bluuebunny/crossref_metadata_2025 huggingface dataset:
Emissions Characteristics of a Legacy Military Aircraft
Authors: Corporan Edwin , DeWitt Matthew J. , Klingshirn Christopher D. , Mahurin Shannon M. , Cheng Meng-Dawn
Published: February 2010

Emissions from aircraft and associated ground equipment are major sources of local pollution at airports and military bases. These pollutant emissions, especially particulate matter (PM), have been receiving significant attention lately due to their proven harmful health and environmental effects. As the U.S. Environmental Protection Agency (EPA) tightens environmental standards, it is likely that military operations, including the basing of advanced and legacy aircraft, will be impacted. Accurate determination of emission indices from aircraft is necessary to properly assess their environmental burden. As such, the gaseous and PM emissions of a B-52 Stratofortress aircraft were characterized in this effort. This emissions study supports the Strategic Environmental Research and Development Program (SERDP) project WP-1401 to determine emissions factors from military aircraft. The main purpose of the project is to develop a comprehensive emissions measurement program using both conventional and advanced techniques to determine emissions factors for pollutants of fixed and rotating wing military aircraft. Standard practices for the measurement of gaseous emissions from aircraft have been well established; however, there is no certified methodology for the measurement of aircraft PM emissions. In this study, several conventional aerosol instruments were employed to physically characterize the PM emissions from two of the aircraft’s TF33 turbofan engines. Exit plane pollutant emissions were extracted via probes and transported through heated lines to the analytical instruments. Particle concentrations, size distributions and mass emissions, as well as engine smoke numbers (SN), soot volatile fraction and total hydrocarbon emissions were measured. The engines were tested at four power settings, from idle to 75% normal rated thrust (NRT) (95% N2 – turbine speed). Test results show relatively consistent PM and gaseous emissions between the two engines for most conditions tested. The measured TF33 PM mass emission indices (EI), including estimated sampling line losses, were in the range of 1.0–3.0 g/kg-fuel and the particle number (PN) EI were between 4.0–10.0E+15 particles/kg-fuel. The particle size data followed a single mode lognormal distribution for all power settings with particle geometric mean diameters ranging from 52 to 85 nm. In general, the aerosol instrumentation provided consistent and reliable measurements throughout the test campaign, therefore increasing confidence on their use for turbine engine PM emissions measurements.
Real-Time Monitoring of the Weld Penetration State in Laser Welding of High-Strength Steels by Airborne Acoustic Signal
Authors: Huang Wei , Yang Shanglu , Lin Dechao , Kovacevic Radovan
Published: February 2010

Nowadays high-strength steels have great applications in different industries due to their good combination of formability, weldability, and high strength-to-weight ratio. To guarantee a high quality without the presence of defects such as partial penetration (PP) in the laser welding of high-strength steels, it is very important to on-line monitor the whole welding process. While optical sensors are widely applied to monitor the laser welding process, we are proposing to use a microphone to acquire the airborne acoustic signals produced during laser welding of high-strength steel DP980. In order to extract valuable information from a very noisy signal acquired in a harsh environment such as industrial welding, spectral subtraction (SS), a noise reduction method is used to process the acquired airborne sound signals. Furthermore, by applying the power spectrum density (PSD) estimation method, the frequency characteristics of the acoustic signals are analyzed as well. The results indicate that the welds in full penetration (FP) and PP produce different signatures of acoustic signals that are characterized with different sound pressure levels and frequency distributions ranging from 500 Hz to 1500 Hz. Based on these differences, two algorithms are developed to distinguish the FP from PP during the laser welding process. A real-time monitoring system is implemented by a LabVIEW-based graphic program developed in this research. A feedback control system that could guarantee the FP will be developed in the near future.
Effect of Thermal and Mechanical Loads on the Centrifugal Impeller Deformation and Its Structure Optimization
Authors: Wang Hong-liang , Xi Guang
Published: February 2010

Micro gas turbines are becoming popular for the distributed electric generator and propulsion system of small air vehicles. The centrifugal compressor impeller is an important component in the micro gas turbine and its aerodynamic performance and structural reliability have great effects on the system. This paper studied the impeller deformation caused by the thermal load (temperature variation) and mechanical loads (aerodynamic pressure and centrifugal force) and its influence on the impeller aerodynamic performance. Combined computational fluid dynamics (CFD) flow analysis and finite element method (FEM) structure analysis, using the fluid-solid and heat-solid interaction technology, the aerodynamic and temperature effects were transferred on the solid blade surfaces as loads to analyze the strain and stress of the centrifugal blade. The working blade profile was achieved by calculating the deformation magnitude of the solid grid nodes. The research showed that the largest deformation occurred at the blade inducer tip and the variation of tip clearance caused by blade deformation brought some influence not only on the aerodynamic performance but also on the structure reliability of the impeller. In order to reduce the impeller deformation under working condition, the hub section profile of the impeller was redesigned by an optimization method.
Investigation of Trailing Edge Cooling Concepts in a High Pressure Turbine Cascade: Aerodynamic Experiments and Loss Analysis
Authors: Rehder Hans-Ju¨rgen
Published: February 2010

