bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Regular and Random Roughness on the Heat Transfer and Skin Friction Coefficient on the Suction Side of a Gas Turbine Vane
Authors: Dees Jason E. , Bogard David G.
Published: March 2009

Skin friction coefficients and heat transfer coefficients are measured for a range of regular and random roughnesses on the suction side of a simulated gas turbine vane. The skin friction coefficients are calculated using boundary layer data and the momentum integral method. High resolution surface temperature data measured with an IR camera yields local heat transfer values. 80 grit, 50 grit, 36 grit, and 20 grit sandpaper, along with a regular array of conical roughness elements are tested. Measured skin friction coefficient data shows that the conical roughness array behaves very similarly to the 50 grit, 36 grit, and 20 grit sandpapers in terms of the effect of the roughness on the hydrodynamic boundary layer. In terms of heat transfer, the conical roughness array is most similar to the 80 grit sandpaper, which are both lower than the roughest sandpapers tested. This data shows that the particular regular array of roughness elements tested has fundamentally different behavior than randomly rough surfaces for this position on the simulated turbine vane. In addition, this difference is in the opposite direction as seen in previous experimental studies. In order to draw a more general conclusion about the nature of random and regular roughness, a parametric study of regular roughness arrays should be performed.
Thermal-Hydraulic Characteristics of Microchannel Heat Exchanger and Its Application to Solar Gas Turbines
Authors: Utamura Motoaki
Published: March 2009

Incorporating “integral method” proposed here, a set of empirical correlations of local heat transfer coefficient and pressure loss coefficient are newly derived based on experiments using microchannel heat exchanger (MCHE) with supercritical carbon dioxide as heating medium and water as coolant. They are expressed in dimensionless forms of polynomial of Reynolds number and Prandtl number. The same correlation of Nusselt number is found applicable to both fluids and its value is almost two times larger than Dittus Boelter correlation. It was also shown that the above form is applicable to a wide range of geometry with the values of constants changed. Accuracy of both correlations is confirmed within 5% errors for MCHE with S-shaped fins in the range of pressures 9∼12.5MPa and temperatures 280∼390K. Based on the correlations, sizes of heat exchangers are evaluated contained in gas turbine cycle with super critical carbon dioxide as a working fluid applicable to solar power.
Influence of Blowing Ratio on the Double-Jet Ejection of Cooling Air
Authors: Kusterer Karsten , Bohn Dieter , Sugimoto Takao , Tanaka Ryozo
Published: March 2009

Further improvement of the thermal efficiency of modern gas turbines can be achieved by a further reduction of the cooling air amount. Therefore, it is necessary to increase the cooling effectiveness so that the available cooling air fulfils the cooling task even if the amount has been reduced. In particular, the cooling effort for the vanes and blades of the first stage in a modern gas turbine is very high. The task of the film-cooling is to protect the blade material from the hot gas attack to the surface. Unfortunately, aerodynamic mixing processes are enhanced by secondary vortices in the cooling jets and, thus, the film-cooling effectiveness is reduced shortly behind the cooling air ejection through the holes. By improvement of the hole positioning, the negative interaction effects can be reduced. One approach is the Double-jet Film-cooling (DJFC) Technology presented recently by the authors. It has been shown by numerical simulations that for a special and precise arrangement of two holes, the interaction of the secondary vortices can be used for a significant increase in film-cooling effectiveness. This is reached by establishing an anti-kidney vortex pair in a combined jet from two jets starting from two cylindrical ejection holes. The influence of the blowing ratio on the double-jet ejection is investigated numerically. The configurations of the double-hole arrangements have been investigated only for a relative high blowing ratio (M = 1.7). The present investigations focus on moderate blowing ratios (1.0 < M < 1.5) and on a higher blowing ratio of M = 2.0. It can be shown that also for moderate blowing ratios the anti-kidney vortex pair is generated in the combined cooling jet. Thus, high adiabatic film-cooling effectiveness can be reached also for the case with a moderate blowing ratio. The lateral distribution of the cooling air is reduced compared to the cases of higher blowing ratios (M = 1.7, M = 2.0).
Experimental and Numerical Investigation of Rotating Bladed Disk Forced Response Using Under-Platform Friction Dampers
Authors: Sever Ibrahim A. , Petrov Evgeny E. , Ewins David J.
Published: March 2009

In this paper we present a methodology and results from an experimental investigation of forced vibration response for a bladed disk with fitted under-platform ‘cottage-roof’ friction dampers, together with the corresponding numerical predictions. A carefully-designed and constructed rotating test rig is used to make precise measurements which involve only the phenomena of interest. For this purpose, the measurement rig is operated under vacuum to eliminate aerodynamic effects on the rotating blisk and non-contact excitation and measurement techniques are employed so as not to modify the bladed disk dynamics. The experimental data measured are used for validation of multi-harmonic balance-based prediction tools developed at Imperial College. Predictions are carried out both with and without taking inherent mechanical mistuning into account, which is identified from measured data. Measured and predicted response curves are compared with each other and the degree of correlation is discussed.
Aerodynamic Design and Prototype Testing of a New Line of High Efficiency, High Pressure, 50% Reaction Steam Turbines
Authors: Cotroneo Joseph A. , Cole Tara A. , Hofer Douglas C.
Published: March 2009

