bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quality of red blood cells washed using an automated cell processor with and without irradiation
Authors: Hansen Adele L. , Turner Tracey R. , Yi Qi‐Long , Acker Jason P. 
Published: November 2013

BackgroundSterile washing of red blood cells (RBCs) and use of an additive solution permits longer postwash storage. The effect of irradiation during this extended storage time is unclear.Study Design and MethodsRBCs were washed 14 days after collection using an automated cell processor and stored in saline‐adenine‐glucose‐mannitol. To determine how long washed and irradiated RBCs could be stored, units were irradiated 1, 4, 5, and 7 days after washing and in vitro quality was assessed. Determined limits of postwash storage time for washed and washed and irradiated RBCs were validated. Quality assessment included percent recovery, hemoglobin (Hb), hemolysis, extracellular K+, and adenosine triphosphate. Immunoglobulin (Ig)A levels were measured in the nonirradiated arm.ResultsRBCs irradiated 1 and 4 days after washing had unacceptably high hemolysis by Day 7 postwash, not meeting the acceptance criterion (<0.8% hemolysis in 98% of units with 95% confidence). Therefore, a 48‐hour maximum storage time after irradiation was chosen. Storage limits tested in the validation phase were as follows: washing on Day 14 and subsequent storage for 7 days (washed RBCs) and washing on Day 14, irradiation on Day 19, and subsequent storage for 48 hours (washed and irradiated RBCs). All units met criteria for Hb, hematocrit, hemolysis, and sterility for washed RBCs. However, RBCs were washed with less than 2 L of saline, and IgA levels in 27 of 40 units were too high to be suitable for transfusion to IgA‐deficient recipients.ConclusionThe extended expiry for washed and washed and irradiated RBCs met requirements for all indications except transfusion to IgA‐deficient recipients.
Analysis and Comparison of Primary Droplet Characteristics in the Near Field of a Prefilming Airblast Atomizer
Authors: Gepperth S. , Koch R. , Bauer H.-J. 
Published: November 2013

As the dominating parameters influencing the Sauter mean diameter of the spray produced by a prefilming airblast atomizer, the air velocity, liquid surface tension and atomizing edge thickness could be identified.
Correlations for the prediction of the droplet sizes produced by prefilming airblast atomizers are compared to droplet sizes measured close to the atomizing edge. The measurements were performed using three geometrical variants of a planar atomizer over a wide range of operating conditions. The diagnostics are based on a particle and ligament tracking technique, that enables simultaneous measurement of the liquid blobs and ligaments formed at the atomizing edge and the droplets in the primary breakup region of the atomizer.
The comparison between measured and calculated droplet diameter indicates, that most of the correlations are capable of reproducing the correct tendency. However, since the measurement data of most correlations were collected in a region where secondary atomization effects can obscure the initial droplet sizes in the primary breakup region, the droplet sizes are generally predicted too small.
Prediction of Unsteady Force for Axial Turbine Buckets (Effects of Nozzle-Bucket Axial Gap Length and Blade Count Ratio)
Authors: Nakajima Tomomi , Shikano Yoshio , Yamashita Yutaka 
Published: November 2013

The purpose of this study is to investigate the unsteady force acting on steam turbine buckets which is induced by a potential field and a wake. The authors have already proposed a new method that can separate the unsteady force into a potential field interaction and a wake interaction from the unsteady viscous flow computation. It is understood from the previous work that simple expressions may be written for the relationships between the nozzle-bucket axial gap length and the unsteady force, which means the amplitude and the phase of the unsteady force with the nozzle passing frequency component.
This paper adopts the blade count ratio as the factor to study the unsteady force of the bucket sections with different bucket heights in the same stage. Four points are seen from the results; points (a)–(c) do not depend on the blade count ratio. (a) The amplitudes of the unsteady force of each interaction can be approximated by an exponential or a power function of axial gap length. (b) The amplitudes of each interaction tend to become large when bucket turning angle is large. (c) The phase of the unsteady force of each interaction with the nozzle passing frequency component has a linear relationship with axial gap length. (d) The amplitudes of each interaction become the maximum value when the blade count ratio is 1.5.
Numerical Investigation of Condenser Pressure Effect on Last Stage Operation of Low Pressure Wet Steam Turbines
Authors: Stanciu Mugurel , Marcelet Meryem , Dorey Jean-Marc 
Published: November 2013

