bluuebunny/crossref_metadata_2025 huggingface dataset:
A Geometry Generation Framework for Contoured Endwalls
Authors: Wood L. E. , Jones R. R. , Pountney O. J. , Scobie J. A. , Rees D. A. S. , Sangan C. M.
Published: November 2019

The mainstream, or primary, flow in a gas turbine annulus is characteristically two-dimensional over the mid-span region of the blading, where the radial flow is almost negligible. Contrastingly, the flow in the endwall and tip regions of the blading is highly three-dimensional, characterised by boundary layer effects, secondary flow features and interaction with cooling flows. Engine designers employ geometric contouring of the endwall region in order to reduce secondary flow effects and subsequently minimise their contribution to aerodynamic loss.

Such is the geometric variation of vane and blade profiles — which has become a proprietary art form — the specification of an effective endwall geometry is equally unique to each blade-row. Endwall design methods, which are often directly coupled to aerodynamic optimisers, are widely developed to assist with the generation of contoured surfaces. Most of these construction methods are limited to the blade-row under investigation, while few demonstrate the controllability required to offer a universal platform for endwall design.

This paper presents a Geometry Generation Framework (GGF) for the generation of contoured endwalls. The framework employs an adaptable meshing strategy, capable of being applied to any vane or blade, and a versatile function-based approach to defining the endwall shape. The flexibility of this novel approach is demonstrated by recreating a selection of endwalls from the literature, which were selected for their wide-range of contouring approaches.
Numerical Investigation of a Swirl Stabilized Methane Fired Burner and Validation With Experimental Data
Authors: Farisco Federica , Notsch Philipp , Prieler Rene , Greiffenhagen Felix , Woisetschlaeger Jakob , Heitmeir Franz , Hochenauer Christoph
Published: November 2019

In modern gas turbines for power generation and future aircraft engines, the necessity to reduce NOx emissions led to the implementation of a premixed combustion technology under fuel-lean conditions. In the combustion chamber of these systems, extreme pressure amplitudes can occur due to the unsteady heat release, reducing component life time or causing unexpected shutdown events. In order to understand and predict these instabilities, an accurate knowledge of the combustion process is inevitable. This study, which was provided by numerical methods, such as Computational Fluid Dynamics (CFD) is based on a three-dimensional (3D) geometry representing a premixed swirl-stabilized methane-fired burner configuration with a known flow field in the vicinity of the burner and well defined operating conditions. Numerical simulations of the swirl-stabilized methane-fired burner have been carried out using the commercial code ANSYS Fluent. The main objective is to validate the performance of various combustion models with different complexity by comparing against experimental data. Experiments have been performed for the swirl-stabilized methane-fired burner applying different technologies. Velocity fluctuation measurements have been carried out and validated through several techniques, such as Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (PIV). Laser Interferometric Vibrometry (LIV) provided information on heat release fluctuations and OH*-chemiluminescence measurements have been done to identify the position of the main reaction zone. During the first part of the CFD investigation, the cold flow has been simulated applying different turbulence models and the velocity flow field obtained in the experiments has been compared with the numerical results. As next, the study focuses on the numerical analysis of the thermo-chemical processes in the main reaction zone. Few combustion models have been investigated beginning from Eddy Dissipation Model (EDM) and proceeding with increased complexity investigating the Steady Flamelet Model (SLF) and Flamelet Generated Manifold (FGM). An evaluation of the velocity field and temperature profile has been performed for all models used in order to test the validity of the numerical approach for the chosen geometry. The best option for future investigations of gas turbines has been identified.
Hydro Francis Runner Stability and Forced Response Calculations
Authors: Seeley Charles , Patil Sunil , Madden Andy , Connell Stuart , Hauet Gwenael , Zori Laith
Published: November 2019

Hydroelectric power generation accounts for 7% of the total world electric energy production. Francis turbines are often employed in large-scale hydro projects and represent 60% of the total installed base. Outputs up to 800 MW are available and efficiencies of 95% are common. Cost, performance, and design cycle time are factors that continue to drive new designs as well as retrofits. This motivates the development of more sophisticated analysis tools to better assess runner performance earlier in the design phase. The focus of this paper is to demonstrate high fidelity and time-efficient runner damping and forced response calculations based on one-way fluid-structure interaction (FSI) using loosely coupled commercial finite element analysis (FEA) and computational fluid dynamics (CFD) codes.

The runner damping is evaluated based on the work done by the fluid on the runner. The calculation of the work first involves determining the runner mode shapes and natural frequencies using a cyclic symmetric FEA model with structural elements to represent the runner hardware, and acoustic fluid elements to represent the mass loading effect of the fluid. The mode shapes are then used in a transient CFD calculation to determine the damping which represents the work done by the fluid on the runner. Positive damping represents stability from flutter perspective while negative damping represents unstable operating conditions.

