bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling the Unsteady Dynamics of a Turbine Research Facility
Authors: Longley John P. 
Published: November 2019

Abstract
The accuracy with which experimental investigations of turbine performance need to be undertaken require either a semi- or fully-automated control of the operating point as any variation can compromise the reliability of the measurements. Fundamentally, both the mass flow rate through the turbine and the applied brake torque need to be adjusted in real-time so that the required operating point is maintained.
This paper describes the development of a time accurate computational simulation of the unsteady dynamics of a large-scale, low-speed turbine facility when its operating point is determined by a full-authority control system. The motivation for the development of the computational simulation was to be able to safely undertake parametric studies to refine the control system and to investigate the cause of monotonic excursions of the operating point which were observed after a major rebuild.
The monotonic excursions of the turbine operating point could only be reproduced by the computational simulation after an unsteady aerodynamic coupling between the turbine exit flow and the downstream centrifugal fan had been incorporated. Based on this observation a honeycomb was installed upstream of the fan in the turbine facility. This eliminated the monotonic excursions and the fractional noise of the operating point was reduced by 37%. When combined with an earlier refinement of the control system the factional noise was reduced by a factor of three. This enables the number of repeated measurements to be reduced by nine and still obtain the same quality of data.
Mechanical Damage Accumulation in SiCf/SiC CMCs Characterised via In-Situ Computed X-Ray Tomography
Authors: Weston Eleri , Nicholson P. Ian , Pattison Stephen , Bache Martin 
Published: November 2019

Abstract
The use of an in-situ loading stage combined with an X-ray computed tomography (XCT) system is demonstrated for detecting sub-critical damage and ultimate failure mechanisms in a 0/90° continuous fibre reinforced SiCf/SiC ceramic matrix composite. XCT inspection was performed on macroscopic scaled test coupons sampling a significant number of fibre tows, whilst the material was subjected to monotonic tensile load, both static and cyclic in nature. The observation of inherent, post-processing features and the tracking of the resultant damage within the composite were demonstrated, supported by post-test inspections using scanning electron microscopy. Two important fracture modes are illustrated, with the tensile stress axis applied in the 0/90° and ±45° orientations relative to the fibre tows.
A CFD Assessment of Engine Core Zone Casing Heat Transfer
Authors: Sun Zixiang , Hills Nicholas J. , Scott Richard 
Published: November 2019

Abstract
A systematic CFD investigation was conducted to assess the core zone (CZ) casing heat transfer of a large civil aircraft engine. Three key engine operating conditions, maximum takeoff (MTO), cruise (CRZ) and ground idle (GI) were analyzed. Steady flows were assumed. Turbulence was simulated using the realizable k-epsilon model in conjunction with the scalable wall function. Buoyancy effect was taken into account. Radiation was calculated using the discrete ordinate (DO) model. It was shown that the forced convection heat transfer dominates in most of the casing surface in the core zone, and radiation is of second importance in general. However, in some areas where both convection and radiation heat transfer are weak but the latter is relatively greater in magnitude than the former, radiation heat transfer could thus become dominant. In addition, the overall impact of radiation on casing heat transfer increases from MTO to CRZ and GI conditions, as the strength of engine load decreases. The overall effect of buoyancy on casing heat transfer is small, but could be noticeable in some local areas where flow velocity is low. The insight into heat transfer features on the engine core zone casing supported by quantified CFD evidences is the first in the public domain, as far as authors are aware.
Investigation of Cross-Sectional Velocity Field Near the Inducer Plane of a Turbocharger Compressor Using 2D Particle Image Velocimetry
Authors: Banerjee Deb , Dehner Rick , Selamet Ahmet , Miazgowicz Keith , Brewer Todd , Keller Philip , Shutty John , Schwarz Arno 
Published: November 2019

