Gas Turbine Compressor Blades Research Articles

Energy absorbing nano-porous Ti layers assisted erosion-corrosion resistant Ti/TiN multi-layered coatings for gas turbine compressor blades

Solid particle erosion (SPE) resistant coatings extend the life of gas turbine compressor blades and improve the safety of flights. Among different types of these coatings, nanolayered multi-layered and nanocomposite coatings proved to be more efficient. Further increase in the efficiency of these coatings can be achieved by introducing energy-absorbing metal porous layers. Here, we report the development of three different types of SPE and corrosion resistant Ti/TiN multilayer coatings (thickness ∼9 μm) on Ti6Al4V substrates using a sputtering technique. The coatings contain three stacks of Ti/TiN (7.3 nm) bi-layers separated by two energy-absorbing Ti layers of different porosity in each coating. The Ti film deposited at 4 mTorr chamber pressure showed a mix of ω and α phases with high porosity. The SPE studies were conducted according to ASTM-G76 standards at a temperature of 400 °C. The corrosion properties of the coatings were studied by potentiodynamic polarization in a 3.5 wt% NaCl solution. The coatings with energy-absorbing porous Ti layers showed better SPE-resistant performance compared to the coating with dense Ti layers. Whereas, vice versa behaviour was in the case of corrosion resistance performance. SPE mechanism is also analysed using field emission scanning electron microscopy images of erosion scars.

Synchronous Vibration Parameter Recognition of Constant-Speed Blades Based on Blade Tip Clearance Measurement

A new method for the synchronous vibration parameter identification of constant-speed rotating blades based on blade tip clearance (BTC) measurement and blade tip timing (BTT) is introduced. A BTC sensor is used to measure the BTC when the blade tip passes through each sensor. The BTT method is used to determine whether the blade tip arrives in advance or lags. The geometric model between the BTC and the blade tip vibration displacement (BTVD) is established, and the BTVD of the blade tip passing through each sensor is obtained. Then, the nonlinear least squares method is used to determine the synchronous vibration parameters of the constant-speed rotating blade. The results show that with an increase in amplitude, the higher the accuracy of the vibration parameter identification proposed in this paper; with a decrease in the random error of the BTC measurement, the higher the accuracy of the vibration parameter identification proposed in this paper; with a decrease in the random error in the measurement of the blade disk dimensions, the higher the accuracy of the vibration parameter identification proposed in this paper. In addition, the smaller the ratio of the blade length to the blade disk radius, the higher the accuracy of the vibration parameter identification method introduced in this paper. Because the structure of the gas turbine compressor and turbine blade disk has a small blade disk ratio, the method proposed in this paper is suitable for the simultaneous vibration parameter identification of gas turbine compressor blades and turbine blades.

Tip Rubbing as a Rare Metallurgical Root Cause of Gas Turbine Compressor Blade Failure

Tip Rubbing as a Rare Metallurgical Root Cause of Gas Turbine Compressor Blade Failure

Ferrite in the HAZ of Dissimilar Temperature Probe Welds

Abstract Protector tubes for temperature sensors were welded onto experimental gas turbine compressor blades. While the blades were made of a high alloy hard-martensitic stainless chromium steel, a high alloy metastable austenitic stainless steel was used for the tiny protector tubes. The dissimilar weld joint was applied using manual GTAW. A large amount of blocky delta ferrite formed in the HAZ immediately adjacent to the fusion line, on the side of the martensitic steel. Delta ferrite in such dissimilar welds might detrimentally affect the mechanical properties of the weld joint. It was therefore recommended not to use the affected experimental blades in test engine service. Even though no failure occurred in this case, one was prevented by declaring the subject instrumented parts unfit for test engine service.

Application of Machine Learning to Forced Response Predictions of an Industrial Axial Compressor Rotor Blade

Abstract Machine learning has gone way beyond a ground-breaking technology a few decades ago to now taken for granted in many day-to-day activities. It is now providing new ways for manufacturing, assembling, operating, monitoring, and maintaining products. Typical application areas include performance optimization, quality improvements, fault detection and predictive maintenance. In this paper application of machine learning algorithms to forced response prediction during the design and analysis of a typical gas turbine compressor blade is reported. The forced response prediction process typically involves utilizing harmonic or time domain computational fluid dynamics (CFD) analyses to compute the forcing and the aero damping, to calculate reserve factors that represent the high cycle fatigue life of the blade. This time-consuming process is generally limited to the later phases of the design cycle and can lead to hundreds of calculations if one must address all the resonances in a typical twin shaft running range. A neural network trained using historical data is used to directly predict the reserve factor with high confidence without the need for costlier high fidelity CFD by using just the finite elements (FE) predicted parameters. This allows to perform high-fidelity aero-mechanical assessment at an early stage in the design process. Further, application of image recognition using a convoluted neural network to aid in the identification of FE predicted Modeshapes is also demonstrated, which can also improve the quality of the reserve factor predictions.

