bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study on the Impact of Fouling on Axial Compressor Stage
Authors: Chen Shaowen , Zhang Chen , Shi Hui , Wang Songtao , Wang Zhongqi 
Published: July 2013

Mechanistic research on the fouling of the compressor is necessary to delay the deterioration caused by fouling during long-term operation, and to explore methods that will lower compressor component deterioration, thereby improving the overall performance.
The effects of fouling on the performance of an axial compressor stage were investigated numerically. As a representative of the realistic compressor stages, the NASA Stage 35 was considered to perform a numerical investigation by means of a commercial computational fluid dynamic code. The numerical model was validated by comparing with the experimental data available from literatures. The computed performance maps and exit parameter distributions showed a good agreement with experimental data. The model was then used to simulate the effect of fouling on compressor stage by various fouling configurations including added thickness and surface roughness levels. The mechanism of the compressor deterioration due to fouling was discussed in detail. As a result, despite the contribution of added thickness on the work capacity, it substantially narrowed the table operating ranges substantially, causing a greater effect on the overall compressor performance. The influence of roughness applied in the rotor is similar to that in the whole stage, including the drop in mass flow rate at choked and near stall point, pressure ratio, and efficiency, whereas, compressor performance slightly decreases in the stator. When the surface roughness is equal to 50 μm, the drop in mass flow rate under a low Reynolds number is less than that under normal conditions, with little influence on the stable operating range.
Performance Uncertainty Quantification for Centrifugal Compressors: Part 2—Flange to Flange Variability
Authors: Sankaran Sivasubramaniyan , Sassanelli Giuseppe , Iurisci Giuseppe , Panizza Andrea 
Published: July 2013

This paper presents a methodology to control flange to flange performance prediction of centrifugal compressors using a probabilistic approach. In order to have reliable prediction for the performance of centrifugal compressors, a thorough knowledge of critical parameters contributing to the deviation and an efficient way to control the variation of these parameters becomes necessary. This paper discusses about a robust methodology for identifying and controlling the variation of these parameters and hence the predicted performance. This probabilistic technique involves a Design of Experiments (DoE) study to handle large number of input parameters, sensitivity study to identify critical ones and a Monte-Carlo based approach to identify the uncertainty in flange to flange performance. This approach takes into consideration the compressor stage performance variability driven by impeller manufacturing tolerances, statoric component losses variability and leakages variability in order to compute overall performance variation in a compressor. An in-house developed probabilistic optimization code (PEZ) is interfaced with a well-validated & calibrated thermodynamic tool to analyse large sets of possible combinations and to provide best possible solution for a given design space. This concept is successfully applied for different compressor configurations by varying the stage numbers and process conditions. The results give an insight on the main sources and magnitude of variations on compressor performance, thus enabling to control the predictions in an efficient way.
This methodology will provide a novel and an efficient way to generate robust compressor performance, where it will be possible to take into account design and manufacturing uncertainty. The use of this methodology can thus drastically improve the performance predictability and risk associated with each compressor selection.
Effects of Blade Damage on the Performance of a Transonic Axial Compressor Rotor
Authors: Li Yanling , Sayma Abdulnaser 
Published: July 2013

Gas turbine axial compressor blades may encounter damage during service for various reasons. Debris from casing or foreign objects may impact blades causing damage near the rotor’s tip. This may result in deterioration of performance and reduction in the surge margin. Ability to assess the effect of damaged blades on the compressor performance and stability is important at both the design stage and in service. The damage to compressor blades breaks the cyclic symmetry of the compressor assembly. Thus computations have to be performed using the whole annulus. Moreover, if rotating stall or surge occurs, the downstream boundary conditions are not known and simulations become difficult.
This paper presents an unsteady CFD analysis of compressor performance with tip curl damage. Tip curl damage typically occurs when rotor blades hit a loose casing liner. The computations were performed up to the stall boundary, predicting rotating stall patterns. The aim is to assess the effect of blade damage on stall margin and provide better understanding of the flow behaviour during rotating stall. Computations for the undamaged rotor are also performed for comparison. A transonic axial compressor rotor is used for the time-accurate numerical unsteady flow simulations, with a variable choked nozzle downstream simulating an experimental throttle. One damaged blade was introduced in the rotor assembly and computations were performed at 60% of the design rotational speed. It was found that there is no significant effect on the compressor stall margin due to one damaged blade despite the differences in rotating stall patterns between the undamaged and damaged assemblies.
Endwall Profiling With Tip Clearance Flows
Authors: Hilfer Michael , Ingram Grant , Hogg Simon 
Published: July 2013

