Structural Optimization And Experimental Verification On The Reduction Of The Fluid Fluctuation In A Rotary Energy Recovery Device

Rotary energy recovery device(RERD),as one of the key equipment to save energy in seawater reverse osmosis(SWRO)system,has the advantage of high efficiency,flexible capacity and easy installation and uninstallation.Fluid fluctuation will be generated when the pressure is switched in a RERD,which may cause vibration and noise.Now appropriate measures to mitigate the fluid fluctuations have been seldom researched.Based on the self-made RERD that need to be optimized in our laboratory,the pre-pressurization and pre-depressurization grooves were firstly slotted on the surface of RERD's endcovers to decrease the flow fluctuations of RERD,which is called a new type endcover.The pre-pressurization groove is set on the front edge of high pressure port and the pre-depressurization groove is set on the front edge of low pressure port in the endcovers.Then,effects of the grooves on performance fluctuations of the RERD were researched by means of computational fluid dynamics(CFD)simulations.Simulative results indicated that when compared with the un-slotted RERD under flow rate of 12 m~3/h,rotary speed of 400 rpm,and operating pressure of 6.0 MPa,the flow fluctuation amplitudes of the slotted RERD were reduced about 75.3%for high pressure outlet and 77.2%for low pressure outlet respectively.Similarly,the pressure fluctuation amplitudes of the slotted RERD were dramatically reduced about 92.5%for high pressure outlet and 90.7%for low pressure outlet.To indicate the validity of the simulation,the corresponding experiment was carried out in SWRO platform established in our laboratory.The results showed that both the experimental and simulative flow fluctuation amplitude increased with the rise of rotor speed.The difference between the experimental and simulative amplitude under the same rotor speed is 2.76%-7.55%under flow rate of 12m~3/h and operating pressure of 6.00 MPa,rotor speed from 200 rpm to 500 rpm,which indicated the CFD simulation results were reliable.Finally,the RERD was coupled to SWRO desalination system to evaluate the static performance and the stability of RERD's long-term operation under operating flow rate of 13m~3/h.The results showed that static performance of the RERD with PEEK end plate was good,and the maximum static leakage was 0.5 m~3/h.However,dynamic performance of the RERD with PEEK end plate was bad,and the dynamic leakage could reach 1.3 m~3/h under pressure of 5.5 MPa.In the process of long term operation,the dynamic leakage maintained 1.3 m~3/h under pressure of 5.5 MPa.Otherwise,the RERD equipped with ceramic plate also showed good static performance,the maximum static leakage was 0.5 m~3/h.Moreover,the corresponding dynamic performance was very good,the dynamic leakage reached 0.8 m~3/h under pressure of 5.5 MPa.In the process of long term operation,the equipment had a stable performance and the dynamic leakage maintained 0.8 m~3/h under pressure of 5.5 MPa.Meanwhile,the energy recovery efficiency could reach 92.1%.