bluuebunny/crossref_metadata_2025 huggingface dataset:
Friction Damping Modeling in High Stress Contact Areas Using Microslip Friction Model
Authors: Marquina Francisco J. , Coro Armando , Gutie´rrez Alberto , Alonso Roberto , Ewins David J. , Girini Giovanna
Published: August 2009

It is well known that friction is really important to reduce amplitudes of vibration of rotor blades. Underplatform dampers are a common solution for introducing friction damping, but there are also other friction damping sources on blades that are produced in places with high normal loads and small relative displacements (e.g. lockplates and blade-disc joints). Several approaches based on the classical Coulomb friction law have been used in order to model the friction damping at those interfaces, but their results are not accurate enough for those cases with small displacements where high normal loads appear. This paper presents simulations of typical cases of friction on rotor blades (underplatform dampers, lockplates and blade root) using a method based on macroslip and the method developed by ‘Industria de TurboPropulsores’ (ITP) based on microslip (InTerPart MIcroslip COntact method), and their comparison with experimental results obtained with several tests performed at Imperial College London (IC). The comparison shows that, for cases with high normal loads and small displacements, the ITPMICO method obtains further more accurate results than based-on-macroslip one.
Methods of Extrapolating Low Cycle Fatigue Data to High Stress Amplitudes
Authors: Radonovich David , Gordon Ali P.
Published: August 2009

Characterizing the low cycle fatigue (LCF) properties of each alloy used in a gas turbine is expensive and time consuming. As such, each material is typically characterized over only the necessary cyclic range to insure safe, reliable component design. If it is desired to understand properties outside of that range, the accepted procedure is to acquire additional LCF test data. The objective of this project is to test the validity of several extrapolation methods versus acquiring additional test data for a particular alloy. Several models are developed by the following techniques: a monotonic test data anchor point, a strain-compatibility derived anchor point, and temperature independence of the Coffin-Manson relation. Predictions are made using a base data set of Ni-base superalloy IN738 LC at several test temperatures. High stress amplitude data points are acquired, and incorporated into the base data set to form an augmented data set. The extrapolation methods are compared to the results from the augmented data set to test validity. The results show that the strain compatibility anchor point model has marginal improvement over extrapolation using the base data set, and the other two models had reduced accuracy relative to extrapolation using the base data set. Anomalies were found in the base test data set due to serrated yielding and oxidation. Two models offer improved fit to test data when used with data sets that contain anomalies. If this is a general trend, it offers potential that the models could be used to indicate anomalous behavior. It is not known whether the results of this study can be applied to other materials.
Damage Evolution and Failure Mechanisms for APS-TBCS
Authors: Cappuccini Filippo , Giovannetti Iacopo , Sanyal Suchismita , Giannozzi Massimo , Kumar Santosh , Shalini T. , Viswanath T.
Published: August 2009

Thermal barrier coatings (TBC-s) have been utilized in gas turbine engines for over two decades, primarily to protect the existing materials under the demands for higher temperatures and greater engine efficiency. Atmospheric Plasma Sprayed TBC, commonly used for hot combustion chamber components of advanced gas turbines, are exposed to thermo-mechanical loads, which may lead to failure in form of macroscopic spallations from the metallic component. The durability of TBC is limited by the interaction of different processes and parameters, such as bond coat oxidation, cyclic strains, visco-plastic and relaxation properties, interface roughness and others. In this work, the spallation failure mechanisms and damage evolution of APS-TBC system are investigated on samples aged by isothermal and thermal cycle tests using different time and temperatures exposures. Several parameters have been analyzed by SEM and a life prediction model approach for APS-TBC is being developed focusing on oxidation kinetics, identifying the parameters such as rumpling, bond coat oxidation, TGO thickness and interdiffusion of base metal elements which drive the oxide formation and TBC spallation mechanisms.
Design, Fabrication, and Performance of Foil Gas Thrust Bearings for Microturbomachinery Applications
Authors: Dykas Brian , Bruckner Robert , DellaCorte Christopher , Edmonds Brian , Prahl Joseph
Published: August 2009

A methodology for the design and construction of simple foil thrust bearings intended for parametric performance testing and low marginal costs is presented. Features drawn from a review of the open literature are discussed as they relate to bearing performance. The design of fixtures and tooling required to fabricate foil thrust bearings is presented, using conventional machining processes where possible. A prototype bearing with dimensions drawn from the literature is constructed, with all fabrication steps described. A load-deflection curve for the bearing is presented to illustrate structural stiffness characteristics. Start-stop cycles are performed on the bearing at a temperature of 425°C to demonstrate early-life wear patterns. A test of bearing load capacity demonstrates useful performance when compared with data obtained from the open literature.
Experimental Investigation Into the Influence of Varying Stagger on the Performance of a Pin-Fin Array
Authors: Allan W. D. , Andrews S. A. , LaViolette M.
Published: August 2009