This paper describes the design of a non-axisymmetric profiled endwall with tip clearance flow. Previous designs have assumed that the interaction between the tip clearance flow and the endwall has been negligible and this paper allows this assumption to be tested.
A profiled endwall was designed, built and tested in a low speed linear cascade. The design was conducted using the Durham endwall design system and this paper provides details of the first experimental validation of this system. Overall the design system was found to perform successfully.
Many other researchers have conducted endwall design, test and build exercises and the key advance here was to examine the effect of profiled endwalls on tip clearance flow. To this end a tip clearance was added to both the CFD and the cascade during the design process. The results show that even with an aspect ratio of two the endwall produces noticeable changes on the tip clearance flow. This does not however necessarily prevent a successful profiled endwall from being implemented in the cascade.
Reynolds Number Effects in a Low Pressure Turbine
Authors: Hura Harjit S. , Joseph John , Halstead Dave E. 
Published: July 2013

This paper reports the results of an experimental and analytical study of Reynolds number (Re) effect on Low Pressure Turbine (LPT) performance. LPTs suffer both a loss in efficiency and flow capacity at altitude due to thicker boundary layers and higher viscous losses. Boundary layer separation can occur in highly loaded and/or high lift designs. The magnitude of the effect is stronger for smaller engines being designed for regional jets which may have cruising altitudes above 50K feet. There is a general lack of knowledge about performance degradation in commercial LPTs under these conditions.
A test program was undertaken in a low pressure 3 stage axial turbine to quantify the effect of low Re on efficiency and flow lapse rate. Rig inlet pressures were varied from 0.27E+5 N/m2 (4 psia) to 4.40E+5 N/m2 (65 psia) to achieve over a 15 fold variation in Re. The chord based average Re varied from 30000 to 500000. Efficiency and flow function lapse of over 5% was measured. The fall off was non-linear with a rapid loss occurring at Re below 100000.
3D CFD analysis was conducted in parallel to predict overall performance but also understand loss details within the blade rows. Measured inlet profiles of total pressure, temperature and air angle, and exit static pressure were used as boundary conditions. Leakages and purge flows were modeled as source terms. A turbulence transition model and wall integration grids was used. The CFD results corroborate the test findings on the overall efficiency and flow capacity lapse rate. Analysis of blade row performance at high and low Re shows a sharp increase in profile loss at low Re.
Effects of Boundary Layer Ingestion on the Aero-Acoustics of Transonic Fan Rotors
Authors: Defoe J. J. , Spakovszky Z. S. 
Published: July 2013

The use of boundary-layer-ingesting, embedded propulsion systems can result in inlet flow distortions where the interaction of the boundary layer vorticity and the inlet lip causes horseshoe vortex formation and the ingestion of streamwise vortices into the inlet. A previously-developed body-force-based fan modeling approach was used to assess the change in fan rotor shock noise generation and propagation in a boundary-layer-ingesting, serpentine inlet. This approach is employed here in a parametric study to assess the effects of inlet geometry parameters (offset-to-diameter ratio and downstream-to-upstream area ratio) on flow distortion and rotor shock noise.
Mechanisms related to the vortical inlet structures were found to govern changes in the rotor shock noise generation and propagation. The vortex whose circulation is in the opposite direction to the fan rotation (counter-swirling vortex) increases incidence angles on the fan blades near the tip, enhancing noise generation. The vortex with circulation in the direction of fan rotation (co-swirling vortex) creates a region of subsonic relative flow near the blade tip radius which decreases the sound power propagated to the far-field.
The parametric study revealed that the overall sound power level at the fan leading edge is set by the ingested streamwise circulation, and that for inlet designs in which the streamwise vortices are displaced away from the duct wall, the sound power at the upstream inlet plane increased by as much as 9 dB. By comparing the far-field noise results obtained to those for a conventional inlet, it is deduced that the changes in rotor shock noise are predominantly due to the ingestion of streamwise vorticity.
The Effect of Airfoil Thickness on the Efficiency of LP Turbines
Authors: Torre Diego , Vázquez Raúl , Armanañzas Leyre , Partida Fernando , García-Valdecasas Guillermo 
Published: July 2013

