INVESTIGATION OF A NOVEL PRESSURE-ACTUATED BRUSH SEAL UNDER HOT STEAM CONDITIONS

Due to the increasing demand towards flexible operation of conventional power plants also the seals of their turbines have to adapt to varying loads. Based on the basic design of a clamped brush seal, a novel seal with a pressure-actuated backplate is introduced which is capable of combining the advantages of low and high inclined brush seals while avoiding their undesired properties for flexible operation. During preliminary investigations on a test rig operated with compressed air and without rotation, the functionality of the improved design was demonstrated. It is shown that the leakage mass flow was lowered by up to 40% while undesired bristle oscillations were reduced by up to 90% at low pressure differences compared to conventional seal designs. After the adaption of the design for subsequent investigations under realistic conditions comparable to those in a steam turbine, further tests were conducted at TU Braunschweig´s hot steam test rig. Within these investigations the novel design showed improved properties regarding a high leakage performance and an advanced capability to avoid deterioration due to shaft excursions compared to brush seals with fixed backplate design.