bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantification of Performance Uncertainty for a Transonic Compressor Rotor Using an Adaptive NIPC Method
Authors: Luo Jiaqi , Xia Zhiheng , Liu Feng 
Published: November 2019

Abstract
Turbomachines are designed and run at specific operational conditions. However, due to some deterministic and stochastic sources of flow variations, especially at the inlet and outlet of turbomachinery blades, the influence of operational condition variations to aerodynamic performance are considerable. The quantification of performance change is one crucial module in robust design of turbomachinery blades. The paper studies the performance impact of stochastic operational condition variations using polynomial chaos. To reduce the computational cost, an adaptive sparse grid technique is employed to construct the adaptive non-intrusive polynomial chaos (NIPC) model. Through statistical evaluations of performance change for a three-dimensional transonic compressor rotor blade, NASA Rotor 67, the response performance of adaptive NIPC is firstly verified by comparing with the direct MCS method and static NIPC. Then the adaptive NIPC is used to statistically evaluate the adiabatic efficiency change of Rotor 67 due to the separate variation of inlet total pressure and outlet back pressure at two operation conditions: near peak efficiency and near stall. It is found that the performance change is nonlinear dependent on the inlet and outlet pressure variations. Besides, the simultaneous effects of inlet and outlet pressure variations to the performance change are investigated. Finally, the statistical results of flow variations along span, on the suction side and blade-to-blade streamsurfaces at different spans are illustrated in detail to demonstrate how the inlet and outlet pressure variations influence the aerodynamic performance change.
Reduced-Order Model of Unsteady Flows in a Turbomachinery Fan Modeled Using a Novel Proper Orthogonal Decomposition
Authors: Krath Elizabeth H. , Carpenter Forrest L. , Cizmas Paul G. A. , Johnston David A. 
Published: November 2019

Abstract
This paper presents a novel, more efficient reduced-order model based on the proper orthogonal decomposition (POD) for the prediction of flows in turbomachinery. To further reduce the computational time, the governing equations were written as a function of specific volume instead of density. This allowed for the pre-computation of the coefficients of the system of ordinary differential equations that describe the reduced-order model. A penalty method was developed to implement time-dependent boundary conditions and achieve a stable solution for the reduced-order model. Rotor 67 was used as a validation case for the reduced-order model, which was tested for both on- and off-reference conditions. This reduced-order model was shown to be more than 10,000 times faster than the full-order model.
Application of Quantitative Monochrome Calibrated Schlieren Technique in Highly-Loaded Turbine Cascade Test
Authors: Zhou Zhihong , Wang Haotian , Liu Huoxing 
Published: November 2019

Abstract
As the load of the turbine components of aircraft engines continuously increases, shock loss becomes the dominant factor of turbine stage loss and has become a hot topic. Schlieren technique is one of the few effective experimental methods to observe and study shock wave and, thus, has been widely used. Nevertheless, limited by camera accuracy and computer image processing technology, quantitative schlieren analysis methods were difficult to achieve in engineering applications. Fortunately, several quantitative schlieren methods have been developed with the help of new digital technology. Applying schlieren technique to the highly-loaded turbine cascade test is of great significance to the study of shock wave in highly-loaded turbine cascades. In this paper, the results of quantitative density field and shock intensity and loss in the cascade are obtained by using a double reflection type monochrome schlieren device. The boundary condition of density field is obtained by pressure test, and MATLAB software is used as image processing calculation tool. The quantitative results of this paper prove the feasibility of applying quantitative schlieren method to highly-loaded turbine cascade tests. Also, the implemented image processing method and density boundary condition acquisition method are suitable and convenient for cascade flow and shock measurement tests.
Structural Integrity Assessment and Engine Test of an Additive Manufactured First Stage Ring Segment of a Siemens Large Gas Turbine
Authors: Rühmer Tobias T. , Gampe Uwe , Fischer Kathrin A. , Wimmer Thomas , Haberland Christoph 
Published: November 2019

Abstract
The first stage ring segment (RS) of a Siemens large gas turbine has been redesigned for Selective Laser Melting (SLM) in order to reduce the cooling air consumption and to increase the gas turbine efficiency. The material is IN939. Cylindrical specimen for uniaxial tensile, cyclic tests and creep rupture tests have been manufactured by SLM to characterize the material by derivation of stress strain and creep rupture curves. The ring segment has been tested in a real gas turbine. The loading conditions as well as measurement data from thermocouples and dynamic strain gages have been taken as input for numerical structural integrity assessment. Permissible service life of the ring segment was evaluated in respect of low cycle fatigue (LCF), high cycle fatigue (HCF) and creep. Results have been compared with the conventional design. Furthermore the hook lock up in the engine was evaluated. The manufacturing quality was ensured through several methods including an optical 3D measuring system and computer tomography, process specimen and flow tests. Post investigations such as cut ups and metallography have also been conducted. The results show that the additive manufactured RS meets the required service lifetime.
Design and Flow Analysis of a Radial Outflow Turbo-Expander
Authors: Wang Xuesong , Sun Jinju , Huo Changjiang , Huo Guilong , Song Peng 
Published: November 2019

