bluuebunny/crossref_metadata_2025 huggingface dataset:
Predicting Transition in Turbomachinery: Part II — Model Validation and Benchmarking
Authors: Praisner T. J. , Grover E. A. , Rice M. J. , Clark J. P.
Published: November 2008

The ability to predict boundary layer transition locations accurately on turbomachinery airfoils is critical both to evaluate aerodynamic performance and to predict local heat-transfer coefficients with accuracy. In state-of-the-art Reynolds Averaged Navier-Stokes (RANS) simulations used to predict flowfields on turbomachinery airfoils, boundary layers are often assumed to be turbulent over the entire airfoil surface. Consequently, losses are not accurately predicted, particularly in the case of stalled airfoils. Here we report on an effort to include empirical transition models developed in Part I of this report in a RANS solver. To validate the new models, a two-dimensional design optimization was performed to obtain a pair of Low-Pressure Turbine (LPT) airfoils with the objective of increasing airfoil loading by 25%. Subsequent experimental testing of the resulting two new airfoils confirmed pre-test predictions of both high and low Reynolds number loss levels. In addition, the accuracy of the new transition modeling capability was benchmarked with a number of legacy cascade and LPT rig data sets. Good agreement between measured and predicted profile losses was found in both cascade and rig environments. However, use of the transition modeling capability has elucidated deficiencies in typical RANS simulations that are conducted to predict component performance. Efficiency-versus-span comparisons between rig data and multi-stage steady and time-accurate LPT simulation results indicate that loss levels in the endwall regions are significantly under-predicted. Possible causes for the under-predicted endwall looses are discussed as wall as suggestions for future improvements that would make RANS-based transitional simulations more accurate.
Linear Stability Analysis of LPT Rotor Packets: Part I — Methodology and Two-Dimensional Results
Authors: Corral Roque , Lopez Carlos , Vasco Carlos
Published: November 2008

Part I of this paper compares the aerodynamic damping of a modern LPT airfoil to the one obtained when pairs of blades are forced to vibrate as a rigid body to mimic the dynamics of welded-pair assemblies. The stabilizing effect of this configuration is shown by means of two-dimensional linear simulations using the Panovsky and Kielb (PK) method. A plausible physical mechanism for the added damping of the welded-pair configuration is outlined. The modal characteristics of three bladed-disc models that differ just in the boundary conditions of the tip-shroud are also compared. These models are representatives of cantilever, interlock and welded-pair designs of low pressure turbine (LPT) rotating parts. The differences in terms of frequency and mode-shape of the three models are sketched. Finally their relative merits from a flutter point of view are discussed making use solely of the two-dimensional aerodynamic damping characteristics.
Managing Reliability Improvement in the U.S. Navy’s Marine Gas Turbine Generator Sets
Authors: Russom Dennis M. , Mummaw Keith , Pineiro Ivan
Published: November 2008

Gas Turbine Generator Sets (GTGs) provide electrical power for the U.S. Navy’s DDG-51 Class ships. These GTGs, packaged by Rolls Royce and powered by the Rolls Royce 501-K34, have been the subject of substantial, well-documented improvement efforts. This paper discusses the processes used to evaluate reliability and identify problematic components. It describes corrective actions that have been made to date and lays out a plan for the future. It goes on to discuss the impact that each improvement has made to GTG reliability and life cycle costs while attempting to project future impact.
Simplified, On-Line Performance Monitoring of Simple Cycle Gas Turbines Using Spreadsheet-Based Calculations
Authors: Phillips Jeffrey N. , Boyce Meherwan P. , Grandmont Jay , Angello Leonard
Published: November 2008

A spreadsheet-based performance monitoring software program has been developed which uses OEM correction curves and thermodynamic analysis to compare actual simple cycle gas turbine performance to expected performance over the full-range of operation including part-load. The program has been designed to require a minimum of user set-up and can interface with widely-used, third-party data historians to access plant operating data in real-time. In addition to providing overall plant performance indicators, the program also provides component-level indicators such as combustion turbine compressor section efficiency. An overview of the algorithms used to calculate actual and expected performance is provided. The advantages and shortcomings of this approach are compared to those used by others. Results are presented from initial testing of the software on a 500 MW combined cycle power featuring two GE 7FA combustion turbines. Performance results include data on the compressor section efficiency of a 7FA over a wide range of operating conditions.
Performance Investigation of Film and Transpiration Cooling
Authors: Wang J. H. , Messner J. , Casey M. V.
Published: November 2008