Abstract
Understanding the velocity field at the inlet of an automotive turbocharger is critical in order to suppress the instabilities encountered by the compressor, extend its map and improve the impeller design. In the present study, two-dimensional particle image velocimetry experiments are carried out on a turbocharger compressor without any recirculating channel to investigate the planar flow structures on a cross-sectional plane right in front of the inducer at a rotational speed of 80 krpm. The objective of the study is to investigate the flow field in front of a compressor blade passage and quantify the velocity distributions along the blade span for different mass flow rates ranging from choke (77 g/s) to deep surge (13.6 g/s). It is observed that the flow field does not change substantially from choke to about 55 g/s, where flow reversal is known to start at this speed from earlier measurements. While the tangential velocity is less than 8 m/s, the radial velocity increases along the span to 17–20 m/s near the tip at high flow rates (55–77 g/s). As the mass flow rate is reduced below 55 g/s, the radial component starts decreasing and the tangential velocity increases rapidly. From about 5 m/s at 55 g/s, the tangential velocity at the blade tip exceeds 50 m/s at 50 g/s and reaches a maximum of about 135 m/s near surge. These time-averaged distributions are similar for different angular locations in front of the blade passage and do not exhibit any substantial azimuthal variation.
Computational Study of the Non-Parametric Squeeze Film Damper Bearing Inverse Model Based on Artificial Neural Networks Applied to a Rotor-Casing System Running on Unsupported SFDs
Authors: Torres Cedillo Sergio G. , Al-Ghazal Ghaith Ghanim , Bonello Philip , Cortés Pérez Jacinto , Reyes Solís Alberto 
Published: November 2019

Abstract
Squeeze Film Damper (SFD) bearings play a vital role in attenuating large amplitudes of vibration due to their relatively simple assembly in aero engine designs. The modern aero-engine structures, typically, have at least two nested rotors mounted within a flexible casing via squeeze-film damper (SFD) bearings. There is a growing body of research into identification techniques for bearing models for use in rotor-bearing analysis to improve reliability and/or efficiency of implementation. The authors’ previous work has shown that, for cases where there is no adequate linear connection between the rotor and casing, the identification of the unbalance from externally mounted sensors requires a virtual instrument that can determine the vibration of the rotor relative to the casing, as a substitute for internal instrumentation. The present study is devoted to determining the effectiveness of the inverse SFD model (under different unbalance state conditions), when it is applied to a rotor-casing system, wherein the rotor runs on two unsprung SFD bearings. The validation of the inverse SFD model enables its use in a future study of the identification of unbalance in such complex systems.
Radial Inlet and Exit Design for a 10 MWe sCO2 Axial Turbine
Authors: Cich Stefan D. , Moore J. Jeffrey , Marshall Michael , Hoopes Kevin , Mortzheim Jason , Hofer Douglas 
Published: November 2019

Abstract
An enabling technology for a successful deployment of the sCO2 closed-loop recompression Brayton cycle is the development of a high temperature turbine not currently available in the marketplace. This turbine was developed under DOE funding for the STEP Pilot Plant development and represents a second generation design of the Sunshot turbine (Moore, et al., 2018). The lower thermal mass and increased power density of the sCO2 cycle, as compared to steam-based systems, enables the development of compact, high-efficiency power blocks that can respond quickly to transient environmental changes and frequent start-up/shut-down operations. The power density of the turbine is significantly greater than traditional steam turbines and is rivaled only by liquid rocket engine turbo pumps, such as those used on the Space Shuttle Main Engines. One key area that presents a design challenge is the radial inlet and exit collector to the axial turbine. Due to the high power density and overall small size of the machine, the available space for this inlet, collectors and transition regions is limited. This paper will take a detailed look at the space constraints and also the balance of aero performance and mechanical constraints in designing optimal flow paths that will improve the overall efficiency of the cycle.
Experimental Analysis of a Particle Separator Design With Full-Field 3D Measurements
Authors: Borup Daniel D. , Elkins Christopher J. , Eaton John K. 
Published: November 2019

Abstract
Particle ingestion into turbine engines is a widespread problem that can cause significant degradation in engine service life. One primary damage mechanism is deposition of particulate matter in internal cooling passages. Musgrove et al. proposed a compact particle separator that could be installed between the combustor bypass exit and turbine vane cooling passage inlet. The design had small pressure losses but provided limited particle separation, and its performance has proved difficult to replicate in subsequent experiments. Borup et al. recently developed a Magnetic Resonance Imaging (MRI) based technique for making full-field, 3D measurements of the mean particle concentration distribution in complex flows. A particle separator based on the Musgrove et al. design was fabricated out of plastic using 3D printing. The primary difference from earlier designs was the addition of a drain from the collector, through which 3% of the total flow was extracted. The separator efficiency was measured at two Reynolds numbers, using water as the working fluid and 33-micron titanium microspheres to represent dust particles. Particle Stokes number was shown to play the dominant role in determining efficiency across studies. MRI was used to obtain the 3D particle volume fraction and 3-component velocity fields. The velocity data showed that flow was poorly distributed between the separator louvers, while the collector flow followed the optimal pattern for particle retention. The particle distribution data revealed that strong swirling flow in the collector centrifuged particles towards the outer wall of the collector and into a partitioned region of quiescent flow, where they proceeded to exit the collector via the drain. Future designs could be improved by re-arranging the louvers to produce a more uniform flow distribution, while maintaining the effective collector design.
Parametric Studies on Aerodynamic Performance of Various Types of LP Turbine Airfoils for Aero-Engines Under the Influence Periodic Wakes and Freestream Turbulence
Authors: Funazaki Ken-ichi , Murakami Daichi , Okamura Yasuhiro 
Published: November 2019