The flow in nuclear steam turbines is mainly affected in normal operating conditions by the condenser pressure, which depends on the heat sink temperature variations. This has an effect not only on the performance, but can also lead to undesired flow regimes and become related to safety issues.
The flow in the low pressure last stages is characterized by two main features: unsteadiness due to the rotation and asymmetry due to the exhaust hood. The effect of the condenser pressure on the stage flow is numerically analyzed with steady and full unsteady approaches. Three distinct flow regimes can be identified at nominal, low and high condenser pressures with different types of unsteady behavior.
A detailed investigation of the steam flow and possible consequences for the turbine safety is carried out at nominal and critical operating points. Comparisons of steady/unsteady approaches and the effect of the hood design are also presented.
Computational Analysis of Abradable Seal: Part 1
Authors: Pandit Rajeev Kumar , Innocenti Luca 
Published: November 2013

The usage of abradable seals in the secondary flow path of centrifugal compressors is very high whenever higher efficiency is the main requirement. This is due to the fact that when compared with other sealing technologies the rubbing of teeth into the abradable material allows for the formation of grooves that result in very tight clearances between static and rotating components.
Flow physics and mass flow leakage through abradable seals are strongly dependent on the presence of these grooves and their respective shapes. For cases where no grooves are formed, the seal leakage is mainly a function of inlet pressure, pressure ratio across the seal and tooth radial clearance. Once grooves are formed, the flow physics and seal leakage are also a function of groove dimensions and tooth axial position inside the groove.
The scope of this paper is to present results obtained from an extended numerical campaign that was performed to understand the effect of groove formation and teeth position on seal leakages. Computation Fluid Dynamics (CFD) was used to study these effects. To achieve higher accuracy of numerical results, all key parameters in CFD such as mesh topology, grid independence, y+ criterion and turbulence model were studied in great detail.
In cases where no grooves are present, the vena contracta (the narrowest point of the carry-over jet) is observed across the first tooth and its effect on flow physics at higher tooth gap is highlighted in this paper. For cases where grooves are present, it is seen that the flow field strongly depends on the following parameters:
1. Groove dimensions (e.g. depth and width),
2. Tooth radial clearance and
3. Tooth axial position inside groove.
The impact of all the above parameters on seal leakage have been discussed and described in this paper. Finally, seal leakages are compared for grooved geometry with respective non-grooved geometry cases (in terms of tooth radial clearance).
In the second part of the paper, the accuracy of CFD results is verified with available experimental data. For judicious comparison, geometrical specifications of all components and boundary conditions in CFD model and experimental setup were maintained very closely.
Development of New High-Performance Labyrinth Seal Using Aerodynamic Approach
Authors: Kuwamura Yoshihiro , Matsumoto Kazuyuki , Uehara Hidekazu , Ooyama Hiroharu , Tanaka Yoshinori , Nishimoto Shin 
Published: November 2013

As key technologies to improve the performance of steam turbines, various types of high performance seal, such as active clearance control (ACC) seals and leaf seals, have been developed by Mitsubishi Heavy Industries, LTD (MHI). Moreover, a new seal concept has also been developed, which remarkably reduces the leakage flow through the blade tip/base clearance by using an aerodynamic approach.
The main concept of this technology is to control and utilize the vortex structure in the cavities of the labyrinth seal by optimizing the cavity geometry. In the optimized geometry, locally-controlled flow on the upstream side of the fin tip causes a strong contraction of the leakage flow and reduces the discharge coefficient significantly. This concept allows for a remarkably reduced leakage flow, whilst keeping clearance at the same level as that of conventional set-up, and thus the risk of contact between rotating and stationary parts low. Therefore, this technology realizes reliable and durable seals with high performance. In addition, it is possible to keep manufacturing cost at the same level as conventional seals, since the structure of this seal is basically the same as the conventional one.
In the development of this technology, a parametric study using Computational Fluid Dynamics (CFD) was carried out to optimize the cavity geometry. The verification test was carried out for the optimized geometry under the real steam conditions. From the results, we confirmed that the optimized geometry reduced the discharge coefficient by up to 30%, compared to conventional seals.
Experimental Measurements of Ingestion Through Turbine Rim Seals: Part 4 — Off-Design Conditions
Authors: Scobie James A. , Sangan Carl M. , Teuber Roy , Pountney Oliver J. , Owen J. Michael , Wilson Michael , Lock Gary D. 
Published: November 2013

