Dissertations / Theses: 'Low pressure turbine blade design'

1

McQuilling, Mark W. "DESIGN AND VALIDATION OF A HIGH-LIFT LOW-PRESSURE TURBINE BLADE." Wright State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=wright1189792837.

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2

Dickel, Jacob Allen. "Design Optimization of a Non-Axisymmetric Endwall Contour for a High-Lift Low Pressure Turbine Blade." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1534980581177159.

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3

Hansen, Laura C. "Phase Locked Flow Measurements of Steady and Unsteady Vortex Generator Jets in a Separating Boundary Layer." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd763.pdf.

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4

Hollon, Brian. "EXPERIMENTAL INVESTIGATION OF SEPARATION IN A LOW PRESSURE TURBINE BLADE CASCADE MODEL." UKnowledge, 2003. http://uknowledge.uky.edu/gradschool_theses/304.

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The flow field around a low pressure turbine blade is examined using smoke-wire flow visualization, static surface pressure measurements, and particle image velocimetry (PIV). The purpose of the experimental study is to investigate the transition and separation characteristics on low pressure turbine blades under low Reynolds number (Re) and varying freestream turbulence intensity (FSTI). A cascade model consisting of 6 Pratt andamp; Whitney PAK-B low pressure turbine blades was examined in a wind tunnel using PIV and flow visualization. Smoke-wire visualization was performed for test section exit angles of 93°, 95°, and 97°, in the range Re = 3 · 104 to 9 · 104 and three levels of FSTI varied with a passive grid. The locations of separation and transition were determined to be approximately 45% and 77% of the suction surface length, respectively, based upon the smoke stream lines observed in the images, and appear to be independent of Re, turning angle, and FSTI. The maximum size of the separation bubble was found to decrease with increasing Re, turning angle, and FSTI. PIV images from three camera views were processed for an exit angle of 95° and a Re range of 3:0 · 104 to 30:0 · 104 and three levels of FSTI. Velocity, vorticity, and reversed flow probability field plots were generated along with velocity, vorticity, and RMS velocity profiles. The point of separation point was determined to be from 63% SSL to 67% SSL. The area of reversed flow was computed for each image pair from camera views 1 and 3, as an approxiamtion of the relative size of the separation region. For low Re and FSTI cases the area was much larger than for higher FSTI cases at any Re. The raw PIV images include some of the rst clear pictures of the turbulent flow structures forming in the unsteady shear layer over the suction surface of low pressure turbine blades. Several movies are compiled that show how the geometry and location of the shear layer evolve in time for a given set of flow conditions.

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Ramakumar, Karthik. "ACTIVE FLOW CONTROL OF LOW PRESSURE TURBINE BLADE SEPARATION USING PLASMA ACTUATORS." UKnowledge, 2006. http://uknowledge.uky.edu/gradschool_theses/359.

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The current study examines plasma actuators as flow control devices. The actuators are placed on a turbine blade profile in a 2D turbine cascade for separation flow control. The configuration involves copper strips separated by a layer of dielectric material, across which an AC electric potential in the range of 5 kHz and 5 kV is applied. The efficiency of the actuator is monitored by measuring power input and flow control effectiveness. Preliminary observations are performed for a quiescent case on a flat plate profile to analyze the average and instantaneous velocities generated by the actuator for varied input parameters, such as waveform shape and frequency. Observations include the generation of starting and standing vortices that may be leveraged for unsteady flow control applications. In the case of turbine flow control, the Pratt andamp; Whitney Pak-B blade profile is used to determine the actuator performance for separation reduction at Reynolds number O(104). The results are compared with flow control on and off states for varied actuator input frequency, power, duty cycle and freestream velocity. Pressure measurements are conducted for the actuated case that show reduced separation and increased main flow velocity. Experimental diagnostics include PIV, 7-hole probe, and smoke-wire flow visualization techniques. Phase locked PIV performed at different forcing frequencies reveals the generation of cross-stream vortices providing re-attachment of the separated flow. During the off periods of the cycle the region of separation is observed to creep back to its original separation point. Various fields-of-view show the structure of these cross-stream vortices at different phases. While the actuator is seen to accelerate the flow in the immediate region of the plasma, the generation of starting vortices demonstrates that unsteady actuation is a more effective form of flow control.

