bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nekomimi Film Cooling Holes Configuration Under Conjugate Heat Transfer Conditions
Authors: Kusterer Karsten , Tekin Nurettin , Wüllner Tobias , Bohn Dieter , Sugimoto Takao , Tanaka Ryozo , Kazari Masahide 
Published: September 2014

In modern gas turbines, the film cooling technology is essential for the protection of the hot parts, in particular of the first stage vanes and blades of the turbine, against the hot gases from the combustion process in order to reach an acceptable life span of the components. As the cooling air is usually extracted from the compressor, the reduction of the cooling effort would directly result in increased thermal efficiency of the gas turbine. Understanding of the fundamental physics of film cooling is necessary for the improvement of the state-of-the-art. Thus, huge research efforts by industry as well as research organizations have been undertaken to establish high efficient film cooling technologies. Today it is common knowledge that film cooling effectiveness degradation is caused by secondary flows inside the cooling jets, i.e. the Counter-Rotating Vortices (CRV) or sometimes also called kidney-vortices, which induce a lift-off of the jet. Further understanding of the secondary flow development inside the jet and how this could be influenced, has led to hole configurations, which can induce Anti-Counter-Rotating Vortices (ACRV) in the cooling jets. As a result, the cooling air remains close to the wall and is additionally distributed flatly along the surface. Beside different other technologies, the NEKOMIMI cooling technology is a promising approach to establish the desired ACRVs. It consists of a combination of two holes in just one configuration so that the air is distributed mainly on two cooling air streaks following the special shape of the generated geometry.
The NEKOMIMI configuration and two conventional cooling hole configurations (cylindrical and shaped holes) has been investigated numerically under adiabatic and conjugate heat transfer conditions. The influence of the conjugate heat transfer on the secondary flow structure has been analysed.
In conjugate heat transfer calculations, it cannot directly derived from the surface temperature distribution if the reached cooling effectiveness values are due to the improved hole configuration with improved secondary flow structure or due to the heat conduction in the material. Therefore, a methodology has been developed, to distinguish between cooling effectiveness due to heat conduction in the material and film cooling flow over the surface. The numerical results shows that for the NEKOMIMI configuration, 77% of the reached overall cooling effectiveness is due to film cooling with improved flow structure in the secondary flow (ACRV) and 23% due to heat conduction in the material. For the cylindrical hole configuration, 10% of the reached overall cooling effectiveness is due to the film cooling flow structure and 90% due to heat conduction in the material.
Meanline Modelling of Inlet Recirculation in Automotive Turbocharger Centrifugal Compressors
Authors: Harley Peter , Spence Stephen , Filsinger Dietmar , Dietrich Michael , Early Juliana 
Published: September 2014

This study provides a novel meanline modelling approach for centrifugal compressors. All compressors analysed are of the automotive turbocharger variety and have typical upstream geometry with no casing treatments or pre-swirl vanes. Past experience dictates that inducer recirculation is prevalent toward surge in designs with high inlet shroud to outlet radius ratios; such designs are found in turbocharger compressors due to the demand for operating range. The aim of the paper is to provide further understanding of impeller inducer flow paths when operating with significant inducer recirculation. Using 3D Computational Fluid Dynamics (CFD) and a single-passage model, the flow coefficient at which the recirculating flow begins to develop and the rate at which it grows are used to assess and correlate work and angular momentum delivered to the incoming flow. All numerical modelling has been fully validated using measurements taken from hot gas stand tests for all compressor stages.
The new modelling approach links the inlet recirculating flow and the pressure ratio characteristic of the compressor. Typically for a fixed rotational speed, between choke and the onset of impeller inlet recirculation the pressure ratio rises gradually at a rate dominated by the aerodynamic losses. However, in modern automotive turbocharger compressors where operating range is paramount, the pressure ratio no longer changes significantly between the onset of recirculation and surge. Instead the pressure ratio remains relatively constant for reducing mass flow rates until surge occurs.
Existing meanline modelling techniques predict that the pressure ratio continues to gradually rise toward surge, which when compared to test data is not accurate. A new meanline method is presented here which tackles this issue by modelling the direct effects of the recirculation. The result is a meanline model that better represents the actual fluid flow seen in the CFD results and more accurately predicts the pressure ratio and efficiency characteristics in the region of the compressor map affected by inlet recirculation.
Investigation of Variated Unsteady Inflow Boundary Conditions on the Transition Behavior of a Low Pressure Turbine Cascade Family
Authors: Blaim Franz F. , Brachmanski Roland E. , Niehuis Reinhard 
Published: September 2014