This paper presents an experimental investigation of the performance of film and transpiration cooling. Two circular tubes were used as test models, one consisted of sintered porous material with a mean porosity of 21% to create a transpiration cooling effect, and the other was made of solid material with four rows of discrete injection holes to simulate film cooling effect in a gas turbine blade. Two series of tests were carried out in the hot-gas wind tunnel at the Institute of Thermal Turbomachinery at the University of Stuttgart. In the first series, the Reynolds numbers based on the tube diameter were between 1.13×105 and 1.31×105, the apparent temperature on the test models was measured using infrared thermal imaging technique and the corresponding cooling effects were calculated. The test results indicated that in comparison with film cooling, transpiration cooling on the porous tube had a greater stability when the upstream state was changed. In the second series, the static pressure distribution along the test section of the wind tunnel was measured under different coolant blowing ratios, and the corresponding influence on mainstream due to coolant injection through film holes and transpiration pores was analyzed. The tests proved that coolant blowing from the film holes at the leading edge and on the side of the solid tube resulted in a change in static pressure downstream of the injection holes, whereas coolant injection from the pores in the trailing region of the porous tube led to a change in static pressure upstream of the tube.
Simulation of Fuel/Air Premixing Under the Effects of Acoustic Forcing
Authors: Van Slooten Paul R. , Madabhushi Ravi K. , Stufflebeam John H. , Lienau Jeffrey
Published: November 2008

To achieve ultra-low NOx emissions in practical lean premixed combustors, a uniform spatial and temporal fuel/air distribution is required. In addition the response of the fuel/air premixer to acoustic perturbations plays a central role in the coupling of the combustion and acoustic processes that potentially lead to thermoacoustic instabilities. In this paper, results from the simulation of a fuel/air premixer with and without acoustic forcing are reported. An unsteady Reynolds-Averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) code is used in the simulations and the computed results are compared with data obtained using a synchronous PLIF technique. Planar phase-locked images of the fuel/air distribution during the forcing cycle are measured from which the planar averaged (bulk) fuel/air ratio “signal” is obtained. The fuel/air ratio to velocity transfer function (time delay and magnitude) at a specific forcing frequency is computed corresponding to a given jet-to-air momentum flux ratio. The comparisons between the computed and measured time delays are quite good, while the magnitude comparisons are currently inconclusive.
Investigation Into the Computational Analysis of Direct-Transfer Pre-Swirl Systems for Gas Turbine Cooling
Authors: Benim A. C. , Brillert D. , Cagan M.
Published: November 2008

Direct transfer pre-swirl systems have been investigated by means of 3D computational analysis. Different computational approaches have been utilized and results have been compared with measurements. Based on the validation studies, guidelines for modeling such systems have been proposed. The present results imply that sufficiently accurate predictions can be obtained by means of a quasi-steady analysis applying the “frozen rotor” approach for treating the interface between the stationary and rotating domains. The results indicate that the dimensionless pressure and temperature show a rather weak sensitivity to the relative position of the stator and rotor, using the frozen rotor approach, for the cases studied.
Identification of Bearing Force Coefficients From Measurements of Imbalance Response of a Flexible Rotor
Authors: San Andre´s Luis , De Santiago Oscar C.
Published: November 2008

Field identification of fluid film bearing parameters is critical for adequate interpretation of rotating machinery performance and necessary to validate or calibrate predictions from restrictive computational fluid film bearing models. This paper presents a simple method for estimating bearing support force coefficients in flexible rotor-bearing systems. The method requires two independent tests with known mass imbalance distributions and the measurement of the rotor motion (amplitude and phase) at locations close to the supports. The procedure relies on the modeling of the rotor structure and finds the bearing transmitted forces as a function of observable quantities (rotor vibrations at bearing locations). Imbalance response measurements conducted with a two-disk flexible rotor supported on two-lobe fluid film bearings allow validation of the identification method estimations. Predicted (linearized) bearing force coefficients agree reasonably well with the parameters derived from the test data. The method advanced neither adds mathematical complexity nor requires additional instrumentation beyond that already available in most high performance turbomachinery.
Experimental Study on the Role of Entropy Waves in Low-Frequency Oscillations for a Diffusion Burner
Authors: Eckstein J. , Freitag E. , Hirsch C. , Sattelmayer T.
Published: November 2008

“Rumble” is a self-excited combustion instability, usually occurring at the start-up of aero-engines with fuel-spray atomizers at sub-idle and idle conditions, and exhibiting low limit frequencies in the range of 50 Hz to 150 Hz. Entropy waves at the (nearly) choked combustor outlet are supposed to be the key feedback-mechanism for the observed self-excited pressure oscillations. The experimental study presented here aims to clarify the role of the entropy waves for the occurrence of rumble. A generic air-blast atomizer with a design being prone to self-excitation has been incorporated into a thermoacoustic combustor test rig with variable outlet conditions. The flame thermoacoustics were characterized by recording the OH*-chemiluminescence, the dynamic pressures, the dynamic temperatures, and by applying PIV. The measurements have shown the occurrence of periodic hot spots travelling with the mean flow with considerable dispersion. Measurements have been conducted with an open-ended resonance tube in order to eliminate the impact of entropy waves on the mechanism of self-excitation. The oscillation obtained, comparable in amplitude and frequency, proved that self-excitation primarily depends on convective time delays of the droplets in the primary zone and thus on the atomization characteristics of the nozzle.
Numerical Study of an Inlet Particle Separator
Authors: Ghenaiet A. , Tan S. C.
Published: November 2008