This paper describes results obtained from an experimental facility which models ingress through the rim seal into the upstream wheel-space of an axial-turbine stage. The experimental rig included 32 nozzle guide vanes and 41 symmetrical turbine blades, and the paper presents measurements of ε (the sealing effectiveness) for single- and double-clearance seals for both over-speed (where the blades rotate faster than at the design point) and under-speed conditions. The design flow coefficient was CF = 0.538, and tests were conducted for 0 < CF < 0.9, which is larger than the range experienced in engines. The measured values of ε were correlated by the ‘effectiveness equations’ for rotationally-induced (RI) and externally-induced (EI) ingress.
The correlated effectiveness curves were used to determine Φmin′ (the value of the sealing flow parameter when ε = 0.95), and the variation of Φmin′ with CF was in mainly good agreement with the theoretical curve for CI (combined ingress), which covered the transition from RI to EI ingress. Departure of the measured values of Φmin′ from the CI curve occurred at very low values of CF for all the seals tested; this was attributed to the effects of separation of the mainstream flow over the turbine blades at large ‘deviation angles’ between the flow and the blades.
The measurements are expected to be qualitatively similar to but quantitatively different from those experienced in engines.
Influence of Pressure on Markstein Number Effect in Turbulent Flame Front Propagation
Authors: Vukadinovic Vlade , Habisreuther Peter , Zarzalis Nikolaos , Suntz Rainer 
Published: November 2013

In gas turbine operation a turbulent flame is employed. Thus, better understanding of the turbulent flame propagation is the key for further optimisation of turbine combustors and reduction of the environmental footprint. As turbulent flames are exposed to stretch, the effect of flame-stretch interaction must be better understood especially at higher pressures.
In present study, turbulent burning velocity of two mixtures, hydrogen/air and propane/air, with negative and positive Ma, respectively are experimentally investigated in fan-stirred explosion vessel. For the investigation an optical laser method is employed based on the Mie-scattering of the laser light by smoke particles. Within this study the influence of initial parameters as initial pressure and turbulence intensity on the flame front propagation is investigated by giving special attention on influence of Ma variation. The experiments were performed at three different pressures 1, 2, 4 bar. The RMS fluctuation velocity was varied in the range of 0–2.77 m/s. The observed results are compared and discussed in detail.
CFD Investigation of Turbulent Premixed Flame Response to Transverse Forcing
Authors: Lee C. Y. , Cant R. S. 
Published: November 2013

Screech is a high frequency oscillation that is usually characterized by instabilities caused by large-scale coherent flow structures in the wake of bluff-body flameholders and shear layers. Such oscillations can lead to changes in flame surface area which can cause the flame to burn unsteadily, but also couple with the acoustic modes and inherent fluid-mechanical instabilities that are present in the system.
In this study, the flame response to hydrodynamic oscillations is analyzed in a controlled manner using high-fidelity Computational Fluid Dynamics (CFD) with an unsteady Reynolds-averaged Navier-Stokes approach. The response of a premixed flame with and without transverse velocity forcing is analyzed. When unforced, the flame is shown to exhibit a self-excitation that is attributed to the anti-symmetric shedding of vortices in the wake of the flameholder. The flame is also forced using two different kinds of low-amplitude out-of-phase inlet velocity forcing signals. The first forcing method is harmonic forcing with a single characteristic frequency, while the second forcing method involves a broadband forcing signal with frequencies in the range of 500–1000 Hz.
For the harmonic forcing method, the flame is perturbed only lightly about its mean position and exhibits a limit cycle oscillation that is characteristic of the forcing frequency. For the broadband forcing method, larger changes in the flame surface area and detachment of the flame sheet can be seen. Transition to a complicated trajectory in the phase space is observed. When analyzed systematically with system identification methods, the CFD results, expressed in the form of the Flame Transfer Function (FTF) are capable of elucidating the flame response to the imposed perturbation. The FTF also serves to identify, both spatially and temporally, regions where the flame responds linearly and nonlinearly. Locking-in between the flame’s natural self-excited frequency and the subharmonic frequencies of the broadband forcing signal is found to alter the dynamical behaviour of the flame.
A Parametric Numerical Study of the Effects of Inlet Swirl Distortion on a Transonic Compressor Stage
Authors: Ben Sghaier Taieb , Mehdi Ahad , Pachidis Vassilios , MacManus David 
Published: November 2013

