Effect of bristle pack position on the rotordynamic characteristics of brush-labyrinth seals at various operating conditions

Over the last few decades,the research on the effect of bristle pack position on the rotordynamic characteristics of the brush-labyrinth seals is not sufficient.To this end,two kinds of brush-labyrinth seals for the bristle pack element installed upstream of the labyrinth teeth named BSU and installed downstream of the labyrinth teeth called BSD were used to investigate the effect of bristle pack position on the rotordynamic characteristics of the brush-labyrinth seals.Using the numerical model combining the porous medium model and the whirling rotor method,the rotordynamic characteristics of the BSU and BSD at various operating conditions including four kinds of pressure ratios,five kinds of inlet preswirl speeds and four kinds of rotor spinning speeds were conducted.The obtained results show that the effects of operating conditions on rotordynamic coefficients for the different seal configurations are different.The direct stiffness,cross-coupled stiffness and direct damping of the BSU are lower than those of the BSD.The rotordynamic coefficients of the BSU are more insensitive to the operating conditions variation.From the perspective of the seal stability,the BSU is a better brush-labyrinth seal configuration at high pressure ratio,high positive preswirl or high rotor spinning speed conditions.While in the case of low pressure ratio,low positive preswirl or low rotor spinning speed conditions,the BSD is a better choice.

Effect of hole arrangement patterns on the leakage and rotordynamic characteristics of the honeycomb seal

The honeycomb seal is a vital component to reduce the leakage flow and improvethe system stability for the turbomachines. In this work, a three-dimensional model is established for the interlaced hole honeycomb seal (IHHCS) and the non-interlaced hole honeycombseal (NIHHCS) to investigate its leakage and rotordynamic characteristics by adopting computational fluid dynamics (CFD). Results show that the hole arrangement patterns have littleimpact on the pressure drop and turbulence kinetic energy distribution for the seals, and theIHHCS possesses a slightly lower leakage flow rate than the NIHHCS. Moreover, the numericalresults also show that the NIHHCS possesses a better rotordynamic performance than theIHHCS at all investigated conditions. Both seals show a larger k and a lower Ceff with the increase of the positive preswirl ratios and rotational speeds, while the negative preswirl ratioswould reduce the k and improve the Ceff. The NIHHCS possesses a higher absolute value ofFt for all operating conditions, this could explain the distinction of Ceff for both seals atdifferent working conditions.

Rotordynamic characteristics prediction for scallop damper seals using computational fluid dynamics

Enhancing damping characteristic is one of the effective methods to solve the instability problem of the rotor system.The three-dimensional numerical analysis model of scallop damper seal was established,and the effects of inlet pressures,preswirl ratios,rotational speeds,interlaced angles and seal cavity depths on the rotordynamic characteristics of scallop damper seal were studied based on dynamic mesh method and multi-frequencies elliptic whirling model.Results show that the direct stiffness of the scallop damper seal increases with decreasing inlet pressure and increasing rotational speed and cavity depth.When the seal cavity is interlaced by a certain angle,which shows positive direct stiffness.The effective damping of the scallop damper seal increases with the increasing inlet pressure,the decreasing preswirl ratio and the rotational speed and cavity depth.There exists an optimal interlaced angle to maximize the effective damping and the system stability.The leakage of the scallop damper seal is significantly reduced with decreasing inlet pressure.The preswirl will reduce the leakage flowrate,and the rotational speed has a slight effect on the leakage performance.The leakage of the scallop damper seal decreases with increasing seal cavity depth.