Study Of Recovery Theories And Methods About On-board Refueling Vapor Recovery System

With the increase of gasoline automobile population in recent years, fuel evaporative pollutant of gasoline automobile are increasing continuously. Facing with exhaustible oil resources and the increasing environmental pollution, the effective control methods of fuel evaporative emission pollutant from gasoline automobile are one of hotspots in today’s world.In this paper, the factors that affect gasoline evaporation and diffusion are studied. The refueling emission mechanism of gasoline automobile and mathematical models as well as key factors of controlling refueling emission are systematically analyzed by using molecular diffusion theory. Then, a type of refueling vapor recovery system and a test equipment of vehicle refueling emission have been designed separately, and some meaningful results are obtained by series of tests as follows:Firstly, the formative mechanism of refueling emission pollutant of gasoline automobile is researched based on the principle of molecular diffusion and mass transfer. After simplifying assumptions, mathematical model of refueling emission of gasoline automobile tank which only installed activated carbon canister is established. Then the quantitative analysis on refueling emission of automobile tank only installed activated carbon canister is undertaken by using computer simulation, and refueling emission from gasoline automobile tank only installed activated carbon canister is forecasted. Moreover, fuel evaporative pollutant control device of the activated carbon canister which can not control refueling emission for gasoline automobile, which is discussed.Secondly, in order to effectively control the refueling emission of gasoline automobile, not only the average temperature of fuel tank, dispensed fuel Reid Vapor Pressure and average temperature are analyzed, but also the amount of entrained air into fuel tank and the duration of waiting for refueling as well as other factors have been explored in depth, and then mathematical models are established. The results show that, the higher average temperature of fuel tank, dispensed fuel Reid Vapor Pressure and average temperature are, the more air enters into the tank, the greater refueling emission from gasoline vehicles is. However, these factors, such as the structure and shape of the fuel tank, refueling quantity and refueling speed etc, have little effect on refueling emission of dispensed fuel per unit volume. Under the action of the above-mentioned factors, the value of actual refueling emission from gasoline automobile is larger than that of experimental tests. Histogram analysis shows that the main factor affecting refueling emission of gasoline automobile is that the fuel tank port is not sealed during refueling, so oil-gas emitted directly into the atmosphere.Thirdly, the mathematical model of refueling emission of ORVR is established based on principle of mass transfer. On-board Refueling Vapor Recovery (ORVR) systems of mechanical and liquid seal-type are discussed separately. The existing problems, such as oil overfilled and spit-back during refueling etc, of present ORVR system of liquid seal-type are analyzed. The new control method of refueling emission is proposed, and a style of ORVR system is designed. The system includes flow control valve in the tank. It can reduce gradually oil-gas circulation area between tank and snorkel, and makes the gas mixture pressure in oil tank change smoothly, when the fuel tank will be filled up.Finally, a set of practical experimental equipments are designed for refueling emission of gasoline automobile, through analyzing the evaporative emission test equipments of domestic and overseas gasoline automobile. This experimental equipment consists of fuel and the ambient temperature testing devices, refueling and pumping matching devices and so on.Than a series of tests are performed.The experimental results verified that the technique of on-board refueling vapor recovery can prevent refueling vapor releasing directly to atmosphere, decrease refueling emission by 97%, and has favorable economic and social benefits, which is worthy of promotion and application.The followings are innovations of this thesis:1) The principle of step input is utilized for analyzing the amount of entrained air into fuel tank on refueling emission of gasoline atuomobile, and the corresponding mathematical model is established.2) The new control method of refueling emission is proposed and a style of ORVR system is designed.3) The new method of refueling emission test about automobile is put forward and a series of testing equipment of refueling emission of gasoline automobile is designed.This paper proposes design theories and methods of ORVR system, which provides a theoretical basis for the domestic development of ORVR system with independent intellectual property rights.