The aerodynamic design and prototype performance testing of a new line of high efficiency, high pressure (HP), 50% reaction steam turbines is described in some detail. Three designs were carried out that can be used in a repeating stage fashion to form high efficiency steam paths. The designs were performed employing a blade master concept. The masters can be aerodynamically scaled and cut to cover a wide range of applications while maintaining vector diagram integrity. Three equivalent prototype flow paths, one each for Gen 0, 1 and 2, masters were designed and tested in a Steam Turbine Test Vehicle (STTV). These prototype designs are representative of high pressure steam turbines for combined cycle power plants. Design of experiments is used to optimize the flow path, stage counts and diameters for production designs taking into account multidisciplinary design constraints. Four such Gen 1 steam path designs have been executed to date as part of a structured series of combined cycle power plants. [1-5] There are two A14 HEAT* (High Efficiency Advanced Technology) steam turbine HP flow paths for GE’s 107FA combined cycle power plants and two A15 HEAT HP flow paths for the 109FB. The larger of the A14 HEAT steam turbine HP’s has recently been performance tested at a customer site demonstrating world class efficiency levels of over 90% for this low volume flow combined cycle turbine [1]. HP volume flows are likely to drop even lower in the future with the need to go to higher steam inlet pressure for combined cycle efficiency improvements so steam path designs with high efficiency at low volume flow will be increasingly important.
Using Thermoacoustic Analysis for Robust Burner Design
Authors: Bellucci Valter , Nowak Dariusz , Geng Weiqun , Steinbach Christian
Published: March 2009

Advanced thermoacoustic analysis is now routinely used in gas turbine combustor development. A thermoacoustic approach based on a combination of numerical analysis (CFD and three-dimensional acoustics), acoustic network models and dedicated measurements of acoustic flame response is well accepted across the industry. However, its application to specific combustor upgrade or development programs in “prediction mode” as opposed to “analysis mode” remains a challenge. This is mainly due to the large sensitivity of the complex methodology to key inputs, such as flame transfer functions, that can be only predicted in the burner design phase. This paper discusses an example where we made an effort to apply the thermoacoustic approach in predictive mode. The example refers to the upgrade of a first generation diffusion burner with a partially premix burner to achieve low emissions. Thermoacoustic instabilities were predicted as a limiting factor for combustor operation and thus a design parameter was identified to perform the thermoacoustic combustor tuning at engine level. A particular challenge of this development program was that no test rig was available. Therefore, the new premix burner was directly installed into a field engine where it was successfully tested.
A Study on the Flow Around the Scallops of a Mixed-Flow Turbine and Its Effect on Efficiency
Authors: Cox Graham , Wu Jason , Finnigan Ben
Published: March 2009

Automotive turbocharger radial inflow turbines are required to have both a high efficiency and a low inertia. In many cases this favours the use of a mixed-flow design. The inertia is minimised by scalloping the back-face, which removes a significant amount of material from the highest radius region of the hub. However, there is a concern that, for a mixed-flow geometry, the presence of a scallop introduces a forward-facing step to the inducer flow. This gives rise to the potential for an additional loss mechanism in the impeller. Two variants of a mixed-flow design, one having scallops and the other without, have been tested in a steady-state rig. The performance deltas are compared against the CFD representations. In reality there is the additional complexity of pulsing inlet conditions due to the operation of the exhaust valves of the piston engine. This causes severe variations in the inducer flow field. To assess whether the presence of a scallop might impair performance in an engine installation, a number of off-design CFD comparisons have been carried out using boundary conditions from a transient model covering a pulsing cycle.
Advanced Supersonic Component Engine for Military Applications
Authors: Lawlor Shawn P. , Steele Robert C. , Baldwin Peter
Published: March 2009

A 1500 kWe Brayton cycle engine is in development that has the efficiency of a diesel, but with the size, weight and maintenance attributes of a gas turbine. The Advanced Supersonic Component Engine (ASCE) combines many of the proven features of shock wave compression and expansion systems, commonly used in supersonic flight inlet and nozzle designs, with turbo-machinery practices employed in conventional axial flow gas turbines. The superior efficiency of the ASCE is a result of high pressure shock wave compression and supersonic expansion phenomena that produce high component efficiencies and a unique engine configuration that minimizes flow stream turning losses throughout the system. The engine employs a two stage counter-rotating configuration to achieve a 30:1 pressure ratio and a 42% simple cycle efficient engine to drive a high-speed direct drive permanent magnet (PM) electric motor/generator for all electric power and propulsion applications. The system promises a specific fuel consumption equal to or better than current reciprocating diesel engines in this size range, but with a 10:1 weight reduction and a 4:1 improvement in time-between-overall compared to marine diesel systems in this size range. This is a 2:1 increase in fuel efficiency at full power over existing gas turbines in this size range.
A Stability Analysis of Constrained Rotating Disks With Different Boundary Conditions
Authors: Khorasany Ramin M. H. , Hutton Stanley G.
Published: March 2009

