bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of Influence of Two-Stage Turbocharging System on Engine Performance Using a Pre-Design Model
Authors: Chen Jinke , Zhuge Weilin , Zheng Xinqian , Zhang Yangjun 
Published: November 2013

As the result of increasingly strict emission regulations and demand of fuel reduction, current light and medium duty engines are being highly boosted with complex two-stage turbocharging systems. The purpose of this work is to investigate the influence of two-stage turbocharging system parameters on the engine performance and the optimization of these parameters.
An analytical pre-design model of the series two-stage turbocharging system for an internal combustion engine was developed, which builds the relationship between total pressure ratio, total expansion ratio and other two-stage turbocharging system parameters. Considering total expansion ratio as a function of expansion ratio between HP and LP turbine, minimum total expansion ratio can be determined using this model. The ratio of total pressure ratio to total expansion ratio, engine brake thermal efficiency and total heat exchange of coolers are considered as the parameters for engine performance evaluation. Influence of two-stage turbocharging system parameters, such as efficiency of compressors and turbines, cooling water temperature, cooler efficiency, pressure loss of coolers, EGR rate and bypass gas rate of wastegate, etc., on engine performance was analyzed respectively.
Results show that the performance of a two-stage turbocharging engine is impacted mainly by LP turbocharger efficiency, intercooler performance and air filter performance.
Experimental Validation of Methods Providing Boundary Conditions to Simulate the Evaporation Process of Water Injected Into High Speed Air Flow
Authors: Nagabhushan P. S. , Rossetti A. , Barabas B. , Schnitzler J. P. , Kefalas A. , Benra F. K. , Dohmen H. J. 
Published: November 2013

Water injection into a high speed air flow has been recently investigated by many scientists and is still an important field of research in gas turbine technology. To study the behavior of droplets in gas turbines, expensive experimental tests and their validation with analytical and Computational Fluid Dynamics (CFD) models are necessary.
The Euler-Lagrange approach can be used to tackle these problems due to their capability in tracking particles along the domain, relative ease in formulating and applying them to the current industrial problems in terms of acceptable computational cost. However, providing spray boundary conditions using Euler-Lagrange approach is quite challenging because the spray pattern depends upon various parameters like spray angle, velocity, diameter distribution etc. In this paper, to obtain these parameters, two different approaches are described. The first approach depends on an analytical model for velocity and spray angle injection conditions and the second approach depends on an Euler free surface simulation. For diameter distribution, Rosin Rammler distribution function and experimental data are used. When combined together these lead to four particle injection conditions. The results achieved from all the four cases are compared with the experimental data of water droplet evaporation in a high speed air flow obtained from a hot air test rig operating at conditions of real gas turbines.
Low-Flow-Coefficient Centrifugal Compressor Design for Supercritical CO2
Authors: Lettieri C. , Baltadjiev N. , Casey M. , Spakovszky Z. 
Published: November 2013

This paper presents a design strategy for very low flow coefficient multi-stage compressors operating with supercritical CO2 for Carbon Capture and Sequestration (CCS) and Enhanced Oil Recovery (EOR). At flow coefficients less than 0.01 the stage efficiency is much reduced due to dissipation in the gas-path and more prominent leakage and windage losses. Instead of using a vaneless diffuser as is standard design practice in such applications, the current design employs a vaned diffuser to decrease the meridional velocity and to widen the gas path. The aim is to achieve a step change in performance.
The impeller exit width is increased in a systematic parameter study to explore the limitations of this design strategy and to define the upper limit in efficiency gain. The design strategy is applied to a full-scale re-injection compressor currently in service. Three-dimensional, steady, supercritical CO2 CFD simulations of the full stage with leakage flows are carried out with the NIST real gas model. The design study suggests that a non-dimensional impeller exit width parameter b2* = (b2/R)ϕ of 6 yields a 3.5 point increase in adiabatic efficiency relative to that of a conventional compressor design with vaneless diffuser. Furthermore, it is shown that in such stages the vaned diffuser limits the overall stability and that the onset of rotating stall is likely caused by vortex shedding near the diffuser leading edge. The inverse of the non-dimensional impeller exit width parameter b2* can be interpreted as the Rossby number. The investigation shows that, for very low flow coefficient designs, the Coriolis accelerations dominate the relative flow accelerations, which leads to inverted swirl angle distributions at impeller exit. Combined with the two-orders-of-magnitude higher Reynolds number for supercritical CO2, the leading edge vortex shedding occurs at lower flow coefficients than in air suggesting an improved stall margin.
Influence of Blade Profile on Secondary Flow in Ultra-Highly Loaded Turbine Cascades at Off-Design Incidence
Authors: Tsujita Hoshio 
Published: November 2013

