bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigations of Film Flows Around Obstacles
Authors: Kneer Johannes , Eastwick Carol , Mu¨ller Armin , Johnson Graham , Robinson Adam , Bauer Hans-Jo¨rg
Published: August 2009

Within an aero-engine bearing chamber oil is provided to components to lubricate and cool. This oil forms a moving film around the inside of the bearing chamber which provides cooling to the chamber walls. Where the walls have features such as bolt heads or bearing supports protruding from the surface the oil film is forced to flow either over or around these features. If the film becomes too thin, or dries out, the cooling becomes ineffective and local hot spots occur which can precipitate coking. The work reported in this paper is a continuation from two previous papers [9, 10] using experimental methods to characterise the disruption to film flow near obstructions. This fundamental study provides insight into likely flow behaviour near obstructing features and is part of a larger set of projects to understand film flow around bearing chamber walls. In the study two rigs are employed: an inclined plane rig and a stratified liquid-gas tunnel used in the previous work. In both rigs the working fluid is tap water at ambient conditions, chosen for ease of use and because the viscosity and density of water at room temperature (≈20 °C) are representative of those of aero-engine oil at a typical operating temperature (between 100 °C to 200 °C). Two measurement methods are used to map flows around penetrating and sub-film obstacles, a needle contact probe and a Laser Focus Displacement Meter. In addition, visualisation is used to provide more details on flow behaviour. The conclusion from the work indicates that, for a bearing chamber, it is best not to have a series of obstacles directly in a line with each other as there will be a significant variation of film height and velocity caused by the obstacles across the bearing chamber wall. However, the effect is reduced for higher gas flow rates, which more closely match chamber conditions for large turbofans. It is recognized that in an engine there is significant vibration, the surfaces are not hydraulically smooth and that temperature will have a major role on the final effect on film flow and that these effects are not considered in this fundamental work.
The Effect of Wall Thickness on Nozzle Suction Side Film Cooling
Authors: Zhang Luzeng , Moon Hee Koo
Published: August 2009

The effect of nozzle airfoil wall thickness on nozzle suction side film cooling effectiveness was experimentally investigated. The engine operating conditions were simulated in a scaled warm cascade, which was built based on industrial gas turbine nozzle airfoils. Film effectiveness distribution on the suction surfaces was obtained using the pressure sensitive paint (PSP) technique. Nitrogen gas was used to simulate cooling flow as well as a tracer gas to indicate oxygen concentration such that film effectiveness by the mass transfer analogy could be obtained. Two nozzle test models were investigated, which had similar cooling supply plenums. One of them had a wall thickness of 0.47cm and the other 0.63 cm. The nozzle vanes had showhead and film cooling holes on two suction side locations. Six cooling mass flow ratios (MFR, blowing ratios) were studied for each of the nozzle test models and two-dimensional film effectiveness distributions were obtained. Then the effectiveness distributions were spanwise averaged for comparison. For both cases, the overall film effectiveness increased with the MFR or the blowing ratio. Comparing the two models, the thicker wall (or the larger L/D value) resulted in improved film effectiveness for the lower MFR’s. For the higher MFR, the better-developed jets due to the thicker wall (or the larger L/D) would cause a jet lift-off; therefore reduce the overall film effectiveness. The spanwise shifting pattern was also depended on the wall thickness.
Topology-Optimized Intermediate Casing of Aero Engine and Comparative Evaluation of Titanium and Composite Architecture in Terms of Load Capacity and Weight Reduction
Authors: Kober Markus , Lenk Olaf , Klauke Thomas , Ku¨hhorn Arnold
Published: August 2009

From Aero Engines of the future it is demanded to provide more power, while the fuel consumption and the mass should decrease. In order to reach the goal of an increasing specific power or a decreasing specific mass, respectively, structural optimization methods, like the topology optimization, find their way into the design process to a greater extent. Additionally one is going to consider more and more fiber reinforced composites as a substitute for titanium alloys in the “cold” structure of the engine. Composite materials offer significant advantages especially concerning the specific mass and the adjustability of their stiffness properties. Unfortunately it is very difficult to predict damage and fracture of such orthotropic materials. The presentation will show the results of a topology optimization of the titanium intermediate-casing of a Rolls-Royce aero engine. Further on the material of the casing will be substituted by a carbon fiber reinforced composite. The fiber orientations and layer thicknesses of the composite are optimized under certain strength constraints, which are described by a modern fracture plane based failure criterion (NASA LaRC04 criterion [6]). Such a failure criterion has a lot of advantages compared to classical ones like Tsai-Hill, Tsai-Wu, ..., which e.g. do not distinguish between fiber and inter-fiber fracture and are therefore not able to predict the type of inter-fiber fracture. Finally the results of the optimization with the current material titanium will be compared to the results of the composite-made intermediate casing in terms of their load capacity and weight.
Air Cushion Vehicle Turbofan Propulsion Feasibility Analysis
Authors: Zipkin David , Shappell Lance
Published: August 2009

