bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Study of 700-mm Fan Model Noise at CIAM Anechoic Chamber
Authors: Khaletskiy Yuri , Mileshin Victor
Published: November 2013

The results of 700-mm fan model study in terms of acoustic response obtained at the CIAM C-3A test rig anechoic chamber are represented. The fan model is a bypass universal propulsion simulator UPS (bypass ratio 8.5, pressure ratio 1.54, fan tip speed 395 m/s, scaled factor k = 2.7) with one-stage fan and nacelle inside which hush kit may be installed.

At the CIAM test rig C-3A acoustic investigation of the S-2 wide chord fan model was carried out. The results showed that at Runway and Flyover the S-2 fan model noise spectra practically did not differ from the noise spectra of single stage fan models with conventional blades.

At Approach mode the S-2 fan model noise spectra radiated in front hemisphere contains several high level tonal components which could be identified as tonal noise at sum frequencies of rotor interaction with the first booster stage. It should be mentioned, that at Approach mode tonal noise at BPF practically does not exceed the broadband noise.

The UPS noise matrices obtained allowed noise prediction of the hypothetical aircraft equipped with turbofan, the scaled fan model of which was tested.
Investigation of the Effect of Perforated Sheath on Thermal-Flow Characteristics Over a Gas Turbine Reverse-Flow Combustor: Part 2 — Computational Analysis
Authors: Wang Liang , Wang Ting
Published: November 2013

The objective of Part 2 is to employ a computational scheme to investigate the difference in flow pattern, pressure drop, and heat transfer in a gas turbine’s dump diffuser and over the outer surface of the combustor with and without a sheath. Both experimental and computational studies are performed. In Part 1, the experiments are conducted under low pressure and temperature laboratory conditions to provide a database to validate the computation model, which is then used to simulate the thermal-flow field surrounding the combustor and transition piece under elevated gas turbine operating conditions.

For laboratory conditions, the CFD results show that (a) the predicted local static pressure values are higher than the experimental data but the prediction of the global total pressure losses matches the experimental data very well; (b) the total pressure losses are 1.19% for the no-sheath case and 1.89% for the sheathed case, which are within 3% of the experimental values; and (c) the temperature difference between the sheathed and non-sheathed cases is in the range of 5∼10K or 16%–32% based on the temperature scale between the highest and lowest temperature in the computational domain.

In summary, removing the sheath can harvest a significant pressure recovery of approximately 3% of the total pressure, but it will be subject to a wall temperature increase of about 500K (900°F or a 36% increase) on the outer radial part of the transition piece, where the flow is slow due to diffusion and recirculation in the large dump diffuser cavity near the turbine end. If modern advanced materials or coatings could sustain a wall temperature of about 200K higher than those currently available, the shield could be removed with the condition that a special cooling scheme (such as a water spray system) must be applied locally in this region. Otherwise, removal of the shield is not recommended.
Gas Turbine Degradation in the Techno-Economic Environmental and Risk Analysis of Flare Gas Utilization in Nigeria
Authors: Allison Isaiah , Ramsden Kenneth , Pilidis Pericles , Roupa Agbadede
Published: November 2013

There is a wide energy gap in Nigeria: electricity generation meets only about 30% of the required 10000MW; and only about 40% of the installed capacity has been achieved. The Niger Delta region of Nigeria is dominated by oil exploration activities with a conglomeration of flow stations and onshore/offshore platforms that flare gases. This work explores the utilization of flare gas in a gas turbine for electricity, and addresses the impact of flare gas on the turbine hot end components. TurboMatch simulation software is used for design and off-design calculations, while investigating optimistic, slow, medium and fast degradation scenarios.
Power Augmentation Approaches for Mechanical Drive Turbines
Authors: Meher-Homji Cyrus B. , Chaker Mustapha A.
Published: November 2013

Mechanical drive gas turbine can benefit significantly by power augmentation. In the oil and gas, petrochemical and process industries, the reduction in output of mechanical drive gas turbines curtails plant output or throughput. Gas turbines exhibit a drop in power output with an increase in air compressor inlet temperature of the order of 0.7% / °C for heavy duty gas turbines and approximately 1% / °C for aeroderivative turbines. Power augmentation by inlet cooling is an attractive means to minimize production swings. Designing gas turbine driven refrigeration compressors for high ambient temperature swings is also a design challenge due to power limitations at high ambient temperatures and high refrigerant condensing pressures. This paper will address a range of gas turbine inlet cooling techniques, and provide a technical perspective of different inlet cooling approaches.