Abstract
Radial-outflow turbo-expanders have emerged in the recent years to suit some special applications where complex multi-phase and multi-component flows (like liquid-rich gases and solid particle-laden gases) need to be expanded. This paper presents a systematic study on the design and flow behavior of a single stage radial-outflow turbo-expander, which is to be used in organic Rankine power system to covert the low-temperature heat into shaft power. A mean-line code coupled with the optimization algorithm is developed and used to carry out the one-dimensional preliminary design, where 7 non-dimensional parameters are used as design variables (nozzle velocity coefficient, rotor velocity coefficient, reaction, rotor inlet and outlet flow angles, velocity ratio, and rotor diameter ratio). In comparison with the original design, significant design performance gains are achieved with the matched combination of design parameters. Geometric shape design is further performed for the expander. In consideration of the flow features in nozzle and rotor blade passages being nearly two-dimensional, blade shape design of both rows is conducted on the basis of the airfoils used for conventional axial flow turbines, where a conformal mapping method is used to convert the axial profile into the polar coordinate frame and it is then represented by 11 parameters of mean cylindrical diameter, radial and tangential chord, leading and trailing edge radius, blade inlet and outlet angles, blade inlet wedge angle, number of blades, unguided turning, and throat size. Flow and overall performance are simulated and predicted for the designed expander, where the output shaft power and overall isentropic efficiency is respectively predicted as 87.86 kW and 81.60% at design condition.
Parametric Design of Blisk Repairs by Patching Considering High Cycle Fatigue
Authors: Berger Ricarda , Hofmeister Benedikt , Gebhardt Cristian G. , Rolfes Raimund 
Published: November 2019

Abstract
Advanced repair techniques intended for jet engine parts are continuously under development and improvement. Patching is a high-tech approach towards reduced scrap rates and an extended life of high pressure compressor blisks.
In this work, we contribute to the structural design of patches for compressor blisks with improved high cycle fatigue behaviour. A fully parameterised patch model is developed, which allows the accurate description of the patch geometry. High cycle fatigue is assessed for welding seam positions specified by the patch model. On the basis of this automated process, a multi-objective optimisation is carried out. The fatigue strength and the length of the welding seam are defined as conflicting targets. Pareto-optimal solutions are calculated using a generalised pattern search algorithm. The engineer’s decision for a specific patch geometry can thus be made based on the optimisation results. The application of the new approach to a compressor blisk demonstrates the influence of vibration modes on fatigue strength. We identify sets of optimal suited patch geometries in accordance to the specified damage pattern.
Wet Gas Compressor Model Validation
Authors: Bakken Martin , Bjørge Tor , Bakken Lars E. 
Published: November 2019

Abstract
The continuous demand for oil and gas forces the petroleum industry to develop new and cost-efficient technologies to increase recovery from new fields and enhance extraction from existing fields. Subsea wet gas compression stands out as a promising solution to increase field extraction, utilize remote regions and reduce costs.
Today, a few subsea compressor systems are already operating while several new installations are expected within the next years. This creates a need for dynamic simulation tools to ensure proper system design and facilitate production. This paper presents the model setup for the wet gas compressor test facility at the Norwegian University of Science and Technology (NTNU). The test facility is an open loop configuration consisting of a single shrouded centrifugal impeller, a vaneless diffuser and a circular volute. The fluid is a mixture of ambient air and water. The analysis presented here validates the dynamic model behavior against transient experimental test cases, which include step changes in liquid content and driver trip in both wet and dry conditions. Further, the discharge valve performance has been analyzed in both dry and wet gas flow.
The test reveals that the dynamic model is able to operate in a stable manner while showing a close correspondence to the transient test cases. Care should be taken in utilizing dry gas valve characteristics in multiphase flows as increased liquid content has a distinct impact on the valve performance.
High Temperature Fatigue Assessment of a SiCf/SiC Ceramic Matrix Composite Using Advanced Monitoring Techniques
Authors: Newton Christopher D. , Jordan Steven P. , Bache Martin R. , Gale Louise 
Published: November 2019

