Research On Characteristics Of Ocean Thermal Energy Double Turbine Gas Bearing-rotor System

With the rapid development of global economy,there is a widespread problem of energy shortage in all countries,and the demand for energy is urgent.Clean energy plays a pivotal role in the development of national economy.Among there are huge reserves,clean and pollution-free ocean energy in the form of ocean thermal energy that have become the focus of attention of experts and scholars from all over the world.And as the core of the ocean thermal energy power generation system,the turbine has a significant impact on the utilization rate of energy and the efficiency of the power generation system.In this paper,the dual-turbine generator set in the ocean thermal energy power generation system is taken as the research object.Aiming at the instability of the gas bearing-rotor system,the load-carrying characteristics of the hydrostatic gas bearing in the turbine unit and the dynamic characteristics of the air-floating rotor system are studied,and the experimental test of the double-turbine generator unit is carried out.The main research contents are as follows:Firstly,The hydrostatic gas Reynolds equation considering the flow characteristics of the orifice is deduced by combining the Navier-Stokes equation,the continuity equation and the velocity boundary condition.The solution process of the gas film thickness equation of the gas bearing and the characteristic equation of the orifice flow,and the calculation method of the outflow in the control area of the orifice is given.Then,the Reynolds equation is discretized by the finite difference method and the Newton iteration method,and the characteristics of the hydrostatic radial gas bearing solution program is compiled based on Matlab.The air film pressure distribution is numerically simulated,and on this basis,the influence of gas pressure,gas film thickness,eccentricity,length-diameter ratio,orifice position,orifice diameter and quantity,air source medium on the load-bearing characteristics of bearing are analyzed.Then,the variational principle is used to construct the functional,and the Reynolds equation of the hydrostatic gas thrust bearing is solved by the finite element method,the over-relaxation iterative method and the proportional division method.Matlab calculation program was written to study the numerical simulation of the air film pressure distribution in the bearing clearance,and analyze the influence of air supply pressure,orifice diameter and quantity on bearing performance,and gas mass flow.In addition,the structural parameters and working conditions of the above two bearings are dynamically optimized.The research method can provide reference value for the optimization design and analysis of hydrostatic gas bearings.For a 50 kW dual-turbine generator set,aerodynamic parameters are optimized by genetic algorithm,one-dimensional aerodynamic design of the turbine is carried out,and Solidworks is used for three-dimensional modeling.With the help of ANSYS,the structure of the rotor system is analyzed,and obtain stress-strain diagram of rotor system.The dynamic model of the dual-turbine gas bearing-rotor system is established,and the gas bearing is equivalent to a spring unit.Then modal analysis method is adopted to solve the critical speed,modal shape of the system.The effects of bearing support stiffness and rotational prestress on the natural frequency of the system are analyzed.Then the harmonic response analysis of the rotor system is carried out based on the modal analysis.The amplitude-frequency characteristic curve of rotor system is obtained when the impeller is subjected to external excitation force.Finally,the dynamic balance experiment of the rotor system is carried out to adjust the unbalance of the rotor system,and build an experimental platform to study the vibration of the unit in the transient speed-up and speed-down process.The experimental results show that the stability of gas bearing and unit is good.The research results can provide a theoretical basis and experimental basis for the dynamic analysis,optimization analysis,experimental research of the gas bearing-rotor system,and have very practical engineering application significance.