An increase of aerodynamic loading of turbine blade leads to the reductions of the numbers of blade and stage. As a result, the size and the weight of gas turbines could be reduced. However, the secondary flow becomes much stronger because of the steeper pressure gradient across the cascade passage, and consequently deteriorates the turbine efficiency. Therefore, it is very important to minimize the loss generation increased by the increase of loading. In the present study, the influences of blade profile on the secondary flow structure in a linear ultra-highly loaded turbine cascade (UHLTC) at off-design incidence were investigated in detail by using a numerical method.
The computations were performed for the flow in three types of UHLTC at zero and off-design incidences. The present three types of turbine blade are same in the inlet and the outlet metal angles but different in the length of the blade suction surface. The verification of the computed results was performed by comparing with the experimental oil flow visualizations and the measured static pressure on the blade surface. The decrease of the length of blade suction surface increased both the profile loss and the secondary loss according to the increase of incidence angle in the positive range. The positive incidence not only strengthened the horseshoe and the passage vortices but also induced a new vortex along the blade suction surface on the end-wall. The incidence angle at which the newly formed vortex appeared was influenced by the blade profile. Moreover, the newly formed vortex affected the strength of the pressure side leg of horseshoe vortex.
Development of a Turning Mid Turbine Frame With Embedded Design: Part II — Unsteady Measurements
Authors: Spataro Rosario , Göttlich Emil , Lengani Davide , Faustmann Christian , Heitmeir Franz 
Published: November 2013

The paper, which is constituted by two parts, presents a new setup for the two-stage two-spool facility located at the Institute for Thermal Turbomachinery and Machine Dynamics (ITTM) of Graz University of Technology. The rig was designed in order to reproduce the flow behavior of a transonic turbine followed by a counter rotating low pressure stage like those in high bypass aero-engines. The meridional flow path of the machine is characterized by a diffusing S-shaped duct between the two rotors. The role of wide chord vanes placed into the mid turbine frame is to lead the flow towards the LP rotor with appropriate swirl.
Experimental and numerical investigations performed on this setup over the last years showed that the wide chord struts induce large wakes and extended secondary flows at LP inlet flow. Moreover, large deterministic fluctuations of pressure, which may cause noise and blade vibrations, were observed downstream of the LP rotor. In order to minimize secondary vortices and to damp the unsteady interactions, the mid turbine frame was redesigned to locate two zero-lifting splitters into the vane passage.
While in the first part paper the design process of the splitters and the time-averaged flow field were presented, in this second part the measurements performed by means of a fast response probe will support the explanation of the time-resolved field. The discussion will focus on the comparison between the baseline case (without splitters) and the embedded design.
Development of a Continuous Coupling of Steam Turbine Blades by Contact of Shrouds
Authors: Hlous Jan , Kubin Zdenek , Kellner Josef , Misek Tomas , Prchlik Lubos 
Published: November 2013

