bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Evaluation of Compressor Blade Fouling
Authors: Kurz Rainer , Musgrove Grant , Brun Klaus
Published: September 2016

Fouling of compressor blades is an important mechanism leading to performance deterioration in gas turbines over time. Experimental and simulation data are available for the impact of specified amounts of fouling on performance, as well as the amount of foulants entering the engine for defined air filtration systems and ambient conditions.

This study provides experimental data on the amount of foulants in the air that actually stick to a blade surface for different conditions of the blade surface. Quantitative results both indicate the amount of dust as well as the distribution of dust on the airfoil, for a dry airfoil, as well as airfoils that were wet from ingested water, as well as different types of oil. The retention patterns are correlated with the boundary layer shear stress. The tests show the higher dust retention from wet surfaces compared to dry surfaces. They also provide information about the behavior of the particles after they impact on the blade surface, showing that for a certain amount of wet film thickness, the shear forces actually wash the dust downstream, and off the airfoil. Further, the effect of particle agglomeration of particles to form larger clusters was observed, which would explain the disproportional impact of very small particles on boundary layer losses.
The Design and Testing of a Low Reaction Turbine Blade Profile for HP and IP Steam Flow Path
Authors: Deng Guoliang , Sun Qi , Wu Qilin , Fan Xiaoping , Yin Mingyan , Tian Chaoyang , Ping Yan
Published: September 2016

The design of a low reaction turbine blade profiles was carried out to improve the steam flow efficiency. The blade profiles geometry design for both the stationary and moving blades and reprofiling of them are done using Vista ATBlade, according to the aerodynamic analysis results from the cascade analysis code MISES.

The original stator profile is aft-loaded, and the new one present in this paper is highly-aft-loaded (HAL) to depress the development of secondary flow further, while maintaining even lower profile loss and wider incidence angle tolerance. The newly designed moving blade is more robust compared with the original one, thus it has larger aspect ratio under the same blade section average stress level, and with better incidence tolerant capability as well.

The planar cascade air tests were first carried out to verify the stator profile loss improvement, with a decrease of energy loss coefficient of almost 0.8% obtained under the Reynolds number of about 1e6. Then the annular cascade air tests with fully 360 degrees stator blades installed were conducted to validate the reduction of endwall loss and the profile loss as well, and to measure the mass flow capability (real mass flow/ideal mass flow).

Finally, two three-stage tests for the original blades and the new one were developed to verify the improvement under real multi-stages flow conditions. All the stages for both tests are designed with the hub reaction of about 15%, without interstage swirl, in the design condition. The flow probes at upstream of first stage stator and downstream of last stage moving blade, the hydraulic dynamometer and the flowmeter are used to test the overall efficiency. Three traverse planes are located at the upstream, middle and downstream of the second stage to measure the flow properties using five hole pneumatic probes. The test results showed a increase of overall efficiency of about 1.5%.

The CFD simulations showed very good agreement of mass flow capability with the tests, for both the stator annular and multi-stage tests.

The application of the newly designed blade profiles in SanHe subcritical reheat 300MW steam turbine (16.7MPa/537°C/537°C) retrofit gives the final proof of the efficiency improvement. The measured efficiency showed remarkable performance, with an increase of efficiency of 1.5%–2.2% for both the HP and IP cylinder.
Steady-State Power Operation of a Supercritical Carbon Dioxide Brayton Cycle With Thermal-Hydraulic Control
Authors: Clementoni Eric M. , Cox Timothy L. , King Martha A.
Published: September 2016

The Bechtel Marine Propulsion Corporation (BMPC) Integrated System Test (IST) is a two shaft recuperated closed Brayton cycle using supercritical carbon dioxide (sCO2) as the working fluid. The IST is a simple recuperated Brayton cycle with a variable speed turbine driven compressor and a constant speed turbine driven generator designed to output 100 kWe. The main focus of the IST is to demonstrate operational, control, and performance characteristics of an sCO2 Brayton power cycle over a wide range of conditions.

IST operation has reached the point where the system can be run with the turbine-compressor thermal-hydraulically balanced so that the net power of the cycle is equal to the turbine-generator output. In this operating mode, power level is changed by using the compressor recirculation valve to adjust the fraction of compressor flow that goes to the turbines as well as the compressor pressure ratio. Steady-state operational data and trends are presented at various system power levels from near zero net cycle power to maximum operating power using a simplified thermal-hydraulic based control method. Confirmation of stable steady-state operation of the system with automatic thermal-hydraulic control is also discussed.
On the Effect of Axial Spacing Between Rotor and Stator Onto the Blade Vibrations of a Low Pressure Turbine Stage at Engine Relevant Operating Conditions
Authors: Marn Andreas , Schönleitner Florian , Mayr Mathias , Selic Thorsten , Heitmeir Franz
Published: September 2016

