bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Turboshaft Engine Architecture on Ash Particle Deposition: Reduced Order Model Application
Authors: Ellis Matthew , Bojdo Nicholas , Filippone Antonio 
Published: January 2021

Abstract
Particles ingested by aero gas turbines are capable of melting in the combustor and depositing on high pressure turbine vane surfaces, where they degrade aerodynamic and thermodynamic performance. The extent of the damage caused is a complex physical process dependent on the thermal and inertial properties of the particles, the operating state of the engine and importantly, engine architecture. The dominant architecture considerations are the position of the burner flames relative to the nozzle guide vane leading edges and the temperature difference across the burner flames. In this work, we investigate the influence of this on particle deposition by approximating the temperature variation of the hot streak as a sinusoidal profile. A parametric analysis is carried out using numerical simulations and an elastic-plastic particle deposition model, to evaluate the effect of mean temperature, temperature difference across the hot streak, and hot streak position on the deposition rate of a generic particle size distribution. Results show that the dominant effect driving particulate deposition is a combination of the gas temperature, hot streak position relative to the vane leading edge and the particulate type. The rate of deposition on a vane for sub-bituminous ash particles may be reduced by up to 56% if the combination of mean temperature, temperature difference across the hot streak, and hot streak position are chosen carefully.
Industrial Challenges in Large Thermally Enabled Structural Whole Engine Models
Authors: Tindall Michelle , Keskin Akin , Layton Andrew 
Published: January 2021

Abstract
Understanding gas turbine design at a system level presents a difficult challenge. Accurate predictions of gas turbine behaviour before whole engine tests are completed are invaluable in preventing costly design changes in the latter stages of the design life cycle. In this study a high fidelity whole engine model has been built — specifically, a thermally enabled structural model. This model can predict component displacements up to system level interactions across the whole engine. Knowledge from such a model can feed into multiple design areas contributing to performance, component design and structural understanding but can also be used to influence physical testing.
There are clear benefits in building such high fidelity models but also many challenges that need to be addressed, namely solver type, geometry interrogation, meshing, solver capability, computational power and finally, processing and validation of output data. Additionally, different applications have been used for thermal and structural modelling in order to utilise best capabilities in thermal and contact modelling but also enable scalability on high performance computing. However, utilising two different solvers involves meshes being tailored for each solver type but also introduces additional complexity of transferring information between the two models used.
The paper will discuss the challenges and analysis methodologies used to thermally solve the whole engine cycle, the mapping procedure to translate thermal data to a structural model, and the approach taken to solve the very large simulation model explicitly at a chosen condition to a pseudo-steady state. In order to validate the simulation results, a vast amount of time has been spent to compare the results to existing test data.
As model validation is a significant step in simulation to gain credibility of the results, a comparison of the predicted component displacements will be shown to X-ray data from a whole engine test. Results and limitations of this testing capability such as influence of engine vibration, shutter speed and noise in the data will be discussed and recommendations provided to improve accuracy of the results.
Cooling Improvement of Gas Turbine Rotary Blades
Authors: Rasimarzabadi Faezeh , Kamalimoghadam Ramin , Najafi Mahmoud , Mohammadi MohammadReza , Sahranavard Fard Nasrin 
Published: January 2021

Abstract
A new method is presented to improve cooling of the turbine blades by using active extraction from the compressor outlet to supply more cooling air with more energy. The cool air is extracted from the end of compressor through a set of peripheral holes to the air transferring channels on the disc edge or torque tube using the tangential velocity vector of the rotating shaft which results in increasing the amount and energy of the cooling air. In fact a forward angle of inlet holes for the channels is used to help the pressurized air overcome the air centrifugal force and to accelerate the flow going into the torque tube. To investigate the effect of new idea, both the original and proposed models are analyzed using 3D CFD simulation on a selected physical domain of a gas turbine. The compressible rotating Navier-Stokes equations are used for numerical simulation of two geometries. The governing equations, mesh treatment, boundary conditions and numerical setup are described. The calculation results are compared to those of the original turbine shaft to show the heat transfer improvement by enhancing the cooling flow rate and fluid energy.
Unsteady Effects due to Rotor Purge Flow Variations in a Dual-Spool Turbine Setup
Authors: Merli F. , Sterzinger P. Z. , Dellacasagrande M. , Wiesinger L. , Peters A. , Heitmeir F. , Göttlich E. 
Published: January 2021