A transient CFD calculation was performed on a runner to obtain engine order forcing function from upstream stationary vanes. This unsteady forcing function was mapped to the FEA model. Care is taken to account for the proper inter-blade phase angle on the cyclic symmetric model. The hydraulic damping from flutter calculations was also provided as input to the forced response. The forced response is then determined using this equivalent proportional damping and modal superposition of the FEA model that includes both the structural and acoustic elements.

Results of the developed analysis procedure are presented based on the Tokke runner, that has been the basis of several studies through the Norwegian HydroPower Center. Unique features of the workflow and modeling approaches are discussed in detail. Benefits and challenges for both the FEA model and the CFD model are discussed. The importance of the hydraulic damping, that is traditionally ignored in previous analysis is discussed as well. No validation data is available for the forced response, so this paper is focused on the methodology for the calculations.
A Novel Vortex Identification Technique Applied to the 3D Flow Field of a High-Pressure Turbine
Authors: Pátý Marek , Lavagnoli Sergio
Published: November 2019

The efficiency of modern axial turbomachinery is strongly driven by the secondary flows within the vane or blade passages. The secondary flows are characterized by a complex pattern of vortical structures that origin, interact and dissipate along the turbine gas path. The endwall flows are responsible for the generation of a significant part of the overall turbine loss because of the dissipation of secondary kinetic energy and mixing-out of non-uniform momentum flows. The understanding and analysis of secondary flows requires a reliable vortex identification technique to predict and analyse the impact of specific turbine designs on the turbine performance. However, literature shows a remarkable lack of general methods to detect vortices and to determine the location of their cores and to quantify their strength.

This paper presents a novel technique for the identification of vortical structures in a general 3D flow field. The method operates on the local flow field and it is based on a triple decomposition of motion proposed by Kolář. In contrast to a decomposition of velocity gradient into the strain and vorticity tensors, this method considers a third, pure shear component. The subtraction of the pure shear tensor from the velocity gradient remedies the inherent flaw of vorticity-based techniques which cannot distinguish between rigid rotation and shear. The triple decomposition of motion serves to obtain a 3D field of residual vorticity whose magnitude is used to define vortex regions.

The present method allows to locate automatically the core of each vortex, quantify its strength and determine the vortex bounding surface. The output may be used to visualize the turbine vortical structures for the purpose of interpreting the complex three-dimensional viscous flow field, as well as to highlight any case-to-case variations by quantifying the vortex strength and location.

The vortex identification method is applied to a high-pressure turbine with three optimized blade tip geometries. The 3D flow-field is obtained by CFD computations performed with Numeca FINE/Open. The computational model uses steady-state RANS equations closed by the Spalart-Allmaras turbulence model. Although developed for turbomachinery applications, the vortex identification method proposed in this work is of general applicability to any three-dimensional flow-field.
Steam Turbine Hot Standby: Electrical Pre-Heating Solution
Authors: Kostenko Y. , Veltmann D. , Hecker S.
Published: November 2019

Growing renewable energy generation share causes more irregular and more flexible operational regimes of conventional power plants than in the past. It leads to long periods without dispatch for several days or even weeks. As a consequence, the required pre-heating of the steam turbine leads to an extended power plant start-up time [1].

The current steam turbine Hot Standby Mode (HSM) contributes to a more flexible steam turbine operation and is a part of the Flex-Power Services™ portfolio [2].

HSM prevents the turbine components from cooling via heat supply using an electrical Trace Heating System (THS) after shutdowns [3]. The aim of the HSM is to enable faster start-up time after moderate standstills. HSM functionality can be extended to include the pre-heating option after longer standstills.

This paper investigates pre-heating of the steam turbine with an electrical THS. At the beginning, it covers general aspects of flexible fossil power plant operation and point out the advantages of HSM. Afterwards the technology of the trace heating system and its application on steam turbines will be explained. In the next step the transient pre-heating process is analyzed and optimized using FEA, CFD and analytic calculations including validation considerations. Therefor a heat transfer correlation for flexible transient operation of the HSM was developed. A typical large steam turbine with an output of up to 300MW was investigated. Finally the results are summarized and an outlook is given.

The results of heat transfer and conduction between and within turbine components are used to enable fast start-ups after long standstills or even outages with the benefit of minimal energy consumption. The solution is available for new apparatus as well as for the modernization of existing installations.
LDV Characterization of Unsteady Vaned Diffuser Flow in a Centrifugal Compressor
Authors: Gooding William J. , Fabian John C. , Key Nicole L.
Published: November 2019

Modern turbomachinery faces increased performance demands in terms of efficiency, compactness, and pressure-rise. Advancements in computational technology have allowed numerical methods to become the backbone of design development efforts. However, the unique complexities of centrifugal compressor flow-fields pose difficult computational problems. As such, advanced experimental methods must be used to obtain high-quality datasets to further inform, improve, and validate computational methods in complex flow regimes.

