bluuebunny/crossref_metadata_2025_split huggingface dataset:
Capacity Matching of Aeroderivative Gas Generator With Free Power Turbine: Challenges, Uncertainties, and Opportunities
Authors: Thirumurthy Deepak , Casado Coca Jose Carlos , Suraweera Kanishka 
Published: November 2019

Abstract
For gas turbines with free power turbines, the capacity or flow parameter matching is of prime importance. Accurately matched capacity enables the gas turbine to run at its optimum conditions. This ensures maximum component efficiencies, and optimum shaft speeds within mechanical limits.
This paper presents the challenges, uncertainties, and opportunities associated with an accurate matching of a generic two-shaft aeroderivative HP-LP gas generator with the free power turbine. Additionally, generic performance trends, uncertainty quantification, and results from the verification program are also discussed. These results are necessary to ensure that the final free power turbine capacity is within the allowable range and hence the product meets the performance guarantees.
The sensitivity of free power turbine capacity to various design variables such as the vane throat area, vane trailing edge size, and manufacturing tolerance is presented. In addition, issues that may arise due to not meeting the target capacity are also discussed. To conclude, in addition to design, analysis, and statistical studies, a system-of-systems approach is mandatory to meet the allowed variation in the free power turbine capacity and hence the desired gas turbine performance.
X-Ray Phase Contrast Imaging of Liquid Film and Spray Development Inside an Aircraft Engine Swirler
Authors: Sforzo Brandon A. , Kastengren Alan L. , Matusik Katarzyna E. , Gomez del Campo Felipe , Powell Christopher F. 
Published: November 2019

Abstract
Modern aircraft engines combine liquid fuel and air using an intricate flow device with many fuel and air flow passages. To date, the process by which the fuel atomizes within this swirler set has not been examined directly due to optical access limitations. In this work, high-speed x-ray phase-contrast imaging of a liquid spray inside a gas turbine engine swirler geometry is presented. Measurements were carried out at the 7-BM beam-line of the Advanced Photon Source at Argonne National Laboratory using the high-energy broadband x-ray beam. The synchrotron x-ray source provides the necessary photon energy and flux to capture time-resolved fluid phenomena within the confines of the relevant geometry while liquid and air are flowing. Spray nozzle hardware and geometries were provided by the National Jet Fuels Combustion Program, allowing for characterization of the spray using a commercially relevant configuration. Modified swirlers were 3D printed with acrylic to improve imaging access while maintaining influential internal features. Water was used as a surrogate fluid for these studies to demonstrate the visualization capabilities. The experiments were conducted at atmospheric exit pressure conditions with a pressure drop of 6% across the swirler. High-speed imaging of the pilot spray cone revealed sheet breakup several millimeters downstream of the orifice exit, upon interaction with the radial assist air flow. These droplets and ligaments were observed to impinge on the inner filming surface of the swirler and flow toward the exit while developing a tangential flow. Under these conditions, the liquid film grows up to several hundred microns in thickness on the filming surface, and subsequently forms ligaments up to several millimeters in length before breaking up. This work demonstrates the capability of x-ray diagnostics in visualizing liquid flows within solid geometries of technical relevance. Furthermore, the spatial quantification of filming flows and liquid interaction with the swirler air provides validation data for modeling of the multi-phase flows and surface interactions within the swirler.
An Impact Assessment of Erosion of Nozzle Guide Vanes and Rotor Blades on Aerodynamic Performance of a Gas Turbine by CFD
Authors: Yonezawa Koichi , Takayasu Masahiro , Nakai Genki , Sugiyama Kazuyasu , Sugita Katsuhiko , Umezawa Shuichi , Ohmori Shuichi 
Published: November 2019

Abstract
Nozzle guide vanes (NGVs) and rotor blades deteriorate due to erosion, and this may affect the aerodynamic characteristics of gas turbines. According to previous studies, the erosion of first-stage NGVs significantly affected the blade loading of the first-stage rotor. An increase in the tip gap also may significantly affect the gas turbine performance. In the present study, numerical investigations have been carried out using a real eroded nozzle and blade geometries for two purposes. One purpose was to clarify the influences underlying the deterioration of the nozzle and the rotor blade, such as the effects on the erosion of NGVs in the first stage and the effects of the tip gap on the gas turbine performance. The other was to develop a method to estimate the total gas turbine performance using a CFD simulation and a heat balance analysis. The results show that the erosion of NGV leads to an increased flow rate and affects the operating condition of the gas turbine cycle. This, in turn, can decrease the total thermal efficiency. The experimental results suggest that an increase in the tip gap width decreases rotor output almost linearly, and the numerical results showed the same tendency. The influence of the tip gap in the real gas turbine condition was also examined, revealing that an increase in the tip gap leads to an increase in the pressure loss in the nozzle downstream as well as around the rotor blade itself. Consequently, the total power output and the isentropic efficiency of the turbine decreased.
Effect of Rotating Instabilities on Aerodynamic Damping of Axial Flow Fan Blades
Authors: Yang Weichao , Wang Yanrong , Han Le , Zhang Xiaobo , Li Zichao 
Published: November 2019