Technical approaches including inlet evaporative cooling, inlet fogging, wet compression, inlet mechanical and absorption chilling are covered. Other approaches such as water injection are briefly discussed. The judicious selection of the dry bulb temperature and coincident relative humidity for the design and selection of the cooling technology is discussed.
Optimizing Synergy of Utility-Scale Wind and Pumped-Hydro Storage
Authors: Singh A. , Wolff F. , Chokani N. , Abhari R. S.
Published: November 2013

The increased penetration of wind-generated electricity exposes wind farm operators to market risks of a balanced supply in the transmission grid. In order to reduce the risks and to gain financial advantage for wind farm operators, the use of pumped hydro storage to adjust the delivery schedule of energy is proposed. An approach that systematically and rapidly addresses the economic, infrastructural, geographic and meteorological factors relevant to wind power plants and pumped hydro storage over large areas is required. An integrated Geographic Information System-based tool is developed to identify, on the scale of a country, wind power plants and pumped hydro storage facilities. Further, a decision algorithm that has inputs of the forecasted and actual wind energy productions, and the day-ahead and intraday electricity market prices is also developed to optimise the use of pumped hydro storage. This approach is demonstrated for Germany, with the target of increasing electricity production from renewable energy sources. A countrywide portfolio of wind power plants that meets the increased electricity production target, and existing and potential pumped hydro storage facilities are identified. By optimizing the use of pumped hydro storage, it is shown that wind farm operators can achieve a 2–4% gain on the Internal Rate of Return on investments. The improved financial performance with the use of pumped hydro storage increases the attractiveness for investments in the wind power sector and mitigates the adverse effects of the variability in the dispatch of wind-generated electricity.
A Study on the Performance of Steam Injection in a Typical Micro Gas Turbine
Authors: De Paepe Ward , Delattin Frank , Bram Svend , Contino Francesco , De Ruyck Jacques
Published: November 2013

Microturbines are very promising for small-scale Combined Heat and Power (CHP) production. Due to the simultaneous production of heat and power, the Turbec T100 microturbine CHP System has the potential of realizing considerable energy savings, compared to classic separate production. The power production however is strictly bound to the heat production. A reduction in heat demand will mostly lead to a shutdown of the unit, since electric efficiency is too low and not competitive with electricity from the net. The reduced amount of running hours has a severe negative impact on the lifetime profitability of the unit. A solution is proposed by injecting auto-generated steam in the T100 micro Gas Turbine (mGT), in order to increase electric efficiency during periods with low heat demand. By doing so, a forced shut down of the unit can be avoided.

The goal of this study was to investigate and quantify the beneficial effect of steam injection on the performance of a typical recuperated mGT. This paper reports on an extended series of steam injection experiments performed on a Turbec T100 microturbine. Previous experiments revealed the necessity for a more accurate determination of the mass flow rate and more precise compressor characteristics. Therefore the test rig was equipped with an additional oxygen analyzer in the exhaust and a pressure gauge to allow for the accurate determination of the pressure ratio. Experiments with steam injection in the compressor outlet of the T100 were performed to demonstrate and validate the benefits of introducing steam in the cycle and to verify its ability to handle the injected steam. It is expected that the mGT will produce a constant power at reduced shaft speed and increased electric efficiency.

Steam injection experiments validated the increase in electric efficiency during stable operation of the mGT. At nominal 100 kWe power production, the replacement of 3.5% of the air mass flow with steam (adiabatic steam injection limit) resulted in an absolute electric efficiency increase of 1.7%. The experiments successfully demonstrated the potential for steam/water injection in the T100 mGT.
An Improved Catcher Bearing Model and an Explanation of the Forward Whirl/Whip Phenomenon Observed in Active Magnetic Bearing Transient Drop Experiments
Authors: Wilkes Jason , Vannini Giuseppe , Moore Jeff , Ransom David
Published: November 2013

Though many approaches have been proposed in the literature to model the reaction forces in a catcher bearing (CB), there are still phenomena observed in experimental tests that cannot be explained by existing models. The following paper presents a novel approach to model a CB system. Some of the elements in the model have been previously introduced in the literature; however, there are other elements in the proposed model that are new, providing an explanation for the forward whirling phenomena that has been observed repeatedly in the literature. The proposed CB model is implemented in a finite element rotordynamic package, and nonlinear time-transient simulations are performed to predict published experimental results of a high speed vertical sub-scale compressor; with no other forces present in the model, the agreement between simulations and experimental data is favorable.