Recent experimental work on a high-speed centrifugal compressor has provided detailed, unsteady, three-component velocity data using Laser Doppler Velocimetry. A passage vortex is present and its nascent tied to the increased incidence at mid-span associated with impeller wake flow. This vortex begins in the hub-pressure side corner and grows to fill the passage and become temporally stable. The vortex development is unsteady in nature and the unsteady effects persist 40% downstream of the throat. Distinct jet and wake flow patterns from the impeller also do not agglomerate until 40% downstream of the throat. Additionally, the critical impact of the unsteady flow development on the time-averaged flow-field is explained.
Evaluation of the Numerical Modelling of a High Pressure Turbine Test Rig
Authors: Luquet David , Julienne Francois , Arntz Aurélien , Lippinois Eric
Published: November 2019

To improve the fuel efficiency demanded by airlines and regulations, the turbomachinery industry is required to steadily enhance engine performances and numerical prediction capabilities. One of the solutions is the lean burn combustor which dramatically reduces NOx levels compared to rich one. However, one drawback of this technology is its impact on the High-pressure turbine due to large swirl and reduced cooling airflow, inducing large spatial and temporal variations in the turbine inlet condition. This can drastically change the operation of the turbine and our ability to model it using standard practice, usually RANS computation. To investigate this combustor-turbine interaction, the European Commission-funded project FACTOR (Full Aerothermal Combustor-Turbine interactiOns Research) was launched several years ago. A test rig of a combustor simulator coupled with a 1.5 stage turbine was built at a DLR facility. An extensive test campaign comprising 5 holes probes and infrared imaging was performed. These produced an array of aerodynamic quantities at different points of interest along the machine axis. With this project reaching its term by the end of 2017, results have been disseminated to the partners. This allows a comparison of measurements with RANS modeling on this configuration. The present paper deals with this analysis using several RANS computations and the results of the test campaign. First, single row computation of the Nozzle Guide Vane and rotor blade were performed. To impose the boundary conditions, the experimental map were azimuthally averaged to obtain profiles of total temperature, total pressure and flow angles. Second, the impact of some geometrical features was investigated. This was done using the recent addition of unstructured mesh capability in the elsA solver. Finally, multi-stage computations, both steady (mixing plane) and unsteady (sliding mesh) give an insight on the relative accuracy of these interstage models. All these computations were then used to investigate the behavior of this particular turbine. In addition to classical analysis using profiles of averaged data, the loss sources were identified by computing the viscous and thermal entropy production. This paves the way for a better understanding of the possibilities and limitations of our simulation capabilities.
A Third-Generation Swirl-Venturi Lean Direct Injection Combustor With a Prefilming Pilot Injector
Authors: Tacina K. M. , Podboy D. P. , Dam B. , Lee F. P.
Published: November 2019

This paper presents experimental results for a low-NOx aero gas turbine combustor, in particular, a third-generation swirl-venturi lean direct injection (SV-LDI-3) combustor concept called V4. The purpose of testing was three-fold. First, to evaluate the combustor against the 80% NOx reduction goal set by NASA’s AATT project. Second, to compare V4 to a previous SV-LDI-3 combustor concept called V3, especially at low power conditions. Third, to examine the accuracy of a type of correlation equation frequently used by engine systems analysis groups to estimate NOx emissions. All three testing goals were met. For the first testing goal, with an estimated NOx reduction of 85%–90%, SV-LDI-3 V4 surpassed the AATT goal. For the second goal, however, V4 did not perform better than V3 at low power conditions. For the third goal, it was found that a major assumption of the correlation equations — a simple dependence on combustor inlet pressure — did not hold.
Static Stiffness Measurements for a Thrust Collar Used in an Integrally Geared Compressor
Authors: Kerr Thomas , Delgado Adolfo , Childs Dara
Published: November 2019

This paper presents a comparison of predicted and measured axial stiffness of an oil-lubricated thrust collar (TC) for use in an integrally geared compressor (IGC). The test rig used to measure the stiffness closely resembles a TC that would be used in a production IGC. Separate motors spin two shafts at predetermined spin speeds, and a pneumatic loader applies an axial load to the pinion shaft. The load is transmitted from the pinion shaft through the TC and onto the bull gear shaft. The relative deflection between the faces of the TC is measured as the axial load is increased. Tests were conducted at pinion spin speeds of 5, 7.5, and 10 krpm, and the axial load was varied from 75 to 2,600 N (1 to 32 bar specific load). A custom curve fit describes the load-deflection plot. The slope of the equation is the stiffness coefficient, kz. The measured kz values increase versus axial load, and decrease versus spin speed. Measured and predicted values agree in trend and magnitude. Predicted kz values slightly overestimate the measured results. The power loss from the lubricated area is measured from VFD power outputs. Power loss increases with spin speed and the measured power loss tends to be twice as high as predictions. These results are useful in validating the predictions made by Cable et. al.[1] The results are also useful to IGC original equipment manufacturers (OEMs) or end-users who desire to model their machines.
Effect of Annulus Flow Conditions on Turbine Rim Seal Ingestion
Authors: Palermo Donato M. , Gao Feng , Chew John W. , Beard Paul F.
Published: November 2019