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6

Bury, Mark Eric. "Influence of Reynolds number and blade geometry on low pressure turbine performance." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/50310.

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7

Verona, Claire L. "Stress corrosion cracking of low pressure steam turbine blade and rotor materials." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/10165.

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Stress corrosion cracking of a 14 wt% Cr martensitic stainless steel, with commercial names PH-15Cr5Ni, FV520B or X4CrNiCuMo15-5, used for the manufacture of low pressure turbine blades, has been studied with the intention of gaining a better understanding of the processes involved, how they occur and why. Industrially this is very important as stress corrosion cracking is considered to be a delayed failure process, whereby microscopic cracks can potentially propagate through a metal undetected until catastrophic failure occurs. The aim of this work is to establish links between crack length and external factors, such as exposure time, in order to devise a method of dating stress corrosion cracks and therefore predicting their possible occurrence in-service.

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8

He, Binyan. "Fatigue crack growth behaviour in a shot peened low pressure steam turbine blade material." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/388077/.

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9

Wang, Yuchen. "Blade Design of Vertical Axis Wind Turbine at Low Tip-speed-ratios." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524224348317784.

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10

McQuilling, Mark. "EXPERIMENTAL STUDY OF ACTIVE SEPARATION FLOW CONTROL IN A LOW PRESSURE TURBINE BLADE CASCADE MODEL." UKnowledge, 2004. http://uknowledge.uky.edu/gradschool_theses/320.

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The flow field around a low pressure turbine (LPT) blade cascade model with and without flow control is examined using ejector nozzle (EN) and vortex generator jet (VGJ) geometries for separation control. The cascade model consists of 6 Pak-B Pratt andamp; Whitney low pressure turbine blades with Re = 30,000-50,000 at a free-stream turbulence intensity of 0.6%. The EN geometry consists of combined suction and blowing slots near the point of separation. The VGJs consist of a row of holes placed at an angle to the free-stream, and are tested at two locations of 69% and 10.5% of the suction surface length (SSL). Results are compared between flow control on and flow control off states, as well as between the EN, VGJs, and a baseline cascade with no flow control geometry for steady and pulsatile blowing. The EN geometry is shown to control separation with both steady and pulsatile blowing. The VGJs at 69% SSL are shown to be much more aggressive than the EN geometry, achieving the same level of separation control with lower energy input. Pulsed VGJs (PVGJ) have been shown to be just as effective as steady VGJs, and results show that a 10% duty cycle is almost as effective as a 50% duty cycle. The VGJs at 10.5% SSL are shown to be inefficient at controlling separation. No combination of duty cycle and pulsing frequency tested can eliminate the separation region, with only higher steady blowing rates achieving separation control. Thus, the VGJs at 69% SSL are shown to be the most effective in controlling separation.

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11

Ssebabi, Brian. "Experimental evaluation of a low temperature and low pressure turbine." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86563.