In order to achieve the ACARE targets regarding reduction of emissions, it is essential to reduce fuel consumption drastically. Reducing engine weight is supporting this target and one option to reduce weight is to reduce the overall engine length (shorter shafts, nacelle). However, to achieve a reduction in engine length, the spacing between stator and rotor can be minimised, thus changing the rotor blade excitation. Related to the axial spacing, a number of excitation mechanisms with respect to the rotor blading must already be considered during the design process. Based on these facts several setups have been investigated at different engine relevant operating points and axial spacing between the stator and rotor in the subsonic test turbine facility (STTF-AAAI) at the Institute for Thermal Turbomachinery and Machine Dynamics at Graz University of Technology. In order to avoid upstream effects of supporting struts, these struts are located far downstream of the stage which is under investigation. For rotor blade vibration measurements, a novel telemetry system in combination with strain gauges is applied. To the best of the author’s knowledge, the present paper is the first report of blade vibration measurements within a rotating system in the area of low pressure turbines under engine relevant operating conditions. In addition, aerodynamic measurements including unsteady flow measurements have been conducted, but will not be presented in this paper. By analysing the flow field, aerodynamic excitation mechanisms can be identified and assigned to the blade vibration. However, this is not presented in this paper. Within this paper, the flow fields are analysed in both upstream and downstream of the turbine stage, visualised for two axial gaps and then compared to the forced response of the blading. Detailed structural dynamic investigations show critical modes during the operation which are identified by the telemetry measurements as well. Finally the influence of the axial spacing regarding the rotor blade excitation and vibration can be elaborated and is prepared to get a better understanding of basic mechanisms. The paper shows that reducing axial spacing is a promising option for reducing engine weight, but aeroelasticity must be carefully taken into account.
Alleviation of Rotating Pressure Oscillations in the Last LP Turbine Stage During Low-Load Conditions
Authors: Haller B. R. , Rice T. S. , Sigg R.
Published: September 2016

In Steam Turbines, under low flow conditions, the flow structure on the long last stage blades is complex. The rotor blades create outward radial flow. Recirculations are setup near the tip in the gap between the fixed and moving blades, and near the hub downstream of the moving blade. The blade carries negative loading and encounters gross flow separations. In this environment, fluctuations in pressure are detected rotating at about half of the rotor speed. Some similarities exist with rotating stall, as found in compressors. In the validation of a new blade design, checks are therefore included to ensure that the rotating excitation does not pass over a natural frequency of the blading. In turn, this can reduce the available design space.

A less restrictive approach is to consider alleviation techniques. A promising candidate is a scheme where steam jets are directed into the flow, onto the LSB, from the outer boundary. Jets have been introduced and tested on a 1/3rd scale multistage steam turbine. The test turbine is both aerodynamically and mechanically representative of a full size machine. The blowing scheme was shown to reduce and then practically eliminate the rotating pressure pattern. 3D CFD computations reveal the major influence of the jets. The solution is elegant because it does not lead to loss of efficiency or design space.
Gas Compression Optimization for Changing Pipeline Landscape
Authors: Zhang Donghui , Kurz Rainer , Lubomirsky Matt , Garcia David , Singh Avneet , Troya Alex
Published: September 2016

The natural gas midstream gathering and pipeline landscape has become much more dynamic in recent years. Some of the attributes contributing to these continuous changes in operations are due to increased supply from shale gas explorations in North America and increasing natural gas demand in Asia. These changes require new pipelines and compressor stations to be built or existing pipelines and compressor stations to be modified to match new required operating conditions.

Economic factors such as initial capital investment and life cycle costs are very important considerations in the decision process to evaluate the benefits of building new stations or modifying existing stations. This paper presents a discussion of some of the more fundamental factors to be considered in evaluating the economics of station optimization projects, and also introduces a variety of options to manage the lifecycle of the centrifugal gas compressors units and stations.
On the Interaction of Multiple Traveling Wave Modes in the Flutter Vibrations of Friction-Damped Tuned Bladed Disks
Authors: Krack Malte , Panning-von Scheidt Lars , Wallaschek Jörg
Published: September 2016

The aerodynamic interference between the blades of a bladed disk can lead to self-excited vibrations known as flutter. Flutter vibrations can reach considerable levels and are thus of special concern in the design of turbomachines. The vibrations can be saturated in so-called limit cycles by the nonlinear dissipative effects related to dry friction in mechanical joints. For a given mode family of a tuned bladed disk, the flutter stability depends on the interblade phase angle, and often multiple traveling wave forms are unstable. In spite of this, previous investigations indicated that in the steady state, friction-damped flutter vibrations of tuned bladed disks are dominated by a single traveling wave component. In contrast, we demonstrate that, in fact, multiple traveling wave components may interact in the steady state. To this end, a phenomenological model is studied, which possesses one lumped mass per sector, elastic Coulomb friction inter-sector coupling, and two unstable traveling waves forms. Depending on the location of the complex eigenvalues of the linearized system, the steady-state vibrations are shown to be dominated by either of the two unstable wave forms or exhibit considerable contributions of both. Both periodic and quasi-periodic attractor forms are computed using Fourier methods and validated with direct time integration. Moreover, the basins of attraction of the different stable limit states are analyzed in detail. Remarkably, even if a stable, periodic vibration in a certain traveling wave is attained, a sufficiently strong instantaneous perturbation of the same form can give rise to a transient ending in a limit cycle with a different traveling wave character.
A Model for Liquid Films in Steam Turbines and Preliminary Validations
Authors: Simon Amélie , Marcelet Meryem , Hérard Jean-Marc , Dorey Jean-Marc , Lance Michel
Published: September 2016