As modern blade designs are breaking historical technical barriers to blade loading levels, adding extra damping is needed to improve blade resistance against excitation. For this purpose, various ways of blade coupling are used. One of most commonly used method is to design a special shroud geometry that makes it touch the adjacent shroud through an interface. These contacting surfaces are assembled with a preload providing a normal acting force. Performing FEM analyses is required to study the influence of manufacturing tolerances and assembly procedure on contact conditions.
In recent years, a new coupling design has been developed in Skoda Power. This work describes the analytical approach selected for simulation of bladed disk assembly procedures regarding blade-to-blade and blade-to-disk contact conditions and consequent stress distribution. First, the common method of assembly that is used for similar blades with free-standing design was studied with an unsatisfactory coupling condition results. Consequently, a new assembly method was developed to improve the disadvantages of the common method. Experimental measurements were performed to verify the credibility of computational analyses for both methods and confirmed their results.
The contact conditions were studied both in state after assembly and during operation, and based on the findings, dynamic properties were predicted. A full scale bladed disk was manufactured for experimental tests to investigate dynamic behaviour. Based on the results of the test, it was possible to choose the most convenient FEM model that can be used for blade tuning during blade design procedure. Additionally, vibration damping was evaluated for several mode shapes and as a whole the measurement confirmed benefits of the coupling design.
Comparison of BLISS 2000 and CO in Turbine Blade MDO for Aircraft Engine
Authors: Yang Junjie , Chen Jingyang , Yan Jiachao 
Published: November 2013

In this paper, the two methods of CO and BLISS 2000 are compared by using a classical numerical example firstly. The results show that the BLISS 2000 performs better in both computational accuracy and efficiency, because the scale of the optimization problem, such as the number of variables and constraints, in the BLISS 2000 is less than that in the CO. Moreover, the BLISS 2000 optimizes directly the system objectives while the CO focuses on decreasing the discrepancy between the coupled variables in different fields.
The two methods are then applied to an aerodynamics-thermal-structure coupled design problem for the turbine blades of an aircraft engine. Based on the results of sensitivity analysis, the number of design variables is reduced from 34 to 12. To eliminate the impact of the surrogate models on the different MDO algorithms as much as possible, the same initial Kriging surrogate models are not refreshed during the MDO procedures. Without the high fidelity simulation such as CFD and FEM analysis in the MDO processes, the BLISS 2000 method shows the more powerful capability of the convergence than that of the CO method, as shown in the numerical example. The optimization steps of the system level for BLISS 2000 are approximate 1/5 of those for CO, and the iteration number of step in the sub-system level with BLISS 2000 is only about 1/8 of that with CO.
Based on the weight sum of two objectives, the BLISS 2000 shows more robust than the CO because both weight reduction and aerodynamic efficiency are improved in the BLISS 2000 but only the blade weight reduction is gained in the CO. For other multi-objective optimization approaches, however, it still needs to be demonstrated through more studies.
Experimental Identification of Force Coefficients of Large Hybrid Air Foil Bearings
Authors: Wang Yu Ping , Kim Daejong 
Published: November 2013

Foil bearing technology using air or gas as a lubricant has been around since the mid 60’s, and it made significant progress in its reliability, performance, and applications. Even if significant progress has been made to the technology, their commercial applications to relatively large machines with journal shaft diameter bigger than 100mm was not reported. This paper presents dynamic characteristics of hybrid (hydrodynamic + hydrostatic) air foil bearing (HAFB) with diameter of 101.6mm and length of 82.6mm. The test rig configuration in this work is a floating HAFB on a rotating shaft driven by electric motor, and the HAFB is under external load.
HAFB stiffness coefficients were measured using both 1) time-domain quasi-static load-deflection curves, and 2) frequency-domain impulse responses, and HAFB damping coefficients were measured using only impulse responses. The HAFB direct stiffness coefficients measured from both methods are close to each other in the range of 4∼7 MN/m depending on speed, load, and supply pressure, but frequency domain method shows larger scatter in the identified coefficients. HAFB coefficients simulated with linear perturbation method using a bump stiffness matched to the load-deflection characteristics at 18,000rpm show reasonably good agreements with experimentally measured values.
The Development of an Air Injection System for the Forced Response Testing of Axial Compressors
Authors: Wegman E. , Snedden G. , van der Spuy S. J. , Holzinger F. , Schiffer H. P. , Mårtensson H. , Őstlund J. 
Published: November 2013

