| Multi-blade centrifugal fans are widely used in industrial and home appliance products.With the improvement of quality of life and the enhancement of energy-saving consciousness,people put forward higher requirements on the efficiency,noise and stable operation range of centrifugal fans.In this paper,based on a model of double-suction multi-blade centrifugal fan,combined with numerical simulation and experimental measurement,this paper analyzes the internal flow field of the prototype under three conditions of small flow,highest efficiency and large flow,and the unreasonable information of flow field structure is obtained.By changing the way of fan placement,the matching relationship between the volute and the impeller,and the distribution pattern of the blades,the airflow flow structure of the inlet and outlet of the impeller can be improved,and the external characteristics and aeroacoustic performance of the fan can be improved.(1)Study on the different placement methods of multi-blade centrifugal fans in the fixed-size kitchen ventilator.Compare the left and right intake air and the front and rear air intake to study its influence on the impeller inlet flow structure and the performance of the whole machine.When the fan system is placed in the left and right air intake mode,the velocity distribution on the air intake surface shows uneven front and rear;when placed in front and rear air intake mode,it shows uneven upper and lower.The results show that it is reasonable to use left and right air intake and the non-motor side is close to the large air intake box.(2)On the basis of logical placement,keep other parameters changeless and further studied the axial matching between the volute and the impeller to improve the airflow of the impeller outlet.Respectively changed the distance between the front end surface of the volute and the front disc of the impeller?the rear end surface of the volute and the rear disc spacing of the impeller and selected the better ones for combination to determine the reasonable axial relative position of the volute and the impeller.Research indicated that the distance between the volute and the front and rear discs of the impeller is increased by 4mm,which is the reasonable match.The fan efficiency is increased by 2.34%?the static pressure is increased by 3.61% and the noise is reduced by 0.75 dB.(3)Based on sinusoidal function and random distributed modulation,the effects of five non-uniform blade distribution modes on rotational noise are studied.Through numerical simulation and aeroacoustic analysis,combined with the experimental data,the influence of the blade modulation mode and amplitude on the aerodynamic performance of the fan and the modulation law of the blade passing frequency are obtained.The results show that when the blade spacing modulation amplitude is less than 20%,the blade distribution form has little effect on the aerodynamic performance of the fan;the blade non-uniformity scheme can reduce the noise of the fan under various working conditions by about 2-4dB.in which the sinusoidal modulation mode with a modulation period of 2 and a modulation amplitude of 8% is the most effective,and the maximum noise reduction is 4 dB. |
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