Abstract
The paper discusses the impact of rotor purge flows on the unsteady flow field downstream of a two-stage, two-spool test turbine. The analyzed setup is representative of the second high-pressure turbine (HPT) and the first low-pressure turbine (LPT) stage in a modern turbofan aero-engine, with a turbine center frame (TCF) with non-turning struts in-between the two turbines. All measurements were carried out for an engine-representative test vehicle setup at the Transonic Test Turbine Facility at Graz University of Technology. The test rig features a secondary air system delivering five purge flows with independent temperature and mass flow control to the HPT and LPT cavities.
This work extends the results shown in two recent publications analyzing the time-resolved flow through the same two-stage setup at fixed purge flow rates. The paper aims to provide additional input about the driving sources of unsteadiness in gas turbines for aeronautic applications, by isolating the HPT and LPT purge air contributions.
The time-resolved flow field at the LPT exit was acquired with a Fast Response Aerodynamic Pressure Probe (FRAPP) for three different purge conditions (reference case, no HPT purge case, no LPT purge case), to separate and quantify the impact of HPT and LPT purge contributions on the main flow field. The so-called Rotor Synchronic Averaging (RSA) technique was used as phase-averaging approach, to account for the unsteadiness due to both rotors. Proper Orthogonal Decomposition (POD) was then applied to isolate the most important structures and identify their origins. The comparison of the three data-sets shows a significant influence of the HPT purge on the entire flow field at the LPT exit, even though the HPT is located far upstream, while the LPT purge impact appears to mostly affect the end-wall region.
A Self-Tuning Model Framework Using K-Nearest Neighbors Algorithm
Authors: Yang Shu-Bo , Alafate Julaiti , Wang Xi , Tian Zhen 
Published: January 2021

Abstract
Benchmark models are indispensable for gas turbine engine monitoring and diagnostics. In most cases, benchmark models are used to predict engine data. When the measured data from a real engine does not match up the predicted data, it means that something undesirable is going on and the engine may need servicing.
Generally, the benchmark models are also thermodynamic models. They are either offered by engine manufactures or obtained using the technique called “performance adaptation”. In both cases, those models have a major limitation: they cannot reflect the development of engine deterioration over time, i.e., deterioration parameters of these models are fixed unless manually adjusted. In practice, however, most engines deteriorate continuously and gradually over time. Due to the increasing mismatch of deterioration, the accuracy of the benchmark model will get worse gradually.
To address the mismatch, this paper presents a self-tuning model framework that intends to improve the existing benchmark models. In the framework, a set of deterioration models are introduced and attached to the original benchmark model. The deterioration models represent the deterioration conditions of all major components. They are machine learning models and can be updated automatically according to the engine measurements. With the aid of the k-nearest neighbours algorithm and gas path analysis techniques, the deterioration models can track the real deterioration conditions through self-tuning and are robust under noise. The proposed model framework is applied to a model turbofan engine. Simulation results show that the accuracy of the benchmark model improves significantly after using the self-tuning framework.
Investigation of Endwall Heat Transfer in Staggered Pin Fin Arrays
Authors: Otto Marcel , Gupta Gaurav , Tran Patrick , Ghosh Shinjan , Kapat Jayanta 
Published: January 2021

Abstract
Arrays of staggered pin fins are a typical geometry found in the trailing edge region of modern airfoils. If coolant is supplied by bleeding from the mid-section of the airfoil instead of provided through the root, the channel length is not long enough to reach a fully developed flow which is commonly found from the fifth row downstream. This present study focuses on the developing section (four rows) of a staggered array with a height to diameter ratio of 2 and a spanwise and streamwise spacing of 2.5 respectively. Measurements are conducted at two Reynolds numbers of 10,000 and 30,000 based on the maximum velocity and pin diameter. Stereoscopic PIV is used to describe the flow field and turbulence characteristics in the wake of the first and third row pin. It is found that the dominating vortical structures depend highly on the Reynolds number. A transient thermochromic liquid crystal technique is used to obtain local heat transfer coefficients on the endwall which are then discussed in the context with the vortical structures. The structure of the horseshoe vortex and the transient wake shedding behave differently in the first and second row. The interaction of both vortex systems affects directly the endwall heat transfer. The results are supplemented by a thorough discussion of TLC and PIV uncertainty.
Numerical and Experimental Aerodynamic Investigation of an S-Shaped Intermediate Compressor Duct With Bleed
Authors: Siggeirsson Elias M. V. , Andersson Niklas , Burak Olander Markus 
Published: January 2021

Abstract
A series of CFD simulations are performed to analyse the effects a rotor off-take bleed has on the performance of an Intermediate Compressor Duct (ICD). To validate the CFD results, a comparison is made to measurements obtained from an experimental facility located at GKN Aerospace Engine Systems in Sweden. To achieve a deeper understanding of the flow physics, hybrid RANS/LES simulations are performed for a single operating condition. The CFD simulations are capable of predicting the behavior when extracting large amount of air through the bleed pipe, where an improved prediction is obtained with the hybrid simulation. The performance of the ICD is severely compromised with increased amount of bleed as the flow delivered to the downstream component is highly disturbed. The disturbed flow is caused by the extraction of axial flow through the bleed pipe, increasing the incidence into the low-pressure compressor’s outlet guide vanes resulting in unfavorable velocity profiles into the ICD. This behavior causes the flow to separate at the OGV blades, where the separation increases with increase bleed. Furthermore, when including the full bleed system, significant circumferential distortions are observed, showing the necessity of the integrated design.
Interaction Between Coriolis Forces and Mistuning on a Cyclic Symmetric Structure With Geometrical Nonlinearity
Authors: Tacher Anthony , Thouverez Fabrice , Armand Jason 
Published: January 2021

