瞬变工况下管阀组件内部不稳定流动特性研究

The pipeline-valve component, including the process valve and its upstream and downstream pipelines, possesses the functions of fluid control and transportation in process industry. Under transient operating conditions, rapid-varying and high-shearing flow can be produced easily in the pipeline-valve component and lead to unstable flow which affect the reliability of valve operation. Besides, evolution of the unstable flow along the pipeline would increase the difficulty in locating the stable signals for flow metering and consequently influence the accuracy of that..This project will combine theoretical analysis, numerical simulation and experimental investigation. Characteristics of the turbulent flow in the component under transient operating conditions are analyzed. A LES numerical method of considering nonlinear velocity gradient and helicity in dynamic SGS model is established to obtain accurate information of flow field. The evolution law of vortex flow is analyzed, and the energy gradient method for characterizing the stability of internal flow is established. The laws of spatial distribution and parametric correlation of internal energy gradient function and external dynamic pressure signals along the pipeline are studied. A method for judging the stable development of flow is built on the correlation of internal and external characteristics. A dimensionless criterion is proposed for predicting the characteristic length of the unstable flow evolving to the stable flow under all transient operating conditions. Finally, this project provides the theoretical support for the design and application of fluid engineering equipment such as the process valve and flowmeter.

管阀组件包含流程阀门及其上下游管道部件，承载着流程工业中流体控制与输导功能。瞬变工况下的管阀组件内部极易产生急变流与高剪切流导致的不稳定流动，影响阀门运行的可靠性。此外，该不稳定流动会沿管道发展，给采集稳定流体计量信号的定位增加了难度，从而制约着流体的准确计量。.本项目拟结合理论分析、数值模拟和实验研究，分析瞬变工况下管阀组件内部的湍流流动特征，确立考虑非线性速度梯度与螺旋度影响的动态亚格子应力模式下的LES数值计算方法，从而获得高精度全流场信息，分析漩涡流场演变规律，建立管阀组件内部流动稳定性的能量梯度表征方法,研究内部能量梯度函数与外部沿程动态压力信息的空间分布规律及其参数化关联，构建流场内、外特性相关联的流动稳定发展判定方法，提出全工况下不稳定流动发展至稳定流动的特征长度无量纲化预估准则，最终为流程阀门和流量计等流体工程装备的设计开发与工程应用提供理论支撑。

阀门调控作用下，管阀组件内部极易出现不稳定流动并沿下游发展，影响管道流体计量稳定信号的采集，从而制约着流体的准确计量。针对该关键工程问题，本项目通过理论分析、数值模拟和实验研究，开展阀门调控作用下管阀组件内部不稳定流动特性研究。基于阀门调控作用下的管阀组件内部湍流流动特征，建立了适用于阀门调控作用下的DES湍流数值计算模型，开展了瞬态工况下管阀组件内部流动特性的准确数值计算，分析了基于速度分布特征的蝶阀结构参数对管阀组件内部不稳定流动特性的影响。针对不同调控方式，总结了稳态和瞬态调控作用下管阀组件内部速度、压力、涡量等流场信息的时空演变规律，揭示了管阀组件内部偏心射流沿程发展规律，提出了速度偏心率及湍动能变化率的流动稳定性参数化表征方法，获得了全工况下不稳定流动至稳定流动的发展管道长度的预估准则。搭建了管阀组件外部流体计量信号采集实验，分析了阀门调控工况、安装位置及阀后发展管道长度对流体计量外特性的影响，揭示了阀门调控作用下内部流体压缩性对流体计量特征频率的影响机理，构建了流场涡量值与流体计量特征频率之间的指数关联，最终为流程阀门和流量计等流体工程装备的设计开发与工程应用提供理论支撑。通过本项目的实施，共发表SCI期刊论文6篇，培养毕业硕士研究生5名。