Helicopters operating in a desert region are often subjected to the environmental effects of sand ingestion that can erode gas turbine engines and block the cooling passages. Traditional method of removing sand particles include barrier filters that employed vortex tube and impact filter designs, and inertial particle separator (IPS). Barrier filters are normally quite heavy and require constant servicing or replacement. IPS relies on contoured surfaces to direct particulates to a scavenge area through the actions of the viscous forces and bounce characteristics of the sand particles. The geometrical design of an IPS plays an important role in determining the sand separation efficiency. This paper presents a numerical study of the RTM322 IPS, which includes the effects of changing the hub, splitter and scavenge duct geometries on the sand separation efficiency. The flow field calculation in the IPS was performed with the commercial CFD software package called TASCflow. The particle trajectories were computed using an in-house developed trajectory code, which was based on the lagrangian method. The effects of flow turbulence on the trajectory were simulated using the eddy lifetime concept. Several design geometrical modifications were investigated such as the shape of the hub and splitter and their relative locations. Particle trajectories and separation efficiency were performed for a range of sand particle sizes, inlet mass flow rates and scavenge ratios.
Thermodynamic Analysis of “Inter-Turbine” and “Intra-Turbine” Reheat for Marine Gas Turbines
Authors: Millsaps Knox T. , Rodman Bruce
Published: November 2008

This paper presents thermodynamic analyses of two types of reheat combustion cycles in gas turbines and provides an evaluation of their usefulness in marine power and propulsion applications. Specifically, baseline cycles, using components of various technology levels, were compared to cycles with single-stage reheat (inter-turbine reheat), and continuous or constant temperature reheat (intra-turbine reheat). the results of this primary flow path analysis show that reheat can greatly increase the power density, while reducing the total fuel consumption over a standard warship mission profile. These trends are strongest at lower technology levels, but are also present at higher component technology levels.
Proposal of Innovative Gas Turbine Combined Cycle Power Generation System
Authors: Moritsuka Hideto
Published: November 2008

In order to estimate the possibility to improve thermal efficiency of power generation use gas turbine combined cycle power generation system, benefits of employing the advanced gas turbine technologies proposed here have been made clear based on the recently developed 1500C-class steam cooling gas turbine and 1300C-class reheat cycle gas turbine combined cycle power generation systems. In addition, methane reforming cooling method and NO reducing catalytic reheater are proposed. Based on these findings, the Maximized efficiency Optimized Reheat cycle Innovative Gas Turbine Combined cycle (MORITC) Power Generation System with the most effective combination of advanced technologies and the new devices have been proposed. In case of the proposed reheat cycle gas turbine with pressure ratio being 55, the high pressure turbine inlet temperature being 1700C, the low pressure turbine inlet temperature being 800C, combined with the ultra super critical pressure, double reheat type heat recovery Rankine cycle, the thermal efficiency of combined cycle are expected approximately 66.7% (LHV, generator end).
Experimental Lift Off Characteristics and the Effect of a Low Friction Coating on the Startup Response of Simple Gas Hybrid Bearings for Oil-Free Turbomachinery
Authors: Wilde Deborah A. , San Andre´s Luis , Aguirrezabala Julene
Published: November 2008

Improved mechanical efficiency is a driving advantage for the application of gas hybrid bearings to oil free turbomachinery. Characterizing the transient response of rotors supported on gas bearings during high friction contact at start up and shut down is essential to improving system reliability and performance. Further experimental results obtained in a test rig consisting of a rotor/motor supported on simple hybrid gas bearings are reported. The experiments of startup transient rotor responses aim to reveal the rotor lift off speed and time for full film gas bearing support. Exact determination of rotor lift off conditions from the time domain data is highly subjective. Ensemble overlapped FFTs of the rotor displacement response reveal the synchronous response and excitation of the rotor-gas bearing natural frequency at lift off. The analysis of the test transient responses also determines the lowest feed pressure for sustained operation at low speeds. Identifying the rotor-bearing system time constant and comparing lift-off speeds and times for uncoated and coated rotors shows the beneficial effect of an inexpensive low-friction solid lubricant (PTFE based coating) applied to the test rotor at room temperature.
Evaluation of Available Technologies for Chicken Manure Energy Conversion and Techno-Economic Assessment of a Case Study in Italy
Authors: Fantozzi Francesco , D’Alessandro Bruno , Leonardi Daniela , Desideri Umberto
Published: November 2008