As part of a European research project, the aerodynamic and thermodynamic performance of a high pressure turbine cascade with different trailing edge cooling configurations was investigated in the wind tunnel for linear cascades at DLR in Go¨ttingen. A transonic rotor profile with a relative thick trailing edge was chosen for the experiments. Three trailing edge cooling configurations were applied, first central trailing edge ejection, second a trailing edge shape with a pressure side cut-back and slot equipped with a diffuser rib array, and third pressure side film cooling through a row of cylindrical holes. For comparison aerodynamic investigations on a reference cascade with solid blades (no cooling holes or slots) were performed. The experiments covered the subsonic, transonic and supersonic exit Mach number range of the cascade while varying cooling mass flow ratios up to 2%. This paper analyzes the effect of coolant ejection on the airfoil losses. Emphasis was given on separating the different loss contributions due to shocks, pressure and suction side boundary layer, trailing edge and mixing of the coolant flow. Employed measurement techniques are schlieren visualization, blade surface pressure measurements and traverses by pneumatic probes in the cascade exit flow field and around the trailing edge. The results show that central trailing edge ejection significantly reduces the mixing losses and therefore decreases the overall loss. Higher loss levels are obtained when applying the configurations with pressure side blowing. In particular the cut-back geometry reveals strong mixing losses due to the low momentum coolant fluid which is decelerated by the diffuser rib array inside the slot. The influence of coolant flow rate on the trailing edge loss is tremendous, too. Shock and boundary layer losses are major contributions to the overall loss but are less affected by the coolant. Finally a parameter variation changing the temperature ratio of coolant to main flow was performed, resulting in increasing losses with decreasing coolant temperature.
Gas Turbine Testing During US Navy Trials for LHD-8 USS Makin Island
Authors: Buonamici Gianfranco P. , Boughner Abe L.
Published: February 2010

The Navy’s newest and last WASP class Amphibious Assault Ship, LHD 8 USS MAKIN ISLAND, is undergoing sea testing for the first time November 2008 before an expected delivery to the US Navy in early 2009. Rather than the two steam propulsion plants used by other ships in the WASP class, LHD 8 utilizes a gas turbine/electric drive hybrid propulsion system developing a combined 70,000 horsepower that will drive the 42,800-ton ship to speeds in excess of 20 knots. The paper will discuss the testing used to prepare the LM2500+ installation on LHD 8, the first of its kind in a military application, for entry into service. This will include details on engine light-off and the testing performed both dockside and at-sea. The paper will discuss the results of the at-sea test data as it compares to the initial predictions used to provide the rationale for funding the ship’s construction project.
Film Cooling Characteristic of Double-Fan-Shaped Film Cooling Holes
Authors: Bai Jiang-Tao , Zhu Hui-ren , Liu Cun-liang
Published: February 2010

The film cooling performance downstream of a single row of double-fan-shaped film cooling holes in a flat plate have been investigated by experimental measurements and numerical simulation. The entrance and exit of double-fan-shaped holes are comprised of a lateral expansion of 15° from the original simple cylindrical shape with stream-wise inclination of 45°. The width of the exit face to cylinder diameter ratio is 1.5; the length-to-diameter ratio is 4.24 and the pitch-to-diameter ratio is 3. The experimental method used to obtain the adiabatic film cooling effectiveness values and the heat transfer coefficient is a transient narrow band liquid crystal technique. Both film cooling effectiveness and heat transfer coefficient are measured at three momentum ratios (I = 0.5, 1, 2) at constant Reynolds number (Re = 10000) and free stream turbulence (Tu = 2%). The film cooling effectiveness, heat transfer coefficient and Net Heat Flux Reduction (NHFR) are presented for detailed distribution and span-wise averaged values. Discharge coefficients are also measured in the experiment. A commercial package is used to numerically simulate the flow and heat transfer of double-fan-shaped holes; simple cylindrical holes are also simulated for comparison. Numerical simulation use RNG turbulence model with a standard wall function for near wall region. Experimental and Numerical simulation results show that: 1) the double-fan-shaped holes present higher discharge coefficient than simple cylindrical holes at respective momentum ratio; 2) the numerical simulation film cooling effectiveness results of double-fan-shaped holes accord well with the experimental results; 3) at measured three momentum ratios, the double-fan-shaped holes demonstrate better film cooling performance (higher NHFR) than simple cylindrical holes, better film cooling expansion on span-wise; 4) the best momentum ratio of double-fan-shaped holes is 0.5.
Single-Stage High-Pressure Turbocharging
Authors: Gwehenberger Tobias , Thiele Martin , Seiler Martin , Robinson Douglas
Published: February 2010