An Experimental and Numerical Investigation of the Effect of Notches on the Root of Gas Turbine Compressor Blades on Critical Speeds

An Experimental and Numerical Investigation of the Effect of Notches on the Root of Gas Turbine Compressor Blades on Critical Speeds

Vibration characteristics of cracked compressor blades with different materials

Aiming at the influence of different material properties on the vibration characteristics of cracked gas turbine compressor blades, the vibration characteristics of cracked compressor blades with three different materials were studied by numerical calculation. The first order bending vibration of a cracked cantilever beam was simplified to a single degree of freedom system. The breathing crack stiffness model was introduced to change the elastic modulus and other parameters of the material. The fourth-order Runge-Kutta method and fast Fourier transform were used to obtain the cantilever beam vibration characteristic diagram, and the relationship between the material properties and the structural vibration was analyzed. The results show that the elastic modulus of the material is proportional to the stiffness, and the stiffness of the material affects the vibration displacement response of the cantilever beam, and the larger the stiffness is, the smaller the vibration displacement is.

Structural and Thermal Analysis of F Class Gas Turbine Compressor Blade

In this study, the structural and thermal analysis of the final stage compressor rotor blades, which are currently used on-site, is performed by using the ANSYS program. For that reason, a 3D model of the existing compressor blade has been done. Later on, this model was transferred to the ANSYS program and analyzed. In the analysis, the parameters formed in the blade geometry were determined. By creating a design geometry with the selected parameters, the stress of the existing blade under operating conditions was examined. All external parameters in this study were taken from an F-class gas turbine operating under real field conditions. The stresses of the obtained values in different regions on the blade were examined. This study is also a reverse engineering study and the effects of real field conditions on the compressor blades have been analyzed.

Effect of compressive residual stress on wear resistance of IGT25+ gas turbine compressor blades made of 1.4923 steel

Effect of compressive residual stress on wear resistance of IGT25+ gas turbine compressor blades made of 1.4923 steel

Thermal studies of big sheep horn as thermal barrier coating (TBC) material for gas turbine compressor blade

This research focuses on the decomposition temperature of a large sheep horn from Haveri District, Karnataka, India, which is 302.9?C. It also demonstrates the possible use of large sheep horn in the aerospace industry. It can be utilised as a Thermal Barrier Coating (TBC) in high-pressure compressor blades of jet engines. Because of its poor thermal conductivity and specific heat capacity, it is a superb insulator, and temperatures throughout the TBC take around 10 minutes to match.

Development of an accelerated test for pitting corrosion of CUSTOM 450 by rDHM

Abstract A key application of CUSTOM 450 alloy is in the construction of gas turbine compressor blades. The study of pitting corrosion can prevent the failure of many gas turbine compressor blades. In this study, a reflective digital holography microscopy method was employed to investigate the growth of pitting corrosion in depth. To this end, a constant potential of 350 mVSCE in a 3.5 wt.% NaCl solution was applied to the specimen. The generated pits were simulated in three dimensions, and it was indicated that pitting corrosion rate was decreased as time passed. Comparing the obtained experimental data with the data gathered from the real industrial environment surrounding a compressor installation, an accelerated test was proposed. By the proposed accelerated test, it is possible to produce a pit similar to the one that will be initiated and propagated at any time in the future in real conditions.

Effect of Tempering Temperature on Physical and Mechanical Properties of Martensitic Stainless Steel Repaired with Gtaw

One of the driving equipment to produce electricity that is widely used is gas turbines. To guarantee gas turbine can be operated according to its design and capacity, it is necessary to choose a material that is suitable for its operating conditions and working temperature. Commonly gas turbine compressor blade material is a martensitic stainless steel which has a high enough strength at the compressor working temperature. Damage that is often experienced occurs at the compressor blade and turbine blade. Gas tungsten arc welding (GTAW) build-up repair is one of the methods used to repair blades. This research was conducted to analyze the effect of tempering temperatures on martensitic stainless steel repaired with GTAW. Research was focus on mechanical properties and microstructure after repaired with GTAW and had heat treatment with various tempering temperatures. In the microstructure, all weld area of the specimens that were tempered at temperatures of 200, 500 and 600°C showed the same microstructure characteristics which consisted of a matrix of tempered martensite as well as chromium carbide. The size of tempered martensite at temperatures of 600°C is larger than 500 and 200°C. The strength and hardness of the material with a tempering temperature of 200°C is higher in value compared to tempering temperatures of 500°C and 600°C, while the toughness of the material with tempering temperature of 500°C is higher compared to 200°C and 600°C.

