Wear mechanisms at the blade tip seal interface

Abradable seals are used at the interface between blade tips and compressor casings in modern gas turbine engines. These materials wear in preference to the blade tips leaving a track which perfectly fits the blades, thus improving sealing at the blade tip an increasing both efficiency and stall margin of the compressor.

The wear mechanisms occurring at this interface have been characterised for two common abradable materials. Changes to these mechanisms with blade speed, incursion rate and abradable hardness have been investigated and described statistically. The wear mechanisms proposed in this work and previously suggested have been used as the foundation for linear models which have been fitted to the results. These models have been used to test the quality of the mechanisms and indicate which processes are poorly understood.

The models were well correlated to results for forces with normally distributed residuals indicating rubbing force systems are well represented by the proposed mechanisms. Temperature and blade length change results were less well correlated indicating these processes are more poorly understood. This work shows that simple linear models based on a mechanistic understanding of underlying processes can be used for describing forces.