预存气体闭端管路的充填水击研究

Investigation on Water Hammer During Filling Process of Closed Conduit with Entrapped Air

关键词:  预存气体  闭端管路  充填  水击  压力震荡  参数模型

Key words:  Entrapped air  Closed conduit  Filling  Water hammer  Pressure oscillation  Parameter model

摘要:

为提升补燃循环发动机仿真平台的分布参数计算能力，针对常温液体充填预存气体闭端管路的水击现象，使用Modelica语言基于MWorks平台建立了一维有限体积的管路充填模型，并分别使用该模型和集中参数模型对现有文献中的充填水击实验进行了仿真模拟。结果表明：对于预存气体0.1MPa的工况下，一维有限体积模型与集中参数模型对实验的模拟度均较为接近；而在管路接近真空的工况下，一维有限体积模型的计算结果与实验数据吻合度很高，集中参数模型误差则高达76%左右。在不同预存气体压力下的计算结果表明：在管路刚度一定、预存气体压力在0.1MPa以下时，气体的压缩缓冲作用是充填过程中水击压力峰值得以减弱的主要原因；当预存气体压力在0.1MPa以上时，气体的缓冲作用与充填流量的减小共同导致了充填水击压力峰值的减弱。对不同弹性管路的计算表明：在闭端管路的充填过程中，管壁弹性对近真空管路的影响相对较大，对预存气体压力较大的管路几乎没有影响。

Abstract:

To improve the capability of distributed parameter modeling of a staged combustion cycle engine simulation platform， a one-dimensional finite volume model was developed to simulate the water hammer of the normal temperature fluid during the filling process of closed conduit with entrapped air. In the present work， the model was programmed by Modelica on MWorks platform， and utilized to simulate several experiments in literatures with comparison of lumped method. The results show that both one-dimensional finite volume model and lumped model have a good agreement with experimental data in the case of 0.1MPa pressure gas in the closed conduit， but in vacuum case one-dimensional finite volume model simulates experiments more accurately while the error of lumped model reaches to about 76%. Under the condition of the given pipeline stiffness， the results for different pre-pressurized pipelines indicate that the cushion effect of gas plays a major role in reducing the water hammer pressure during the filling process when the pressure of entrapped air is less than 0.1MPa. With the exception of cushion effect of gas， the decrease of mass flow rate starts to weaken the peak pressure when the pressure of entrapped air is more than 0.1MPa. The simulations for different elastic pipes indicate that the elasticity has a relatively large impact on water hammer in vacuum case while nearly no impact in higher pressure cases.