Liquid films in steam turbines, present in usual operating conditions, play a large but poorly understood part in the wetness-born troubles (power losses and erosion). More knowledge is needed to estimate their impacts and lessen their effects. The aim of this paper is to propose and verify a model to predict these liquid films. This model is based on modified Shallow-Water equations (integral formulation). It takes into account inertia, mass transfer, gravity, gas and wall frictions, pressure, surface tension, droplet impacts, rotational effects and is unsteady. A 2D code has been developed to implement this model. A part of the model has been verified with analytical solutions (Riemann problems and inclined lake at rest), has been confronted with the linear stability of falling liquid film and has been validated with the experiment of Hammitt et al. [1] which involves a sheared film under low-pressure steam turbine conditions.
Circumferential Flow Differences in the Double-Sided Centrifugal Compressor With Non-Balanced Inlets
Authors: Yang Ce , Liu Yixiong , Wu Wangxia , Jing Lei , Wang Benjiang , Chen Shan
Published: September 2016

A double-sided centrifugal compressor consists of two impellers whose inlets are non-balanced, with one side of the impeller connected to the straight duct, and the other connected to the bending duct. This leads to the differences in the inlet conditions of the double-sided impeller, resulting in the differences in the flow structures of the rear impeller along the circumferential direction. In this work, aiming at analyzing the flow structures of the rear impeller, diffuser and volute internal in three flow rate conditions, the internal flow field of the double-sided centrifugal compressor was calculated in a numerical method. It is found that the inlet bending duct results in significant inlet axial velocity difference of the rear impeller along circumferential direction. The axial velocity differences at high span positions become more obvious with the increase of the flow rate. Moreover, the jet-wake structures among the blade passage outlets are also various. At the high static pressure zones of the volute, corresponding blade passage wake regions increase and their sizes are also influenced by the inlet distortion. The circumferential distributions of the static pressure in the diffuser agree well with that in the volute. In the diffuser, the non-uniform degrees of the static pressure distributions are roughly the same at different radius positions and are weakening with the decrease of the flow rate.
Coupling of an Unsteady Lifting Line Free Vortex Wake Code to the Aeroelastic HAWT Simulation Suite FAST
Authors: Saverin Joseph , Marten David , Pechlivanoglou George , Nayeri Christian Navid , Paschereit Christian Oliver
Published: September 2016

A coupling of the Lifting Line Free Vortex Wake (LLFVW) model of the open source wind turbine software QBlade and the wind turbine structural analysis tool FAST has been achieved. FAST has been modified and compiled as a dynamic library, taking rotor blade loading from the LLFVW model as input. Most current wind turbine aeroelastic simulations make use of the Blade Element Momentum (BEM) model, based upon a number of simplifying assumptions which are often violated in unsteady situations. The purpose of the implemented model is to improve accuracy under unsteady conditions. The coupling has been thoroughly validated against the NREL 5MW reference turbine. The turbine is compared under both steady conditions and three unsteady operating conditions to the BEM code AeroDyn. The turbine has been simulated operating at a constant RPM and with a variable-speed, variable blade-pitch-to-feather controller. Under steady conditions the agreement between the LLFVW and AeroDyn is demonstrated to be very good. The LLFVW produces different predictions for rotor power, blade deflection and blade loading during transient conditions. A number of important observations have been made which illustrate the necessity of a higher fidelity aerodynamic model. The validation and results are considered as a step towards the implementation of an open-source, high fidelity aeroelastic tool for wind turbines.
Analysis of Conjugate Heat Transfer Between Cooling Film and Thermal Barrier Coatings Based on Micro-Structure
Authors: Wang Yuzhang , Li Jiali , Liu Hongzhao , Weng Yiwu
Published: September 2016

Due to different preparation processes and long term operation, the micro structure of thermal barrier coating is different. The different micro structures have great effect on the thermal insulation properties of thermal barrier coatings and the conjugate heat transfer between the cooling film and thermal barrier coatings. In this work, different micro structures of thermal barrier coating were reconstructed using the scanning electron microscopy (SEM) images of two kinds of real thermal barrier coatings. The developed numerical calculation program based on the lattice Boltzmann method (LBM) was used to analyze the conjugate flow field and heat transfer between cooling film and porous thermal barrier coatings. The results show that the micro structures of thermal barrier coatings have a great influence on the stability of the surface film. Weak spatial variations in fluid velocity appear over the coating surface. The spatial variations in velocity over the layered coatings are larger because of its rough surfaces. The ratio of the vertical velocity to the bulk flow velocity can reach 2.5%. There is obvious vortex flow at the interface of coatings and cooling film, and weak flow in the interior perpendicular pores of the columnar coatings.
Transient Lift-Off Test Results for an Experimental Hybrid Bearing in Air, Simulating a Liquid Hydrogen Turbopump Start Transient
Authors: Childs Dara W. , Klooster David , Borchard Henry , Pavelek Dustin , Phillips Stephen
Published: September 2016

