plateau areas.Select an inline four cylinder turbocharged diesel engine as the test object. The effect laws of different EGR rate on fuel economy, power and emission characteristics on diesel engine which burning pure diesel fuel and B15E5 (hybrid fuel contains the volume ratio of biodiesel, 15% of 5% ethanol and 80% petrochemical diesel) were gained. According to the thirteen conditions, ESC test cycle, the pure diesel fuel and B15E5 diesel engine emissions of NOx and PM emissions were tested. The establishment of the engine on the basis of the experimental research model, the working process of diesel engine was simulated, considering the engine power, economy and emission characteristics, and ultimately determines the optimal rate of EGR under different working conditions. The conclusions are as follows:(1) Under 25%,50%and 75% load rate of the 2200r/min and 0%,6% ···24% EGR rate. Same EGR rate, diesel engine torque reduction, the fuel consumption rate increase, the engine torque was decreased gradually, the decline when fueled with B15E5 was 1.3%, 1.9% and 2.8% respectively, the decline when fueled with pure diesel fuel was 1.2%, 1.9% and 2.4% respectively; the effective rate of fuel consumption increased gradually, and B15E5 increased 9%, 3.7% and 5.3% respectively, pure diesel fuel in 14%, 3.6% and 4.8% respectively. Same EGR rate, engine fueled with B15E5 compared with fueled pure diesel, NOx emissions increase, smoke emission decrease; with the increase of EGR rate, NOx emission decreased gradually, the decline when fueled with B15E5 was 21.3% ,36.7% and 18.3% respectively,pure diesel fuel decreased by 21.3% ,40.3% and 17.9% respectively; the smoke emission increases gradually, using B15E5 were increased 61.5% ,700% and 100% respectively, pure diesel fuel were increased 46.7%,400% and 141.7%.(2) The load of 25% 2200r/min, increased EGR rate from 0% to 16%, the maximum combustion pressure and maximum combustion temperature decreased, the decline of pure diesel was bigger than B15E5, the trend was basically the same.(3)The ESC test cycle of diesel engine’s NOx and smoke emissions were tested, when EGR was turned off, the emission of NOx was 3.9g/kW·h, the PM emission was 0.07 g/kW·h fueled with B15E5, NOx emissions was 3.5g/kW·h, PM emission was 0.12 g/kW·h fueled with pure diesel; using EGR, NOx emissions were 3.6g/kW·h, PM emissions were 0.08 g/kW·h fueled with B15E5, NOx emissions were 3.4g/kW·h, PM emissions were 0.11 g/kW·h fueled with pure diesel. It need optimize the rate of EGR under the various conditions.(4) The simulation results show that:the rate of EGR has little effect on the diesel engine’s torque and fuel consumption rate; increased EGR rate, NOx emission decreased in the range of 31% to 64.3%, small load and moderate load smoke emissions slightly increase, the maximum was 83.9%, high load, increased EGR rate, smoke rose faster, the largest increase reaching 540%. Emission standard of reference, the State Ⅳ emission standard of PM changed from 0.02g/kW·h to 0.1g/kW·h, NOx to maintain 3.5g/kW·h constant, as the PM and NOx in this study in order to meet the demand of high emission standards; the power and economy of comprehensive consideration of diesel engine, and determined the optimum EGR rate of high environment conditions of diesel engine fueled with pure diesel and B15E5.
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