The inlet temperature of modern gas turbine engines has been increased to achieve higher thermal efficiency and increased output. The blade edge regions, including the blade tip, the leading edge, and the platform, are exposed to the most extreme heat loads, and therefore, must be adequately cooled to maintain safety. For the blade tip, there is tip leakage flow due to the pressure gradient across the tip. This leakage flow not only reduces the blade aerodynamic performance, but also yields a high heat load due to the thin boundary layer and high speed. Various tip configurations, such as plane tip, double side squealer tip, and single suction side squealer tip, have been studied to find which one is the best configuration to reduce the tip leakage flow and the heat load. In addition to the flow and heat transfer on the blade tip, film cooling with various arrangements, including camber line, upstream, and two row configurations, have been studied. Besides these cases of low inlet/outlet pressure ratio, low temperature, non-rotating, the high inlet/outlet pressure ratio, high temperature, and rotating cases have been investigated, since they are closer to real turbine working conditions. The leading edge of the rotor blade experiences high heat transfer because of the stagnation flow. Film cooling on the rotor leading edge in a 1-1/2 turbine stage has been numerically studied for the design and off-design conditions. Simulations find that the increasing rotating speed shifts the stagnation line from the pressure side, to the leading edge and the suction side, while film cooling protection moves in the reverse direction with decreasing cooling effectiveness. Film cooling brings a high unsteady intensity of the heat transfer coefficient, especially on the suction side. The unsteady intensity of film cooling effectiveness is higher than that of the heat transfer coefficient. The film cooling on the rotor platform has gained significant attention due to the usage of low-aspect ratio and low-solidity turbine designs. Film cooling and its heat transfer are strongly influenced by the secondary flow of the end-wall and the stator-rotor interaction. Numerical predictions have been performed for the film cooling on the rotating platform of a whole turbine stage. The design conditions yield a high cooling effectiveness and decrease the cooling effectiveness unsteady intensity, while the high rpm condition dramatically reduces the film cooling effectiveness. High purge flow rates provide a better cooling protection. In addition, the impact of the turbine work process on film cooling effectiveness and heat transfer coefficient has been investigated. The overall cooling effectiveness shows a higher value than the adiabatic effectiveness does.

Detailed film cooling effectiveness distributions were measured on the stationary blade tip and on the leading edge region of a rotating blade using a Pressure Sensitive Paint technique. Air and nitrogen gas were used as the film cooling gases and the oxygen concentration distribution for each case was measured. The film cooling effectiveness information was obtained from the difference of the oxygen concentration between air and nitrogen gas cases by applying the mass transfer analogy. In the case of the stationary blade tip, plane tip and squealer tip blades were used while the film cooling holes were located (a) along the camber line on the tip or (b) along the span of the pressure side. The average blowing ratio of the cooling gas was controlled to be 0.5, 1.0, and 2.0. Tests were conducted in a five-bladed linear cascade with a blow down facility. The free stream Reynolds number, based on the axial chord length and the exit velocity, was 1,100,000 and the inlet and the exit Mach number were 0.25 and 0.59, respectively. Turbulence intensity level at the cascade inlet was 9.7%. All measurements were made at three different tip gap clearances of 1%, 1.5%, and 2.5% of blade span. Results show that the locations of the film cooling holes and the presence of squealer have significant effects on surface static pressure and film-cooling effectiveness. Same technique was applied to the rotating turbine blade leading edge region. Tests were conducted on the first stage rotor of a 3-stage axial turbine. The Reynolds number based on the axial chord length and the exit velocity was 200,000 and the total to exit pressure ratio was 1.12 for the first rotor. The effects of the rotational speed and the blowing ratio were studied. The rotational speed was controlled to be 2400, 2550, and 3000 rpm and the blowing ratio was 0.5, 1.0, and 2.0. Two different film cooling hole geometries were used; 2-row and 3-row film cooling holes. Results show that the rotational speed changes the directions of the coolant flows. Blowing ratio also changes the distributions of the coolant flows. The results of this study will be helpful in understanding the physical phenomena regarding the film injection and designing more efficient turbine blades.