This paper explores the feasibility of utilizing turbofan gas turbines for combined propulsion and lift on an amphibious air cushion vehicle (ACV). The required thrust and bleed flow were identified, and employed to select possible COTS turbofans for this application. In addition, the turbofan cycle was evaluated for ACV applicability. The investigation revealed that a turbofan configuration would require a new inlet filtration system, which was categorized as high risk. Furthermore, fuel comparisons showed that the turbofan arrangement would require significantly more fuel when compared to the traditional propeller and lift fan system.
Experimental and Numerical Investigations on Turbine Airfoil Cooling Designs: Part II—An Investigation on Heat Transfer Features by Infrared Thermal Imaging Technique
Authors: Wang J. H. , Xu H. Z. , Ma L. , Wu X. Y. , Yang S. J.
Published: August 2009

Experimental and numerical investigations are conducted to understand the heat transfer characteristics of a double-wall film-cooled configuration. To validate the numerical method for describing the heat transfer process of the complex configuration, an infrared thermal imaging (ITI) system is used. Through the ITI system, two-dimensional temperature distributions over the coversheet of the configuration are captured. The experiments are carried out in a hot gas wind tunnel with an electrical heater of 30kW. The specimen used in the experiments has an actual size of gas turbine engines, and an integral structure of the coversheet and columnar ribs is processed by a numerically controlled milling machine. Numerical calculations are carried out by an alternant iteration algorithm between velocity field and temperature field, and the shear-stress-transport k-ω model and locally refined T-grid validated by the first part of this work are used. The numerical results are compared with the thermal image captured by the ITI system. The influences of coolant impingement and cross flow within the configuration, coolant film effect at the coversheet, heat conduction through the ribs on the overall cooling effectiveness at the coversheet are illustrated and discussed. The objective of this investigation is to provide a preparation for the next work, to estimate the thermal stress and reliability of the double-wall cooling configurations.
Blade Vibration Phenomena of HPC Bliscs Considering Manufacturing Effects and Strain Gauge Application
Authors: Klauke T. , Ku¨hhorn A. , Beirow B. , Parchem R.
Published: August 2009

Compared to conventional bladed disc assemblies with heavy blade-disc connections, the integrated design (blisc) of modern aero engine compressors results in reduced rotor masses, facilitates higher maximum rotational velocities and improved pressure ratios (increased efficiency factors). Apart from these advantages a number of disadvantages occur. Some of them are for example a very low structural damping and a higher sensitivity to manufacturing- and material tolerances (mistuning). This results in localized vibration modes, higher displacement amplitudes, critical stress levels and reduced high cycle fatigue (HCF) of several blades due to inauspicious aerodynamic excitations. From this, an optimum choice of blades to be instrumented with strain gauges (s/g) is the basis of a convincing vibration monitoring system during rig tests. Based on an extensive measurement campaign and numerical investigations an overview of all major manufacturing effects (blisc milling, rotor tip grinding, welding the single bliscs together, compressor assembly) and also the strain gauge application itself on the vibration behavior of real mistuned bliscs will be presented for a multi-stage high pressure research compressor (HPC) in detail (see Fig. 1). The investigations show, that the original blade mistuning deviations resulting from the initial blisc milling procedure remain until the last manufacturing process of the aero engine and still dominate the blisc forced response behavior during aerodynamic excitation. In contrast to this effect, rotor tip grinding procedures as well as the assembly of the rotor drum only cause an even frequency shift of every blade, which does not significantly change the blisc behavior. Complementary to the influence of manufacturing-caused blade mistuning on the whole rotor balance, the effects of an application of high-temperature strain gauges on HPC-blades will be discussed regarding the modification of the blisc vibration modes. Finally different methods will be introduced aiming at a compensation of the strain gauge induced blade stiffening depending on the blade dimensions to ensure the best possible vibration monitoring results.
Experimental Study of Oblong Exhaust Ejectors With Multi-Ring Oblong Entraining Diffusers
Authors: Chen Qi , Birk A. M.
Published: August 2009

This paper presents experimental data for the performance of two oblong, straight, air-air ejectors with 4-ring oblong entraining diffusers. The effects of inlet swirl angle, nozzle diameter and flow temperature on the ejector pumping, back pressure, wall pressure distribution, diffuser pressure recovery and surface film cooling effectiveness were studied. The experiments were carried out on a hot gas wind tunnel that could provide primary mass flow rates up to 2.2 kg/s at ambient temperature and 1.8 kg/s at 500°C. Velocity, pressure and temperature were measured in the annulus upstream of the primary nozzle, on the mixing tube and diffuser walls, at the diffuser gap inlets and at the diffuser exit. A comparison between the performance of the oblong ejector and a round ejector indicated that for a short length ejector, the oblong ejector provided better overall performance in terms of pumping and velocity and temperature distributions.
Transition Modeling Effects on the Simulation of a Stator Cascade With Active Flow Control
Authors: Mertens Dirk , Thiele Frank , Swoboda Marius , Huppertz Andre´
Published: August 2009