A six row pin-fin array was constructed with a spanwise spacing of 2.5 diameters, streamwise spacing of 1.5 diameters and a height to diameter ratio of 1. The streamwise stagger of alternate rows was continuously varied from fully in-line to fully staggered. Tests were carried out at Reynolds numbers of 2.7 × 104 and 2.3 × 104, corresponding to maximum velocities, in the low subsonic range, of 21 m/s and 18 m/s respectively. These results showed that the array averaged heat transfer was greatest from a fully staggered array and had a minimum at a stagger slightly greater than fully in-line. However, with increasing stagger, the array-averaged friction factor grew at a greater rate than the heat transfer. The ensuing analysis of the total array performance, considering both the magnitude of heat transfer and the losses within the array, showed that the fully in-line array had the highest ratio of heat transfer enhancement to friction factor enhancement. Therefore, if pressure loss was a design criterion, the fully in-line array was preferable. However, if pressure loss was not a constraint, then the staggered array was preferable.
Analysis of Dynamic Characteristics of Gas Turbine Rotor Considering Contact Effects and Pre-Tightening Force
Authors: Yuan Qi , Gao Rui , Feng Zhenping , Wang Jianlu
Published: August 2009

Modern gas turbine rotors are usually designed as combined rotors in which disks are tied together by one central tie rod or several tie rods distributed along the circumference. This structure has the advantages in cooling design, light weight and processing assembly, however it brings some problems and challenges in predicting the dynamic characteristics of rotor. No matter how many tie rods are used to fasten the disks, the rotor is not an integral or continuous structure any more. The contact effects between contact faces and the pre-tightening forces of tie rods have great influence on the rotor’s dynamic behaviors. Traditional methods to calculate the critical speed in rotor dynamics such as Transfer Matrix Method and 2-D Finite Element Method (FEM), based on the integral and continuous rotor, fail to consider factors of the contact effects and the pre-tightening forces of tie rods. Although the 3-D FEM can exactly calculate the critical speed, it is still time and resource consuming to establish and calculate such complex three-dimensional structures, even on the most advanced computers at present. In this paper, the traditional 2-D FEM is improved by considering the contact effects and pre-tightening forces of tie rods. Contact faces in the rotor are dealt as elements with equivalent stiffness but without mass, thus the rotor-bearing system of gas turbine are composed of contact elements, elastic elements, rigid disk elements and bearing elements. According to the improved 2-D FEM, a program is developed to calculate the critical speed and unbalance response of gas turbine rotors. The equivalent stiffness, serving as an important input parameter in the program and elements in the stiffness matrix of the system, is mainly determined by the contact stiffness between contact faces and the pre-tightening force. To find out relationships between them, GW (Greenwood and Williamson) statistical model is used and the equivalent stiffness of complex contact faces is obtained. According to the results, certain curves showing the relationship between equivalent stiffness of contact surface and pre-tightening force are obtained. By these curves and the program, we can easily calculate the dynamic characteristics of gas turbine rotors with satisfying accuracy and less time. To validate this method, the critical speed of a real rotor of a certain gas turbine was calculated with the program and curves, and the results agree well with the measured data.
Numerical and Experimental Investigation of the Flow and Performance Characteristics of Twin-Entry Radial Turbine Under Full and Partial Admission Conditions
Authors: Shahhosseini M. R. , Hajilouy-Benisi A. , Rad M.
Published: August 2009

In this paper, numerical and experimental investigation of the performance and internal flow field characteristics of the twin-entry radial inflow turbine under full and partial admission conditions are presented. The turbine is tested on a turbocharger test facility, which was developed for small and medium size turbochargers. The flow pattern in the volute and impeller of a twin-entry turbine is analyzed using fully three-dimensional viscous program. The computational performance results are compared with the experimental results, and good agreement is found. The flow field at the outlet of the turbine is investigated using a five-hole pressure probe. The tests are performed for both full and partial admission conditions numerically and experimentally. In the volute, results show that highest entropy gain factor belongs to the shroud side at partial admission conditions. In the inlet of rotor, flow at the partial admission condition is more prone toward shroud side than full admission. Meanwhile, entropy distribution contours corresponding to the exit plane are considered, which show entropy gain factor pattern do not have appreciable difference at full and partial admission conditions, and minimum entropy gain factor exists at shroud side near the suction surface and at hub side near the pressure surface.
Investigations on the Discharge and Total Temperature Increase Characteristics of the Labyrinth Seals With Honeycomb and Smooth Lands
Authors: Yan Xin , Li Jun , Song Liming , Feng Zhenping
Published: August 2009

The viscous work generated by the rotating components of the seal not only represents the direct loss of power, but also causes the increase in total temperature of fluid (windage effect). In order to study the discharge and total temperature increase characteristics of the stepped labyrinth seals with smooth and honeycomb lands, 3D RANS solutions from CFX is used in this work. At first, the influences of the inlet preswirl, leakage flow rate and rotational speed on the total temperature increase in the convergent and divergent stepped labyrinth seals with smooth and honeycomb lands are conducted. The obtained 3D numerical results are well in agreement with the referenced experimental data. It shows that the utilized numerical approach has sufficient precision to predict the total temperature increase in seals. Then, a range of pressure ratios and four sizes of sealing clearance are performed to investigate the effects of sealing clearances and pressure ratios impact on the discharge and total temperature increase of the stepped labyrinth seals with honeycomb and smooth liners.
Dynamic Response of the Vertical Rotor System to Base Excitation
Authors: Zuo Jianli , Wu Jianjun , Li Ping , Su Shenjian
Published: August 2009

