Contact Mechanics and Material Removal in Abradable Linings

Abradable linings are used within compressors and turbines as they allow blade tip clearances to be minimised, whilst not suffering the penalty of blade tip wear. They are of particular interest in aero-engines, where they help to improve engine efficiency and minimise the consumption of aviation fuel. This proposal is concerned with investigating cutting type wear experienced by abradable linings, during the incursion of a blade tip into the lining. Previous studies have considered the process to be similar to that of high speed machining, whereas recent observations from engine tests have indicated that debris is in fact ejected from the rear of the contact.In this study a demonstrator platform will be developed for simulating aero-engine compressor rubs, and the associated contact mechanics investigated using an ultrasonic technique in combination with a finite element model. Through this approach, material failure points will be identified, and insight gained as to why debris is ejected from the rear of the contact. Blade tip geometries will also be investigated as part of this study, as well as their effect on material removal. This topic area is particularly pertinent as aero-engine manufacturer's looks to minimise blade tip clearances further inorder to increase engine efficiency, thus increasing the frequency of abrasion events.

As was highlighted in the Case for Support, research into abradable linings is extremely pertinent as they significantly influence the efficiency of turbo-machinery. Further, as designers currently look to utilise systems for dynamically controlling blade tip clearances, the topic area of micro-rubs becomes particularly important. The novel investigative work in this study directly engages with this issue, and will be of interest to both aero-engine and turbo-machinery manufacturers. Specifically, the topic area of abradable linings in aero-engine compressors has been selected as the research platform, as it is the highest impact area for the topic due to the incursion rates experienced by the linings during flight. It is planned that dissemination will target both senior industrial figures as well as more specific practitioners. This will be performed through technical reporting and presentation at conference events, as well as through focused workshop events for engineers directly involved in the topic. Due to the link with Rolls-Royce, part of the dissemination will take place through Integrated Project Team meetings to in part fulfil the latter requirement. This work also has wider impact with regards to measuring contact pressures from a dynamic contact. The techniques demonstrated here offer the prospect of developing a condition monitoring tool, whereby the evolution of a dynamic contact due to wear can be considered. In light of this, technical seminars and events related to condition monitoring will also be targeted.