An investigation of a stator cascade is undertaken by means of steady 3D RANS simulations, the focus of which is on two computational setups. The first takes transition effects into account using a correlation-based transition model as suggested by Abu-Ghannam and Shaw, while the second is considered to be fully turbulent. In a first step the base flow is validated by experimental measurements, followed by configurations employing active flow control by means of steady jets with varying mass flow. By investigating the differences arising due to the varying level of modeling complexity the necessity of using a transition model can be illustrated.
Nonlinear Stochastic Dynamics, Chaos and Reliability Analysis for Single Degree Freedom Model of a Rotor Blade
Authors: Kumar Pankaj , Narayanan S.
Published: August 2009

In turbo machinery, the analysis of systems subjected to stochastic or periodic excitation becomes highly complex in the presence of nonlinearities. Nonlinear rotor systems exhibit a variety of dynamic behaviours that include periodic, quasi periodic, chaotic motion, limit cycle, jump phenomena etc. The transitional probability density function (pdf) for the random response of nonlinear systems under white or coloured noise excitation (delta-correlated) is governed by both the forward Fokker-Planck (FP) and backward Kolmogorov equations. This paper presents efficient numerical solution of the stationary and transient form of the forward FP equation corresponding to two state nonlinear systems by standard sequential finite element (FE) method using C0 shape functions and Crank-Nicholson time integration scheme. For computing the reliability of system, the transient FP equation is solved on the safe domain defined by D barriers using the FE method. New approach for numerical implementation of path integral (PI) method based on non-Gaussian transition pdf and Gauss-Legendre scheme is developed. In this study, PI solution procedure is employed to solve the FP equation numerically to examine some features of chaotic and stochastic response of nonlinear rotor systems.
Numerical Simulation of TOBI Flow: Analysis of the Cavity Between a Seal-Plate and HPT Disc With Pumping Vanes
Authors: Gupta Anish Kumar , Ramerth Douglas , Ramachandran Dhinagaran
Published: August 2009

HP turbine cooling systems utilize a TOBI (tangential on-board injector) nozzle and seal-plate to deliver cooling air to the airfoils with minimal loss in pressure and a benefit in relative total temperature. It was necessary to have a low TOBI exit pressure to control excess leakage across adjacent labyrinth seals with a trade-off of maintaining adequate pressure to supply blade cooling. Consequently, pumping vanes were needed on the seal-plate to restore pressure, which adds parasitic work to the turbine and a corresponding loss of engine efficiency. Engine testing revealed recirculation zones attached to the radial pumping vanes. Subsequent numerical simulation corroborated the recirculation and resulting circumferential asymmetry in flow distribution to the cooled airfoils. As a consequence, excess cooling air is supplied to the HP rotor with some airfoils receiving the minimum amount of cooling air. This study seeks to improve the flow distribution and pumping effectiveness by means of contouring the pumping vanes, increasing pumping vane solidity and/or controlling diffusion by re-contouring the seal-plate surface. Design features that increase total through flow when overall pressure ratio is fixed are also explored.
Off-Design Operation of the Multi-Fuel CHP Cycles
Authors: Kosman Wojciech
Published: August 2009

The paper describes the problems when the operation regime of the CHP cycle is adjusted according to the user demands. The analysis concerns a multi-fuel system, which utilizes biomass, natural gas and coal. The analyzed system consists of a combined gas and steam cycles. The analysis presented here concerns off-design operation caused by part loading, varying ambient conditions and power demands. An appropriate division of the load between the sub-cycles increases the overall efficiency. The analysis concerns also various options of biomass supply to the system. The research regards mostly the effectiveness criterion as it has a direct influence on the costs of operation.
The Performance Evaluation of Variations of Diffuser Geometry of the Centrifugal Compressor in a Marine Engine (70MW) Turbocharger
Authors: Kim Hong-Won , Park Jong-Il , Ryu Seung-Hyup , Choi Seong-Wook , Ghal Sang-Hak
Published: August 2009