The vibration behavior of constrained high speed rotating disks is of interest in industries as diverse as: aerospace, computer disk manufacture and saw design and usage. The purpose of this study is to investigate the stability behavior of guided circular disks with different boundary conditions. The equations of motion are developed for circular rotating disks constrained by space fixed linear, mass, spring, damper systems. The resulting equation of motion is a two dimensional fourth order partial differential equation that requires numerical solution. The Galerkin Method is employed using the eigenfunctions of the stationary non-constrained disk as approximation functions. Of interest is the effect on stability of conditions at the inner boundary. In particular the difference in behavior for centrally clamped, and splined disks (those disks that run on a spline arbor) is investigated. Also discussed is the effect of constraints on the flutter and divergence instability boundaries. Preliminary experimental results are presented for constrained splined disks, and these results are compared with the analytical predictions.
Aerodynamics of a Low-Pressure Turbine Airfoil at Low-Reynolds Numbers: Part 1 — Steady Flow Measurements
Authors: Mahallati Ali , McAuliffe Brian R. , Sjolander Steen A. , Praisner Thomas J.
Published: March 2009

This two-part paper presents a detailed experimental investigation of the laminar separation and transition phenomena on the suction surface of a high-lift low-pressure (LP) turbine airfoil, PakB. The first part describes the influence of Reynolds number, freestream turbulence intensity and turbulence length scale on the PakB airfoil under steady inflow conditions. The present measurements are distinctive in that a closely-spaced array of hot-film sensors has allowed a very detailed examination to be made of both the steady and unsteady behaviour of the suction surface boundary layer. In addition, this paper presents a technique for interpreting the transition process in steady, and periodically unsteady, separated flows based on dynamic and statistical properties of the hot-film measurements. Measurements were made at Reynolds number varying from 25,000 to 150,000 and for freestream turbulence intensities of 0.4%, 2% and 4%. Two separate grids were used to generate turbulence intensity of 4% with integral length scales of about 10% and 40% of the airfoil axial chord length. The first is comparable with the turbulence length scales expected in the engine and the second is considerably larger. While the higher levels of freestream turbulence intensity promoted earlier transition and a shorter separation bubble, the varying turbulence length scale did not have a noticeable effect on the transition process. The size of the separation bubble increased with decreasing Reynolds number, and under low freestream turbulence levels the bubble failed to reattach at low Reynolds numbers. As expected, the losses increased with the length of the separation bubble on the suction side of the airfoil, and increased significantly when the bubble failed to reattach.
CFD Simulation of Water Injection in GT Inlet Duct Using Spray Experimentally Tuned Data: Nozzle Spray Simulation Model and Results for an Application to a Heavy-Duty Gas Turbine
Authors: Bianchi Michele , Chaker Mustapha , De Pascale Andrea , Peretto Antonio , Spina Pier Ruggero
Published: March 2009

This study describes an application of Computational Flow Dynamics (CFD) to the two-phase flow problem of water injection into a compressor inlet duct for fogging systems. The paper addresses issues related to the CFD setup and the developed spray simulation model. Water injection is simulated by fitting experimental data on sprays obtained from industrial nozzles. In particular, the initial droplets size distribution is defined in accordance with results of laboratory tests on impaction-pin type nozzles. By using a commercial CFD software, 3D numerical simulations have been carried out on a typical gas turbine inlet duct. The effects of the duct geometry, filter and silencer on the duct internal air flow-field were analyzed. Finally, the effect of water injection carried out by means of an array of nozzles in the inlet duct is investigated. The paper presents the CFD two-phase results obtained for the application case under study; the analysis of the compressor bellmouth conditions due to the evaporation phenomenon is included in the paper.
The Application of Boundary Layer Blowing to a Highly Separated Flow Condition
Authors: Banks Kevin , Herring Steven J.
Published: March 2009

The potential consequences of climate change are leading to large scale interest in the development of renewable energy sources. The conversion of wave energy into electrical power is particularly attractive to countries such as the UK which have ready access to this resource. A considerable amount of research has been conducted over the past 30 years or so into the design of Oscillating Water Column (OWC) power plants, but it is clear from this that the levels of efficiency achieved by the turbine need to be considerably improved in order for such power plants to become economically viable. An important factor which limits the level of power conversion efficiency achieved is the development of highly separated flow regions during the operating cycle, which severely reduces performance. There are consequently large performance benefits to be gained if the degree of flow separation can be significantly reduced, or ideally removed. A technology which could have such an effect is boundary layer blowing. The paper describes an investigation into the application of boundary layer blowing to the type of highly separated flow condition which occurs in impulse turbine configurations intended for use in OWCs. The results have shown considerable promise that further development of this technology could play a part in increasing the overall economic viability of OWC power plants.
Lecture on Gas Turbine Cycle Analysis Aimed at Application to Catalog Data From Commercially Available Machines
Authors: Wettstein Hans E.
Published: March 2009