Abstract
Laboratory based experiments to assess the “damage tolerance” of any new material system are a pre-requisite to engineering design, especially for aerospace components. In the case of CMCs, macro-scale specimens are preferred containing representative fibre-matrix architectures that support the definition of mechanical properties under service representative stress states.
The combination of complex internal structure and inevitable processing artefacts within CMCs provides numerous sites for damage initiation. Damage then progresses in an inhomogeneous manner prior to ultimate failure at some critical location. Traditional techniques employed for strain measurement (extensometry/strain gauges) prove to be ineffective tools when testing these advanced composites. More complex characterization is essential in order to assess the localised response of the material.
Advanced techniques, specifically digital image correlation and acoustic emission, have been applied to the evaluation of an CVI/MI silicon carbide reinforced/silicon carbide CMC tested at the elevated temperature of 800°C under fatigue loading. The spatial and temporal indications of damage were correlated to the observable forms of damage initiation and progression. Ancillary use of an in-situ SEM loading stage provided insight into the crack opening and closing mechanisms active within this material when under cyclic stress.
Prediction of Low-Engine-Order Excitation due to a Non-Symmetrical Nozzle Ring in a Radial Turbine by Means of the Nonlinear Harmonic Approach
Authors: Kovachev Nikola , Müller Tobias R. , Waldherr Christian U. , Vogt Damian M. 
Published: November 2019

Abstract
Low engine order (LEO) excitation in a turbomachine stage can be induced by non-uniform inflow conditions, manufacturing tolerances or in-service wear. LEOs are known to excite significant forced response vibration amplitudes that can easily cause High Cycle Fatigue (HCF) failure of blades. The accurate prediction of LEO excitation usually requires high-fidelity CFD models of the full annulus of the machine due to the loss of symmetry leading to excessive computational cost.
Previous investigation showed that the aerodynamic excitation stemming from the blade-passing-frequency in a vaned radial inflow turbine can be accurately predicted by using the NonLinear Harmonic (NLH) method at highly reduced computational costs. In the current paper, the feasibility of the NLH method for the prediction of LEO excitation due to geometrical asymmetries is investigated for the same test object. An exact digital replica of the nozzle guide ring is created using measured throat width data. NLH simulations resolving different combinations of frequencies and a time-marching calculation are conducted with the new model involving this digital replica. The results show that a NLH model including small number of certain frequencies is able to predict the occurring LEO excitation sufficiently accurate. By comparing results from subsequent forced response analysis with measured vibration amplitudes, a satisfactory agreement was found confirming this conclusion.
Large Eddy Simulation of the Flow Developing in Static and Rotating Ribbed Channels
Authors: Duchaine Florent , Gicquel Laurent , Grosnickel Thomas , Koupper Charlie 
Published: November 2019

Abstract
In the present work, the turbulent flow fields in a static and rotating ribbed channel representative of an aeronautical gas turbine are investigated by mean of wall-resolved compressible Large Eddy Simulation (LES). This approach has been previously validated in a squared ribbed channel based on an experimental database from Von Karman Institute (Reynolds and rotation numbers of about 15000 and +/− 0.38 respectively). LES results prove to reproduce differences induced by buoyancy in the near rib region and resulting from adiabatic or anisothermal flows under rotation. The model also manages to predict the turbulence increase (decrease) around the rib in destabilizing (stabilizing) rotation of the ribbed channels. On this basis, this paper investigates in more details the spatial development of the flow along the channel and its potential impact on secondary flow structures. More specifically and for all simulations, results on the adiabatic static case exhibits two contra-rotating structures close to the lateral walls of the channel induced by transversal pressure difference created by the ribs. These structures are generated after the first ribs and appear behind all inter rib sections, their relative position being partly affected by rotation. When considering the stabilizing rotating case, two additional contra-rotating structures also develop along the channel from the entrance close to the low-pressure wall (rib-mounted side). These vortices are due to the confinement of the configuration, inflow profile and are the result of Coriolis forces induced by rotation. Görtler vortices also appear on the pressure wall (opposite to the rib-mounted side). In the destabilizing rotating case, these two types of secondary structures are found to co-exist and their migration in the channel is significantly different due to the presence of the ribs on the pressure side. Finally, it is shown that heat transfer affects only marginally the static and stabilized cases while it changes more significantly the flow organization in the destabilizing case mainly because of enhanced heat transfer and increased buoyancy force effects.
Analysis of Thermal Transients for sCO2 Brayton Cycle Heat Exchangers
Authors: Moisseytsev Anton , Sienicki James J. 
Published: November 2019