An examination of the condition of the flow leaving the impeller exit kinetic energy often accounts for 30–50% of the shaft work input to the compressor stage, and for energy efficiency it is important to recover as much of this as possible. This is the function of the diffuser which follows the impeller. Effective pressure recovery downstream of an impeller is very important to realize a centrifugal compressor with high efficiency and high pressure ratio, and an appropriate selection of a diffuser for a specific impeller is a critical step to develop the compressor accordingly. The purpose of this study is to investigate the sensitivity of how compressor performances changes as vaned diffuser geometry is varied. Three kinds of vaned diffusers were studied and its results were compared. First vaned diffuser type is based on modified NACA airfoil and second is channel diffuser and third is conformal transformation of NACA 65 airfoil. A mean-line prediction method was applied to investigate the performance and stability for three kinds of diffusers. And CFD analyses have been done for comparison and detailed interior flow pattern study. In this study, the off-design behavior of three different types of diffusers, given by mean-line prediction, was investigated using CFD results and selected the NACA 65 diffuser geometry which satisfy wider operating range and higher pressure recovery than the others. The numerical results were compared with experimental data for validation.
3D Thermo-Mechanical Modelling Method to Predict Compressor Local Tip Running Clearances
Authors: Benito Diego , Dixon Jeff , Metherell Paul
Published: August 2009

This paper presents a 3D thermo-mechanical modelling method to calculate compressor local tip running clearances. The method requires a solid geometry representation of the compressor casings and main engine structures, including local geometry features such as thrust lugs, gearbox, sump, offtake bosses and struts. The finite element model is capable of predicting asymmetric temperature and displacement distributions for transient and steady-state conditions as a result of thermal, pressure and mechanical loads (e.g. thrust, gas torques, gravity, gusts, etc). This methodology has been applied to calculate local tip clearances on the intermediate pressure compressor of a civil aero-engine. The results from the 3D solid model have been compared to those obtained with more conventional analysis tools (i.e. 2D axisymmetric thermo-mechanical models and 3D isothermal shell and beam models) in order to build confidence in the new methodology. Local tip running clearances were measured on the intermediate pressure compressor by means of capacitance probes. Measured local closures for a typical square cycle including a low power idle phase and high power max take-off phase have been compared to predicted local closures to establish the validity of the new methodology.
Detailed Internal Measurements of a Siemens Combustor Operating at Gas Turbine Relevant Conditions
Authors: Wedlock M. , Wood J. P. , Miller M. N. , Sims G. J. , Liu K. , Syed K. , Bowen P. , Crayford A. , Sevcenco Y.
Published: August 2009

In order to develop liquid fuelled DLE gas turbine combustors, especially to accommodate alternative more environmentally friendly fuels, it is necessary that their operation is well understood. Although CFD can appear to offer many insights into the operation of such burners this is only achieved by applying a number of individual models to predict each stage in the mixture preparation and combustion processes. While each model is validated individually, their overall performance in a complex system is not well understood. This paper therefore presents unique data that can be used to determine the overall validity of CFD predictions of a Siemens combustor. Such data was produced by QinetiQ by making detailed (approximately 200) gas analysis measurements in the interior of the combustor while operating at gas turbine relevant conditions using the Sector Combustion Rig at the GTRC Port Talbot. The data collected shows detailed information regarding the internal processes of the combustor, and is therefore ideally suited to the validation of CFD.
A Fluidic Actuator for Active Combustion Control
Authors: Guyot Daniel , Paschereit Christian Oliver , Raghu Surya
Published: August 2009

In this work the performance of a fluidic actuator in an active combustion control scheme is demonstrated. The actuator was tested in two different burner configurations, a bluff body burner and a generic swirl-stabilized burner, where it modulated parts of the fuel flow. The oscillation frequency was controlled by varying the inlet mass flow of the actuator. Fluidic actuators are of special interest for fuel-based active control schemes featuring high frequency fuel flow modulation, as they are much more durable then conventional valves due to the absence of fast moving parts. Hot wire measurements were performed to investigate the fluidic actuator’s oscillation characteristics without combustion. The actuator was then incorporated into a bluff body burner and a swirl-stabilized burner, respectively, where it modulated parts of the fuel flow blended with nitrogen. Pressure and heat release fluctuations in the combustor were recorded and images of the flame were taken. For both burners the heat release response of the flame to fuel flow modulation was first studied during stable combustion. The spectra of the heat release signals showed a clear peak corresponding to the fluidics’ oscillation frequency, thus validating the ability of the actuator to influence the combustion process. As the next step, each of the two combustors was operated at conditions that featured a strong low-frequency combustion instability when no fuel was modulated. In case of the bluff body burner applying fuel modulation resulted in attenuation of the combustion instability for some oscillation frequencies. The attenuation was highest when modulating the fuel flow in between the fundamental instability frequency and its subharmonic. Modulating the fuel flow at the subharmonic, however, resulted in an amplification of the instable mode. Also when applied to the swirl burner, the fludics’ fuel flow modulation caused a significant reduction of the pressure oscillations, although the actuator could only be operated at oscillation frequencies much lower than the instability frequency due to the attached tubes. The results obtained in this work show that the fluidic actuator in use allows for fuel modulation and hence combustion control without the need for complex and fast moving parts, thus ensuring a long actuator lifetime. This makes the fluidic actuator highly appropriate for application in industrial gas turbines.
Aerodynamic Performance of Suction-Side Gill Region Film Cooling
Authors: Chappell Justin , Ligrani Phil , Sreekanth Sri , Lucas Terry , Vlasic Edward
Published: August 2009

