bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigation of Turbine Stator Well Rim Seal, Re-Ingestion and Interstage Seal Flows Using Gas Concentration Techniques and Displacement Measurements
Authors: Eastwood D. , Coren D. D. , Long C. A. , Atkins N. R. , Childs P. R. N. , Scanlon T. J. , Guijarro-Valencia A.
Published: May 2012

Gas turbine engine performance requires effective and reliable internal cooling over the duty cycle of the engine. Life predictions for rotating components subject to the main gas path temperatures are vital. This demands increased precision in the specification of the internal air system flows which provide turbine stator well cooling and sealing. This in turn requires detailed knowledge of the flow rates through rim seals and interstage labyrinth seals. Knowledge of seal movement and clearances at operating temperatures is of great importance when prescribing these flows. A test facility has been developed at the University of Sussex, incorporating a two stage turbine rated at 400 kW with an individual stage pressure ratio of 1.7:1. The mechanical design of the test facility allows internal cooling geometry to be rapidly re-configured, while cooling flow rates of between 0.71 CW, ENT and 1.46 CW, ENT, may be set to allow ingress or egress dominated cavity flows. The main annulus and cavity conditions correspond to in cavity rotational Reynolds numbers of 1.71×106< Reφ <1.93×106. Displacement sensors have been used to establish hot running seal clearances over a range of stator well flow conditions, allowing realistic flow rates to be calculated. Additionally, gas seeding techniques have been developed, where stator well and main annulus flow interactions are evaluated by measuring changes in gas concentration. Experiments have been performed which allow rim seal and re-ingestion flows to be quantified. It will be shown that this work develops the measurement of stator well cooling flows and provides data suitable for the validation of improved thermo-mechanical and CFD codes, beneficial to the engine design process.
CFD Analysis of a Savonius Rotor in a Confined Test Section and in Open Field
Authors: Torresi Marco , Fortunato Bernardo , Pascazio Giuseppe , Camporeale Sergio Mario
Published: May 2012

Aim of this paper is to provide a deep insight into the dynamic behavior of the flow through a Savonius rotor by means of computational fluid dynamics (CFD). The analysis is carried out solving the incompressible Unsteady Reynolds Averaged Navier-Stokes equations, providing fundamental information concerning the complex unsteady flow field in and around the rotor. The motivation for employing a numerical approach relies on the consideration that detailed analysis of wind turbines, aiming to improve their design, cannot be easily performed by means of experimental full-scale field-testing due to the lack of control on the test conditions. At the same time, few are the wind tunnels where large turbine prototype testing is possible, so that experimental tests are usually carried out inside wind tunnels having dimensions comparable with those of the prototype. Moreover, if the available wind tunnel has a confined test section, the turbine performance could be quite different from those expected in open field. Therefore, in this paper, the turbine is firstly supposed to operate in open field and then in a bounded test section, in order to analyze the effect of flow confinement and to correlate the turbine performance in open field with experimental results obtained from prototypes tested in small wind tunnels of assigned blockage.
Measurement Based Atomization Model for Diesel Spray Evaporation and Combustion in a Matrix Burner
Authors: Bohn Dieter , Willie James
Published: May 2012

This paper describes the development of an atomization model for implementation in a CFD solver. The model is developed for application in a matrix burner that is suitable for simulating the conditions prevailing in stationary gas turbines. The fuel considered is diesel and the matrix burner is designed using the Lean Premixed Prevaporized (LPP) concept. In this concept, the liquid fuel is first atomized, vaporized and thoroughly premixed with the oxidizer before it enters the combustion chamber. The injector used is a hollow-cone Schlick series 121–123 pressure-swirl atomizer. Extensive measurements are carried out at different atomization pressures to determine the right parameters like the nozzle diameter, atomization pressure and spray cone angle that will yield a good spray pattern. Based on the measurement data, the mass flow rate and the droplet size distribution are determined. The latter is determined by curve fitting the experimental data. The determined droplet size distribution is implemented in a Fortran subroutine that is hooked to the CFD solver. Cold flow CFD results are compared for different positions of the nozzle. The hot flow CFD results are also compared with the hot flow results obtained when the droplet size distribution is assumed to be uniform.
Evaluation of Heat Transfer Effects on Turbocharger Performance
Authors: Sirakov Borislav , Casey Michael
Published: May 2012

Test data on several small turbochargers with different levels of heat transfer from the turbine to the compressor have been obtained through cooling of the turbocharger center housing and by testing in hot and cold test stands. This data identifies the strong effect of the heat transfer on the apparent efficiency of the compressor and turbine, particularly at low speeds and low mass flows. A simplified theory is used to explain the apparent effect of the heat transfer on the work input and efficiency. The results confirm that conventional performance maps underestimate the efficiency of the compressor stage and overestimate the efficiency of the turbine by as much as 20% points at low speeds. A correction procedure for this effect is defined which converts performance maps obtained with heat transfer to performance maps for adiabatic conditions (for both compressor and turbine) without any prior knowledge or measurement of the heat transfer. The practical significance of the results with regard to turbocharger performance and the relevance to a broader class of turbomachines is discussed.
Aerodynamic Performance of a Coolant Flow Off-Take Downstream of an OGV
Authors: A’Barrow C. , Carrotte J. F. , Walker A. D. , Rolt A. M.
Published: May 2012