Chicken manure used as a natural fertilizer, given its high Nitrogen content, requires key actions in odor control that are often difficult to carry out resulting in an image loss for the company. Manure land-filling however is costly as well as incineration and this latter does still require odor control. Energy conversion from chicken manure may turn the cost into an earning that could payback both the investment and the image loss for odorous emissions. In this optic the paper analyses the different technologies that are available for energy conversion from chicken manure namely incineration, gasification, pyrolysis and anaerobic digestion with application to a real case. A large scale egg selling company in central Italy, with three production sites, was selected and its mass and energy flow balance assessed with particular reference to manure production and electricity consumption and expense. Five different technologies were then considered for energy conversion from chicken manure both for a single production site (microscale) and for the three (small scale). Grate incineration with steam production from exhaust gases was considered and discarded because of the too small scale. BTG gasification technology and IPRP pyrolysis technology presented by the authors, were evaluated and the techno-economic assessment showed interesting pay back time with medium to high investment costs and medium efficiencies. Pyrolysis technology with gas-steam combined cycle was considered but the economics show a very high pay back for the investment due to the small scale. Finally anaerobic digestion was evaluated showing the lowest investment cost and efficiency but an interesting payback period also considering that no public financing was considered. This latter solution has been presented to the company that will decide whether to finance the project.
Development of Express Calculation-Experimental Technique to Estimate Life and Reliability of Ceramic Parts and Components
Authors: Soudarev A. V. , Molchanov A. S.
Published: November 2008

The analysis of existing programs to develop advanced ceramic gas turbine engines indicates that the challenge to ensure a target life of ceramic components is of a paramount importance. The up-to-date express methodologies to define life have some principal limitations which necessitates to carry out labor- and time-consuming tests of bulky batches of ceramic samples and parts. The accuracy of the predicted results, at the same time, remains rather low which does not allow their practical application to design ceramic parts and components. An improvement of techniques of the life estimation could be attained considering that a crack growth takes place under load, this phenomenon occurring with the crack shear stress generation, this stress correlating with a threshold value of the stress intensity factor. It turns out here that along with the dynamic failure, the test duration is also a significant parameter, i.e. the parameter which is neglected by the current methodology to estimate the static failure and life. The developed methodology demonstrates not a bad correlation between the estimates and the experimental values, whereby reducing the scope of the initial data compared with the current methodology. Furthermore, using this approach one can predict results of proof tests which enables opting for an optimum proof duty. A result of the proof tests is essentially dependent on three test condition parameters, namely: 1. The value of a selected trial loading or a fraction of the parts rejected; 2. The exposition time under the trial loading; 3. The test temperature and the initial scatter of the strength properties. The sequence of the calculation carrying out is as follows: 1. A required Weibull modulus is identified using the static failure estimate technique for a target reliability of the ceramic element, stresses under the operation conditions, operation time, dynamic failure parameters. 2. The proof test conditions are identified using the Weibull modulus required. The obtained calculation formulae need a smaller scope of the experimental data with the static failure accuracy and life becoming greater compared with the existing values. Thus, the methodology presented allows to ensure a target reliability of ceramic parts, to identify their quantity required and the preliminary tests conditions.
Mist/Steam Heat Transfer of Multiple Rows of Impinging Jets
Authors: Wang Ting , Gaddis J. Leo , Li Xianchang
Published: November 2008

Internal mist/steam blade cooling technology is considered the future of high-temperature gas turbine systems that burn hydrogen or synthetic gases. This paper experimentally investigates the mist/steam heat transfer of three rows of circular jet impingement in a confined channel. Fine water droplets with an average diameter of 3-μm are generated by atomizing water through small nozzles under high pressure. The circular jets have a uniform diameter of 8-mm, and the distance between adjacent jets in a row is 3 diameters. Jets in different rows are staggered and the distance between rows is 1.5 diameters. The spacing of nozzle-to-target is 2.8 diameters. Experiments were conducted with Reynolds numbers at 7,500 and 15,000 and heat fluxes ranging from 3,350 to 13,400W/m2. The results indicate that the wall temperature significantly decreased because of mist injection. A region of high cooling enhancement is observed and more extensive than those employing one row of circular jets or a slot jet. While the details depend on flow conditions, it is seen that the enhanced region of 3-row jets is about 5 jet diameters at Re = 7,500, q” = 7.54 kW/m2, and ml/ms = 3.5%, compared to 2 jet diameters for single-row jets. The enhancement becomes negligible after a certain distance downstream. The maximum local cooling enhancement is up to 800% by injecting 3.5% of mist at low heat flux condition and 150% for high heat flux condition. The average cooling enhancement can achieve more than 100% within 2 jet-diameter distance from the stagnation line at Re = 15,000 and ml/ms = 1.5%.
Indirectly Heated Pyrolysis for Selected Biomass Materials
Authors: Sun Li , Xu Min , Sun Rongfeng
Published: November 2008

Pyrolysis is an important basic process for biomass thermo-chemical conversion. By different condition of the process, a series of technologies can be designed to produce different products, such as mid-Btu gas, syngas, liquid fuel and hydrogen. This paper presents the experimental data for selected biomass materials on indirectly heated pyrolysis process. The influences of temperature on parameters such as pyrolysis products, mass balance relationship, composition of gas, are described. This research paves the way to two technical directions. One combines with a gasifier to produce gas with very low tar content, which can be used to generate electricity. Another, in association with secondary decomposition process, generates hydrogen-rich gas.
The Coarsening Kinetic of γ′ Particles in Nickel-Based Superalloys During Aging at High Temperatures
Authors: Mastromatteo F. , Niccolai F. , Giannozzi M. , Bardi U.
Published: November 2008