The physical model of a high-speed vertical rotating machine was taken as the example. The motion differential equations of the rotor system were established by the Lagrange equation and numerically solved by the Wilson-θ method. The whirling characteristics of the rotor excited by the base’s harmonic motions have been analyzed. The whirling directions are different between the rotor’s upper and lower ends. And the whirling characteristics of the rotor vary with the frequency of the base’s motion. Besides, there exists such a region of the rotor’s rotary speed, in which the whirling characteristics and amplitudes of the rotor system are relatively steady, so the aseismic tests at a certain lower speed can be done to examine the aseismic capability of the rotor system at operating speed.
A Compressible Flow Network Analysis for Design Upgrade of Industrial Aeroderivative High Pressure Turbine Blades
Authors: Jin H. , Riddle A. , Cooke L.
Published: August 2009

Industrial aeroderivative gas generators used to drive pipeline compressors had experienced significant scrap rates of high pressure turbine (HPT) blades due to oxidation on the aftmost row of film cooling holes at mid-airfoil on the pressure side. The oxidation attack resulted in a significant loss of base material and effective thickness, and eventually became the life limiting factor and a major decision point in determining the engine overhaul period. A quick comparison of the aeroderivative HPT blade with its aero-version design showed that the cooling air entering each aeroderivative HPT blade is restricted by a metering plate at the blade root. Using the aero-engine design as a baseline, a compressible flow network analysis (CFNA) was conducted to identify the root cause of the oxidation and develop design upgrades to extend the aeroderivative HPT blade life.
Simulation of Turbulent Lifted Flames Using a Partially-Premixed Coherent Flame Model (PCFM)
Authors: Zhang Yongzhe , Rawat Rajesh
Published: August 2009

Partially-premixed combustion occurs in many combustion devices of practical interest, such as gas-turbine combustors. Development of corresponding turbulent combustion models is important to improve the design of these systems in efforts to reduce fuel consumption and pollutant emissions. Turbulent lifted flames have been a canonical problem for testing models designed for partially-premixed turbulent combustion. In this paper we propose modifications to the coherent flame model (CFM) so that it can be brought to the simulation of partially-premixed combustion. For the primary premixed flame, a transport equation for flame area density is solved in which the wrinkling effects of the flame stretch and flame annihilation are considered. For the subsequent non-premixed zone, a laminar flamelet PPDF methodology, which accounts for the non-equilibrium and finiterate chemistry effects, is adopted. The model is validated against the experimental data on a lifted H2/N2 jet flame issuing into a vitiated coflow. In general there is fairly good agreement between the calculations and measurements both in profile shapes and peak values. Based on the simulation results the flame stabilization mechanism for lifted flames is investigated.
Study on Advanced Internal Cooling Technologies for the Development of Next-Generation Small-Class Aircraft Engines
Authors: Fujimoto Shu , Okita Yoji , Fukuyama Yoshitaka , Yamane Takashi , Mimura Fujio , Matsushita Masahiro , Yoshida Toyoaki
Published: August 2009

An innovative internal cooling structure named multi-slot cooling has been invented for high-pressure turbine (HPT) nozzles and blades. This cooling structure has been designed to be simple, inexpensive, and to exhibit good cooling performance. In order to confirm the cooling performance of this structure, test pieces of dummy turbine nozzles were manufactured. Three geometric parameters (width of slots, overall height of cooling channel, and height of jet impingement) are associated with these test pieces. The cooling performance tests were conducted by using these test pieces for several Reynolds numbers of the mainstream hot gas [2.2 × 105 – 3.4 × 105] and cooling airflow [3 × 103 – 1 × 104]. Infrared (IR) images of the heated surfaces of the test pieces were captured for every Reynolds number in the tests, and then the distributions of the cooling effectiveness were obtained. Simultaneously, the pressure losses were measured. This paper describes the hot gas flow tests performed to confirm the effects of the geometric parameters on the cooling performance and pressure loss, and to obtain data of Nusselt number and pressure loss coefficient for the design of turbine nozzles in the future by applying this new cooling structure to next-generation small-class aircraft engines. Additionally a preliminary analysis of airfoil cooling was performed to evaluate both cooling performance of conventional impingement cooling and multi-slot cooling in applying to a HPT nozzle, as a result it was found that the multi-slot cooling is well applicable to cooling of HPT airfoils.
Experimental Study on Impeller Blade Vibration During Resonance: Part 1—Blade Vibration Due to Inlet Flow Distortion
Authors: Kammerer Albert , Abhari Reza S.
Published: August 2009