Within the compression system of a gas turbine engine a significant amount of air is removed to fulfil various requirements associated with cooling, ventilation and sealing. Flow is usually removed through off-takes located in regions where space is restricted, whilst the flow is highly complex containing blade wakes, secondary flows and other flow features. This paper investigates the performance of a pitot style off-take aimed at providing a high pressure recovery in a relatively short length. For this to be achieved some pre-diffusion of the flow is required upstream of the off-take (i.e. by making the off-take larger than the captured streamtube). Although applicable to a variety of applications, the system is targeted at an intercooled aero-engine concept where the off-take would be located aft of the fan Outlet Guide Vane (OGV) root and provide coolant flow to the heat exchangers. Measurements and numerical predictions are initially presented for a baseline configuration with no off-take present. This enabled the OGV near field region to be characterised and provided a datum, relative to which the effects of introducing an off-take could be assessed. With the off-take present a variety of configurations were investigated including different levels of pre-diffusion, prior to the off-take, and different off-take positions. For very compact systems of short length, such that the gap between the OGV and off-take is relatively small, the amount of pre-diffusion achievable is limited by the off-take pressure field and its impact on the upstream OGV row. This pressure field is also influenced by parameters such as the non-dimensional off-take height and splitter thickness. The paper analyses the relative importance of these various effects in order to provide some preliminary design rules. For systems of increased length a significant amount of flow pre-diffusion can be achieved with little performance penalty. However, the pre-diffusion level is eventually limited by the increased distortion and pressure losses associated with the captured streamtube.
Experimental Validation of Empirical Methods for Dynamic Stress Prediction in Turbomachinery Blades
Authors: Allison Timothy C. , Lerche Andrew H. , Moore J. Jeffrey
Published: May 2012

Turbomachinery blade fatigue life estimation requires reliable knowledge of actual static and dynamic stresses occurring within the blades. A common method for predicting dynamic stresses is to construct a finite element model of the blade and simulate the dynamic response to aerodynamic loads. Although this method is powerful and very useful, modeling errors (geometry, boundary conditions, stress concentrations, damping, etc.) may result in inaccurate stress predictions. Furthermore, unavoidable variability in manufacturing results in blade mistuning, which significantly affects stress amplification at resonance. This paper presents two empirical methods for predicting dynamic stresses in turbomachinery blades that include the actual effects of structural damping and mistuning. Both methods use strain gauge measurements from a blade modal test to obtain load to strain transfer functions, which are applied to predict the blade strain or stress response to a simulated load. The advantages and disadvantages of each method are discussed. The predictions of each method are compared with dynamic blade strain data acquired during a rotating test of a centrifugal compressor impeller.
Integrating a Hybrid Electric Drive Propulsion System With the Existing DDG 51 Class Machinery Control System
Authors: Halpin Richard , Sapienza Frank
Published: May 2012

The destroyers of the USS Arleigh Burke Class all have 4 propulsion gas turbines and 3 gas turbine generators (GTGs). A typical at-sea “condition 3” operating profile consists of having 2 gas turbine generators running at approximately 50% capacity, and one propulsion gas turbine online at low to intermediate ship speeds. Having 2 GTGs online at all times at 50% load each provides the obvious advantage of maintaining all electric loads should one GTG shut down unexpectedly. This luxury does come at the cost of fuel efficiency, as gas turbines efficiency improves continuously as they move away from idle. On the propulsion end, a single gas turbine is capable of generating enough horsepower to propel the ship at speeds in excess of 20 knots. Depending upon the specific mission that the destroyer may be on, however, quite a bit of operating profile may be at speeds below 15 knots where the LM2500 is operating at less than 20% capacity. In this range of operation specific fuel consumption ratios are also relatively low. The proposed Hybrid Electric Drive (HED) system has the potential to address both of these inefficient ranges of operation. By installing one 2000 horsepower electric motor on each shaft, the electric motors can be used to propel the ship at speeds below 14 knots (projected) while running the GTGs up to 90% operating range where they are most efficient. The LM2500 is shut down completely at this range, and the potential fuel savings in this configuration is substantial. While there are many engineering challenges with installing such a HED system on board an in-service DDG, the focus of this paper is on how to integrate HED with the existing Machinery Control System (MCS). Such challenges include interfacing MCS to the HED supervisory controller, developing a new HED control interface for the propulsion control operator, integrating HED into the existing shaft speed control algorithm, transitioning to and from HED propulsion, and updating data logging to include HED. Managing the interface between current electric load, changing electric loads, and current available HED power will also be addressed.
Aero-Structural Analysis of Wind Turbine Blades With Sweep and Winglets: Coupling a Vortex Line Method to ADAMS/AeroDyn
Authors: Braaten Mark E. , Gopinath Arathi
Published: May 2012