To meet the ever-increasing demands that will be made on engines, and especially on planned new engine generations, in the future, the power density of their turbochargers will have to be significantly increased. Raising the brake mean effective pressure, introducing Miller timing and providing support for exhaust-gas treatment all presuppose an increase in the turbo’s compressor pressure ratio while keeping the turbo unit as compact as possible. To fulfill all of these conditions with single-stage turbocharging, a new approach to future turbocharger design is needed, especially when additional expensive materials, such as titanium, are not to be used. On the compressor side, when using proven aluminum compressors, this requires additional cooling of the compressor wheels. But other turbocharger components too, such as the turbine, bearings, shaft seals and also the casings and their connections, are exposed to higher thermal and mechanical stresses as a result of the pressure ratios being far higher than those of turbochargers currently on the market. The challenge, which could also be called a balancing act, in dimensioning new turbochargers for single-stage high-pressure turbocharging with aluminum compressors is to design the components with the help of the available tools such that sufficient safety and component lifetime are achieved while performance and component efficiency are optimized. By using the available calculation tools, such as FEM or for the fluid dynamics CFD, it is now possible to achieve compressor pressure ratios of up to 5.8 in continuous operation with single-stage turbocharging while ensuring a compact turbocharger design and aluminum compressors. The paper describes how ABB Turbo Systems Ltd has successfully developed and qualified a new single-stage high-pressure turbocharger generation with radial turbine which allows compressor pressure ratios of up to 5.8 in continuous operation at 100% engine load. First successful engine tests with the new A100 radial turbocharger generation have been carried out both on medium- and on high-speed engines. The first frame sizes of the new A100 high-pressure turbocharger series have been released for market introduction, setting a significant new benchmark for turbocharging advanced diesel and gas engines.
Determination of a Local Bulk Temperature Based Heat Transfer Coefficient for the Wetted Surfaces in a Single Inline Row Impingement Channel
Authors: Ricklick Mark , Kapat J. S.
Published: February 2010

High performance turbine airfoils are typically cooled with a combination of internal cooling channels and impingement. In such applications, the jets impinge against a target surface, and then exit along the channel formed by the jet plate, target plate, and side walls. Local convection coefficients are the result of both the jet impact, as well as the channel flow produced from the exiting jets. Numerous studies have explored the effects of jet array and channel configurations on both target and jet plate heat transfer coefficients. However, most current studies use the plenum temperature as the reference temperature in heat transfer calculations. This presents some difficulty to designers who need to determine heat transfer rates based on the local bulk temperatures. This paper examines three different methods to determining the local bulk temperature in a steady state impingement channel heat transfer experiment. The various methods will be compared based on their ease of application as well as their accuracy in describing the results. One method proves to be the most accurate, while another proves to be more easily implemented. The methods are compared for a single case previously studied, on a 15 hole, single row impingement channel, with dimensions of X/D = 5, Y/D = 4, Z/D = 1 & 3 and an average jet based Reynolds number of 17,000 and 45,000. Effects due to the choice of the reference temperature in heat transfer calculations are shown to cause significant variations in the calculated heat transfer coefficients. These results point to a transition between different flow regimes in the post-impingement flow.
A Study of Mesh-Fed Slot Film Cooling
Authors: Bunker R. S.
Published: February 2010

This investigation demonstrates the potential improvement in adiabatic film effectiveness that can be achieved through the use of mesh-fed surface slot film cooling. Mesh, or in-wall network, cooling is composed of fairly compact arrays of pedestals sized to fit within the limited wall thickness of a turbine airfoil. When the coolant discharge from such a mesh is along a shallow ramp to the airfoil aerodynamic surface (ie. like an angled film hole), the resulting film effectiveness from this combined geometry can be very high. The in-wall mesh network acts as the structural means for obtaining the slot geometry. In this study, flat plate warm wind tunnel testing has been conducted on two mesh-fed film geometries and compared against data for a row of axial round film holes, as well as a row of shaped diffuser film holes. The mesh-fed geometries are composed of pedestal arrays with height-to-diameter ratios of 0.2 exiting onto 20-degree inclines to the surface. The mesh slot exit film blowing ratios tested ranged from M = 0.1 to 0.7, while round and shaped film hole conditions covered 0.5 to 1.2. The mesh-fed film effectiveness results indicate a performance greater than that of shaped diffuser holes, but less than that of a more idealistic two-dimensional slot film geometry. The mesh-fed film effectiveness was as much as 25% higher than that for shaped holes in the near-hole region of x/Ms < 50, and up to 100% greater in the downstream region of x/ms > 50.
An Experimental Study of Transitional Flow Friction and Heat Transfer Performance of a Channel With Staggered Arrays of Mini-Scale Short Pin Fins
Authors: Rao Yu , Wan Chaoyi , Zang Shusheng
Published: February 2010

An experimental study was conducted to investigate the friction and heat transfer performance of air transitional flow in a rectangular channel with staggered arrays of short pin fins with transverse spacing-to-diameter of 1.5 and streamwise spacing-to-diameter ratio of 2.5. The friction factor, averaged Nusselt number and the overall thermal performance of the transitional flow have been obtained, and compared with Metzger’s pin fin channel with transverse spacing-to-diameter of 2.5 and streamwise spacing-to-diameter ratio of 2.5. The experimental study has showed that in the Reynolds number range of 1678–8500, the pin fin channel with transverse spacing-to-diameter of 1.5 has a higher convective heat transfer performance, but the enhancement capability decreases with the Reynolds number. For Re <6000, the overall thermal performance of the pin fin channel with transverse spacing-to-diameter of 1.5 is higher than the pin fin channel transverse spacing-to-diameter of 2.5, however for Re >6000 the overall thermal performance of the former is lower than the latter. For both of the pin fin channels, the overall thermal performance gets highest when the flow transition occurs.
Different Condition Monitoring Models for Gas Turbines by Means of Artificial Neural Networks
Authors: Palme´ Thomas , Fast Magnus , Assadi Mohsen , Pike Andrew , Breuhaus Peter
Published: February 2010

