During shut down process, aeroengines cools mainly by buoyant convection. Within relatively closed casing, hot air rises and cold air falls, which develops a uneven temperature-distributed field. In such a field, thermal gradient can make differential thermal expansion, causing the compressor shaft to bow. Starting engines with thermal bow will increase vibration of rotor. Even worse, rubbing between rotors and stator will cause further asymmetric heating of the bowed rotor, and subsequently increased thermal distortion, which is called Newkirk Effect. What's worse, thermal bow is so serious that areoengine can't start. So far, few experimental researches have been made on thermal bow of rotor about static tests and dynamic response in lab. The difficulty and innovation of experiment is developing an uneven temperature field similar to that in real casing. By building such a casing in which can develop temperature difference in radial and axial direction, static temperature distribution and structure deformation tests and dynamic experiments of rotor with thermal bow are carried out. Based on the rotor for one certain type of aeroengine, the paper describes an experiment of thermal bow failure，in which uneven temperature field can be simulated. In static experiment, it can be concluded that temperature difference of all cross sections goes up with the increase of heating temperature. In addition, it has close connection with the structure. The maximum temperature difference occurs in the middle segment of rotor whose radius is maximum. It takes least time to eliminate temperature difference for the segment with minimum radius. Cold blowing can effectively and quickly reduce temperature difference than natural cooling. Meanwhile, the regulation of rotor deformation shows highly agreement with that of temperature difference. As for dynamic experiment, the vibration of rotor is intensified due to the occurrence of thermal bow. The larger the temperature difference is, the larger the amplitude becomes. That's because deformation caused by temperature difference increases mass imbalance of rotor. The deformation is more similar to the mode of first order vibration than other modes, so the vibration when rotation speed is near 2365r/min and 2892 r/min increases obviously. Besides, thermal bow influence the fundamental frequency vibration. With the increase of cooling time, vibration amplitude of rotor reduces gradually. And that's the most important feature of thermal bow different from initial mass imbalance. Cold blowing is still the most effectively and quickly measure.

Key words: Aeroengine; Temperature difference; Thermal bow; Structural deformation; Cold blowing; Vibration.


Experimental Research on the Characteristics of Thermal Bow in an Aeroengine HP Spool

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

Turbo Expo - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.