The FAST/ADAMS/AeroDyn system of codes has been widely used to perform the aero-structural analysis of conventional wind turbine blades. Recent advances in blade design involve the development of aeroelastic tailored blades with large amounts of sweep, and blades with winglets. However, the existing Blade Element Momentum (BEM) approach in AeroDyn is limited to straight blades and does not account for sweep or dihedral effects. The goal of this work is to obtain higher fidelity aerodynamic loads predictions for such advanced blade designs. A Vortex Line Method (VLM) for computing aerodynamic loads has been coupled to ADAMS through modification of the existing AeroDyn interface. The VLM approach adopted here adds fidelity by modeling the effects of sweep, dihedral, 3D wakes, and wake dynamics. An existing steady/unsteady VLM code with these capabilities was restructured to allow its integration with AeroDyn. The FAST routines from NREL, which are used as a preprocessor to ADAMS, and the ADAMS/AeroDyn interface itself, were also modified to create an ADAMS model that properly accounts for the curvature of the blade that occurs when large amounts of sweep or winglets are present. The resulting ADAMS/VLM model was compared to the original ADAMS/BEM model for a straight blade and for a highly swept blade. The model was also applied to blades with pressure-side and suction-side winglet configurations. The BEM and VLM models give similar aero predictions for the straight blade, as expected. The induced twist and blade deformations are found to be more similar for the two methods than the aerodynamic loads. Computations were made for the blades with the winglets at different wind speeds and different pitch settings, and results were obtained for blade deflection, induced twist, and thrust and torque force distributions.
Analysis of Flow Migration in an Ultra-Compact Combustor
Authors: Bohan Brian T. , Polanka Marc D.
Published: May 2012

The Ultra Compact Combustor (UCC) has the potential to offer improved thrust-to-weight and overall efficiency in a turbojet engine. The thrust-to-weight improvement is due to a reduction in engine weight by shortening the combustor section through the use of the revolutionary UCC design. The improved efficiency is achieved by using an increased fuel-to-air mass ratio, and allowing the fuel to fully combust prior to exiting the UCC system. Furthermore, g-loaded combustion offers increased flame speeds that can lead to smaller combustion volumes. The circumferential combustion of the fuel in the UCC cavity results in hot gases present at the outside diameter of the core flow. This orientation creates an issue in that the flow from the circumferential cavity needs to migrate radially and blend with the core flow to present a uniform temperature distribution to the high-pressure turbine rotor. A computational fluid dynamics (CFD) analysis is presented for the flow patterns in the combustor section of a representative fighter-scale engine. The analysis included a study of secondary flows, cavity flow characteristics, shear layer interactions and mixing properties. An initial understanding of primary factors that impact the radial migration is presented. Computational comparisons were also made between an engine realistic condition and an ambient pressure rig environment.
Test Results From a Concentrated Solar Microturbine Brayton Cycle Integration
Authors: Dickey Brian
Published: May 2012

Capstone Microturbine and Heliofocus Solar Thermal Solutions in a partnership built an open loop Brayton cycle system using a 65 kW Capstone Microturbine and a concentrated solar energy receiver. This system was built for initial development testing to validate the ability to generate electricity on a small scale at high efficiencies using only solar energy as the input. A secondary goal was to demonstrate the ability of the receiver to transfer sun energy into the working fluid of air at efficiencies that would support the target overall system electrical efficiency of 21%. Concentrating Solar Power systems in the 20 kW to 100 kW electrical output power range currently do not exist in the market place today. Demand for this type of power generation is high due to its small footprint per kW of energy produced, its ability to be distributed in small kW increments to meet site demand and space, its relatively high electrical efficiency and its projected low cost per kilowatt of generated electricity. This initial testing was done without the production configuration dish concentrator component and instead a solar tower with a field of Heliostats provided the sunlight to the solar generation system. Test results showed that the receiver met the efficiency goal set forth and that the overall system was capable of producing 25kW of electricity to the electric grid. The receiver efficiency measured was 89% at or near the needed airflow and air temperature levels required by the Microturbine to support an overall system efficiency of 21%. The next step in the development process would be to integrate the development system onto a concentrating solar dish and demonstrate the total conversion efficiency at the target 21% prior to commercialization.
Development and Field Validation of a Large-Frame Gas Turbine Power Train for Steel Mill Gases
Authors: Hall Joel M. , Thatcher Robert T. , Koshevets Sergey V. , Thomas Larry L. , Jones Robert M.
Published: May 2012