The results presented herein show that friction between the journal and axial face of the catcher bearing results in a forward cross-coupled force that pushes the rotor in the direction of rotation. This force is proportional to the coefficient of friction between the axial face of the rotor and catcher bearing and the axial thrust on the rotor. This force results in synchronous whirl when the running speed is below a combined natural frequency of the rotor-stator system, and constant frequency whip when the speed is above a whip frequency.
A Rothalpy Analysis for the Isothermal Boundary Condition at Casing Applied to the Rotor 37 Transonic Axial Flow Compressor
Authors: Bruna Dario , Turner Mark G.
Published: November 2013

CFD simulations have been set-up with an isothermal boundary condition at the casing for running the NASA Rotor 37 axial compressor. The casing temperature was set to the inlet total temperature. The comparison to data was much improved for the efficiency for the 100% speed line relative to the adiabatic simulations. The efficiency difference between the isothermal and adiabatic solutions is about 1%, with the isothermal calculation matching the low flow test condition. The profiles of total temperature with the isothermal boundary condition matched the data near the casing without any overshoot, typical of most compressor calculations. Also the efficiency profile had a similar improvement in matching the data because of its relationship to temperature.

A similar comparison between isothermal and adiabatic cases has been carried out for the same geometry with double the design clearance. The working range based on the steady CFD calculations is about half that of the design clearance case which is felt to be realistic.

Moreover a detailed analysis based on conservation of Rothalpy has been made and applied to the rotor. Mass averaged Rothalpy is not conserved due to a frictional power term associated with the stationary case as well as heat transfer. The effects of these terms show the extent of the heat transfer is between 10–20% of span away from the casing.

The heat transfer effect calculated with the isothermal boundary condition simulation is thought to be real, and accounting for it matches data better than using an adiabatic assumption. However, the real rig would probably not be isothermal at the casing and may require more complex simulations such as a conjugate heat transfer approach.
Rotor Dynamic Modeling of Gears and Geared Systems
Authors: Kaplan Jason A. , Dousti Saeid , Allaire Paul E. , Nichols Bradley R. , Dimond Timothy W. , Untaroiu Alexandrina
Published: November 2013

The ability to accurately predict rotating machine resonant frequencies and to assess their stability and response to external forces is crucial from a reliability and preventive maintenance perspective. Resonant frequencies and forced response become more difficult to predict when additional complicated components such as gearboxes are present in the rotor system. Gearbox dynamics contain many complex interactions and many of the simplifying assumptions provided in the literature do not apply to most geared systems. A finite element formulation of the gearbox, which couples the axial, lateral, and torsional degrees-of-freedom of the low and high-speed shafts, is developed. It has the capability to apply to a wide variety of both spur and helical geared systems and is sufficiently robust to account for arbitrary orientation angles between the parallel shafts. This study presents a rotor dynamic analysis of an industrial drive-train consisting of a steam turbine, herringbone gearbox, and a generator using 1-D Timoshenko beam elements. The rotor dynamic analysis consists of the calculation of the damped natural frequencies, mode shapes, and provides insight into the stability of the industrial drive-train.
Influence of Partial Admission on the Downstream Stages of a Reaction Turbine: An Analytical Approach Verified by Measurements
Authors: Beer Wolfgang , Hirsch Peter
Published: November 2013

Field measurements on an industrial steam turbine with a rated power output of 5.8 MW, consisting of an impulse type control wheel and a reaction part, showed a significant gap of efficiency from the design calulations. It was suspected, that this gap results from underestimation of the loss created by non-uniform inflow conditions to the reaction part due to partial admission. The experimental results and data of experiments done in the 1990s are therefore recalculated to find possible explanations. It turns out, that probably the data considered for verifcation is not complete. When taking the complete data into account, and using an averaging method, the verification calculations show, that the models used for design and recalculation of industrial steam turbines are accurate enough for industrial purposes, but a calculation model for efficiency loss due to partial admission has to be added. In this work non-uniformity between the flow passages was not observed for the test turbine. Non-uniformity of the flow in radial direction was observed for the test turbine, but was not taken into consideration here, as the whole rotor was treated integrally. Flow seperations as unsteady effects were not considered, as a steady-state investigation was conducted.

The calculation models are verified by comparison with field measurement data from industrial steam turbines, by comparison with the results of a 9 MW steam driven test turbine and by recalculated results from literature. Not all verification calculations are presented in detail here.
Experimental and Numerical Investigation of Inflow Turbulence on the Performance of Wind Turbine Airfoils
Authors: Eisele O. , Pechlivanoglou G. , Nayeri C. N. , Paschereit C. O.
Published: November 2013