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Thesis (MEng)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: The potential benefits from saving energy have driven most industrial processing facilities to pay more attention to reducing energy wastage. Because the industrial sector is the largest user of electricity in South Africa (37.7% of the generated electricity capacity), the application of waste heat recovery and utilisation (WHR&U) systems in this sector could lead to significant energy savings, a reduction in production costs and an increase in the efficiency of industrial processes. Turbines are critical components of WHR&U systems, and the choice of an efficient and low cost turbine is crucial for their successful implementation. The aim of this thesis project is therefore to validate the use of a turbine for application in a low grade energy WHR&U system. An experimental turbine kit (Infinity Turbine ITmini) was acquired, assembled and tested in a specially designed and built air test bench. The test data was used to characterise the turbine for low temperature (less than 120 Celsius) and pressure (less than 10 bar) conditions. A radial inflow turbine rotor was designed, manufactured and then tested with the same test bench, and its performance characteristics determined. In comparison with the ITmini rotor, the as-designed and manufactured rotor achieved a marginally better performance for the same test pressure ratio range. The as-designed turbine rotor performance characteristics for air were then used to scale the turbine for a refrigerant-123 application. Future work should entail integrating the turbine with a WHR&U system, and experimentally determining the system’s performance characteristics.
AFRIKAANSE OPSOMMING: Die potensiële voordele wat gepaard gaan met energiebesparing het die fokus van industrie laat val op die bekamping van energievermorsing. Die industriële sektor is die grootse verbruiker van elektrisiteit in Suid-Afrika (37.7% van die totale gegenereerde kapasiteit). Energiebesparing in die sektor deur die toepassing van afval-energie-herwinning en benutting (AEH&B) sisteme kan lei tot drastiese vermindering van energievermorsing, ‘n afname in produksie koste en ‘n toename in die doeltreffendheid van industriële prosesse. Turbines is kritiese komponente in AEH&B sisteme en die keuse van ‘n doeltreffende lae koste turbine is noodsaaklik in die suksesvolle implementering van dié sisteme. Die doelwit van hierdie tesisprojek is dus om die toepassing van ‘n turbine in ‘n lae graad energie AEH&B sisteem op die proef te stel. ‘n Eksperimentele turbine stel (“Infinity Turbine ITmini”) is aangeskaf, aanmekaargesit en getoets op ‘n pasgemaakte lugtoetsbank. Die toetsdata is gebruik om die turbine te karakteriseer by lae temperatuur (minder as 120 Celsius) en druk (minder as 10 bar) kondisies. ‘n Radiaalinvloeiturbinerotor is ook ontwerp, vervaardig en getoets op die lugtoetsbank om die rotor se karakteristieke te bepaal. In vergelyking met die ITmini-rotor het die radiaalinvloeiturbinerotor effens beter werkverrigting gelewer by diselfde toetsdruk verhoudings. Die werksverrigtingkarakteristieke met lug as vloeimedium van die radiaalinvloeiturbinerotor is gebruik om die rotor te skaleer vir ‘n R123 verkoelmiddel toepassing. Toekomstige werk sluit in om die turbine met ‘n AEH&B sisteem te integreer en die sisteem se werksverrigtingkarakteristieke te bepaal.

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12

Naicker, Leebashen. "Influence of heat treatment condition on the stress corrosion cracking properties of low pressure turbine blade steel FV520B." Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/25377.

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Stress corrosion cracking (SCC) is a corrosion phenomenon which continues to plague the power generating industry especially in low pressure (LP) steam turbine blades operating in the phase transition zone. An investigation has therefore been conducted to examine the effect of heat treatment condition on the microstructure, mechanical properties and SCC properties of one such LP turbine blade material, FV520B, used in the steam turbines of coal-fired power stations in South Africa. The three stage heat treatment cycle of the FV520B turbine blades consists of homogenisation at 1020°C for 30 minutes, solution treatment at 790°C for two hours and precipitation hardening at 545°C for six hours. In this study, the precipitation hardening temperature was varied in the range 430-600°C to investigate how this variation would affect the material and SCC properties. Hardness and tensile testing were performed to obtain mechanical properties while the investigative techniques used to characterise the microstructures were light microscopy, dilatometry, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Stress corrosion susceptibility for the different heat treatment conditions was quantified using U-bend specimens while crack growth rates and threshold stress intensities for SCC (KISCC) were measured using fatigue precracked wedge open loaded (WOL) specimens. Both SCC tests were conducted in a 3.5% NaCl environment maintained at 90°C. XRD results revealed the presence of reverted austenite in the higher tempered specimens due to the precipitation hardening temperature being close to the Ac1 temperature for the material. The presence of reverted austenite was shown to adversely affect mechanical strength and hardness which decreased with increasing precipitation hardening temperature. Light and electron microscopy (SEM and TEM) revealed the presence of Cr-rich precipitates along the prior austenite grain boundaries in all tested heat treatment conditions. The propensity, quantity and size of the Cr-rich precipitates increased as the specimen temper temperature increased. SCC susceptibility was shown to be dependent upon yield strength and decreased as precipitation hardening temperature increased with specimens in the overaged condition showing no cracking after more than 5000 hours in the test environment. WOL testing only produced cracking in the three highest strength specimens after 2000 hours. Crack growth rates and threshold stress intensities were found to be dependent on yield strength and decreased with increasing precipitation hardening temperature. Analysis of fracture surfaces revealed crack propagation along prior austenite grain boundaries in all test heat treatment conditions indicating intergranular stress corrosion cracking (IGSCC) as the dominant cracking mechanism.

