Biodiesel effects on transient needle motion and near-exit flow characteristics of a high-pressure diesel injector
Biodiesel effects on transient needle motion and near-exit flow characteristics of a high-pressure diesel injector
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DOI：
10.1177/1468087413497951
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发表时间：
2014-06
影响因子：
2.5
通讯作者：
S. Moon;Taku Tsujimura;Yuan Gao;Suhan Park;Jin Wang;N. Kurimoto;Y. Nishijima;M. Oguma
中科院分区：
文献类型：
--
作者：
S. Moon;Taku Tsujimura;Yuan Gao;Suhan Park;Jin Wang;N. Kurimoto;Y. Nishijima;M. Oguma
在研究中，生物柴油的瞬态针运动和近出口流动特性的单孔高压柴油喷油器的影响进行了研究，针升程，针速度，出口速度和近出口流动结构在不同的喷射压力。本文利用超快X射线相衬成像技术分析了喷针的瞬态运动和近出口流动特性。高能亚纳秒X射线脉冲具有可视化喷嘴内的针状物和近出口密集超音速流的潜力，其速度达到600 m/s以上。无论燃料、喷射条件和喷射器类型如何，都可以通过对x射线图像的加工分析来获得瞬态针阀运动以及近出口超音速流的结构和速度。生物柴油的高体积模量和粘度通常会减慢针运动并降低流动性能。在打开瞬态，急剧增加和随后的超调针速度和出口速度观察到的喷雾宽度的同时增加。生物柴油的针速，出口速度和喷雾宽度的增加较慢，但在打开瞬态的速度超调程度较高。稳态时，生物柴油的湍流结构和喷雾宽度均小于柴油。在关闭瞬态过程中，针速的突然增加和出口速度的降低，同时观察到喷雾宽度的增加。在相同的激励脉冲宽度下，生物柴油的关闭过渡过程开始延迟，总喷射持续时间较长。在大约低于100 MPa的低喷射压力下，生物柴油和柴油之间的差异变得微不足道。
In this study, biodiesel effects on transient needle motion and near-exit flow characteristics of a single-orifice high-pressure diesel injector were investigated in terms of needle-lift, needle speed, exit velocity and near-exit flow structure under various injection pressures. Ultrafast x-ray phase-contrast imaging technique was employed in this study to analyze the transient needle motion and near-exit flow characteristics. High-energy sub-nanosecond x-ray pulses have a potential to visualize the needle inside the nozzle and near-exit dense supersonic flow which speed reaches over 600 m/s. Transient needle motion and the structure and velocity of near-exit supersonic flows can be obtained by fabricated analysis of the x-ray images regardless of fuel, injection condition and type of injector. High bulk modulus and viscosity of biodiesel normally slow down the needle movement and decrease the flow performance. During opening-transient, sharp increase and following overshoot in needle speed and exit velocity were observed with a concurrent increase in spray width. The biodiesel showed a slower increase in needle speed, exit velocity and spray width but a higher degree of velocity overshoot during opening-transient. At steady-state, the biodiesel showed less turbulent flow structure and smaller spray width than diesel. During closing-transient, an abrupt increase in needle speed and decrease in exit velocity were observed with a concurrent increase in spray width. The biodiesel showed the retarded start of closing-transient and longer total injection duration under same energizing pulse duration. The difference between biodiesel and diesel became insignificant at low injection pressures roughly below 100 MPa.