Experimental Research On Reducing Emission With EGR On DME-Diesel Mixed Fuel Engine

DME with its special physical and chemical properties can achieve efficient and low polluting combustion, and has gained extensive attention.In this thesis, combustion test of DME and diesel fuel are carried on 4100QBZL diesel engine which are designed specially, and exhaust gas recirculation technology is applied to reduce the harmful exhaust emissions furtherly,moreover comprehensive performance is analysed deeply.This thesis discusses DME with medium and low proportion and diesel mixed fuel (D30, D40, D50) burn on 4100QBZL type engine when the oil supply system has been redesigned.After comparison, the D40 mixed fuel is selected, and the matching optimization of fuel injection parameters is made . In this thesis,EGR system which is suitable to 4100QBZL diesel engine is established,including selection, design, cooling,and installation ,the influence of different EGR rate on combustion and emissions of D40 mixed fuel engine is studied. After comprehensive comparison, better EGR rate is selected , then test is carried again and compared with the original machine.The results showed that: in all operating conditions, after applying EGR system on D40 mixed fuel engine, when the EGR rate increases, the peak value of cylinder combustion pressure will reduce, position of the pressure peak will delay,Compared with the original diesel engine, the basic dynamic can be guaranteed, the appropriate amount of EGR can improve the economic efficiency at low load, and at high load EGR may increase fuel consumption rate, but economic will deteriorate; HC emissions and CO emissions will increase compared with the original diesel engine, the overall emission level is still low; NOx emissions and PM emissions have been effectively controlled, emissions will reduce obviously.Thus, DME-diesel blends fueled on the turbocharged diesel engine with EGR technology, it can not only improve the application ratio of DME and reduce fossil fuel consumption, but also has the important theoretical and practical significance to reduce emissions of the diesel engine, which is suited to China's basic national conditions, and it also helps to alleviate China's ever increasing pressure on energy supply and environmental pollution.