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13

Jia, H.-X., G. Xi, L. Müller, R. Mailach, and K. Vogeler. "Effect of clocking on unsteady rotor blade loading in a low-speed axial compressor at design and off-design operating conditions." Sage, 2008. https://publish.fid-move.qucosa.de/id/qucosa%3A38439.

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This paper presents the results of stator clocking investigations at a design point and an operating point near the stability limit in a low-speed research compressor (LSRC). The unsteady flow field of the LSRC at several clocking configurations was investigated using a three-dimensional unsteady, viscous solver. The unsteady pressure on the rotor blades at midspan (MS) was measured using time-resolving piezoresistive miniature pressure transducers. The effect of clocking on the unsteady pressure fluctuation at MS on the rotor blades is discussed for different operating points. Based on the unsteady profile pressures, the blade pressure forces were calculated. The peak-to-peak amplitudes of the unsteady blade pressure forces are presented and analysed for different clocking positions at both the design point and the operating point near the stability limit of the compressor.

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14

Cranstone, Alexander William. "Low pressure turbine design for a future high bypass ratio aero-engine." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610530.

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15

Cencelli, Nicolette Arnalda, Bakstrom T. W. Von, and T. S. A. Denton. "Aerodynamic optimisation of a small-scale wind turbine blade for low windspeed conditions." Thesis, Stellenbosch : Stellenbosch University, 2006. http://hdl.handle.net/10019.1/353.

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Thesis (MScEng (Department of Mechanical and Mechatronic Engineering))--Stellenbosch University, 2006.
ENGLISH ABSTRACT: Wind conditions in South Africa determine the need for a small-scale wind turbine to produce useable power at windspeeds below 7m/s. In this project, a range of windspeeds, within which optimal performance o the wind turbine is expected, was selected. The optimal performance was assessed in terms of the Coefficient of Power(Cp), which rates the turbines blade's ability to extract energy form the avalible wind stream. The optimisation methods employed allowed a means of tackling the multi-variable problem such that the aerodynamic characteristics of the blade were ideal throughout the wind speed range. The design problem was broken down into a two-dimensional optimisaion of the airfoils used at the radial stations, and a three-dimensional optimisation of the geometric features of the wind rotor. by means of blending various standard airfoil profiles, a new profile was created at each radial station. XFOIL was used for the two-dimensional analysis of these airfoils. Three-dimensional optimisn involved representation of the rotor as a simplified model and use of the Blade Element Momentum(BEM) method for analysis. an existimg turbine blade, on which the design specifications were modelled, was further used for comparative purposes throughout the project. The resulting blade design offers substantial improvements on the reference design. The application of optimisation methods has successfully aided the creation of a wind turbine blade with consistent peak performance over a range of design prints.
Sponsored by the Centre for Renewable and Sustainable Energy Studies, Stellenbosch University

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16

Seumangal, Nicole. "Influence of the heat treatment procedure on the stress corrosion cracking behaviour of low pressure turbine blade material FV566." Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/27427.