Abstract
An investigation of the interaction between Coriolis forces and mistuning on a cyclic symmetric structure is presented in this paper. The sensitivity of the eigenvalues and eigenvectors to mistuning is first studied with the perturbation method. A lumped parameter model is used to perform a modal analysis using a numerical approach after which geometrical nonlinearity is added to compare behavior with the linear case. Two different modes are thoroughly investigated for different rotational speeds, the first with an eigenvalue isolated from the others and the second presenting a frequency veering zone. The evolution from a standing wave domination at low speeds to a travelling wave domination at high speeds is observed for the isolated mode, whereas a standing wave domination remains around the veering zone for the second mode studied. It is also shown that the geometrical nonlinearity reinforces the mistuning effect versus the Coriolis forces.
Unsteady Numerical Investigation on Film Cooling Characteristics of the Trailing Edge Cutback With Upstream Cylinder Hole
Authors: Xiao Xiangtao , Wang Pei , Xu Qingzong , Du Qiang , Liu Jun , Chang Sheng 
Published: January 2021

Abstract
The trailing edge cutback is often applied when designing the film cooling structure of a high-pressure turbine. Previous studies have demonstrated strong unsteady film mixing process which is indeed influenced by the vortex shedding from the pressure side lip. Thus, adiabatic film cooling effectiveness on cutback rapidly declines at streamwise direction. To obtain high film cooling performance, this paper arranges a cylinder hole on pressure side upstream of the trailing edge cutback flat-plate model. The film cooling characteristics of combined configuration are investigated with unsteady numerical method. DES turbulence model has been proved to capture the vortex shedding well. The mainstream Reynold number is Rem = 360000 based on the length from inlet to lip. The total coolant-to-mainstream blowing ratio is M = 0.5 and cylinder hole is arranged at three different positions (X/H = −4, −6, −8). Firstly, film cooling performance of two configurations (cutback, cutback with a cylinder hole at X/H = −6) are compared. The results indicate that the mainstream temperature and velocity greatly reduce due to hole coolant ejection. The vortex shedding downstream of lip is weakened contributing to less film mixing on the trailing edge cutback. The lateral-averaged adiabatic film cooling effectiveness increases especially downstream of cutback. Then three combined configurations of hole at different positions show that all configurations can improve film cooling performance of the trailing edge cutback. When cylinder hole is arranged closer to lip, adiabatic film cooling effectiveness increases more.
Numerical Study of a Small-Scale Micro Gas Turbine-ORC Power Plant Integrated With a Biomass Gasifier
Authors: Reale Fabrizio , Sannino Raniero , Calabria Raffaela , Massoli Patrizio 
Published: January 2021

Abstract
The paper is focused on coupling a small-scale power plant, based on a micro gas turbine (mGT) and a bottoming Organic Rankine Cycle (ORC), with a biomass gasifier. The aim of this study is to define the optimal strategies to maximize the benefits related to distributed generation and to promote the organic solid waste gasification, in terms of energy efficiency and renewable sources exploitation. In particular, they were investigated the energetic performances of the system when the micro gas turbine was fed with several fuel blends, made by specific volume concentration of syngas and biogas. The low heating value of both considered fuels implies the necessity of operating the mGT in peculiar conditions as determined by the performance maps of compressor and turbine. Then, the thermodynamic analyses of the whole energy system have been carried out to evaluate the performance for each fuel. The high hydrogen content of syngas and the different thermodynamic properties of the studied fuel blends required a deeper investigation of the combustion process. In order to analyze the combustion stability and the fluid dynamic aspects, an accurate investigation of combustion chamber has been performed through a CFD solver. Finally, a comparison of the plant performances for each fuel blend have been reported, along with opportunities and critical aspects related to power plant integration.
Using Blade Tip Timing and Pressure Data to Characterise Compressor Stall and Surge
Authors: Przysowa Radoslaw , Russhard Peter , Wachlaczenko Michal 
Published: January 2021