Start-transient testing of a hybrid (combined hydrostatic and hydrodynamic action) bearing supplied with air was completed, providing an indication of its performance while operating in a compressible fluid medium. The test start transients were modeled after Rocket Engine Transient Simulation Software (ROCETS) predictions for start-transient behavior of running speed ω(t) and bearing supply pressure Ps(t). The top test speed was 15 krpm. The ramp rate, supply pressure Ps values at 15 krpm, constant bearing unit load magnitude w0, and load orientation (load-on-recess LOR or load-on-land LOL) were varied. Five different load-case combinations were carried out (separately) for LOR and LOL load configurations with ramp rates varying from 2206 rpm/s to 8824 rpm/s. The target pressures at 15 krpm varied from 5.32 bars to 18.25 bars.

The tested bearing dimensions were: L = D = 38.1 mm, and Cr =.0635 mm. Lift-off occurs due to the increase in Ps (ω dependent) and was defined as the point of departure towards the center of the bearing with increasing ω while the rotor remained 0.00254 mm (0.1 mils) above the bearing surface. This method is limited by the inability to accurately measure an established operating bearing clearance.

Evaluation of the lift-off Ps versus applied unit load w0 supports the following conclusions: (1) Lift-off Ps is approximately a linear function of w0, (2) Changing the ramp rate while keeping constant the specified Ps at 15 krpm has no significant impact, (3) Lowering the limit Ps at 15 krpm may reduce the lift-off Ps value, and (4) The LOR start-transient cases required a higher lift-off speed and lift-off Ps values than the corresponding LOL start-transient cases.
Numerical Investigation of a Novel Approach for Mitigation of Forced Response of a Variable Geometry Turbine During Exhaust Braking Mode
Authors: Zhao Ben , Hu Leon , Sun Harold , Yang Ce , Shi Xin , Yi James , Curtis Eric , Engeda Abraham
Published: September 2016

One of critical concerns in a variable geometry turbine (VGT) design program is shock wave generated from nozzle exit at small open conditions with high inlet pressure condition, which may potentially lead to forced response of turbine wheel, even high-cycle fatigue issues and damage of inducer or exducer. Though modern turbine design programs have been well developed, it is difficult to eliminate the shock wave and all the resonant crossings that may occur within the wide operating range of a VGT turbine for automotive applications. This paper presents an option to mitigate intensity of the shock wave induced excitation using grooves on nozzle vane surface before the shock wave. Two kinds of turbines in which nozzle vanes with and without grooves were numerically simulated to obtain a three-dimensional flow field inside the turbine. The predicted performances from steady simulations were compared with test data to validate computational mesh and the unsteady simulation results were analyzed in detail to predict the responses of both shock wave and aerodynamic load acting on turbine blade surface. Compared with the original design, an introduction of grooves on nozzle vane surface mitigates the shock wave while also obviously reduces the amplitudes of alternating aerodynamic load on the turbine blades.
Spectra and Large Eddy Structures in the Double Log-Layer of a High Re Wind Turbine Array Boundary Layer
Authors: Chatterjee Tanmoy , Peet Yulia
Published: September 2016

Wind Turbine Array Boundary Layer (WTABL) is a relatively simple, yet useful theoretical conceptualization to study very large wind farms in atmospheric boundary layer (ABL). In the current paper, we perform a high-fidelity LES investigation of a 3 × 3 wind turbine array in a WTABL framework, with a main focus on extending the work beyond the simple analytical model and providing a rigorous fundamental understanding of the dynamic behaviour of length scales, their scaling laws and the anisotropic structure of the energy containing eddies responsible for power generation from the wind turbines. This is accomplished by studying the components of energy and shear-stress spectra in the flow. This knowledge can potentially provide an efficient way to control the wind farm power output as well as serve as a stepping stone to design efficient low order numerical models for predicting farm power and dynamics at reduced computational expense.
Unsteady Force on Multi-Stage and Multi-Passage Turbine Long Blade Rows Induced by Wet-Steam Flows
Authors: Miyazawa Hironori , Furusawa Takashi , Yamamoto Satoru , Sasao Yasuhiro , Ooyama Hiroharu
Published: September 2016

