In turbo-machinery, abradable layers are used to protect sensible components while keeping minimal possible clearances for maximum efficiency. This article describes the experimental comparison of state of the art abradable layers used as steam turbine seals and a new type of abradable layer made of a metallic felt. The comparison is done via abradability and leakage testing. The leakage is also compared to a state of the art analytical formula to show the effect on the thermal cycle calculation.
An abradable test rig is presented together with the test method. Test results show the value of the Felt seal compared to other two types at low contact speed area.
A steam test rig is also presented. Seal leakage at real operating conditions is evaluated and compared to an analytical formula. The leakage results show some efficiency gap compared to other two types of seals.