Abstract
Rotating stall and surge are common phenomena in compressors, and related research has been carried out since the invention of the gas-turbine engine. Signals of fast response pressure sensors analysed with spectral methods based on Fourier transform are primarily used to characterise compressor stall. This article focuses on the application of blade tip timing (BTT) for this purpose and aims to demonstrate current analysis capabilities, issues and challenges related to practical applications. By using real engine test results, we show that BTT provides more information at the cost of more complex analysis. The signals of four tip timing and three pressure probes installed in the first compressor stage are processed. We observed flow disturbances and blade responses caused by objects located in the inlet at a constant speed and also surge events during snap acceleration. All-blade spectrum and modal tracking are used to identify the presence of non-integral vibration and to determine the nominal frequency and nodal diameter. This data seeds the Least Squares Fitting, which delivers amplitude and phase. A method for sensor fusion is presented. For the selected non-integral responses, tip timing and pressure results are evaluated to show how they can complement each other. The proposed methodology can be used both for compressor development and Blade Health Monitoring.
Application of Immersed Boundary Method on Instrumented Turbine Blade With LES
Authors: Ubald Bryn N. , Watson Rob , Cui Jiahuan , Tucker Paul , Shahpar Shahrokh 
Published: January 2021

Abstract
Leading edge instrumentation used in compressor and turbine blades for jet-engine test rigs can cause significant obstruction and lead to a marked increase in downstream pressure loss. Typical instrumentation used in such a scenario could be a Kiel-shrouded probe with either a thermocouple or pitot-static tube for temperature/pressure measurement. High fidelity analysis of a coupled blade and probe requires the generation of a high quality mesh which can take a significant amount of an engineers time. The application of Immersed Boundary Method (IBM) and Large Eddy Simulation is shown in this paper to enable the use of an extremely simple mesh to observe the primary flow features generated due to the blade and probe interaction effects, as well as quantify downstream pressure loss to within a high level of accuracy. IBM is utilised to approximately model the probe, while fully resolving the blade itself through a series of LES simulations. This method has shown to be able to capture downstream loss profiles as well as integral quantities compared to both experiment and fully wall-resolved LES without the need to spend a significant amount of time generating the ideal mesh. Additionally, it is also able to capture the turbulence anisotropy surrounding the probe and blade regions.
Integrally Bladed Rotor Mistuning Identification and Model Updating Using Geometric Mistuning Models
Authors: Beck Joseph A. , Brown Jeffrey M. , Gillaugh Daniel L. , Carper Emily B. , Kaszynski Alex A. 
Published: January 2021

Abstract
Non-uniform manufacturing variations and uneven usage wear and damage, referred to as mistuning, can drastically alter the dynamic response of Integrally Blade Rotors (IBR)s. Optical scanners, combined with Finite Element Model (FEM) mesh metamorphosis algorithms, have provided capabilities to create analytical models that reduce the effect of geometrical uncertainties in numerical predictions. However, deviations in material properties cannot be obtained via optical scanning, so additional approaches are needed. A geometric mistuning Reduced-Order Model (ROM) is developed and modified to solve for unknown IBR sector eigenvalues that are linearly proportional to Elastic modulus. The developed approach accounts for both proportional and non-proportional mistuning and allows updating of the Elastic modulus for each sector in the ROM. Different tuned and mistuned modal reduction procedures are employed to understand the implications of each for identifying mistuning. Simulated test data with known inputs indicate the efficiency and accuracy of the method and improvements over using a traditional, tuned mode approach. The developed methods are then extended to bench-level traveling wave excitation data to discern how sector frequencies vary due to geometry and modulus mistuning.
Numerical Investigation on Unsteady Characteristics in Different Rim Seal Geometries: Part B
Authors: Lian Zengyan , Du Qiang , Liu Guang , Wang Ruonan , Xie Lei 
Published: January 2021

Abstract
Hot gas ingestion into the wheel space can reduce the lifetime of vulnerable components in gas turbine like the turbine disk. Rim seal structure at the periphery of the wheel-space is designed to protect the turbine disk from hot gas. This paper describes the steady and unsteady Reynolds-averaged Navier-Stokes (RANS and URANS) computation method with Shear Stress Transport (SST) turbulent model using commercial CFD code and the validation of grids. The RANS and URANS computation have been carried out in a one stage turbine model with different rim seal configurations: fish-mouth rim seal and double rim seal. A 10.91° sector computation model comprises one pitch in a row of stator vanes, and rotor blades is set up and simulated with different sealant flow rate. Results show that the fish-mouth rim seal can achieve higher sealing effectiveness with low sealant flow rate by installing the inner shell at high radius on the stator disk. The comparison between the steady and unsteady results indicates that the RANS computation underpredicts the level of the hot gas ingestion, especially in the double rim seal configuration. It can be found in the URANS computation results at different time steps that, when the rotating effect is considered, the interaction between the vane wake and the wave of the blade leading edge can lead to more serious pressure asymmetry, which worsens the hot gas ingestion. The counter-rotating vortex induced at outer wheel space and the Kelvin-Helmholtz-like vortices caused by velocity difference of mainstream and sealing flow can further aggravate the ingress.