bluuebunny/crossref_metadata_2025_split huggingface dataset:
Re-Ingestion of Upstream Egress in a 1.5-Stage Gas Turbine Rig
Authors: Scobie James A. , Hualca Fabian P. , Patinios Marios , Sangan Carl M. , Owen J. Michael , Lock Gary D. 
Published: August 2017

In gas turbines, rim seals are fitted at the periphery of stator and rotor discs to minimise the purge flow required to seal the wheel-space between the discs. Ingestion (or ingress) of hot mainstream gases through rim seals is a threat to the operating life and integrity of highly-stressed components, particularly in the first-stage turbine. Egress of sealing flow from the first-stage can be re-ingested in downstream stages.
This paper presents experimental results using a 1.5-stage test facility designed to investigate ingress into the wheel-spaces upstream and downstream of a rotor disc. Re-ingestion was quantified using measurements of CO2 concentration, with seeding injected into the upstream and downstream sealing flows. Here a theoretical mixing model has been developed from first principles and validated by the experimental measurements. For the first time, a method to quantify the mass fraction of the fluid carried over from upstream egress into downstream ingress has been presented and measured; it was shown that this fraction increased as the downstream sealing flow rate increased. The upstream purge was shown to not significantly disturb the fluid dynamics but only partially mixes with the annulus flow near the downstream seal, with the ingested fluid emanating from the boundary layer on the blade platform. From the analogy between heat and mass transfer, the measured mass-concentration flux is equivalent to an enthalpy flux and this re-ingestion could significantly reduce the adverse effect of ingress in the downstream wheel-space. Radial traverses using a concentration probe in and around the rim seal clearances provide insight into the complex interaction between the egress, ingress and mainstream flows.
Distinguishing Primary and Secondary Loads to Support Gas Turbine Blades and Vanes Design
Authors: Riva Andrea , Elli Stefano , Nussbaum Julien 
Published: August 2017

Creep mechanisms are present in heavy duty gas turbine blades and vanes due to the simultaneous presence of high temperature and high stresses. Therefore, the microstructural phenomena (dislocation movement and atomic diffusion) that occur and accumulate during service are able to convert part of the initial elastic field of strain into permanent creep strain. This also induces a global redistribution of stresses. The progressive accumulation of creep strain can, in some extreme cases, produce changes and damage in the material (gamma prime rafting, porosity) and can eventually lead to component failure.
This work shows how the understanding of the nature of the load significantly affect the capability of creep strain to produce damage. In fact, it is shown how both primary (non-self-limiting) and secondary (self-limiting) loads are both capable to generate a significant amount of creep strain, but the microstructural damage is more easily generated by relentless primary loads, generated by external forces such as the rotor blade centrifugal force (or, in other components, external gas pressure, dead weight). In the case of turbine blades and vanes, due to the complexity of the component, it is challenging to quantitatively distinguish relentless primary from self-limiting secondary stresses or simply thermal from mechanical contributions. This work is aimed to provide the designer with tools to perform such distinction and support the interpretation of the creep calculations. The proposed methodologies are developed to improve the accuracy of the prediction of the creep damage in turbine blades and vanes, but they can also be used for other purposes (e.g. predict the hysteresis cycle shift, support the estimation of the plastic strain on the basis of an elastic FE calculation), as illustrated in the paper.
An Explicit-Implicit Time Integration Approach for Finite Element Evaluation of Engine Load Following an FBO Event
Authors: Weng Yiliu , Zheng Lipeng 
Published: August 2017

Engine fan blade-off (FBO) is an extreme event that could well place the flight safety at risk. When it happens, the engine will experience high-velocity impact at first, and then enter into a “high-power” stage due to huge unbalance before coming to a steady state called “windmilling”. The analytical process for FBO can be split into two phases, one for impact simulation and the other for obtaining the FBO load to pylon. Typically, explicit method with fine mesh finite elements is used in the first phase, and implicit method with coarse meshes is adopted in the second one. In most cases, the only connection between these two analyses may be the unbalance level caused by FBO. More structural responses other than the unbalance level due to fan blade impact are actually ignored in the succeeding implicit analysis. Attempts have been made by Boeing, GE and MSC to integrate these two processes by adding some features in MD Nastran. Yet the intermediate binary files created and the restricted input entries make the integration process quite inflexible.
This paper introduces an explicit-implicit time integration approach for finite element analysis of engine load following an FBO event. The proposed method attempts to connect the two stages more closely, yet in a more flexible manner. In this approach, the engine structural response under FBO obtained from explicit analysis is transferred to the implicit analysis, together with the unbalance level caused by blade loss. The necessity of the approach is discussed, and sensitivity analysis is conducted to understand the factors that play significant roles in the approach. As the models for explicit and implicit analyses are different in mesh sizes and scales, the authors also develop a tool that can interpolate the load information and further, smooth it to fit calculation. Finally, the approach is tested on a full engine model to show its applicability and advantages over the traditional method for load evaluation of FBO event.
LES Analysis of Flow and Heat Transfer in a Rib-Roughened Duct in Clockwise and Anti-Clockwise Rotation Regimes
Authors: Salvagni Alessandro , Borello Domenico 
Published: August 2017

