bluuebunny/crossref_metadata_2025_split huggingface dataset:
Virtual Gas Turbines Part I: A Top-Down Geometry Modelling Environment for Turbomachinery Application
Authors: Kulkarni Davendu Y. , Lu Gan , Wang Feng , di Mare Luca 
Published: September 2021

Abstract
The gas turbine engine design involves multi-disciplinary, multi-fidelity iterative design-analysis processes. These highly intertwined processes are nowadays incorporated in automated design frameworks to facilitate high-fidelity, fully coupled, large-scale simulations. The most tedious and time-consuming step in such simulations is the construction of a common geometry database that ensures geometry consistency at every step of the design iteration, is accessible to multi-disciplinary solvers and allows system-level analysis.
This paper presents a novel design-intent-driven geometry modelling environment that is based on a top-down feature-based geometry model generation method. In the proposed object-oriented environment, each feature entity possesses a separate identity, denotes an abstract geometry, and carries a set of characteristics. These geometry features are organised in a turbomachinery feature taxonomy. The engine geometry is represented by a tree-like logical structure of geometry features, wherein abstract features outline the engine architecture, while the detailed geometry is defined by lower-level features. This top-down flexible arrangement of feature-tree enables the design intent to be preserved throughout the design process, allows the design to be modified freely and supports the design intent variations to be propagated throughout the geometry automatically.
The application of the proposed feature-based geometry modelling environment is demonstrated by generating a whole-engine computational geometry. This geometry modelling environment provides an efficient means of rapidly populating complex turbomachinery assemblies. The generated engine geometry is fully scalable, easily modifiable and is re-usable for generating the geometry models of new engines or their derivatives. This capability also enables fast multi-fidelity simulation and optimisation of various gas turbine systems.
Numerical Predictions of Cavitating Flow Within a Liquid Hydrogen Inducer
Authors: Blumenthal Robert F. , Kelecy Franklyn J. 
Published: September 2021

Abstract
With the recent interest in using liquid hydrogen as a fuel source for energy production and transportation, predicting the performance of pumping systems which handle hydrogen has become an important issue. Liquid hydrogen is a cryogenic fluid which exists at extremely low temperatures and presents a myriad of design challenges to ensure a safe, efficient, and robust fuel delivery system. In addition, the typical operating conditions for pumps handling liquid hydrogen are such that vapor formation due to cavitation is present in the flow even when the head rise is relatively unaffected. Cavitation can cause severe damage to pump components and lead to shortened life and eventual failure, especially at the temperatures associated with liquid hydrogen.
The present work was focused on validating CFD methods for accurately predicting cavitating flow in a pump inducer handling cryogenic hydrogen. The CFD code used in this study was Ansys CFX, which is a general-purpose commercial solver with models available for simulating cryogenic cavitation in turbomachinery. The specific model employed for cavitation utilized a Rayleigh-Plesset based multiphase formulation in conjunction with thermodynamic property tables appropriate for cryogenic liquid hydrogen. Adjustments to cavitation model parameters were introduced as a function of fluid temperature to account for the thermal suppression head effects that are present at cryogenic thermal conditions.
Dependence of LPBF Surface Roughness on Laser Incidence Angle and Component Build Orientation
Authors: Subramanian Ramesh , Rule David , Nazik Onur 
Published: September 2021

Abstract
Laser Powder Bed Fusion (LPBF) of metallic components is unlocking new design options for high efficiency gas turbine component designs not possible by conventional manufacturing technologies. Surface roughness is a key characteristic of LPBF components that impacts heat transfer correlations and crack initiation from co-located surface defects — both are critical for gas turbine component durability and performance. However, even for a single material, there is an increasing diversity in laser machines (single vs multi-laser), layer thicknesses (∼20–80 microns) and orientations to the build plate (upskin, vertical and downskin) that result in significant variability in surface roughness. This study systematically compares the surface roughness across the above-mentioned variables to further develop a repeatable correlation of surface roughness to the angle between the substrate normal and laser incidence direction. This presented data will be discussed in detail, to show potential applicability of this process signature curve across materials, machines, and substrate orientations. Future steps to a rapid process qualification standard for surface roughness, across Siemens Energy’s global manufacturing footprint will also be discussed.
Research on Matching Characteristics of Ship-Engine-Propeller of COGAG
Authors: Wang Zhitao , Ma Jiayi , Yu Haichao , Li Tielei 
Published: September 2021