A phase-controllable air injection exciter system was developed to enable measurement of the forced response properties of a transonic axial compressor blisk. The project was performed as part of the FP7 European framework programme project FUTURE. The eventual aim of this project is to improve existing turbomachinery blade flutter prediction methods.
The development and manufacturing of the exciter system was performed by the Council for Scientific and Industrial Research (CSIR) in Pretoria, South Africa. The exciter system consists of 15 air injectors, each with its own servo motor and controller. The injectors consist of a small rotating disc with a specific number of holes equispaced around the periphery, rotating within a pressurised volume. When the holes are rotated, using a servo motor, past an exit tube an air pulse is generated that is injected upstream of the compressor. The controllers enable adjustment of the relative phase angle between the exciters and in this way a pattern that resembles different nodal diameters can be excited on the rotor blisk.
Once the construction of the system was completed, it was transferred to Stellenbosch University, South Africa for sub-scale testing on a low speed compressor. The purpose of the sub-scale tests was to commission and verify the operation of the exciter system. The tests started with simple in-phase tests and then worked towards more complex test parameters that included frequency sweeps through the natural frequency of the compressor blades. The tests showed that it is possible to generate a blade response of different nodal diameters using the exciters. The blade response was also found to vary depending on the number of rotor holes, air supply pressure and sweep rate used for the exciters.
Following completion of the sub-scale tests, the completed system was transferred to the transonic compressor test facility of the Technical University Darmstädt (TUD) where both free flutter and forced response experiments were performed on a purpose-designed blisk in the transonic compressor test rig. The experimental campaign was successfully completed with the forced response experiments showing that the air injection system could be used to measure the response characteristics of the blisk.
Postdiagnosis C-Reactive Protein and Breast Cancer Survivorship: Findings from the WHEL Study
Authors: Villaseñor Adriana , Flatt Shirley W. , Marinac Catherine , Natarajan Loki , Pierce John P. , Patterson Ruth E. 
Published: November 2013

Abstract
Background: Serum C-reactive protein (CRP) is a marker of acute inflammatory response and has been associated with health outcomes in some studies. Inflammation and immune response may have potential prognostic implications for breast cancer survivors.
Methods: The Women's Healthy Eating and Living Study includes 2,919 early-stage breast cancer survivors with serum collected 2 years postdiagnosis and follow-up for clinical outcomes over approximately 7 years. CRP concentrations were measured using high-sensitivity electrochemiluminescence assay. Outcomes, including all-cause mortality, breast cancer–specific mortality, and additional breast cancer events were oncologist verified from medical records and death certificates. Cox proportional hazards models were conducted with adjustment for potential confounding factors to generate HRs and 95% confidence intervals (CI).
Results: CRP concentrations in women diagnosed with breast cancer were associated with death due to any cause, death due to breast cancer, and additional breast cancer events, after adjustment for sociodemographic and cancer characteristics (lnCRP: P &lt; 0.05 for all three outcomes). The HR for women with (vs. without) acute inflammation suggests a threshold effect on overall survival, rather than a dose–response relationship (≥10.0 mg/L vs. &lt;1 mg/L: HR, 1.96; 95% CI, 1.22–3.13). Associations were similar for breast cancer–specific mortality (HR, 1.91; 95% CI, 1.13–3.23) and any additional breast cancer–related event (HR, 1.69; 95% CI, 1.17–2.43).
Conclusions: Acute inflammation status (CRP ≥ 10 mg/L) may be an important independent biomarker for long-term survival in breast cancer survivors.
Impact: Interventions to decrease circulating CRP concentrations in breast cancer survivors with acute inflammation may improve prognosis. Cancer Epidemiol Biomarkers Prev; 23(1); 189–99. ©2013 AACR.
Adventitial Nab-Rapamycin Injection Reduces Porcine Femoral Artery Luminal Stenosis Induced by Balloon Angioplasty via Inhibition of Medial Proliferation and Adventitial Inflammation
Authors: Gasper Warren J. , Jimenez Cynthia A. , Walker Joy , Conte Michael S. , Seward Kirk , Owens Christopher D. 
Published: November 2013

Background—
Endovascular interventions on peripheral arteries are limited by high rates of restenosis. Our hypothesis was that adventitial injection of rapamycin nanoparticles would be safe and reduce luminal stenosis in a porcine femoral artery balloon angioplasty model.

