Study On Flow Mechanism And Characteristic Of ORVR Vehicle Refueling Process

The Onboard Refueling Vapor Recovery technology(ORVR), which is based on vehicle emission control technology for oil and gas, has been over 20 years since it was brought out by Environmental Protection Agency(EPA) in 1994. As China's growing number of motor vehicles, the control of motor vehicle emissions is urgent, while ORVR technology is gradually aroused people's attention. However, the study of ORVR technology has just been started in China and thus the related theories and references as well as data are very limited. Based on this background, the ORVR fuel system model was used in this paper, made a systematic research on gas-liquid two phase flow during refuelling process of ORVR fuel fill system, research methods including parameter analysis, numerical simulation and experimental measurement, and also assisted with equipment like Particle Dynamic Analyzer(PDA) and high rate camera.A lumped parameter model covering filler pipe, fuel tank and vent valve was established, partitioning it into four controllers and two valves. It also discusses geometric structure of fueling system, fuel flow rate of fuel nozzle, fuel evaporation and how the ratio of air and fuel vapor in the fuel tank impacts pressure, successfully estimating the pressure variation of the gas-phase space in the filler pipe and fuel tank while the fueling system is fueling up.Then, a numerical simulation analysis on filler pipe and ORVR fueling system at full scale, utilizing ANSYS FLUENT, was conducted, a Computational Fluid Dynamics application. On basis of that, this thesis systematically studies the various cases while fueling up, which helps to discover the impacts of fueling rate, inner diameter of filler pipe and back pressure of vent valve on gas-liquid two-phase flow, and the cases include liquid seal, back flow and flow field of filler pipe, air entrainment around the filler pipe mouth, and pressure variation of gas-phase space in fuel tank. And use the PDA to measure the flow field of filler pipe, the test results consistent with the numerical simulation and verify the reliability of the use of CFD numerical models.Considering that the refueling of an motor vehicle is a transient process, a visualized experiment platform composed of quartz glass filler pipe at 1:1 scale and polymethyl methacrylate fuel tank was established, in order to dig into the complicated gas-liquid two-phase flow research. Facilitated with PDA and high rate camera, it measures the velocity flow field in filler pipe, pressure variation around the filler pipe mouth and the head space of fuel tank. With these experiments, the observations that the transaction from laminar flow to turbulent flow, the process of vortex motion circling the pipe axis, air entrainment and the mixture of air and liquid have been available.The research results of this paper explain the formation of liquid seal of filler pipe and also reveal the flow features and pressure variations of ORVR system during refueling, which might offer reliable data for further independent researches on ORVR system in China.