bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rapid Airfoil Design for Uncooled High Pressure Turbine Blades
Authors: Moradi Niloofar , Vlasic Edward , Moustapha Hany 
Published: August 2015

The aero-engine design process is highly iterative, multidisciplinary in nature and complex. The success of any engine design depends on best exploiting and considering the interactions among the numerous traditional engineering disciplines such as aerodynamics and structures. More emphasis has been placed lately on system integration, cross disciplines leveraging of tools and multi-disciplinary-optimization at the preliminary design phase. This paper investigates the automation of the airfoil generation process, referred to as Rapid Airfoil 3D (RAF 3D), for uncooled high pressure turbine blades at the preliminary design phase. This Matlab based program, uses the turbine aero meanline (TAML) in parallel with a database of previously designed P&WC airfoils, in-house design rules and best practices to define a pre-detailed airfoil shape which can be fed back to other analytical groups for pre-detail analyses, such as for structures and vibrations. Resulting airfoil shapes have been aerodynamically validated using an in-house 3D RANS code.
RAF 3D will shorten the turnaround time for P&WC’s turbine aerodynamics group to provide a preliminary 3D airfoil shape to turbine structures group by up to a factor of ten. Additionally, the preliminary assessments of stress and vibration specialists will be more accurate as their assessments will be based on an airfoil that has had inputs from all functional groups even though it is “first pass” design.
Assessment of Unsteady Pressure Measurement Uncertainty: Part 1 — Single Sensor Probe
Authors: Dell’Era Giulia , Mersinligil Mehmet , Brouckaert Jean-François 
Published: August 2015

With the advancements in miniaturization and temperature capabilities of piezo-resistive pressure sensors, pneumatic probes — which are the long established standard for flow-path pressure measurements in gas turbine environments — are being replaced with unsteady pressure probes. Any measured quantity is by definition inherently different from the ‘true’ value, requiring the estimation of the associated errors for determining the validity of the results and establishing respective confidence intervals. In the context of pressure measurements, the calibration uncertainty values, which differ from measurement uncertainties, are typically provided. Even then, the lack of a standard methodology is evident as uncertainties are often reported without appropriate confidence intervals. Moreover, no time-resolved measurement uncertainty analysis has come to the attention of the authors.
The objective of this paper is to present a standard method for the estimation of the uncertainties related to measurements performed using single sensor unsteady pressure probes, with the help of measurements obtained in a one and a half stage low pressure high speed axial compressor test rig as an example. The methodology presented is also valid for similar applications involving the use of steady or unsteady sensors and instruments.
The static calibration uncertainty, steady measurement uncertainties and unsteady measurement uncertainties based on phase-locked and ensemble averages are presented in this contribution. Depending on the number of points used for the averaging, different values for uncertainty have been observed, underlining the importance of having greater number of samples. For unsteady flows, higher uncertainties have been observed at regions of higher unsteadiness such as tip leakage vortices, hub corner vortices and blade wakes.
Unfortunately, the state of the art in single-sensor miniature unsteady pressure probes is comparable to multi-hole pneumatic probes in size, preventing the use of multi-hole unsteady probes in turbomachinery environments. However, the angular calibration properties of a single sensor probe obtained via an aerodynamic calibration may further be exploited as if a three-hole directional probe is employed, yielding corrected total pressure, unsteady yaw angle, static pressure and Mach number distributions based on the phase-locked averages with the expense of losing the time-correlation between the virtual ports. The aerodynamic calibration and derivation process are presented together with the assessment of the uncertainties associated to these derived quantities by the authors in [1]. In the virtual three-hole mode, similar to that of a single-sensor probe, higher uncertainty values are observed at regions of higher unsteadiness.
Investigation of the Dynamics of an Ultra Low NOx Injection System by POD Data Post-Processing
Authors: Berrino M. , Lengani D. , Satta F. , Ubaldi M. , Zunino P. , Colantuoni S. , Di Martino P. 
Published: August 2015