Forming the first part of a two-part paper, the experimental approach to acquire resonant vibration data is presented here. Part 2 deals with the estimation of damping. During the design process of turbomachinery components, mechanical integrity has to be guaranteed with respect to high cycle fatigue of blades subject to forced response or flutter. This requires the determination of stress levels within the blade which in turn depend on the forcing function and damping. The vast majority of experimental research in this field has been performed on axial configurations for both compressors and turbines. This experimental study aims to gain insight into forced response vibration at resonance for a radial compressor. For this purpose a research impeller was instrumented with dynamic strain gauges and operated under resonant conditions. Modal properties were analysed using FEM and verified using an optical method termed Electronic-Speckle-Pattern-Correlation-Interferometry (ESPI). During the experiment, unsteady forces acting on the blades were generated by grid installations upstream of the impeller which created a distorted inlet flow pattern. The associated flow properties were measured using an aerodynamic probe. The resultant pressure fluctuations on the blade surface and the corresponding frequency content were assessed using unsteady CFD. The response of the blades was measured for three resonant crossings which could be distinguished by the excitation order and the natural frequency of the blades. Measurements were undertaken for a number of inlet pressure settings starting at near vacuum and then increasing. The overall results showed that the installed distortion screens generated harmonics in addition to the fundamental frequency. The resonant response of the first and second blade mode showed that the underlying dynamics support a single-degree-of-freedom model.
A Time-Domain Fluid-Structure Interaction Analysis of Fan Blades
Authors: Cho Seung Ho , Kim Taehyoun , Song Seung Jin
Published: August 2009

This paper presents aerodynamic and aeromechanical analyses for an entire row of fan blades (i.e. tens of blades with a finite aspect ratio) subject to a uniform incoming flow. In this regard, a new unsteady three-dimensional vortex lattice model has been developed for multiple blades in discrete time domain. Using the new model, the characteristics of the unsteady aerodynamic forces on vibrating blades, including their temporal development, are examined. Also, the new aerodynamic model is applied to examine the aeromechanical behavior of fan blades by using a standard eigenvalue analysis. For this analysis, the fan blades have been modeled as three-dimensional plates, and, increasing the number of blades (or solidity) is predicted to destabilize the fan blade row.
Extended Models for Transitional Rough Wall Boundary Layers With Heat Transfer: Part II—Model Validation and Benchmarking
Authors: Stripf M. , Schulz A. , Bauer H.-J. , Wittig S.
Published: August 2009

Two extended models for the calculation of rough wall transitional boundary layers with heat transfer are presented. Both models comprise a new transition onset correlation, which accounts for the effects of roughness height and density, turbulence intensity and wall curvature. In the transition region, an intermittency equation suitable for rough wall boundary layers is used to blend between the laminar and fully turbulent state. Finally, two different submodels for the fully turbulent boundary layer complete the two models. In the first model, termed KS-TLK-T in this paper, a sand roughness approach from Durbin et al., which builds upon a two-layer k-ε-turbulence model, is used for this purpose. The second model, the so-called DEM-TLV-T model, makes use of the discrete-element roughness approach, which was recently combined with a two-layer k-ε-turbulence model by the present authors. The discrete element model will be formulated in a new way suitable for randomly rough topographies. Part I of the paper will provide detailed model formulations as well as a description of the database used for developing the new transition onset correlation. Part II contains a comprehensive validation of the two models, using a variety of test cases with transitional and fully turbulent boundary layers. The validation focuses on heat transfer calculations on both, the suction and the pressure side of modern turbine airfoils. Test cases include extensive experimental investigations on a high-pressure turbine vane with varying surface roughness and turbulence intensity, recently published by the current authors as well as new experimental data from a low-pressure turbine vane. In the majority of cases, the predictions from both models are in good agreement with the experimental data.
Design Details of a 600 MW Graz Cycle Thermal Power Plant for CO2 Capture
Authors: Jericha H. , Sanz W. , Go¨ttlich E. , Neumayer F.
Published: August 2009

The high power highest efficiency zero-emission Graz Cycle plant of 400 MW was presented at ASME IGTI conference 2006 and at CIMAC conference 2007. In continuation of these works a raise of power output to 600 MW is presented and important design details are discussed. The cycle pressure ratio is increased from 40 to 50 bar by a half-speed stage connected via gears to the main compressor shaft allowing to keep the volume flow to the main compressors constant. The compressors are driven by the transonic compressor turbine stage. Mass flow to the compressors is increased by the factor of 1.27, density in blades of the main compressors is raised by the same factor. The turbine inlet temperature is raised to 1500°C together with the increase in the cycle pressure ratio, both are well accepted values in gas turbine technology today. Most important development problems have to be solved in designing the oxy-fuel burners. They are presented here in the form of coaxial jets of fuel (natural gas or coal gas alternatively) held together by a steam vortex providing coherent flow and flame is ignited by its strong suction. Combustion is finalized by the mixing with a counter-rotating outer vortex flow of working gas leading to a well defined position of vortex break down. The transonic stage of the compressor turbine is supplied with innovative steam cooling forming coherent layers outside of the blade shell of which stress deliberations will be presented.
Characterization of a Real Size Retrofittable Catalytic Combustion System
Authors: Diers Olaf , Fischer Michael , Heinze Johannes , Koopman Johan , Schneider Denis , Hassa Christoph , Friedl Markus J. , Carroni Richard
Published: August 2009