As of September 2009, GE Energy (GE) has successfully expanded its large-frame gas turbine product line to burn ultra-low calorific steel mill gas fuel blends, especially mixtures of Blast Furnace Gas (BFG) and Coke Oven Gas (COG). The first two GE frame 9E Gas Turbines in China with this capability have thus far accumulated more than 8000 hours operating on BFG/COG blends. The China site comprises two complete power trains, including GE 9E gas turbines, generators, fuel cleaning equipment, and fuel gas compressors. Since startup, combustion operating parameters have remained within design limits, consistent with the extensive full-scale lab testing GE conducted during the turbine’s design development effort, and comparable to fleet experience on natural gas fired GE gas turbines. Based on this accumulated data set, especially the wide range of gas compositions tested in the combustion lab, similar process gases such as corex and finex gases, and air-blown synthetic gases are operable in this system. The GE 9E platform targets the 50Hz market. For 60Hz applications, a 7EA BFG product is available.
Endwall Contouring Using Continuous Diffusion: A Breakthrough Method and its Application to a Three-Stage High Pressure Turbine
Authors: Schobeiri M. T. , Lu K.
Published: May 2012

Blades of high pressure turbines have a relatively small aspect ratio that produce major secondary flow regions close to the hub and tip. The secondary flows caused by a system of hub and tip vortices induce drag forces resulting in an increase of secondary flow losses and thus a reduction of stage efficiency. Given the high level of technological maturity and the current state of turbine aerodynamic efficiency, major efficiency improvement, if any, can be achieved only by significant R&D effort. In contrast, moderate increase in aerodynamic efficiency is attainable by reducing the effect of parasitic vortices such as those mentioned above. Introducing an appropriate non-axisymmetric endwall contouring reduces the secondary flow effect caused by the pressure difference between pressure and suction surfaces. Likewise, attaching leading edge fillets reduces the strength of horse shoe vortices. While an appropriate endwall contouring design requires special care, the design of the leading edge fillet is straight forward. In this paper we present a physics based method which enables researchers and engineers to design endwall contours for any arbitrary blade type regardless of the blade loading, degree of reaction, stage load and flow coefficients. A thorough step-by-step design instruction is followed by its application to the second rotor of the three-stage research turbine of Turbomchinery Performance and Flow Research Laboratory (TPFL) of Texas A&M University. Comprehensive numerical calculations of the flow field including the secondary flow show the positive impact of an appropriately designed endwall contouring on the efficiency. The results also show, how an inappropriately designed contour can be detrimental to turbine efficiency. The numerical result of the efficiency calculations is compared with the experimentally obtained efficiency for the reference non-contoured turbine.
Comprehensive Application of a First Principles Based Methodology for Design of Axial Compressor Configurations
Authors: Iyengar Vishwas , Sankar Lakshmi N.
Published: May 2012

Axial compressors are widely used in many aerodynamic applications. The design of an axial compressor configuration presents many challenges. It is necessary to retool the design methodologies to take advantage of the improved accuracy and physical fidelity of these advanced methods. Here, a first-principles based multi-objective technique for designing single stage compressors is described. The study accounts for stage aerodynamic characteristics and rotor-stator interactions. The proposed methodology provides a way to systematically screen through the plethora of design variables. This method has been applied to a rotor-stator stage similar to NASA Stage 35. By selecting the most influential design parameters and by optimizing the blade leading edge and trailing edge mean camber line angles, phenomena such as tip blockages, blade-to-blade shock structures and other loss mechanisms can be weakened or alleviated. It is found that these changes to the configuration can have a beneficial effect on total pressure ratio and stage adiabatic efficiency, thereby improving the performance of the axial compression system.
Combined Cycle Off-Design Performance Estimation: A Second-Law Perspective
Authors: Gu¨len S. Can , John Joseph
Published: May 2012

A combined cycle power plant (or any power plant, for that matter) does very rarely — if ever — run at the exact design point ambient and loading conditions. Depending on the demand for electricity, market conditions and other considerations of interest to the owner of the plant and the existing ambient conditions, a CC plant will run under boundary conditions that are significantly different from those for which individual components are designed. Accurate calculation of the “off-design” performance of the overall combined cycle system and its key subsystems requires highly detailed and complicated computer models. Such models are crucial to high-fidelity simulation of myriad off-design performance scenarios for control system development to ensure safe and reliable operability in the field. A viable option in lieu of sophisticated system simulation is making use of the normalized curves that are generated from rigorous model runs and applying the factors read from such curves to a known design performance to calculate the “off-design” performance. This is the common method adopted in the fulfillment of commercial transactions. These curves, however, are highly system-specific and their broad applicability to a wide variety of configurations is limited. Utilizing the key principles of the second law of thermodynamics, this paper describes a simple, physics-based calculation method to estimate the off-design performance of a combined cycle power plant. The method is shown to be quite robust within a wide range of operating regimes for a generic combined cycle system. As such, a second law based approach to off-design performance estimation is a highly viable tool for plant engineers and operators in cases where calculation speed with a small sacrifice in fidelity is of prime importance.
Model-Based Data Reconciliation and Bias Detection for Heavy-Duty Industrial Gas Turbines Performance Diagnosis
Authors: Lin TsungPo , Mendoza Eduardo , Kestner Brian K.
Published: May 2012