A systematic study of sealing performance for a chute style turbine rim seal using URANS methods is reported. This extends previous studies from a configuration without external flow in the main annulus to cases with a circumferentially uniform axial flow and vane generated swirling annulus flow (but without rotor blades). The study includes variation of the mean seal-to-rotor velocity ratio, main annulus-to-rotor velocity ratio, and seal clearance. The effects on the unsteady flow structures and the degree of main annulus flow ingestion into the rim seal cavity are examined. Sealing effectiveness is quantified by modeling a passive scalar, and the timescales for the convergence of this solution are considered. It has been found that intrinsic flow unsteadiness occurs in most cases, with the presence of vanes and external flow modifying, the associated flow structures and frequencies. Some sensitivities to the annulus flow conditions are identified. The circumferential pressure asymmetry generated by the vanes has a clear influence on the flow structure but does not lead to higher ingestion rates than the other conditions studied.
A Numerical Study on the Effect of Hole Inclination Angle With Imperfection on Film Cooling Effectiveness
Authors: Rezzag Taha , Jubran Bassam A.
Published: November 2019

The present study numerically evaluates the influence of hole inclination angle with a hole imperfection on film cooling performance. Here, the hole imperfection due to laser percussion drilling is modelled as a half torus. Three hole inclination angles were investigated: 35°, 45° and 55°. Furthermore, every case was evaluated at three blowing ratios: 0.45, 0.90 and 1.25. Each case is compared to a baseline case where the hole imperfection is absent. The results indicate that the hole inclination angle has a strong influence on the film effectiveness performance when a hole imperfection is present. Centerline effectiveness plots reveal a maximum effectiveness deterioration of 89% for a blowing ratio of 0.90 in the vicinity of the hole exit. Dimensionless temperature contours show that the jet produced in the presence of an imperfection is much more compact causing the counter rotating vortex pair to be closer to each other. This enhances the jet to lift off from the plate.
Computational Analysis of the Equalization Behavior of Thrust Bearings With Regular and Modified Leveling Plates
Authors: Gokaltun Seckin , DeCamillo Scan
Published: November 2019

In this work, a Finite Element Analysis (FEA) model has been developed that represents the interaction between the thrust bearing components under the influence of a misaligned rotor. The FEA model represents the contact between bearing components such as the pads and leveling plates and calculates the forces and moments created, as well as capturing the elastic deformation caused by the load imposed by the runner. The current analysis excludes the existence of the fluid film between the runner and the pads; therefore, the loads and misalignments created represent a static loading condition. It was observed that the bearing equalization system is still functional for design modification cases such as material removal at the outer diameter of the lower leveling plates, while the equalization performance is reduced slightly.
Reducing Blade Force Response in a Radial Turbine by Means of Jet Injection
Authors: Netzhammer Stephan , Vogt Damian M. , Kraetschmer Stephan , Leweux Johannes , Blackburne Jennifer
Published: November 2019

Radial turbines consisting of a spiral volute inlet casing, such as those found in turbochargers, are subject to excitations caused by the inlet flow. In the absence of inlet guide vanes, the asymmetries from the volute are accentuated and lead to Low Engine Order (LEO) excitations. These excitations can be particularly troublesome as they are likely to resonate with the first bending mode (M1) at high rotational speeds, causing large vibration displacement amplitudes which will result in High Cycle Fatigue (HCF). It is therefore imperative to ensure these vibration amplitudes are low enough to make certain blade failure will not occur.

This paper deals with the possibility of actively influencing the excitation pressure pattern on the blades such that the amplitude and phase of the forcing is affected. This active influence is through the use of an air jet injection at the tip of the turbine blade and has the potential to substantially reduce the blade vibrations caused by the LEO excitations. This theory of using air jets to alter the blade vibration amplitude is investigated in this paper both experimentally, using standard turbine housing equipped with a rotatable device with a single jet nozzle, and numerically, using Computation Fluid Dynamics (CFD) software ANSYS CFX.