We report on an LES study of effects of stabilising/destabilising rotation on heat transfer over a ribbed surface in a rectangular duct at Re = 15000. The duct bottom wall, ribbed by flow-normal, equally-spaced square-sectioned ribs, was uniformly heated (except for the ribs) by a constant heat flux. The duct was rotated with angular velocity corresponding to the rotation number of 0.3, around an axis parallel to the ribs in counter-clockwise (clockwise) direction, thus destabilising (stabilising) the ribbed-wall adjacent flow.
These well-resolved LES gave some new insight into the rotation effects on flow and heat transfer providing information that are not easily accessible by experiments. An attempt was made to identify the heat transfer effects due to the rotation-induced modifications of the secondary motion.
An Approach for Efficient CFD Simulations of an Ejector Air Injection System for Active Aerodynamic Compressor Stabilization
Authors: Brehm Sebastian , Kern Felix , Raub Jonas , Niehuis Reinhard 
Published: August 2017

The Institute of Jet Propulsion at the University of the German Federal Armed Forces Munich has developed and patented a novel concept of air injection systems for active aerodynamic stabilization of turbo compressors. This so-called Ejector Injection System (EIS) utilizes the ejector effect to enhance efficiency and impact of the aerodynamic stabilization of the Larzac 04 two-spool turbofan engine’s LPC. The EIS design manufactured recently has been subject to CFD and experimental pre-investigations in which the expected ejector effect performance has been proven and the CFD set-up has been validated. Subsequently, optimization of the EIS ejector geometry comes into focus in order to enhance its performance. In this context, CFD parameter studies on the influence of in total 16 geometric and several aerodynamic parameters on the ejector effect are required. However, the existing and validated CFD set-up of the EIS comprises not only the mainly axisymmetric ejector geometry but also the highly complex 3D supply components upstream of the ejector geometry. This is hindering large scale CFD parameter studies due to the numerical effort required for these full 3D CFD simulations. Therefore, an approach to exploit the overall axissymmetry of the ejector geometry is presented within this paper which reduces the numerical effort required for CFD simulations of the EIS by more than 90%. This approach is verified by means of both experimental results as well as CFD predictions of the full 3D set-up. The comprehensive verification data set contains wall pressure distributions and the mass flow rates involved at various Aerodynamic Operating Points (AOP).
Furthermore, limitations of the approach are revealed concerning its suitability e.g. to judge the response of the attached compressor of future EIS designs concerning aerodynamic stability or cyclic loading.
Numerical Simulation With Adaptive Boundary Method for Predicting Time Evolution of Erosion Processes
Authors: Castorrini Alessio , Corsini Alessandro , Morabito Francescogiuseppe , Rispoli Franco , Venturini Paolo 
Published: August 2017

In the present study a new approach to simulate the time evolution of erosion of a target body is presented. An interface algorithm connecting two in-house codes for flow field and particle motion and deposition simulations is developed and presented. The flow solver produces the flow field which is taken as input by the particle tracking and deposition solver, which, in turn, provides the displacements of all the grid nodes due to erosion. The approach is still one-way coupling, since particle motion is governed only by the flow field which is not affected by the particles. However, the interface allows to account for the effect of erosion on flow field and particle motion.
This approach shows a big potential for those applications where a long time simulation is important but not possible with the classical numerical techniques.
Numerical Testing of a Trailing Edge Passive Morphing Control for Large Axial Fan Blades
Authors: Castorrini A. , Corsini A. , Sheard A. G. , Rispoli F. 
Published: August 2017

The concept of morphing geometry to control and stabilize the flow has been proposed and applied in several aeronautic and wind turbine applications. We studied the effect of a similar passive system applied on an axial fan blade, analysing potential benefits and disadvantages associated to the passive coupling between fluid and structure dynamics.
The present work completes a previous study made at the section level, giving a view also on the three-dimensional effects.
We use the numerical computation to simulate the system which defines a complex fluid-structure interaction problem. In order to do that, an in-house finite element solver, already used in the previous study, is applied to solve the coupled dynamics.
Design of Directional Probes for High-Frequency Turbine Measurements
Authors: Liu Zhe , Paniagua Guillermo 
Published: August 2017