At the 2015 ASME Turbo Expo in Montreal, we presented a paper on unsteady three-dimensional wet-steam flow simulations for the last three stages of a low-pressure real steam turbine. We then focused on the investigation of unsteady wetness in the three-stage blade passages, which was conducted by assuming the same number of blades in the previous study and the real blade number. The obtained results showed that wetness is definitively influenced by the blade number difference between the stator and the rotor. This paper presents a numerical investigation of unsteady pressure forces on the multi-stage blade rows caused by stator-rotor interactions, which include unsteady wakes, vortices, shocks, and wetness. In particular, we investigate the effect of blade number variation on the pressure forces. Our results indicate that unsteady pressure forces are significantly influenced by shocks from the upstream stator trailing edges transferred to the adjacent rotor blade noses. We finally found that the unsteady pressure forces on the rotor blades are strongly influenced by shocks from upstream stator trailing edges near the hub region and the forces result in a time-dependent torque difference between neighboring two rotor blades.
Flow Field Characterization at the Outlet of a Lean Burn Single Sector Combustor by Laser-Optical Methods
Authors: Schroll M. , Doll U. , Stockhausen G. , Meier U. , Willert C. , Hassa C. , Bagchi I.
Published: September 2016

High OPR engine cycles for reduced NOx emissions will generate new aggravated requirements and boundary conditions by implementing low emission combustion technologies into advanced engine architectures. Lean burn combustion systems will have a significant impact on the temperature and velocity traverse at the combustor exit. Lean burn fuel injectors dominate the combustor exit conditions. This is due to the fact that they pass a majority of the total combustor flow, and to the lack of mixing jets like in a conventional combustor. With the transition to high pressure engines it is essential to fully understand and determine the high energetic interface between combustor and turbine to avoid excessive cooling, which has a detrimental impact on turbine and overall engine efficiency.

Velocity distributions and their fluctuations at the combustor exit for lean burn are of special interest as they can influence the efficiency and capacity of the turbine. Within the EU project LEMCOTEC, a lean burn single sector combustor was designed and built at DLR, providing optical access to its rectangular exit section. The sector was operated with a fuel staged lean burn injector from Rolls-Royce Deutschland. Measurements were performed under various operating conditions, covering idle and cruise operation. Two techniques were used to perform velocity measurements at the combustor exit in the demanding environment of highly luminous flames under elevated pressures: Particle Image Velocimetry (PIV) and Filtered Rayleigh Scattering (FRS). The latter was used for the first time in an aero-engine combustor environment. In addition to a conventional signal detection arrangement, FRS was also applied with an endoscope for signal collection, to assess its practicality for a potential future application in a full annular combustor with restricted optical access. Both measurement techniques are complementary in several respects, which justified their respective application and comparative assessment. PIV is able to record instantaneous velocity distributions and is therefore capable to deliver higher velocity moments, in addition to temporal averages. Applied in two orthogonal traversable light sheet arrangements, it could be used to map all three velocity components across the entire combustor cross section, and obtain data on velocity variances, cross-correlations and turbulence intensities. FRS is limited to measurements of average velocities, as long sampling times are required due to the weak physical process of Rayleigh scattering. However, FRS has two advantages: It requires no particle seeding, because it is based on the measurement of a molecular Doppler shift, and it can provide temperature information simultaneously. This contribution complements a second paper (GT2016-56370) focusing on the measurement of temperature distributions at the same combustor exit section by laser-based optical methods.
sHAWT Design: Airfoil Aerodynamics Under the Influence of Roughness
Authors: Holst D. , Pechlivanoglou G. , Kohlrausch C. T. , Nayeri C. N. , Paschereit C. O.
Published: September 2016

Small horizontal axis wind turbines (sHAWTs) are mostly designed by smaller companies with no or just small possibilities of aerodynamic testing and hence, airfoil selection is often based on published performance data and minimal or no experimental testing from the blade designer’s side. This paper focuses on the aerodynamic consequences resulting from an unqualified airfoil selection and accumulating surface soiling. The high performance low Reynolds profile FX 63-137 is compared to an Eppler-338 wing section as well as to a high performance utility scale wind turbine airfoil, AH 93-W-174 -1ex. We extensively investigated these three different airfoils within the low Reynolds regime between 50,000 and 200,000. This regime is especially important for the starting behavior of a wind turbine, i.e. a quick speed up, and is crucial for small wind turbines because they have more frequent start/stop events. A Reynolds number of 200 k is additionally the operational regime of some sHAWT under the 5–10 kW level.

The present study discusses not only the low Reynolds performance of the smooth profiles but investigates the influence of surface soiling. This ranges from 2D disturbances, such as a 0.2mm thin tripwire or several zigzag tapes, up to the simulation of massive sand build up by covering the entire leading edge region with a 40 grit sand paper. The experiments reveal that even small surface soiling has an impact and massive roughness leads in some cases to the loss of 50% in lift coefficient. The experimental data is used to simulate a sHAWT in different stages of debris. While the peak power was reduced by two thirds compared to the clean configuration the annual energy production has halved under certain conditions.
Numerical Aerodynamic Damping Evaluation of High-Pressure Steam Turbine Blades for Aeromechanical Characterization
Authors: Peruzzi Lorenzo , Bellucci Juri , Pinelli Lorenzo , Arnone Andrea , Arcangeli Lorenzo , Cosi Lorenzo , Mazzucco Marco
Published: September 2016

A validated non-linear uncoupled method for flutter stability analysis was employed to estimate the aerodynamic damping of an HP (High-Pressure) steam turbine blade row.