The performance of suction-side gill region film cooling is investigated using the University of Utah Transonic Wind Tunnel and a simulated turbine vane in a two-dimensional cascade. The effects of film cooling hole orientation, shape, and number of rows, and their resulting effects on the aerodynamic losses, are considered for four different hole configurations: round axial (RA), shaped axial (SA), round radial (RR), and round compound (RC). The mainstream Reynolds number based on axial chord is 500,000, exit Mach number is 0.35, and the tests are conducted using the first row of holes, or both rows of holes at blowing ratios of 0.6 and 1.2. Carbon dioxide is used as the injectant to achieve density ratios of 1.77 to 1.99 similar to values present in operating gas turbine engines. Presented are local distributions of total pressure loss coefficient, local normalized exit Mach number, and local normalized exit kinetic energy. Integrated Aerodynamic Losses (IAL) increase anywhere from 4 to 45 percent compared to a smooth blade with no film injection. The performance of each hole type depends upon the airfoil configuration, film cooling configuration, mainstream flow Mach number, number of rows of holes, density ratio, and blowing ratio, but the general trend is an increase in IAL as either the blowing ratio or the number of rows of holes increase. In general, the largest total pressure loss coefficient Cp magnitudes and the largest IAL aerodynamic losses are generally present at any particular wake location for the round radial RR or shaped axial SA configurations, regardless of the film cooling blowing ratio and number of holes. The SA shaped axial holes also generally produce the highest local peak Cp magnitudes. IAL magnitudes are generally lowest with the RA hole configuration. A one-dimensional mixing loss correlation for normalized IAL values is also presented, which matches most of the both rows data for RA, SA, RR, and RC hole configurations. The equation also provides good representation of the RA, RC, and RR first row data sets.
Optimization of a Centrifugal Impeller Using Evolutionary Algorithms
Authors: Bartold Andreas , Joos Franz
Published: August 2009

This paper presents the development and application of an automated optimization method for aerodynamic design of centrifugal impellers. The algorithm used for the optimization is an evolutionary algorithm. Within this method the shape of the centrifugal impeller is described using B-Spline curves. The method introduced is used for redesigning an existing impeller with regard to maximization of the isentropic efficiency at a fixed operating point. Here the isentropic efficiency is calculated using the solution of a compressible three-dimensional Reynolds-averaged Navier-Stokes solver. The presentation will show that the method presented provides a new design that outperforms the original impeller with respect to the particular objective and demonstrates its usefulness.
Asymptotic Description of Maximum Mistuning Amplification of Bladed Disk Forced Response
Authors: Martel Carlos , Corral Roque
Published: August 2009

The problem of determining the maximum forced response vibration amplification that can be produced just by the addition of a small mistuning to a perfectly cyclical bladed disk still remains not completely clear. In this paper we apply a recently introduced perturbation methodology, the Asymptotic Mistuning Model (AMM), to determine which are the key ingredients of this amplification process, and to evaluate the maximum mistuning amplification factor that a given modal family with a particular distribution of tuned frequencies can exhibit. A more accurate upper bound for the maximum forced response amplification of a mistuned bladed disk is obtained from this description, and the results of the AMM are validated numerically using a simple mass-spring model.
Aeroderivative Gas Turbines for LNG Liquefaction Plants: Part 2—World’s First Application and Operating Experience
Authors: Meher-Homji Cyrus , Messersmith Dave , Hattenbach Tim , Rockwell Jim , Weyermann Hans , Masani Karl
Published: August 2009

LNG market pressures for thermally efficient and environmentally friendly LNG plants coupled with the need for high plant availability have resulted in the world’s first application of high performance aeroderivative gas turbines for a 3.7 MTPA LNG plant in Darwin. The six engines utilized are GE PGT25+ engines rated at 32 MW ISO driving propane, ethylene and methane compressors. The paper describes the design, manufacture, testing, and implementation of these units focusing on both the gas turbine and the centrifugal compressors. Power augmentation utilized on these units is also discussed. An overview of operating experience and lessons learned are provided. Part 1 of this paper provides a detailed analysis of why high thermal efficiency is important for LNG plants from an economic and greenhouse gas perspective.
Windback Floating Oil Seal Optimization Using CFD
Authors: Chochua Gocha , Tecza Joseph , Lyons Michael
Published: August 2009

Floating oil ring seals are used at the shaft ends of centrifugal compressors to eliminate process gas leakage to the atmosphere. The windback feature of the seals consists of several spiral grooves machined into the inside diameter of the seal ring. These grooves use the rotation of the shaft to reduce sealing oil leakage. Because of the complex fluid behavior in and around a windback seal, it is difficult to develop a design tool for accurate prediction of leakage. To address this, a comprehensive CFD model was created to predict performance of windback seals. Then a Design of Experiments approach was used to create a response surface model of the seal leakage as a function of several geometrical and operational parameters. The response surface predictions are compared with available experimental data.
Low Frequency Noise Contamination in Fan Model Testing
Authors: Brown Clifford A. , Schifer Nicholas A.
Published: August 2009