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Stress corrosion cracking is one of the leading damage mechanisms in low-pressure turbines in the power generation industry; in LP turbine blades it primarily occurs in the last stage blades. The research investigated the influence of tempering temperature on the microstructure, mechanical properties, and stress corrosion cracking properties of 12% chromium FV566 stainless steel, which is used to manufacture LP turbine blades. The standard heat treatment of the steel comprises of austenitising, quenching and double tempering. Austenitising is carried out at 1050°C for one hour - which is sufficiently long to generate a fully austenitic matrix and to dissolve carbon completely. Subsequently, the material is quenched in air. The high level of alloying elements ensures the complete martensitic transformation, with carbon atoms trapped in the matrix and distributed homogeneously. Thereafter, tempering of the material at 580-600°C enhances the ductility and toughness. Tempering replaces the solid solution strengthening of the dissolved carbon with precipitation strengthening by carbides. The final microstructure of the FV566 steel blades is referred to as tempered martensite. van Rooyen showed that for 12% chromium steel tempering at and above 600°C induces passivity of the material against SCC, while tempering of 12% chromium steels at 450-550°C causes sensitisation of the material and the material exhibits intergranular SCC. From such studies, the motivation arises to investigate the impact of heat-treatment parameters - specifically the impact of tempering temperature on the stress corrosion behaviour of the material. The testing methodology comprises heat treatment of FV566 samples at 1050°C for 1 hour, at 350°C for 1 hour, and thereafter tempering for 1 hour at various tempering temperatures. Each stage of heat treatment is followed by air cooling - followed by analysis of the microstructure, mechanical testing and stress corrosion cracking testing of the specimens at the different temper conditions. Stress corrosion testing was divided into two categories. The first set of tests was carried out with U-bend specimens to determine the susceptibility of materials at different heat treatments to SCC, the time taken for SCC to initiate, and the mode of cracking. The second set of tests was conducted to determine the threshold stress intensity, as a function of crack growth rate, for each heat treatment. The SCC failure mechanism observed was intergranular SCC (IGSCC) by anodic dissolution for the 550°C, 560°C, 570°C, 580°C, 590°C, 600°C and 620°C specimens. The material's resistance to SCC improved with increasing tempering temperature. Specimens tempered at 480°C and 550°C were most susceptible to SCC, while specimens tempered at 600°C The material's resistance to SCC improved with increasing tempering temperature. Specimens tempered at 480°C and 550°C were most susceptible to SCC, while specimens tempered at 600°C were immune to SCC in a 4000-hour period. A change in tempering temperature results in a change in the quantity and type of precipitates formed which results in changes in SCC properties of FV566.

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17

Oksuz, Ozhan. "Multiploid Genetic Algorithms For Multi-objective Turbine Blade Aerodynamic Optimization." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12609196/index.pdf.

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To decrease the computational cost of genetic algorithm optimizations, surrogate models are used during optimization. Online update of surrogate models and repeated exchange of surrogate models with exact model during genetic optimization converts static optimization problems to dynamic ones. However, genetic algorithms fail to converge to the global optimum in dynamic optimization problems. To address these problems, a multiploid genetic algorithm optimization method is proposed. Multi-fidelity surrogate models are assigned to corresponding levels of fitness values to sustain the static optimization problem. Low fidelity fitness values are used to decrease the computational cost. The exact/highest-fidelity model fitness value is used for converging to the global optimum. The algorithm is applied to single and multi-objective turbine blade aerodynamic optimization problems. The design objectives are selected as maximizing the adiabatic efficiency and torque so as to reduce the weight, size and the cost of the gas turbine engine. A 3-D steady Reynolds-Averaged Navier-Stokes solver is coupled with an automated unstructured grid generation tool. The solver is validated by using two well known test cases. Blade geometry is modelled by 37 design variables. Fine and coarse grid solutions are respected as high and low fidelity surrogate models, respectively. One of the test cases is selected as the baseline and is modified in the design process. The effects of input parameters on the performance of the multiploid genetic algorithm are studied. It is demonstrated that the proposed algorithm accelerates the optimization cycle while providing convergence to the global optimum for single and multi-objective problems.

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18

Lipfert, Martin [Verfasser]. "Unsteady Aerodynamics of a Low Pressure Turbine at Off-Design Operation / Martin Lipfert." München : Verlag Dr. Hut, 2015. http://d-nb.info/1079768971/34.

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19

Pluim, Jonathon Douglas. "DESIGN OF A HIGH FIDELITY WAKE SIMULATOR FOR RESEARCH USING LINEAR CASCADES." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1244039010.

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20

Ozturk, Burak. "Combined effects of Reynolds number, turbulence intensity and periodic unsteady wake flow conditions on boundary layer development and heat transfer of a low pressure turbine blade." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1150.

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21

Fletcher, Nathan James. "Design and Implementation of Periodic Unsteadiness Generator for Turbine Secondary Flow Studies." Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1560810428267352.

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22

Mathison, Randall Melson. "Experimental and Computational Investigation of Inlet Temperature Profile and Cooling Effects on a One and One-Half Stage High-Pressure Turbine Operating at Design-Corrected Conditions." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1250281163.

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23

Stephens, Julia Elizabeth. "Control of the tip-gap flow of a low pressure turbine blade in a linear cascade." 2009. http://etd.nd.edu/ETD-db/theses/available/etd-04072009-101828/.

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Thesis (Ph. D.)--University of Notre Dame, 2009.
Thesis directed by Thomas C. Corke for the Department of Aerospace and Mechanical Engineering. "April 2009." Includes bibliographical references (leaves 181-185).