The tests yielded positive results indicating that a single air injection was able to significantly decrease, as well as increase, the blade vibration amplitude. At certain jet injection locations, decreases in blade vibration amplitude of 70% were measured which was backed up by numerical results. To numerically calculate these differences in the vibration amplitude, the generalized force approach was used successfully. The positive results obtained from this study show real potential for this method to become a useful tool in keeping blade vibration to a safe level and avoiding failures in turbomachines.
CH Kinetics Measurements and Their Importance for Modeling Prompt NOx Formation in Gas Turbines
Authors: Cooper Sean P. , Mulvihill Clayton R. , Mathieu Olivier , Petersen Eric L. , Crofton Mark W. , Lam King Y.
Published: November 2019

Recent work by the authors and others has uncovered the need for further chemical kinetic-related modeling and experiments, specifically for NOx kinetics at engine conditions. In particular, data on CH formation at realistic combustion conditions are needed for further refinement of the prompt-NOx kinetics. To this end, a series of shock-tube experiments to obtain CH concentration time histories at elevated temperatures was performed behind reflected shock waves at The Aerospace Corporation using a tuneable laser. This Ti-Sapphire laser was operated in the near infrared at about 854 nm; blue light at 426.9 nm was obtained using an external, frequency-doubling crystal. The resulting light was used in a differential absorption setup with common-mode rejection to measure CH time histories. New measurements in CH4-C2H6-O2 mixtures highly diluted in argon were performed at temperatures between 1890 K and 2719 K. These new data are compared to several modern, detailed chemical kinetics mechanisms with updated NOx submechanisms. Sensitivity and rate of production analyses at the shock-tube conditions along with a gas turbine model are used to elucidate the current state of affairs in CH prediction by the literature models and its effect on NOx production, particularly through the prompt mechanism. A brief discussion of the chemical kinetics for an important reaction in the production of CH is also presented to emphasize the need for further study and refinement of reactions leading to CH production.
Dynamics of a Rod-Fastened Rotor Considering the Bolt Loosening Effect
Authors: Li Pu , Yuan Qi , Zhao Bingxi , Gao Jin
Published: November 2019

Rod-fastened rotors are widely applied in heavy duty gas turbines and aircraft engines due to a good stiffness-to-weight behavior compared to conventional forged rotors. In order to achieve a continuous and stable power output, it is critical to guarantee the mechanical integrity. Therefore, the clamping force is of great importance which influences the distribution of the contact pressure. In an extreme condition, the bolt loosening resulting in an additional bending moment entails a different dynamic response. In this paper, the dynamics of a rod-fastened rotor subjected to the unbalance force, combined loads from the residual bow as well as the bolt loosening will be analyzed. First of all, an accurate rod-fastened rotor model is generated incorporating 1D beam element and zero-length joint element. Next, the mode superposition method is applied to derive the equations of motion and the analytical solution of the rod-fastened rotor will be achieved. Furthermore, experimental results are used to verify the simulations. It has demonstrated that the rod loosening yields a remarkably different behavior compared to the normal rotor after balancing. The dynamic response is also closely dependent on the unbalance as well as the relative phase angle between the location of unbalance and rod loosening. This paper provides a fundamental insight into the steady response of the rod-fastened rotor and may be used for fault identification as well as balancing of combined rotors.
Numerical Study on Flow and Heat Transfer Characteristics of Discrete Film Cooling Holes of the Sinusoidal Longitudinal Corrugated Heat Liner
Authors: Xu Zhi-peng , Zhu Hui-ren , Wang Ya-zhou , Bian Xinyu
Published: November 2019

To understand film cooling flow fields and heat transfer characteristics of the longitudinal corrugated surface on afterburner heat liner, the numerical simulation was performed in approximate actual boundary conditions. The single hole and full film holes on the corrugated surface were investigated under different boundary conditions to study the heat transfer and discharge coefficient. The adverse pressure gradient on the leeward results in spanwise expansion of the airflow, while the favorable pressure gradient on the windward keeps the shape of the jet constant. The different hole spacing and hole row spacing in different positions of the corrugated surface should be considered due to the film covering characteristics. The film cooling holes at the same height on the leeward and windward share the similar laterally average effectiveness. The flow rate and discharge coefficient increase from crest to trough. Cross-flow has a negative influence on the discharge coefficient especially the inlet cross-flow. The cross-flow and discharge coefficient can be correlated with each other by a logarithmic function. The jet discharge coefficient on the windward surface is higher than that on the leeward surface, which is contrary to previous cognition. The reason is that the jet blocking causes the downstream pressure zone to advance, which counteracts and enhanced the siphon effect on the leeward and windward side respectively. As the inlet pressure of coolant increases, the film cooling effectiveness on the windward side is greatly improved in full film condition. However, it changes little on the leeward side.
Development of a High-Pressure Hot-Corrosion Burner Rig for Testing Structural Materials Following Long Exposures to Arabian Extra Light Crude Oil Combustion Products
Authors: Saxena Saumitra , McIntosh John , Dawood Ziad , Maloney Andrew , Carolan Ronan , Mitsudharmadi Hatsari , Chen Aiping , Roberts William L. , Giri Krishna Shesha , Mohammad Bassam , Glaser Paul , Goldmeer Jeffrey
Published: November 2019