Simulation of pitting corrosion on gas turbine compressor blade

First row rotating blades of four axial-flow compressors were prematurely fractured. Previous investigations showed that the site atmosphere contains corrosive compounds which lead to an increase in possibility of pitting on the blades. To this end, experimental and numerical studies are considered. Replica testing, Scanning Electron Microscope (SEM) and fractography of the broken blade indicate that the pits join together and make one bigger pit under SCC mechanism which reduces the failure time. 3-D models of the pitting on the blade under existing forces are analyzed by COMSOL Multiphisics software. The simulation results show the location of maximum stress concentration inside one of the pits which is compatible with the location of initial SCC crack in the pit depth. Finite element analysis shows good similarities with fractography photos. Stress concentration and interaction of stresses around the pits are two mechanical reasons for initiation and growth of cracks. Calculations show that the occurrence of SCC at the location of the pit reduces the crack initiation time to half. The presence of pits increased the stress by approximately 130 MPa relative to the healthy blade. The part between the two pits with a stress of approximately 180 MPa showed the interaction of the two pits in the operating conditions of the compressor blade.

Application of modified Locati method in fatigue strength testing of a turbo compressor blade

The blades of axial turbomachines (steam and gas turbines, axial compressors) are highly stressed by centrifugal force, temperature, and alternating fluid forces, which leads to vibrations and fatigue cracking. This requires the studious engagement of designers and technologists. In this paper, a procedure for accelerated fatigue testing of a gas turbine compressor blade based on the modified Locati method is presented. The tests were performed on a vibration shaker with the frequency that equal the blade’s first natural frequency. S-N curves were estimated according to two approximate representation namely one-slope and two-slope models. Then, the blades were tested at different stress levels starting at a level below foreseen fatigue strength at the specified fatigue life. In each loading block, a blade was subjected to 2ˑ107 cycles. After the first block was completed, the stress level in the second loading block was increased by 20 MPa and a new 2ˑ107 cycles were applied. A procedure was repeated until the blade failure occurred. It was considered that a blade has failed when its natural frequency drops by more than 2%. After the failure, the fatigue strength was calculated using Palmgren -Miner rule.

Solid Particle Erosion Behaviour and Protective Coatings for Gas Turbine Compressor Blades—A Review

Gas turbines (GTEs) are often utilised in harsh environments where the GT components, including compressor vanes and rotor blades, are subject to erosion damage by sand and dust particles. For instance, in a desert environment, the rate of damage made by solid particles erosion (SPE) becomes severe, and therefore results in degradation to the GTE parts, lowering the cycle efficiency, reducing the device lifetime, and increasing the overall cost of the operation. As such, understanding the erosion mechanism caused by solid particles and the effects associated with it is crucial for selecting the appropriate countermeasures and maintaining the system performance. This review paper provides a survey of the available studies on SPE effects on GTEs and surface protective coatings. Firstly, the ductile and brittle SPE mechanism is presented, as well as the ductile-brittle transition region. Then, an in-depth focus on the parameters associated with the SPE, such as particles properties and impingement conditions, is introduced. Furthermore, the existing theoretical models are shown and discussed. Afterwards, erosion resistant coating materials for surface protection and their selection criteria are covered in the review. Finally, the gap in knowledge and future research direction in the field of SPE on GTEs are provided.

Role of bonding nature on the temperature dependent erosion behavior of solid materials: A detailed high temperature Raman spectroscopic analysis

Solid particle erosion is an unavoidable problem for gas turbine compressor blades, wind turbines, crude oil pipes, rovers in outer space, and other machine components operated in harsh conditions. Gas turbine components are usually operated in the temperature range of 100–1400 °C. However, the influence of temperature on the solid particle erosion mechanism has not been studied adequately. In this paper, the influence of temperature on the solid particle erosion properties of metals (Ti6Al4V, SS 304, Al-8011, and Ti/TiN multilayers) and non-metals (Al2O3, fused quartz, and Si) is studied. The erosion tests were conducted in the temperature range of 30–800 °C. The erosion rate of metallic and ionic solids (viz., Ti6Al4V, SS 304, Al-8011, Al2O3, and Ti/TiN multilayers with the thermal expansion coefficient α ≥ 8 μm/°C) initially decreased with increasing temperature and then increased at higher temperatures, whereas for covalently bonded materials such as fused quartz (α = 0.55 μm/°C) and Si (α = 2.6 μm/°C), the erosion rate increased with increasing temperature. As the temperature increases, it causes lattice vibrations and bond flexibility to increase the high thermal expansion coefficient materials due to their non-directional ionic or metallic bonds. It helps these materials to absorb the erodent energy without much damage, whereas the same does not happen in the case of low thermal expansion coefficient materials due to their strong directional covalent bonding. Temperature dependent Raman spectroscopic studies were carried out to understand the lattice vibrations and phase changes during heating.