The objective of this paper is to analyze the influence of incoming periodic wakes, considering the variable width, on the integral total pressure loss for two low pressure turbine (LPT) airfoils.
In order to reduce the overall weight of a LPT, the pitch to chord ratio was continuously increased, during the past decades. However, this increase encourages the development of the transition phenomena or even flow separation on the suction side of the blade. At low Reynolds numbers, large separation bubbles can occur there, which are linked with high total pressure losses.
The incoming wakes of the upstream blades are known to trigger early transition, leading to a reduced risk of flow separation and hence minor integral total pressure losses caused by separation. For the further investigation of these effects, different widths of the incoming wakes will be examined in detail, here. This variation is carried out by using the numerical Unsteady Reynolds Averaged Solver TRACE developed by the DLR Cologne in collaboration with MTU Aero Engines AG. For the variation of the width of the wakes, a variable boundary condition was modeled, which includes the wake vorticity parameters. The width of the incoming wakes was used as the relevant variable parameter. The implemented boundary condition models the unsteady behavior of the incoming wakes by the variation of the velocity profile, using a prescribed frequenc. TRACE can use two different transition models; the main focus here is set to the γ–Reθt transition model, which uses local variables in a transport equation, to trigger the transition within the turbulence transport equation system.
The experimental results were conducted at the high speed cascade open loop test facility at the Institute for Jet Propulsion at the University of the German Federal Armed Forces in Munich.
For the investigation presented here, two LPT profiles — which were designed with a similar inlet angle, turning, and pitch are analyzed. However, with a common exit Mach number and a similar Reynolds number range between 40k and 400k, one profile is front loaded and the other one is aft loaded.
Numerical unsteady results are in good agreement with the conducted measurements. The influence of the width of the wake on the time resolved transition behavior, represented by friction coefficient plots and momentum loss thickness will be analyzed in this paper.
Gas Temperature Field Measurement Using Thin-Filament Pyrometry
Authors: Wang Guanghua , Bonilla Carlos , Kalitan Danielle 
Published: September 2014

Thin Filament Pyrometry (TFP) has been proven to be a useful approach to measure hot gas temperature. The TFP technique involves suspending a thin filament (typically a SiC fiber) in hot gas flow path and calculating the gas temperature from the measured thermal radiance of the filament. Comparing to most optical and laser based non-intrusive techniques, the TFP approach offers significant simplicity, reduced cost and relative ease of applicability, especially at high-pressure gas-turbine type conditions.
In this study, TFP was employed to measure combustor exit gas temperature distributions in an atmospheric combustion rig simulating a model aero-engine combustor burning Jet-A fuel. Hot gas from the combustor was accelerated through a converging nozzle to achieve high exit velocities. The thermal radiation signal from the glowing fiber was collected by a Near Infrared (NIR) camera outfitted with a band pass filter. The gas temperature profile was calculated by an intensity ratio technique. Two-Dimensional temperature maps were obtained via spatially and temporally scanning the TFP system. Temperature measurements at the combustor exit are reported for various fuel-air ratios at Mach numbers around 0.38. A type-B thermocouple stationed at the centerline of the combustor exit was corrected for radiation effects and used to infer the flame temperature for TFP measurement.
The major contributions of the current study to the advancement of the TFP technique for measuring hot gas temperatures are: (1) To the authors’ knowledge, this is the first time that the TFP technique has been used in a liquid fueled combustion system, and (2) The data presented herein were obtained at greater Mach numbers than all previous studies (Ma = 0.38).
Conjugate Heat Transfer Analysis for Gas Turbine Cooled Blade
Authors: Ho Kuo-San , Urwiller Christopher , Konan S. Murthy , Liu Jong S. , Aguilar Bruno 
Published: September 2014

This paper explores the conjugate heat transfer (CHT) numerical simulation approach to calculate the metal temperature for a cooled gas turbine blade. ANSYS CFX14.0 code was selected as the computational fluid dynamic (CFD) tool to perform the CHT simulation. The two-equation SST turbulence model with automatic wall treatment was employed. A full engine test with Silicon Carbide (SiC) chip measurements was performed and used to validate the CHT results.
Metal temperatures calculated with the CHT model were compared to engine test data. The results demonstrated good agreement between predicted and measured airfoil metal temperatures. The blade cooling flow prediction was matched to the flow network analysis.
This paper describes a process to calculate convection heat transfer coefficients (HTC) for cooling passages and airfoil surfaces using CHT results. This process was made possible because local wall heat flux and fluid temperatures were known. This approach assisted in calibrating an in-house conduction thermal model for steady state thermal analyses.
Generalized Optimization of Counter-Rotating and Single-Rotating Fans
Authors: Lengyel-Kampmann Timea , Voß Christian , Nicke Eberhard , Rüd Klaus-Peter , Schaber Reinhold 
Published: September 2014

