High temperature rub in rig for compressor casings
The SEAL-COAT project has resulted in a much better and more fundamental understanding of abradability. An abradable coating means that if it rubs against a more abrasive material in motion, the former will be worn whereas the latter will not. The material is used in coatings in the compressor and turbine sections of aircraft engines. Here, minimal clearance is required between the blade tips and casing, while taking into account thermal expansion. A large enough clearance must be used to prevent the tip from catastrophically contacting the casing. Therefore, abradable coatings must not only allow for closer clearances, but also to automatically adjust clearances, in-situ, while the device is operating. Before newly developed coatings such as abradables can be applied to engines they must first be thoroughly tested. The SEAL-COAT project originally designed a device for testing new abradables under conditions that were as realistic as possible. The test temperature of the device, known as a rub in rig, was limited to 650°C. Because engine performance can be improved by increasing the pressure ratio, compressors experience higher temperatures. Therefore, higher test temperatures of up to 750°C were required for the test rig. The SEAL-COAT team modified the existing rub in rig with a new heating system and with a new unit for controlling the heating system. Through this upgrade they were able to test abradables for future applications, both for themselves and on behalf of customers who require their unique services. This work is applicable not only to the aero-engine market but also to gas turbines for power generation, pump compressors and engine turbochargers.
