Research On The Operating Characteristics And Structure Influence Of The Rotary Energy Recovery Device

In the reverse osmosis seawater desalination system,the rotary energy recovery device has become the key equipment to reduce the system operating cost and energy consumption due to its precise structure,low operating cost and high energy recovery efficiency.The device is based on the positive displacement principle of liquid pressure energy transfer.High-pressure brine and low-pressure seawater directly contact with each other in the device for energy transfer and material exchange.The energy recovery efficiency is as high as 98%.It is the most efficient product among the current energy recovery devices on the market.There are three core problems in the practical application of rotary energy recovery device,which are worthy of in-depth study: first,effectively control the mixing degree of the liquid in the rotor passage to ensure the salt concentration of the high-pressure outlet fluid;Second,the rotor is supported by the hydraulic lubrication of clearance liquid film,and the end seal is realized on the premise of ensuring the energy recovery efficiency;Third,the device realizes self-starting under the drive of incoming liquid and can run smoothly.Aiming at the above three key problems,the liquid mixing process in the rotor passage and the end face sealing were simulated and analyzed by numerical simulation.Based on theory,a theoretical derivation of the rotor speed of rotary energy recovery device was carried out.The numerical simulation method was used to explore the influence of the inclination of the sump,end clearance and the lubricating groove on the performance of the device.The main research and results are as follows:(1)The three-dimensional model of liquid mixing process in rotary energy recovery device was established,and the formation,development and stability process of liquid piston in rotor passage were analyzed by numerical simulation method.The influences of flow rate and speed on the energy recovery efficiency and mixing degree of the device were analyzed.Through the simulation analysis,it was concluded that the rotating energy recovery device has the characteristics of speed adaptability and constant mixing degree.(2)In this study,the starting torque of the rotor driven by the inflow was analyzed,and the rotation resistance torque received by the circumferential surface and the end surface was calculated.The theoretical relationship between the rotational speed and the treatment capacity of the rotary energy recovery device was obtained through the moment balance.(3)The numerical simulation method was used to explore the influence of the inclination of the sump on the fluid flow state,self-starting performance and operation performance of the device.It was found that the end plate inlet sump is helpful to increase the tangential velocity of the driving fluid in the channel,and then increase the starting torque of the rotor.The increase of the inclination angle of the sump is not conducive to the start-up process of the device,but is conducive to the reduction of the turbulence intensity in the channel.When the inclination angle of the sump is less than,the mixing degree decreases with the increase of the dip angle;when the dip angle is more than,the increase of the inclination of the liquid collecting tank aggravates the degree of liquid mixing in the channel.(4)The numerical simulation method was used to analyze pressure loss and the leakage mechanism of the end face.It was concluded that the pressure difference flow between the high and low pressure fluid in the end clearance is the cause of the end leakage.The liquid pressure in the lubricating grooves affects the end pressure loss,and the end pressure loss is proportional to the liquid pressure in the lubricating grooves.By analyzing the influence of different end clearances on the pressure loss and leakage,it was concluded that with the increase of end clearance,the pressure loss decreases rapidly and then tends to be stable,while the end leakage increases continuously.By comparing and analyzing the pressure loss and flow loss of models with and without lubricating grooves under different clearances,it was found that the lubricating grooves are conducive to improve the sealing performance of the device.