Subject of this paper is a lecture on calculating an open gas turbine cycle with realistic pressure drops and realistic blading efficiencies using only published catalog data and some additional assumptions. Emphasis is given on the experiences gained from the preparation of a lecture for a computerized education platform (“CompEdu”). The first student feedback is reported too. The lecture explains the use of the program, the sequence of solution for this specific task, how and why the calculation program is built up this way and how results can be interpreted. A student having worked through this lecture should be able to use or modify the program and to judge the accuracy of her/his produced cycle datasets.
Numerical Simulation of Turbulent Flows in Centrifugal Compressor Stages With Different Radial Gaps
Authors: Smirnov Pavel E. , Hansen Thorsten , Menter Florian R.
Published: March 2009

Numerical simulation of three-dimensional flow in a one-stage centrifugal compressor with a diffuser of variable geometry has been performed using the ANSYS CFX 10 code. The computations were conducted using steady and unsteady flow formulations and employing the RANS two-equation turbulence models. Steady-state flow simulations in the compressor were done for two vaned diffuser geometries with different radial gaps. A detailed comparison with the experimental data reported in the literature for different operating points of the “Radiver” test case compressor is presented and discussed. Good agreement of the computed velocity field with the measurements data is obtained at the impeller exit. Downstream of the diffuser vane, prediction quality depends on the operating point. Transient simulations performed for the best operating point of the compressor did not improve considerably predictions of flow characteristics in the diffuser as compared to the steady-state approach.
The Development of a Computational Tool for Improving the Productivity of the CFD Process: Part 1 — Mesh Quality Control
Authors: Favaretto Carlos Felipe , Dawes Bill
Published: March 2009

This paper presents the first part of the development of a mesh manipulation application, MeshTools. The proposed tool eliminates the necessity of revisiting a CAD system when making geometrical changes on the CFD model by directly modifying the node coordinates. In addition to that, a robust built-in mesh quality optimization routine guarantees a standard quality for the output mesh. MeshTools was integrated with a widely used commercial CFD code and several turbomachinery related test cases are reported.
On Effects of Impeller-Diffuser Interaction in the “Radiver” Centrifugal Compressor
Authors: Boncinelli Paolo , Ermini Mirco , Bartolacci Samuele , Arnone Andrea
Published: March 2009

In the present work, effects of impeller-diffuser interaction were investigated in the “Radiver” centrifugal compressor stage exploiting CFD techniques. Two diffuser geometries, differing in the radial gap between impeller exit and diffuser inlet, were analyzed by means of both steady and unsteady computations at two different operating conditions. Physical mechanisms by which interaction affects the flow field were identified and discussed. Flow unsteadiness was found to marginally affect the stage performance, but to have a relevant impact on the flow field.
Fundamental Impact of Firing Syngas in Gas Turbines
Authors: Oluyede Emmanuel O. , Phillips Jeffrey N.
Published: March 2009

This paper addresses the impact of burning syngas in a large size, heavy-duty gas turbine designed to run on natural gas while maintaining hot section life. The process used to produce syngas is not discussed here; we mainly focus on analyzing the issues related to switching from natural gas to syngas on the gas turbine hot sections and the possibility of reducing the firing temperature in order to maintain the durability of the hot metal section life. The analysis indicate that the power output for a syngas-fired turbine plant could be increased as much as 20–25% when compared with the same turbine fired at the same metal temperature as the natural gas, however this increase in power output is also accompanied by an increase in the moisture content of the combustion products due largely to higher hydrogen content in the syngas and the increased turbine flow which contribute significantly to the overheating of turbine component parts. Correlations based on the hydrogen content as well as the lower heating value of the fuels were obtained in order to determine specific firing temperature reduction necessary to obtain durable metal temperature.
CFD-Based Throughflow Solver in a Turbomachinery Design System
Authors: Gu Fahua , Anderson Mark R.
Published: March 2009

