等温层曝气器水动力学模型.docVIP

  Hydrodynamic model for a hypolimnetic aerator#  5 10 15 20 25 30 35 40 45 SUN Xin, DUAN Feifei, LIU Wei, HUANG Tinglin, ZHANG Wushou, CONG Haibing (Schoold of Environmental and Municipal Engineering, Xian University of Architecture and Technology) Abstract: The water velocity in the aeration chamber of a hypolimnetic aerator directly influences the efficiency of mixing and oxygenation in the hypolimnion, and consequently the effect of water quality improvement. Based on the energy balance between the energy input and the energy loss for the gas-liquid two-phase flow in the aeration chamber, a one-dimensional hydrodynamic model for the aeration chamber was developed. Various types of energy loss were analyzed, an equation for the energy loss due to the wakes was particularly proposed. The average gas holdup and water velocity in the riser of the aeration chamber were predicted by solving the developed model with the reeal-domain method of MATLAB. Sensitivity analysis of the model parameters showed that the prediction results were greatly dependant on the flow resistance coefficient at the top and the coefficient due to local disturbances at the entrance and exit. Using optimized parameters, both gas holdup and water velocity were well predicted within ±7% and ±15% of the measured ones respectively. Developed hydrodynamic model for the aeration chamber can be used to accurately predict the average water velocities under different air flowrates in the aeration chamber, and can be used to design and optimize the hypolimnetic aerator. Key words: Hypolimnetic aerator;hydrodynamic model;water velocity;prediction 0 Introduction Thermal stratification widely occurs in source reservoirs and contributes to most water quality problems in such waters[1-3]. Once the reservoir is stratified, the thermocline prevents the mass transfer between the epilimnion and hypolimnion and makes the dissolved oxygen (DO) in the hypolimnion decrease to nearly zero through the biological a