Aircraft engine noise research and development depends on the ability to study and predict the noise created by each engine component in isolation. The presence of a downstream pylon for a model fan test, however, may result in noise contamination through pylon interactions with the free stream and model exhaust airflows. Additionally, there is the problem of separating the fan and jet noise components generated by the model fan. A methodology was therefore developed to improve the data quality for the 9 × 15 Low Speed Wind Tunnel (LSWT) at the NASA Glenn Research Center that identifies three noise sources: fan noise, jet noise, and rig noise. The jet noise and rig noise were then measured by mounting a scale model of the 9 × 15 LSWT model fan installation in a jet rig to simulate everything except the rotating machinery and in duct components of fan noise. The data showed that the spectra measured in the LSWT has a strong rig noise component at frequencies as high as 3 kHz depending on the fan and airflow fan exit velocity. The jet noise was determined to be significantly lower than the rig noise (i.e. noise generated by flow interaction with the downstream support pylon). A mathematical model for the rig noise was then developed using a multi-dimensional least squares fit to the rig noise data. This allows the rig noise to be subtracted or removed, depending on the amplitude of the rig noise relative to the fan noise, at any given frequency, observer angle, or nozzle pressure ratio. The impact of isolating the fan noise with this method on spectra, overall power level (OAPWL), and Effective Perceived Noise Level (EPNL) is studied.
Numerical Studies on Cavity-Inside-Cavity-Supported Flames in Ultra Compact Combustors
Authors: Katta Viswanath R. , Zelina Joeseph , Roquemore William M.
Published: August 2009

Cavities are incorporated in the designs of the future gas-turbine combustors for providing flame stability and, thereby, for improving the lean blowout characteristics. Recently, a Cavity-inside-cavity (CIC) design was proposed for the Air Force Research Laboratory’s ultra compact combustor (UCC). Numerical studies are performed in the present study to understand the dynamics of the CIC-supported flames. The complex CIC that was used in the actual hardware has been simplified for making it amenable to two-dimensional models. Calculations are performed for the modified CIC using a two-dimensional, unsteady, reacting flow code known as UNICORN. Direct numerical simulations and calculations using k-ε turbulence model are performed. A fast, global-chemistry model is used for studying the flame dynamics inside and in the wake region of CIC. Calculations are performed for several CIC geometries generated through varying the width of the cavity. The design CIC is found oversized for the secondary (circumferential) airflow used in UCCs. A detailed chemistry model is also used for understanding the blowout characteristics of the CIC-supported flames.
Marine Gas Turbine Propulsion System Controls: An Integrated Approach
Authors: McMurry Joseph H. , Keefer Thomas B. , Previsani Lorenzo
Published: August 2009

A typical marine gas turbine propulsion system installation consists of separate controls for not only the gas turbine but also the ship systems, reduction gearbox, water jet and exhaust system. Advantages in reduced complexity, lower weight, ease of installation/maintenance and reduced cost of ownership can be achieved by minimizing the quantity of individual subsystem controls. An integrated gas turbine control (ITC) panel has been successfully designed, developed, installed, commissioned and delivered to a private luxury yacht owner over a 12-month period. The design and development phase of the project brought together a multi-discipline team of engineers to establish the requirements for the ITC. A development ITC was fabricated and tested to evaluate the system performance that included offline simulation in addition to actual gas turbine engine performance testing in a test cell. A key design feature of the ITC is the utilization of commercial off-the-shelf (COTS) hardware for the major control system components. This is in contrast to the typical non-integrated control systems used in past gas turbine control applications which utilized a purpose built, embedded processor system architecture. The use of COTS hardware in this design provides for literally millions of hours of operating experience of the equipment design even in advance of the initial simulation and evaluation testing. It also lends itself to ease of field troubleshooting and subcomponent replacement with readily available hardware. Accommodation for unforeseen system modifications were readily achieved through the ease of programming modifications. This paper describes in detail the conception, design, development, evaluation, testing and installation of the aforementioned ITC.
Simulation of Inlet Fogging and Wet-Compression in a Single Stage Compressor Including Erosion Analysis
Authors: Khan Jobaidur R. , Wang Ting
Published: August 2009