Throughflow analysis is a critical component for the multi-stage axial turbomachine design. The Euler throughflow approach has been developed over the last couple of decades, but has been less successful than its early peer, the streamline curvature approach. In this paper an Euler throughflow approach is described for engineering applications. It includes the steps needed to construct the stream surface, such as modifications for the incidence and deviation, and the throat area correction. The flow angle difference at the trailing edge and in the downstream non-bladed gap stations is resolved, and the numerical loss from solving the Euler equation is removed as well. This solver has been integrated into a comprehensive turbomachinery design system. It creates and modifies the machine geometries and predicts the machine performance at different levels of approximation, including one-dimensional design and analysis, quasi-three-dimensional methods (blade-to-blade and throughflow) and full-three-dimensional steady-state CFD analysis. The flow injection and extraction functions are described, as is the implementation of the radial mass distribution. Some discussion is dedicated to the shock calculation. Finally, examples are provided to demonstrate the pros and cons of the Euler throughflow approach and also to demonstrate the potential to solve for a wider range of flow conditions, particularly choked and transonic flows that limit stream function based solvers.
Comparing Extended Port and Corrugated Wall Jet Impingement Geometry for Combustor Liner Backside Cooling
Authors: Esposito E. I. , Ekkad S. V. , Kim Yong , Dutta Partha
Published: March 2009

Impinging jets are commonly used to enhance heat transfer in modern gas turbine engines. Impinging jets used in turbine blade cooling typically operate at lower Reynolds numbers in the range of 10,000 to 20,000. In combustor liner cooling, the Reynolds numbers of the jets can be as high as 60,000. The present study is aimed at experimentally testing two different styles of jet impingement geometries to be used in backside combustor cooling. The higher jet Reynolds numbers lead to increased overall heat transfer characteristics, but also an increase in crossflow caused by spent air. The crossflow air has the effect of rapidly degrading the downstream jets at high jet Reynolds numbers. In an effort to increase the efficiency of the coolant air, configurations designed to reduce the harmful effects of crossflow are studied. Two main designs, a corrugated wall and extended ports, are tested. Local heat transfer coefficients are obtained for each test section through a transient liquid crystal technique. Results show that both geometries reduce the crossflow induced degradation on downstream jets, but the individual geometries perform better at different Reynolds numbers. The extended port and corrugated wall configurations show similar benefits at the high Reynolds numbers, but at low Reynolds numbers, the extended port design increases the overall level of heat transfer. This is attributed to the developed jet velocity profile at the tube exit. The benefit of the developed jet velocity profile diminishes as jet velocities rise and the air has less time to develop prior to exiting.
An Iterative Method for Blade Profile Loss Model Adaptation Using Streamline Curvature
Authors: Pachidis Vassilios , Pilidis Pericles , Templalexis Ioannis , Marinai Luca
Published: March 2009

The various incidence, deviation and loss models used in through-flow analysis methods, such as Streamline Curvature, are nothing more than statistical curve fits. A closer look at public domain data reveals that these statistical correlations and curve fits are usually based on experimental cascade data that actually display a fairly large scatter, resulting in a relatively high degree of uncertainty. This usually leads to substantial differences between the calculated and actual performances of a given gas turbine engine component. Typically, matching calculated results from a throughflow analysis against experimental data requires the combination of various correlations available in the public domain, through a very tedious, complex and time consuming ‘trial and error’ process. This particular study supports the view that it might actually be much more time-effective to “adopt” a given loss model against experimental data through an iterative, physics-based approach, rather than try to identify the best combination of available correlations. For example, the well-established “Swan’s model” for calculating the blade profile loss factor in subsonic and transonic axial flow compressors depends strongly on approximate correlations for calculating the blade wake momentum thickness, and therefore represents such a case. This study demonstrates this by looking into an iterative approach to blade profile loss model adaptation that can provide a relatively simple and quick, but also physics-based way of ‘calibrating’ profile loss models against available experimental data for subsonic applications. This paper presents in detail all the analysis necessary to support the above concept and discusses Swan’s model in particular as an example. Finally, the paper discusses the performance comparison of a two-dimensional, Streamline Curvature compressor model against experimental data before and after the adaptation of that particular loss model.
CFD Analysis of Flow in High-Radius Pre-Swirl Systems
Authors: Jarzombek K. , Benra F.-K. , Dohmen H. J. , Schneider O.
Published: March 2009

Pre-swirl systems of gas turbines are utilized to reduce the temperature of the cooling air during the transfer from the stationary into the rotating system of the turbine. The amount of temperature decrease between the pre-swirl nozzle and the receiver holes depends on many geometrical and operational parameters. For the design process of a cooling air system, simple but general 1D (one-dimensional) calculation methods are required. These models must comprise correlations describing all dominant flow effects in order to provide the most accurate results. For the development of such models, a good understanding of the flow behavior in the system is indispensable. In this contribution, a pre-swirl scheme consisting of the three main components: pre-swirl nozzle, pre-swirl cavity and receiver hole is investigated numerically for different configurations. The cavity of the system is described as a rotorstator system and as a rotor-rotor system. With both configurations, CFD (Computational Fluid Dynamics) simulations with the same set of boundary conditions are performed. The evaluation of the results shows the influence of each component on the three-dimensional structure of the flow. For different operating conditions, the flow inside the cavity is represented by streamlines and discussed in detail. In the cavity, the swirl distribution is shown for all configurations and compared to free vortex behavior. For some regions, where a strong decrease of total pressure is present, the flow pattern is described in detail. In view of the development of a 1D design method for a pre-swirl system, the described flow effects give some important hints.
The Influence of Blade Tip Gap Variation on the Flow Through an Aggressive S-Shaped Intermediate Turbine Duct Downstream a Transonic Turbine Stage: Part I — Time-Averaged Results
Authors: Marn A. , Go¨ttlich E. , Pecnik R. , Malzacher F. J. , Schennach O. , Pirker H. P.
Published: March 2009