This paper presents three different gas turbine condition monitoring models developed by artificial neural networks. Operational data from an ALSTOM GT11-N1 has been employed for training and evaluation of the artificial neural network models. The developed models differ by their selected input and output parameters. These ANN models are used for prediction of performance parameters of the gas turbine. When tested on data collected after a training period, the models reveal different degradation trends, i.e. difference between expected and measured performance parameter values. The approach adopted in this paper shows that powerful monitoring tools can be developed form operational data with artificial neural networks.
Experimental and Numerical Investigation of Convective Heat Transfer in a Gas Turbine Can Combustor
Authors: Patil Sunil , Abraham Santosh , Tafti Danesh , Ekkad Srinath , Kim Yong , Dutta Partha , Moon Hee-Koo , Srinivasan Ram
Published: February 2010

Experiments and numerical computations are performed to investigate the convective heat transfer characteristics of a gas turbine can combustor under cold flow conditions in a Reynolds number range between 50,000 and 500,000 with a characteristic swirl number of 0.7. It is observed that the flow field in the combustor is characterized by an expanding swirling flow which impinges on the liner wall close to the inlet of the combustor. The impinging shear layer is responsible for the peak location of heat transfer augmentation. It is observed that as Reynolds number increases from 50,000 to 500,000, the peak heat transfer augmentation ratio (compared to fully-developed pipe flow) reduces from 10.5 to 2.75. This is attributed to the reduction in normalized turbulent kinetic energy in the impinging shear layer which is strongly dependent on the swirl number that remains constant at 0.7 with Reynolds number. Additionally, the peak location does not change with Reynolds number since the flow structure in the combustor is also a function of the swirl number. The size of the corner recirculation zone near the combustor liner remains the same for all Reynolds numbers and hence the location of shear layer impingement and peak augmentation does not change.
LAFAD Hard Ceramic and Cermet Coatings for Erosion Protection of Turbomachinery Components
Authors: Gorokhovsky Vladimir , Bowman Chris , Wallace John , VanVorous Dave , O’Keefe John , Champagne Victor , Pepi Marc , Tabakoff Widen
Published: February 2010

To mitigate costly surface damage, compressor blades are coated with materials that resist corrosion and resist wear from particle impact. Large Area Filtered Arc Deposition (LAFAD) technology has demonstrated the capability of depositing relatively thick cermet coatings with microlaminated architectures forming a stack of metallic/ceramic bi-layers. These coatings have nearly defect-free morphology and an extremely smooth surface with high surface energy, which improves the aerodynamics of airfoils. Yet, the deposition process can be carried out at a speed that produces coatings sufficiently thick to provide long life protection from particle damage at a cost-effective production rate. The basic mechanical properties and erosion resistance of LAFAD microlaminated cermet coatings deposited on Ti6Al4V and 17-4PH steel substrates have been investigated as a function of coating composition and architecture.
Development of a Micro Gas Turbine Combustion System for Fuel Oil: CFD-Lay-Out and Combustion Tests
Authors: Schmitz I. , Scherer V.
Published: February 2010

The current paper presents the development of a lean premixed prevaporized (LPP) combustion system for a micro gas turbine. A commercial spill return atomizer and a standard fuel oil pump as used in domestic burner applications were specified for the fuel supply system. The relatively large droplet sizes generated by this kind of atomizer system require careful design of the evaporation section of the combustion system. The usage of a LPP combustion concept implies the risk of self ignition and flash back. To avoid both, the knowledge of the ignition delay time and the flame speed of fuel oil are essential for the design of the combustion system. The paper describes the development process of the combustion system and presents experimental results for different geometries and operation conditions.
High Rotation Number Effects on Heat Transfer in a Rectangular (AR=2:1) Two Pass Channel
Authors: Huh Michael , Lei Jiang , Liu Yao-Hsien , Han Je-Chin
Published: February 2010

This paper experimentally investigated the rotational effects on heat transfer in a smooth two-pass rectangular channel (AR=2:1), which is applicable to the cooling passages in the mid portion of the gas turbine blade. The test channel has radially outward flow in the first passage and radially inward flow in the second passage after a 180° sharp turn. In the first passage, the flow is developing and heat transfer is increased compared to the fully developed case. Rotation slightly reduces the heat transfer on the leading surface and increases heat transfer on the trailing surface in the first pass. Heat transfer is highly increased by rotation in the turn portion of the first pass on both leading and trailing surfaces. Rotation increased heat transfer enhancement in the tip region up to a maximum Nu ratio (Nu/Nus) of 1.83. In the second passage, under rotating conditions, the leading surface experienced heat transfer enhancements above the stationary case while the trailing surface decreased. The current study has more than 4 times the range of the rotation number previously achieved for the 2:1 aspect ratio channel. The increased range of the rotation number and buoyancy parameter reached in this study are 0–0.45 and 0–0.8, respectively. The higher rotation number and buoyancy parameter have been correlated very well to predict the rotational heat transfer in the two-pass, 2:1 aspect ratio flow channel.
Challenges in Aero Gas Turbine Combustor Development
Authors: Maurya Dalton , Jayaprakash G. N. , Badarinath C.
Published: February 2010

