Aerodynamic Noise Analysis Of 6MF-30 Portable Pneumatic Extinguisher Fan

Portable pneumatic extinguisher is one of most important forest fire-fighting equipment originally designed by China.It is easy to use,but the noise of portable pneumatic extinguisher may have serious physiological and psychological effects on operators.Hence,we conducted the research on the aerodynamic noise of the 6MF-30 portable pneumatic extinguisher fan in this paper.The main content and conclusions are as follows:1.The theoretical analysis on the aerodynamic noise of the 6MF-30 portable pneumatic extinguisher fan was done.The acoustics analysis results show that the rotary movement of impeller and the irregularity of shell result in fluid pulsation.And the fluid pulsation causes the aerodynamic noise.The aerodynamic noise source of the portable pneumatic extinguisher fan includes monopole source caused by uneven mass flow,dipole source caused by interaction force of shell and air and quadrupole source caused by air viscous force2.The flow field simulation of the 6MF-30 portable pneumatic extinguisher fan was carried out.Firstly,we measured the wind speed of the air inlet,which showed that the wind speed was 1.8 m/s.Then,based on the known inlet conditions,we used the FLUENT software with a two dimensional model to conduct the flow field simulation,during which the Realizable k-s turbulence model was used.And we got the dynamic pressure,turbulence intensity and velocity magnitude results which turned out that the main aerodynamic noise source might locate in the impeller,the vortex tongue and the shell.3.The aerodynamic noise simulation of the 6MF-30 portable pneumatic extinguisher fan was carried out.The simulation was conducted on the FLUENT software with the method of a combination of the LES turbulence model and the FW-H noise calculation model.Based on the results of the noise simulation,we carried out the experiment of the noise measurement and analyzed the difference between the simulation results and the practicality experiment results,which confirmed us that the main aerodynamic noise source was located in the impeller and vortex tongue.Finally,we got the aerodynamic noise model of the 6MF-30 portable pneumatic extinguisher fan.4.The influencing factors of the aerodynamic noise of the 6MF-30 portable pneumatic extinguisher fan were analyzed.We carried out the aerodynamic noise simulations of models of the portable pneumatic extinguisher fan with different parameters and made a contrastive analysis of the simulation results.It was showed that exit installation angle had little influence on the aerodynamic noise,however,the stagger angle and the curvature ratio's impact on the aerodynamic noise was depended on different frequency ranges.The aerodynamic noise of model with 300 stagger angle was the lowest in the low frequency(<80Hz)and the high frequency(1000?5000Hz).And in other frequency,the aerodynamic noise of model with 40° stagger angle was the lowest.In the low frequency(<100Hz),when the curvature ratio was 2.1,the aerodynamic noise of model was the lowest.In the middle and high frequency(100-1000 Hz),the model with 4.7 curvature ratio held the minimum aerodynamic noise.In the high frequency(1000?5000 Hz),the single-curve blade impeller had the lowest aerodynamic noise.And as the frequency increased over 5000 Hz,the aerodynamic noise of single-curve blade impeller turned into the highest.