The demand of further increased bypass ratio of aero engines will lead to low pressure turbines with larger diameters which rotate at lower speed. Therefore, it is necessary to guide the flow leaving the high pressure turbine to the low pressure turbine at a larger diameter without any loss generating separation or flow disturbances. Due to costs and weight this intermediate turbine duct has to be as short as possible. This leads to an aggressive (high diffusion) s-shaped duct geometry. To investigate the influence of the blade tip gap size of such a nonseparating high diffusion duct flow a detailed test arrangement under engine representative conditions is necessary. Therefore, the continuously operating Transonic Test Turbine Facility (TTTF) at Graz University of Technology has been adapted: A high diffusion intermediate duct is arranged downstream a HP turbine stage providing an exit Mach number of about 0.6 and a swirl angle of 15 degrees (counter swirl). An LP vane row is located at the end of the duct and represents the counter rotating low pressure turbine at larger diameter. In order to determine the influence of the blade tip gap size on the flow through such an s-shaped turbine duct measurements were conducted with two different tip gap sizes, 1.5% span (0.8mm) and 2.4% span. (1.3mm). The aerodynamic design of the HP vane, the HP turbine, the duct and the LP vane was done by MTU Aero Engines. The investigation was conducted by means of five-hole-probes with thermocouples, boundary layer rakes and static pressure taps at the inner and outer wall along the duct at several circumferential positions. Five-hole-probe measurements were done in five planes within the duct and in two planes downstream of the LP vane. A rough estimation of the duct loss is given at the end of the paper. Part II of this work deals with two-component Laser-Doppler Velocimeter (LDV) measurements at duct inlet directly downstream the HP blade to obtain unsteady information about the inflow. Additionally, oil film visualisation was used to get information about the surface flow at the outer and inner wall of the duct.
Helicopter IRS Engine Integration for the “FIRST” Technology Demonstrator Programme
Authors: Ponton Tony , Warnes Gordon
Published: March 2009

The balanced protection of military assets presents a major challenge to military rotorcraft customers. The proliferation of sophisticated threat systems (including simpler weapons cued by imaging hardware) has highlighted the need for signature suppression systems to be considered as an integral part of rotorcraft design. Suppression of emissions at source offers multiple synergies with other aircraft systems including aerothermal optimisation (minimised pressure losses & highest utility of air flows), enhanced efficiency of other defensive aids equipment, and increased operational effectiveness. The optimisation of the benefits of IR suppression to the helicopter platform as a whole is closely tied into the design of the engine and exhaust system. The achievement of a successful design thus requires the close cooperation of the airframe and engine manufacturers and the availability of the necessary design and assessment tools. This paper is intended to illustrate the many aspects of Infra-Red Suppressor (IRS) design and the tools required to enable successful IRS optimisation and airframe integration. The development of a generic Future Infra-Red Suppressor Technology (FIRST) and the supporting design & analysis capability are described. The FIRST technology development programme has yielded a generic, scaleable, retrofit helicopter IRS that balances aircraft signatures (multi-band IR & RADAR) and installation penalties (such as engine performance and operating costs) to yield a substantial increase in aircraft survivability when compared with existing IRS designs.
Automated CFD Analysis Within the Preliminary Combustor Design System PRECODES Utilizing Improved Cooling Models
Authors: Pegemanyfar Nima , Pfitzner Michael , Surace Marco
Published: March 2009

