| In the pipe network system,the tee pipe is a commonly used as the pipe joint,which can be used to change the flow direction and the flow rate of the airflow at each outlet.Also,it’s widely used in aerospace,petrochemical and other industries.When the airflow flows through the bifurcation of the tee pipe,the flow field would be changed greatly due to the large change in the cross section of the flow channel,resulting in the increase of intensity of turbulence,even the unsteady flow phenomena,such as flow separation and the increase of pressure fluctuation.What’s more,the pressure fluctuation itself may induce severe noise in the cavity of the pipe.In the meantime,it’s more likely to occur the phenomena of resonance between the structure and the airflow when the frequency of pressure fluctuation is close to the modal frequency of structure,causing the occurrence of broken structure.Therefore,research was carried out in the aspect of flow field,noise and structure by means of experiment and numerical calculation.Firstly,the aerodynamic modeling experiments are carried out to investigate the characteristic of airflow pressure fluctuation under three different flow rates based on similarity theory and the differences of pressure fluctuation are then com Pared whether the guide device is mounted or not.It turns out that when the guide isn’t installed,the stability of airflow in bifurcation of the tee pipe is weak,which may easily lead to imbalanced distribution of pressure fluctuation between the two branches of the tee pipe.But along with the direction of airflow,the phenomena of imbalanced distribution gradually become weaker.However,compared with situation that the guide device isn’t installed,the guide device will greatly enhance the stabilities of upstream of airflow.As a result,the relative size of the standard deviation of pressure fluctuation between the two branches drops nearly 11%～22%,resulting in the improvement of imbalanced distribution of the pressure fluctuation between the two branches.Moreover,the standard deviation and the power spectrum of airflow pressure fluctuations at pipe bifurcation junction are reduced practically 38%-58%and 66%～88%,respectively.As for the one branch in the downstream with high airflow pressure fluctuation,the guide device helps reduce 16%-51%of airflow pressure fluctuation.In a word,the results shows that the guide device can significantly serve the purpose of stability of airflow at the upstream of the pipe as well as the enhancement of uniformity of the airflow.Secondly,based on the four-microphone transfer function method,the acoustical experiment is carried out to study the effect of guide device while the numerical calculation is also designed in the same condition.Compared with the experimental results,the results of calculation prove to reliable.As the results reveal,the sound in about 270 Hz,287 Hz,375 Hz and 440 Hz,can be effectively reduced owing to the guide device.Moreover,the sound in the wide frequency range of 2500 Hz～4500 Hz drops almost 18 db.Meanwhile,the sound from the inlet of the pipe always propagate to the two branches of the pipes with the same energy since it’s a symmetric tee pipe.Lastly,with the help of the ANSYS Mechanics,the modal analysis of the tee pipe is investigated.It turns out that the range of the natural frequencies of the pipeline is nearly 120 Hz～165 Hz.Therefore,in order to prevent the resonance of the tee pipe which may cause the pipeline rupture,some measures can be done like reducing the strength of excitation among these frequencies or increasing the restriction of the pipeline at those locations.The research helps to get better understanding of the characteristic of flow field,noise and structure of tee pipe,laying the foundation of the further research.Meanwhile,the guide device enriches the technical way of optimizing the flow field and sound field of the tee pipe,which has the engineering reference value. |
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