车载加油油气回收系统中气液两相流动特性的实验和数值模拟

合理分析车载加油油气回收系统(ORVR)内气液两相的流动特性对油气排放控制技术的实施具有重要意义。以ORVR加油系统为对象,采用高速摄像、粒子动态分析仪(PDA)实验测量和CFD数值模拟相结合的方法,对ORVR车辆加油过程中的气液两相流动特性进行了系统研究,讨论了加油量对加油管内流场和压力场的影响。结果表明,随着加油速度的增大,加油管口的射流卷吸增强,气液两相流动过程中的湍流程度加剧,液流冲击与破碎严重,涡旋现象明显；随着加油速度的增大,气液掺混严重,液体自由表面边界逐渐模糊；加油过程中加油管和燃油箱内气相压力的变化分为2个阶段:开始加油时气相压力迅速增大,在5~8 s内达到峰值；然后气相压力逐渐减小,最终趋于稳定。

Experiment and numerical simulation of gas-liquid two phase flow in on-board refueling vapor recovery system

An analysis of the gas-liquid two-phase flow in on-board refueling vapor recovery (ORVR) system is of great importance to implement the evaporation emissions control technology.The flow characteristic of gas-liquid two phase of ORVR was investigated using the research methods, such as numerical simulation and experimental measurement with particle doppler dynamic analyzer (PDA) and high-speed camera. The results of influence of refueling velocity show that with the increasing of refueling velocity, the jet entrainment near the pipe inlet increases and the flow turbulence is intensified. At the same time, the increased refueling velocity makes serious fluid impingement and breakage, inducing the more obvious vortex phenomenon. In addition, as the refueling velocity increases, the gas-liquid mixing is increased and the free surface of liquid is gradually blurred. The change of vapor pressure comes in two stages in both refueling pipe and fuel tank. At beginning, the gas pressure increases rapidly and reaches peak within 5 to 8 seconds. Then the gas pressure decreases and becomes stable in the end.