Rotor Dynamic Characteristics Of Energy Recovery Hydraulic Turbocharger

The hydraulic turbocharger integrates residual energy recovery and liquid pressurization.It is widely used in large and medium-sized seawater desalination systems by reverse osmosis membrane method.In order to improve system efficiency,the speed of the integrated machine is usually as high as 10~4 orders of magnitude,which puts high requirements on the stability of the bearing-rotor system of the integrated machine.High speed will not only reduce the bearing damping,but also increase the fluid excitation force received by the rotor to varying degrees,which will adversely affect the stability of the rotor system of the integrated machine.Therefore,in order to ensure the safe and stable operation of the turbine energy recovery integrated machine,it is very necessary to conduct a systematic and in-depth study on the dynamic characteristics of its rotor system.The main work done in this article is as follows:(1)The development history and the research status of the energy recovery hydraulic turbine were summarized systematically;the related research progress and development trends of water lubricated bearings and rotor dynamics were reviewed.(2)Through the numerical simulation,the hydraulic performance and internal flow field of the turbine and booster pump were analyzed,three different operation schemes were designed according to power matching;the distribution rules of the radial and axial forces of the booster pump impeller and turbine impeller are studied.The simulation results show that the turbine and booster pump have better hydraulic performance under design conditions.When the turbine was operating under 1.4Q_d and the booster pump was operating under 1.0Q_d,the overall efficiency of the hydraulic turbocharger is the highest.When the booster pump was running under partial operating conditions,the radial force on the impeller is greater,and the radial force on the turbine impeller increases with the increase of the flow rate.The total axial force of the integrated machine points to the turbine outlet,and its size increases with the increase of the flow rate.(3)Based on the theory of fluid dynamic pressure lubrication,the detailed steps of solving the dynamic and static characteristics of the bearing liquid film using the finite difference method and the perturbation parameter method are combed,and the dynamic and static characteristics of the bearing under different structural parameters are solved and analyzed in conjunction with MATLAB software.The calculation results show that increasing the aspect ratio or reducing the radius clearance can improve the bearing capacity of the bearing.When the ratio of the clearance ratio(c?e)to the aspect ratio(L/D)is in the range of 0.0065~0.0075,the minimum water film thickness of the bearing can be optimized.Under high-speed conditions,the bearing damping is significantly reduced,and the stability is relatively poor.(4)Based on SAMCEF Rotor software,the finite element calculation models of three different dimensions of the bearing-rotor system were established,the critical speed solution and vibration mode analysis of the three calculation models were carried out.The calculation results show that the results of the three calculation models are in good agreement.The rotor system of the hydraulic turbocharger has a low-frequency eddy frequency.To ensure the stable operation of the rotor,its actual working speed should be set in the range of 4800~25000r/min.Properly reducing the density of the rotor material can increase the critical speed of the rotor of the integrated machine;the structural parameters of the bearing mainly affect the rotor's rigid body Critical speed.(5)The transient response of the bearing-rotor system considering different loads were analyzed by SAMCEF Rotor analysis software.The results show that:the common amplitude value of the hydraulic turbocharger could be effectively reduced by improving the machining accuracy of the impeller,installing the impeller in a misaligned manner,increasing the starting acceleration of the rotor,selecting bearings with small stiffness and large damping.After considering the action of the fluid excitation force,the vibration amplitude of the rotor was significantly increased compared to when only the unbalanced mass is considered,and the amplitude increases with the increase of the radial force received by the rotor.The trajectory of the axis at different positions has different eccentricity,and the trajectory curve was petal-shaped.