| Limits and measurement methods for emissions from light-duty vehicles(CHINA 6)has been issued in order to control the increase of gasoline automobile fuel evaporation population in recent years.With the increase of hybrid electric vehicles(HEV),it is urgent to research fuel vapor recovery technology of HEV and decrease the vapor emission.Firstly,in this paper,the features of HEV vapor recovery system have been studied.The working features and mechanism of HEV have important influence on the vapor recovery system,which have been stated systematically.The difference in onboard vapor recovery system between the HEV and conventional vehicles have been analyzed,on this basis,the new vapor recovery method has been researched and designed.Secondly,it has important impact on the reducing the refueling emission to research refueling vapor emission mechanism of HEV because of strict refueling emission standard of “CHINA 6”.So,simplify the refueling process and develop mathematical models of refueling emission for HEV based on molecular diffusion theory.What's more,the refueling emission process has been calculated by using MATLAB based on the mathematical models.Thirdly,purging carbon canister is the important part of vapor recovery system for HEV.The difference of vapor recovery system between HEV and conventional vehicles have been compared so that the principle of designing purging carbon canister has been summarized.The current purging methods have some drawbacks on account of analyzing two typical HEV purging models.On the basis of analysis,new HEV purging model has been researched.Finally,some important parts have been designed on account of resistance to high pressure and sealing of new vapor recovery system.Then the refueling emission test and evaporative emission test of HEV vapor recovery system have been conducted by using enterprise's test devices referring to “CHINA 6” standard.The refueling emission test results have been compared with refueling mathematical models calculation.Besides,in order to compare the HEV recovery system emission with conventional vehicles Onboard Refueling Vapor Recovery system(ORVR),the refueling emission test and evaporative emission test of ORVR also have been conducted.The test results shows that refueling emission and evaporative emission of new HEV vapor recovery system are far below the “CHINA 6” standards and also less than the ORVR emission,which indicates that the new HEV vapor recovery system has low emission and perfect effects.Furthermore,relative error between the test and calculation with the refueling time increasing.The followings are innovations of this thesis:(1)Analyze the HEV vapor recovery system mechanism and develop the new refueling emission mathematical model.The validity of mathematical model has been verified by conducting tests based on “CHINA 6” standards.(2)Design the new purging canister model and develop relative mathematical model,in the view of improving energy utilization efficiency for HEV,based on analysis of two typical purging canister model methods with some defect. |
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