Abstract
The combined gas turbine and gas turbine power propulsion device (COGAG power propulsion device) is an advanced combined power system, which uses multiple gas turbines as the main engine to drive propellers to propel the ship. COGAG power propulsion device has high power density, excellent stability and maneuverability, it receives more and more attention in the field of ship power at home and abroad. This article takes the COGAG power propulsion device as the research object, uses simulation methods to study its steady-state operating characteristics, and conducts a ship-engine-propeller optimization matching analysis based on economy and maneuverability. The research work carried out in this article is as follows.
Firstly, according to the structural relationship between the various components and the system thermal cycle mode of the COGAG power propulsion device, establish the controller, main engine, gear box, clutch, shafting, propeller, ship and other components and simulation models of the system with the modular modeling idea.
Secondly, divide the gears according to ship speed. For the four working modes of single-gas turbine with load, dual-gas turbine with load, three-gas turbine with load, and four-gas turbine with load, analysis the ship-engine-propeller optimization matching of the COGAG power propulsion device based on economy and maneuverability, and calculate the best shaft speed and propeller pitch ratio in each gear, so as to obtain the steady-state operation characteristics of the COGAG power propulsion device based on the ship-engine-propeller matching, which provides a basis for determining the target parameters of the dynamic process.
Identification of Slip Load, Friction Force and External Force Using Unscented Kalman Filter for Frictionally Damped Turbine Blades
Authors: Patel Himanshu , Sinha Alok 
Published: September 2021

Abstract
An Unscented Kalman Filter (UKF) based technique has been developed for parameter estimation of turbine blades with friction dampers. The technique is based on integration of Newmark method, an iterative numerical integration method for structural dynamics, with UKF. The technique has been implemented on a single mode model of a turbine blade with a friction damper. Two approaches are developed. First, both steady state vibration and known forcing data are used to estimate parameters such as friction force and slip load. These parameters are treated as additional states of the system and the augmented state space model is used with UKF to estimate parameters. In the second approach, transient vibration response of the system is used to estimate slip load, friction force and unknown sinusoidal forcing function as well. The frequency of sinusoidal external excitation is assumed to be known. The unknown magnitude and phase of the external excitation are represented as a solution of a second order differential equation, which leads to two additional states in the model. Numerical results are presented for both the cases of known and unknown forcing functions in the presence of modeling and measurement errors. A discussion of these results is presented and the validity of the new approach is corroborated.
Determination of the Area of Rational Use of Hybrid Bearings With Steel Rings and Ceramic Rolling Elements in High-Speed Aircraft Engines
Authors: Lavrentyev Yury , Petrov Nikolay , Nozhnitsky Yury 
Published: September 2021

Abstract
The process of improving gas turbine engines is associated with increased thermodynamic parameters and rotor speed. In advanced aircraft engines the main rotor bearings will operate at speed index dmn &gt; 3 · 106 mm · rpm, where dm is the bearing pitch diameter (mm), and n is the rotational speed (rpm). Under these conditions, significant heat is generated in the bearings, and the use of hybrid rolling bearings with steel rings and ceramic rolling elements looks more attractive due to the ceramic’s low density and low coefficient of thermal expansion.
A computational method for predicting the thermal state of rolling bearings operating at high speed parameters has been developed based on comparative tests of steel and hybrid rolling bearings. Knowing the thermal state of the bearing allows the value of the operating clearance to be set in the bearing, which is important for determining the contact angle and load distribution over the rolling elements.
A comparison with the results from tests of hybrid and steel bearings presented in the previous literature has shown that the calculated values correspond to the experimental data.
Criteria for selecting steel or hybrid bearings are proposed, and areas of rational use for hybrid rolling bearings in aircraft engines are determined.
Experimental Study on Different Tip Clearance of Low-Speed Axial Fan
Authors: Zhang Ming , Li Jia , Dong Xu , Sun Dakun , Sun Xiaofeng 
Published: September 2021

