A Review of NDT/Structural Health Monitoring Techniques for Hot Gas Components in Gas Turbines

Mevissen, Frank; Meo, Michele

doi:10.3390/s19030711

Cited by 69 publications

(57 citation statements)

References 206 publications

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“…SX blades contain highly complex inner passages, called cooling channels as shown in Figure 1 [3]. These channels use convection cooling to maintain a lower blade temperature by using [9] under the terms of the Creative Commons Attribution 4.0 License from http://creativecommons.org/licenses/by/4.0/), and (d) cracked turbine blades (Reproduced from [9] under the terms of the Creative Commons Attribution 4.0 License from http://creativecommons.org/lice nses/by/4.0/).…”

Section: Background On Sx Turbine Blades-materials and Production Promentioning

confidence: 99%

“…Regulations dictate that once the blade tip loses a set amount of material, it may no longer be employed and must be repaired or scrapped. Additionally, fatigue cracks and other forms of damage (Figure 3b-d) [9]) at the shank, the dovetail, and the bottom of the airfoil limit the life of the turbine blades. Currently, when an SX turbine blade is damaged at the tip, it is typically repaired one to three times before being scrapped where it is either be reverted to regain its constituent materials or scrapped as waste (Based on our conversation with John Apostol, Principal Engineer-GEnx Program, American Airlines, Dallas, TX, USA).…”

Section: Introductionmentioning

confidence: 99%

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On the Fabrication of Metallic Single Crystal Turbine Blades with a Commentary on Repair via Additive Manufacturing

Angel

Basak

2020

JMMP

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The turbine section of aircraft engines (both commercial and military) is an example of one of the most hostile environments as the components in this section typically operate at upwards of 1650 °C in the presence of corrosive and oxidative gases. The blades are at the heart of the turbine section as they extract energy from the hot gases to generate work. The turbine blades are typically fabricated using investment casting, and depending on the casting complexity, they generally display one of the three common microstructures (i.e., equiaxed or polycrystalline, directionally solidified, and single crystal). Single crystal casting is exotic as several steps of the casting process are traditionally hands-on. Due to the complex production process involving several prototyping iterations, the blade castings have a significant cost associated with them. For example, a set of 40 single crystal turbine blades costs above USD 600,000 and requires 60–90 weeks for production. Additionally, if the components suffer from material loss due to prolonged service or manufacturing defects, the traditional manufacturing methods cannot restore the parent metallurgy at the damage locations. Hence, there is a significant interest in developing additive manufacturing (AM) technologies that can repair the single crystal turbine blades. Despite the blades’ criticality in aircraft propulsion, there is currently no review article that summarizes the metallurgy, production process, failure mechanisms, and AM-based repair methods of the single crystal turbine blades. To address this existing gap, this review paper starts with a discussion on the composition of the single crystal superalloys, describes the traditional fabrication methods for the metallic single crystal turbine blades, estimates the material and energy loss when the blades are scrapped or reverted, and provides a summary of the AM technologies that are currently being investigated for their repair potential. In conclusion, based on the literature reviewed, this paper identifies new avenues for research and development approaches for advancing the fabrication and repair of single crystal turbine blades.

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Section: Background On Sx Turbine Blades-materials and Production Promentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On the Fabrication of Metallic Single Crystal Turbine Blades with a Commentary on Repair via Additive Manufacturing

Angel

Basak

2020

JMMP

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“…Temperature mapping of gas turbine rotor blades is extremely important both for condition health monitoring and blade design optimization. Infrared thermography allows contactless measurements of the rotor blade surface temperature in gas turbines [28], but the mapping between the 2D image and the 3D blade requires adequate camera calibration. Thus, the blade itself has to be used as the calibration frame: indeed, its geometry is well known, and usually, an accurate 3D model is available.…”

Section: Introductionmentioning

confidence: 99%

Camera Calibration with Weighted Direct Linear Transformation and Anisotropic Uncertainties of Image Control Points

Barone

Marrazzo²,

Otón

2020

Sensors

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Camera calibration is a crucial step for computer vision in many applications. For example, adequate calibration is required in infrared thermography inside gas turbines for blade temperature measurements, for associating each pixel with the corresponding point on the blade 3D model. The blade has to be used as the calibration frame, but it is always only partially visible, and thus, there are few control points. We propose and test a method that exploits the anisotropic uncertainty of the control points and improves the calibration in conditions where the number of control points is limited. Assuming a bivariate Gaussian 2D distribution of the position error of each control point, we set uncertainty areas of control points’ position, which are ellipses (with specific axis lengths and rotations) within which the control points are supposed to be. We use these ellipses to set a weight matrix to be used in a weighted Direct Linear Transformation (wDLT). We present the mathematical formalism for this modified calibration algorithm, and we apply it to calibrate a camera from a picture of a well known object in different situations, comparing its performance to the standard DLT method, showing that the wDLT algorithm provides a more robust and precise solution. We finally discuss the quantitative improvements of the algorithm by varying the modules of random deviations in control points’ positions and with partial occlusion of the object.

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“…Non-contact blade vibration measurement, known as blade tip-timing (BTT) or Non-Intrusive Stress Measurement System (NSMS), is a technique for determining dynamic blade stresses to ensure the structural integrity of bladed disks in jet engines and stationary turbines [1,2]. It can be used in axial or radial compressors [3] and unshrouded or shrouded turbines [4].…”

Section: Introductionmentioning

confidence: 99%

Non-Contact Measurement of Blade Vibration in an Axial Compressor

Przysowa

Russhard²

2019

Sensors

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Complex blade responses such as a rotating stall or simultaneous resonances are common in modern engines and their observation can be a challenge even for state-of-the-art tip-timing systems and trained operators. This paper analyses forced vibrations of axial compressor blades, measured during the bench tests of the SO-3 turbojet. In relation to earlier studies conducted in Poland with a small number of sensors, a multichannel tip-timing system let us observe simultaneous responses or higher-order modes. To find possible symptoms of a failure, blade responses in a healthy and unhealthy engine configuration with an inlet blocker were studied. The used analysis methods covered all-blade spectrum and the circumferential fitting of blade deflections to the harmonic oscillator model. The Pearson coefficient of correlation between the measured and predicted tip deflection is calculated to evaluate fitting results. It helps to avoid common operator mistakes and misinterpreting the results. The proposed modal solver can track the vibration frequency and adjust the engine order on the fly. That way, synchronous and asynchronous vibrations are observed and analysed together with an extended variant of least squares. This approach saves a lot of work related to configuring the conventional tip-timing solver.

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A Review of NDT/Structural Health Monitoring Techniques for Hot Gas Components in Gas Turbines

Cited by 69 publications

References 206 publications

On the Fabrication of Metallic Single Crystal Turbine Blades with a Commentary on Repair via Additive Manufacturing

On the Fabrication of Metallic Single Crystal Turbine Blades with a Commentary on Repair via Additive Manufacturing

Camera Calibration with Weighted Direct Linear Transformation and Anisotropic Uncertainties of Image Control Points

Non-Contact Measurement of Blade Vibration in an Axial Compressor

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