The use of crude oil as a backup fuel in gas turbines remains an economical option for power plants in petroleum-rich countries like Saudi Arabia. However, operating gas turbines with crude oil can corrode their Hot-Gas-Path (HGP) components due to the formation of vanadium oxides and alkali metal vanadates, when preventative measures are not employed. While the pre-combustion treatment of crude oil fuel is effective at reducing the content of sodium (Na) and potassium (K) in the fuel and, therefore, their resulting combustion products, any pre-combustion removal of vanadium has remained unviable on a commercial scale. Typically, a best practice limit of 0.5 ppmw vanadium is imposed on liquid fuels when inhibitors are not employed, and the total alkali content is limited to 1.0 ppmw. To evaluate the effects of incremental exceedances of such limits on the structural materials and coatings of gas turbines, a high-pressure hot-corrosion test rig was built at King Abdullah University of Science and Technology (KAUST). Arabian Extra Light (AXL) crude oil with a vanadium content of up to 2 ppm was chosen as the test fuel. This burner rig was designed to accommodate high temperatures (∼1173 K/ 900 °C) and the combustion of unrefined crude oils at an elevated pressure of up to 15 bar. Highly reduced flow velocities (∼1 m/s) were employed to deconvolute erosional effects from corrosion. This experiment exposed the tested materials to combustion products under these conditions for extended periods (up to 500 hours). The development of the rig included several design iterations and changes to the configuration of various sub-systems, owing to some challenges in maintaining stable combustion at low flow rates, management of coke/ash formation from the burning of crude oil, and adequate control over the pressure and temperature during extended experimental campaigns. The present publication summarizes the design and commissioning of this high-pressure hot-corrosion rig facility, and the successful demonstration of several long duration (400+ hour) experimental runs with AXL crude oil, where the environment of the sample section with test coupons was maintained at 5.5 bar and 1173 K. The pressure and temperature inside the sample section of the rig were continuously monitored. The batch of material coupons was removed from the sample section after the runs and sent for corrosion analysis. Deposits resulting from the AXL combustion and fouling were collected from several sections of the rig for analytical analysis. The fuel wash procedure, the design of components in the burner rig, and best practices of operation were also documented.
Experimental Study on the Effects of Slot Jet on Film Cooling Performance in the Cascade Endwall With Purge Flow
Authors: Yunjia Yao , Peiyuan Zhu , Zhi Tao , Liming Song , Jun Li
Published: November 2019

Based on the infrared temperature measurement technology, in this paper, the effect of the purge flow from the upstream slot on the film cooling performance of the annular cascade endwall was studied experimentally. GE‘s E3 turbine first stage stator blades is selected as the experimental reference blade type in this experiment. In the current experiment, effects of different slot locations, slot ejection angles and slot profiles on the endwall film cooling effectiveness were taken into account. Under the influence of endwall secondary flow, the film cooling is mainly concentrated on the front part of the channel and close to the suction side of the blade, while there is almost no cooling effect close to the pressure side of the blade in the channel. With the increase of the distance between the blade leading edge and the slot, the endwall film cooling performance is reduced. While the distance increasing from 0.15Cx to 0.45Cx, and the peak endwall film cooling effectiveness is reduced by 78%, 68% and 58% respectively when the mass flow ratio (MFR) is 1.0%, 1.5%, and 2.0%. As the slot ejection angle is reduced, the endwall film cooling performance can be effectively improved. When the slot ejection angle increased from 45° to 90°, the peak endwall film cooling effectiveness decreases by 17%, 15%, and 13% respectively at the mass flow ratio (MFR) = 1.0%,1.5% and 2.0%. And the convergent slot can effectively improve the endwall cooling film formed by slot jet compared to the reference slot. When the mass flow ratio are MFR = 1.0%, 1.5%, and 2.0%, the peak endwall film cooling effectiveness at the convergent slot is increased by 50%, 20%, and 15% comparing to the reference slot.
Development of a Hundreds of kWe-Class Supercritical Carbon Dioxide Power Cycle Test Loop in KIER
Authors: Choi Bongsu , Cho Junhyun , Shin Hyungki , Cho Jongjae , Roh Chulwoo , Lee Beomjoon , Lee Gilbong , Ra Ho-Sang , Baik Young-Jin
Published: November 2019

