Brush Seals in Industrial Gas Turbines

Brush seals have demonstrated reductions in parasitic leakage flow in aircraft engines. The same benefits in leakage reduction and performance improvement can be realised in industrial gas turbines. Moreover, as a baseload machine will typically run in excess of 8000 hours per year, the value of the resulting fuel savings and/or extra power generated is significant. While the application of brush seals to industrial gas turbines is conceptually similar to that to aircraft engines, there are some important differences. These include larger diameters and thicknesses, larger tolerance bands, split casings with the accompanying ellipticity and segmented seals, fewer transient excursions, constant synchronous speed, no landing or maneuver loads, longer operating life requirements, and, in the case of field retrofitting, the robustness to withstand field installation. Brush seals have been designed for and installed in the GE E Class turbine high pressure packing (compressor discharge) and middle bearing locations. The development included tribological tests, leakage tests, secondary flow path modelling, and field tests. Results from field installations to date and from the marketplace are very positive.