Numerical Simulation Of Brush Seal Sealing Characteristics And Hysteresis

With power station steam turbine developing towards high temperature, highpressure, high speed and high load direction, steam leakage loss becomes a major lossof turbine, but advanced seal technology is one of the effective measures to reduceleakage loss. As a kind of advanced seal, although brush seal has gradually beenapplicated, the research which concerns about leakage flow characteristics of brushseal is still not comprehensive enough, the number of relevant theoretical research issmall, also, because of the limited experimental conditions and the limited value ofselected factors, there is a certain bias in the leakage flow characteristics reflectedon this basis.Numerical simulation of two-dimensional has been performed to study thesealing characteristics and hysteresis of brush seal using CFD (Computational FluidDynamics) software Fluent, the model is axisymmetric analysis model, the fluidmedium is compressible ideal gas, the solid wall boundary condition is adiabatic andnon-slip, the standard wall function is used by near-wall region, the turbulence modelis two-equation k-ε model.Based on the correctness of the selected model, the leakage flow characteristicsof brush seal at different protection heights、 brush beam thickness and radialclearance have been researched, results indicate that the protection height h isproportional to the leakage flow rate, is inversely proportional to the brushes pressuredistribution values near the back plate, when h<1.4mm, with the protection heightincreasing, the leakage flow rate increases in the form of a convex parabola, whenh>1.4mm, the leakage flow rate increases linearly; brush seal leakage flow rate andthickness of the beam is inverse proportion; the relationship between brush sealleakage flow rate and radial clearance becomes proportional, with the increase ofradial clearance, the region of pressure drop becomes larger along the radial direction,the deflection angle of the flow lines increases, and the location of the deflection occurring moves upstream along the axial direction.Secondly, the leakage flow characteristics of low hysteresis brush seal hasbeen researched, results indicate that the conventional brush seal sealingcharacteristics is similar to the rectangular brush seal’s, although the airfoil brushseal’s sealing characteristics is poor, compared with the previous two kinds of seal, itis less affected by the brush hysteresis; groove depth has little impact on the flowcharacteristics of low hysteresis brush seal; the axial clearance is proportional to theleakage flow rate of low hysteresis brush seal, with the increase of axial clearance, thepressure values at back plate reduce a lot except for the protection height region, andthe most obvious effect of the pressure drop can be obtained when the axial clearanceincreases from0mm to0.1mm. For practical engineering problems, usingappropriate axial clearance for low hysteresis brush seal’s structural optimization isfeasible.