The present paper is focused on the investigation of the dynamics of the flow downstream of an Ultra Low NOx (ULN) injection system, designed to reduce NOx emissions and combustor axial length. Two rectangular flame tubes have been experimentally investigated: one aimed at simulating an unconfined exit flow, and another with the same transverse dimensions of the combustor annular sector, to simulate the confined flow field. The effects induced by the realistic flame tube presence are investigated comparing the flow field with that generated in the unconfined case. Particular attention is paid to the vortex breakdown phenomena associated with the flow generated by the two co-rotating swirlers constituting the injection system.
Two different and complementary measurement techniques have been adopted to characterize the aerodynamics of the vortex breakdown. The hot-wire investigation results reveal the frequencies associated with the precession motion due to the vortex breakdown. The Particle Image Velocimetry technique has been coupled with Proper Orthogonal Decomposition (POD) for data post-processing in order to reconstruct the swirling motion generated by the injection system. The property of POD, which consists of splitting temporal from spatial information of the flow field in analysis, allows the distinction between deterministic and random fluctuations without the need of an external trigger signal. This feature is fundamental for the better understanding of an highly-swirling flow.
Experimental Investigation of Circumferential Groove Casing Treatments for Large Tip Clearances in a Low Speed Axial Research Compressor
Authors: Rolfes Matthias , Lange Martin , Vogeler Konrad 
Published: August 2015

In high pressure compressors large tip clearances can occur in the rear stages especially during transient operation. This can lead to a reduced operating range and performance of the compressor. One simple means to reduce the negative effects of a rotor tip clearance increase can be circumferential groove casing treatments. Their ability to improve the operating range of a compressor is well-known for several decades.
In this paper, an experimental study to investigate the influence of three different circumferential groove casing treatments on a low speed axial research compressor with very large rotor tip clearances (5% of annulus height) is presented. Two single-groove and one double-groove casing treatments have been tested. The grooves are positioned from 31% to 69% axial chord. The compressor characteristics of the smooth wall and the three groove configurations are discussed as well as selected five-hole probe measurements of the flow field downstream the rotor. It can be shown that all grooves are able to improve the operating range of the compressor. Furthermore, an improvement of efficiency due to the casing grooves can also be observed in certain operating points.
An Evaluation of Vaneless Diffuser Modelling Methods as a Means of Improving the Off-Design Performance Prediction of Centrifugal Compressors
Authors: Stuart Charles , Spence Stephen , Filsinger Dietmar , Starke Andre , Kim Sung In , Harley Peter 
Published: August 2015

An evaluation of existing 1-D vaneless diffuser design tools in the context of improving the off-design performance prediction of automotive turbocharger centrifugal compressors is described. A combination of extensive gas stand test data and single passage CFD simulations have been employed in order to permit evaluation of the different methods, allowing conclusions about the relative benefits and deficiencies of each of the different approaches to be determined. The vaneless diffuser itself has been isolated from the incumbent limitations in the accuracy of 1-D impeller modelling tools through development of a method to fully specify impeller exit conditions (in terms of mean quantities) using only standard test stand data with additional interstage static pressure measurements at the entrance to the diffuser. This method allowed a direct comparison between the test data and 1-D methods through sharing common inputs, thus achieving the aim of diffuser isolation.
Crucial to the accuracy of determining the performance of each of the vaneless diffuser configurations was the ability to quantify the presence and extent of the spanwise aerodynamic blockage present at the diffuser inlet section. A method to evaluate this critical parameter using CFD data is described herein, along with a correlation for blockage related to a new diffuser inlet flow parameter ⚡, equal to the quotient of the local flow coefficient and impeller tip speed Mach number. The resulting correlation permitted the variation of blockage with operating condition to be captured.
Parametric and Comparative Assessment of Navier-Stokes CFD Methodologies for Darrieus Wind Turbine Performance Analysis
Authors: Balduzzi Francesco , Bianchini Alessandro , Gigante Fabio Antonio , Ferrara Giovanni , Campobasso Michele Sergio , Ferrari Lorenzo 
Published: August 2015

Navier-Stokes computational fluid dynamics simulations are expected to provide the basis for a deeper understanding of the real behavior of vertical-axis wind turbines. The prediction of the flow field past Darrieus rotors, a popular turbine of this type, requires a good resolution of both the unsteadiness caused by the periodic variation of the modulus and direction of the relative velocity perceived by the blades, and the interaction between the wakes shed by the blades in the upstream region of the rotor and the downstream blades traveling through such wakes.
This paper presents a comparative assessment of the predictive capabilities of two substantially different time-dependent Navier-Stokes Reynolds-averaged-based approaches to the analysis of Darrieus turbines. One is based on a commercial code, and the other on an academic research code. A Darrieus rotor configuration previously analyzed by other researchers was selected for this study, which focused on the turbine flow at a tip-speed ratio of 3.3. Aggregate power coefficient comparisons at other regimes are also provided. Solution sensitivity analyses to spatial and temporal grid refinement, domain size and boundary condition modeling aspects for each of the two approaches are provided in the study. A very good agreement is obtained between the two simulation sets, and a fairly good agreement is found between both simulations and available measured data.
Quantitative CFD Analyses of Particle Deposition on a Subsonic Axial Compressor Blade
Authors: Suman Alessio , Kurz Rainer , Aldi Nicola , Morini Mirko , Brun Klaus , Pinelli Michele , Spina Pier Ruggero 
Published: August 2015

