bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of High Efficiency 5MW Class Gas Turbine the Kawasaki M5A
Authors: Ishihara Shinya , Terauchi Koji , Ikeguchi Takuya , Ryu Masanori 
Published: November 2019

Abstract
Kawasaki Heavy Industries (KHI) launched the M5A gas turbine with a rated output of 4.7MW and 32.6% of thermal efficiency at ISO operating conditions. This gas turbine was designed for combined heat and power application (CHP) with dry low emission (DLE) and the features are that it is compact and light-weight. It also has high efficiency (highest in class), suitable exhaust temperature for steam production and achieved the lowest level of exhaust emissions by using proven DLE technologies originating from other recent KHI gas turbines. The design philosophy was successfully applied to be based on previous reliable gas turbine structure and materials as well as using the state-of-the-art technology about aerodynamics and the cooling. The in-house verification tests have been conducted since 2016 to confirm design targets for performance, emissions, durability and operability. This paper describes the development process of M5A and includes technical features and validation test results.
Numerical Modeling of Static and Rotordynamic Characteristics for Three Types of Helically-Grooved Liquid Annular Seals
Authors: Li Zhigang , Fang Zhi , Li Jun , Feng Zhenping 
Published: November 2019

Abstract
This paper deals with numerical predictions of the leakage flow rates, drag power and rotordynamic force coefficients for three types of helically-grooved liquid annular seals, which include a liquid annular seal with helically-grooved stator (GS/SR seal), one with helically-grooved rotor (SS/GR seal), and one with helical grooves on stator and rotor (GS/GR seal). These seals are frequently used for multiple-stage centrifugal pumps as they have the advantage of low leakage (even to zero) due to the “pumping effect” of the helical grooves. However, the static and rotordynamic characteristics of helically-grooved liquid annular seals still are not fully understood, and even more pronounced is the lack of effective numerical models in the literature.
A novel transient CFD-based perturbation method was proposed for the predictions of the leakage flow rates, drag power and rotordynamic force coefficients of helically-grooved liquid annular seals. This method is based on the unsteady Reynolds-Averaged Navier–Stokes (RANS) solution with the mesh deformation technique and the multiple reference frame theory. The time-varying fluid-induced forces acting on the rotor/stator surface were obtained as a response to the time-dependent perturbation of the seal stator surface with the periodic motion, based on the multiple-frequency elliptical-orbit stator whirling model. The frequency-independent rotordynamic force coefficients were determined using curve fit and Fast Fourier Transform (FFT) in the frequency domain. The CFD-based method was adequately validated by comparisons to the published experiment data of leakage flow rates and fluid response forces for three types of helically-grooved liquid annular seals. Based on the transient CFD-based perturbation method, numerical results of the leakage flow rates, drag powers and rotordynamic force coefficients were presented and compared for three types of helically-grooved liquid annular seals at five rotational speeds (n = 0.5 krpm, 1.0 krpm, 2.0 krpm, 3.0 krpm and 4.0 krpm), paying special attention to the effective stiffness coefficient and effective damping coefficient. Results show that the GS/GR seal has the best sealing capability, followed by the GS/SR seal and then the SS/GR seal. The leakage flow rate of all three helically-grooved seals monotonically decreases with the increasing rotational speed. The GS/SR seal possesses the best stiffness and damping capability, followed by the SS/GR seal and then the GS/GR seal. Rotordynamic instability problems are more likely caused by the GS/GR seal in multi-stage centrifugal pumps. From a rotordynamic viewpoint, the GS/SR helically-grooved liquid annular seal is a better seal concept for multi-stage centrifugal pumps.
Sound Power Measurements at Radial Compressors Using Compressed Sensing Based Signal Processing Methods
Authors: Hurst Jakob , Behn Maximilian , Tapken Ulf , Enghardt Lars 
Published: November 2019