Nickel-based superalloys are widely used in applications requiring strength at high temperature, and in particular in manufacturing of several important components of both aeronautics and land based gas turbines. The main property of these materials is due to their particular microstructure consisting of a fcc lattice nickel matrix (γ phase), strengthened by precipitation of a second phase Ni3(Ti,Al) (γ′ phase), having fcc lattice. During aging at high temperatures, γ′ precipitates increase their size, following a kinetic law described by the classical LSW theory. In this work the growth kinetic of γ′ precipitates for the superalloy GTD 111 has been investigated by SEM. Samples of the alloy have been aged in the typical range of service temperatures for times up to 8000 hours. For each sample a large number of images has been acquired and the size and distribution of γ′ particles have been evaluated. Plotting the average size values, corresponding to the different times and temperatures analyzed, it was possible to obtain the growth kinetic of these particles, finding that the above mentioned theory gives a good description of the observed behaviour. The data obtained for GTD 111 have been also compared with other data referring to INCONEL 738, obtained from samples aged in the same conditions and analyzed in the same way. GTD 111, when compared to IN738, resulted to have a much slower growth kinetic, resulting in a much higher creep resistance. From the collected data it was possible to calculate also the activation energy for the diffusion process for both alloys, finding out values in agreement with those obtained by other authors and very close to the activation energies of Ti and Al in Ni matrix.
Investigation of the Tonal Acoustic Field of a Transonic Fanstage by Time-Domain CFD-Calculations With Arbitrary Blade Counts
Authors: Schnell Rainer
Published: November 2008

In order to investigate the tonal noise generated by viscous blade/vane interaction in a typical transonic bypass engine fan stage, time domain calculations were carried out with the non-linear Navier-Stokes solver TRACE. The propagating acoustic field was obtained by a modal decomposition of near field flow data. Comparisons with available experimental data in the bypass duct casing are presented. Different OGV designs of the investigated fanstage were evaluated with respect to the emitted tonal noise of the stage. To ensure the correct modal structure of the acoustic field it is vital to employ the correct blade count ratio in numerical simulations. To accomplish this efficiently, phase-lagged boundary conditions were incorporated into the employed flow solver. The method has been validated using a counter-rotating propfan configuration and was then applied for the three dimensional, spatially highly resolved fanstage calculation.
Micro Gas Turbine Combustion Chamber Design and CFD Analysis
Authors: Parente Joao , Mori Giulio , Anisimov Viatcheslav V. , Croce Giulio
Published: November 2008

In the framework of the non-standard fuel combustion research in micro-small turbomachinery, a newly designed micro gas turbine combustor for a 100-kWe power plant in CHP configuration is under development at the Ansaldo Ricerche facilities. Combustor design starts from a single silo chamber shape with two fuel lines, and is associated with a radial swirler flame stabiliser. Lean premix technique is adopted to control both flame temperature and NOx production. Combustor design process envisages two major steps, i.e. diagnostics-focussed design for methane only and experimentally validated design optimisation with suitable burner adaptation to non-standard fuels. The former step is over, as the first prototype design is ready for experimental testing. Step two is now beginning with a preliminary analysis of the burner adaptation to non-standard fuels. The present paper focuses on the first step of the combustor development. In particular, main design criteria for both burner and liner cooling system development are presented. Besides, design process control invoked both 2D and 3D CFD analysis. Two turbulence models, FLUENT standard k-ε model and Reynolds Stress Model (RSM), are refereed and the results compared. Here both a detailed analysis of CFD results and a preliminary analysis of main chemical kinetic phenomena are discussed.
Urban Air Quality Impacts of Distributed Generation
Authors: Carreras Marc , Medrano Marc , Samuelsen G. S. , Brouwer Jack , Rodriguez Marco , Dabdub Donald
Published: November 2008

Distributed Energy Resources (DER) have the potential to supply a significant portion of increased power demands in California and the rest of the US. Distributed generation is characterized by many stationary power generators that are distributed throughout an urban air basin. In contrast, central-generation sources are typically located outside the basin. As a result, distributed generation may lead to increased pollutant emissions within an urban air basin, which could adversely affect air quality. The present project develops a systematic approach for characterizing the installation of DER in an urban air basin and simulates the potential air quality impacts using a state-of-the-art three-dimensional computer model. The assessment of the air quality impacts associated with DER is made in the South Coast Air Basin (SoCAB) of California for the year 2010. Initial results suggest that DER characterization can be systematically applied to urban air basins, and that realistic DER implementation in SoCAB by the year 2010 only slightly affects concentrations of ozone and particulate matter in the basin.
Application of Multistage CFD Analysis to Low Pressure Compressor Design
Authors: Brilliant Lisa , Balamucki Stanley , Burger George , Dong Yuan , Lejambre Charlie
Published: November 2008