Performance diagnoses of heavy-duty industrial gas turbines often rely on measured data from on-site monitoring systems (OSM), subjected to larger uncertainties and possible biases. The measured data are used to analyze gas turbine heat balance and estimate immeasurable performance characteristics such as firing temperature and component health parameters. Traditional heat balance techniques are deterministic, and, thus, calibration uncertainty is not mitigated. In this paper, a method of model-based data reconciliation (MBDR) and bias detection was developed, serving as a probabilistic process of reducing calibration uncertainty while eliminating contamination effects caused by measurement biases. This method utilizes physics-based gas turbine models to reconcile multiple data sets while the model health parameters are inferred simultaneously. Levenberg–Marquardt algorithm was utilized to solve the maximum-likelihood problem, i.e., minimizing Least Squares. A hypothesis test scheme using sequential bias compensation was utilized for bias detection and neutralizing smearing effects. To reduce the computation time in MBDR and bias detection, the Response Surface Methodology (RSM) was applied to generate surrogate model. A systematic way of data selection using Multiscale Principal Component Analysis was also employed, serving as an efficient way of filtering large data sets for the use of MBDR. This proposed methodology was demonstrated by application to GE 7FA gas turbines. Results showed significant reduction in calibration uncertainty and smearing effects.
Validation of a Coupled Fluid/Solid Heat Transfer Method
Authors: Chaquet Jose M. , Corral Roque , Pastor Guillermo , Pueblas Jesus , Coren D. D.
Published: May 2012

A coupled method for solid/fluid steady heat transfer calculations is presented. The results of the fully coupled and uncoupled simulations are compared with the experimental data obtained for the front and rear stator well of a turbine. Several cooling mass flow rates have been considered. The uncoupled methodology is described as well and the accuracy of the results for both approaches is discussed. It is concluded that even if the uncoupled approach it is conducted carefully, the coupled method is more accurate since it removes some hypotheses inherent to the uncoupled approach.
Lean Blowout Predictions of a Non-Premixed V-Gutter Stabilized Flame Using a Damkohler Number Methodology
Authors: Wang Hui-ru , Jin Jie
Published: May 2012

The lean blowout stability of a non-premixed, V-gutter stabilized flame was investigated using a Damkohler number methodology. The flow and chemical timescales were extracted from the reacting RANS CFD results on a cell-by-cell basis. Assessment of three representative definitions of flow and chemical timescales for Damkohler number based on different blowout mechanisms was performed. By examining the Damkohler number fields, the structure of the flame or the possibility of blowout can be estimated. The results demonstrated that a distinct transition between stable and unstable flames was observed by decreasing the fuel-air ratio or increasing the inlet velocity at atmosphere pressure and an inlet temperature of 537K. All three definitions can predict the lean blowout limit in a reasonable consistent with the available experimental data through adjusting the critical Damkohler number of each definition in the current study. The performances and physical differences of three definitions were also discussed.
Thermal Analysis of Cooling System in a Gas Turbine Transition Piece
Authors: Park Jun Su , Yun Namgeon , Moon Hokyu , Kim Kyung Min , Kang Sin-Ho , Cho Hyung Hee
Published: May 2012

This paper presents thermal analyses of the cooling system of a transition piece, which is one of the primary hot components in a gas turbine engine. The thermal analyses include heat transfer distributions induced by heat and fluid flow, temperature, and thermal stresses. The purpose of this study is to provide basic thermal and structural information on transition piece, to facilitate their maintenance and repair. The study is carried out primarily by numerical methods, using the commercial software, Fluent and ANSYS. First, the combustion field in a combustion liner with nine fuel nozzles is analyzed to determine the inlet conditions of a transition piece. Using the results of this analysis, pressure distributions inside a transition piece are calculated. The outside of the transition piece in a dump diffuser system is also analyzed. Information on the pressure differences is then used to obtain data on cooling channel flow (one of the methods for cooling a transition piece). The cooling channels have exit holes that function as film-cooling holes. Thermal and flow analyses are carried out on the inside of a film-cooled transition piece. The results are used to investigate the adjacent temperatures and wall heat transfer coefficients inside the transition piece. Overall temperature and thermal stress distributions of the transition piece are obtained. These results will provide a direction to improve thermal design of transition piece.
Numerical Study on Varied Vortex Reducer Configurations for the Flow Path Optimization in Compressor Cavities
Authors: Du Xiao-qin , Zhu Hui-ren , Zhang Zong-wei
Published: May 2012