Effects of substrate roughness on the surface morphology and corrosion properties of Fe- and Ni-aluminide coatings on martensitic stainless steel

Surface morphology affects several important characteristics of airfoils such as corrosion resistance, fouling and aerodynamic properties. In the current investigation different morphologies were developed on the surface of a martensitic stainless steel used for gas turbine compressor blade applications. A low temperature aluminide diffusion coating was applied on the steel substrates having low, intermediate and high average roughness values. The aluminizing treatment was carried out at 470 °C for 24 h in a powder mixture of Al, AlCl3 and Al2O3. Some of the substrates with intermediate roughness were received a Ni electrodeposition with 5, 10, and 20 μm thicknesses before aluminizing to investigate the resultant influence on the final morphology. Surface morphology and microstructure of the specimens were studied via FE-SEM, XRD and EDS analysis. The surface roughness of the specimens was studied via a stylus profilometer and their corrosion behavior was examined by the potentiodynamic polarization test. The results showed that the surface roughness of the substrate increases after aluminizing treatment but the final roughness can be reduced by applying an appropriate thickness of a Ni interlayer. The raising of the surface roughness reduced the corrosion rate of the uncoated steel specimens but revealed a weak beneficial effect on the aluminized specimens. Thicker Ni interlayers resulted in higher corrosion rates of nickel aluminide coatings.

Correction to: Effect of Porosity Parameters on the Strength of Gas Turbine Compressor Blades Made of Titanium Alloys

To the article “Effect of Porosity Parameters on the Strength of Gas Turbine Compressor Blades Made of Titanium Alloys,” by D. V. Pavlenko, Vol. 51, No. 6, pp. 887–899, November, 2019.

Effect of Porosity Parameters on the Strength of Gas Turbine Compressor Blades Made of Titanium Alloys

A study on the effect of pore space parameters of sintered titanium alloys on the strength margin of gas turbine compressor blades has been carried out. It is shown that the endurance of parts made of sintered titanium alloys synthesized from powder mixtures based on PT5 titanium powder obtained by the mechanical milling of a titanium sponge must be evaluated taking into account the peculiarities of the morphology of the pore space. An approach to taking into account the effect of the peculiarities of the morphology of the pore space on the endurance limit of gas turbine compressor blades has been proposed and experimentally evaluated using an analysis of the fractal dimension of pore boundaries. The results of experimental studies of the endurance limit of specimens of VT1-0, VT6, and VT8 titanium alloys, which have a different porosity, mean pore size and fractal dimension, are presented. A modeling of the stress-strain state of an airfoil of full-scale low-pressure compressor blades of a shaft gas turbine engine has been performed. The results of fatigue tests of full-scale compressor blades are presented. Based on fracture mechanics approaches, an improved model for the estimation of the endurance limit of specimens of sintered titanium alloys taking into account solid phase properties, pore size and morphology, and total porosity is proposed. A relationship relating the strength margin of full-scale compressor blades to the endurance limit of laboratory specimens, their porosity parameters and the loads acting during the operation of gas turbine engines is proposed. A calculation of the strength margin and the probability of non-failure of gas turbine compressor blades made of a sintered titanium alloy with different pore size and shape, and porosity has been made. Their maximum permissible values have been determined, at which the strength margin and the probability of non-failure of blades are provided, which meet the requirements of normative documents. It is shown that to provide the required value of the strength margin and probability of non-failure of blades, the process to manufacture them must include operations aimed at avoiding pores in the surface layer.

ESTIMATION OF THE STRESS-STRAIN STATE OF THE BLADE BASED ON INTERPROGRAM INTERACTION OF PROGRAM COMPLEXES

Basis of numerical simulation of turbulent viscous gas flow, using the Navier-Stokes equations averaged the Reynolds (RANS-model), a static analysis of the gas turbine compressor blade was performed. The simulation of flow parameters in three-dimensional formulation was carried out. For the solution of system of the equations the iterative differential scheme was built. The initial equations are integrated numerically by use of the iterative explicit and implicit differential scheme with a second order approximation. The differential two-parametrical SST Menter's model is used as a model of turbulence. As a result, distributed pressure and velocities in the blades channel were obtained and unfavorable flow zones were identified. At the second stage, was developed algorithm by which the interrelation of the gas-dynamic and mechanical calculation program was established. As a result, distributed pressure was applied to the finite-element model of the blade and a static analysis was performed. Static calculation makes it possible to calculate the stress-strain state of the construction.