Wind turbine blade design is currently based on the combination of a plurality of airfoil sections along the rotorblade span. The two-dimensional airfoil characteristics are usually measured with wind tunnel experiments or computed by means of numerical simulation codes. The general airfoil input for the calculation of the rotorblade power characteristics as well as the subsequent aerodynamic and aeroelastic loads are based on these two-dimensional airfoil characteristics. In this paper, the effects of inflow turbulence and wind tunnel test measurement deviations are investigated and discussed, to allow considerations of such effects in the rotorblade design process. The results of CFD simulations with various turbulence models are utilized in combination with wind tunnel measurements in order to assess the impact of such discrepancies. It seems that turbulence, airfoil surface roughness and early transition effects are able to contribute significantly to the uncertainty and scattering of measurements. Various wind tunnel facilities generate different performance characteristic curves, while grid-generated turbulence is generally not included in the wind tunnel measurements during airfoil characterization. Furthermore the correlation of grid-generated wind tunnel turbulence with the atmospheric turbulence time and length scales is not easily achieved. All the aforementioned uncertainties can increase the performance scattering of current wind turbine blade designs as well as the generated aeroelastic loads. A brief assessment of the effect of such uncertainties on wind turbine performance is given at the last part of this work by means of BEM simulations on a wind turbine blade.
Experimental Investigation on Aerodynamic Behavior of a Compressor Cascade in Droplet Laden Flow
Authors: Ober Birger , Joos Franz
Published: November 2013

The possibility to augment the power output of gas turbines by the use of water injection becomes more and more attractive in recent years as unsteadily available renewable energy sources become more present and the need of reserve power rises. Depending on the installed system, water injection may result in a two phase flow inside the compressor. The water droplet laden compressor flow promises benefits in efficiency and to some extent in performance and stability. The thermodynamic aspect has been thoroughly investigated as summarized by Eisfeld [1]. A promising approach is the stabilizing influence on highly stressed airfoils as experimentally investigated by Eisfeld and Joos [2] who conducted first systematic experimental investigations but were limited in the range of incidence angles. Multiple numerical investigations have been undertaken by different research groups which found similar results (e.g. Sun et al in [3]). The ongoing experimental investigation presented in this paper focuses on the influence of a droplet laden flow on an axial compressors aerodynamics over the range of relevant incidence flow angles. The result of the series of experiments is a comparison of a dry air compressor flow and a droplet laden air compressor flow at high velocity (Ma > 0.85). The variables were water load and incidence angle. The discussion will investigate the effects of the presence of water droplet on the compressor cascades discharge flow properties and their influence on the relevant performance parameters. For this a discussion of the loss coefficient the detailed discharge flow velocity and the axial velocity density ratio (AVDR) will take place.
Study of Steady State and Transient Blade Row CFD Methods in a Moderately Loaded NASA Transonic High-Speed Axial Compressor Stage
Authors: Qizar Mohammed Abdullah , Mansour Mahmoud L. , Goswami Shraman
Published: November 2013

The effect of blade row interaction and hub leakage flow on the performance of moderately loaded NASA transonic hybrid compressor stage (Rotor 35 / Stator 37) is investigated through three-dimensional steady state and time-accurate, Navier Stokes calculations of the stage using the ANSYS CFX code at peak efficiency and near stall operating conditions. Understanding unsteady flow phenomena in compressor stages requires the use of time-accurate CFD simulations. Due to the inherent differences in blade counts between adjacent blade rows, the flow conditions at any given instant in adjacent blade rows differ. Depending on the blade counts, it may be necessary to model the entire annulus of the stage; however, this requires considerable computational time and memory resources.

Several methods for modeling the transient flow in turbo machinery stages which require a minimal number of blade passages per row, and therefore reduced computational demands, have been presented in the literature. Recently, some of these methods have become available in commercial CFD solvers. The paper describes the steady and the unsteady CFD approaches used for investigating the ability to predict the measured performance of the NASA transonic axial stage design known as the hybrid stage, which consists of the axial Rotor35 and the axial stator 37. The steady approach employs the mixing-plane while the unsteady approaches are URANS with one based on full annulus simulation for the stage and the second enables simulations for the stage using reduced computational model, with a single passage from each blade row based on the time-tilting or the time-transformation technique.

The above methods are evaluated and compared in terms of computational efficiency and comparison is made to steady stage simulations. Comparisons to overall performance data and two-dimensional Laser Doppler Velocimeter measurements of the velocity field are used to assess the predictive capabilities of the methods. Computed flow features are examined, and compared with reported measurements. This paper presents validation and calibration of methods used for determining blade row interactions and the respective predictive capabilities against the full annulus and the experimental test data.
Deterministic Stress Modeling for Multistage Compressor Flowfields
Authors: Stollenwerk Stefan , Kügeler Edmund
Published: November 2013

