水力瞬变仿真中混油界面位置的确定

在顺序输油管道中,混油界面的位置不断发生变化,水击波速等油品物性参数值在管道沿线的分布也随之变化。为了准确地确定瞬态流动时混油界面的位置,及时改变界面上游油品的物性,更真实地仿真水力瞬变过程,提出基于水击特征线法的混油界面位置阶梯推进法。结合x-t网格图,介绍了阶梯推进法的原理。归纳出混油界面网格跨越的6种组合类型,并给出了基于特征线法的阶梯推进法的计算流程。通过计算实例分析,认为对于仿真时间较短,时步较长,混油界面附近的稳态和瞬态平均流速以及两种介质水击波速的差异不是很大时,如果不关心混油界面的真实位置,可以根据稳态流速确定混油界面位置;当仿真中混油界面可能经过对界面位置较为敏感的边界时,必须用瞬态流速计算混油界面的位置。

Determining the Location of Batching Interface in Hydraulic Transient Simulation

In batch pipelining,the location of batching interface is always variable and the physical property values of involved oil such as surge wave speed change along pipeline.In order to determine the location of batching interface in transient flow properly,update physical property values in time and simulate transient process more truly,ladder marching method for calculating the location of batching interface based on the method of water hammer characteristic was brought forward.Incorporating with x-t grid chart,the principle of ladder marching method was introduced.Six grid span types of batching interface were summarized and the computation procedure of ladder marching method based on characteristic method was given.Through analyzing example of calculation,it is concluded that in an usual simulation,the shorter the simulation time,the longer the time step and the difference between average steady-state flow velocity and transient one around batching interface is small,at the same the surge wave speed of one kind of oil doesn't differ greatly from the other's,the location of batching interface can be determined by the steady state flow velocity if the real location isn't be concerned with;when batching interface possibly passes through the boundary sensitive to the interface location,the location must be determined by transient flow velocity.