Abstract
Tip clearance flow is not only the source of undesirable noise but also a potential indicator for critical operating conditions with rotating stall or surge. It can induce blade vibration, which would cause premature blade failure when the vibration is strong enough. The paper presents experimental studies on the effects of tip clearance on the stall inception process in a low-speed high-load single stage fan with different tip clearance. From the point of view of flow range, it has been proved by computations that there is an optimal gap value, and an explanation is given according to different stall mechanisms of large and small tip clearance. However, the experiment of no tip clearance is not easy to achieve. In this experiment, a wearable soft wall casing was used to achieve “zero clearance”, and an explicit conclusion was obtained. The pressure rise and efficiency are improved at small tip clearance. Instantaneous Casing Pressure Field Measurement was carried out: instantaneous casing pressure fields were measured by 9 high response pressure transducers mounted on the casing wall. At the near stall point with large tip clearance, a narrow band increase of the amplitudes in the frequency spectrum at roughly half of the blade passing frequency can be observed according to the spectrum of static pressure at points on the endwall near the leading-edge and above the rotor. This phenomenon was explained from two aspects: tip clearance flow structure and pressure signal spectrum.
Theoretical Study on Static Performance of Double-Bump Foil Bearings
Authors: Xu Fangcheng , Chu Jianhua , Luan Wenlin , Zhao Guang 
Published: September 2021

Abstract
In this paper, single-bump foil models with different thickness and double-bump foil models with different initial clearances are established. The structural stiffness and equivalent viscous damping of double-bump foil and single-bump foil are analyzed by finite element simulation. The results show that the double-layer bump foil has variable stiffness and the displacement of the upper bump is greater than the initial gap when the two-layer bumps contact. A model for obtaining static characteristics of aerodynamic compliant foil thrust bearing is established on the basis of the stiffness characteristics of the double-bump foil. This paper solves gas Reynolds equation, the gas film thickness equation and the foil stiffness characteristic equation via the finite element method and the finite difference method. The static characteristics of the thrust bearings including the bearing pressure distribution, the gas film thickness and the friction power consumption have been obtained. The static characteristics of two kinds of foils have been compared and analyzed, and the effect of initial clearance on the static performance of double-bump foil bearings is studied. The results show that the double-bump foil structure can effectively improve the load capacity of thrust bearing. In addition, the static performance of double-bump foil thrust bearings is between the performance of the single-bump foil bearing and the double-bump foil bearing whose foil’s clearance is zero. The smaller the initial clearance is, the easier it will be to form a stable double-bump foil supporting structure.
Open Source Axial Compressor Mean-Line Design Tool for Supercritical Carbon Dioxide
Authors: Wells Kaden , Turner Mark G. 
Published: September 2021