Unsteadiness is one of the main characteristics in turbomachinery flows. Local unsteady changes in static pressure must exist within a turbo-machine in order for that machine to exchange energy with the fluid. The primary reason for unsteady effects lies in the interaction between moving and stationary blade rows. The industrial design process of aero-engines and gas turbines is still based on Reynolds-averaged Navier-Stokes (RANS) techniques where the coupling of blade rows is carried out by mixing-planes. However, this methodology does not cover deterministic unsteadiness in an adequate way. For standard aero-optimization, detailed unsteadiness is not essential to the designer of turbomachines but rather its effect on the time averaged solution. The time averaged deterministic unsteadiness can be expressed in terms of deterministic stresses. The present paper presents two different modeling strategies for deterministic stresses that constitute an improvement of the conventional steady mixing-plane approach. Whilst one of the presented models operates with deterministic flux terms based on preliminary unsteady simulations, the other one, a novel transport model for deterministic stress, is a stand-alone approach based on empirical correlations and a wide range of numerical experiments. A 4.5 stage transonic compressor is analyzed regarding blade row interaction effects and their impact on the time averaged solution. The two models are applied to the compressor and their solutions are compared to conventional mixing-plane, time accurate and experimental data. The results for the speedline, the wake shapes, the radial distributions and the rotor blade loadings show that the deterministic stress models strongly improve the RANS solution towards the time accurate and the experimental methods.
An Off-Design Performance Prediction Model for Low-Speed Double-Discharge Centrifugal Fans
Authors: Wolfe Tristan , Lee Yu-Tai , Slipper Michael E.
Published: November 2013

A generalized model for mapping the trend of the performance characteristics of a double-discharge centrifugal fan is developed based on the work by Casey and Robinson (C&R) which formulated compressor performance maps for tip-speed Mach numbers ranging from 0.4 to 2 using test data obtained from turbochargers with vaneless diffusers. The current paper focuses on low-speed applications for Mach number below 0.4. The C&R model uses four non-dimensional parameters at the design condition including the flow coefficient, the work input coefficient, the tip-speed Mach number and the polytropic efficiency, in developing a prediction model that requires limited geometrical knowledge of the centrifugal turbomachine. For the low-speed fan case, the C&R formulas are further modified to apply a low-speed, incompressible analysis.

The effort described in this paper begins by comparing generalized results using efficiency data obtained from a series of fan measurements to that using the C&R model. For the efficiency map, the C&R model is found to heavily depend on the ratio of the flow coefficient at peak efficiency to that at the choke flow condition. Since choke flow is generally not applicable in the low-speed centrifugal fan operational environment, an alternate, but accurate estimation method based on fan free delivery derived from the fan test data is presented. Using this new estimation procedure, the modified C&R model predicts reasonably well using the double-discharge centrifugal fan data for high flow coefficients, but fails to correlate with the data for low flow coefficients. To address this undesirable characteristic, additional modifications to the C&R model are also presented for the fan application at low flow conditions.

A Reynolds number correction is implemented in the work input prediction of the C&R model to account for low-speed test conditions. The new model provides reasonable prediction with the current fan data in both work input and pressure rise coefficients. Along with the developments for the efficiency and work input coefficient maps, the use of fan shut-off and free delivery conditions are also discussed for low-speed applications.
Materials Considerations for Supercritical CO2 Turbine Cycles
Authors: Wright I. G. , Pint B. A. , Shingledecker J. P. , Thimsen D.
Published: November 2013

Proposed open and closed Brayton-type cycle systems employing supercritical CO2 (sCO2) as the working fluid develop hot gas path environments that present challenging requirements of strength and environmental resistance for the materials of construction. The likely materials properties required by different cycle configurations are examined and compared with the capabilities of available materials. In some instances where peak operating conditions in the turbines in closed-cycle systems approach 500°–700°C at 200 bar, or 1150°C at 300 bar for open cycles, the range of available alloys with the requisite temperature-strength and capabilities is limited.

The cycles are highly recuperated: hot, lower-pressure turbine exhaust is used to pre-heat high-pressure CO2 entering the external heater or combustor just upstream of the turbine. Obviously, there is a need to match alloy capabilities with the performance requirements of individual components. Where alloys are employed under conditions beyond current experience, or in unusual configurations (the unique properties of sCO2 may impact the design of some components), practical acceptance will depend on successful qualification testing involving close collaboration among equipment manufacturers, materials suppliers, and materials research and development groups.

Examination of the range of scenarios published for sCO2 turbine systems suggests that approaches used in the U.S. Advanced, Ultra-Supercritical (A-USC) Steam Boiler program, and some of the data generated for fabrication, joining, mechanical properties, and performance in simulated service environments in that program, will be applicable to some of the components in these systems. An attempt to elaborate and prioritize the materials property and qualification activities required for the successful realization of these sCO2 cycles is presented as a guide to activities needed to facilitate materials selection.
Aerodynamic Loss for a Turbine Blade With Endwall Leakage Features and Contouring
Authors: Lynch Stephen P. , Thole Karen A. , Kohli Atul , Lehane Christopher , Praisner Tom
Published: November 2013