The supercritical carbon dioxide (S-CO2) power cycle has been a topic of interest because it exhibits a high efficiency and compact size and is compatible with any heat source. Since 2013, the Korea Institute of Energy Research (KIER) has developed three S-CO2 power cycle experimental test loops for distributed power source applications. Based on this experience, a hundreds of kWe-class dual Brayton test loop with a maximum temperature of 500 °C has been designed and partially fabricated. This cycle consists of two turbines, one compressor, two recuperators, and a flued-gas heater. First, a relatively low-temperature turbine with an inlet temperature of 392 °C was designed and manufactured as an axial impulsetype turbo-generator because of the cost and development time required for construction of a full-cycle test loop. As a preliminary step, the turbo-generator was successfully tested in 2017. Next, it was continuously operated for 4.2 h in 2018. In addition, the following components were designed and manufactured: a centrifugal compressor with a dry gas seal; oil-lubricated tilting-pad bearings; a flued-gas heater, which consists of a burner and a shell-and-tube heat exchanger; and two printed circuit heat exchanger type recuperators. The full cycle is expected to be operational in November 2019.
Techno-Economic Evaluation of the Effect of Impurities on the Performance of Supercritical CO2 Cycles
Authors: Vesely Ladislav , Dostal Vaclav , Kapat Jayanta , Vasu Subith , Martin Scott
Published: November 2019

The development of new power generation technologies are necessary to meet growing energy demands and emission requirements. The supercritical carbon dioxide (S-CO2) cycle is one such technology; it has relatively high efficiency, potential to enable 100% carbon capture, and compact components. The S-CO2 cycle is adaptable to almost all of the existing power producing methods including fossil, solar, and nuclear technologies. However, it is known that the best combination of the operating conditions, equipment, working fluid and cycle layout determine the maximum achievable efficiency of a cycle. Impurities in the cycle have some effect on the S-CO2 power cycle as presented in our previous work. The effect of impurities is positive or negative and affects all components. The effect of mixture compositions on the techno-economic evaluation is important information for the global understanding of the effect of mixtures on the S-CO2 power cycle. This paper focuses on the techno-economic evaluation of a hypothetical power plant with the S-CO2 power cycle. Two cases are considered for techno-economic evaluation. The difference between these cases is in the heat source and the associated heat exchanger (PCHE and shell and tube heat exchanger). Cost estimation was performed for three indicators (the levelized cost of electricity, the internal rate of return, and the net present value), which are important for economic viability and the rate of return of the project.
Experimental Investigation on the Creep and Low Cycle Fatigue Behaviors of a Serviced Turbine Blade
Authors: Li Zhenlei , Shi Duoqi , Yang Xiaoguang , Li Nina
Published: November 2019

This paper experimentally investigated the creep and fatigue behaviors of a low-pressure turbine (LPT) blade with 600 hours of service using a novel test system. Pure low cycle fatigue (LCF), pure creep and creep-fatigue interaction (CFI) experiments on the full-scale serviced blades were conducted respectively. Test results showed that the increasing of deformation amplitude was divided into three stages under both pure LCF and creep-fatigue loadings. The deformation of each blade increased rapidly until failure when the test cycle exceeded the 80% of their overall life under the pure LCF and CFI condition. The hold period in creep-fatigue tests shortens the first stage of whole life and has no influence on the proportion of crack initiation life to overall life. The fractures in pure LCF, pure creep and creep-fatigue tests emerged transgranular, intergranular and both transgranular and intergranular behaviors respectively. The crack initiated and propagated in a specific zone of the blade under all the experimental loadings, which limited its creep-fatigue resistance. At last, the remaining life of turbine blade was estimated conservatively by introducing the safety limit into a statistical method.
Experimental and Numerical Evaluation of Losses From Turbine Hub Clearance Flow
Authors: Uher Jan , Milcak Petr , Skach Radek , Fenderl David , Zitek Pavel , Klimko Marek
Published: November 2019

Long-term efforts have been made to understand loss generation and its reduction in the field of axial turbomachines. The traditional approach to losses for an isolated blade row considers the profile and the secondary losses as a result of viscous flow. The additional kinds of losses in the stage are connected with the shear stress in the mixing process. These losses result from the mixing of the main stream flow with 1) the stator leakage injected through the root axial gap and 2) the return of the tip leakage over the bucket shroud. This article focuses on the first type of mixing losses. The leakage to the main stream flow ratio and the root reaction are the two key parameters investigated in this study.

The primary data source for this study is the experiment. An experimental single stage air turbine was modified to set and precisely measure the stator leakage flow. Three configurations of the single-stage test rig with different reaction levels were tested.

The second data source for this study is CFD computation. These computations are applied to different geometries and conditions from the experiment; they are derived from real steam turbine stages designed in DSPW. The computations simulate multistage configuration and real steam is considered as the working fluid. CFD computations were performed in the commercial software ANSYS CFX. Each configuration task was computed in three iterative steps. Each step takes the distribution of the flow parameters on the boundary domains from the previous iteration. The final results from this ‘repeating boundary conditions’ approach better correspond with the real expansion in a multistage configuration.

The two data sources are not directly comparable. The experiment is used for validation of the trends. The computations provide the possibility of a multi-parametric study. The multi-parametric study is necessary to obtain a more general loss model which can be used during turbine design.