This contribution describes the investigation of an engine-scale catalytic hybrid burner. The burner has been investigated under atmospheric conditions with preheated air and natural gas fuel in two operating points, with and without the catalytic reactor. By using the catalyst, an extension of the operating range to leaner stoichiometries has been demonstrated. Exhaust gas analysis performed directly downstream of the burner as well as in the burner far-field showed a NOx reduction potential of more than 20% when employing the catalyst. For the operation with the catalytic reactor, the flame stabilization process and dependency of NOx formation on the piloting gas ratio is described with results of OH chemiluminescence measurements. Radial temperature profiles taken with Coherent Anti Stokes Raman Scattering (CARS) suggest a reaction delay directly downstream of the catalytic section of the burner. Calculations with a perfectly stirred reactor model help to obtain a better understanding of the kinetics of the hot gases leaving the catalyst section.
3D CFD Ingestion Evaluation of a High Pressure Turbine Rim Seal Disk Cavity
Authors: Mirzamoghadam A. V. , Heitland G. , Morris M. C. , Smoke J. , Malak M. , Howe J.
Published: August 2009

The amount of cooling air assigned to seal high pressure turbine rim cavities is critical for performance as well as component life. Less air leads to excessive hot annulus gas ingestion and its penetration deep into the cavity compromising disk life. Excessive purge air adversely affects performance. The minimum purge (i.e. sealing) air requirement to control ingestion is also influenced by annulus circumferential pressure fluctuation present over the rim seal cavity. Its interaction with the platform gap resistance and the amount of purge air needs to be understood in order to reliably predict performance and component life. Work has commenced to investigate opportunities in reducing disk cavity purge flow requirements by studying ways to control ingestion. The study has been initiated with 3D CFD model setup/run mode options to benchmark main/cavity flow field interactions. The selection of the appropriate CFD model fidelity, however, is one of the main goals of this work. The CFD model phase has 3 options to be evaluated; 1) steady solution with mixing plane aft of the cavity, 2) steady solution with mixing plane forward of the cavity, 3) unsteady solution. Option 1 has been completed and is the subject of this paper. A reference HP turbine stage and disk cavity from an engine design was selected for the CFD study. The steady flow solution model captured the oscillatory movement and penetration depth of ingestion by varying purge flow rate and observing the impact on the mixing plane forward and aft of the disk cavity. Moreover, the influence of upstream stator vane airfoil fillet shape was also investigated. The entrained flow was established by starving the cavity and integrating the outflow along the disk. This value along with the nominal and intermediate cavity purge flows were validated against relevant sealing flow design correlations. At a radial location near the rim, an ingestion mixing efficiency value versus purge flow rate was obtained which correlates well with recent unsteady flow results from the literature.
Novel Shrinkage-Free Structural Ceramic Materials for Gas Turbine Applications
Authors: Soudarev A. V. , Konakov V. G. , Morozov N. F. , Ovidko I. A. , Semenov B. N.
Published: August 2009

The paper presents results of development of the novel shrinkage-free, adaptable to machining and easily welded alumo-boron-carbide silicon materials that experience the cermet stage during their manufacturing. A specific feature of the like ceramics is their double-stage sintering process when, after the original stage, a metal-ceramic blank has a sufficient strength and is easily machined by conventional metal-cutting tools. In addition, such materials are electrically conductive, therefore, the elasto-erosion treatment technique can be applied. Subsequently, a machined part is finally sintered, whereas all the geometries remain actually unchanged due to the shrinkage absence. Prior to the final sintering, all separate parts can be joined by the diffusion welding with the seam strength being 5–10% different from the strength of the main part. The paper provides an insight into the processes and results of tests of the representative selections of samples of four types of the structural ceramics that are experiencing the cermet stage during the process of their formation. Also, ceramic parts for the CGTE hot passage are demonstrated.
Multi-Purpose Model of SOFC Hybrid Systems
Authors: Ghigliazza Francesco , Traverso Alberto , Ferrari Mario L. , Wingate John
Published: August 2009

The Multi-Purpose Model represents a new methodology for developing model based tools for control system design and verification. The Multi-Purpose Model, as described in this paper, simulates a SOFC hybrid system — a challenging and innovative application of dynamic modelling and control. Real-time modelling is a recognised approach to monitor advanced systems and to improve control capabilities. Applications of Real-Time (RT) models are commonly used in the automotive and aerospace fields. Starting from existing TRANSEO components and models, a new approach to fit hybrid system application has been developed. Original C-based models have been translated into embedded Matlab functions for direct use within Matlab-Simulink. The resulting models have then been used to autogenerate c-code with the Real-Time Workshop. The C-code has then been compiled to produce application specific executables.
Design and Performance Evaluation of a Trigeneration System Incorporating Hydraulic Storage and an Inverted Brayton Cycle
Authors: Blieske Matthew , Gauthier J. E. D. , Huang X.
Published: August 2009

