Bionic Volute Tongue Optimization Design of Multi-blade Centrifugal Fan Inspired by the Wave Leading-edge of Humpback Whale Flippers

The volute tongue can split the gas in the multi-blade centrifugal fan to make the gas flow to the volute outlet as much as possible.However,the unsteady axial deflection of the gas in the impeller results in different air flow angles at the outlet of the impeller at different blade heights.This seriously affects the flow near the volute tongue.The wave leading-edge structure of humpback whale flippers has a very high flow control effect under complex flow conditions.Therefore,the wave leading-edge structure is studied in this paper and applied to the optimization design of multi-blade centrifugal fan volute tongue.First,based on the wave leading-edge structure of humpback whale flippers,three-dimensional wave leading-edge airfoils with different wave direction angles are established to judge the adaptability of the new wave leading-edge structure under different attack angles.Then,aiming at the internal flow field and noise characteristics of multi-blade centrifugal fan,a bionic volute tongue optimization design method is proposed,and studied its influence on the internal flow field and noise characteristics of the fan.The results show that when the wave direction angle is 45°,the wave leading-edge structure can effectively suppress the generation of the leading-edge separation vortex and the shedding of the wake vortex,which is also helpful to reduce the noise.The bionic volute tongue with the wave leading-edge structure can adapt to the situation that the impeller outlet air flow angle is small.At the maximum volume flow rate operating point,the static pressure recovery coefficient of the bionic volute tongue fan is increased by about 5%compared to the original fan,the air volume is increased by 5.16%,and the noise is reduced by 0.6 dB.

Effects of Bionic Volute Tongue on Aerodynamic Performance and Noise Characteristics of Centrifugal Fan Used in the Air-conditioner

The aerodynamic noise generated by the centrifugal fan used in the air conditioner is related to the comfort of human living and working,which can be controlled by using the bionic design and optimization of key components of centrifugal fan.Inspired by the non-smooth leading edge of long-eared owl wing,eight kinds of volute tongues are proposed to reduce the aerodynamic noise of a centrifugal fan.The flow and sound characteristics are numerically investigated by incorporating computational fluid dynamics and computational aero-acoustics.The optimal result exhibits a noise reduction of up to 1.5 dB with a slight increase in mass flow rate.The acoustic characteristics,with respect to the sound pressure level,power spectral density,and sound directivity are discussed.The time-domain,frequency-domain,and root mean square values of pressure fluctuation are monitored and analyzed to assess the unsteady flow interaction between the volute tongue and impeller.The intensity and scale of vortices in the centrifugal fan are suppressed in the upstream and downstream of the bionic volute tongue,and the turbulence effect on the surface of the volute tongue becomes even and weak.

Effect of the volute tongue cut on pressure pulsations of a low specific speed centrifugal pump

The volute tongue,as the crucial component inducing rotor-stator interaction,is detrimental to unsteady pressure pulsations of centrifugal pumps.In the present paper,to investigate the effect of the volute tongue cut on pressure pulsations of a low specific speed centrifugal pump,three volute tongues are obtained through twice cuts,named cases 1,2,3.Twenty measuring points are evenly mounted on periphery of the volute casing to obtain unsteady pressure signals using high response transducers.Pressure amplitudes at the blade passing frequency fBPF and root mean square(rms)values in 0 Hz-500 Hz frequency band are applied to evaluate the cutting effect.Results show that pressure spectrum is significantly affected by the volute tongue cut,especially for the component at fBPF.For different measuring points,influences of the volute tongue cut on three cases are not identical.From nns values,it is evident that cutting the volute tongue will lead to pressure energy increasing for most of the concerned measuring points,especially for the points at the far away region from the volute tongue.Finally,from comparison with the original shape case 1,the averaged increment of the twenty points is more than 20%.So it is concluded that for this type centrifugal pump,cutting the volute tongue is not reasonable considering low pressure pulsation requirement.