【作者】 焦磊；

【导师】 王乐勤；

【作者基本信息】 浙江大学 ， 化工过程机械， 2005， 博士

【摘要】 本文以用于原油底泥清理的连续射流和脉冲射流为研究对象,围绕射流清洗过程中的冲击射流流动及自激脉冲射流在发生装置内的湍流流动,对自激脉冲射流的发生机理及射流冲击靶物的流动特性进行理论分析和试验研究。 通过对冲击射流内各区域流动特性的分析,给出了圆形冲击射流冲击区的范围,从喷嘴出口条件入手,导出了壁面射流区中壁面切应力和径向速度的沿程分布关系式,该式反应了壁面射流场对初始条件的依赖。 推导了轴对称坐标下冲击射流势流区域的湍流时均方程,考虑冲击区流线强曲率变化的影响,对湍动能和能量耗散率方程进行修正,给出了改进的湍流模型,并将其应用于冲击射流的数值计算,得到与试验相一致的结果。根据计算结果探讨了冲击高度和喷嘴出口雷诺数对冲击射流中环形回流区的影响,得到了环形回流中心随冲击高度和喷嘴出口雷诺数的变化规律。 通过对冲击射流湍流边界层的研究,给出了边界层的动量方程和能量方程,分析了边界层厚度的特点,应用轴对称坐标系,提出了边界层方程的求解方法。 利用双流体模型推导了非定常空化模型的控制方程,讨论了方程离散化、坐标变换、液汽两相流SIMPLE解法等问题,论述了利用气体密度分数进行相间压力分摊的必要性,并结合改进的空化模型对典型工况的自激脉冲射流进行数值模拟,揭示了自激脉冲射流发生机理。 通过自激脉冲射流和连续射流的喷射性能试验,分析了脉冲射流打击力的脉动特性,推导了最大打击力的经验计算式,总结了打击力水平较高的自激喷嘴结构及运行参数的优化配比范围。 通过连续射流和自激脉冲射流打击油泥的试验,测得了油泥样本屈服时的最小打击力,并以此作为依据推导了连续射流射程的计算式。更多还原

【Abstract】 The solid jet and pulsed jet applied to clean crude oil sludge are investigated in this paper, the movement performance of a jet directed to impinge against a wall and the self-excited pulsed jet flow mechanism and its experimental test method are studied according to the impinging jet and the turbulent flow in self-excited pulsed jet device.The flow property in all of the impinging jet area is analyzed to indicate the extension of impingement region. The shear stress and radial velocity distribution is derived from initial condition at the nozzle to show that the wall depends on the initial condition at the nozzle.The potential turbulent equation in the impinging jet is established as a function of flow stream rotation and curvature, the standard turbulent model is improved by modifying the kinetic energy and the dissipation equation, which is applied to compute the impinging jet and the computation result is consistent with the experiment. The movement characteristics of the center of the toroid as Jet-to-target plate spacing or the Reynolds number at nozzle is mappedBy employing axisymmetric coordinate, the momentum and energy equations based on the impingement wall layer are established to compute the hydraulic profit.The numerical theory of unsteady cavitations has been set up by studying the two-fluid model of liquid and vapor. The control equations are put forward and the method of equations segregating, the mesh grid transformation and SIMPLE for two-phase fluid are discussed. The method of sharing pressure by mass fraction is discussed, which is applied to improve cavitations model for numerical simulation on self-excited pulsed jet. The mechanism of the self-excited pulse is described through dividing the pressure zone, velocity and the volume fraction zone.The stagnation pressure of pulsed jet is discussed according to the experiment of self-excited pulsed jet. The computational formulate of maximum stagnation pressure is obtained from experimental result. The optimal range of structural and operate parameters are summarized.The minimum hitting force is measured when oil sludge yielding in the experiment of solid jet and pulsed jet impinging against oil sludge, and the computational formulate of jet range is derived from experimental result.更多还原