Ceramics can highly withstand the environments of high temperature and serious erosion, it completely substitutes for alloys which reach their specific limitations. Turbine rotor operates in the compressed stage with temperature over thousand Celsius degrees; it must rely on excellent properties of ceramics to elevate the durability and lifetime. To manufacture complex ceramic component before, industry usually uses near net shaping or rapid prototyping (RP) processes. A manufacturing process based on machining green ceramic turbine component is presented here. Initially, formulating a series of machining experiments for green ceramics to verify the idea of thesis, and analyzing the probability of Al2O3 ceramic as a turbine material. Firstly, it needs to check the machinability of green ceramic by face milling. Secondly, point milling the normal plate of green compact and the plate with analogical blade geometry to find a set of usable machining parameters (such as revolution speed, feed rate, step over and cutting depth); meanwhile, addressing machining amendment by observing the final conditions of specific geometric characteristics on workpiece. Finally, try to machining green ceramic turbine successfully applying the above parameters.

In this work, the time varying stresses in a Howden axial flow fan are obtained by finite element analyses. Dynamic substructuring is used to obtain accurate values of the stresses in the threads of the blade shaft, the component which connects the blade with the hub. Three different global models are used to compare the influence of neglecting the fan shaft and the stiffness influence of the centrifugal force. The relative displacements, which are obtained from the global models, have been used as boundary condition in the detailed models. The detailed models are used to obtain the Von Mises stresses in the root of the threads of the blade shaft. Finally the results of the three global models are compared with experimental measured data provided by Howden. The experimental data results in the highest Von Mises stresses. The model with the fan shaft and the stiffness influence of the centrifugal force gives values for the Von Mises stresses which are approximately twenty percent lower. The model without the fan shaft results in the lowest stresses which are approximately forty percent lower than the stresses obtained using the measured data.

This work studies the effects of radial flow on the aerodynamic phenomena occurring on a retreating blade with a focus on dynamic stall and reverse flow as applied to both a helicopter rotor in forward flight and a wind turbine operating at a yaw angle. While great progress has been made in understanding the phenomenon of two-dimensional dynamic stall, the effect of rotation on the dynamic stall event is not well understood. Experiments were conducted on a rigid two bladed teetering rotor at high advance ratios in a low speed wind tunnel. Particle image velocimetry (PIV) measurements were used to quantify the flow field at several azimuthal angles on the rotating blade during the dynamic stall event. The effect of centrifugal forces induced ``pure'' radial velocity on the dynamic stall event at 270 degrees azimuth was studied in detail. Further investigation of the radial flow field suggested that the mean radial velocity attenuated on moving outboard due to an apparent shear layer instability and it was demonstrated to be of first order importance in the flow field. These radial flow results prompted an exploration of the flow over a rotating disk to establish similarities of the radial flow over rotating blade in separated flow to that over a rotating disk in separated flow. While a greater part of this work focused on aspects of dynamic stall on the retreating blade, the final parts focus on the exotic flow regime of reverse flow (characterized by flow from the trailing edge to the leading edge of the blade). Aerodynamic loads measurement and surface flow visualization via tufts are used to first quantify the behavior of a static yawed blade in reverse flow. PIV measurements are then used on a static yawed blade and a rotating blade in reverse flow conditions to ascertain the effects of rotation on reverse flow.