On possible fan concept for future high and ultra-high bypass ratio turbofan engines is the counter-rotating (CR) fan. Several studies [1][2][3][4] dealt already with the optimization of CR fans, however the mass flow and the total pressure ratio were typically given and fixed for a specified application. The results of these studies showed a benefit of the CR fan compared to the conventional single-rotating (SR) fan, which strongly depended on the engine cycle. Following this experience, it was necessary to further specify the efficiency benefits more precisely in association with fan total pressure ratio and fan inlet axial Mach number. The results are discussed in this present paper. A special emphasis was given on determining the optimal pressure ratio, for which the CR-fan expectably achieves the maximal efficiency benefit.
The idea was to perform a global optimization study without any constraints for the operating point inside of a broad (ΠFan, Max) –range, for the rotational speeds and with only a few constraints for the geometry of the blades to avoid infeasible geometries. An adequate range for the fan pressure ratio (ΠFan) and for the axial Mach number (Max) was chosen for the global optimization covering the entire range from current to potential future ultra-high bypass ratio engine applications, also taking into account a reduced nacelle diameter and thus high axial fan inflow Mach numbers.
The focus of the present study was to develop a method for the global optimization of a fan stage.
As a result of this study, the maximal achievable efficiency is shown as a function of the fan pressure ratio and the axial Mach number. Thus the efficiency differences between the CR and SR fan can be calculated through the differences between the surfaces for any given set of parameters defining a potential engine. This allows for a generalized assessment of this particular fan concept over the entire range of relevant applications.
Dynamic Behavior of a Mistuned Air Turbine: Comparison Between Simulations and Measurements
Authors: Pohle Linus , Panning-von Scheidt Lars , Wallaschek Joerg , Aschenbruck Jens , Seume Joerg R. 
Published: September 2014

Due to manufacturing tolerances, wear during operation or regeneration processes like maintenance operation, the structural properties of turbine blades deviate from design condition to reference blades. This deviation usually causes higher vibration amplitudes and as a consequence a lower service life expectation. Many different calculation methods can be used to simulate these increased amplitudes of mistuned blades. The major resulting problem is on the one hand to capture the occurring deviation of the eigenfrequencies from the reference blade and on the other hand to incorporate these real deviations in simulations. Solving these problems with a simplified experimental setup will make it possible to predict the maximum amplitude and to avoid costly experiments in a rotating turbine.
The aim of the paper is to verify a simulation of the vibration amplitude by experiments using a reduction method to calculate a mistuned system in reasonable time. The results of the chosen simulation are compared to experiments in a rotating turbine.
To reduce the number of degrees of freedom of the full finite-element model and the computational effort, a multi-step reduction method is used. In the simulation, the centrifugal force, the structural damping, the steady static pressure on the blades, and the mistuning are considered. To find the occurring deviations of each manufactured blade, an experimental modal analysis is performed for every single blade in a non-rotating setup with the eigenfrequencies of every single blade as an output. The single-stage results of the simulation are subsequently compared to experiments in a 5-stage air turbine in which the vibration amplitudes and the eigenfrequencies of every blade in the last rotor blade row are measured by a tip-timing system.
Methods and Results in Remote Monitoring and Diagnosing a Fleet of Industrial Gas Turbines
Authors: Scheianu Dorin 
Published: September 2014

The paper describes a set of analysis tools and the results obtained from applying them to remote monitoring a fleet of industrial gas turbines serviced under contract. It includes the following:
- The initial post overhaul acceptance test (performed in a specialized controlled environment facility) and the subsequent commissioning test (performed in the field at the end user)
- The object of monitoring service — data collection, transmission, organization, storage and access
- Data analysis and conversion into useful information
- Monitoring and analysis tools with results available and accessible in real time: statistics, trends, cloud points, estimators of engine health
- Development of malfunction indicators and their use
The purpose of such analysis is the development and implementation of proper quantitative tools and methods for correctly assessing when malfunctions of gas turbines develop and eventually to identify their causes, in order to help the operating personnel select the appropriate maintenance measures in a timely manner. The examples included are collected from actual applications, with engineering interpretation and resolution.
Numerical 3D Simulation of the Cavitating Flow in a Centrifugal Pump With Low Specific Speed and Evaluation of the Suction Head
Authors: Limbach Phillip , Kimoto Marius , Deimel Christian , Skoda Romuald 
Published: September 2014