A Low Pressure Compressor (LPC) is unique in its requirements for wide operating range during a flight mission. As a result, the aerodynamic design involves a trade-off between performance and stall margin. The requirement to reduce engine development cost and schedule has resulted in developing LPCs during the engine validation program. With engine validation and certification schedules being compressed continuously, getting the initial design right has become critical. Multistage CFD analysis is used in the current design process to optimize the airfoils and stage matching. Three-dimensional airfoil features, such as bow, that improve secondary flow features and can be optimized using CFD. The PW6000 LPC engine test data has validated the analytical results and demonstrated surge margin and efficiency levels above the requirements. The LPC also achieved all other design objectives in its first build, representing a significant cost saving for a new centerline engine development program.
Assessing Fan and Compressor Blade HCF Sensitivity to Non-Uniform Inlet Flows
Authors: Wallace Robert M. , King Peter S. , Kenyon James , O’Brien Walter F.
Published: November 2008

In recent years, the subject of high cycle forced response excitation of aircraft turbine engine components and resulting fatigue failures (HCF) has been of increasing concern. Prediction and test methods are needed that can identify inlet distortion-related HCF drivers and response, and support assessment and correction of potential problems before failure occurs. The present paper describes a method by which inlet distortions may be examined for flow-distortion-driven HCF excitation potential in a test situation. The method was derived from results of a distortion screen test that produced periodic excitation in a two-stage transonic fan. A CFD method is used to predict the unsteady pressure field on the first stage blades due to a harmonic component of the measured total pressure distortion. A finite element (FE) model of the blade is then used to identify modal frequencies and predict vibratory stress and strain, providing information on the HCF potential and sensitivity to the imposed distortion. The method avoids the need for a full unsteady, coupled CFD-FE model of the entire compressor flowpath, and the calculations can be conducted rapidly. For the case evaluated, it is shown to produce stress predictions that compare to within 5% of the experimental values.
New Compressed Air Energy Storage Concept Improves the Profitability of Existing Simple Cycle, Combined Cycle, Wind Energy, and Landfill Gas Power Plants
Authors: Nakhamkin Michael , Wolk Ronald H. , van der Linden Sep , Patel Manu
Published: November 2008

The proposed novel compressed air energy storage (CAES) concept is based on the utilization of capacity reserves of combustion turbine (CT) and combined cycle (CC) plants for the peak power generation, instead of development of highly customized and expensive turbo-machinery trains. These power reserves are particularly high during high ambient temperatures that correspond to typical summer peak power requirements. The stored compressed air will be injected into the CT after the compressor diffuser to supplement the reduced (due to high ambient temperature or altitudes) mass flow, through the turbine to the full potential (typically achieved at low ambient temperatures). The alternative concept, with stored compressed air, is humidification before injection into the CT, this reduces the auxiliary compressor size, the storage volume and associated costs. Power increase of up to 25% can be realized, coincidental with that which is typical for a CAES plant, significant reduction in the heat rate and emissions. The novel CAES concept reduces specific plant costs by a factor of two, which makes it particularly effective for integration with renewable energy sources, like wind energy plants and landfill gas (LFG) plants. The paper also presents an alternative small capacity CAES plant, which is based on using smaller man-made storage facilities (high pressure pipes and/or vessels), either underground or above ground that can be readily constructed at CT sites without specific geological requirements. The latter part of this paper specifically concentrates on integration of CAES with wind and landfill gas (LFG) plants.
Numerical Optimization of a Vaned Shroud Design for Increased Operability Margin in Modern Centrifugal Compressors
Authors: Barton M. T. , Mansour M. L. , Liu J. S. , Palmer D. L.
Published: November 2008

This paper describes the computational fluid dynamics (CFD) approach coupled with an automated grid generation technique utilized for the numerical optimization of a modern centrifugal compressor with an inducer vaned shroud for increased operability margin. The grid generation process was automated to permit rapid optimization of the impeller and vaned shroud geometry. A three dimensional (3D), viscous, steady flow, mixing-plane approach was utilized to numerically analyze the impeller and vaned shroud in a coupled fashion to capture the interaction effects. The numerical technique verifies the ability of the vane shroud to extend compressor surge margin at the part-speed operating condition, while maintaining acceptable high-speed performance. CFD analyses confirm that the aerodynamics of the vaned shroud match expectation, and are consistent with the mass-averaged compressor speedline characteristics generated from the CFD results.
Optimization of Rotor Critical Speeds by Change of Features of Machine’s Bearings
Authors: Rybczynski Jozef
Published: November 2008