Aerodynamic probes are prevalent in turbomachinery research and gas turbine monitoring. Regrettably, this measurement technique experiences limitations in the transonic range as well as high frequency. Calibrated numerical tools offer an alternative procedure to design suitable instrumentation for each turbine application. In this paper, all the numerical analyses were performed using unsteady Reynolds Averaged Navier Stokes (URANS), two and three-dimensional.
Firstly, two different probe geometries, oval and trapezoidal probe geometries were characterized at different incidence angles. In particular, the pressure recovery, angle sensitivity, induced vortex shedding unsteadiness at several yaw angles were evaluated. The studies were performed over a wide range of Mach numbers from subsonic to the transonic regime. The vortex shedding of the probe was also carefully analyzed. In a second evaluation, we selected the oval probe geometry including the line-cavity effects into the pressure tappings. The resonance frequency of line-cavity system was evaluated and compared with analytical calculations, as well as with the detailed analysis of Bergh and Tijdeman. The comparison of the pressure tapping readings with the actual input signal allowed the identification of the transfer functions, as well as the physical mechanisms that should be corrected during the measurements. Finally, 3D unsteady evaluations were implemented to compute the blockage effects, as well as the final frequency attenuation experienced by the piezo-resistive sensors.
Numerical Combustion and Heat Transfer Simulations and Validation for a Hydrogen Fueled “Micromix” Test Combustor in Industrial Gas Turbine Applications
Authors: Striegan C. , Haj Ayed A. , Kusterer K. , Funke H. H.-W. , Loechle S. , Kazari M. , Horikawa A. , Okada K. , Koga K. 
Published: August 2017

Hydrogen represents a possible alternative gas turbine fuel for future low emission power generation once it can be combined with the use of renewable energy sources for its production. Due to its different physical properties compared to other fuels such as natural gas, well established gas turbine combustion systems cannot be directly applied for Dry Low NOx (DLN) Hydrogen combustion. This makes the development of new combustion technologies an essential and challenging task for the future of hydrogen fueled gas turbines.
The newly developed and successfully tested “DLN Micromix” combustion technology offers great potential to burn hydrogen in gas turbines at very low NOx emissions. The mixing of hydrogen and air is based on the jet in cross-flow (JICF) principle, where the gaseous fuel is injected perpendicular into the crossing air stream. The reaction takes place in multiple miniaturized diffusion flames with an inherent safety against flashback and the potential of low NOx emissions due to a short residence time of the reactants in the flame region.
Aiming to further develop an existing burner design in terms of an increased energy density, a redesign is required in order to stabilize the flames at higher mass flows while maintaining low emission levels.
For this reason, a systematic numerical analysis using CFD is carried out, to identify the interactions of combustion, radiation and heat conduction in the adjacent burner wall by conjugate heat transfer (CHT) methods. Different combustion models are applied, starting from a hybrid eddy break-up model to more advanced turbulence-chemistry interaction approaches considering detailed chemical mechanisms. Those allow an improved prediction of the different NO-pathways of production and consumption. The results of the simulations are in good agreement with atmospheric test rig data of optical flame structure, measured combustor surface temperatures and NOx emissions.
The numerical methods help reducing the effort of manufacturing and testing to few designs for single validation campaigns, in order to confirm the flame stability and NOx emissions in a wider operating condition field. Further on, the more detailed CFD-simulations support the understanding of decisive mechanisms to reduce the numerical work to the most important models for further industrial applications in future.
Influence of Tip Geometry on Over Tip Leakage in Shrouded Rotor Blades With Cooling
Authors: Tessier Jeffrey , Vogel Gregory 
Published: August 2017

Gas turbine blades can be shrouded and designed with “knife edges” to reduce over tip leakages as an attempt to improve turbine stage efficiency. The smaller the tip gap is, the less the amount of leakage and consequently the higher the turbine efficiency. However a zero tip gap between the rotating blade and the stationary casing is simply not practical and not achievable for typical engine operations. One approach often consists of making the stationary shroud at the casing of abradable coating or of softer material in a honeycomb structure. In some cases, it is also common practice to pretrench the honeycomb structure to a certain height to reduce rubbing that could naturally occur with brand new hardware.
This paper details the physical effects occurring between trenched and un-trenched configurations and quantifies the potential loss in turbine stage efficiency and power under such changes.
Because front turbine stages are also cooled, this paper is also detailing the physical effects that are occurring between trenched and un-trenched configurations for a shrouded cooled turbine blade and the associated impact on performance. Since gas turbine are set to run at a specific gas mass flow, the differences between un-trenched and trenched for un-cooled and cooled are compared at the same given gas mass flow conditions.
The paper concludes with key considerations for cooled turbine stage efficiency effects with and without trench.
ECAT: An Engine Component Aerothermal Facility at the University of Oxford
Authors: Kirollos Benjamin , Lubbock Roderick , Beard Paul , Goenaga Frédéric , Rawlinson Anton , Janke Erik , Povey Thomas 
Published: August 2017