Gas turbine inlet fog / overspray cooling is considered as a simple and effective method to increase power output. To help understand the water mist transport in the compressor flow passage, this study conducts a computational simulation of wet compression in a single rotor-stator compressor stage using the commercial code, Fluent. A sliding mesh scheme is used to simulate the stator-rotor interaction in a rotating frame. The effect of different heat transfer models and forces (e.g. drags, thermophoretic, Brownian, Saffman’s lift force etc.) are investigated. Models to simulate droplet breakup and coalescence are incorporated to take into consideration the effect of local acceleration and deceleration on water droplet dynamics. Analysis on droplet history (trajectory and size) with stochastic tracking is employed to interpret the mechanism of droplet dynamics under influence of local turbulence, acceleration, diffusion, and body forces. An erosion model is also included. The results show that droplet local slip velocity is noticeably affected by local acceleration and deceleration of the compressor blade, and in turn, the heat transfer and water evaporation rate are affected. Due to the short droplet residence time in the compressor stage, local thermal equilibrium is not always achieved, and the air may not always reach saturation even sufficient amount of liquid mass is in the air. The results also show erosion occurs near the rotor fore-body on the suction side with the present erosion model, which is subject to continuous improvement and further verification. The transient results of different rotor/stator relative positions show low airflow blockage produces more effective compression and higher temperature rise. Different types of droplet boundary conditions show the effect is negligible.
Novel Cycles Deployment Study for a Silent Aircraft
Authors: Nettis L. , De Bellis F. , Javed A. , Doulgeris G. , Ogaji S. O. T. , Pilidis P.
Published: August 2009

Aircraft noise is nowadays considered a pollutant like exhaust gases. Moreover, future requirements for aircraft certification impose a remarkable reduction in noise emission in the next 20 years. Since current technologies are insufficient to achieve the target, new technologies have to be developed, both for engines and airframes. In this paper, three novel engine cycles have been studied from a preliminary and theoretical point of view, considering noise and fuel consumption reduction as key design drivers. The innovative cycles analysed are: Variable Fan Nozzle Area (VFNA), Constant Volume Combustor (CVC) and Inter Cooled Recuperated (ICR). A parametric analysis has been performed for each one of them in order to select the best cycle; then, the three optimums have been compared. The designed VFNA engine provides the largest reduction in jet noise (64%) in comparison to the baseline, whilst the CVC has the lowest fuel consumption. However, both use two fans per engine, with weight and drag penalties. A further noise reduction is obtained installing the engines upon the wings, and not beneath them as in conventional designs. Obtained results show that noise shielding technique is responsible for a 20 dB decrease in OASPL, leading to a noise level, perceived on the ground, lower than 60 dB. This value implies a full satisfaction of the new environmental laws. Finally, the three propulsion systems have been installed on a medium range, twin engine aircraft and its flight performance has been evaluated. Simulations establish the superiority of the novel cycles against the baseline, in terms of reduced fuel consumption for the given mission.
Fuel Flexibility of the Alstom GT13E2 Medium Sized Gas Turbine
Authors: Do¨bbeling Klaus , Meeuwissen Thiemo , Zajadatz Martin , Flohr Peter
Published: August 2009

Today’s power generation markets require considerable flexibility in terms of type and quality of fuels. However, this must be with low emissions, high reliability and high efficiency. In more than 100 installations worldwide the Alstom GT13E2 is in use with a wide variety of fuels. Fuel flexibility is the ability to burn natural gas fuels with a wide Wobbe index range which also allows the use of fuel preheaters (to increase efficiency) as well as the ability to use fuel oil as back up or main fuel. The paper will show the allowable Wobbe index range and higher hydrocarbon effects on gas turbine combustion and the field experience gained. Specific design features implemented in the GT13E2 ensure reliable and environmental friendly operation with varying fuels. Those are: 1.) an almost entirely convectively cooled combustor with only a small amount of film cooling. 2.) the use of premix burners which are stabilized by an aerodynamically induced recirculation at the centerline and a separately controlled pilot fuel injection. 3.) an adaptive fuel staging that monitors the flame stability by pulsation measurements and adjusts the fuel staging in the combustor such that the flame is always stable but not overly rich. This results in better NOx control under varying operating conditions due to the closed-loop controlled flame stability.
Numerical Investigation on the Second Stator Boundary Layer Under Clocking Effects: Comparison of v2f and LCL-Model
Authors: Heidecke Axel , Stoffel Bernd
Published: August 2009

This paper presents the results of a numerical investigation of a 1.5-stage low pressure turbine. The main focus of the numerical work was the prediction of the stator-2 boundary layer development under the influence of the stator stator clocking. The turbine profile used for the examination is a so called high-lift-profile and was designed for a laminar-turbulent transition over a steady separation bubble. The boundary conditions were defined by the 1.5-stage test turbine located at our laboratory, where also the measurement data was derived from. The calculations were conducted with a two-dimensional Navier-Stokes solver using a finite volume discretisation scheme. The higher level turbulence models v′2-f and the LCL-turbulence model, which are capable to predict boundary layer transition were compared with measurement data at midspan.
On the Individual and Combined Effects of Intentional Mistuning, Coupling and Damping on the Forced Response of Bladed Disks
Authors: Yu Changbo , Wang Jianjun , Li Qihan
Published: August 2009

