Visualization of the internal flow field and veloc

2022-08-01
  • Detail

Research on visualization of internal flow field and velocity distribution of cross flow fan for air conditioning

1 introduction in recent years, with the widespread use of household and vehicle air conditioners, people begin to pay attention to the miniaturization of air conditioners. Due to its compact structure, the cross flow fan has great advantages over other types of fans in volume, and its efficiency is higher than that of axial flow and centrifugal fans in the case of small size. Therefore, it is concerned by more and more air-conditioning manufacturers. The air conditioner with this fan can deeply blow the gas into the space or room in the form of no vortex. In addition, the axial direction of this fan can be very long, so the air volume is large and the air supply is uniform. So far, many countries, especially Japan, Europe and the United States, have done a lot of research on the internal flow of cross flow fans, but most of the research is carried out without heat exchangers. After the cross flow fan is used in air conditioning, a heat exchanger should be installed at the inlet of the fan, so the research on the cross flow fan with heat exchanger has more practical significance. A clear understanding of the internal flow field and flow characteristics of the cross flow fan with and without heat exchanger will provide strong evidence for improving the fan performance and further theoretical analysis

under the condition that the shape and position of the shell and tongue remain unchanged, through the visualization of the internal flow of the cross flow fan and the laser Doppler velocimeter (if the amplifier output voltage is unstable LDV), a leading German automobile manufacturer has just purchased a new cannon e-system 5 enhanced equipment. With or without changes in conditions such as, heat exchanger and impeller blade inclination, The flow characteristics and velocity distribution in the inlet region of the cross flow fan and the inner region of the impeller are experimentally studied and summarized in detail. 2 experimental device and method the research object is a cross flow fan provided by an electrical appliance company in Japan. Fig. 1 is the schematic diagram of the cross flow fan prototype (installed with heat exchanger) for the experiment. The outer diameter of the impeller is 95mm, the inner diameter is 70mm (the ratio of inner diameter to outer diameter is 0.7, which can be used for prototype production 37), and the total length is 217mm. The 35 blades of the impeller are equally spaced. The whole impeller is divided into three parts by two annular plates, and the rotating shaft is installed on the side plate. The blade is 1mm thick circular arc blade with blade inclination α Is the included angle between the connecting line at both ends of the circular arc blade and the connecting line between the outer end of the blade and the center of the rotating shaft. There are 5 kinds of impellers used in the experiment, and the other sizes are the same. The blade inclination angles are 19 °, 24 °, 26 °, 29 ° and 34 ° respectively. The coordinate system of the experimental measuring point is centered on the axis of the rotating shaft of the impeller. For the convenience of the following discussion, a polar coordinate system with the rotation center of the impeller as the circular point as shown in Figure 2 is established. Fig. 1 cross flow fan (with heat exchanger) Fig. 2 the internal flow visualization experiment of the cross flow fan in the polar coordinate system is to use the white carbon dioxide generated by the sublimation of dry ice as the tracer particle through the laser curtain method, and use the camera to record the image. The internal velocity measurement experiment of the cross flow fan is to measure the velocity and direction of each point of the internal flow field of the cross flow fan through LDV, so as to draw the velocity vector diagram of the internal flow of the cross flow fan. 3 experimental results and analysis 3.1 visualization of internal flow of cross flow fan 3 and 4 are visualization images of internal flow of cross flow fan under three different impeller blade inclination angles. The white part in the figure shows the flow trajectory of gas particles. In the experiment, the impeller speed n=13, there are a large number of steel trading merchants with long operation time, wide business scope and strong trading ability at 00r/min, It can be seen from the visualization image: Fig. 3 visualization image of internal flow field of cross flow fan (with heat exchanger) Fig. 4 visualization image of internal flow field of cross flow fan (without heat exchanger) 3.1.1 gas inflow area

there are three gas flow directions in this area: (1) pointing to the rotating axis of the impeller; (2) The rotation direction is the same as that of the impeller; (3) It is opposite to the rotation direction of the impeller. In other words, the flow distribution of gas flowing into the impeller in this area is uneven, and there is a main inflow area. When setting the heat exchanger, the inclination angle of the impeller blade α= At 24 °, the main inflow area of gas is the largest (the included angle of the main inflow area is about 140 °); α= At 34 °, the main inflow area of gas is the smallest (the included angle of the main inflow area is about 50 °). Where there is no heat exchanger, α= At 24 °, the main inflow area of gas is the largest (the included angle of the main inflow area is about 160 °); α= At 19 °, the main inflow area of gas is the smallest (the included angle of the main inflow area is about 85 °)

3.1.2 impeller internal area

no matter what the blade inclination is, there is always an area with only a small amount of gas particles flowing in the impeller, which is due to the existence of eccentric vortex in this area. It can be seen from the experimental results that the eccentric eddy current is α= At 24 °, the area is the smallest, and the heat exchanger is set at α= The area is the largest at 19 ° and the area is the largest at 34 ° without heat exchanger. In addition, the position of vortex center of eccentric vortex varies with α The impeller moves from the lower side of the rotating shaft to the right side of the rotating shaft

3.1.3 gas outflow area

Copyright © 2011 JIN SHI