Abstract
The design of heat exchangers for use in a supercritical carbon dioxide (sCO2) Brayton cycle power converter must provide for acceptable performance for duty cycle events encompassing anticipated transients and postulated accidents. This paper presents the results of a comprehensive analysis of thermal transients for sCO2 cycle heat exchangers, with emphasis on the sodium-to-CO2 heat addition heat exchanger. A range of transients, from normal operation to severe accidents, were simulated with the coupled PDC and SAS4A/SASSYS-1 system level dynamic analysis computer codes. For each transient, the calculated change in the heat exchanger wall temperature is determined as a measure of the thermal loading.
Design and Performance Analysis of Mixed Flow Turbine Rotors With Extended Blade Chord
Authors: Leonard Thomas , Spence Stephen , Filsinger Dietmar , Starke Andre 
Published: November 2019

Abstract
Mixed flow turbines offer additional design freedom compared with conventional radial turbines. This is useful in the automotive turbocharger application to reduce rotor inertia, which can be very beneficial for the transient response of a highly-boosted downsized passenger car powertrain. A previously published study from the authors analysed a series of nine mixed flow turbine rotors with varying blade cone angle and inlet blade angle. This paper reports an extension of that study with two further mixed flow turbine rotors where the chord length of the rotor blade was extended. The aim of this work was to understand both the aerodynamic and mechanical impacts of varying the chord length, particularly for the turbocharger application where off-design performance and transient response are very important. The baseline mixed flow rotor for this study had a blade cone angle of 30° and an inlet blade angle of 30°. Two further variations were produced; one with the TE extended in the downstream direction across the entire blade span. In the second variation the chord was extended at the hub corner only, while the shroud corner of the TE remained unchanged, with the aim of achieving some aerodynamic improvement while meeting mechanical requirements.
When the blade was extended at both the hub and shroud, the inertia and stress levels increased significantly and the blade eigenfrequencies reduced. There was significant improvement in peak efficiency, but the mechanical performance was unfavourable. The improvement in peak efficiency was mainly due to better exhaust diffuser performance and therefore would not be realised in most turbocharger installations.
The blade that was extended at only the hub corner incurred very little additional inertia, and the centrifugal stresses and blade eigenfrequencies were improved. Consequently, it was possible to reduce the blade thickness at the TE in order to achieve a more aerodynamically optimised design. In this case, the mechanical performance was acceptable and there were efficiency improvements of up to 1.1% pts at off-design conditions, with no reduction in peak efficiency or maximum mass flow rate. Therefore, the blade that was extended only at the hub produced some improvement within acceptable mechanical limits. The flow field features were considered for the three rotor geometries to explain the changes in loss and efficiency across the operating range.
Numerical Investigation of the Influence of Flow Deflection at the Upper Hood on Performance of Low Pressure Steam Turbine Exhaust Hoods
Authors: Munyoki Dickson , Schatz Markus , Vogt Damian M. 
Published: November 2019

Abstract
Most of the world’s power is produced by large steam turbines using fossil fuel, nuclear and geothermal energy.
The LP exhaust hoods of these turbines are known to contribute significantly to the losses within the turbine, hence a minor improvement in their performance, which results in a lower backpressure and thus higher enthalpy drop for the steam turbine, will give a considerable benefit in terms of fuel efficiency.
Understanding the flow field and the loss mechanisms within the exhaust hood of LP steam turbines is key to developing better optimized exhaust hood systems. A detailed analysis of loss generation within the exhaust hood was done by the authors [1]. It was found that most losses occur at the upper hood and are caused by the swirling flows, which mostly start at the diffuser outlet, especially for the top diffuser inlet sector flows that have a complex path to the condenser. The authors further numerically investigated the influence of hood height variation on performance of an LP turbine exhaust hood [2], which further contributed to the knowledge of the loss mechanisms.
With the loss mechanisms in exhaust hoods reasonably well understood, flow deflection at the upper hood is investigated in the current paper. The deflection is aimed at minimizing the intensity of the vortices formed thus reducing the exhaust losses. The deflector configurations analyzed are modifications of the walls of the reference configuration’s outer casing. The numerical models of the reference configuration which are based on a scaled axial-radial diffuser test rig operated by ITSM have already been validated by the authors at design and overload operating conditions and three tip jet Mach numbers (0, 0.4 and 1.2)[1].
Deflector configurations investigated are found to re-direct the flow at the upper hood and minimize the intensity of the swirling flows hence leading to improvement in performance of LP steam turbine exhaust hoods. The best performing deflector configuration is found to give a considerable improvement in performance of 20% at design load and 40% at overload both at tip jet Mach number of 0.4 (corresponding to shrouded last stage blades). At design load and tip jet Mach number of 1.2 (corresponding to unshrouded last stage blades), the improvement is found to be moderate. About 7% performance increase is observed.