Control And Optimization Methodology For On-board Refueling Vapor Recovery System Of Hybrid Electric Vehicles

Vehicular evaporative emissions are an important source of volatile organic compounds(VOCs).Moreover,the plug-in hybrid electric vehicles(PHEVs)may run as electric vehicles(EVs)under charge depleting(CD)mode for a long time.The shutdown of engine causes that the activated carbon canisters may not purge well in-use and to become saturated with fuel vapor.Therefore,the problems of evaporative emissions and refueling emissions of PHEVs are still severe.The new emission regulation(CHINA 6)reduces the limits of evaporative emissions and adds the limit of refueling emissions.Particularly,the measurement methods for refueling emissions from HEV have been added to the new emission regulation(CHINA 6).So the problem of evaporative emissions and refueling emissions from PHEVs deserves attention.Firstly,the structure of onboard vapor refueling recovery(ORVR)system of PHEVs has been introduced.The generation mechanism of refueling emissions from PHEV has been researched.The mathematical models of refueling emissions during depressurization stage and refueling stage have been built based on the ideal gas law and molecular diffusion theory.Moreover,the calculation results of the refueling emissions from PHEVs have been obtained.Secondly,the numerical simulation models of refueling emissions from PHEVs during depressurization stage and refueling stage have been established,respectively.The numerical simulation models of refueling emissions from PHEVs during depressurization stage and refueling stage have been validated by experiment.The simulation results show the excellent agreement with experiment results.The simulation results of refueling emissions have been obtained.Moreover,the refueling emissions under different dispensing rate were studied.Thirdly,the structural parameters of ORVR that affect the refueling emissions from PHEVs have been analyzed.The test plan was determined based on the Box-Behnken test design method,and the results of refueling emissions were obtained through numerical simulation.The response surface model between the refueling emissions and the structural parameters was built.The structural parameters of ORVR were optimized based on the genetic algorithm.Moreover,the refueling pre-shutoff was checked.Fourthly,the control methods of ORVR of PHEVs were introduced.The generation mechanism of evaporative emissions from PHEVs when they are not refueling was researched.The control strategy of fuel tank isolation valve(FTIV)has been established.The control strategy was built to reduce the emissions when the FTIV opens to release the fuel vapor.Finally,the refueling emissions tests of ORVR of PHEV have been conducted following the test procedures specified in the new emission regulation(CHINA 6).The validity of the mathematical model and numerical model were further verified by comparing the experimental results with the mathematical model results and numerical simulation results,respectively.