Design And CFD Analysis Of Components Of On-Board Refueling Vapor Recovery System

Gasoline vapor emission during vehicle refueling process is Volatile Organic Compounds'(VOCs)important sources.In order to reduce the hydrocarbon emission during the refueling process,the U.S.Environmental Protection Agency(EPA)regulated that the light-duty vehicles produced after 1998 must be equipped with On-Board Refueling Vapor Recovery System(ORVR),which can recycle 98% gasoline vapor produced dur ing the refueling process.Chinese vehicle emission regulations become increasingly stringent,and it plans to limit gasoline vapor emissions produced during refueling process,therefore the study of ORVR system is particularly important.In this dissertation,at first,vehicle gasoline evaporative emission regulations both inland and abroad were introduced based on a large number of literatures both inland and abroad.And the research status of ORVR system both inland and abroad was analyzed.Then refueling emission process of ORVR system was studied in the mathematical theory.The mathematical model of ORVR system's refueling emissions was established.MATLAB software was utilized to calculate the mathematical model.Results show that with the increase of air entrainment,fuel tank temperature and dispensing fuel Reid Vapor Pressure(RVP),the amount of vehicle's refueling evaporative emissions increase;with the increase of carbon canister working ability,the amount of vehicle refueling evaporative emissions decrease.Secondly,an unsteady gas-liquid two-phase numerical model of ORVR system was developed and simulated,utilizing fluid simulation software ANSYS Fluent and conbining VOF model and porous model.The results show that venting pipe diameter d,refueling velocity v,angle between filler gun mouth axis and filler pipe mouth axis ?,length of nozzle mouth inserted into the filler pipe L,height difference between filler pipe and tank bottom H have principal influence on refueling characteristics;the general influence factors include angle between the filler pipe and fuel tank ? and baffles installation.With the decrease of venting pipe diameter d,refueling process is smoother and it is easier to forming liquid seal in filler pipe.The fuel fluctua tion increases as the refueling velocity v increases;when the angle ? is 15°,the disturbance of fluid in filler pipe mouth is the smallest;as the increase of L,the fuel fluctuation in filler pipe mouth decreases;as the increase of H,the refueling smoothness decreases.Based on numerical and CFD analyzing results,the ORVR system of one model vehicle was designed.Especially,it elaborated operation principles,materials and important design parameters calculation of Filling Limited Venting Valve(FLVV),Gravity Venting Valve(GVV),Inlet Check Valve(ICV)and carbon canister.Finally,refueling emission characteristics test was carried on referring to national and business relevant standards,which was used to analyze the influences of fuel flow rate,the length of nozzle mouth inserted into the filler pipe,the angle between filler gun mouth axis and filler pipe mouth axis on vehicle refueling characteristics.Test Results validate that the ORVR designed in this paper meets the national vehilcle emission standard.