The subject of this article is an analysis of the influence of changes of certain construction and operation parameters of slide bearings on the critical speeds and corresponding forms of vibrations of rotors supported in such bearings. An exemplary analysis has been made for a typical, average sized turbo-compressor train consisting of three rotors. It has been found that critical speeds of a rotor are most sensitive to the bearings clearance; less sensitive to the bearings length, and least sensitive to the oil mean temperature. Found relations permit to avoid an accidental search for a way to change the rotor critical speeds if there is such a necessity and when it is impossible to change the geometry of the rotor itself. The results of the analysis allow optimization of the process of detuning the machine from resonance.
Effect of Rotor Tip Speed and Stator Sweep on Rotor-Stator Interaction
Authors: Atassi Oliver V. , Hall Christopher M.
Published: November 2008

Data taken in the Source Diagnostic Test of the unsteady pressure on a fan-exit guide vane is analyzed to identify the dominant noise producing regions on the vane. The dominant noise source regions of the vane are identified as the outer fifty percent span of the vane. The sensitivity of this result to fan tip speed and exit guide vane sweep is studied. Sweep is seen to decrease the radial correlation length of the unsteady vane response and hence decrease the noise produced by wake-vane interaction. Results for the periodic component of the fan wakes show that the magnitude of the wake harmonics is largest in the outer fifty percent span of the duct and the radial phase variation is largest in the hub region. These results demonstrate a strong cause and effect relationship between the radial distribution of the wake harmonics and the dominant noise producing regions on the fan-exit guide vane.
Progress on Environmentally Compliant Aluminum Ceramic Compressor Coatings
Authors: Mosser Mark F.
Published: November 2008

During the last decade there has been an increasing emphasis on compliance to ever stricter environmental laws as well as compliance to regulations that have been designed to protect workers from exposure to toxic or otherwise harmful substances or processes. This world-wide emphasis has forced a continuing review of materials and processes used in the manufacture and protection of compressor materials from corrosion. Turbine compressors have been coated with silicone aluminum paint, diffused nickel cadmium and aluminum pigmented ceramic coatings that contain hexavalent chromium. These three processes utilize various chemicals including toxic substances, carcinogens and volatile organic compounds (VOC). All three of the coating processes need to be either made compliant or eliminated from use. This paper will review efforts that have been made to develop compliant aluminum ceramic compressor coating materials as applied to various steel and stainless steel substrates. In all cases the new materials that have been developed are free of toxic or carcinogenic materials. Test results will be compared to specification requirements for chrome containing compressor coatings in the area of physical properties including surface finish, thickness and adhesion. Additionally, environmental test data will be presented based on standard test methods that compare new compliant coatings with conventional chrome containing materials. Finally, process steps and conditions will be described for these new coatings.
Compressor Stall Control Through Endwall Recirculation
Authors: Strazisar Anthony J. , Bright Michelle M. , Thorp Scott , Culley Dennis E. , Suder Kenneth L.
Published: November 2008

Experiments that demonstrate the use of endwall recirculation to control the stall of transonic compressor stages are described. Endwall recirculation of a compressor stage is implemented by bleeding air from the casing downstream of a stator blade row and injecting the air as a wall jet upstream of a preceding rotor blade row. The bleed ports, injection ports, and recirculation channels are circumferentially discrete, and occupy only 20–30% of the circumference. The development of compact wall-jet injectors is described first. Next, the results of proof-of-concept steady recirculation tests on a single-stage transonic compressor are presented. Finally, the potential for using endwall recirculation to increase the stability of transonic highly-loaded multistage compressors is demonstrated through results from a rig test of simulated recirculation driving both a steady injected flow and an unsteady injected flow commanded by closed-loop active control during compressor operation at 78–100% of design speed. In this test air from an external source was injected upstream of several rotor blade rows while compressor bleed was increased by an amount equivalent to the injected massflow. During closed loop control, wall static pressure fluctuations were monitored and the injected flow rate was controlled to reduce the stalling mass flow. The use of wall jet injection to study the dynamics of transonic compressor stages is also discussed.
Non-Metallic Brush Seals for Gas Turbine Bearings
Authors: Bhate Nitin , Thermos Anthony C. , Aksit Mahmut F. , Demiroglu Mehmet , Kizil Huseyin
Published: November 2008

A non-metallic brush seal has been developed as an oil seal for use in turbomachinary. Traditionally labyrinth-type seals with larger clearances have been used in such applications. Labyrinth seals have higher leakage rates and can undergo excessive wear in case of rotor instability. Brush seals reduce leakage by up to an order of magnitude and provide compliance against rotor instabilities. Brush seals are compact and are much less prone to degradations associated with oil sealing. This paper describes the benefits and development of the non-metallic brush seals for oil sealing application.
Insertion of Electrostatically Charged Fuel Atomization Technology Into a U.S. Navy Shipboard Gas Turbine Engine
Authors: Guimond David P. , Thomas Matthew E. , DiSalvo Roberto , Elliot Adam , Crocker D. Scott
Published: November 2008