A numerical analysis is performed to assess the capability of common simulation methods, in particular Ansys CFX, to predict the performance and NPSH curve of a centrifugal pump at very low specific speed for both, design and off-design conditions.
In all cases, we use an entire numerical model containing the impeller, the volute casing, the side chambers as well as suction pipe and pressure pipe. A three-dimensional setup is used, testing the following numerical models: steady, i.e. frozen rotor model, unsteady model accounting for the impeller movement and the relative impeller-volute position, single-phase flow as well as cavitating flow conditions.
The global performance of the pump is assessed in terms of pressure head, power consumption and pump efficiency for single-phase flow. Furthermore, the drop of the pump head and Net Positive Suction Head (NPSH) characteristics are analyzed for cavitating flow conditions. Numerical results are validated against experimental data.
Regarding non-cavitating flow conditions, the trend of the characteristic curves is well predicted, while absolute performance values differ from measured data significantly. The results of steady and unsteady calculations deviate from each other by less than 2%. Concerning cavitating flow, unsteady simulations have to be performed in particular for overload conditions, in order to obtain convergence of the solver. The trend of the measured NPSH curve is well captured with default cavitation model parameters. For nominal and overload, the predicted NPSH curve underestimates the measured one significantly.
Effect of the Stator Hub Configuration and Stage Design Parameters on Aerodynamic Loss in Axial Compressors
Authors: Yoon Sungho , Selmeier Rudolf , Cargill Patricia , Wood Peter 
Published: September 2014

The choice of the stator hub configuration (i.e. cantilevered versus shrouded) is an important design decision in the preliminary design stage of an axial compressor. Therefore, it is important to understand the effect of the stator hub configuration on the aerodynamic performance. In particular, the stator hub configuration fundamentally affects the leakage flow across the stator. The effect of the stator hub configuration on the leakage flow and its consequent aerodynamic mixing loss with the main flow within the stator row is systematically investigated in this study.
In the first part of the paper, a simple model is formulated to estimate the leakage loss across the stator hub as a function of fundamental stage design parameters, such as the flow coefficient, the degree of reaction and the work coefficient, in combination with some relevant geometric parameters including the clearance/span, the pitch-to-chord ratio and the number of seals for the shrouded geometry. The model is exercised in order to understand the effect of each of these design parameters on the leakage loss.
It is found that, for a given flow coefficient and work coefficient, the leakage loss across the stator is substantially influenced by the degree of reaction. When a cantilevered stator is compared with a shrouded stator with a single seal at the same clearance, it is shown that a shrouded configuration is generally favored as a higher degree of reaction is selected, whereas a cantilevered configuration is desirable for a lower degree of reaction. Further to this, it is demonstrated that, for shrouded stators, an additional aerodynamic benefit can be achieved by using multiple seals.
The second part of the paper investigates the effect of the rotating surfaces. Traditionally, only the pressure loss has been considered for stators. However, the current advanced CFD generally includes the leakage path with associated rotating surfaces, which impart energy to the flow. It is shown that the conventional loss coefficient, based on considering only the pressure loss, is misleading when hub leakage flows are modeled in detail, because there is energy addition due to the rotation of the hub or the shroud seals for the cantilevered stator and the shrouded stator, respectively. The calculation of the entropy generation across the stator is a better measure of relative performance when comparing two different stator hub configurations with detailed CFD.
Two Phase Computational Study of Flow Behaviour in a Region Within an Aeroengine Gearbox
Authors: Turner A. , Morvan H. P. , Simmons K. 
Published: September 2014

Within large civil aeroengines a significant contributor to parasitic power loss (manifest as increased heat-to-oil) is the internal gearbox (IGB). An IGB typically contains high speed shafts, a spiral bevel gear pair, bearings and seals as well as the complex geometry of the stationary components. The University of Nottingham Technology Centre in Gas Turbine Transmission Systems (UTC) has conducted experimental and computational projects to enhance understanding of two phase flow behaviour. Validated single phase modelling capability for an unmeshed shrouded crown gear has been established [1–3] and discrete phase modelling [3] has been applied to investigate the oil path under the shroud. Experimental work on shroud configurations [5] and two-phase flow [6] has also been conducted at the UTC using a rig with representative but simplified geometry relative to an aeroengine.
Recent modelling activity has focussed on the region behind the gear. In an aeroengine this region includes a large shaft location bearing that sheds oil into the rear chamber. This oil, combined with the high speed and complex airflows generated by proximity to the gear, makes this region particularly challenging to model. In the experimental test rig at the UTC this zone does not contain a bearing and so as yet no validation data exists.
In this paper an axisymmetric sector model of the rig back chamber is presented. Two phase flow behaviour was modelled using the Volume of Fluid (VOF) and Eulerian models within the CFD software ANSYS-Fluent. A comparison between these two multiphase models is made and their suitability to model the oil behaviour in the back chamber is discussed. Oil flow behaviour in this region is also reported.
The CFD results show that the VOF model is insufficient for predicting oil flows in this environment. Although there is a significant amount of liquid present as wall film, the liquid not on the walls appears important and is not adequately modelled by VOF, which is well-known as being most suitable where there is a definite interface between liquid and gaseous phases. The Eulerian model shows significantly more likely flow behaviour with results indicating a non-uniform distribution of oil across the axial length of the rear chamber with a bias towards the rear (bearing side). The air jet entering in the rear chamber from between the gear and shroud strongly influences flow behaviour in the rear chamber. The computed flow field is such that a full 360° model is recommended for future work of this nature.