This paper describes a new engine-parts facility at the University of Oxford for high technology-readiness-level research, new technology demonstration, and for engine component validation.
The Engine Component AeroThermal (ECAT) facility has a modular working section which houses a full annulus of engine components. The facility is currently operated with high-pressure nozzle guide vanes from a large civil jet-engine. A high degree of engine similarity is achieved, with matched conditions of Mach number, Reynolds number, and coolant-to-mainstream pressure ratio. For combustor-turbine interaction studies, a combustor simulator module is used, which is capable of both rich-burn and lean-burn combined temperature, swirl and turbulence profiles.
The facility is being used for aerothermal optimisation research (e.g., novel cooling systems, aerodynamic optimisation problems, capacity sensitivity studies), computational fluid dynamics validation (aerodynamic predictions, conjugate predictions), and for component validation to accelerate the engine design process.
The three key measurement capabilities are: capacity characteristic evaluation to a precision of 0.02%; overall cooling (metal) effectiveness measurements (using a rainbow set of parts if required); and aerodynamic loss evaluation (with realistic cooling, trailing-edge flow etc.). Each of these three capabilities have been separately developed and optimised in other facilities at the University of Oxford in the last 10 years, to refine aspects of facility design, instrumentation design, experimental technique, and theoretical aspects of scaling and reduction of experimental data. The ECAT facility brings together these three research strands with a modular test vehicle for rapid high technology-readiness-level research, demonstration of new technologies, and for engine component validation.
The purpose of this paper is to collect in one place — and put in context — the work that led to the development of the ECAT facility, to describe the facility, and to illustrate the accuracy and utility of the techniques by presenting typical data for each of the key measurements.
The ECAT facility is a response to the changing requirements of experimental turbomachinery testing, and it is hoped this paper will be of interest to engine designers, researchers, and those involved in major facility developments in both research institutes and engine companies.
A One-Dimensional Gas Dynamics Code for Turbocharger Turbine Pulsating Flow Performance Modelling
Authors: Feneley Adam , Pesiridis Apostolos , Chen Hua 
Published: August 2017

As governments around the world ramp up their efforts to reduce CO2 emissions, downsizing internal combustion engines has become a dominant trend in the automotive industry. Air charging systems are being utilised to increase power density and therefore lower emissions by downsizing internal combustion engines. Turbocharging represents the majority of these air charging systems, which are commonly adopted for commercial and passenger vehicles. The process of matching turbomachinery to an engine during early-stage development is important to achieving maximum engine performance in terms of power output and the reduction of emissions.
Despite on-engine conditions providing highly unsteady gas flows, current turbocharger development commonly uses performance maps that are produced from steady state measurements. There are other significant sources of error to be found in early stage turbocharger performance prediction, such as the omission of heat transfer effects, and the use of data extrapolation methods to cover the entire operating range of a device from limited data sets. Realistic engine conditions provide a complex heat transfer scenario, which is dependent upon load history and the component layout of the engine bay. Heat transfer effects are particularly prevalent at low engine loads, whilst pulsating effects are significant at both high and low engine speeds (and therefore exhaust pulse frequency). Compressor maps are often provided by manufacturers with a level of heat transfer corresponding to a gas stand test, not realistic engine conditions. This causes a mismatch when using the aforementioned maps in commercial engine codes. This reduces the quality of overall engine performance predictions, since as the temperature of the exhaust gas on the turbine side rises, the performance prediction increasingly deviates from the usual adiabatic assumption used in simulations.
In the present work, a one-dimensional unsteady flow model has been developed to predict the performance of a vaneless turbine under pulsating inlet conditions, with scope to account for heat transfer effects. Flow within the volute is considered to be one-dimensional and unsteady, with mass addition and withdrawal used to simulate the gas flow between the volute and rotor. Rotor passages are also treated as one-dimensional and unsteady, with the equations being solved by the method of characteristics. This model is able to simulate the circumferential feeding of the rotor from the casing, unlike many previous zero and one-dimensional models. Building upon previous work, the basis of this code has been constructed in C++ with future integration with other modern gas dynamics codes in mind. By providing the appropriate instantaneous operating conditions at specified time intervals, a code such as this could theoretically negate the need for maps produced by steady-state data.