Cause analysis and suppression method of the vortex at the impeller outlet of the multiblade centrifugal fan

Indoor air conditioning systems play a crucial role in regulating the environmental conditions of enclosed spaces. The noise generated by such systems can significantly impact human comfort. The multiblade centrifugal fan, as a crucial component of indoor air conditioners, has a significant impact on the performance of the air conditioner. The vortex, which is the primary noise source inside the fan, hinders the aerodynamic noise reduction of the indoor unit. During experimental research and numerical simulation of the indoor unit, the researchers identified the presence of a vortex flow at the outlet of the multiblade centrifugal fan. By analyzing the velocity vector of different cross-sections in the fan, the researchers determined the formation mechanism and influencing factors of the vortex at the fan's outlet. The addition of fairing sheet plates on the volute wall was explored as a vortex suppression method, which proved effective in weakening and suppressing the vortex. The test results showed that under the same air volume, the noise reduction amplitude of the fan equipped with fairing sheet blades was 1.2 dB at an outlet static pressure of 30 Pa and 0.7 dB at an outlet static pressure of 100 Pa. The research findings suggest that the addition of the fairing sheet can effectively reduce the vortex's intensity, improve the performance of the multiblade centrifugal fan, and reduce the noise.