• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.1
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• pp.24-33
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• 1999

For performance prediction and diagnostics of gas turbine engines, linear and non-linear gas path analysis are applied. In order to find optimal instrument parameters to detect the physical faults such as (outing, erosion and corrosion, non-linear gas path analysis is used. A typical industrial gas turbine engine, TB5000, is used to study the effect of physical faults on engine performance. Through comparison of RMS error between linear and non-linear gas path analysis, the optimal instrument parameters can be defined. As a result, it is found that the linear GPA has the level of error introduced by the assumption of the linear mode: can be of the same order of magnitude as the fault being soughtwhile the non-linear GPA can be solved the non-linear relationships between dependent and independent parameters using an iterative method such as the Newton-Raphson method with sufficient accuracy.

• Wind and Structures
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• v.31 no.3
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• pp.217-227
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• 2020

Based on translation models, both Gaussian and non-Gaussian wind fields are generated using spectral representation method for investigating the influence of non-Gaussian characteristics and directivity effect of wind load on fatigue damage of wind turbine. Using the blade aerodynamic model and multi-body dynamics, dynamic responses are calculated. Using linear damage accumulation theory and linear crack propagation theory, crack initiation life and crack propagation life are discussed with consideration of the joint probability density distribution of the wind direction and mean wind speed in detail. The result shows that non-Gaussian characteristics of wind load have less influence on fatigue life of wind turbine in the area with smaller annual mean wind speeds. Whereas, the influence becomes significant with the increase of the annual mean wind speed. When the annual mean wind speeds are 7 m/s and 9 m/s at hub height of 90 m, the crack initiation lives under softening non-Gaussian wind decrease by 10% compared with Gaussian wind fields or at higher hub height. The study indicates that the consideration of the influence of softening non-Gaussian characteristics of wind inflows can significantly decrease the fatigue life, and, if neglected, it can result in non-conservative fatigue life estimates for the areas with higher annual mean wind speeds.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.11a
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• pp.59-60
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• 2018

The oscillating-water-column wave energy converter represents the complex physical characteristics associated with the water column, turbines, generator, and power converter. This study focuses on the derivation of the physical relationship between the water column and turbine based on the 1/ 4 scale model test. The aerodynamic characteristics of the OWC ducted turbine were simulated using an orifice. The turbine effect, a key element in the OWC-chamber performance evaluation, can be represented by the flow rate and pressure drop through the orifice. The turbine effect of OWC-WEC was confirmed to have a non-linear relationship from the measured flow rate and pressure drop in the model test.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.1
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• pp.69-75
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• 2001

Linear GPA(Gas Path Analysis) and non-linear GPA programs for performance diagnostics of a turboprop engine were developed, and a study for selection of optimal measurement variables was performed. Simultaneous faults in the compressor, the compressor turbine and the power turbine, which occur damage of the engine, were assumed. The non-linear GPA analysis was carried out with an iterative method, where the performance degradation rate of independent parameters was divided into same intervals. It was compared with the result by the Newton-Raphson method for observing the effect of an iterative method. According to the analysis result, it was found that performance of non-linear GPA can be influenced on the type of the iterative method. For showing effects of the number of measurement variables both the linear and non-linear GPAs were analyzed with 10, 8 and 6 measurement sets, respectively. RMS error between them were compared each other. It was realized that the more measurement parameters are used, and the more accurate result may be obtained. However much better result can be obtained with measurement parameters selected properly Moreover, RMS error by using non-linear GPA was less than that by using linear GPA.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.256-263
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• 2008

The assumed modes method is developed to derive a set of linear differential equations describing the motion of a flexible wind turbine blade and to propose an approach to investigate the forced responses result from various wind excitations. In this work, we have adopted Euler beam theory and considered that the root of the blade is clamped at the rigid hub. And the aerodynamic parameters and forces are determined based on Blade Element Momentum (BEM) theory and quasi-steady airfoil aerodynamics. Numerical calculations show that this method gives good results and it can be used fur modeling and the forced vibration analysis including the coupling effect of wind-turbine blades, as well as turbo-machinery blades, aircraft propellers or helicopter rotor blades which may be considered as straight non-uniform beams with built-in pre-twist.

• Advances in aircraft and spacecraft science
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• v.4 no.1
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• pp.37-52
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• 2017

Gas turbines operating in dusty or sandy environment polluted with micron-sized solid particles are highly prone to blade surface erosion damage in compressor stages and molten sand attack in the hot-sections of turbine stages. Commercial/Military fixed-wing aircraft engines and helicopter engines often have to operate over sandy terrains in the middle eastern countries or in volcanic zones; on the other hand gas turbines in marine applications are subjected to salt spray, while the coal-burning industrial power generation turbines are subjected to fly-ash. The presence of solid particles in the working fluid medium has an adverse effect on the durability of these engines as well as performance. Typical turbine blade damages include blade coating wear, sand glazing, Calcia-Magnesia-Alumina-Silicate (CMAS) attack, oxidation, plugged cooling holes, all of which can cause rapid performance deterioration including loss of aircraft. The focus of this research work is to simulate particle-surface kinetic interaction on typical turbomachinery material targets using non-linear dynamic impact analysis. The objective of this research is to understand the interfacial kinetic behaviors that can provide insights into the physics of particle interactions and to enable leap ahead technologies in material choices and to develop sand-phobic thermal barrier coatings for turbine blades. This paper outlines the research efforts at the U.S Army Research Laboratory to come up with novel turbine blade multifunctional protective coatings that are sand-phobic, sand impact wear resistant, as well as have very low thermal conductivity for improved performance of future gas turbine engines. The research scope includes development of protective coatings for both nickel-based super alloys and ceramic matrix composites.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.270-275
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• 2008

In this study, computer applied engineering (CAE) techniques are full? used to conduct structural and dynamic analyses of a huge composite rotor blade. Computational fluid dynamics is used to predict aerodynamic load of the rotating wind-turbine blade model. Static and dynamic structural analyses are conducted based on the non-linear finite element method for composite laminates and multi-body dynamic simulation tools. Various numerical results for aerodynamic load, dynamic analyses are presented and characteristics of structural behaviors are investigated herein.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.10
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• pp.1383-1389
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• 2013

There were telecommunication noise and malfunctions of the electronic devices occurred over a wide area due to the high harmonic voltage and/or current levels of the Back-to-back converter in the DFIG wind power system even though the magnitude of all harmonics is within the international standards. The triangular carrier signals of the PWM used in the power converter system is related to the telecommunication noise because they are in the range of audible frequencies and amplified by a variety of the standing waves that were excited by harmonic voltage sources in the weak grid system such as a long distance distribution transmission lines. This paper describes the characteristics of the harmonics in the wind turbine-generator, numerical analysis and simulation of the harmonics resonance phenomena in the distribution lines as well as measuring induced voltage of the telecommunication lines in parallel with power lines in order to verify the root cause of the telecommunication noise. These noise problems can occur in a wind turbine power system with a non-linear converter at any time, as well as photovoltaic power system. So, the preliminary review of suitable filter devices and switching frequencies of the PWM have to be required by considering the stability of the controller at the design stage but as part of the measures the effect of the telecommunication cable shields was analyzed by comparing the measured data between multi-conductor with/without shields so as to attenuate the sources of the harmonics voltage induced into the telecommunication lines and to apply the most cost-effective measures in the field.