Effect Of The Multi-parameters On The Fluid-induced Force Of The Rotary Straight-through Labyrinth Gas Seal

The labyrinth seal in turbomachinery is a key element to restrict leakage flow among rotor-stator clearances from high-pressure regions to low-pressure regions.Its overall performance affects the aerodynamic efficiency of the turbomachinery,rotor stability and operational safety.The current trend in the high-performance turbomachine design requires more compact and higher-power machines with higher efficiencies because of the demand for higher rotor speeds and tighter clearances.This trend more accurately determines the rotor critical speeds,vibration levels,and onset of turbomachine instability.Numerous experimental investigations and field troubleshooting experiences have confirmed that the pressure-driven flow in the labyrinth seal can generate fluid-induced forces that become significant in some cases;thus,this flow strongly affects the stability of the machine.Although many studies have been performed to investigate the rotordynamic coefficients of the labyrinth seal,the fluid-induced force characteristics of labyrinth seals are not fully understood.Therefore,this paper chooses the influence of the multi-parameters on the fluid-induced force of the rotary straight-through labyrinth gas seal(RSTLGS)as the study object.To study the influence of the multi-parameters on the fluid-induced force characteristics of the RSTLGS,the this paper applies the numerical calculation method and research analysis method based on the computational fluid dynamics(CFD).The main research works are as follows:1.According to the operation condition and structure characteristic of the conventional straight-through labyrinth seal,the structure model of the RSTLGS is established.The fluid-induced force consists of the pressure force and viscous force on the surface of the rotor as the specific research object.Based on the CFD numerical calculation theory,the CFD numerical calculation method and the research analysis method to study the fluid-induced force characteristics of the RSTLGS are put forward.By the sealing experiment method,the CFD numerical calculation method is verified to better predict the leakage of the straight-through labyrinth gas seal leakage.The results show that the numerical simulation method can satisfy the research requirements of this paper.2.Influences of three kinds of operation parameters,including pressure drop,rotational speed and eccentricity,on the fluid-induced force of the RSTLGS are respectively researched using the CFD numerical calculation and analysis.The results show that the increasing pressure drop promotes the pressure force and viscous force,the increasing rotational speed inhibits the pressure force and promotes the viscous force.The increasing eccentricity inhibits the radial 'pressure force,radial and total viscous force and promotes the axial viscous force,axial and total pressure force,especially the changes of the radial and total pressure force are bigger.The multivariate regression analysis shows that the pressure drop is an important factor that affect the total pressure force,followed by the eccentricity.The pressure drop is the key factor that affect the total viscous force.3.Four kinds of inlet preswirls,consisting of axial preswirl velocity,radial preswirl angle,circumferential positive preswirl angle and circumferential negative preswirl angle,are established.The CFD numerical calculation method are used to study the our kinds of inlet preswirls on the fluid-induced force of the RSTLGS.The results show that the increasing axial preswirl velocity significantly inhibite the pressure force and viscous force on the surface of the rotor.A specific radial preswirl angle can make the pressure force and viscous force reach the extreme value.The increasing circumferential positive preswirl angle and circumferential negative preswirl angle significantly promote the pressure force and viscous force.The axial preswirl velocity,radial preswirl angle,circumferential positive preswirl angle and circumferential negative preswirl angle are the important factors that affect the fluid-induced force of the RSTLGS.Among them,the influence of the circumferential negative preswirl angle is the most,followed by the circumferential positive preswirl angle,and finally the axial preswirl velocity and radial preswirl angle.4.Effcets of five kinds of structural parameters,including inlet length,groove width,tooth width,tooth height and tooth number,on the fluid-induced force of the RSTLGS are respectively researched using the CFD numerical calculation method.The results show that the increasing tooth width,tooth height and tooth number inhibite the total pressure force and promote the total viscous force.The increasing inlet length and groove width promote the total pressure force and total viscous force.The multivariate regression analysis shows that the tooth number,is an important factor that affect the total pressure force,followed by the groove width,and other structural parameters have less influence.The inlet length is an important factor that affect the total viscous force and the inlet length,tooth number and groove width have certain influence.5.The inlet length,groove width,tooth width,tooth height and tooth number are the important factors that affect the fluid-induced force of the RSTLGS.Among them,the influence of the tooth number on the total pressure force is the most,followed by the groove width,and finally the tooth height and inlet length.Tooth width has the greatest influence on the total viscous force.6.Three kinds of clearance changes,consisting of tooth clearance,tooth divergence and tooth convergence,are designed.Three kinds of clearance changes on the fluid-induced force of the RSTLGS are computed and analyzed.The results show that the increasing tooth clearance,tooth divergence and tooth convergence promote the total pressure force.The increasing tooth clearance promote the total viscous force,and The increasing tooth divergence and tooth convergence inhibite the total viscous force.The tooth clearance,tooth divergence and tooth convergence are the important factors that affect the fluid-induced force of the RSTLGS.Among them,the influence of the tooth clearance is the most,followed by the tooth divergence,and finally the tooth convergence.This paper more comprehensively studied the influence of the multi-parameters on the fluid-induced force of the RSTLGS,especially for the inlet preswirl and clearance change.The conclusions of this paper not only helps to better understand the fluid-induced force characteristics of labyrinth seals,but also provides the theoretical basis for the control and optimization of the flow field of labyrinth seals.