Secondary flows near the endwall of a turbine blade contribute to a loss in aerodynamic performance in the engine. Further reductions in performance occur when the secondary flows interact with leakage flow from necessary clearance features, such as the clearance gap between the blade rotor and an upstream stator or gaps between adjacent blade platforms. Non-axisymmetric endwall contouring has been shown to reduce the strength of secondary flows near the endwall, but relatively little research has been done to test the sensitivity of the contouring to the endwall leakage features. This paper describes aerodynamic measurements taken downstream of a cascade with representative leakage features. In general, upstream leakage flow with swirl relative to the blade increased aerodynamic loss, relative to leakage that was matched to the blade wheelspeed. Non-axisymmetric contouring for an endwall without a platform gap reduced underturning of the flow but had no effect on overall loss, relative to a flat endwall without a gap. A contoured endwall with a platform gap had 12% higher mixed-out loss than a contoured endwall without a gap.
Axial-Slot Casing Treatments Improve the Efficiency of Axial Flow Compressors: Aerodynamic Effects of a Rotor Redesign
Authors: Streit J. Anton , Heinichen Frank , Kau Hans-Peter
Published: November 2013

A state-of-the-art transonic compressor rotor has a distinct potential for increased efficiency if modified for improved interaction with an axial-slot type casing treatment. Reducing the number of blades and thus the surface lowers friction losses but increases tip clearance effects and deteriorates the stall margin due to the higher aerodynamic blade loading. The latter two negative effects can be compensated for by the casing treatment, thus restoring the required stall margin and gaining an overall reduction of losses. For the specific compressor rotor under investigation, the potential in polytropic efficiency is as high as 0.7%.

The present study was performed using time-accurate CFD (URANS) simulations. Both the reference rotor as well as the modified design are analyzed regarding their interaction with the casing treatment. The traceability of the conclusions is assured by interpreting the detailed flow phenomena. The newly designed rotor is found to be favorably influenced by the casing treatment at design operating conditions whilst the reference only benefits at throttled operating points.

Casing treatments are commonly used to broaden the operating range of existing compressors without changing the design of the compressor rotor itself. This study aims to show the possible transformation of this potential in the stall margin into efficiency at design operating conditions by implementing an appropriate rotor design.
Fanno Design of Blow-Off Lines in Heavy Duty Gas Turbine
Authors: Cioffi Marco , Puppo Enrico , Silingardi Andrea
Published: November 2013

In typical heavy duty gas turbines the multistage axial compressor is provided with anti-surge pipelines equipped with on-off valves (blow-off lines), to avoid dangerous flow instabilities during start-ups and shut-downs. Blow-off lines show some very peculiar phenomena and somewhat challenging fluid dynamics, which require a deeper regard. In this paper the blow-off lines in axial gas turbines are analyzed by adopting an adiabatic quasi-unidimensional model of the gas flow through a pipe with a constant cross-sectional area and involving geometrical singularities (Fanno flow). The determination of the Fanno limit, on the basis of the flow equation and the second principle of thermodynamics, shows the existence of a critical pipe length which is a function of the pipe parameters and the initial conditions: for a length greater than this maximum one, the model requires a mass-flow reduction. In addition, in the presence of a regulating valve, so-called multi-choked flow can arise. The semi-analytical model has been implemented and the results have been compared with a three-dimensional CFD analysis and cross-checked with available field data, showing a good agreement. The Fanno model has been applied for the analysis of some of the actual machines in the Ansaldo Energia fleet under different working conditions. The Fanno tool will be part of the design procedure of new machines. In addition it will define related experimental activities.
Modelling and Validation of the Nonlinear Dynamic Behaviour of Bolted Flange Joints
Authors: Schwingshackl C. W. , Di Maio D. , Green J. S.
Published: November 2013

Linear dynamic finite element analysis can be considered very reliable today for the design of aircraft engine components. Unfortunately, when theses individual components are built into assemblies, the level of confidence in the results is reduced, since the joints in the real structure introduce nonlinearity that cannot be reproduced with a linear model. Certain types of nonlinear joints in an aircraft engine, such as underplatform dampers and blade roots, have been investigated in great detail in the past, and their design and impact on the dynamic response of the engine is now well understood. With this increased confidence in the nonlinear analysis, the focus of research now moves towards other joint types of the engine which must be included in an analysis to allow an accurate prediction of the engine behaviour.