Time-frequency analysis techniques are proposed as a necessary tool for the analysis of acoustics generated by helicopter transient maneuvering flight. Such techniques are necessary as the acoustic signals related to transient maneuvers are inherently unsteady. The wavelet transform is proposed as an appropriate tool, and it is compared to the more standard short-time Fourier transform technique through an investigation using several appropriately sized interrogation windows. It is shown that the wavelet transform provides a consistent spectral representation, regardless of employed window size. The short-time Fourier transform, however, provides spectral amplitudes that are highly dependent on the size of the interrogation window, and so is not an appropriate tool for this situation. An extraction method is also proposed to investigate blade-vortex interaction noise emitted during helicopter transient maneuvering flight. The extraction method allows for the investigation of blade-vortex interactions independent of other sound sources. The method is based on filtering the spectral data calculated through the wavelet transform technique. The filter identifies blade-vortex interactions through their high amplitude, high frequency impulsive content. The filtered wavelet coefficients are then inverse transformed to create a pressure signature solely related to blade-vortex interactions. This extraction technique, along with a prescribed wake model, is applied to experimental data extracted from three separate flight maneuvers performed by a Bell 430 helicopter. The maneuvers investigated include a steady level flight, fast- and medium-speed advancing side roll maneuvers. A sensitivity analysis is performed in order to determine the optimal tuning parameters employed by the filtering technique. For the cases studied, the optimized tuning parameters were shown to be frequencies above 7 main rotor harmonics, and amplitudes stronger than 25% (−6 dB) of the energy in the main rotor harmonic. Further, it is shown that blade-vortex interactions can be accurately extracted so long as the blade-vortex interaction peak energy signal is greater or equal to the energy in the main rotor harmonic. An in-depth investigation of the changes in the blade-vortex interaction signal during transient advancing side roll maneuvers is then conducted. It is shown that the sound pressure level related to blade-vortex interactions, shifts from the advancing side, to the retreating side of the vehicle during roll entry. This shift is predicted adequately by the prescribed wake model. However, the prescribed wake model is shown to be inadequate for the prediction of blade-vortex interaction miss distance, as it does not respond to the roll rate of the vehicle. It is further shown that the sound pressure levels are positively linked to the roll rate of the vehicle. Similar sound pressure level directivities and amplitudes can be seen when vehicle roll rates are comparable. The extraction method is shown to perform admirably throughout each maneuver. One limitation with the technique is identified, and a proposal to mitigate its effects is made. The limitation occurs when the main rotor harmonic energy drops below an arbitrary threshold. When this happens, a decreased spectral amplitude is required for filtering; which leads to the extraction of high frequency noise unrelated to blade-vortex interactions. It is shown, however, that this occurs only when there are no blade-vortex interactions present. Further, the resulting sound pressure level is identifiable as it is significantly less than the peak blade-vortex interaction sound pressure level. Thus the effects of this limitation are shown to be negligible. / text

Computations were run to study heat transfer coefficient augmentation with film cooling for a simulated gas turbine blade leading edge. The realizable k-[epsilon] turbulence model (RKE) and Shear Stress Transport k-[omega] turbulence model (SST) were used for the computational simulations. RKE computations completed at a unity density ratio were confirmed to be consistent with experimental measurements conducted by Yuki et al.(1998) and Johnston et al. (1999) whereas SST computations exhibited significant discrepancies. Moreover the effect of the density ratio on heat transfer coefficient augmentation was studied because experimental measurements of heat transfer coefficient augmentation with film cooling are generally constrained to unity density ratio tests. It was shown that heat transfer coefficient augmentation can be simulated using unity density ratio jets, but only when scaled with the momentum flux ratio of the coolant jets. / text

In this thesis, a novel approach is presented for blade loss simulation of an aircraft gas turbine rotor mounted on rolling element bearings with squeeze film dampers, seal rub and enclosed in a flexible housing. The modal truncation augmentation (MTA) method provides an efficient tool for modeling this large order system with localized nonlinearities in the ball bearings. The gas turbine engine, which is composed of the power turbine and gas generator rotors, is modeled with 38 lumped masses. A nonlinear angular contact bearing model is employed, which has ball and race degrees of freedom and uses a modified Hertzian contact force between the races and balls and for the seal rub. This combines a dry contact force and viscous damping force. A flexible housing with seal rub is also included whose modal description is imported from ANSYS. Prediction of the maximum contact load and the corresponding stress on an elliptical contact area between the races and balls is made during the blade loss simulations. A finite-element based squeeze film damper (SFD), which determines the pressure profile of the oil film and calculates damper forces for any type of whirl orbit is utilized in the simulation. The new approach is shown to provide efficient and accurate predictions of whirl amplitudes, maximum contact load and stress in the bearings, transmissibility, thermal growths, maximum and minimum damper pressures and the amount of unbalanced force for incipient oil film cavitation. It requires about 4 times less computational time than the traditional approaches and has an error of less than 5 %.