Recent breakthroughs in the field of hydrocarbon fuel electrostatic charging techniques have now permitted the opportunity for the Navy to consider implementing this technology into shipboard gas turbines. This research effort is focused toward electrostatic atomization insertion into a U.S. Navy Shipboard Rolls Royce Corporation 501-K research engine at the Naval Surface Warfare Center, Carderock Division (NSWCCD). Specific milestones achieved thus far include: (a) Spray demonstration of an electrostatically boosted 501-K gas turbine fuel injector prototype at fuel flows from 40 PPH to 250 PPH. (b) Electrostatic charging effect measurements on the droplet size and patternation of a 501-K simplex atomizer configuration. (c) Numerical modeling of the influence electrostatic charging has on secondary atomization breakup and predicted particulate emissions. This paper documents results associated with injector conceptual design, electrode integration, atomization measurements, numerical modeling and fuel injection system integration. Preliminary results indicate electrostatic boosting may be capable of reducing particulate emissions up to 80% by inserting the appropriate fuel injector.
Development of the Advanced Cycle Low-Power Gas Turbine Alternator (ACL-GTA)
Authors: McCallum Neil R. , English Colin , Watier Bernard
Published: November 2008

The Royal Navy is pursuing the ‘All Electric’ ship under its Marine Engineering Development Strategy. This strategy envisages the use of long life, fuel efficient, advanced cycle marine gas turbine alternator sets in an Integrated Electric Propulsion system, which includes the wide scale electrification of auxiliary systems. In 2000 the UK Ministry of Defence placed a contract on Turbomeca Limited, France, for the development of a 1.8MW advanced cycle gas turbine driving a high speed alternator, providing 800V DC output. The basic design details of this 1.8MW Gas Turbine Alternator (GTA), known as the ACL GTA, was presented at the Turbo Expo 2003 in Atlanta, Georgia. However, since 2003 the design of all the components has been finalised and testing has now commenced on this novel Gas Turbine (GT) technology. The purpose of this paper is to present the first of those test results and describe the final design of the unit on test by constituent parts. These include the bare GT, the recuperator, the directly coupled permanent magnet High Speed Alternator (HSA), its controller the Electronic Unit (EU) and the Monitoring and Control System (MCS). Information will be provided on the individual unit testing and how it is being integrated to ensure project success. The aspects of the design covering control of the power output, self-sustainability and ability to parallel or operate with other diesel generators or GTAs will also be discussed. As an introduction the paper will briefly reiterate the requirement for this GTA and discuss the importance of the commercial business case in conjunction with the military requirements so as to design and build a GTA capable of directly competing with diesel generators.
Three Dimensional Measurements of Instantaneous Flow Field in Corners With Smooth Surfaces Under a Zero Pressure Gradient
Authors: Phillips Michael , Deutsch Steve , Fontaine Arnie , Yavuzkurt Savas
Published: November 2008

Three dimensional instantaneous velocity data were taken in a turbulent corner flow with smooth walls under a zero pressure gradient. Experiments were carried out in air with a free stream velocity of 13 m/s and an axial Reynolds number of about 10,000,000. The data were collected using a three-component LDV system that was configured in a nearly orthogonal setup. Measurements were made down to a y+ of approximately 5, and should provide a valuable data set in developing models and predictive codes. Data were collected at two axial locations, 0.93 and 1.26 m measured from the virtual origin. The boundary layer thickness was 20.90 mm and 24.91 mm respectively at these locations. At each position, instantaneous velocity profiles were measured at 6.35, 12.7, 20.6, 41.2, 82.3, 121.9, 164.5, 184.8, and 205.1 mm from the corner. The centerline profiles agree well with classical flat plate data. Three mean velocity and six Reynolds stress components have been calculated. The instantaneous velocity field data set is sufficient to compute higher order correlations. The data will be valuable for development of computer codes and models for heat transfer studies in the internal cooling channels of gas turbine blades and turbine end wall flow and heat transfer studies. An analysis of the data is presented. Future studies will concentrate on one smooth and one rough wall corner flow with favorable and adverse pressure gradients to provide a detailed database for corner flows in complex three dimensional flow fields.
USNS LCPL Roy M. Wheat: Zorya DT-59 Gas Turbine Installation and Integration
Authors: DeCorso Richard , Caguiat Daniel E. , Patterson Jeffrey S. , Zipkin David M.
Published: November 2008

In June 1997, the U.S. Navy purchased the Soviet military cargo ship “Vladimir Vaslyaev” for conversion to the USNS LCPL Roy M. Wheat for use in the Maritime Prepositioning Force. This paper documents the efforts of NSWCCD and dB Associates in supporting the installation, startup, and integration of the ship’s controls with the two Zorya DT-59 main propulsion gas turbine engines (GTE’s). The installation documentation developed included a video record of the port and starboard gas turbine installations, as well as information that aided in the development of the Engineering Operational Procedures (EOP). The integration for the DT-59s focused on providing engine speed sensors, an engine vibration monitoring system and engine reversing protection circuits.