High cycle fatigue is a factor that influence gas turbine buckets lifetime and it’s due to high frequency vibrations during service. Rotation and fluid flow around the blades cause static and dynamic stresses on the buckets row. For this reason the natural frequencies and HCF resistance evaluation are fundamental in the design phase of gas turbine engines in order to avoid resonance problems during service. Single crystal and directionally solidified superalloys shows anisotropic material properties, in particular single crystal can be modeled as orthotropic material in lattice directions for FEM simulations purposes. In this paper the influence of the lattice growth orientation, identified by two angles, on the natural frequencies of first stage bucket has been investigated. Six-sigma analysis has been performed in order to obtain a transfer function between lattice orientation and bucket vibration. The Design of Experiment (DoE) has been performed using FEA modal results on ten different vibration modes. The results obtained by FEA are verified by an experimental test on the real Heavy Duty MS5002 buckets.

With the increasing use of renewable energy sources, Gas Turbines (GTs) are currently required to accomplish more flexible operations for supplying the back-up energy. As a result, thermo-mechanical fatigue issues in the GTs components are emphasized. In this paper, the design of a novel rig for assessing the fatigue behavior in the trailing edge of full scale GTs blades is presented. Based on a detailed Finite Element (FE) analysis of the blade response under thermo-mechanical loads, it is demonstrated that the stress and strain cycles arising in this area during a start-up/shut-down transient can be accurately reproduced by clamping the blade in the shank zone and applying a transversal load to\ud the trailing edge. It is also shown that the stress/strain states can be obtained using a Test Article (TA) extracted from the actual blade. In this configuration, the load magnitude and direction, and the distance of the application point from the blade platform are the test control parameters. A FE model simulating the TA test is developed to determine the test parameters. A tooling for clamping and loading the TA is finally proposed along with a rig apparatus consisting of standard equipment used in material testing

The NovaLT™16 gas turbine recently developed in Baker Hughes, a GE company (BHGE), is part of a larger class of gas turbines (LT class) aiming at covering a wide space in the small power range segment and at introducing in the market a state of the art technology engine for what concerns performance, emissions, operability, durability and maintainability. The main purpose of this paper is to describe the entire validation campaign that was performed at BHGE facilities. This campaign can be divided into 3 different phases. The first phase focused on measuring engine performance in a new, clean and unaltered configuration. The second phase focused on emissions, vibration, thermal distribution, auxiliary system performances and the like, in order to validate the design assumption and calculation results across the full operational range. In this phase, more than 2000 sensors were installed across the entire engine, covering all modules, and all functional tests were performed (inside and outside of design space) to guarantee reliable engine behavior. At the end of this test phase, a full engine teardown was performed to allow a detailed parts inspection that confirmed the achievement of the design intent. The standard maintenance plan of the engine requires 35Kh continuous running. Therefore, the third part of the test aimed at validating engine durability with a full endurance test that allowed the identification and correction of any possible remaining operation problem. In this phase, the engine was still equipped with more than 1000 sensors, and was operated continuously following a well-defined operating profile in order to simulate both mechanical drive and power generation modes. This campaign successfully allowed to fine tune several engine control logic details, to monitor emissions behavior across a wide range of ambient temperature and load condition (the test spans from hot to cold day), to analyze trends of standard engine parameters and special instrumentation and, through planned borescope inspection, to evaluate individual component status versus selected operating profile. Data reported in this paper represent a summary of all the data acquired and post processing results, and illustrate how an endurance test can help tuning machine performance predictions in a wide operating range.

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In the oil and gas industry, manufacturers are continuously engaged in providing machines with improved performance, reliability and availability. First Stage Bucket is one of the most critical gas turbine components, bearing the brunt of very severe operating conditions in terms of high temperature and stresses; aeromechanic behavior is a key characteristic to be checked, to assure the absence of resonances that can lead to damage. Aim of this paper is to introduce a method for aeromechanical verification applied to the new First Stage Bucket for heavy duty MS5002 gas turbine with integrated cover plates. This target is achieved through a significantly cheaper and streamlined test (a rotating test bench facility, formally Wheel Box Test) in place of a full engine test. Scope of Wheel Box Test is the aeromechanical characterization for both Baseline and New bucket, in addition to the validation of the analytical models developed. Wheel Box Test is focused on the acquisition and visualization of dynamic data, simulating different forcing frequencies, and the measurement of natural frequencies, compared with the expected results. Moreover, a Finite Elements Model (FEM) tuning for frequency prediction is performed. Finally, the characterization of different types of dampers in terms of impact on frequencies and damping effect is carried out. Therefore, in line with response assessment and damping levels estimation, the most suitable damper is selected. The proposed approach could be extended for other machine models and for mechanical audits.