The design of state-of-the-art combustion chambers is based on a multitude of design rules. To use this knowledge more effectively and to accelerate the combustor design process an automated combustion chamber design tool is being developed within the European project INTELLECT D.M. (Integrated Lean Low Emission Combustor Design Methodology). Due to the automation of the design process the time required to set up a new preliminary combustion chamber design is reduced from weeks to hours. The development of the automated preliminary combustor design tool is described in [1]. The focus of this paper is on new developments of the design system PRECODES (preliminary combustor design system) including automated mesh generation and CFD simulation. Design rules and parameters are formalized and stored within an EXCEL database. The combustor layout process including the calculations of cooling air mass flows and the zonal layout is done automatically using this database. The layout process has to be iteratively adjusted in order to find an optimal design due to the nonlinear interdependence of some of the design variables. The EXCEL database provides information for two parametric CAD models. The first parametric model includes the flame tube, pre-diffuser, cowl, metering panel, heatshield and the casing. Therefore it is relatively complex and only used for weight approximation and visualization purposes. The second CAD model is a generic model of the flame tube providing the basis for the automatic CFD mesh generation and CFD simulations. The CAD geometry is transferred to the commercial grid generator ICEM-CFD via the ICEM internal direct CAD interface. Based on the CAD geometry a multiblock structured mesh is generated automatically. Due to the utilization of the same blocking master model for different flame tubes varying in combustor size and orientation, and size and position of the mixing holes the mesh topology differs only marginally between different designs. Thus the CFD simulations are well comparable. Different combustor configurations are generated based on input parameter changes, i.e. changing the pressure level, the zonal stoichiometry or the maximum allowable material temperatures. An overview of the present results and the potentials of applying the automated combustor design tool PRECODES is presented.
Hydrogen as a Pilot Gas to Improve Power Turndown in Simulated Ultra Low NOx Gas Turbine Combustion
Authors: Andrews Gordon E. , Delgadillo Eduardo Z. , Mkpadi Mike C. , Hayes Gary
Published: March 2009

The use of a central pilot with a well mixed radial swirler combustor was investigated, at 600K and atmospheric pressure, to improve the power turn down of a low NOx combustor design. Hydrogen was compared with natural gas as the pilot fuel, using between 11 and 29% of the total energy input as hydrogen pilot fuel. With natural gas at low powers there was a hydrocarbon and CO emissions problem, but good flame stability was achieved and there was flame propagation from the pilot to the well mixed main combustion. The use of hydrogen as a pilot gas resulted in a 90% reduction in the HC and CO emissions at the simulated low power conditions. However, there was a significant increase in NOx emissions. The use of hydrogen as a pilot is a simple way to introduce hydrogen into existing industrial gas turbines so that the CO2 reduction credits of 11–29% can be claimed, if the hydrogen comes from a renewable or carbon sequestrated source.
Liquid Fuelled Low NOx Radial Swirlers With Central Pilot Combustion
Authors: Andrews Gordon E. , Kim M. N. , Mkpadi Mike C. , Akande Sheriff A.
Published: March 2009

Radial swirlers have proved effective in achieving low NOx using natural gas and this work investigates their use with kerosene with and without a central NG pilot. Two kerosene fuel injection locations were compared: at the inlet to the vane passages on the centreline with co-flow injection and 20mm downstream of the 76mm diameter swirler exit through the wall of a 76mm diameter 40mm long discharge duct. Flash back and auto ignition problems cannot occur with the downstream wall fuel injection location. All configurations were also tested with natural gas so that the difference in emissions due to the change from gas to liquid fuel could be established. The results show that ultra low NOx emissions can be achieved for kerosene with vane passage injection and that the use of a central pilot increases the NOx but improves the flame stability and power turndown. However, on liquid fuels the pilot to main flame propagation was not as good as when natural gas was used as the main fuel. Liquid fuel injection at the radial swirler wall outlet was effective but had slightly higher NOx for lean mixtures and worse HC and CO emissions. However, for richer primary zone mixtures the NOx was lower than for vane passage injection and this indicated that rich/lean combustion was occurring, without the uniform mixing and low NOx combustion that occurred with natural gas injection at this location.
Non-Linear Rotor-Rubbing Vibration Analysis Through the Wavelet Transform
Authors: Jauregui Juan C. , Rubio Eduardo , Gonzalez Oscar
Published: March 2009

Vibration analysis is the basis for an early detection of faults in rotating machinery. It is the main element for any maintenance program. Due to the basics of the FFT (Fast Fourier Transform), vibration prediction systems based on this analysis tool are unable to identify unsteady and non-linear vibrations. They provide only the spectrum content of a signal, but due to its nature, the time interval and the instant when the vibration occurs are eliminated. Therefore, new modern signal analysis tools have been developed. Among them, wavelets have been extensively applied to non-linear vibration and transient analysis. In the case of a rotor rubbing the housing or the bearing, wavelets allow the identification of the “wave shape” through a predetermined time-frequency function. The challenge of this method is the definition of the function that represents the actual phenomenon. Results show that rubbing is a non-linear phenomenon, this was verified through a ramp-up and ramp-down test procedure. It was found that the most appropriate procedure for its identification is through wavelet analysis. The key factor is the definition of the best-fit wavelet.
Planar Duct Heat Transfer With Turbulence Enhancing Obstacles for Combustor Liner External Cooling
Authors: Andrews Gordon E. , Khalifa Ibrahim M.
Published: March 2009