The Hot End Technologies Directorate (HETD) of Gas Turbine Research Establishment (GTRE) has the mandate to design, development and delivery of airworthy combustor and afterburner modules for a military aero gas turbine engine. In order to meet the mandate, the directorate takes the overall responsibility of design to manufacture of the combustion systems. This paper addresses the challenges faced in the development of combustor module. A short annular combustor with air blast atomizer is incorporated in the engine and it is a very important equipment of a gas turbine engine, wherein the heat energy is added to get Turbine Inlet Temperature (TET). It comprises of a pre-diffuser, a dump diffuser, outer annulus, inner annulus and a flame tube. There has been a basic liner, which was used in earlier engines and there was a shortfall in terms of performance parameters — allowable profile and pattern factors. To improve the performance, in collaboration with the M/s Central Institute of Aviation Motors (CIAM), Moscow, Russia, the liner was redesigned [1]. The secondary holes were totally blocked, primary and dilution holes were altered and it was incorporated with a new dome with a modified curvature. A new air blast atomizer with a swirler having an outer and inner pintle was incorporated. The basic liner was incorporated with these modifications and making this dome out of the high temperature resistance nickel chromium alloy was challenging and it was realized. The liner assemblies incorporating all the welding details have been realized within the GTRE. The combustor system was tested for ground light up to 4.3 km. The light up time was of the order of 5 s. The pressure loss was of the order of 4.9% at a combustor inlet Mn of 0.30. The circumferential and radial pattern factor for the modified liner is of 0.36 and 0.14 respectively.
Hybrid RANS/LES Simulation of a Lean Premixed Swirl Burner Based on a Turbulent Flame Speed Closure
Authors: Ku¨nne Guido , Klewer Christian , Janicka Johannes
Published: February 2010

In this work, simulations of a strongly swirled premixed flame at atmospheric pressure were carried out using classical RANS-methods as well as different hybrid RANS/LES approaches. In the context of RANS, a large number of simulations using the k-ε-model were performed to study the impact of sensitivities related to boundary conditions and model parameters. For the transient simulations, the hybrid methods, DES (Detached Eddy Simulation) and SAS (Scale Adaptive Simulation) as implemented in ANSYS-CFX, were employed. These methods were used to avoid the prohibitive computational cost of LES in boundary layers but to resolve the detached eddies to capture the flame turbulence interaction. Combustion modeling in CFX is based on a transport equation for the progress variable combined with a turbulent flame speed closure to treat the chemical source term. In addition, isothermal LES was performed in advance to identify the coherent structures, such as precessing vortex cores, which were observed experimentally.
Application of Bayesian Forecasting to Change Detection and Prognosis of Gas Turbine Performance
Authors: Lipowsky Holger , Staudacher Stephan , Bauer Michael , Schmidt Klaus-Juergen
Published: February 2010

This paper presents a novel technique for automatic change detection of the performance of gas turbines. In addition to change detection the proposed technique has the ability to perform a prognosis of measurement values. The proposed technique is deemed to be new in the field of gas turbine monitoring and forms the basic building block of a patent pending filed by the authors [1]. The technique used is called Bayesian Forecasting and is applied to Dynamic Linear Models (DLMs). The idea of Bayesian Forecasting is based on Bayes’ Theorem, which enables the calculation of conditional probabilities. In combination with DLMs (which break down the chronological sequence of the observed parameter into mathematical components like value, gradient, etc.) Bayesian Forecasting can be used to calculate probability density functions prior to the next observation, so called forecast distributions. The change detection is carried out by comparing the current model with an alternative model which mean value is shifted by a prescribed offset. If the forecast distribution of the alternative model better fits the actual observation, a potential change is detected. To determine whether the respective observation is a single outlier or the first observation of a significant change, a special logic is developed. Studies have shown that a confident change detection is possible for a change height of only 1.5 times the standard deviation of the observed signal. In terms of prognostic abilities the proposed technique not only estimates the point of time of a potential limit exceedance of respective parameters, but also calculates confidence bounds as well as probability density and cumulative distribution functions for the prognosis.
The Effect of Element Thermal Conductivity on Turbulent Convective Heat Transfer From Rough Surfaces
Authors: McClain Stephen T. , Hodge B. Keith , Bons Jeffrey P.
Published: February 2010