The effect of airfoil thickness on the efficiency of Low Pressure (LP) Turbines has been investigated experimentally in a multistage turbine high-speed rig. The rig consists of three stages of a state of the art LP turbine. The stages are characterized by a very high hade angle, reverse cut-off design, very high lift and very high aspect ratio airfoils.
Two different sets of stators have been designed and tested. The first set of stators is made of airfoils with a thickness to chord ratio around 10% along the span with exception of a small areas close to the endwalls. In those areas, the thickness has been increased above the previous value to reduce the secondary flows. These types of airfoils have been referred in the literature as “spoon” airfoils.
The second set of stators has been designed to have the same spanwise distribution of pressure coefficient (Cp) on the suction surface than the first set. However, the thickness to chord ratio was increased along the span up to values around 20% to rise the velocity of the flow and to remove any separation bubble on the pressure side. The resulting shape of the profiles is representative of “hollow” airfoils.
The velocity triangles, chord distribution, leading and trailing edge locations and flowpath have been maintained between both sets. They have been tested with the same blades and at the same operating conditions with the intention of determining the impact of the profile thickness on the overall efficiency. The turbine characteristics: sensitivity to speed, specific work, Reynolds number and purge flows have been obtained for both sets.
The comparison of the results suggests that the efficiency of both types of airfoils exhibit the same behaviour, no significant differences in the results can be distinguished.
Experimental Investigation of the Unsteady Flow Field Downstream of a Counter-Rotating Two-Spool Turbine Rig
Authors: Lengani Davide , Santner Cornelia , Spataro Rosario , Paradiso Berardo , Göttlich Emil 
Published: July 2013

The paper presents an experimental investigation of the unsteady flow field in the two-spool counter-rotating transonic turbine at Graz University of Technology. The test setup consists of a high pressure (HP) stage, a diffusing mid turbine frame with turning struts (TMTF) and a shrouded low pressure (LP) rotor. The two rotors are mounted on mechanically independent shafts in order to provide engine-representative operating conditions. The rig was designed in cooperation with MTU Aero Engines and Volvo Aero within the EU project DREAM (ValiDation of Radical Engine Architecture SysteMs).
A two-sensor fast response aerodynamic pressure probe (2S-FRAP) has been employed to provide time-resolved aerodynamic area traverses downstream of the LP turbine. Such measurement allows estimating the total deterministic unsteadiness transported through the duct. In particular, it has been possible to isolate the structures induced by each rotor by means of the encoders mounted on the two shafts. A global ensemble averaged field, which takes into account the rotor-rotor interactions, is also provided. The time resolved distributions of the flow quantities are then discussed in details. The perturbations due to the HP rotor in terms of velocity and flow angle are negligible in this downstream plane. Indeed, the largest fluctuations of velocity are due to the TMTF-LP rotor interaction, they occur in the wake and secondary flows of the TMTF. Large fluctuations of static and total pressure are instead due to both rotors to the same extent.
The Sensitivity of 2D Compressor Incidence Range to In-Service Geometric Variation
Authors: Goodhand Martin N. , Miller Robert J. , Lung Hang W. 
Published: July 2013

The loss mechanisms which control 2D incidence range are discussed with an emphasis on determining which real in-service geometric variations will have the largest impact. For the majority of engine compressor blades (Minlet>0.55) both the negative and positive incidence limits are controlled by supersonic patches. It is shown that these patches are highly sensitive to the geometric variations close to, and around the leading edge. The variations used in this study were measured from newly manufactured as well as ex-service blades. Over most the high pressure compressor considered, it was shown that manufacture variations dominated.
The first part of the paper shows that, despite large geometric variations (∼10% of leading edge thickness), the incidence range responded in a linear way. The result of this is that the geometric variations have little effect on the mean incidence range of a row of blades. In the second part of the paper a region of the design space is identified where non-linear behavior can result in a 10% reduction in positive incidence range. The mechanism for this is reported and design guidelines for its avoidance offered. In the final part of the paper, the linear behavior at negative incidence and the transonic nature of the flow is exploited to design a robust asymmetric leading edge with a 5% increase in incidence range.
The Practical Design of Turbocharger Turbines Using a Throughflow-Based Optimisation Process
Authors: Cox Graham D. 
Published: July 2013

The modern trends in automotive turbocharger applications are towards the boosting of smaller internal combustion engines and more advanced systems including two-stage, turbo-compounding and hybrid electric-motor assist. Off-the-shelf turbochargers will become a smaller share of the market and the choice of major parameters for the compressor and turbine, e.g. speed and diameter, will fall outside of the manufacturer’s knowledge base. The selection of the compressor and turbine may even be independent. The only certainty is that the turbomachinery will have to be small, cheap and efficient.
To provide some guidance to the turbine designer, this paper presents the results of a study in which practical designs have been generated to cover the range of conceivable parameters, presented in non-dimensional terms to provide general applicability. All the designs are generated using a throughflow-based optimisation system in which the candidate geometries are assessed against mechanical as well as aerodynamic and inertia targets.
Analysis of the results gives clues to the form of the basic empiricism that would be of use in the preliminary design of automotive turbocharger turbines.
CREATE: Advanced CFD for HPC Performance Improvement
Authors: Pesteil A. , Cellier D. , Domercq O. , Perrot V. , Boniface J. C. 
Published: July 2013

