Research On The Optimized Integration Of Micro Centrifugal Fans

Micro centrifugal fan is a common turbomachinery, with the characteristics of high pressure coefficient, low noise, widely used in the field of energy, electronic, aviation, etc. It has become a hot spot of research object. Due to the asymmetry of centrifugal fan itself, there exit quiet severe velocity distortion on the outlet surface of centrifugal fan. The speed of fluid near the lateral of the centrifugal fan is almost 3 to 4 times the speed of the fluid near the medial. In micro centrifugal fan this phenomenon is extremely unfavorable to the realization of the function of ventilation, heat dissipation, etc. The asymmetry of micro centrifugal fan can also lead to the low efficiency, the efficiency of common micro axial fan is about 70%, and the efficiency of the micro centrifugal fan is only 40% to 60%, thus it is very significant for the performance of centrifugal fan by improving the parameters of impeller in centrifugal fan. Considering the complexity of structure and the difficulty to match the suitable parameters for micro centrifugal fan, experimental method is inevitable to spend so much time and cost a lot as a result, therefore we rectify the outlet velocity distortion of centrifugal fan by the way of numerical simulation, and design the integration of distortion section and volute, furthermore improve the overall performance of micro centrifugal fan, in order to rachieve the goal of integrated optimization.This article firstly builds a 3D modeling of a certain type of micro centrifugal fan, then uses Numeca software for meshing and numerical simulation, and obtains the calculation results of internal flow field. Under the condition of some rotate speed, analyses the distribution and variation of pressure and velocity in the micro centrifugal fan. Study shows that the internal flow of centrifugal fan is very complicated, the pressure and velocity of fluid in every part of centrifugal fan reveals the acceleration and pressurization of principle in micro centrifugal fan; flows on the surface of blade and in the cascade channel reveals the phenomenon of “jet-wake”, explaining the source of the vibration and noise in micro centrifugal fan; velocity distributions in micro centrifugal fan shows that it is very uneven of fluid velocity on the surface of outlet, the fluid velocity near the medial side of volute is about 5 m/s, while the fluid velocity near the lateral side of volute is more than 20 m/s, the velocity from medial side to lateral side presents the increasing trend, it can be seen that the outlet velocity exists severe speed distortion in micro centrifugal fan, and will have great effect on realizing the function of ventilation, heat dissipation and so on in micro centrifugal fanThen in view of the inhomogeneity of outlet velocity in micro centrifugal fan, on the basis of the traditional micro centrifugal fan, this article designed the volute scroll to correct the velocity distortion by the way of equilateral primitive method, in order to improve the uniform velocity distribution. The volute scroll designed by the way of equilateral primitive method is more correspond with the real flow condition of the inner space in the micro centrifugal fan, the acceleration and pressurization of fluid was changed with the radial of volute, near the outlet the fluid flows into the mixing section, making these fluid with uneven direction and magnitude of velocity transfer energy mutually by extrusion and collision, decrease the speed difference between the fluid clusters. This paper innovatively defines the concept of distortion variance, by comparing the differences between before and after of designing the outlet of micro centrifugal fan, the distortion variance has decreased by an order of magnitude from the original 6 m2 / s2, the definition of distortion variance quantifies the degree of nonuniformity and the results of distortion correction can be measured more visually.Finally due to the complexity of a micro centrifugal fan, and there are too much parameters affecting the performance of micro centrifugal fan, so the orthogonal test are usually adopted for analysis in engineering. Numerical simulation is carried out with changes of four parameters in the impeller including the number of blade, the 2D type of blade, the beveling angle of blade and twisted angle of blade. The influence of these four parameters to mass flow, pressure and efficiency are established. According to the degree of these four parameters, ranking the order of these four parameters and choosing the optimal value to micro centrifugal fan. The best combination of these four parameters is selecting the type C as 2D optimization for blade, the number of blade is 50, twisted Angle is 10 °and beveling angle is α = 45 °, and the influence of four parameters of micro centrifugal fan ranks as follows: shape of 2D section > beveling angle > number of blade > twisted angle.