To bring the economic benefit of trigeneration to small-scale users without incorporating expensive components, an inverted Brayton cycle (IBC) is employed which makes use of the expander section already present in a microturbine. An air accumulator provides pressurized air, which is passed through the expander section of the same microturbine used to charge the accumulator. The air passing through the IBC is cooled due to expansion, simultaneously providing power and cooling flow. As the microturbine is indirectly fired, the flow passing through the engine or IBC can be directly vented into the household; eliminating the need for additional heat exchangers. The size of the cycle studied is on the order of 10 kW(e), suitable for a domestic household, however the system is easily scaled for larger commercial applications. The majority of the components in the system studied are ‘off the shelf’ products. A feasibility study was conducted to ensure the proposed system is economically competitive with systems currently used, such as individual generation provided by an air conditioner, high efficiency natural gas furnace, and grid power. Simulations were run for a full year based on actual external temperature, electrical, and thermal loads for a single family detached dwelling located in Winnipeg, Canada. Performance data was generated using Matlab™ while economic performance was determined with time-based simulations conducted using Simulink™. The system is designed to allow energy islanding by providing for all household energy needs throughout the year, however integration with a power grid is optional. It was found the operating costs for the proposed trigeneration system in an energy islanding mode of operation were marginally higher than individual generation (A/C unit, NG furnace, grid power) during heating modes of operation, and more expensive for cooling modes of operation. The yearly energy cost for the trigeneration system exceeded the individual generation costs by 30 to 40%, however there remains much room for improvement to the trigeneration concept. All economic data was based upon fair market energy prices as found in central Canada.
Time-Frequency Analysis of Transient Vibrations to Improve Turbo-Compressor Start-Up
Authors: Jauregui Juan C. , Gonzalez Oscar , Rubio Eduardo
Published: August 2009

Diagnosis of turbo-compressors during start-up is a particularly challenging task. One of the reason is the reduced set of instruments that monitor this procedure. It is cumbersome to adjust lubrication and steam valves while controlling the speed and dynamic stability. In order to get the turbo-compressor out of a high vibration zone, it is important to be able to predict instabilities associated to the start-up process. Thus, it is necessary to have a measurement system with the ability of fault detection, especially at early stages of fault appearance. In this way, the start-up time can be significantly reduced. Although recent developed diagnosis methods use information from different sources and measurements, data structures are not designed to carry predictive information related to the turbo-compressor health. Therefore, it is important to extract early warning signals related to instability conditions. Vibration signals during machine start-up are non-stationary in nature, and conventional techniques, such as Fourier transforms and time series analysis, have difficulties to extract the full features of the vibrations signature. In this paper, the features of start-up vibrations in rotational systems like those found in turbo compressors are investigated by time-frequency analysis, and appropriate analysis of the transient vibration during compressor start-up is presented.
Tip Clearance Effects on Inlet Hot Streaks Migration Characteristics in High Pressure Stage of a Vaneless Counter-Rotating Turbine
Authors: Zhao Qingjun , Du Jianyi , Wang Huishe , Zhao Xiaolu , Xu Jianzhong
Published: August 2009

In this paper, three-dimensional multiblade row unsteady Navier-Stokes simulations at a hot streak temperature ratio of 2.0 have been performed to reveal the effects of rotor tip clearance on the inlet hot streak migration characteristics in high pressure stage of a Vaneless Counter-Rotating Turbine. The hot streak is circular in shape with a diameter equal to 25% of the high pressure turbine stator span. The hot streak center is located at 50% of the span and the leading edge of the high pressure turbine stator. The tip clearance size studied in this paper is 2.0mm (2.594% high pressure turbine rotor height). The numerical results indicate that the hot streak mixes with the high pressure turbine stator wake and convects towards the high pressure turbine rotor blade surface. Most of hotter fluid migrates to the pressure surface of the high pressure turbine rotor. Only a few of hotter fluid rounds the leading edge of the high pressure turbine rotor and migrates to the suction surface. The migration characteristics of the hot streak in the high pressure turbine rotor are dominated by the combined effects of secondary flow, buoyancy and leakage flow in the rotor tip clearance. The leakage flow trends to drive the hotter fluid towards the blade tip on the pressure surface and to the hub on the suction surface. Under the effect of the leakage flow, even partial hotter fluid near the pressure surface is also driven to the rotor suction surface through the tip clearance. Compared with the case without rotor tip clearance, the heat load of the high pressure turbine rotor is intensified due to the effects of the leakage flow. And the results indicate that the leakage flow effects trend to increase the low pressure turbine rotor inlet temperature at the tip region. The air flow with higher temperature at the tip region of the low pressure turbine rotor inlet will affect the flow and heat transfer characteristics in the downstream low pressure turbine.
Effective Thermoelastic Properties of Flat and Curved Transpiration Cooled Multilayer Plates via Homogenization
Authors: Laschet Gottfried , Rex Stephan
Published: August 2009