Usually such blade rows are not affected to flutter instability problems, yet an estimation of the aerodynamic damping can be useful for an accurate aeromechanical characterization of these kind of blade rows. The geometry under investigation is a typical steam turbine blade row at design point. Computational aeroelastic analyses are performed on the more relevant modeshape, sampling the nodal diameters, in order to well describe the typical aeroelastic stability curve. The presence of the tip shroud implies a strong mechanical coupling between adjacent blades resulting in complex modeshapes with high frequency, significantly different from those usually analyzed in the flutter analysis.

The results in term of aerodynamic damping curves are rather different from the usually sinusoidal shape. This is due to the large variation of the frequency over the analyzed nodal diameters, especially at low nodal diameters range. This results are useful to give a better insight in the aeroelastic response of this type of blades.
Experimental and Numerical Investigation of Effusion Cooling for High Pressure Turbine Components: Part 2 — Numerical Results
Authors: Ledezma Gustavo A. , Lachance Julienne , Wang Guanghua , Wang Anquan , Laskowski Gregory M.
Published: September 2016

In this study, numerical simulations of adiabatic film cooling effectiveness are carried out on a round hole effusion cooling flat plate configuration. The numerical method used was a Large Eddy Simulation (LES) with periodic unstructured hexa-dominant grids. The numerical 2-D surface effectiveness and the laterally-averaged effectiveness are compared against the Pressure Sensitive Paint (PSP) results obtained in Part 1 of this paper. The numerical runs were done for a constant gas path Mach (Ma) number of 0.1 and 3 film blowing ratios in the 0.6–1.0 range. The objective is to demonstrate the ability of the LES method to capture the physics of η over a relevant range of blowing ratios. The LES predictions of laterally-averaged and local film effectiveness show tremendous improvement with respect to steady state Reynolds Averaged Navier Stokes (RANS) model results. Furthermore the LES data agrees very well with the experimental data.
Heat Transfer Investigation in a Smooth Rotating Channel With Thermography Liquid Crystal
Authors: You Ruquan , Li Haiwang , Tao Zhi , Wei Kuan
Published: September 2016

An experiment investigation was conducted in a smooth cooling channel under rotating conditions on a new rotating facility. The heat transfer phenomenon of rotating channel with constant heat flux boundary conditions was measured using PIV and TLCs (Thermography Liquid Crystal). The square cross-section channel is manufactured from Plexiglas. Four 1 mm thick transparent ITO (Indium Tin Oxide) heater glasses taped on four Plexiglas walls independently to provide the same constant heat flux boundary conditions. The size of the heated channel is 600 mm*80 mm*80 mm.

TLCs was used for measuring the two-dimensional detail distribution of the temperature on the leading surface and trailing surface of the channel. The pixel-level calibration method was used for reducing the error of the TLCs. In the experiments, the Reynolds number, based on the channel hydraulic diameter (D) of 80 mm and the bulk mean velocity, is 20000, and the rotation number are 0, 0.068, 0.135, 0.205, 0.273, respectively. The obtained result shows that rotation has an important different effects on the heat transfer of leading and trailing side. On the trailing side, the heat transfer increases with the rotation number monotonically along the stream wise (X direction), and rotation enhances the local Nu/Nus up to 20%. On the leading side, rotation weakens the Nu/Nus around 25% with the rotation number of 0.273. However, on the leading side, with the increase of rotation number, the Nu/Nus is not decreasing monotonically along the stream wise, there is a slight enhancement (turning point) along the stream wise with different rotation numbers. The position of turning point on the leading side is different with various rotation numbers. With higher rotation number, the turning point moves closer to the inlet of the channel. This phenomenon is an important reference to investigate the flow field in our future work with PIV. More details of two-dimensional distribution Nu on the leading and trailing side will be shown in this work.
Preliminary Design and Considerations of a MWe Scale Supercritical CO2 Integral Test Loop
Authors: Wang Junfeng , Huang Yanping , Zang Jinguang , Liu Guangxu
Published: September 2016

Nuclear Power Institute of China (NPIC) has started the investigation on supercritical carbon dioxide (S-CO2) power cycles since 2011. The aim of this project is to understand the feasibility and economics of coupling S-CO2 power cycle with Gen IV nuclear reactors, industrial waste heat, solar power, and so on. Up to now, the pre-concept design, economics analyses, and feasibility evaluation has been accomplished. The focus in the next step is the technology demonstrations by constructing and testing an integral test loop of S-CO2 Brayton cycle. With subcontractors and collaborators from China and UK, NPIC starts the design of a MWe scale Integral Test Loop in mid-2015. This paper presents some preliminary design results on this Integral Test Loop, including cycle layouts, design heat balance, and components considerations. Future planning on SCO2 power cycle research and development in NPIC is discussed.
Large Eddy Simulations of the Combustor Turbine Interface: Study of the Potential and Clocking Effects
Authors: Koupper Charlie , Bonneau Guillaume , Gicquel Laurent , Duchaine Florent
Published: September 2016

