{'fraction_non_alphanumeric': 0.014144877839691384, 'fraction_numerical': 0.0, 'mean_word_length': 5.630681818181818, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Life assessment by fracture mechanics analysis and damage monitoring technique on combustion liners

A methodology has been developed and tested including a multi-disciplinary framework towards integrated analysis of gas turbine combustors. The sub-elements consist of combustion dynamics, stress and modal analysis, fracture mechanics and structural health monitoring have been interlinked indicating the damage evaluation to life assessment. The interaction between the interrelated combustion driven flame dynamics, acoustic pressure fluctuations and liner wall vibration has been investigated in the laboratory combustor test system. During the operation, the combustion, acoustics and wall vibrations have been coupled together. The dynamic combustion process generates high amplitude pressure oscillations resulting in vibration of the liner structure at about constant elevated temperature in base load operation. The thermo-acoustic instabilities have a significant destructive impact on the life of the liner material due to high cyclic vibration levels at high temperature. 
A structural health monitoring (SHM) method has been established to identify the damage, detect the flaw existence and determine the location, severity and progress of the damage for the combustion liners. Vibration-based and acoustic emission (AE) techniques have been applied in the test system to assess the structural behavior. The applicability of the technique has been tested by examining the dynamic modal parameters of the structure. The method enables a reliable assessment on the liner specimen at elevated temperatures by means of non-destructive evaluation under continuous operation of the combustor. The combustion liner specimen material has been assessed by calculating the near-tip fields at the crack tip by finite element based stress and fracture mechanics analysis. An algorithm based on J-Integral has been utilized to analyze the crack growth behavior under various loading conditions considering both linear and non-linear elastic fracture mechanics concepts. The location and the direction of the cracking on the liner specimen have been predicted. The presented work interrelates the different mechanisms in gas turbine combustors and the applicability of the concepts has been verified and validated in the test systems.