Methods and Results—

Eighteen juvenile male crossbred swine were included. Single-injury (40%–60% femoral artery balloon overstretch injury; n=2) and double-injury models (endothelial denudation injury 2 weeks before a 20%–30% overstretch injury; n=2) were compared. The double-injury model produced significantly more luminal stenosis at 28 days,
P
=0.002, and no difference in medial fibrosis or inflammation. Four pigs were randomized to the double-injury model and adventitial injection of saline (n=2) or 500 μg of nanoparticle albumin-bound rapamycin (nab-rapamycin; n=2) with an endovascular microinfusion catheter. There was 100% procedural success and no difference in endothelial regeneration. At 28 days, nab-rapamycin led to significant reductions in luminal stenosis, 17% (interquartile range, 12%–35%) versus 10% (interquartile range, 8.3%–14%),
P
=0.001, medial cell proliferation,
P
<0.001, and fibrosis,
P
<0.001. There were significantly fewer adventitial leukocytes at 3 days,
P
<0.001, but no difference at 28 days. Pharmacokinetic analysis (single-injury model) found rapamycin concentrations 1500× higher in perivascular tissues than in blood at 1 hour. Perivascular rapamycin persisted ≥8 days and was not detectable at 28 days.

Conclusions—
Adventitial nab-rapamycin injection was safe and significantly reduced luminal stenosis in a porcine femoral artery balloon angioplasty model. Observed reductions in early adventitial leukocyte infiltration and late medial cell proliferation and fibrosis suggest an immunosuppressive and antiproliferative mechanism. An intraluminal microinfusion catheter for adventitial injection represents an alternative to stent- or balloon-based local drug delivery.
Objective Identification of the Intertropical Convergence Zone: Climatology and Trends from the ERA-Interim
Authors: Berry Gareth , Reeder Michael J. 
Published: November 2013

Abstract
An objective method for the identification of the intertropical convergence zone (ITCZ) in gridded numerical weather prediction datasets is presented. This technique uses layer- and time-averaged winds in the lower troposphere to automatically detect the location of the ITCZ and is designed for use with datasets including operational forecasts and climate model output. The method is used to create a climatology of ITCZ properties from the Interim ECMWF Re-Analysis (ERA-Interim) dataset for the period 1979–2009 to serve as an indicator of the technique's ability and a benchmark for future comparisons. The automatically generated objective climatology closely matches the results from subjective studies, showing a seasonal cycle in which the oceanic ITCZ migrates meridionally and the land-based ITCZ features are predominantly summertime phenomena. Composites based on the phase of the El Niño–Southern Oscillation index show a major shift in the mean position and changes in intensity of the ITCZ in all ocean basins as the index varies. Under La Niña conditions, the ITCZ intensifies over the Maritime Continent and eastern Pacific, where the ITCZ weakens over the central and equatorial eastern Pacific. An analysis of changes in the ITCZ and its divergence during the period 1979–2009 indicates that the mean position of the ITCZ shifts southward in the western Pacific and a broad global intensification of the convergence into ITCZ regions. The relationship between tropical cyclogenesis and the ITCZ is also examined, finding that more than 50% of all tropical cyclones form within 600 km of the ITCZ.
Century-Scale Intensity Modulation of Large-Scale Variability in Long Historical Temperature Records
Authors: Yuan Naiming , Fu Zuntao 
Published: November 2013

Abstract
Large-scale variability in long historical temperature records around the North Atlantic Ocean is analyzed by means of power spectral density (PSD) analysis and detrended fluctuation analysis (DFA). It is found that the intensity of large-scale variability is changeable with time, and long memory analysis can be used to detect this possible intensity variation quantitatively. By estimating long-term memory (LTM) in subrecords of different time intervals, a century-scale variation of LTM is revealed, which further indicates a century-scale intensity modulation of the large-scale temperature variability. At the beginning of the nineteenth and twentieth centuries, the large-scale variability is more apparent, whereas in the second half of the nineteenth and twentieth centuries the large-scale variability becomes less significant. Considering the importance of large-scale variability, the findings herein suggest a new perspective on the understanding of climatic change.