Random mistuning always exists in bladed disk structures. The maximum blade forced response amplitudes are often much larger than those of their perfectly tuned counterparts, which leads to eventual failure via high cycle fatigue (HCF). Therefore, it is of great importance to predict and, ultimately, to reduce the blade forced response levels as a result of random mistuning. In this paper, intentional mistuning is introduced into a simplified 12-bladed disk model by varying the stiffness of the blades in periodic harmonic patterns. The individual and combined effects of intentional mistuning, coupling and damping are examined in the absence and presence of random mistuning through numerical study. It is found that there is some threshold value of intentional mistuning and coupling that leads to maximum mistuning effects and certain relations among intentional mistuning strength, integer harmonics, coupling and damping can suppress the response levels of mistuned bladed disks, which provides useful guidelines for safe and reliable designs of bladed disk systems.
Some Effects of Non-Axisymmetric End Wall Profiling on Axial Flow Compressor Aerodynamics: Part I—Linear Cascade Investigation
Authors: Harvey N. W.
Published: August 2009

Non-axisymmetric end wall profiling is now a well established design methodology in axial flow turbines, used principally to improve their aerodynamic efficiency by reducing secondary loss. However, profiled end walls (PEWs) have yet to find an in-service application in a gas turbine compressor. This two-part paper presents the results of a number of studies, both experimental and computational, into the potential aerodynamic benefits of applying PEWs in axial flow compressors. The first paper reports research carried out using a linear compressor stator cascade at Cambridge University. The datum geometry was based on previous research with this cascade. The PEW geometry was generated using a method that had been proven to reduce secondary loss in turbine blade rows. Data was taken on the datum and PEW geometries in the form of exit area traverses and surface static pressure measurements. The experiments demonstrated improvements to the exit flow field in terms of local reductions in the loss and under-turning in the secondary flow region due to the PEW. It was found that the original design method had over estimated the benefits of the PEW. The datum and PEW geometries were further analysed using state-of-the-art CFD (Computational Fluid Dynamics). The CFD is shown to achieve very good agreement with measurement at the design condition and a reasonable, qualitative match at off-design. It is concluded that the PEW geometry, though not optimum, effected predictable changes to the compressor stator flow field. The mechanisms for these effects are discussed and conclusions are drawn for taking the work forward. In particular, a mechanism is identified whereby the PEW enhances the cross-flow on the end wall and the subsequent radial migration of the secondary flow adjacent to the aerofoil suction surface. The control of corner stall by means of this flow mechanism is highlighted as a possible area for further investigation. This is followed up in the second paper, which presents a computational study of applying PEWs to a multi-stage HP compressor.
The Unsteady Loss in One-Stage Transonic Compressor Under Peak Efficiency and Near Stall Conditions
Authors: Sun Yutao , Ren Yu-Xin , Fu Song , Wadia Aspi R.
Published: August 2009

The loss mechanism due to the blade row interaction effects in a compressor is an important and interesting problem. In the present paper, the loss in a compressor stage under both peak efficiency (PE) and near stall (NS) operating conditions is studied numerically by solving the 3D unsteady RANS equations. The loss is measured in terms of the thermodynamic irreversibility. In order to examine the relationship between loss and flow structures, an intensive parameter called the intensity of irreversibility is derived. The relative importance of various flow structures in loss production has been identified by the orders of the intensity of irreversibility. An audit of the irreversibility has been carried out, which shows the importance of suction surface boundary layers and the tip leakages in loss generation. Under the NS conditions, the tip leakages are the most important sources of loss production. The unsteady evolution of irreversibility in the rotor and stator passage is also analyzed.
Experimental Study of Advanced Convective Cooling Techniques for Combustor Liners
Authors: Maurer Michael , Ruedel Uwe , Gritsch Michael , von Wolfersdorf Jens
Published: August 2009

An experimental study was conducted to determine the heat transfer performance of advanced convective cooling techniques at the typical conditions found in a backside cooled combustion chamber. For these internal cooling channels, the Reynolds number is usually found to be above the Reynolds number range covered by available databases in the open literature. As possible candidates for an improved convective cooling configuration in terms of heat transfer augmentation and acceptable pressure drops, W-shaped and WW-shaped ribs were considered for channels with a rectangular cross section. Additionally, uniformly distributed hemispheres were investigated. Here, four different roughness spacings were studied to identify the influence on friction factors and the heat transfer enhancement. The ribs and the hemispheres were placed on one channel wall only. Pressure losses and heat transfer enhancement data for all test cases are reported. To resolve the heat transfer coefficient, a transient thermocromic liquid crystal technique was applied. Additionally, the area-averaged heat transfer coefficient on the W-shaped rib itself was observed using the so-called lumped-heat capacitance method. To gain insight into the flow field and to reveal the important flow field structures, numerical computations were conducted with the commercial code FLUENT™.