Abstract
Rotating instabilities (RIs) have been reported in axial flow fans as well as in low-speed and high-speed axial compressors during recent years. They can cause the non-synchronous vibrations (NSV) and generate noise.
In this paper, numerical simulations are performed on an axial flow fan to investigate the influence of RIs on aerodynamic damping of fan blades. The phenomena of RIs in the axial fan were first observed during an experimental test. The spectrum of the pressure signal captured by the case-mounted unsteady pressure transducers near blade tips contains narrow frequency bands below the blade passing frequency, of which the dominant frequency does not equal harmonics of rotor shaft frequency.
The numerical investigation is performed with an unsteady 3D Navier-Stokes method that solves for the entire blade row at near-stall point to confirm the phenomena. Flow separation and blade tip vortex shedding are captured at the tip region of the blades in the simulation. Although the spectrums are different between numerical simulation and experimental results, the simulation predicts a dominant pressure fluctuation frequency of RI that is almost the same as the experimentally measured value, which verified the accuracy of the numerical simulation. Aeroelasticity of the fan blade is investigated by influence coefficient method based eigenvalue method. At near-maximum-efficiency point and near-stall point, aerodynamic modal damping ratios (AMDRs) and distribution of local AMDR of first two modes (first and second flapping mode) are computed respectively. The separation region improves the stability of both modes. However, the vortex shedding area on suction side reduce the AMDRs of 1F mode while the vortex impingement region on pressure side reduces local AMDR for both modes.
On the Interaction of Swirling Flames in a Lean Premixed Combustor
Authors: Ramachandran Gopakumar , Dutta Ankit Kumar , Durairaj Harish , Chaudhuri Swetaprovo 
Published: November 2019

Abstract
Premixed or partially premixed swirling flames are widely used in gas turbine applications because of their compactness, high ignition efficiency, low NOx emissions and flame stability. A typical annular combustor consists of about eighteen to twenty-two swirling flames which interact (directly or indirectly) with their immediate neighbors even during stable operation. These interactions significantly alter the flow and flame topologies thereby bringing in some discrepancies between the single nozzle (SN) and multi nozzle (MN), ignition, emission, pattern factor and Flame Transfer Functions (FTF) characteristics. For example, in MN configurations, application of a model based on SN FTF data could lead to erroneous conclusions. Due to the complexities involved in this problem in terms of size, thermal power, cost, optical accessibility etc., a limited amount of experimental studies has been reported, that too on scaled down models with reduced number of nozzles. Here, we present a detailed experimental study on the behavior of three interacting swirl premixed flames, arranged in-line in an optically accessible hollow cuboid test section, which closely resembles a three-cup sector of an annular gas turbine combustor with very large radius. Multiple configurations with various combinations of swirl levels between the adjacent nozzles and the associated flame and flow topologies have been studied. Spatio-temporal information of the heat release rate obtained from OH* chemiluminescence imaging was used along with the acoustic pressure signatures to compute the Rayleigh index so as to identify the regions within the flame that pumps energy into the self-excited thermoacoustic instability modes. It was found that the structure of the flame-flame interaction regions plays a dominant role in the resulting thermoacoustic instability. To resolve the flow and reactive species field distributions in the interacting flames, two-dimensional, three component Stereoscopic Particle Image Velocimetry (SPIV) and Planar Laser Induced Fluorescence (PLIF) of hydroxyl radical was applied to all the test conditions. Significant differences in the flow structures among the different configurations were observed. Simultaneous OH-PLIF and SPIV techniques were also utilized to track the flame front, from which the curvature and stretch rates were computed. Flame surface density which is defined as the mean surface area of the reaction zone per unit volume is also computed for all the test cases. These measurements and analyses elucidate the structure of the interaction regions, their unique characteristics and possible role in thermoacoustic instability.
Application of Adaptive GPA to an Industrial Gas Turbine Using Field Data
Authors: Ramadhan Ericcson , Li Yi-Guang , Maherdianta Deplian 
Published: November 2019

