Diagnostic methods of a bladed disc mode shape evaluation used for shrouded blades in steam turbines

Strnad, Jaromir; Liška, Jindřich

doi:10.1088/1742-6596/659/1/012051

J. Phys.: Conf. Ser.

2015

DOI: 10.1088/1742-6596/659/1/012051

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Diagnostic methods of a bladed disc mode shape evaluation used for shrouded blades in steam turbines

Jaromir Strnad

Jindřich Liška

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Cited by 3 publications

(2 citation statements)

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“…=1 =1 (13) where Q ( ) and Q ( ) are the force amplitude and phase respectively corresponding to frequency component with engine order EO . If a travelling wave model of blade excitation is required, the phase angles are set according to the following formula [26] which is a corrected version of the one in [19]:…”

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confidence: 99%

An experimentally validated modal model simulator for the assessment of different Blade Tip Timing algorithms

Mohamed

Bonello

Russhard³

2020

Mechanical Systems and Signal Processing

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Blade Tip Timing (BTT) technology is concerned with the estimation of turbomachinery blade vibration. A BTT system comprises two parts: (a) measurement system for blade tip arrival times ("BTT data"); (b) the analysis algorithms. Simulators that generate BTT data play a key role in BTT development since they enable an assessment of the performance of the different BTT algorithms. Such assessments are not feasible with real engine data since they require controlled conditions and knowledge of the true tip vibration as the reference.Most simulators in the literature are based on a simple spring-mass-damper model and commercially available ones have no physical underpinning. This work presents a novel realistic simulator based on the experimentally validated Finite Element (FE) model of a bladed disk (blisk). Transformation to modal space enables the efficient generation of simulated BTT data regardless of the complexity of the blisk geometry. The simulator is then used in a first-time comparative study of three principal BTT algorithm methods (autoregressive, sine fitting, two-parameter plot) under various conditions involving synchronous and asynchronous excitations with both single and simultaneous frequencies.The study clarifies obscurities in the methods and demonstrates the applicability of each method to different BTT system scenarios.

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confidence: 99%

An experimentally validated modal model simulator for the assessment of different Blade Tip Timing algorithms

Mohamed

Bonello

Russhard³

2020

Mechanical Systems and Signal Processing

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“…( 4) with engine order EO , and i , f are the initial and final angular velocities (rad/s) respectively. The phase angles are set according to the following formula [27] in order to obtain the travelling wave model of blade excitation…”

mentioning

confidence: 99%

A novel method for the determination of the change in blade tip timing probe sensing position due to steady movements

Mohamed

Bonello

Russhard³

2019

Mechanical Systems and Signal Processing

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The correlation of blade tip timing (BTT) measurements against strain gauge (SG) measurements and finite element (FE) predictions includes a number of uncertainties. One of the main ones is the steady movement of the blades (i.e. change in their mean position and orientation). This causes the sensing positions of the probes relative to a blade tip to deviate from their intended (nominal) positions, leading to deceptive results for the BTT amplitude and the corresponding stress levels.Such movements are caused by variations in static loading conditions (thermal and pressure) associated with changes in the operating speed. A novel method is introduced for the determination of three basic types of blade tip steady movements: axial; lean; untwist. The method relies on linking the shift in the averages of the BTT data to a number of geometrical relations, depending on the type of movement. Not more than two probes (to be placed at different axial positions) are needed to measure all three types of movement. The method is validated by simulations using a novel BTT simulator, and by measurements from both a test rig and real engine tests. The validated results demonstrate the great potential of the method for practical applications.

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Rotating blades monitoring using standard turbine instrumentation

Liška

Jakl

Vasicek

2019

Proceedings of the Institution of Mechanical Engineers, Part C:

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Ensuring the reliability of the steam turbine is fundamental task for its proper operation. Early detection of any failure avoids material and financial losses. A very important task in turbomachinery diagnostics is monitoring of rotating blades vibration, especially in terms of the last stages of low-pressure turbine parts, where, in general, the vibration can reach the important level due the blades length. The commonly used methods are based on stress evaluation using strain gauges or on the non-contact measurement of blade tips – blade tip-timing (BTT) method. Rising demand for low-cost monitoring systems suitable for blade monitoring has led to development of a new approach based on signal processing of standard turbine instrumentation. The symptoms of blade vibration could be also visible in signals from relative shaft vibration (SV) sensors, which are standardly installed in turbine journal bearings. This paper illustrates the principles and possibilities of the approach based on processing of SV signals for monitoring of actual state of rotating blades. Finally, the comparison of parallel measurements using SV and BTT in operation of steam turbine reveals the properties and advantages of both methods.

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Diagnostic methods of a bladed disc mode shape evaluation used for shrouded blades in steam turbines

Cited by 3 publications

References 9 publications

An experimentally validated modal model simulator for the assessment of different Blade Tip Timing algorithms

An experimentally validated modal model simulator for the assessment of different Blade Tip Timing algorithms

A novel method for the determination of the change in blade tip timing probe sensing position due to steady movements

Rotating blades monitoring using standard turbine instrumentation

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