The biggest feature of the dc cross-flow fan is that the fluid flows through the fan impeller twice, the fluid flows in the radial direction and then flows out in the radial direction, the intake and exhaust directions are in the same plane, and the exhaust body is evenly distributed along the width direction of the fan. Due to its simple structure, small size and high dynamic pressure coefficient, it can reach a long distance, and is widely used in laser instruments, air conditioners, air curtain equipment, dryers, hair dryers, home appliances and grain combine harvesters.
Why does the dc cross flow fan have a reverse wind phenomenon?
DC cross-flow fans are widely used in the cleaning of agricultural materials and other departments due to their theoretically unlimited width, large air volume and small size. Although many scholars have studied the cross-flow fan, there are still some basic problems to be further explored. For example: what does the gas flow through the cascade twice, how the vortex that controls the flow field in the impeller is formed, what the direction of the gas flow depends on (that is, how the inlet and outlet are determined), etc. For this purpose, experimental studies were carried out. In order to facilitate the observation of the flow field, photography and the measurement of static pressure, the test is simulated with water.
For the dc cross-flow fan, if the design is improper, it may cause a reverse wind phenomenon, that is, the air inlet and the air outlet are exchanged with each other. To this end, a simulation test study was carried out in a water tank.
The boundary (shell) of the dc cross-flow fan, the cross-flow fan is generally composed of a curve GF (rear wall) with a gradually increasing gap with the impeller, a circular arc or other shape of the vortex tongue BD and the upper boundary DE. The length of the volute tongue and the angle γ between it and the upper boundary DE of the air outlet have a great influence on the performance of the fan. The test found that when the vortex tongue BD has a certain length, the vortex center is at the point C1, the fan can work normally, and the fluid flow direction. As the clearance δ between the vortex tongue and the impeller decreases, the vortex center C1 moves outward and downward, and the backflow decreases. If the angle γ is appropriately reduced, the fluid is easy to flow out along the upper boundary, and the backflow will also be reduced.
(1) The asymmetric outer boundary (including the asymmetry with the impeller gap) is the basic condition for the cross-flow fan to make the fluid flow stably in a certain direction.
(2) When the impeller drives the fluid to rotate, if there is only a straight boundary in the flow field, a vortex will be formed near the boundary, downstream of the smallest gap along the rotation direction of the impeller, and at the inner edge of the impeller. The rotation direction of the vortex of the cross-flow fan is the same as that of the impeller, and the strength of the vortex mainly depends on the speed of the impeller and the boundary conditions. The flow field inside and outside the impeller is mainly controlled by this vortex.
(3) If there are multiple boundaries, the flow field depends on the combined influence of each boundary. The vortex appears near the boundary where the flow resistance difference is greatest, and there is only one vortex.
(4) For the dc cross-flow fan, in order to make it work normally and not against the wind, compared with other boundaries, the vortex tongue should have a larger flow resistance difference.
DC cross flow fan diagram
dc cross flow fan parameters
DC cross flow fan diagram
DC cross flow fan appearance network
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