Abstract
Two sound power measurement approaches were developped that are easy to install and have the ability to detect the dominant modal content by applying the modern signal processing method, Compressed Sensing. In general Compressed Sensing requires only few measurement positions for an exact reconstruction of sparse acoustic mode fields. For a current study we have chosen two Compressed Sensing algorithms. Each require separate sensor array arrangements and deliver different modal contents, from which the sound power can be derived. Firstly, an Azimuthal Mode Analysis is conducted by applying the Enhanced Orthogonal Matching Pursuit (EOMP) algorithm to a sound pressure measurement vector. The measurements are obtained by using a sensor ring array with optimized positions. In a subsequent step, the sound power is calculated by referring the detected azimuthal mode spectrum to a model describing the energy distribution over the radial mode content. Secondly, using the Block Orthogonal Matching Pursuit (BOMP) algorithm, the radial mode amplitudes are determined directly. This algorithm requires the sensors to be placed at optimized azimuthal and axial positions and reconstructs a set of dominant radial modes that occur in groups. With the objective to verify both methods, the newly designed and optimized arrays in combination with the aforementioned mode reconstruction algorithms are applied to a numerical data set. This data was provided by URANS simulations of a radial compressor set-up, which is an exact replication of an actual test rig located at the RWTH Aachen University. The introduced estimation methods perform well as shown by comparison with an exact and high resolution Radial Mode Analysis Method. In the near future, the presented measurement approaches will be applied in an experimental study performed at the radial compressor test rig.
The Research on Compressor Performance Degradation Caused by Surface Roughness Enlargement due to Corrosion in Marine Environments
Authors: Sun Haiou , Ma Jingyuan , Wang Zhongyi , Cao Lei 
Published: November 2019

Abstract
In the marine environment, the corrosion on a compressor blade caused by salt spray severely affects the compressor performance and poses a threat to its operation reliability. This study simulated the corrosion on the blade made of X20Cr13 martensitic stainless steel caused by salt spray by using the static acceleration test. Average depth and density of surface corrosion pit were calculated by the actual corrosion with peak valley and different shapes and sizes. The value of average deviation Ra was calculated by average depth and density of corrosion pit. According to the empirical formula proposed by Koch and Smith (ks = 6.2 Ra), setting the equivalent sand grain roughness ks in CFX. NASA Stage67 as calculation model. Then analyzed the effects of various surface roughness on compressor performance and internal flow field through the numerical simulation method. The results revealed that with the increase in corrosion time, the flow rate, pressure ratio, torque, and power of the compressor decreased. The internal flow indicated the increasing internal loss and decreasing efficiency. On the basis of loss analysis, the binomial relationships between the service time and relative values of total pressure loss and efficiency loss, respectively, were established.
Impact of Varying High- and Low-Pressure Turbine Purge Flows on a Turbine Center Frame and Low-Pressure Turbine System
Authors: Sterzinger P. Z. , Zerobin S. , Merli F. , Wiesinger L. , Peters A. , Maini G. , Dellacasagrande M. , Heitmeir F. , Göttlich E. 
Published: November 2019

Abstract
This paper presents the experimental and numerical evaluation and comparison of the different flow fields downstream of a turbine center frame duct and a low-pressure turbine stage, generated by varying the inlet flow conditions to the turbine center frame duct. The measurements were carried out in an engine-representative two-stage two-spool test turbine facility at the Institute for Thermal Turbomachinery and Machine Dynamics at Graz University of Technology. The rig consists of a high-pressure (HPT) and a low-pressure (LPT) turbine stage, connected via a turbine center frame (TCF) with non-turning struts. Four individual high-pressure turbine purge flow rates and two low-pressure turbine purge flow rates were varied to achieve different engine-relevant TCF and LPT inlet flow conditions. The experimental data was acquired by means of five-hole-probe area traverses upstream and downstream of the TCF, and downstream of the LPT. A steady RANS simulation taking all purge flows in account was used for comparison and additional insight are gained from a numerical variation of the HPT and LPT purge flow rates.
The focus of this study is on the impact of the variations in TCF inlet conditions on the secondary flow generation through the TCF duct and the carry-over effects on the exit flow field and performance of the LPT stage. Existing work is limited by either investigating multi-stage LPT configurations with generally very few measurements behind the first stage or by not including relevant HPT secondary flow structures in setting up the LPT inflow conditions. This work addresses both of these shortcomings and presents new insight into the TCF and LPT aerodynamic behavior at varying the HPT and LPT purge flows. The results demonstrate the importance of the HPT flow structures and their evolution through the TCF duct for setting up the LPT inflow conditions, and ultimately for assessing the performance of the first LPT stage.
Prediction of Flow Properties on Turbine Vane Airfoil Surface From 3D Geometry With Convolutional Neural Network
Authors: Jin Yuan , Li Shan , Jung Olivier 
Published: November 2019