The discrete-element model for flows over rough surfaces considers the heat transferred from a rough surface to be the sum of the heat convected from the flat surface and the heat convected from the individual roughness elements to the fluid. In previous discrete-element model development, heat transfer experiments were performed using metallic or high-thermal conductivity roughness elements. Many engineering applications, however, exhibit roughness with low thermal conductivities. In the present study, the discrete element model is adapted to consider the effects of finite thermal conductivity of roughness elements on turbulent convective heat transfer. Initially, the boundary-layer equations are solved while the fin equation is simultaneously integrated so that the full conjugate heat transfer problem is solved. However, a simpler approach using a fin-efficiency is also investigated. The results of the conjugate analysis and the simpler fin-efficiency analysis are compared to experimental measurements for turbulent flows over ordered cone surfaces. Possibilities for extending the fin-efficiency method to randomly-rough surfaces and the experimental measurements required are discussed.
Gas Turbines Fired With Biomass Pyrolysis Syngas: Analysis of the Overheating of Hot Gas Path Components
Authors: Colantoni Simone , Della Gatta Stefania , De Prosperis Roberto , Russo Alessandro , Fantozzi Francesco , Desideri Umberto
Published: February 2010

Alternative resources such as biomass, and municipal and industrial waste are being considered as a source for the production of syngas to replace natural gas as a power turbine fuel. Pyrolysis of biomass produces a syngas composed primarily of CO, CO2, CH4 and H2 with a medium-low lower heating value (LHV) that is strongly dependent on the process boundary conditions such as the pyrolysis temperature and product residence time in the reactor [1, 2]. The issues associated with conventional gas turbines also apply to syngas turbines with the added complexity of the fuel and impurities. At present, syngas turbines are operated at firing temperatures similar to those of turbines fired on natural gas by increasing the fuel mass flow through the turbine. While this produces a higher turbine power output, the heat transferred to the hot flow-path vanes and blades is also greater. The aim of this paper is to report on the use of numerical modeling to analyze the fundamental impact of firing gas turbines with biomass pyrolysis syngas. To complete the analysis, the results have been compared with data from the literature on gas turbines fired with coal gasification syngas. The test engine used to perform this analysis is a General Electric GE10-2 gas turbine. The performance, aerodynamics and secondary flows were computed using proprietary software, while commercial finite element software was used to perform the thermal and local creep analyses.
CFD Prediction for Multi-Jet Impingement Heat Transfer
Authors: Zu Y. Q. , Yan Y. Y. , Maltson J. D.
Published: February 2010

In this paper, the flow and heat transfer characteristics of two lines of staggered or inline round jets impinging on a flat plate are numerically analyzed using the CFD commercial code FLUENT. Firstly, the relative performance of seven versions of turbulence models, including the standard k-ε model, the renormalization group k-ε model, the realizable k-ε model, the standard k-ω model, the Shear-Stress Transport k-ω model, the Reynolds stress model and the Large Eddy Simulation model, for numerically predicting single jet impingement heat transfer is investigated by comparing the numerical results with available benchmark experimental data. As a result, the Shear-Stress Transport k-ω model is recommended as the best compromise between the computational cost and accuracy. Using the Shear-Stress Transport k-ω model, the impingement flow and heat transfer under multi-jets with different jet distributions and attack angles are simulated and studied. The effect of hole distribution and angle of attack, etc. on the heat transfer coefficient of the target plate are examined.
Optimization of a Fan-Shaped Hole for Film Cooling Using a Surrogate Model
Authors: Lee Ki-Don , Kim Kwang-Yong
Published: February 2010

A numerical procedure for shape optimization of a fan-shaped hole is presented to enhance film-cooling effectiveness by combining a three-dimensional Reynolds-averaged Navier-Stokes analysis with the radial neural network method, a well known surrogate modeling technique for optimization. The injection angle of the hole, lateral expansion angle of hole and ratio of length-to-diameter of the hole are chosen as design variables and spatially averaged film-cooling effectiveness is considered as an objective function which is to be maximized. Latin hypercube sampling is used to determine the training points as a mean of the design of experiment. Sequential quadratic programming is used to search for the optimal point from the constructed surrogate. The film-cooling effectiveness has been successfully improved by the optimization with increased values of all design variables as compared to the reference geometry.
An Experimental Investigation of a Single Stage Wet Gas Centrifugal Compressor
Authors: Fabbrizzi Michelangelo , Cerretelli Ciro , Del Medico Francesco , D’Orazio Maria
Published: February 2010