Parallel plate combustor wall cooling was investigated. The combustor air flowed down the gap between two flat surfaces in a low pressure loss configuration. The work was aimed at combustor liner external air cooling for regenerative combustor cooling prior to entering a lean low NOx combustor. The test rig was 152 mm square and the test section was a duct of 152mm width and height of 10 and 5mm with a 152mm length. The experimental investigation involved the measurement of the heat transfer coefficient using the lumped capacity method. together with overall wall cooling effectiveness measurements in a hot duct test rig. The compromise between increased pressure loss and enhanced heat transfer for obstacles in the duct was investigated. It was shown that at coolant flow rates comparable with combustor requirements, adequate wall cooling effectiveness could be achieved using this technique. The cooling effectiveness performance was compared with the alternative technique of impingement cooling using low impingement jet pressure loss.
An Energy-Based Method for Multi-Axial Fatigue Life Calculation
Authors: Scott-Emuakpor Onome , Shen M.-H. Herman , George Tommy , Cross Charles
Published: March 2009

An accelerated method for determining the material strength of Aluminum 6061-T6 has been developed for prediction of fully-reversed shear and biaxial fatigue life. The framework for this accelerated method is developed in accordance with a previously developed uniaxial energy-based prediction approach, which states: the total strain energy dissipated during a monotonic fracture and a cyclic process is the same material property, where each can be determined by measuring the area underneath the monotonic true stress-strain curve and the area within a hysteresis loop, respectively [1]. The developed framework consists of the following two elements: (1) The development of a life prediction and estimation implementation scheme for calculating effective shear fatigue life cycles, and (2) the development of a constitutive law for multi-axial fatigue life prediction based on analytical comparison with biaxial fatigue experimental data. A comparison between these two framework elements and experimental results for Al 6061-T6 has been conducted to show that there is good agreement, thus validating the prediction method and the developed procedures of the entire framework.
The Effect of Blade Leading Edge Platform Shape on Upstream Disk Cavity to Mainstream Flow Interaction of a High-Pressure Turbine Stage
Authors: Marini Remo , Girgis Sami
Published: March 2009

This paper presents a CFD study of a transonic highpressure 1-stage turbine that includes the blade upstream disk cavity. The emphasis of the analysis was to understand and quantify the impact of the blade leading edge platform shape on the flow interaction between the upstream disk cavity flow and the gaspath mainstream flow. Two blade platform shapes were analyzed: a recessed and a raised leading edge shape. The results presented include steadystate and transient simulations in order to describe the flow interaction and quantify the impact on stage efficiency. A sensitivity analysis on the amount of cavity flow was performed to investigate the impact on secondary losses (interpreted by entropy generation) and stage efficiency. It was found that the blade leading edge platform shape and cavity flow amount affected the blade hub passage vortex structure and location. At the nominal engine condition, the raised leading edge platform shape showed an improvement in stage efficiency. It also showed a reduced sensitivity of stage efficiency due to cavity flow amount.
Heat Transfer From Low Aspect Ratio Pin Fins
Authors: Lyall Michael E. , Thrift Alan A. , Kohli Atul , Thole Karen A.
Published: March 2009

The performance of many engineering devices from power electronics to gas turbines is limited by thermal management. Heat transfer augmentation in internal flows is commonly achieved through the use of pin fins, which increase both surface area and turbulence. The present research is focused on internal cooling of turbine airfoils using a single row of circular pin fins that is oriented perpendicular to the flow. Low aspect ratio pin fins were studied whereby the channel height to pin diameter was unity. A number of spanwise spacings were investigated for a Reynolds number range between 5000 to 30,000. Both pressure drop and spatially-resolved heat transfer measurements were taken. The heat transfer measurements were made on the endwall of the pin fin array using infrared thermography and on the pin surface using discrete thermocouples. The results show that the heat transfer augmentation relative to open channel flow is the highest for smallest spanwise spacings and lowest Reynolds numbers. The results also indicate that the pin fin heat transfer is higher than the endwall heat transfer.
Analysis and Control of Part-Load Unsteady Flow in Francis Turbine’s Draft Tube
Authors: Zhang Ri-Kui , Mao Feng , Wu Jie-Zhi , Chen Shi-Yi , Wu Yu-Lin , Liu Shu-Hong
Published: March 2009

By using the Reynolds-averaged Navier-Stokes (RANS) equations, the complex unsteady vortical flow in the entire draft tube of a Francis turbine under a part-load condition, with severe low-frequency pressure fluctuation, is investigated numerically to gain an in-depth understanding of the physical characters of the flow including its stability and robustness, and thereby to seek effective control means to alleviate or even eliminate the strong pressure fluctuation. Our main findings are as follows: In the cone segment of the draft tube, the vortex rope is due to the global instability of the flow caused crucially by the reversed axial flow at the inlet. In the elbow segment of the draft tube, the reversed flow coexists side by side with a fluid channel that carries the mass flux downstream due to favorable axial pressure gradient. In the outlet segment of the draft tube, the mass-flux channel always goes through a fixed outlet, leaving the other two with nearly zero flux. The entire draft-tube flow, although undesired under part-load condition, forms a globally robust system. The principles for effectively controlling this complex flow are proposed. A simple water jet injection at the inlet is numerically proven successful.