Analysis Of Flow Field And Optimization Of Noise Elimination For Chemical Gas Turbine Inlet Pipe

The mechanical vibration of the gas pipeline caused by the flow contraction and expansion while the chemical gas turbine is working,which causes the noise pollution to the surrounding environment,affects the physical and mental health of the construction workers and reduces the production efficiency.Such noise is aerodynamic noise.However,the intensity and distribution of noise in different working environment and the distribution of flow field of the gas pipeline will be different in different working environment.Therefore,carrying out the research work on the flow field,acoustic property of the intake pipe of the chemical gas turbine is of great importance to be clear of the flow field and noise distribution of the intake pipe and taking measures to reduce the noise.In this paper,the gas turbine intake pipe of a large environmental protection equipment Co.,Ltd.is taken as the research object.The flow field and sound field of the intake pipe are simulated by the computational mechanics(CFD)and the acoustic finite element method(Acoustics-FEM).The specific work is as follows:(1)Firstly,the intake noise source and production mechanism of the chemical gas turbine,the theory and research status of CFD and acoustics,and the simulation application software are expounded.On this basis,the research contents,methods and technical line of this paper are put forward.(2)Secondly,the pressure,velocity,turbulence distribution,pressure loss and distortion parameters of the inlet and outlet are obtained and the flow field characteristics of the intake pipe is analyzed by the simulation of the internal flow field of the intake pipeline in Fluent,The results show that there is negative pressure in the inlet pipe outlet,which improves the exchange rate of the surrounding air flow;the flow velocity of the intake pipe and the air kinetic energy increases from the inlet to outlet,which is beneficial to the rotating blades of chemical gas turbines.The flow field characteristics of the pipe is appropriate to the standard.(3)Thirdly,the transmission losses of the intake pipe without considering the influence of air flow and within the effect of air flow are calculated by Virtual.Lab,the internal sound field and the transfer loss of the inlet and outlet are analyzed and compared according to the simulation results.The results show that the transmission loss curve fluctuates greatly,the frequency width of the peak attenuation peak is narrow,and the transmission loss in all frequency is lower than the standard,so it is supposed to take measures to reduce the noise;The airflow field is of little importance to the acoustic characteristics when the Maher value is less than 0.3.It provides a reference for the subsequent noise reduction scheme.(4)The internal flow field and transmission losses of the acoustic pipeline are simulated by Fluent and calculated by Virtual.Lab respectively.The pressure,velocity,turbulence distribution,pressure loss,distortion parameters and transmission loss of the inlet and outlet were obtained.The flow field characteristics of the intake pipe and the acoustic transmission loss are analyzed,and the flow field and acoustic simulation results of the intake pipe are compared with the results of the acoustic simulation.The results show that the performance of the pipes with mufflers decreases slightly,the pressure loss is eligible while the flow uniformity is unqualified.The acoustic properties improve greatly,but the transmission loss in 20~60Hz and 160~460Hz is lower than the standard value.(5)Finally,the optimization requirements of the muffler are stated.The influence of the thickness and quantity of the sound absorbing material and the guide angle of the soundboard on the flow field characteristics and the influence of the structure factor,flow resistance,porosity,thickness,quantity and the guide angle of the sound plate on the acoustic performance of the silencer are studied.The structural parameters of the muffler are determined by combined the requirements of the muffler design and the results of the influence of each parameter.Finally,the flow field and the acoustic field of the anechoic pipe are simulated,of which the results is compared and analyzed with the simulation results of the intake pipe,which show that the structure of the muffler is appropriate,of which the acoustic and flow field characteristics all accord with the requirements for the construction site,and provides theoretical basis and reference for the design of chemical gas turbine muffler.