Abstract
Nowadays, Computational Fluid Dynamics (CFD) simulations play an increasingly important role for turbine airfoil design. This high-fidelity approach is capable to provide accurate information of flow fields. Meanwhile, the calculation accuracy is always gained at the expense of numerical cost. This gap limits opportunities for design space exploration. To address this problem, surrogate models (also known as metamodels) are introduced to approximate high-fidelity CFD models. However, traditional surrogate models, such as Kriging or Radial Basis Function, construct response surface on a design space with limited dimensions. This prevents users from predicting the flow fields directly from the geometry and performing interactive design of airfoil. In the present work, we propose a Convolutional Neural Network (CNN) based surrogate model to predict flow properties on turbine vane airfoil surface from 3D airfoil profile defined by point cloud. The proposed CNN architecture adopts a symmetric expanding path that is similar to the so-called U-Net. The geometries in the training and testing dataset are generated via varying the parameters defined by the Free-Form Deformation approach. The corresponding flow fields are obtained through high-fidelity CFD simulations performed in a finite volume context. Furthermore, a gaussian process based Bayesian optimization technique is utilized to tune automatically the hyperparameters of the network. In this work, we trained the CNN based surrogate model with static pressure and temperature on the mean section of turbine vane airfoil surface. The trained model is able to predict in a reliable and efficient way the corresponding property directly from the 3D geometry, which allows engineers to agilely adjust their airfoil design.
Experimental and Numerical Study on the Effect of Fan-Shaped Hole Configuration on Film Cooling Effectiveness
Authors: Seo Hyun Jae , Park Sang Hyeon , Kwak Jae Su , Kang Young Seok 
Published: November 2019

Abstract
Film cooling technique has been widely applied to protect gas turbine blades from high temperature combustion gases. In this study, to improve the cooling effectiveness of fan-shaped film cooling holes, the effect of the main shape parameters on the film cooling effectiveness was investigated through numerical and experimental studies. Commercial software based on Reynolds Averaged Navier-Stokes (RANS) analysis was used in the numerical study, and the PSP (Pressure Sensitive Paint) technique was used to experimentally measure the film cooling effectiveness. The design points for the optimization were derived by the Box-Behnken method, which is one of the design of experiments (DOE). Three shape parameters of a fan-shaped hole were selected as design variables: the forward expansion angle, the lateral expansion angle, and the length of cylindrical part of the hole. The area-averaged film cooling effectiveness was selected as an objective function and the optimal hole shape of each analysis was obtained using the response surface methodology (RSM). It was confirmed that the film cooling effectiveness was affected by all three variables in both numerical and experimental results. Both analyses showed similar trends of each variable on film cooling effectiveness, but the optimal hole shape obtained by each method was different. The difference is attributed to flow separation not captured by RANS based analysis and surface roughness caused by the manufacturing process and the PSP coating in experimental analysis. Notably, the experimentally optimized hole showed better film cooling effectiveness than that of the numerically optimized hole in the comparison experiments.
Effect of Additive Manufacturing Process Parameters on Turbine Cooling
Authors: Snyder Jacob C. , Thole Karen A. 
Published: November 2019