In literature there are some studies related to the fouling phenomena in transonic compressors, but, in industrial applications (heavy-duty compressor, pump stations, etc.) the subsonic compressors are widespread. It is of great interest to the manufacturer to discover the fouling phenomenon related to this type of compressor.
This paper presents three-dimensional numerical simulations of the micro-particle ingestion on a subsonic axial compressor rotor carried out by means of a commercial computational fluid dynamic code. Particle trajectory simulations use a stochastic Lagrangian tracking method that solves the equations of motion separate from the continuous phase.
The number of particles, sizes, and concentrations are specified in order to perform a quantitative analysis of the particle impact on the blade surface.
In this paper the particle impact pattern and the kinematic characteristics (velocity and angle) of the impact are shown. Both of the blade zones affected by particle impact and the blade zones affected by particle deposition are analyzed. The particle deposition is established by using the quantity called sticking probability. The sticking probability links the kinematic characteristics of particle impact on the blade with fouling phenomenon.
The results show that micro-particles tend to follow the flow by impacting at full span with a higher impact concentration on the leading edge. The suction side is affected only close to the leading edge and, at the hub, close to the trailing edge. Particular fluid-dynamic phenomena such as separation, stagnation and tip leakage vortex strongly influence the impact location of the particles. The kinematic analysis showed a high tendency of particle adhesion on the suction side, especially for smaller particles for which the fluid dynamic phenomena play a key role regarding particle impact velocity and angle.
Estimation of the Particle Deposition on a Transonic Axial Compressor Blade
Authors: Suman Alessio , Morini Mirko , Kurz Rainer , Aldi Nicola , Brun Klaus , Pinelli Michele , Spina Pier Ruggero 
Published: August 2015

Solid particle ingestion is one of the principal degradation mechanisms in the compressor section of heavy-duty gas turbines. Usually, foulants in the ppm range, not captured by the air filtration system (0–2) μm cause deposits on blading and result in a severe performance drop of the compressor. It is of great interest to the industry to determine which areas of the compressor airfoils are interested by these contaminants as a function of the location of the power unit.
The aim of this work is the estimation of the actual deposits on the blade surface in terms of location and quantity. The size of the particles, their concentrations and the filtration efficiency are specified in order to perform a realistic quantitative analysis of the fouling phenomena in an axial compressor. This study combines, for the first time, the impact/adhesion characteristic of the particles obtained through a CFD and the real size distribution of the contaminants in the air swallowed by the compressor.
The blade zones affected by deposits are clearly reported by using easy-to-use contaminant maps realized on the blade surface in terms of contaminant mass.
The analysis showed that particular fluid-dynamic phenomena such as separation, shock waves and tip leakage vortex strongly influence the pattern deposition. The combination of the smaller particles (0.15 μm) and the larger ones (1.50 μm) determines the highest amounts of deposits on the leading edge of the compressor airfoil.
From these analyses, some guidelines for proper installation and management of the power plant (in terms of filtration systems and washing strategies) can be drawn.
Impact of Turbine Blade Internal Cooling on Aerodynamic Loss
Authors: Vassiliev Vladimir , Granovskiy Andrey , Lomakin Nikolai 
Published: August 2015

Modern gas turbines operate at high temperature, which exceed the endurance limit of material, and therefore the turbines components have to be cooled by the air taken from the compressor. The cooling providing positive impact on lifetime of GT has negative impact on its performance. Firstly because the cooling air bypasses combustor and its capacity is not fully utilized. This effect is usually accounted in thermodynamic calculations of gas turbine. Secondly the injection of cooling air in the turbine disturbs the main flow, and may lead to increased losses. In addition cooling requirements lead to limitation on the blade shape (e.g. limiting the minimal size of trailing edge) and thereby negatively affect the losses. These effects were already discussed in the literature, but further investigations for better understanding of flow physics and design improvement are still useful.
There is also additional impact of cooling - impact of heat transfer on near wall boundary layer and coolant properties. This effect was not sufficiently discussed in the open literature, where quite often the walls are considered as adiabatic.
The paper consists of two main parts. In the first part the results of experimental investigations of several linear cascades with and without trailing edge injection are presented and discussed.
In the second part the results of detailed numerical investigations of one of these cascades are presented. One set of calculations were done at the test rig conditions for comparison with measured data. These calculations were used for validation of CFD model. The next sets of calculations were done for engine typical conditions, including the simulation of blade material temperature. The calculations were performed for adiabatic wall and for surface with heat transfer, including the impact of heat transfer on coolant injection. This analysis provides split of losses caused by different factors, and offers the opportunities for efficiency and lifetime improvements of real engine designs/upgrades.
Analysis of Measured Flame Transfer Functions With Locally Resolved Density Fluctuation and OH-Chemiluminescence Data
Authors: Peterleithner Johannes , Stadlmair Nicolai V. , Woisetschläger Jakob , Sattelmayer Thomas 
Published: August 2015