In the internal air system of modern aero-engine, the cooling air is generally taken from the compressor platform, transported radially inwards towards the shaft and further transported to the hot parts. Since strongly swirling air is bled in the compressor rotor to a much lower radius, a means of vortices will be created, which lead to very high pressure losses and limit the cooling flow rate. The present work investigates the fluid flow for twelve kinds of vortex reducer geometries which utilize columnar baffles to divide the cavity into several chambers and avoid extensive vortex formation, therefore the pressure loss decreases and the flow mass increases observably. Based on the numerical study, the pressure loss is closely related to the curvature of the curve and the intersection angle (β) at the entry. Geometries of columnar baffles installed in the cavity include the straight angled degrees (0°,45°,60°) towards the radial and the curved such as Archimedean spirals (ρ = aθ, a = 12,20,30), hyperbolic spirals (ρ θ = a, a = 50,80,100) and logarithmic spirals (ρ = eα θ, α = 0.3,0.4,0.5). For the straight, the attention is focused on six and twelve baffles which are evenly arranged along the circumferential, but six ones for the curved. Otherwise, a key point is that the total volume of baffles is equal for different vortex reducer geometries. The results show that vortex reducer configurations with twelve baffles perform better than those with six baffles for the straight with the same angle. Compared with the straight radial baffle, the other kinds of baffles play better roles with respect to reducing pressure losses and gaining large flow mass. As a rule, the large pressure loss occurs when the curvature for the curved is large, because the flow direction changes greatly. A dedicated investigation about the influence of varied vortex reducer configurations is presented in this paper, particular discussions and conclusions are shown.
Non-Linear Dynamics of Multi-Mode Unstable Bladed-Disks: Part I—Description of a Canonical Model and Phenomenological Results
Authors: Corral Roque , Gallardo Juan Manuel
Published: May 2012

A simple model that describes the non-linear dynamics of bladed-disk due to the dry friction exerted in attachment and the unsteady aerodynamic forced induced by the vibration of aerodynamically unstable airfoils is presented and analyzed. The analysis is focused on a simplified case whose dynamics is representative of a high aspect ratio low-pressure turbine rotor-blade. A parametric study is conducted to understand the dynamics of the the problem for times much longer than the fundamental period of the rotor blades, when the effect of the initial conditions is not relevant and a periodic steady state has been reached. It is concluded that the conjecture that the dynamics of multi-mode unstable bladed-disk, in the absence of external periodic forcing, finally reaches a state in which only a single traveling-wave exists is true and that this behavior may be reproduced using simplified models.
Design of a Highly Loaded Transonic Two-Stage Fan Using Swept and Bowed Blading
Authors: Jin Hailiang , Jin Donghai , Zhu Fang , Wan Ke , Gui Xingmin
Published: May 2012

This paper presents the design of a highly loaded transonic two-stage fan using several advanced three-dimensional blading techniques including forward sweep and “hub bending” in rotors and several bowed configurations in stators. The effects of these blading techniques on the performance of the highly loaded transonic two-stage fan were investigated on the basis of three-dimensional Navier-Stokes predictions. The results indicate that forward sweep has insignificant impact on the total pressure ratio and adiabatic efficiency of the fan. The throttling range of the fan is found to be improved by forward sweep because the shock in the forward swept rotor is expelled later upstream to the leading edge than that in the unswept one. Hub bending design technique increases the efficiency in the hub region of R1 due to the reduction of the low momentum zone in the hub region near the trailing edge. The stator vane design has a pronounced impact on the performance of the fan. The total pressure ratio, adiabatic efficiency, and stall margin of the schemes with the bowed vanes are increased significantly compared to the scheme with the straight vanes. The large corner stall in the straight S1 vane is reduced effectively by the bowed S1 vanes. Moreover, the strong corner stall in the straight S2 vane is fully eliminated by the bowed S2 vanes. Among the bowed vane schemes, the scheme with positive bowed (P. B.) hub and negative bowed (N. B.) tip vanes has the best efficiency and stall margin performances thanks to the superiority of the performance over the midspan regions of the bowed vanes.
Concept Optimal Design of Composite Fan Blades
Authors: Rao J. S. , Sheelavant Kiran , Bombale Balasaheb
Published: May 2012

A procedure is outlined to determine the composite lay-out of a given baseline metallic fan blades. The vane material Titanium is replaced by Carbon Fiber composite materials. For the operating speed the baseline maximum strain in the vane is maintained and weight reduction is taken as the objective function. Three phases of optimization are suggested. In the first phase free size optimization is performed on the composite blades to determine the required topology. A layout of composites is then proposed. In the second phase based on free optimization results gauge optimization setup is illustrated for determining the thicknesses. In the third phase Ply-stacking optimization can be performed. By using composite materials substantial savings in the weight can be achieved without affecting the performance of engine blade.
Experimental Investigation of Turbocharger Rotor Bearing System
Authors: Ashtekar Ankur , Sadeghi Farshid , Powers Garry , Mantel Kevin , Griffith Robert
Published: May 2012

