Abstract
Cross-flow fans are widely used in numerous applications such as low-pressure ventilation, household appliances, laser instruments, and air-conditioning equipment. Cross-flow fans have superior characteristics, including simple structure, small size, stable airflow, high dynamic pressure coefficient, and low noise. In the present study, numerical simulation and experimental research were carried out to study the unique secondary flow and eccentric vortex flow characteristics of the internal flow field in multi-operating conditions. To this end the vorticity and the circumferential pressure distribution in the air duct are obtained based on the performed experiments and the correlation between spectral characteristics of multiple operating conditions and the inflow state is established. The obtained results show that when the area of the airflow passage decreases while the area of the eccentric vortex area gradually increases, then the airflow of the cross-flow fan decreases, the outlet expands, and the flow pattern uniformity reduces. It was found that wakes form in the vicinity of the blade and the tail of the volute tongue, which generate pressure pulsation, and aerodynamic noise. The pressure distribution along the inner circumference shows that the total minimum pressure appears in the eccentric vortex near the volute tongue and the volute returns near the zone. Moreover, it was found that the total pressure near the eccentric vortex is significantly smaller than that of the main flow zone. As the flow rate decreases, the pressure pulsation amplitude of the eccentric vortex region significantly increases, while the static and total pressure pulsation amplitudes are gradually increased. Close to the eccentric vortex on the inner side of the blade in the volute tongue area, total pressure is low, total pressure on the outside of the blade is not affected, and pressure difference between the inner and outer sides is large. When the flow rate of the cross-flow fan is 0.4 Qd, there is no obvious peak at the harmonic frequency of the blade passage frequency. This shows that the aerodynamic noise is caused by the main unstable flow.
Highlights
Cross-flow fans are widely used in applications with low-pressure ventilation, including household appliances, laser instruments, and air-conditioning equipment, due to their simple structure, small size, stable airflow, high dynamic pressure coefficient, and low noise level
In order to verify the accuracy of the numerical simulation of the aerodynamic performance prediction of the cross-flow fan, the aerodynamic performance obtained the numerical simulation
In order to verify the accuracy of the numerical simulation of theby aerodynamic performance prediction of the cross-flow fan, the aerodynamic performance obtained bythat the numerical simulation was compared with the experimental performance
Summary
Cross-flow fans are widely used in applications with low-pressure ventilation, including household appliances, laser instruments, and air-conditioning equipment, due to their simple structure, small size, stable airflow, high dynamic pressure coefficient, and low noise level. For cross-flow fans in air-conditioning applications, secondary and eccentric eddy flow characteristics of the internal flow field originate from multi-operating conditions and system variations. This is more pronounced in low-flow conditions. It should be indicated that these fans differ from other industrial fans regarding flow phenomena and design methods
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