The goal of the study presented in this paper is to analyze flame transfer functions with a new approach based on the combination of-line-of sight OH*-chemiluminescence and density fluctuation data. The OH*-chemiluminescence is acquired with a photomultiplier and an intensified camera, the density fluctuations are measured with a Laser vibrometer on a two axis traverse. In flames with forcing the acoustic fluctuations can be extracted from the data by discrimination of all contributions from combustion noise, because it is not correlated with the excitation device. Assuming rotational symmetry of the fluctuations originating from excitation, planar phase-resolved and pseudo-local OH*-chemiluminescence and density fluctuation data is obtained from the measured line-of-sight integrated signals.
In the study this technique is applied to a swirl burner configuration with FTFs from known multi-microphone measurements (MMM). In the first step, the externally premixed mode without equivalence ratio fluctuations is studied and in the second step the fuel is injected in the swirler in order to generate equivalence ratio waves. At selected frequencies the planar fields of the OH*-chemiluminescence and density fluctuations are compared to the FTFs in order to improve the understanding regarding the specific amplitude and phase values. In addition to heat release the vibrometer data reveals the periodic oscillation of the conical annular jet of the cold reactants in the combustor filled with hot products. On the global scale the amplitudes and phases of heat release expected from the MMM are satisfactorily reproduced by both methods for the premixed cases, whereas OH*-chemiluminescence data cannot be used as indicator for heat release if equivalence ratio fluctuations are present, because the amplitude of the FTF is significantly over-predicted due to the sensitivity of OH* on the local fuel-air mixture.
Investigation of Annular Jet Flows in a Subsonic Air-Air Ejector With Multi-Ring Entraining Diffuser
Authors: Namet-Allah A. , Birk A. M. 
Published: August 2015

The current paper presents a cold flow simulation study of a low Mach number air-air ejector with a four ring entraining diffuser that is used in a variety of applications including infrared (IR) suppression of exhaust from helicopters and fixed wing aircraft. The main objectives of this investigation were to identify key issues that must be addressed in successful CFD modelling of such devices, and recognize opportunities to improve the performance of these devices. Two-dimensional CFD simulations were carried out using commercial software, Ansys14. Studies of mesh and domain size sensitivity were made to ensure the CFD results were independent of both factors. A turbulence model independence study using k-ε, k-ω and RSM turbulence models was performed to figure out the appropriate turbulence model that produced the best agreement with the experimental data for several of ejector performance criteria. The measured flow properties in the annulus were used as input boundary conditions for the CFD simulations. However, in the comprehensive turbulence model study, the measured flow parameters at the nozzle exit were also applied as inlet boundary conditions for the CFD simulations. The measured flow velocity at the nozzle exit, at one centerline section inside the mixing tube and at the diffuser exit and the system pressure recovery were compared with the CFD predictions. The ejector pumping ratios, back pressure coefficient and diffuser gap velocities were also compared.
It was found that the RANS-based CFD predictions were sensitive to the changes in the ejector domain size, mesh refinement and inlet boundary condition locations. With the annulus inlet boundary conditions, the tested turbulence models under predicted the size of the core separation downstream of the system, back pressure, pumping ratio and pressure recovery in the mixing tube and diffuser. However, the ability of the RNG turbulence model to predict the ejector performance parameters was better than that of the other turbulence models at all inlet flow conditions. Nevertheless, applying the inlet boundary conditions at the nozzle exit enhanced the capability of the RANS-based turbulence model particularly in predicting the ejector pumping ratios, pressure recovery and the size of the core separation. Finally, the acceptable agreement between the experimental data and the CFD predictions provides a valid tool to continue improving these devices using CFD techniques.