The evaluation of the experimental and numerical parts focuses on a comparison of the overall stage performance. Stage efficiency and reaction are presented in relation to the ratio between leakage and main stream flow.
Numerical Modeling of Particle Deposition in Turbine Cascade
Authors: Yang Xiaojun , Hu Yingqi , Yu Tianhao , Liu Zhigang
Published: November 2019

Impurities ingested in the fuel and air may deposit on the surface of turbine components during the operation of aero engines. The presence of such deposits will change the roughness of the blade surface and even seriously affect the aerodynamic performance of each turbine component and the overall safety of the engine. In this study, a new deposition prediction model was developed, which utilizes the User Defined Function (UDF) of Fluent and mesh reconstruction technique to simulate the long-term accumulation of deposition on a nozzle guide vane. Based on the critical viscosity model and the critical velocity model, considering the elasticity and viscosity of particles, some improvements to the model were proposed. The shear removal of individual particles and bulk deposits have been considered in the new deposition model. The simulation result of deposition distribution was verified by comparing with the experimental results obtained under the low temperature wax deposition. Its consistency and problems were also discussed. Subsequently, the increase of deposition thickness with time was shown. The effects of the detachment model and free flow temperature on the deposition distribution were studied. The results show that the deposition at the leading edge of turbine vanes increases fastest with time. The deposition distribution may be more accurate if the detachment model is taken into account. The amount of deposition on the vane pressure surface and stagnation line will increase with the increase of free flow temperature.
A Passive Flow Control to Mitigate the Corner Separation in an Axial Compressor by a Slotted Rotor Blade
Authors: Yoon Sungho , Ajay Rao , Chaluvadi Venkata , Michelassi Vittorio , Mallina Ramakrishna
Published: November 2019

The operability of the axial compressor is generally limited by endwall flows; either at the casing mainly due to the tip leakage flows or at the hub mainly due to three-dimensional corner separations. Therefore, it is crucial to improve flows near the endwalls to enhance the operability of the compressor. Based on a last-stage with cantilevered stator vanes, a small endwall slot was introduced to a rotor blade to mitigate the hub corner separation and maximize the aerodynamic operating range of axial compressors by natural aspiration.

The developed flow control technology is numerically analyzed based on the in-house High-Speed Research Compressor (HSRC) which, in turn, represents the rear stage of a modern compressor. This compressor was predicted to stall due to hub corner separation on a rotor blade based on multistage CFD analysis. A small spanwise endwall slot, connecting the pressure side and the suction side of a compressor rotor blade, was introduced near the hub to provide the by-pass flows from the pressure side to the suction side (see Figure 1). This naturally-aspirated jet significantly reduced the three-dimensional corner separation which generally occurs where the suction side meets the hub. The substantial reduction of the three-dimensional corner separation, in turn, improved the aerodynamic stall margin of the compressor. The benefit is accomplished because the low momentum region near the hub was energized due to the naturally-aspirated jet through the endwall slot and the radial migration of the low momentum flow on the suction side was significantly reduced.

A systematic parametric study was conducted to better understand the flow details and optimize the flow control without sacrificing aerodynamic efficiency. It was discovered that a very small slot, smaller than 10% of span, located near the endwall, was sufficient to have a more than 6% improvement of the stall margin with a negligible efficiency penalty (less than 0.1%). The naturally-aspirated flow through the small slot eliminates the source of the corner separation at the hub platform by strengthening the flow near the hub. This, in turn, reduces the overall aerodynamic blockage by decreasing the radial migration of the low momentum flow over a third of the span. Finally, evaluations of the mechanical strength and structural dynamics of slotted rotor blades, as well as the aerodynamic impact in a multi-stage environment were conducted and its results were discussed.
Similarity Study of Lightly Loaded Shrouded Rotors for Distributed Propulsion
Authors: Lagha Massyl , Duplaa Sébastien , Binder Nicolas , Carbonneau Xavier , Rodriguez Benoit
Published: November 2019

Achieving the objectives of the American and European long-term air transport in terms of emission reduction requires to shift to hybrid/electric aircraft by 2050. This implies the development of distributed propulsion systems using multiple low-diameter lightly-loaded shrouded rotors, operating at high rotational speed and moderate flight Mach number. The relevance of characteristic maps of such a propulsive system is discussed in this paper. It is based on an integrative approach, that takes advantage of the two different formalisms generally found when dealing with aeronautical propulsion : either propeller diagrams (external aerodynamics) or turbomachinery maps (internal aero-dynamics). It outlines the main parameters representing the shrouded rotors performance and the parameters that drive them in a self-similar way. This is done by dimensional analysis, taking into account the geometric and operating parameters of both the rotor and the shroud and their combined variables. The self-similarity is observed with potential flow and RANS computations, which credits the proposed formalism as a powerful tool for scaling the shrouded rotors.