Wet Gas Compression technology for centrifugal compressors is without doubts one of the topics that have enjoyed a most rapidly growing interest in recent years [1]. This is certainly due to the new opportunities for exploiting aging gas fields, which are rendered possible by this technology. However, despite the numerous recent works on this topic, the fundamental understanding of wet gas compression processes remains challenging in the sense that no unified standards for testing and performance exist, and that the understanding of the basic physical phenomena is not fully complete. The present work is concerned with such issues and contributes experimental results and performance analysis for a low pressure-ratio centrifugal compressor stage in heavily wet gas streams. An open loop test rig was built for a single scale model centrifugal compressor to be run at typical design operating range. The impeller was a standard impeller with no design adjustments for wet streams. The performance was assessed at liquid mass fractions (LMF) ranging between 0% and 50% and at average droplet diameters between 50 μm and 75 μm, as well as non-atomized liquid streams. The results clearly demonstrate that wet gas strongly influences compressor performance, considering adsorbed power, efficiency and compressor characteristics. The results also show that, although the impeller design did not account for heavily wet streams, the overall compression characteristics remain good and the machine was able to process the two-phase mixture without failures, in some cases with improved pumping. The compressor exit temperatures of the gas phase in heavily wet conditions are key to assessing machine performance, in particular efficiency, for wet gas compression. Although an accurate technology approach for measuring such temperatures has not yet been developed, in the present work a droplet model is proposed. This model is then calibrated with experimental data in order to develop a methodology providing reliable efficiency values.
Combustion Dynamics Data Mining Techniques: A Way to Gain Enhanced Insight in the Combustion Processes of Fielded Gas Turbines
Authors: Laget Hannes , Deneve Michae¨l , Vanderhaegen Evert , Museur Thomas
Published: February 2010

Combustion dynamics are still an important challenge for the gas turbine operators. Modern dry low NOx combustors operate within very small tolerances of equivalence ratio, airfuel mixing and heat release rate in order to attain low NOx emissions and combustion stability. Small changes in fuel composition, or extremes in ambient temperature can trigger combustion instabilities. Large amounts of data of real engines are available to the end user. Moreover, instead of adaptations to the hardware, the end-user is primarily interested in the actual condition of its gas turbine. Although physical insight is without any doubt an important step to enhance knowledge of the processes within the combustion chamber, these large datasets can also be exploited with data-mining techniques based on black box models, such as artificial neural networks or decision trees. In this paper, the latter approach is discussed in detail and implemented on a F-class gas turbine. The operational and combustion data, acquired over a long period on the gas turbine, have been used as the input to a commercial data-mining program in order to study the correlations between the different operational parameters and the characteristic amplitude and frequency of the combustion dynamics. Moreover, the data-mining program allows the nonlinear modelling of the combustion dynamics, which in a second step has been used to carry out a parametric study. The parameters with a high influence, amongst others the gas quality, the compressor inlet temperature and the firing temperature, on the presence of combustion dynamics have been retained for modelling the behaviour of the combustion dynamics. The obtained models show good correspondence with operational experience and data gathered during gas turbine tuning operation. These models can thus be used to enhance the insight into the complex behaviour of combustion dynamics. They can be helpful for predictive maintenance and finally can be applied for the determination of tuning margins and the prevention of high combustion dynamics.
Effect of Hole Spacing on Deposition of Fine Coal Flyash Near Film Cooling Holes
Authors: Ai Weiguo , Murray Nathan , Fletcher Thomas H. , Harding Spencer , Bons Jeffrey P.
Published: February 2010

Particulate deposition experiments were performed in a turbine accelerated deposition facility to examine the nature of flyash deposits near film cooling holes. Deposition on both bare metal and TBC coupons was studied, with hole spacings (s/d) of 2.25, 3.375, and 4.5. Sub-bituminous coal ash particles (mass mean diameter of 13 microns) were accelerated to a combustor exit flow Mach number of 0.25 and heated to 1183°C before impinging on a target coupon. The particle loading in the 1-hr tests was 310 ppmw. Blowing ratios were varied in these experiments from 0 to 4.0 with the density ratio varied approximately from 1.5 to 2.1. Particle surface temperature maps were measured using two-color pyrometry based on the RGB signals from a camera. For similar hole spacing and blowing ratio, the capture efficiency measured for the TBC surface was much higher than for the bare metal coupon due to the increase of surface temperature. Deposits on the TBC coupon were observed to be more tenacious (i.e., hard to remove) than deposits on bare-metal coupons. The capture efficiency was shown to be a function of both the hole spacing and the blowing ratio (and hence surface temperature). Temperature seemed to be the dominant factor affecting deposition propensity. The average spanwise temperature downstream of the holes for close hole spacing was only slightly lower than for the large hole spacing. Roughness parameters Ra and Rt decreased monotonically with increased blowing ratio for both hole spacings analyzed. The roughness for s/d = 3.375 was lower than that for s/d = 4.5, especially at high blowing ratio. It is thought that these data will prove useful for designers of turbines using synfuels.
Development of Life Prediction Methodology for Thermal Barrier Coatings Based on Nondestructive Piezo-Spectroscopy Photoluminescence Measurements
Authors: Govindaraju Madhavrao , Rechoum Slimane , Sablik Martin J. , Cheruvu N. Sastry , Dryepondt S. , Sikorski Ruth L.
Published: February 2010