The objectives of this investigation were to design and construct a high speed turbocharger test rig to measure dynamics response of angular contact ball bearing rotor system, and to evaluate the performance of angular contact ball bearings as a replacement to conventional journal bearings in turbocharger systems. A test rig was designed and developed to operate at speeds up to 70,000 rpm. The rotating components (i.e. turbine wheels) of the turbocharger test rig were made to be dynamically similar to an actual turbocharger. Proximity sensors were used to record the turbine wheel displacements while accelerometers were used to monitor the rotor vibrations. A radio telemetry based wireless temperature sensor was designed and installed on the bearing cage. The in-situ temperature sensor monitored and recorded the bearing condition in real time. The rotor dynamic results obtained from the turbocharger test rig were used to corroborate with an analytical model developed simulate the turbocharger rotor system. The turbocharger test rig was then used to examine the dynamic response of the turbocharger. The rotor displacements and bearing temperatures were recorded and analyzed to study the effects of bearing preloading and rotor imbalance on the turbocharger ball bearing rotor system.
Experimental/Numerical Crossover Jet Impingement in an Airfoil Leading-Edge Cooling Channel
Authors: Elebiary K. , Taslim M. E.
Published: May 2012

Technological advancement in gas turbine field demands high temperature gases impacting on the turbine airfoils in order to increase the output power as well as the thermal efficiency. Leading-edge is one of the most critical and life-limiting sections of the airfoil which requires intricate cooling schemes to maintain a robust design. In order to maintain coherence with a typical external aerodynamic blade profile, cooling processes usually take place in geometrically complex internal paths where analytical approaches may not provide a proper solution. In this study, experimental and numerical models simulating the leading-edge and its adjacent cavity were created. Cooling flow entered the leading-edge cavity through the crossover ports on the partition wall between the two cavities and impinged on the internal surface of the leading edge. Three flow arrangements were tested: 1,2) flow entering from one side (root or tip) of the adjacent cavity and emerging from either the same side or the opposite side of the leading-edge cavity and 3) flow entering from one side of the adjacent cavity and emerging from both sides of the leading-edge cavity. These flow arrangements were tested for five crossover-hole settings with a focus on studying the heat transfer rate dependency on the axial flow produced by upstream crossover holes (spent air). Numerical results were obtained from a three-dimensional unstructured computational fluid dynamics model with 1.1 million hexahedral elements. For turbulence modeling, the realizable k–ε was employed in combination with enhanced wall treatment approach for the near wall regions. Other available RANS turbulence models with similar computational cost did not produce any results in better agreement with the measured data. Nusselt numbers on the nose area and the pressure/suction sides are reported for jet Reynolds numbers ranging from 8000 to 55000 and a constant crossover hole to the leading-edge nose distance ratio, Z/Dh, of 2.81. Comparisons with experimental results were made in order to validate the employed turbulence model and the numerically-obtained results. Results show a significant dependency of Nusselt number on the axial flow introduced by upstream jets as it drastically diminishes the impingement effects on the leading-edge channel walls. Flow arrangement has immense effects on the heat transfer results. Discrepancies between the experimental and numerical results averaged between +0.3% and −24.5%, however correlation between the two can be clearly observed.
Electronic Torsional Vibration Elimination for Synchronous Motor Driven Turbomachinery
Authors: Sihler Christof , Schramm Simon , Rossi Valerio , Lenzi Andrea , Depau Valerio
Published: May 2012

The oil and gas industry has a growing demand for electrically driven trains operated at variable speeds. Variable frequency electrical drives enable increased operational flexibility and energy efficiency. One drawback of power electronics driven systems is the generation of non-fundamental air-gap torque ripple components due to electrical harmonics. The air-gap torque ripple can interact with the mechanical system at natural torsional frequencies of the drive train. Uncontrolled excited torsional vibration can silently lead to coupling failure due to fatigue. The coincidence of electrical drive harmonics and natural torsional frequencies of the mechanical system is sometimes unavoidable, due to the large variable speed range of the compressor as for process requirements. For those types of applications, a damping system utilizing available power electronics has been developed that can be applied to new units but also as a retrofit solution in existing variable speed trains. Electronic torsional vibration elimination (eTVe) is based on an angular vibration measurement in the mechanical system and an interface to the existing inverter control of the electrical drive. An important milestone of the eTVe development was achieved in 2010, in site testing this new solution to Liquid Natural Gas (LNG) production trains and demonstrating that it can completely eliminate torsional vibrations. With eTVe a residual torsional vibration level was achieved that was lower than the vibration level measured while the LNG train was only gas turbine driven. This torsional performance was achieved with a standard load commutated inverter drive (LCI). LCIs are one of the most widespread electrical drive technology for gas compression trains because of excellent reliability records, and it is the only one referenced solution for electric power larger than 45 MW.
Development of an Air-Cycle Environmental Control System for Automotive Applications
Authors: Forster Christopher J. , Lemieux Patrick
Published: May 2012

