Numerical Simulation Study On Optimization Of Hydraulic Characteristics Of Inlet Channel Of Sea Intake Pump Station

The seawater taken from the seawater intake system of a liquefied natural gas(LNG)receiving terminal is mainly used as a heating medium for LNG.How to safely,efficiently,and stably obtain seawater that meets the requirements of the gasifier is crucial for the normal operation of the gasification unit.The flow channel for seawater intake at an LNG receiving terminal is generally designed to be symmetrical,but considering that the water intake volume is often small in the early stages of operation,the water intake pipes are generally arranged asymmetrically.Currently,there is little research on the flow characteristics of non-symmetric inflow in the seawater intake pump station flow channel.In order to explore the flow characteristics of nonsymmetric inflow in the seawater intake pump station flow channel,this paper used Open FOAM to establish a numerical model of the Zhoushan LNG intake channel.The k-ω SST turbulent model was selected,the free interface was captured using the VOF(Volume of Fluid)method,the FVM(Finite Volume Method)method was used for spatial discretization,and the PIMPLE(PISO-SIMPLE merge algorithm)algorithm was used for velocity-pressure coupling.The accuracy and reliability of the numerical calculation method were verified by comparing it with actual flow rate data.Based on the simulated flow results,the water flow characteristics in the flow channel during non-symmetric inflow were studied,the causes of poor flow were explored,and optimization measures were developed accordingly.The numerical model established in this study can provide scientific basis for the design of the flow channel structure and the selection of water intake methods for seawater intake pump stations.The specific research work and conclusions are presented below.1.A mathematical model of an open seawater pump station flow channel was established,and a grid independence test and sensitivity analysis of computational time were conducted.The numerical simulation results were validated based on measured cross-section flow velocities,showing that the relative error between the calculated and measured average flow velocities of the characteristic sections did not exceed 8.8%,7.2%,6.3%,and 5.9%.The numerical model can better reproduce the flow characteristics in the physical model test of the pumping station.2.This study compares and analyzes the flow patterns and velocity distributions in the entire channel structure at three different planes,namely the inlet bell mouth plane,the gate mid-section plane,and the gate top plane,under two types of water inflow: symmetrical and asymmetrical.The turbulence kinetic energy distribution at the inlet bell mouth plane and the uniformity index of the flow velocity at the pump inlet cross-section are also examined.The average uniformity index before the pump with asymmetric inflow is higher than that with symmetric inflow,and the total average turbulent kinetic energy of each seawater pump inlet basin is also lower than that under symmetric inflow conditions.Therefore,asymmetric inflow is more advantageous for the operation of the water pump.3.In response to the adverse flow pattern of the initial flow channel structure of the pump station,optimization research was conducted on the flow pattern in the flow channel by adding crossbeams in the forebay and adding triangular guide piers and crossbeams in the gradually expanding section of the inlet basin.Through multiple schemes of gradual modification and comparison,it was found that the extension scheme of the double water blocking crossbeam in the forebay performed the best in terms of flow velocity uniformity on the front section of the pump,effectively improving the flow velocity distribution at the inlet of the flow channel.On this basis,a triangular diversion pier is added to the gradually expanding section of the inlet basin to minimize the average turbulent kinetic energy in front of the pump,which can effectively improve the bias and reflux flow patterns at the outlet of the filter tank,thereby ensuring a uniform distribution of water flow in the inlet basin.