A multiscale approach based on the homogenization method of periodic material structures is developed here to predict the effective thermoelastic properties of heterogeneous porous materials. This method allows the calculation of effective equivalent properties either for each layer separatlely or for the multilayer of transpiration cooled multilayer plates. As gas turbine components are usually not flat, three different cooled plate designs — plane, convex and concave — are analyzed numerically. Effective Young and shear moduli as well as Poisson and thermal expansion coefficients are presented in detail for the reference flat plate. Then for the curved plates, the most sensitive effective Young and shear moduli of the TBC layer are compared with the reference ones. The effect of the blowing ratio on the effective orthotropic stiffness properties is outlined. The influence of local geometrical imperfections of the cooling channel shapes on the effective thermoelastic properties of the TBC layer of flat plates is also discussed in detail.
Unsteady Flow-Field Unreactive Experimental Characterisation and Velocity Fluctuations Analysis of an Ansaldo Energia Heavy Duty Gas Turbine Burner
Authors: Caruggi Mario , Nilberto Alessandro , Bonzani Federico
Published: August 2009

The research here presented is focused on the laser based experimental characterisation of an Ansaldo Energia burner equipping the Heavy Duty gas turbine (HD). The component is a partially premixed, swirl stabilized burner, adopting a central axial swirler surrounded by a mixed-flow, radially inward one. The burner can be fed with gaseous and liquid fuels by adopting three different injection modalities: diffusion, premixed and pilot injections. The experimental campaigns were carried out at DIMSET/SCL, the Savona Combustion Laboratory, within a joint research initiative between Ansaldo Energia and DIMSET (University of Genoa), on a full scale burner-combustor assembly, by scaling the base load operational conditions to ambient pressure under a Mach number similitude. The research activities performed have been addressed at achieving a detailed set of experimental data adequate to obtain a complete unsteady flow field characterisation in terms of velocity components’ radial distributions together with their local turbulent and periodical fluctuations within the combustor primary zone. In this way, the inner recirculation region at the burner exit can be neatly identified. Furthermore, the main fluid-dynamical parameters of the turbulent flow have been calculated, in terms of turbulent kinetic energy, turbulence intensity, Reynolds stresses and swirl number in order to characterise in detail the burner-combustor assembly from a fluid-dynamics point of view. The said investigations being performed with different operational and geometrical settings and properly managed in order to allow further burner developments at the technological/industrial level. In parallel, the research activities have also pursued the target of performing a thorough velocity fluctuation analysis, to be correlated with possible combustion instabilities, in order to attain a deeper comprehension of phenomena typically affecting gas turbine combustors, such as thermo-acoustical instabilities (humming). The velocity fluctuations have been investigated with particular reference to their inception locations within the burner: it turned out that they are typically related to the presence of the two different swirlers, which induce peculiar interactions between two different flow structures, each one presenting its own dynamical characteristics.
The Effects of IGV Wake Impingement on the Boundary Layer and the Near-Wake of a Rotor Blade
Authors: Soranna Francesco , Chow Yi-Chih , Uzol Oguz , Katz Joseph
Published: August 2009

This paper examines the response of a rotor blade boundary layer and a rotor near-wake to an impinging wake of an Inlet Guide Vane (IGV) located upstream of the rotor blade. Two-dimensional Particle Image Velocimetry (PIV) measurements are performed in a refractive index matched turbomachinery facility that provides unobstructed view of the entire flow field. Data obtained at several rotor phases enables us to examine IGV-wake-induced changes to the structure of the boundary layer and how these changes affect the flow and turbulence within the rotor near-wake. We focus on the suction surface boundary layer, near the blade trailing edge, but analyze the evolution of both the pressure and suction sides of the near-wake. During IGV-wake impingement, the boundary layer becomes significantly thinner, with lower momentum thickness and more stable profile compared to other phases at the same location. Analysis of available terms in the integral momentum equation indicates that the phase-averaged unsteady term is the main contributor to the decrease in momentum thickness within the impinging wake. Thinning of the boundary/shear layer extends into the rotor near wake, making it narrower and increasing the phase averaged shear velocity gradients and associated turbulent kinetic energy (TKE) production rate. Consequently, the TKE increases during wake thinning, with as much as 75% phase-dependent variations in its peak magnitude. The paper introduces a new way of looking at PIV data by defining a wake oriented coordinate system which enables to study the structure of turbulence around the trailing edge in great detail.
Efficient Design Method for Non-Synchronous Vibrations Using Enforced Motion
Authors: Spiker Meredith A. , Kielb Robert E. , Hall Kenneth C. , Thomas Jeffrey P.
Published: August 2009