Abstract
This paper presents an open-source axial compressor design code developed for applications using Supercritical CO2 (S-CO2). Real property tables are generated using REFPROP (Reference Fluid Thermodynamic and Transport Properties Database) linked to MATLAB. These tables are created and are provided for S-CO2 and could be created for any fluid in the database. At this time, only a single-phase fluid has been implemented. The tables are imported into the mean-line code and are interpolated with cubic splines to calculate real properties based on two given properties. The mean-line code is written in Python to allow portability and convenient plotting capability. The inputs are simple ascii files with the overall compressor details, stage data, and an optional IGV file. The code uses the axial flow equations of continuity, energy, and angular momentum in addition to velocity triangles to calculate state properties at every station. A free vortex assumption at each between-blade row station is used to calculate information at hub, pitch, and tip. The input for each stage includes the Mach number and absolute flow angle at the rotor leading edge in addition to the total enthalpy rise across each rotor. Loss coefficients, solidity, aspect ratio and axial spacing are also specified for each blade row along with blockage to account for wakes, boundary layers, and bleed. A hub radius is also specified. These parameters allow for a complete set of realistic inputs for the design of axial compressors using S-CO2 as the working fluid. The output can be used to assess the design and is used as the start of higher fidelity design.
Comparison of Model Order Reduction Methods in Thermoacoustic Stability Analysis
Authors: Purwar Naman , Meindl Maximilian , Polifke Wolfgang 
Published: September 2021

Abstract
Model order reduction can play a pivotal role in reducing the cost of repeated computations of large thermoacoustic models required for comprehensive stability analysis and optimization. In this proof-of-concept study, acoustic wave propagation is modeled with a 1D network approach, while acoustic-flame interactions are modeled by a flame transfer function. Three reduction techniques are applied to the acoustic subsystem: firstly modal truncation based on preserving the acoustic eigenmodes, and then two approaches that strive to preserve the input-output transfer behavior of the acoustic subsystem, i.e., truncated balanced realization and iterative rational Krylov algorithm. After reduction, the reduced-order models (ROMs) are coupled with the flame transfer function. Results show that the coupled reduced system from modal truncation accurately captures thermoacoustic cavity modes with weak influence of the flame, but fails for cavity modes strongly influenced by the flame as well as for intrinsic thermoacoustic modes. On the contrary, the coupled ROMs generated with the other two methods accurately predict all types of modes. It is concluded that reduction techniques based on preserving transfer behavior are more suitable for thermoacoustic stability analysis.
Air-Steam Dual Loop Gas Turbine Engine With Pulse Detonation Combustion
Authors: Nageswara Reddy Pereddy 
Published: September 2021

Abstract
Air-steam Dual Loop Gas Turbine Engine (DLGTE) consists of a gas turbine engine with Pulse Detonation Combustor (PDC) (operating by the Humphrey cycle) with the air as the working fluid and a steam turbine engine (operating by the Rankine cycle) with the steam as the working fluid. The temperature of the hot detonation products is reduced to Turbine Inlet Temperature (TIT) by exchanging heat energy between detonation products and water in a Detonation Products to Water Heat Exchanger (DPWHE). The thermodynamic cycle of operation of DLGTE with PDC is analyzed based on quasi-steady state one dimensional formulation, and a computer code is developed in MATLAB to simulate the engine performance at different compressor pressure ratios and TITs. C2H4/air is taken as the fuel-oxidizer. It is found that DLGTE with PDC achieves 40 to 47% thermal efficiency as against 20 to 35% of Base Line Gas Turbine Engine (BLGTE) and 27 to 40% of Combined Cycle Gas Turbine Engine (CCGTE) with a Steady Flow Combustor (SFC) depending on the cycle pressure ratios and TITs. The specific work output of DLGTE is found to increase from 875 to 1200 kJ/kg air as against 180 to 380 kJ/kg air of BLGTE and 200 to 430 kJ/kg air of CCGTE.
Experimental and Computational Investigation of Film Cooling Performance and External Flowfield Effects due to Impingement Coolant Feed in the Leading Edge of a Turbine Blade
Authors: Moore Jacob D. , Easterby Christopher C. , Bogard David G. 
Published: September 2021