Abstract
Turbine cooling is a prime application for additive manufacturing because it enables quick development and implementation of innovative designs optimized for efficient heat removal, especially at the micro-scale. At the micro-scale, however, the surface finish plays a significant role in the heat transfer and pressure loss of any cooling design. Previous research on additively manufactured cooling channels has shown the surface roughness increases both heat transfer and pressure loss to similar levels as highly-engineered turbine cooling schemes. What has not been shown, however, is whether opportunities exist to tailor additively manufactured surfaces through control of the process parameters to further enhance the desired heat transfer and pressure loss characteristics.
The results presented in this paper uniquely show the potential of manipulating the parameters within the additive manufacturing process to control the surface morphology, directly influencing turbine cooling. To determine the effect of parameters on cooling performance, coupons were additively manufactured for common internal and external cooling methods using different laser powers, scan speeds, and scanning strategies. Internal and external cooling tests were performed at engine relevant conditions to measure appropriate metrics of performance. Results showed the process parameters have a significant impact on the surface morphology leading to differences in cooling performance. Specifically, internal and external cooling geometries react differently to changes in parameters, highlighting the opportunity to consider process parameters when implementing additive manufacturing for turbine cooling applications.
Physics-Based Simulation in Support of a Through-Life Gas Turbine Service Business Model
Authors: Dawes Bill , Hunt Matt , Meah Nabil , Kudryavtsev Andrey , Evans Rich 
Published: November 2019

Abstract
The overall aim of the work reported in this paper is to explore whether a physics-based simulation approach has the potential to reduce the uncertainty & variability associated with both predicting & managing maintenance costs and improving engine design to optimise through-life economic performance. The main novelty in the paper is to demonstrate how an innovative Digital Geometry model can represent typical in-service component degradation and then support appropriate simulation meshes to permit degraded performance to be predicted. Two examples are given: blade erosion from particulates; and a simulated cooled blade burn-through event.
Numerical Simulation of Combustor Effusion Cooling Flow Based on Source Term Method
Authors: Wang Jing , Mao Ronghai , Tao Wenjie , Wang Zhichao , Zhang Chi , Lin Yuzhen 
Published: November 2019

Abstract
A numerical method based on single-sided source term has been developed to investigate the effects of the effusion cooling air on the temperature distribution in a combustor. The principle of this method is to replace the cooling holes with uniform mass, momentum, energy and turbulence sources on the hot side of the combustor liner. A resolved model that comprises cooling holes and a simplified model based on single-sided source term method have been both numerically computed. The flow and temperature fields attained from the simplified model have been found to be in good agreement with those from the resolved model. Experimental tests of a tri-sector model combustor have been conducted, mainly focusing on its outlet temperature distribution profile. Comparison results showed that the numerical results about the trend of temperature distribution fit well with the experimental data.
Furthermore, the single-sided source term method has been employed onto a simplified model combustor to investigate the design variables of the cooling hole on the temperature distribution. It has been found that as the blowing ratio increases, the wall adiabatic film cooling effectiveness would increase. But the higher blowing ratio affects the formation of corner vortex zone and primary recirculation zone, which results in a higher exit core temperature. The inclination angle of injection flow has little effect on the temperature distribution. The simulation of effusion cooling flow based on the single-sided source term method significantly reduces computational costs without compromising the accuracy. It is expected to be applied in the multi-parameter optimization of the cooling structure in a combustor liner.
Experimental Investigation for Enhanced Control of Rotating Unsteady Flow Instabilities in an Unshrouded Centrifugal Compressor Impeller
Authors: Mischo B. , Jenny P. , Bidaut Y. , Fonzi N. , Hermann D. , Wirsum M. C. 
Published: November 2019