With the generalization of Lean Burn combustors, the flow field entering the turbine tends to feature higher levels of swirl, turbulence, while different hot streak patterns often emerge if compared to the previous generation of combustion chambers. In this context, the combustor-turbine interactions and more specifically the transport of hot streaks through the turbine need to be further analysed to gain engine performance and improved turbine life. Considering this new context, a non-reactive axial combustor simulator representative of a Lean Burn architecture, together with a 1.5 high pressure turbine stage is developed within the European project FACTOR. The interaction between these two modules is numerically investigated by performing Large Eddy Simulation (LES) of the combustor simulator equipped with two Nozzle Guide Vanes (NGVs). By using such an integrated approach, the combustor-turbine interface (plane 40) disappears, allowing: (i) more realistic inlet conditions to the turbine by suppressing all the assumptions associated with averaged profiles; (ii) to account for the potential effect of the vanes on the chamber. Note that if compared to classical approaches, the use of time-resolved LES has the advantage of well predicting the combustor mean flow and turbulence, resulting in more realistic flow properties at the turbine inlet as confirmed by previous works on this configuration. This paper focuses first on two LESs of the combustor-turbine specific configurations: i.e., two clocking positions of the hot streak relative to the NGVs. Significant changes on the thermal field around the vanes are highlighted. When the hot streak is injected in front of a vane leading edge, it considerably heats up the pressure side compared to the adjacent vane although the temperature field is quite uniform at the NGV exit because of the enhanced mixing of the hot streak. On the other hand, when the hot streak is injected in the passage between two adjacent vanes, it remains away from the vane walls preventing them from heating up. The hot streak however crosses the vane passage without being significantly distorted resulting in a more heterogeneous flow field at the rotor inlet. Second, the potential effect induced by the presence of the vanes is investigated by comparing the flow field inside the chamber with and without NGVs. It is found that the potential effect does not alter temperature patterns while a significant radial and azimuthal mass flow redistribution is observed up to about 25% axial chord length upstream of the vanes. The turbulence level is affected by the presence of vanes up to plane 40 when the hot streak is aligned with the passage.
Simplified Estimation of Aerodynamic Damping for Bladed Rotors: Part 2 — Experimental Validation During Operation
Authors: Figaschewsky Felix , Kühhorn Arnold , Beirow Bernd , Giersch Thomas , Nipkau Jens , Meinl Ferdinand
Published: September 2016

Due to increasing requirements of future engine projects, much effort has been spent on the design of more efficient turbomachinery blades in the recent years. Besides aerodynamic efficiency constraints, these designs need to meet structural criteria ensuring that they are safe and robust with respect to High Cycle Fatigue (HCF). The estimation of the resonant vibration amplitude is done based on the aerodynamic force and the overall damping level. Since, for many applications the contribution of mechanical damping is often rather low compared to the aerodynamic counterpart, the determination of the aerodynamic damping is vital for the estimation of the forced vibration response. This second part is meant to contribute to a simplified computation of the aerodynamic damping during operation by making additional assumptions: The investigated mode family shall not suffer from flutter, has a high reduced frequency and the influence of adjacent blades is negligible. Under these circumstances a simplified approach can be introduced that allows for the computation of the mean value of the aerodynamic damping based on a steady state CFD solution of the regarded stage. It is well known, that the aerodynamic damping of a blade mode family depends on the inter blade phase angle (IBPA) and its direction of propagation, which is not covered by the simplified approach. For higher modes the difference between the minimum and maximum damping is often low and the mean value is a good approximation, whereas for fundamental modes there is often a significant difference. However, it is shown that considering a mistuned vibration response of the rotor, the expected value of the mistuned damping exhibits the mean value of IBPA-dependent aerodynamic damping. CFD simulations of an oscillating airfoil indicate a certain validity range of the simplified approach based on a modified reduced frequency and inlet Mach number, which allows to determine for which industrial applications the approach is most suitable. Finally, this range of validity is verified with experimentally determined overall damping values from strain gauge measurements during operation for 2 different industrial applications, an axial compressor stage of a jet engine and a radial turbine stage of a turbocharger.
S-CO2 Turbine Design for Decay Heat Removal System of Sodium Cooled Fast Reactor
Authors: Cho Seong Kuk , Lee Jekyoung , Lee Jeong Ik , Cha Jae Eun
Published: September 2016

A Sodium-cooled Fast Reactor (SFR) has receiving attention as one of the promising next generation nuclear reactors because it can recycle the spent nuclear fuel produced from the current commercial nuclear reactors and accomplish higher thermal efficiency than the current commercial nuclear reactors. However, after shutdown of the nuclear reactor core, the accumulated fission products of the SFR also decay and release heat via radiation within the reactor. To remove this residual heat, a decay heat removal system (DHRS) with supercritical CO2 (S-CO2) as the working fluid is suggested with a turbocharger system which achieves passive operational capability. However, for designing this system an improved S-CO2 turbine design methodology should be suggested because the existing methodology for designing the S-CO2 Brayton cycle has focused only on the compressor design near the critical point.