Abstract
The gas turbine inspection activities provided by the manufacturers and user maintenance scheme may be different from each other. To accommodate the difference, performing engine diagnostic as a condition-based monitoring technique is necessary to support Asset Performance Management (APM) adopted by the gas turbine users to improve the scheme.
This paper provides an application of a novel Adaptive Gas Path Analysis (Adaptive GPA) to diagnose performance and health condition of a GE industrial gas turbine MS5001PA operated by PT Pupuk Kaltim (PKT). In the application, an engine thermodynamic model is constructed, adapted, and validated on the actual engine performance based on its gas path measurements. To estimate the health condition from the degraded engine data, two steps are applied in the Adaptive GPA diagnostic process. The first step is the estimation of degraded engine performance status and the second step is the prediction of engine health status at the gas turbine component level. Adaptive GPA results show that satisfactory predictions of the engine degradation have been achieved. In other words, the compressor has been predicted 5.56% degradation in flow capacity and 4.26% degradation in efficiency respectively, which is an indication of compressor fouling. Combining the diagnostic results, manufacturer’s recommendations, and user maintenance strategy, it is relatively safe and allowable to increase the maintenance inspection interval from 12,000 to 16,000 hours. Therefore, the adaptive GPA is proven to be beneficial to support condition-based maintenance decisions.
Transient Regime Simulation From Idle to Maximum Take-Off Flight Conditions of Cooled Cooling Air Heat Exchanger for an Aero Gas Turbine Heat Management
Authors: Mucci Alberto , Kholi Foster Kwame , Ha Man Yeong , Min June Kee , Beecroft Peter A. , Yoon Sang Youl , Yun Won Geun , Sibilli Thierry 
Published: November 2019

Abstract
The quest for improving the thermal efficiency of gas turbines has raised the turbine entry temperatures (TET) and hence the operating pressure ratios (OPR). However, the combination of high TET and high cooling flow temperature makes the cooling of the hot sections more challenging. A cooled cooling air heat exchanger (CCAHX) can be used to cool the high-temperature compressor offtake, showing improved steady aerothermal performance in terms of pressure and temperature. Presented here is the experimental testing of the CCAHX and the process used to generate a highly representative transient simulation of its dynamic performance between idle and Maximum Take-Off (MTO) flight conditions. Said simulation is primarily used to predict the performance during further experiments. Due to the harsh experimental conditions, the simulation guarantees safe operations of the test facility while advising on the right procedures to use during real scale tests. Due to the complex internal structure of the heat exchanger, a one-dimensional computational fluid dynamics (CFD) commercial software was employed to validate the models using results from steady-state data for a single CCAHX unit. Derived procedures from the 1D analysis are used to guide the transient testing at real scale flight conditions, where the core and fan flows are thermally-linked to two CCAHXs in a back-to-back configuration. Results show that the approach considered here can correctly predict the performance of a complex heat exchanger system in transient, fast-changing operations, as calculations in real flight conditions showed good agreement with experimental results of a real scale test.
Identification of Metal Temperature Distribution in Steam Turbine During Start-Up Operation Using Particle Filter and Model Order Reduction
Authors: Ito Hiroshi 
Published: November 2019

Abstract
In steam turbines (STs), evaluation technology of thermal deformations during transient operations is increasingly important, because of a demand for improvement of operability such as shortening startup time. However, it is still difficult to predict temperatures of metal parts with sufficient accuracy due to complexity of heat transfer phenomena.
The present study puts its focus on developing a method to identify metal temperatures of STs during start-up operations using particle filter (PF), a kind of sequential Bayesian filter utilizing ensemble approximation, and model order reduction (MOR) technique.
In this method, a self-organizing state-space model is used to calculate time evaluations of metal temperatures, and heat transfer coefficient (HTC) parameters and steam bulk temperature parameters. And an optimal estimate of these is obtained through iterations of a short-time prediction and a correction of variables using measured temperatures. In this state-space model, state variables including HTC and bulk temperature parameters are treated as random variables, and the time evolution of each variable is modeled as follows;
(1) Metal temperature is modeled using a reduced order model (ROM) in order to reduce computational time of PF. The ROM is constructed from a finite element model for unsteady heat transfer analysis using MOR technique.
(2) HTC is modeled as a random walk model where its changes during one time step is randomly determined using Gaussian noise. Here, the magnitude of this noise is adjusted automatically.
(3) Bulk temperature is modeled using prediction formulas with Gaussian noise added.
As a validation problem, a cold start-up operation of a ST unit of a gas turbine combined cycle (GTCC) is considered. The proposed method is applied to the problem, and boundary conditions (BCs) are identified using measured temperatures at 68 measurement points. Then, the heat transfer analysis based on finite element analysis (FEA) is performed using the identified BCs. As a result of this FEA, it is confirmed that the calculated metal temperature tends to agree better with measurements compared with that of initial FEA, and that the errors of the calculated temperature at measurement points reduce by 41% on average compared with initial FEA. From this result, it is concluded that this proposed method is effective for metal temperature identification during start-up operations.
Investigation of Combustor-Turbine-Interaction in a Rotating Cooled Transonic High-Pressure Turbine Test Rig: Part 1 — Experimental Results
Authors: Krumme Alexander , Buske Clemens , Bachner Johannes R. , Dähnert Jerrit , Tegeler Marc , Ferraro Federica , Gövert Simon , Kocian Frank , di Mare Francesca , Pahs Andreas 
Published: November 2019