The present paper provides an overview of technological evolutions aimed at improving the aerodynamic performance of Snecma’s High Pressure Compressors. Several concepts were investigated under its CREATE compressor research program, involving an extensive simulation effort. An overview of the computational approaches involved in the evaluation and selection of innovative and most promising concepts will be given in the paper. The main topics dealt with are:
1) Aeromechanical optimization of airfoils and flow path:
In recent years, great efforts have been made to improve the aerodynamic design of airfoils. Among them, optimization methods have been progressively implemented in the design process with an increased complexity logic. The latest methods used at Snecma involve multi-objective, multi-parameters aeromechanical optimization including mean camber line, stacking axis, flow path contouring and more. This work is illustrated by two practical examples.
2) Vortex generators:
In order to control the flow, vortex generators can be forecasted as a promising step forward. The goal is to create exogenous vorticity that will counter-balance the endogenous vorticity. Thus they appear as a tool to reduce losses and improve stability in highly loaded turbomachinery devices such as modern high pressure compressors. This section of the paper will give an overview of the dedicated numerical simulations completed.
3) Clocking:
Numerous studies are related to the benefit drawn from turbine clocking on turbomachinery performance. However, fewer examples of successful compressor clocking exist. The recent capability of computational fluid dynamics tools to reduce the computational effort necessary to investigate such an issue (by the use of harmonic balance methodology) gives the opportunity for a renewed evaluation.
4) Optimization of shroud leakage flow with main flow:
A strong interaction exists with the secondary flows originated in the inner flow path cavities. Coupled main flow path and cavities aerodynamic simulations were conducted to improve the relevance of the computations and understand the mechanisms involved.
5) Tandem bladings and splitters in axial rotors:
The last aspect of the study was focused on dual blading concepts. After a brief review of the literature, some simulations were carried out to explore the relevance of such concepts from the viewpoint of modern high pressure compressors performance improvement.
Steady State and Transient CFD Studies on Aerodynamic Performance Validation of a High Pressure Turbine
Authors: Murari Sridhar , Sunnam Sathish , Liu Jong S. 
Published: July 2013

With the advent of fast computers and availability of less costly memory resources, computational fluid dynamics (CFD) has emerged as a powerful tool for the design and analysis of flow and heat transfer of high pressure turbine stages. CFD gives an insight in to flow patterns that are difficult, expensive or impossible to study using experimental techniques. However, the application of CFD depends on its accuracy and reliability. This requires the CFD code to be validated with laboratory measurements to ensure its predictive capacity.
In the continual effort to improve analysis and design techniques, Honeywell has been investigating in the use of CFD to predict the aerodynamic performance of a high pressure turbine. Reynolds Averaged Navier Stokes (RANS), unsteady models like detached eddy simulation (DES), large eddy simulation (LES), and Scale Adaptive Simulation (SAS) are used to predict the aerodynamic performance of a high pressure turbine. Mixing plane approach is used to address the flow data transport across the stationary interface in RANS simulation. The film holes on blade surface and end walls for all the analysis are modeled by using actual film hole modeling technique.
The validation is accomplished with the test results of a high pressure turbine, Energy Efficient Engine (E3). The aerodynamic performance data at design point, typical off-design points are taken as test cases for the validation study. One dimensional performance parameters such as corrected mass flow rate, total pressure ratio, cycle efficiency, and two dimensional spanwise distributions of total pressure, total temperature and flow angle that are obtained from CFD results are compared with test data. Streamlines and flow field results at different measurement planes are presented to understand the aerodynamic behavior.
Meanline Modeling of Ported Shroud Turbocharger Compressor
Authors: Qiu Xuwen , Krivitzky Eric M. , Bollweg Peter 
Published: July 2013

The requirements for higher fuel economy and better diesel and gasoline engines demand a wider range in turbocharger compressor operation. Ported shroud compressor housing is one of the most commonly used techniques for compressor map width enhancement. Although the general mechanism of such a flow feature is well understood, there are no readily available design tools to guide the engineers at the preliminary design stage. Designers have had to rely on three-dimensional (3D) CFD tools to sort out many design variables, but these tools can be prohibitively expensive.
This paper explains how to develop a ported shroud compressor model on top of a commercial meanline compressor design program. The model considers some basic parameters, such as bleed location and geometry, which drive the recirculation or bypass flow through the bleed channel. The effects of the secondary flow on the compressor performance, such as pressure rise, efficiency, and stall and choke margins are also analyzed. The model prediction is validated with CFD simulation and test data.