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24

Waite, Joshua Joseph. "Physical Insights, Steady Aerodynamic Effects, and a Design Tool for Low-Pressure Turbine Flutter." Diss., 2016. http://hdl.handle.net/10161/12264.

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The successful, efficient, and safe turbine design requires a thorough understanding of the underlying physical phenomena. This research investigates the physical understanding and parameters highly correlated to flutter, an aeroelastic instability prevalent among low pressure turbine (LPT) blades in both aircraft engines and power turbines. The modern way of determining whether a certain cascade of LPT blades is susceptible to flutter is through time-expensive computational fluid dynamics (CFD) codes. These codes converge to solution satisfying the Eulerian conservation equations subject to the boundary conditions of a nodal domain consisting fluid and solid wall particles. Most detailed CFD codes are accompanied by cryptic turbulence models, meticulous grid constructions, and elegant boundary condition enforcements all with one goal in mind: determine the sign (and therefore stability) of the aerodynamic damping. The main question being asked by the aeroelastician, ``is it positive or negative?'' This type of thought-process eventually gives rise to a black-box effect, leaving physical understanding behind. Therefore, the first part of this research aims to understand and reveal the physics behind LPT flutter in addition to several related topics including acoustic resonance effects. A percentage of this initial numerical investigation is completed using an influence coefficient approach to study the variation the work-per-cycle contributions of neighboring cascade blades to a reference airfoil. The second part of this research introduces new discoveries regarding the relationship between steady aerodynamic loading and negative aerodynamic damping. Using validated CFD codes as computational wind tunnels, a multitude of low-pressure turbine flutter parameters, such as reduced frequency, mode shape, and interblade phase angle, will be scrutinized across various airfoil geometries and steady operating conditions to reach new design guidelines regarding the influence of steady aerodynamic loading and LPT flutter. Many pressing topics influencing LPT flutter including shocks, their nonlinearity, and three-dimensionality are also addressed along the way. The work is concluded by introducing a useful preliminary design tool that can estimate within seconds the entire aerodynamic damping versus nodal diameter curve for a given three-dimensional cascade.

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25

kuveya, Khanyisile Rose. "A study towards the development of the laser shock peening technology for an Eskom power station low pressure steam turbine blade application. To also compare the impact of laser shock peening without coating against shot peening treatment on 12%Cr steel." Thesis, 2018. https://hdl.handle.net/10539/26784.

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A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in fulfilment of the requirements for the degree of Master of Science in Engineering, under the supervision of Professor Claudia Polese,2018
The root section of a turbine blade is the most critical part as it forms the structural bond of the turbine blade to the shaft. If not maintained correctly the blade could fail catastrophically due to high and low cycle fatigue, stress corrosion cracking as well as corrosion fatigue. The sources of loading on the blades vary from normal operation, excitation of natural frequencies during transient occasions and overloads during statutory testing. Different surface modification technologies can be put in place to improve blades in-service performance. The present study is aimed at comparing previous results achieved from Shot Peening (SP) of an equivalent turbine blade to those achieved by Laser Shock Peening without coating (LSPwC).The SP data which is used for comparison is from the work and study done to optimise the SP of a 12Cr steel steam turbine blade. It is expected that LSPwC processing of the blade will result in a reduction in mean surface roughness (Ra), and deeper compressive residual stresses than the conventional SP processing. The focus of this investigation is also to determine the effects of LSPwC laser and processing parameters, such as laser intensity, laser spot size, coverage, water layer, and possibly laser wavelength on the X12CrNiMo12 high strength steel target material. Segments of an ex-service turbine blade, 20x20mm by 10mm thickness, processed at the CSIR National Laser Centre under various LSPwC parameters were analysed as follows: composition properties confirmed by spark tests; surface integrity assessed by SEM and 3D roughness mapping; microstructure; residual stress measurements by laboratory X-ray Diffraction. The experimental results helped in optimizing the LSPwC parameters for the X12CrNiMo12, before applying LSPwC to the more complex geometry of the blade root. This study then allowed for the determination of which peening process is most suited for turbine components.
XL2019

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Dissertations / Theses on the topic 'Low pressure turbine blade design'

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