Experimental Researches On The Gap Flow Field Visualization Of Labyrinth Seal And Seal Vibration Control Technology

The seal fluid flow characteristics in rotating machinery has lots of complexities.Vibration problems especially fluid excitations resulted by these flow characteristics have seriously puzzled the engineering reality for a long time.Thus,researches on the seal gap flow field are important and necessary.This paper applies particle image velocimetry technology(PIV)to the flow field measurement of labyrinth seal gap and has obtained the vector distribution,flow traces and turbulent kinetic energy distribution of labyrinth seal measurement section under 27 kinds of experiment conditions by changing the rotor speed and the chamber width-depth ratio.In order to solve the seal fluid excitation problem,the vibration control experiment based on magnetorheological damper and switch control strategy is conducted.For the wear and leakage issues of petrochemical plant steam turbine,a new seal composed of labyrinth and honeycomb seal is designed and installed instead of the original seal and it has successfully promoted the work efficiency of steam turbine.The main contents of this paper are as follows:(1)An experimental device consisted of labyrinth seal model and media loop which can be used to measure the inner flow field are designed and the labyrinth seal experiment device-PIV measurement system is established.The rotor speed and tooth pitch of the seal model can be changed to compose 27 kinds of measuring conditions during the experiment.Under these conditions,the vector distribution,flow traces and turbulent kinetic energy distribution of labyrinth seal measurement section are measured and studied.(2)According to the images measured by PIV,the velocity change law of the fluid in seal gap and each chamber along with the rotor speed and chamber width-depth ratio are analyzed.In the situation that the seal rotor is a cantilever beam,the flow fields of the seal with two different cantilever length rotors are compared and the rotor vibration effects to seal flow field are analyzed.Such of measurements and researches on seal gap flow field have provided experimental basis for the seal design and performance optimization.(3)As a new vibration control method,magnetorheological damper and the switch control strategy are used to control the seal vibration.The experimental results show that magnetorheologitcal damper and switch control can obviously decrease the seal vibration amplitude and play an auto-control role.The maximum amplitude drop value up to 68%.Meantime,the drop value increases with the work current increase.Thus,the vibration suppression effect can be enhanced by increasing the work current of magnetorheological.(4)The new seal composed of labyrinth and honeycomb seal can efficiently reduce the leakage of steam turbine in petrochemical plant and dramatically promote its work efficiency.In addition,the seal and rotor stability is also promoted and the steam turbine safe operation is ensured.