Performance Studies Of Rotary Energy Recovery Device Based On Different Material Friction Pairs

Seawater desalination as a primary means to solve the problem of shortage of freshwater resource, seawater reverse osmosis is a mainstream technology of thedesalination market. Energy recovery device is one of the key devices to reduce its’operational cost. Rotary energy recovery devices are the focus of research anddevelopment because of their high efficiency, operational stability and flexibility,compact structures and many other advantages.Based on the simulative platform of reverse osmosis desalination system, this paperis to choose two different end-face friction pairs: Polyether-ether-ketone (PEEK) toceramic and ceramic to ceramic. Under the first friction pair, the start-up mode of thedevice is researched, and the variations of leakage flow and efficiency withoperational pressure and rotary speed are studied. Under the second friction pair,some research such as the variations of rotary torque and leakage flow with end-faceclearances is carried out. Under the PEEK-ceramic friction pair, combined the newservo motor system (rotary speed ranged from0to1000r/min), the variable flowratetests and the long-term stability tests have been done. This paper is also designed animproved total ceramic rotor and sleeve. The leakage tests and flow stability tests ofthe device are carried out.The results show that, under the PEEK-ceramic friction pair, the device is better tostart up according to this order: turn on the feed pumps, and then regulate the rotaryspeed to the rated value, at last, raise the system’s operational pressure to a requiredvalue. And under that start-up mode, the biggest rotary torque is just17.28N·m. Withthe increase of operational pressure, the leakage flow rises to a value placidly and theefficiency increases rapidly to93%and then keeps stable. With the acceleration ofrotor, the leakage flow declines a little and the efficiency increases slightly. Under theceramic-ceramic friction pair, there are three end-face clearances:0.060mm,0.035mmand0.010mm. With the reduction of the end-face clearance, the rotary torqueincreases obviously, the leakage flow decreases evidently and the effiency increases.Under the PEEK-ceramic friction pair, combined the new servo motor system,variable flowrate tests (14m3/h-500r/min,16m3/h-600r/min,18m3/h-700r/min) are carried out. And the results show that, the hydrodynamic characteristics of the deviceare fine under different flowrates, the leakage flow decreases and the efficiencyincreases with the enlarged operational flowrates. In the long-term operationalstability tests, the device runs for60hours (12hours/day times5days) under theoperational conditions of14m3/h,500r/min and6MPa. During the earlier stage of thetest, the device performs well, the leakage flow is stable at0.6m3/h and the efficiencywaves up and down at94%. But during the later period, the operational pressure ofthe device cannot stay stable and gradually declines, and the leakage flow of thedevice rises slowly. After taking apart the device, we find that, the PEEK endfacewears out. With the improved total ceramic rotor and sleeve, under the pressure of6.0MPa, the device’s maximum static leakage flow is0.19m3/h and the dynamic leakageflow is0.60m3/h. The pressure and flow fluctuations of all flows are tiny.