The Reverse-Brayton cycle has been used for aircraft cabin cooling for many decades. However, air-cycle cooling hasn’t been popular in the automotive field yet. This study demonstrates that air-cycle technology can provide sufficient cooling for certain applications. The primary focus is a novel forced induction engine control system, where compressor bleed is used both to provide engine boost control and air-conditioning. The bleed-air drives an air-cycle machine (ACM) consisting of typical automotive components: a turbocharger, heat exchanger, and ducting. The components of an ACM system are lightweight and compact compared to those of a typical vapor compression system; both qualities are critical in high performance applications, where such a system seems to make most sense. The ACM was tested first on a test stand and then directly on an engine, in a bootstrap-cycle configuration. The turbocharged test engine’s intake manifold pressure was controlled by bleeding air from the outlet of the engine’s intercooler and feeding the ACM compressor inlet. Once the compressed air was supplied to the ACM it was further compressed by the ACM, cooled by the secondary intercooler, and expanded through the ACM turbine. The engine’s turbocharger was resized to compensate for the increased air flow during ACM operation. The results show that a dry-air-rated (DAR) coefficient of performance (COP) of 0.73 and a DAR cooling capacity of 1.5 tons are possible on a test stand, and a DAR COP of 0.56 and a DAR cooling capacity of 0.72 tons are possible on-engine. The data available from the on-engine testing was limited to lower ACM pressure ratios due to a bearing failure before full testing was complete; performance would likely increase with higher inlet pressures, as shown by the compressed air test stand results. The test results strongly suggest that continued development and in-vehicle testing will provide adequate air-conditioning and engine performance, using only the most benign and environmentally friendly working fluid: air.
An Investigation of Treating Adiabatic Wall Temperature as the Driving Temperature in Film Cooling Studies
Authors: Zhao Lei , Wang Ting
Published: May 2012

In film cooling heat transfer analysis, one of the core concepts is to deem film cooled adiabatic wall temperature (Taw) as the driving potential for the actual heat flux over the film-cooled surface. Theoretically, the concept of treating Taw as the driving temperature potential is drawn from compressible flow theory when viscous dissipation becomes the heat source near the wall and creates higher wall temperature than in the flowing gas. But in conditions where viscous dissipation is negligible, which is common in experiments under laboratory conditions, the heat source is not from near the wall but from the main hot gas stream; therefore, the concept of treating the adiabatic wall temperature as the driving potential is subjected to examination. To help investigate the role that Taw plays, a series of computational simulations are conducted under typical film cooling conditions over a conjugate wall with internal flow cooling. The result and analysis support the validity of this concept to be used in the film cooling by showing that Taw is indeed the driving temperature potential on the hypothetical zero wall thickness condition, ie. Taw is always higher than Tw with underneath (or internal) cooling and the adiabatic film heat transfer coefficient (haf) is always positive. However, in the conjugate wall cases, Taw is not always higher than wall temperature (Tw), and therefore, Taw does not always play the role as the driving potential. Reversed heat transfer through the airfoil wall from downstream to upstream is possible, and this reversed heat flow will make Tw > Taw in the near injection hole region. Yet evidence supports that Taw can be used to correctly predict the heat flux direction and always result in a positive adiabatic heat transfer coefficient (haf). The results further suggest that two different test walls are recommended for conducting film cooling experiments: a low thermal conductivity material should be used for obtaining accurate Taw and a relative high thermal conductivity material be used for conjugate cooling experiment. Insulating a high-conductivity wall will result in Taw distribution that will not provide correct heat flux or haf values near the injection hole.
Flow and Heat Transfer in the Tip-Turn Region of a U-Duct Under Rotating and Non-Rotating Conditions
Authors: Hu S.-Y. , Chi X. , Shih T. I.-P. , Bryden K. M. , Chyu M. K. , Ames R. , Dennis R. A.
Published: May 2012

CFD simulations were performed to study the flow and heat transfer in a U-duct, relevant to internal cooling of the first-stage turbine component in electric-power-generation, gas-turbine engines. Parameters studied include (1) two aspect ratios of the duct cross section, i.e. H/W = 1 and H/W = 0.25; (2) smooth duct and duct lined with pin fins of height H arranged in a staggered fashion; and (3) two rotational speeds: 0 rpm and 3,600 rpm. In all cases, the wall temperature is 1173 K; the coolant temperature at the U-duct inlet is 623 K; and the back pressure at the exit of the U-duct is 25.17 atm. The Reynolds numbers studied are 150,000 for the duct with the 4-to-1 aspect ratio, and 150,000 and 375,000 for the duct with the 1-to-1 aspect ratio. When there is rotation at 3,600 rpm, the rotational numbers corresponding to these Reynolds numbers and duct aspect ratios are 0.592, 1.64, and 4.11, respectively. Result is presented to show the nature of the flow, the temperature distribution, and the surface heat transfer with focus on the flow and heat transfer in the tip-turn region as a function of the parameters investigated. This computational study is based on 3-D steady RANS. The ensemble-averaged continuity, compressible Navier-Stokes, and energy equations were closed by the thermally perfect equation of state with temperature-dependent gas properties and the two-equation realizeable k-ε turbulence model with and without wall functions.