One such joint is the bolted flange, which is present in many forms on an aircraft engine. Its main use is the connection of different casing components to provide the structural support and gas tightness to the engine. This flange type is known to have a strong influence on the dynamics of the engine carcase. A detailed understanding of the nonlinear mechanisms at the contact is required to generate reliable models and this has been achieved through a combination of an existing non-linear analysis capability and an experimental technique to accurately measure the nonlinear damping behaviour of the flange. Initial results showed that the model could reproduce the correct characteristics of flange behaviour, but the quantitative comparison was poor. From further experimental and analytical investigations it was identified that the quality of the flange model is critically dependent on two aspects: the steady stress/load distribution across the joint and the number and distribution of non-linear elements. An improved modelling approach was developed which led to a good correlation with the experimental results and a good understanding of the underlying nonlinear mechanisms at the flange interface.
Synthetic Sound Source Generation for Acoustical Measurements in Turbomachines
Authors: Bartelt Michael , Laguna Juan D. , Seume Joerg R.
Published: November 2013

One of the greatest challenges in modern aircraft propulsion design is the reduction of the engine noise emission in order to develop quieter aircrafts. In the course of a current research project, the sound transport in low pressure turbines is investigated. For the corresponding experimental measurements, a specific acoustic excitation system is developed which can be implemented into the inlet of a turbine test rig and into an aeroacoustic wind tunnel. This allows for an acoustic mode generation and a synthesis of various sound source patterns to simulate typical turbomachinery noise sources such as rotor-stator interaction, etc. The paper presents the acoustical and technical design methodology in detail and addresses the experimental options of the system. Particular attention is paid to the design and the numerical optimization of the acoustic excitation units. To validate the sound generator during operation, measurements are performed in an aeroacoustic wind tunnel. For this purpose, an in-duct microphone array with a specific beamforming algorithm for hard-walled ducts is developed and applied to identify the source locations. The synthetically excited sound fields and the propagating acoustic modes are measured and analyzed by means of modal decomposition techniques. The measurement principles and the results are discussed in detail and it is shown that the intended sound source is produced and the intended sound field is excited. This paper shall contribute to help guide the development of excitation systems for aeroacoustic experiments to better understanding the physics of sound propagation within turbomachines.
An Approach to Detect and Mitigate Ice Particle Accretion in Aircraft Engine Compression Systems
Authors: May Ryan D. , Guo Ten-Huei , Simon Donald L.
Published: November 2013

The accretion of ice in the compression system of commercial gas turbine engines operating in high ice water content conditions is a safety issue being studied by the aviation sector. While most of the research focuses on the underlying physics of ice accretion and the meteorological conditions in which accretion can occur, a systems-level perspective on the topic lends itself to potential near-term operational improvements. This work focuses on developing an accurate and reliable algorithm for detecting the accretion of ice in the low pressure compressor of a generic 40,000 lbf thrust class engine. The algorithm uses only the two shaft speed sensors and works regardless of engine age, operating condition, and power level. In a 10,000-case Monte Carlo simulation, the detection approach was found to have excellent capability at determining ice accretion from sensor noise with detection occurring when ice blocks an average of 6.8% of the low pressure compressor area. Finally, an initial study highlights a potential mitigation strategy that uses the existing engine actuators to raise the temperature in the low pressure compressor in an effort to reduce the rate at which ice accretes.
Design and Commissioning of an Engine-Like Test Environment
Authors: Laing Malcolm , Pickering Todd , Kominsky Dan , O’Brien Walter , Poland Steve
Published: November 2013

Test and evaluation are critical to any product development program. The validation of engine sensor products is particularly challenging since the test engine required for validation can range in value from thousands to millions of dollars, costing much more than the sensor product itself. As a result, significant sensor testing and validation is required by an engine owner prior to on-engine testing. To support our development activities and to facilitate test validation acceptance, we have created a test and evaluation platform for gas turbine sensors that will allow us to test developmental sensors in an engine-like environment without risking the possibility of engine damage. Driven by the core exhaust of a JT15-D engine, the Dynamic Rotor Research Rig (DR3) test and evaluation platform provides a test capability that is highly representative of the high temperatures, vibrations, gasses, fluids and overall gas turbine engine environment, while providing the means to easily add and replace sensors, add and test custom rotors, control temperature and rotor speeds, and to not risk engine health during test activities.

Here we will discuss our sensor testing goals and how they fed into the operational goals and design considerations for the DR3. Early design concepts and the ultimate approach we took with the DR3 design will be explored, along with the candidate test rig component and subassembly fabrication processes that we evaluated and ultimately selected for use. We will review the manufacturing issues that we encountered during the construction phase of the DR3 and overview the commissioning of the DR3, problems that we discovered during start up and how we solved them.

Included will be the results of initial turbine blade clearance and blade tip timing sensor testing performed on the DR3 and an evaluation of the DR3 performance, including temperature and speed control of the test rig and other characterization of the operating regime of the rig. Finally, we will present future plans to upgrade the DR3 rig to support future high temperature sensor and blade health monitoring development activities.
Turbomachinery for a Supercritical CO2 Electro-Thermal Energy Storage System
Authors: Fuller R. , Hemrle J. , Kaufmann L.
Published: November 2013

This paper presents analysis of CO2 turbomachinery for the electro-thermal energy storage (ETES) concept for site-independent bulk (grid-scale) electric energy storage. In charging mode, ETES operates as a transcritical CO2 heat pump, consuming electric energy which is converted into thermal energy stored in the form of hot water and ice on the hot and cold side of the cycle, respectively. On demand, the CO2 cycle is reversed for discharging during which ETES operates as transcritical CO2 power generation plant, consuming the stored hot and cold sources. The target capacity of the ETES system is of the order of units of MW electric to ∼100 MW electric, with typical daily cycles and 4 to 8 hours of storage. The estimated electric-to-electric round trip efficiency of ETES is about 60%.