Abstract
This study carries out parametric investigations on aerodynamic loss of various types of LP turbine airfoils characterized with different flow deceleration rates (DR) on their suction surfaces under the realistic flow conditions such as wake inflow and freestream turbulence. The Reynolds number examined in this study ranges from 57,000 to 170,000. As for the freestream turbulence, two levels of the turbulence are used, i.e., about 1.2% and 3.5%. Stagnation pressure distributions downstream of each of the airfoil cascades are measured by use of a Pitot tube, while steady-state and unsteady boundary-layers are measured over the rear part of suction surface and pressure side near the trailing edge using a single hot-wire probe. The measured boundary-layer data are used to estimate the cascade loss along with RANS (Reynolds-Averaged Navier-Stokes) simulations by taking advantage of the momentum-theory based Denton’s method. First, relationships between the cascade loss for each flow condition and DR are examined. The estimated loss values are then compared with the measured cascade loss to check the validity of the loss estimation method, which is a derivative of Denton’s method, under the realistic flow conditions.
Numerical Investigation on the Vibration of Steam Turbine Main Inlet Control Valves Considering Fluid Force Effects
Authors: Li Yueyue , Xu Sihua , He Jin , Hu Zhiqiang , Xiao Lei 
Published: November 2019

Abstract
In this paper, a finite element model (FEM) for inlet control valve was built and the structural modal analysis was performed to get the Eigen-frequencies of the valve. The valve plug as well as the stem together with piston rod and spring block were analyzed separately. Some peak frequencies of the main inlet control valves were obtained at the 2% lift case during warm-up stage on a nuclear power plant. The dynamic flow field as well as the steam forces were obtained by computational fluid dynamic (CFD) calculations with DES turbulence model. In order to clarify the cause of the valve vibration, the natural frequencies were compared with the test data to indicate that the frequency of certain rocking modes may coincided with the test results. What’s more, the peak frequencies of the dynamic steam forces from CFD simulations were also compared with the rocking modes of control valve to identify the mechanism that cause the vibration at certain frequencies.
Aerodynamic Comparison Between Circumferential and Wing-Embedded Inlet Distortion for an Ultra-High Bypass Ratio Fan Stage
Authors: Giesecke Daniel , Friedrichs Jens 
Published: November 2019

Abstract
Future aircraft design concepts often show a somewhat wing embedded ultra-high bypass ratio engine. The aircraft concept of the Coordinated Research Centre 880 (CRC880) is a single-aisle configuration with engines partly integrated over the aircraft wing. The aircraft is designed to take off and land on regional airfields with low noise and fuel emissions to address the guidelines set by the ACARE. As a result of the engine installation, the inlet induces a non-axisymmetric boundary layer ingestion into the fan stage.
In experimental setups, inlet distortion has often been seen as a 60-degree circumferential inlet stagnation pressure distortion. However, the fan stage inlet flow of the prescribed engine installation of the CRC880 differs to a great extent from a 60-degree sector. In this paper, an aerodynamic comparison between a realistic inflow situation and a similar 60-degree inlet distortion for the same ultra-high bypass ratio fan stage is given. The realistic inflow situation is a result of the flow moving over the aircraft wing suction side and entering the nacelle. As non-axisymmetric inlet geometry remains the same for both cases, therefore, only the total pressure boundary condition at nacelle inlet was changed between both cases. Hence, full annulus simulations are required. Both inlet distortion cases are equivalent by matching average 60-degree distortion coefficient. This study points out that the method, by using averaged 60-degree segment values, excludes specific inflow characteristics. For the same averaged 60-degree distortion coefficient, the local distortion of the embedded case is up to four times larger at rotor tip compared to the segmental approach. For constant mass flow, fan pressure ratio and isentropic efficiency drop by more than five and eight percent respectively. At peak efficiency operating condition, the decrease is even more significant with more than nine percent in stage efficiency.
For future embedded aircraft engine configurations, the fan designer has to take into account the non-axisymmetric local flow changes. Hence, the 60-degree segment method is not sufficient when investigating experimental boundary layer ingesting fans and therefore, further method developments are necessary.
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

Abstract
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

Abstract
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

Abstract
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.