中文摘要：

采用数字粒子图像测速技术（DPIV）对二甲醚（DME）瞬态喷雾的速度场进行了测量,获得了DME瞬态喷雾的内部微细结构、速度矢与涡量分布等信息,并探讨了启喷压力、喷孔直径、环境压力等参数对喷雾速度场的影响规律。试验结果表明：任一喷雾断面的轴向速度以轴心处为最大,向外沿径向逐渐减小,基本呈对称分布;喷雾轴心速度随喷雾贯穿距离的增大而不断减小,且喷孔直径越小、环境压力越大,其轴向速度衰减率越大,而启喷压力对轴向速度衰减率影响不大;启喷压力、喷孔直径、环境压力对喷雾发展的稳定性、液滴尺寸和速度矢的空间分布均匀性,以及喷雾发展的形态等均具较大影响。数据分析发现,DME喷雾断面的速度分布具有自模性,并据此提出了DME喷雾速度的无因次分布数学表达式。

英文摘要：

This paper presented an experimental study on the transient spray velocity field of dimethyl ether （DME） by digital particle image velocimetry （DPIV）. The microscopic structures of DME spray were visualized and the information about velocity vector and vorticity were obtained. The experimental results reveal that the fuel velocity at the centerline decreases with the increase of the spray penetration. The velocity distribution at any spray cross section is basically symmetric in the radial direction. The highest fuel velocity occurs at the centerline and the fuel velocity gradually decreases toward the periphery of the spray. The development of spray tends to be unstable with the increase of injection pressure, nozzle hole diameter is and back pressure. The smaller the nozzle hole diameter is and the larger the back pressure is, the faster the decline rate of spray centerline velocity is. The injection pressure has an insignificant effect on the decline rate of spray centerline velocity. At the spray front the interactions between spray and ambient air become inten- sive and forms mushroom-like spray tip when the back pressure is larger. The DME spray is in good agreement with the turbulent free jet in respect of the dimensionless profile of analogue distribution of velocity. A new dimensionless profile of velocity was developed for DME fuel spray.