Abstract
Unshrouded industrial centrifugal compressor impellers operate at high rotational speeds and volume flow rates. Under such conditions impeller blade excitation is dominated by high frequency interaction with stationary parts, i.e. vaned diffusers or inlet guide vanes. In a previous study conducted on two full compression units of the original equipment manufacturer (OEM), the authors also identified, characterized and quantified resonant blade vibration caused by the interaction of the impeller blades with sub-synchronous rotating stall cells during severe off-design conditions. The resonant impeller excitation lead to significant dynamic stress in the blades. In a follow-up study the authors have reproduced this phenomenon under representative off-design conditions in a downscaled test rig and successfully reproduced the phenomenon with unsteady Computational Fluid Dynamics (CFD) and structural mechanical Finite Element Method (FEM) analysis. The gained knowledge of these studies was translated into a new diffuser design philosophy, based on a sectorwise circumferential variation of the leading edge angle. In this paper, the patented philosophy by the OEM is presented and verified experimentally on the same test rig configuration in terms of flow path geometry and measurement equipment that was used in the mentioned prior study to assess resonant blade interaction. The results confirm the design aims: rotating stall onset was delayed without affecting the aerodynamic performance of the stage. Resonant blade interaction with rotating stall observed in the baseline diffuser could not be avoided with the two new diffuser designs. However, with the two new diffusers, the induced mechanical stresses in the impeller and the excitability were reduced by up to 12%.
Effects of Axial Velocity of Main Stage on the Performances of a Centrally Staged LPP Combustor
Authors: Wang Zhichao , Hui Xin , Wang Jianchen , Lin Yuzhen , Zhang Chi 
Published: November 2019

Abstract
Characteristics of the main stage exert important effects on the performances in a centrally staged LPP combustor. The experiments on flow fields, spray, and combustion were carried out on the combustors with different axial velocity at the main stage exit (Vm). The NOx emissions, combustion efficiency and lean blowout are all tested in a rectangular model combustor under elevated temperature and pressure conditions, while flow field and spray characteristics are measured in an optical combustor by Kerosene-PLIF and PIV under non-reacting elevated temperature and pressure conditions.
The results show that with the Vm of the main stage changing from 61 m/s to 80 m/s, the NOx emission and combustion efficiency decreases. Meanwhile, lean-blow out (LBO) performance becomes worse. CFD simulation is conducted to investigate the flow fields, spray, emissions and LBO performance of the combustor. The simulation results show the turbulent intensity between the pilot and main stage flows is stronger for the combustor with higher Vm. Besides, the recirculating flow in the recirculation zone also has an increasing trend. The two reasons cause the temperature in the combustion zone decrease, which is beneficial to the NOx reduction. In addition, the stronger turbulence intensity between the main and pilot stage make the quenching of pilot flame more severe, causing the combustion efficiency lower. Moreover, the increase of the inverse flow also worsens the LBO performance.
Nonlinear Vibration Prediction of a Highly Flexible Rotor Supported by an Axial Groove Journal Bearing Considering Journal Angular Whirling Motion
Authors: Koondilogpiboon Nuntaphong , Inoue Tsuyoshi 
Published: November 2019

Abstract
In this study, the difference in dynamic behavior of the rotor-bearing system supported by the bearing model that considers both lateral and angular whirling motions of the journal (model A), and the model that considers only lateral whirling motion (model B) is investigated. The rotor model consists of a slender shaft, a large disk and two small disks supported by a self-aligning ball bearing and an axial groove journal bearing of L/D = 0.6. Three positions of the large disk: 410, 560, and 650 mm measured from the ball bearing, are investigated. Numerical integration of the rotor-bearing system which is modally reduced to the 1st forward mode is performed at above the onset speed of instability until either a steady state journal orbit or contact between the journal and the bearing occurs to identify the bifurcation type. Numerical results using model A indicate subcritical bifurcation with the contact between the journal and the inboard side of the bearing in all three large disk positions, whereas those of model B indicate subcritical bifurcation when the large disk position is at 410 mm, and supercritical bifurcation is observed in the other two cases. Lastly, the experiments at the same three large disk positions are performed. Subcritical bifurcation with the contact between the journal and the inboard side of the bearing is observed in all large disk positions, which conforms with the calculation result of model A. As a result, model A is essential in nonlinear vibration analysis of a highly flexible rotor system.