Abstract
The effects that leading-edge impingement coolant feeds have on the external flowfield and on film cooling performance in the showerhead have not been studied thoroughly in the literature. To isolate the influence of the impingement feed, experimental adiabatic effectiveness and off-the-wall thermal field measurements were made using a shaped hole geometry fed by an ideal plenum coolant feed and by an engine-realistic impingement coolant feed. The impingement configuration exhibited around 10% higher adiabatic effectiveness levels than the plenum configuration did — a finding in agreement with the few studies isolating this effect. CFD RANS simulations of the impingement and the pseudo-plenum configurations from a companion study were consulted to investigate the root cause of this difference in performance because the experimental data alone did not sufficiently explain it. In the impingement feed simulation, flow remained better attached throughout the hole (both at the inlet and at the diffuser) due to a rotation caused by the impingement flow, leading to better attachment on the exterior surface. This was most significant for the suction side holes at higher blowing ratios wherein the pseudo-plenum caused much more severe separation in the holes than the impingement configuration did.
An Unconventional Method for the Diagnosis and Study of Generator Rotor Thermal Bows
Authors: Chatterton Steven , Pennacchi Paolo , Vania Andrea 
Published: September 2021

Abstract
The rotor thermal sensitivity often affects the dynamic behavior of power unit generators. Owing to this phenomenon, increments of field current and other process parameters that are related to it may cause a shaft thermal bow and significant changes in the synchronous vibration. This symptom can also be caused by many other common malfunctions that affect rotating machines. Therefore, diagnostic techniques aimed at identifying the actual fault are very useful for optimizing maintenance activities. The thermal sensitivity of generator rotors can be deemed as a fault because it is commonly caused by a local deterioration of the winding insulation as well as by jamming phenomena between conductors and rotor slots, caused by friction forces due to the different thermal expansions of these components. This paper shows the results obtained applying a diagnostic method, based on multiple linear regression models, which has been developed for the analysis of generator vibrations caused by thermal sensitivity. Nevertheless, nonlinear relationships between vibration and process parameters have also been taken into account. The capabilities of this diagnostic technique have been validated using the analysis of experimental data collected in a power plant. The results of this investigation are shown and discussed in the paper.
Isentropic Formulation of the Linearized Euler Equations For Perfectly Premixed Combustion Systems
Authors: Romero Vega Pedro , Hofmeister Thomas , Heilmann Gerrit , Hirsch Christoph , Sattelmayer Thomas 
Published: September 2021

Abstract
The linearized Euler equations (LEE) provide an accurate — yet computationally efficient — description of propagation and damping of acoustic waves in geometrically complex, non-uniform reactive mean flows like those found in gas turbine combustion chambers. However, direct application of the LEE to perfectly premixed combustors with highly turbulent flows overestimates entropy waves as the LEE solution inherently contains coupled acoustic, vortical and entropy modes. In the present work, the LEE are decomposed into isentropic and non-isentropic parts ultimately obtaining a simplified set of isentropic LEE, in which only acoustic and vortical modes propagate. In the isentropic LEE, only continuity and momentum equations need to be solved. The energy equation is replaced by the isentropic relation between acoustic pressure and density. From the decomposition, the unsteady heat release term, which acts as a source in the energy equation, naturally arises as a source in the continuity equation. This way, the thermoacoustic coupling is still preserved in the isentropic formulation. The derived isentropic set of equations is first tested with a one-dimensional benchmark configuration consisting of a mean flow temperature jump, non-uniform mean flow velocity and unsteady heat release sources. Solutions of the non-isentropic and isentropic set of LEE are compared and the avoidance of entropy waves proved. Finally, isentropic LEE are used for reproducing the frequency of the self-excited first transversal mode of a lab-scale swirl-stabilized premixed combustor. Furthermore, isentropic and non-isentropic LEE solutions are compared. The non-isentropic LEE yield too high levels of entropy at the combustor exit that may explain the increased damping rate of the non-isentropic LEE solution compared to the isentropic LEE solution. This shows the relevance of isentropic LEE for correctly predicting thermoacoustic stability limits at high frequencies in relevant industrial applications.