| Axial flow fan is widely used in mechanical ventilation cooling tower in coking, iron, steel,petroleum, thermoelectric and other industries because it is suitable for high mass flow conditions with low cost. Axial flow fan is the second largest energy-consuming equipment in the industrial circulating water system. The operating efficiency of axial flow fan will determine the power consumption of the fan directly, and the flow pulse characteristics of fan will determine the service life of the fan and the ventilator. Consequently, Improving the efficiency of the fan and reducing the pulsation of air flow have been an important research topic for scholars and enterprises both at home and abroad.LF92 fan that is widely used in mechanical ventilation cooling towers is chosen as the research object. Aerodynamic performance of the fan is studied with field experiment as well as steady and unsteady three-dimensional numerical simulation. The results show that the numerical simulation results are consistent with the experimental results. The experiment and numerical results show that the fan is low-efficient, and the turbulence intensity of the ventilator is high.Aiming at these problems, on the basis of summarizing the domestic and foreign research,based on the fan blade tip of tong groove schemes to retrofit of blade, was studied by the three-dimensional numerical simulation of slot coefficient k and groove depth h effect the performance of the fan, the slot coefficient of 0.3, 0.5 and 0.75, slot depth in 3 mm, 5 mm, 8 mm, contrast analysis of the total of five kinds of slot. The results show that the fan blade tip on the groove after, the turbulence intensity of tip clearance obviously increased, within the tip clearance, near the blade position appeared and the leakage flow in the opposite direction from leakage flow, reducing the flow of leakage flow control effect. By comparing the structure of different grooves, it is found that the effect of slot coefficient on aerodynamic performance is greater than that of opening groove. In all retrofit scheme, 0.75 k, h = 5 mm flow control scheme of the best, the blade tip clearance leakage down 15.79% compared with the prototype fan, a 5.49% drop in the input power, at the same time, the most obvious point of pressure pulsation frequency amplitude of 43% decline.In order to further improve the aerodynamic performance of fan, apply the single row grate tooth model instead of the optimal aerodynamic performance k0.75 h5 non groove model base on above research, then the steady and unsteady numerical simulation are carried out. The results showed that the aerodynamic performance of slot grooved grooves was higher than that of k0.75 h5, and the input power fell 7.96%. Because of the clearance vortex moved to within the tip clearance near blade pressure surface, and the turbulent kinetic energy of the clearance vortex strength increase, further enhance the blocking effect of leakage flow, the leakage down 19.74%, compared with the prototype fan pressure pulsation pressure changes in the most obvious point, pressure pulsation intensity and frequency amplitude fell by more than 90%, fan aerodynamic performance has been further improved. |
PDF Full Text Request