水轮机筒阀动水关闭过程的水力特性分析

发布时间：2018-08-07 18:52

【摘要】：筒阀紧急动水关闭是保证水轮机安全运行的保护措施之一，本文主要以水轮机全流道为模型，数值模拟筒阀动水关闭过程。以掌握水轮机运行过程中筒阀及引流部件的水力特性、水轮机运行状况等为目的，利用FLUENT仿真软件模拟筒阀60s动水关闭，研究筒阀动水关闭行程内的压力、速度、流量和力矩等水力特性变化规律，重点对小开度下的水力特性进行细化分析。论文主要研究内容和成果如下： (1)结合筒阀实际运行工况，以转轮转速达到170r/min时的定常计算结果作为非定常计算的初始流场，依据筒阀实际关闭规律，利用profile定义筒阀关闭方式；对导叶和转轮区域进行网格加密，运用滑移网格和动网格技术适应流场区域变化，对不同套网格可信度进行对比分析；以水轮机全流道网格为计算模型，选用用RNG k-湍流双方程模型，采用SIMPLEC算法对流场进行迭代求解，较真实的模拟筒阀动水关闭过程水轮机内部流场特征。 (2)数值模拟得到筒阀动水关闭行程内的上下端面、内外表面的轴向动水作用力水力特性，并对其水力特性曲线进行分析；筒阀周围压力和速度场不稳定，筒阀在动水关闭过程中受到倾覆力矩作用，建立筒阀倾覆模型，并对筒阀倾覆稳定性进行评价，以判断筒阀是否倾覆和卡死，为筒阀实际安全稳定运行提供参考依据。 (3)重点研究小开度下的水力特性，对小开度关闭行程再次进行细化数值模拟，得到小开度下的筒阀过流区域流量和流速特性曲线；对筒阀下端面不同截面位置下不同点进行取值，得到其在小开度下的变化规律；对筒阀附近区域、转轮区域、环列平面叶栅导叶区域的压力和速度场进行分析，得到小开度下流场内部的漩涡、脱流、尾迹流等不稳定流和空化、汽蚀、振动等不稳定现象。为筒阀运行过程中的水力优化提供参考，可与筒阀实际运行工况进行对比分析，采取相应措施以使其运行更高效、更稳定。
[Abstract]:The emergency water closure of the cylinder valve is one of the protection measures to ensure the safe operation of the hydraulic turbine. This paper mainly uses the full flow path of the hydraulic turbine as a model to simulate the closing process of the cylinder valve, in order to master the hydraulic characteristics of the cylinder and drainage parts in the running process of the turbine and the running status of the hydraulic turbine, and use the FLUENT simulation software to simulate the cylinder valve 60s. When the water is closed, the hydraulic characteristics, such as pressure, velocity, flow and torque, are studied. The hydraulic characteristics of the small opening are detailed and analyzed. The main contents and results of this paper are as follows:
(1) according to the actual operating conditions of the cylinder valve, the constant calculation results of the rotary speed of 170r/min are taken as the initial flow field of unsteady calculation. According to the actual closing law of the cylinder valve, the closing mode of the cylinder valve is defined by profile, and the mesh of the guide vane and the rotary wheel is encrypt, and the slip grid and the dynamic grid technology are used to adapt the change of the flow field. The reliability of different sets of grid is compared and analyzed. Using the full flow path grid of hydraulic turbine as the calculation model, the RNG k- turbulent double equation model is selected and the SIMPLEC algorithm is used to solve the convection field iteratively. The flow characteristics of the turbine are simulated in a more real way.
(2) the hydraulic characteristics of the axial dynamic water force of the inner and outer surfaces of the cylinder valve are obtained by numerical simulation, and the hydraulic characteristics of the inner and outer surface are analyzed. The pressure and velocity field around the cylinder valve are not stable, and the tube valve is overturned by the overturning moment in the process of moving water closure, and the capsizing model of the cylinder valve is set up, and the overturning of the cylinder valve is stabilized. The evaluation is carried out to determine whether the cylinder valve is overturned and jammed, so as to provide reference for the safe and stable operation of the cylinder valve.
(3) focus on the hydraulic characteristics under the small opening, refine the small open stroke again, get the flow and velocity characteristic curve of the flow area under the small opening, get the value of the different points under the different section position of the lower end of the cylinder valve, and get the change law under the small opening. The pressure and velocity field in the region of the guide vane of the circular plane cascade are analyzed, and the instability of the vortex, defLOW, wake flow and other unstable flow and cavitation, cavitation, vibration, etc. in the flow field under the small opening is obtained, which provides a reference for the hydraulic optimization during the operation of the cylinder valve, and can be compared with the actual operating conditions of the cylinder valve. Measures are taken to make it more efficient and more stable.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TK730

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