This paper presents the results of a new enforced motion method using harmonic balance computational fluid dynamics (CFD) analysis to design for NSV. Currently, most researchers employ a time domain CFD technique to directly find the frequency of the underlying flow instability which can take significant computational time. NSV is said to occur when the frequency of the instability coincides with a blade mode frequency. The enforced motion design method uses blade motion to attempt to force the fluid frequency to lock-on to the blade vibration frequency at a specified amplitude. For a fixed critical amplitude and blade mode frequency, a range of interblade phase angles (IBPAs) is investigated to determine the aerodynamic damping. A negative value of damping at any IBPA deems the design unacceptable. Furthermore, a procedure for blade re-design (frequency changing) is presented. At the least stable IBPA, the damping is determined for a range of blade frequencies and amplitudes to determine the Limit Cycle Oscillation (LCO) amplitude. A better design is then at the blade frequency that minimizes the blade vibration amplitude. Therefore, these preliminary results indicate that it is advantageous to include blade motion in NSV design approaches. Most significantly, it gives designers a quick and efficient method to assess a design for NSV.
EVA: A Tool for EnVironmental Assessment of Novel Propulsion Cycles
Authors: Kyprianidis Konstantinos G. , Colmenares Quintero Ramon F. , Pascovici Daniele S. , Ogaji Stephen O. T. , Pilidis Pericles , Kalfas Anestis I.
Published: August 2009

This paper presents the development of a tool for EnVironmental Assessment (EVA) of novel propulsion cycles implementing the Technoeconomical Environmental and Risk Analysis (TERA) approach. For nearly 3 decades emissions certification and legislation has been mainly focused on the landing and take-off cycle. Exhaust emissions measurements of NOx, CO and unburned hydrocarbons are taken at Sea Level Static (SLS) conditions for 4 different power settings (idle, descent, approach and take-off) and are consecutively used for calculating the total emissions during the ICAO landing and take-off cycle. With the global warming issue becoming ever more important, stringent emissions legislation is soon to follow, focusing on all flight phases of an aircraft. Unfortunately, emissions measurements at altitude are either extremely expensive, as in the case of altitude test facility measurements, or unrealistic, as in the case of direct in flight measurements. Compensating for these difficulties, various existing methods can be used to estimate emissions at altitude from ground measurements. Such methods, however, are of limited help when it comes to assessing novel propulsion cycles or existing engine configurations with no SLS measurements available. The authors are proposing a simple and fast method for the calculation of SLS emissions, mainly implementing ICAO exhaust emissions data, corrections for combustor inlet conditions and technology factors. With the SLS emissions estimated, existing methods may be implemented to calculate emissions at altitude. The tool developed couples emissions predictions and environmental models together with engine and aircraft performance models in order to estimate the total emissions and Global Warming Potential of novel engine designs during all flight phases (i.e. the whole flight cycle). The engine performance module stands in the center of all information exchange. In this study, EVA and the described emissions prediction methodology have been used for the preliminary design analysis of three spool high bypass ratio turbofan engines. The capability of EVA to radically explore the design space available in novel engine configurations, while accounting for fuel burn and global warming potential during the whole flight cycle of an aircraft, is illustrated.
Experimental Investigation Into the Behaviour Within Flush Offtake Pipes
Authors: Dagefo¨rde Helge , Eastwick Carol , Robinson Adam , Johnson Graham , Kontin Sinisˇa , Bauer Hans-Jo¨rg
Published: August 2009

Within an aero-engine bearing chamber oil is provided to components to lubricate and cool. This oil must be efficiently removed (scavenged) from the chamber to ensure it does not overheat and degrade. To design an effective scavenge it is important to understand the inter-relationship between the flow at the offtake point and the flow structures within the offtake pipe. This paper describes a fundamental project that has experimentally investigated what happens to the flow in the inlet to the offtake and the offtake pipe when a moving liquid film passes over a vertical offtake. In particular the effect film height and momentum have on the flow structure in the offtake pipe is investigated. The rig employed for this work uses an inclined plane to develop a liquid film which then enters the offtake area. The closed circuit test rig is operated at room temperature with tap water as the working fluid. Water is chosen for visualisation reasons and because the viscosity and density of water at room temperature (≈ 25°C) are similar to those of aero-engine oil at a typical operating temperature (≈200°C). At the end of the Perspex inclined plane a fully-developed liquid film enters the scavenge area. The scavenge area is in two parts. The first is a horizontal plane that has a flush vertical offtake pipe mounted centrally to the width. The second section, downstream of the offtake section and connected to it, is a variable angled plane. This allows the rig to be configured so that the liquid film can either overspill the scavenge section or, if the variable angled plane is raised, for flow that passed the offtake to be returned back. The fluid behaviour at the inlet of the offtake and the flow pattern in the offtake pipe are investigated for two different pipe diameters using visualisation. The incoming film height is recorded by the use of a flush conductance probe. The offtake is drained under gravity in its present configuration. The results from the work allow a regime map of flow behaviour to be created, dependent on the incoming flow conditions, that identifies when air is ingested into the offtake and in what form (annular, bubbly etc).