A companion paper [1] presents the control concept of the ETES plant and discusses several issues specific to the ETES plant design and operation. This paper analyzes these particular requirements from the perspective of the CO2 turbomachinery required for the storage plant, presenting the selection of the turbomachinery types and their shaft arrangement suitable for the ETES. The expected performance, main design features and challenges are discussed, together with questions related to the scalability of the turbomachines towards high power targets. Impacts of the turbomachinery designs on the ETES system performance, such as the sensitivity of the system electric-to-electric round trip efficiency on the turbomachinery efficiency are discussed.
An Optimal Automated Zone Allocation Approach for Risk Assessment of Gas Turbine Engine Components
Authors: Moody Jonathan P. , Enright Michael P. , Liang Wuwei
Published: November 2013

High-energy rotating components of gas turbine engines may contain rare material anomalies that can lead to uncontained engine failures. The Federal Aviation Administration and the aircraft engine industry have been developing enhanced life management methods to address the rare but significant threats posed by these anomalies. One of the outcomes of this effort has been a zone-based risk assessment methodology in which component fracture risk is estimated using groupings of elements called zones that are associated with 2D finite element (FE) stress and temperature models. Previous papers have presented processes for creation of zones either manually or via an automatic algorithm in which zones are assigned to each finite element in a component model. These processes may require significant human time and computer time. The focus of this paper is on the optimal allocation of multiple finite elements to zones that minimizes the total number of zones required to compute the fracture risk of a component. An algorithm is described that uses a relatively coarse response surface method to estimate the conditional risk value at each node in a finite element model. Zones are initially defined for each finite element in the model, and the algorithm identifies and merges zones based on minimizing the influence on component risk. The process continues until all of the zones have been merged into a single zone. The zone sequence is applied in reverse order to identify the minimum number of zones that satisfies component target risk or convergence threshold constraints. This solution provides the optimal allocation of finite elements to zones. The algorithm is demonstrated for a representative gas turbine engine component. The approach significantly improves the computational efficiency of the zone-based risk analysis process.
Application of the Multi-Axial Creep Failure Method on Double Reheat Thermodynamic Cycle Turbine
Authors: Chen Gang , Jiang Puning , Wang Yuxiang , Hao Zhenzhen
Published: November 2013

With the development of higher efficiency and lower consumption plants, higher steam parameters to 600/620/620°C and 33/10.6/3.5MPa and double reheat thermodynamic cycle system are adopted for the power plant. Thus, it is believed that the safety of high temperature components in the steam turbine system is a critical issue that could not be circumvented in the period of modern industrial development. To achieve a reliable design, manufacture and the desired long-term operation of the high temperature components in steam turbine, many fundamental research concerning design criteria and life prediction has been studied. However, for the steam turbine original equipment manufacturer (OEM) which design criteria and life prediction model are suitable for their product and how to accurately assess the components’ life under long-term operation is still a critical issue. For all confronted problems, the multi-axial creep failure is one of the major problems in the life prediction for high temperature components, and it is an important factor to be considered in the high temperature components design.

In this paper, the creep failure mechanisms of high temperature components in steam turbine which under multi-axial stress states are analyzed, and the design criteria for creep strain and stress are presented which are based on cavity growth theory. The application of the method and design criteria in a medium pressure turbine which is included in a double reheat thermodynamic cycle plant is presented.
The Impact of Centre Body Alignment to Flow Through an Annular Diffuser
Authors: Cerantola D. J. , Birk A. M.
Published: November 2013

Cold air-flow testing was completed over a range of inlet Reynolds numbers of 0.8–3.5 × 105 on several annular diffuser designs to quantify the variation in first order statistics due to misalignment. The procedure involved in attaching the outer duct wall caused a maximum 5% axis shift with respect to the outlet diameter at the diffuser outlet relative to the centre body axis and translated to an approximate inlet variation in height of 2%. This shift was sufficient to distort the flow whereby the quadrant with the greater area at the annular diffuser inlet corresponded to higher total pressure at the outlet. Results showed that static pressure coefficient never varied by more than 3.8% and the outlet velocity uniformity coefficient stayed within 2.4% from reference configurations; however, total pressure coefficient had a larger variation in some cases greater than 10%.