Durability of Thermal barrier coatings (TBCs) exposed to hot combustion environment is a major concern to the aerospace industry. Typical failure mechanism of electron beam physical vapor deposited (EBPVD) TBCs is separation or spallation of the ceramic top coat at the thermally grown oxide (TGO) layer. TBC spallation occurs when the residual stresses at the TBC-TGO bond coat approaches zero. The objective of the investigation was to develop an analytical approach to determine the remaining service life of TBC coated components using nondestructive photo-luminescence piezospectroscopy (PLPS) measurements. EBPVD coated samples were exposed to both isothermal and thermal cycling at three temperatures (1093°C, 1149°C, and 1204°C). Samples were removed at periodic intervals up to failure. The PLPS technique was used to measure the residual stresses at the interface of TBC-TGO. A model was developed for predicting the remaining life of TBC system based on the correlation between the residual stresses at the TBC-TGO interface and the shift in the TGO luminescence frequency. Remaining life prediction of the model was validated on samples thermally cycled at 1121°C. The predicted values of remaining life were compared with experimental data.
Thermoacoustic Modeling of a Gas Turbine Using Transfer Functions Measured at Full Engine Pressure
Authors: Schuermans Bruno , Guethe Felix , Pennel Douglas , Guyot Daniel , Paschereit Christian Oliver
Published: February 2010

Thermoacoustic transfer functions have been measured of a full-scale gas turbine burner operating at full engine pressure. Excitation of the high-pressure test facility was done using a siren that modulated part of the combustion airflow. Pulsation probes have been used to record the acoustic response of the system to this excitation. In addition, the flame’s luminescence response was measured by multiple photomultiplier tubes and a light spectrometer. Three techniques to obtain the thermoacoustic transfer function are proposed and employed: two combined acoustical-optical technique and a purely acoustic technique. The first acoustical-optical technique uses one single optical signal capturing the chemiluminescence intensity of the flame as a measure for the heat release in the flame. It only works, if heat release fluctuations in the flame have only one contribution, e.g. equivalence ratio or mass flow fluctuations. The second acoustic-optical acoustic-optical technique makes use of the different response of the flame’s luminescence at different optical wavelengths bands to acoustic excitation. It also works, if the heat release fluctuations have two contributions, e.g. equivalence ratio and mass flow fluctuation. For the purely acoustic technique, a new method was developed in order to obtain the flame transfer function, burner transfer function and flame source term from only three pressure transducer signals. The purely acoustic method could be validated by the results obtained from the acoustic-optical techniques. The acoustic and acoustic-optical methods have been compared and a discussion on the benefits and limitations of the methods is given. The measured transfer functions have been implemented into a non-linear, three-dimensional, time domain network model of a gas turbine with an annular combustion chamber. The predicted pulsation behavior shows a good agreement with pulsation measurements on a field gas turbine.
Torsional Vibrations in Rotordynamic Systems: Smart Investigation Methods
Authors: Rossi Valerio , Naldi Lorenzo , Depau Valerio
Published: February 2010

Nowadays more and more complex applications in the Oil & Gas industry, customer tailor made designs and electrification growth present new and tougher rotor dynamic challenges. As a consequence, in addition to lateral, also torsional vibrations need to be monitored and deeply investigated during string test and at site, to validate design or when unexpected issues occur. This paper describes the experiences achieved by the authors on the study and fulfillment of smart investigation methods for torsional vibration analysis at site, where measurements and diagnostics need to be carried out without affecting production and field operation. Several methods have been studied, tested and validated on simulators and on an internal test bench before being finally applied to site troubleshooting with the purpose of avoiding unit shut down, allowing on line monitoring and reducing costs. All studied investigation methods are presented in this paper with results, comparative analysis and an overview of the simulator and of the other systems tested. Possible future developments are described also. It is now possible to protect machineries against unexpected high torsional vibrations leveraging the standard instrumentation normally available for unit protection and monitoring.
Global Turbulent Consumption Speeds (ST,GC) Of H2/CO Blends
Authors: Venkateswaran Prabhakar , Marshall Andrew D. , Noble David R. , Antezana Jose , Seitzman Jerry M. , Lieuwen Tim C.
Published: February 2010

This paper describes measurements of the global turbulent consumption speed, ST,GC, of atmospheric pressure H2/CO flames at mean flow velocities and turbulence intensities up to U = 50 m/s and u′/SL = 100, respectively. The particular emphasis of the paper is to characterize H2/CO mixture properties upon turbulent flame speeds — a number of prior studies have noted that different fuels, with the same laminar flame speed and combusted in the same turbulent flow, can have widely different turbulent flame speeds. This effect is believed to be due to flame speed sensitivities to stretch and possibly thermo-diffusive instabilities. While this effect is widely known, little data are available for syngas blends. Turbulent flame speeds were obtained with blends ranging from 30–90% H2, with the mixture equivalence ratio, φ, adjusted at each fuel composition to have nominally the same laminar flame speed, SL. In addition, equivalence ratio sweeps at constant H2 level were also performed. The data clearly corroborate results from other studies that show significant sensitivity of ST,GC to fuel composition. In particular, at a fixed u′ and SL, values of ST,GC increase by almost a factor of 1.5–2 when H2 levels are increased from 30% (at φ = 0.59) to 90% (at φ = 0.46). Moreover, ST,GC in the 90% H2 case is 3 times larger than the φ = 0.9 CH4/air mixture with the same SL value. An important conclusion from this work is that fuel effects on ST,GC highlighted above are not simply a low turbulence intensity phenomenon — they clearly persist over the entire range of turbulence intensities used in the measurements.