This thesis project is about designing and developing an already existing testing device for a new invented Doctor Blade. A doctor blade is a blade used for creping tissue paper of a rotating cylinder, Yankee Cylinder. The old testing device was incomplete in a way that a rotating cylinder was missing, hence the tested blade is not loaded properly. The old testing device already contained the doctor blade holding device and the pulling device (pulling the creping blade). These two devices are transferred to the new testing device without any redesign within them. The adding of a rotating cylinder/roller required some new redesign regarding the testing device. The main beam (beam carrying all elements) is replaced with a larger one in order to fit the roller and is elongated in order to run longer tests. The new beam has a larger cross section in order to minimize the risk of bending. The main beam is supplied with five small beams, welded onto it, three for attaching the holding device and two for attaching the roller. The dimensions of these small beams are chosen in order to put the roller on the right position according to the creping blade. An electric motor is added to the new testing device in order to drive the roller with a chain. This required two sprockets, one for the motor and one for the roller shaft. The sprockets are chosen with a pitch diameter ratio matching the gearing required. FMEA-analysis is done on the whole design where five failure modes were chosen to be included, bending of the main beam and motor beam, screw joints of the same beams and sprocket-chain mechanism. Some FEM-analysis was required in order to detect the bending of the beams and measuring the loading on the screw joints. The screw joint loading achieved from the FEM-analysis is used for the theoretical screw joint calculations. The FMEA-analysis implied that four of the analyzed failure modes have acceptably low risk factor and dos not require any further actions. However one received a high risk factor, the chain-sprocket mechanism, the risk of clamping fingers. This is solved by adding a protecting house/shell made of sheet metal. Measurements were done on the old and the new testing device regarding the required force for pulling the creping blade and the pressure distribution between the creping blade and the beam (and roller in the new testing device). The improvement of the pulling force values is rather due to the new designed doctor blade than due to the new testing device. The new testing device is however more appropriate than the old one hence the added roller and the tests shows that it is functional as well. / Projektet handlar om design och utveckling av en redan existerande testrigg för ett nyuppfunnet kräppningsblad. Ett kräppningsblad är det bladet som just kräpper av papper från en roterande cylinder, s.k. Yankee Cylinder. Den gamla testriggen var inte komplett och saknade en roterande cylinder, därav kräppningsbladet belastades inte ordentligt. Den gamla testriggen innehöll redan en hållaranordning för kräppningsbladet och en dragstation (som drar kräppningsbladet). Dessa två delar förflyttades till den nya testriggen utan några korrigeringar. Tillägget av en roterande cylinder/vals krävde ny design för den nya testriggen. Huvudbalken (balken som bar alla delar) ersattes av en större balk för att den nya valsen ska få plats. Nya balken är även längre i syfte att kunna köra längre tester. Tvärsnittsarean hos den nya balken är större i syfte att minimera risken för böjning. Fem små balkar är fastsvetsade i den nya huvudbalken, tre för fästning av hållaranordningen och två för fästning av valsen. Placeringen av dessa fem balkar valdes i syfte att placera valsen i rätt position enligt kräppningsbladet. En elektrisk motor tillfördes till den nya testriggen i syfte att driva valsen med en kedja. Detta krävde två nya kugghjul, en för motorn och en för valsaxeln. Delningsdiametern för de två kugghjulen valdes med en viss kvot som motsvarar den utväxlingen som krävs. FMEA-analys utfördes på hela testriggen dör fem olika haveriorsaker inkluderades, böjning av huvudbalken och motorbalken, skruvförbanden på dessa två balkar och till sist kugghjul-kedja mekanismen. FEM-analys krävdes för beräkningar av böjningen på balkarne och för belastningen på skruvförbanden. Belastningen på skruvförbanden uppnåd från FEM-analysen användes senare i de teoretiska beräkningarna av skruvförbanden. FMEA-analysen angav att fyra av de fem analyserade haveriorsakerna har accepterad låg riskfaktor och kräver inga åtgärder. Dock så visade det sig att en haveriorsak fick en för hög risk faktor, kugghjul-kedja mekanismen, risken att klämma fingrar.Detta problem löstes med hjälp av att designa ett skyddshus /skal av plåt. Mätningar gjordes på den gamla och den nya testriggen på dragkrafter och tryckfördelning mellan kräppningsblad och balk (vals i den nya testriggen). Förbättringen av värden på dragkrafterna beror mer av det nydesignade kräppningsbladet än av den nya testriggen. Hursomhelst är den nya testriggen lämpligare än den gamla med tanke på tillförseln av valsen och dessutom så visar testerna att den är funktionell.

An accelerated high cycle fatigue testing approach is presented to determine the fatigue endurance limit of materials at high frequencies. Base excitation of a tapered plaque driven into a high frequency resonance mode allows the test to be completed in a significantly shorter time. This high cycle fatigue testing is performed using the tracked sine resonance search and dwell strategy. The controller monitors the structural health during the test. Any change in the dynamic response indicates crack initiation in the material. In addition, a shape optimization finite element model is conducted for the design of the tapered plaques. An integrated neural (Neural-Network) genetic (NSGA_II) optimization technique is implemented to carry out the shape optimization for this component. This process results in a significant reduction in the computational cost. A Pareto set is then produced that meets the designer’s requirements and provides the decision maker several alternatives to choose from.