Abstract
Within the scope of European Commission FP7 project FACTOR, dedicated to combustor-turbine-interaction research, a clean-sheet design of a rotating turbine test rig featuring a non-reacting combustor simulator was created and built among the partners. German Aerospace Center DLR provided the operational facility NG-Turb to which the rig was adapted and was responsible for global rig integration and operation, also including aerodynamic probe measurements of the flow field.
The rig and experimental set-up is described and post-processed results from probe traverses in several measurement planes are presented and discussed. Special attention is paid to the comparison and influence of two combustor-NGV clocking positions on the periodic turbine flow field, made possible by rig adaptation during the campaign. The strongly distorted and nonuniform turbine inlet flow created by the combustor simulator proved challenging for the probe measurements, but at the same time set a realistic boundary condition enabling the analysis of ‘CTI’ by flow structures migrating through the blade rows.
Advances in High-Speed Linear Design Technology: Novel Approach to Sidewall Geometry Design for Erosion Tests
Authors: Sokolov Maksim , Lorenz Max , Rostamian Mirco , Koch Christian , Weissschuh Matthias , Staudacher Stephan 
Published: November 2019

Abstract
Test rigs for compressor cascade testing reported in literature are characterized by a high level of complexity. This is especially the case if a variable incidence should be allowed for or the flow conditions reach transonic or supersonic flow regimes. Incidence alteration capability is preferable for obtaining a more comprehensive picture of cascade properties. However, it necessitates a complex kinematic set-up in order to rotate the blades and to adjust the sidewall setting such that flow periodicity across the passages is ensured. Additionally, a complex sealing system is usually required to guarantee minimum flow disturbance. Often, a suction system is also introduced for boundary layer control and regulation of flow conditions. In the case of erosion testing the situation is exacerbated as the application of such conventional adjustment devices is ruled out due to the presence of solid particles in the flow. In this work an investigation of a new cascade design for erosion testing with variable incidence was conducted. A fixed sidewall geometry is proposed which ensures periodic flow conditions in the speed range of M = 0.5 up to M = 0.78 while allowing incidence adjustments in the range of i = ±10° as assessed by means of CFD. The novel design paradigm enables such flexibility by virtue of a self-regulating flow induced by flow separation from the fixed sidewall geometry. The latter has the benefit of not requiring a specialized mechanical setup and sealing due to the absence of movable parts in the flow. The calculated results show acceptable periodicity of various flow parameters within the passage at 50 percent blade height for all incidence settings considered. The conducted investigation has demonstrated that specially designed fixed sidewalls may enable sufficiently accurate transonic erosion testing under various incidence angles while making cascade erosion testing more economical and time efficient.
Experimental Investigations of Turbulent Flow in a Rotating Ribbed Channel in Terms of the Effect of Coriolis Force
Authors: You Haoliang , Li Haiwang , You Ruquan , Tao Zhi , Shi Jincheng 
Published: November 2019

Abstract
In the current work, the effect of Coriolis force is considered in a rotating rectangular rib-roughened channel. Time-resolved PIV (Particle Image Velocimetry) was used to measure the flow field. The Reynolds number is fixed at 10000, and the rotation numbers range from 0 to 0.52. The ribs obstruct the channel by 10%. The mean velocity fields and Reynolds shear stress fields are obtained. Due to the effect of Coriolis force, the flow fields are different between leading and trailing side. Furthermore, the vortex and the reattachment are also investigated. Based on the results, it can be inferred that Coriolis force plays a significant effect on the vortices. Coriolis force enlarges the vortex near the leading side, but suppresses the vortex near the trailing side. An interesting phenomenon has been found. Because of the Coriolis force pointing to the trailing side, the main stream is supposed to be pushed to the trailing side. But the results show that a velocity deficit appears near the trailing side. This phenomenon indicates that the Coriolis force is not the only force affecting the flow, but the secondary flow is also an important factor that cannot be ignored in a rotating ribbed channel.