To develop a S-CO2 turbine design methodology, the non-dimensional number based design and the 1D mean line design method were modified and suggested. The design methodology was implemented into the developed code and the code results were compared with existing turbine experimental data. The data were collected under air and S-CO2 environment. The developed code in this research showed a reasonable agreement with the experimental data. Finally using the design code, the turbocharger design for the suggested DHRS and prediction of the off design performance were carried out. As further works, more effort will be put it to expand the S-CO2 turbine test data for validating the design code and methodology.
A Transient 3D CFD Model of a Progressive Cavity Pump
Authors: Mrinal K. R. , Siddique Md. Hamid , Samad Abdus
Published: September 2016

A progressive cavity pump (PCP) is a positive displacement pump and has been used as an artificial lift method in the oil and gas industry for pumping fluid with solid content and high viscosity. In a PCP, a single-lobe rotor rotates inside a double-lobe stator. Articles on computational works for flows through a PCP are limited because of transient behavior of flow, complex geometry and moving boundaries. In this paper, a 3D CFD model has been developed to predict the flow variables at different operating conditions. The flow is considered as incompressible, single phase, transient, and turbulent. The dynamic mesh model in Ansys-Fluent for the rotor mesh movement is used, and a user defined function (UDF) written in C language defines the rotor’s hypocycloid path. The mesh deformation is done with spring based smoothing and local remeshing technique. The computational results are compared with the experiment results available in the literature. Thepump gives maximum flowrate at zero differential pressure.
Analysis of the Dynamic Behavior of Two High-Pressure Turbines for the Possible Detection of Rub Symptoms
Authors: Cangioli Filippo , Pennacchi Paolo , Vania Andrea , Chatterton Steven , Dang Phuoc Vinh
Published: September 2016

Physical contact between the rotor and stationary-elements is a main topic in the field of rotordynamics. In the last decades, many studies have investigated the causes and the consequences of this phenomenon; the so-called ‘rub’, resulting in several theories and mathematical models. Muszynska characterized the rub from a phenomenological point of view in different conditions, both steady-state and transient; her studies laid the foundations and inspired research in the following years in many universities and research centers. State-of-the-Art methods permit to recognize, in a simple way, the rub during machine operating condition but in spite of the amount of studies, it is still difficult to prevent the occurrence of rubbing.

This paper focuses on identifying what are the forerunner symptoms of rubbing without attach specific attention to the rub and even to the consequences on the machine behavior. The authors investigate how to prevent the occurrence of rub by detecting its symptoms by means of analysis of the vibration and of the diagnostic data. For this purpose, the conventional graphic tools are used: Bode plot, polar plot, cascade plot, waterfall plot, centerline plot, time-based plot etc.

The dynamic behavior of two high-pressure steam turbines, which have been damaged by a physical contact between the rotor and a stationary part, is analyzed. In order to investigate the evolutionary trend of the vibration for possible rub detection, a new graphic tool was developed by the authors.

This work is born thanks to an industrial interest about the identification of evidences in the dynamic behavior of the forthcoming rub.

The data are available in three different sets of measurements, for both the high-pressure turbines. The data cover a quite long period but they are not available during the rubbing.

It must be noticed that the rub has occurred, for both turbines, immediately after a trip of the machine, so it is not excludable, a priori, that the cause of the trip has not been the same cause of the rubbing.
Development of an Active Control System for Rotating Machinery by Means of Tilting Pad Journal Bearings
Authors: Chatterton Steven , Cangioli Filippo , Pennacchi Paolo , Vania Andrea , Dang Phuoc Vinh
Published: September 2016

The current design trend of rotating machines like turbo-generators, compressors, turbines, and pumps is focused on obtaining both high dynamic performances and high versatility of machines in different operating conditions. The first target is nowadays achieved by equipping machines with tilting pad journal bearings. For the second target, State-of-the-Art researches are focused on the development of active systems able to adapt the dynamic behavior of the machine to the external environment and new operating conditions.

Typical causes of large vibration in rotating machines are faults, residual unbalance, resonance condition and instabilities. Aiming at vibration reduction, in recent years many studies are carried out to investigate different solutions; one of them is based on active tilting pad journal bearing.

In this paper, the authors investigate, by simulations, the reduction of shaft vibration by controlling the motion of the pads of a tilting pad journal bearing. The basic idea is to balance the exciting force on the shaft with a suitable resulting force of the oil-film pressure distribution.

In particular, a sliding mode controller has been considered and both angular rotation of the pads about the pivot and the radial motion of the pivot have been analyzed.

Sliding mode control guarantees high robustness of the control system in real applications that can be characterized by a strong non-linear behavior.

In the paper a general consideration about the bearing, the actuating methods and the control system have been provided. A numerical analysis of large size rotor equipped with active pads has been carried out in order to verify the effectiveness of the system in several conditions, even during the most critical operating phase, i.e. the lateral critical speed.