The ingestion or manifestation of a vortical flow can have dramatic effects on an aero engine. It is therefore imperative to quantify these effects and understand their underlying mechanism. This numerical study analyses the response of a transonic compressor stage to the ingestion of different streamwise vortical distortions using steady-state CFD. The vortex is described using a number of features, which are varied and combined together in order to generate a wide range of different swirl disturbances. The initial aim of this research is to identify the vortex features which have the highest impact on compressor performance.
A numerical model of a compressor stage is generated which enables prescribed vortical flows to be imposed at the domain inlet. The method is validated against experimental data which was obtained under clean, undistorted conditions. The response of the compressor following the ingestion of a vortex is assessed both in terms of overall compressor performance parameters as well as more detailed aerodynamic characteristics.
The results show that the compressor is sensitive to the vortex magnitude, core size, polarity and radial location. Furthermore, co-rotating, high-strength vortices which are ingested in the near-hub region cause the most significant drop in pressure ratio and corrected mass flow. In contrast, counter-rotating vortices cause little change in compressor performance.
Overall, the work shows that modest swirl distortions can have a notable impact on the compressor performance and stability, and highlights the growing need to develop methods and an understanding of how this class of distortion can be evaluated during the engine design phase.
Compressor Leading Edge Sensitivities and Analysis With an Adjoint Flow Solver
Authors: Giebmanns A. , Backhaus J. , Frey C. , Schnell R. 
Published: November 2013

Based on the results of a prior study about fan blade degradation, which state a noticeable influence of small geometric changes on the fan performance, an adjoint computational fluid dynamics method is applied to systematically analyze the sensitivities of fan blade performance to changes of the leading edge geometry.
As early as during manufacture, blade geometries vary due to fabrication tolerances. Later, when in service, engine operation results in blade degradation which can be reduced but not perfectly fixed by maintenance, repair and overhaul processes. The geometric irregularities involve that it is difficult to predict the blade’s aerodynamic performance. Therefore, the aim of this study is to present a systematic approach for analyzing geometric sensitivities for a fan blade.
To demonstrate the potential, two-dimensional optimizations of three airfoil sections at different heights of a transonic fan blade are presented. Although the optimization procedure is limited to the small area of the leading edge, the resulting airfoil sections can be combined to a three-dimensional fan blade with an increased isentropic efficiency compared to the initial blade.
Afterwards, an adjoint flow solver is applied to quasi-three-dimensional configurations of an airfoil section in subsonic flow with geometric leading edge variations in orders representative for realistic geometry changes. Validations with non-linear simulation results demonstrate the high quality of the adjoint results for small geometric changes and indicate physical effects in the leading edge region that influence the prediction quality.
Combined Heat and Power: Gas Turbine Operational Flexibility
Authors: DiCampli James 
Published: November 2013

Combined heat and power (CHP) is an application that utilizes the exhaust heat generated from a gas turbine and converts it into a useful energy source for heating & cooling, or additional electric generation in combined cycle configurations. Compared to simple-cycle plants with no heat recovery, CHP plants emit fewer greenhouse gasses and other emissions, while generating significantly more useful energy per unit of fuel consumed. Clean plants are easier to permit, build and operate. Because of these advantages, projections show CHP capacity is expected to double and account for 24% of global electricity production by 2030. An aeroderivative power plant has distinct advantages to meet CHP needs. These include high thermal efficiency, low cost, easy installation, proven reliability, compact design for urban areas, simple operation and maintenance, fuel flexibility, and full power generation in a very short time period.
There has been extensive discussion and analyses on modifying purge requirements on cycling units for faster dispatch. The National Fire Protection Association (NFPA) has required an air purge of downstream systems prior to startup to preclude potentially flammable or explosive conditions. The auto ignition temperature of natural gas fuel is around 800°F. Experience has shown that if the exhaust duct contains sufficient concentrations of captured gas fuel, and is not purged, it can ignite immediately during light off causing extensive damage to downstream equipment.
The NFPA Boiler and Combustion Systems Hazards Code Committee have developed new procedures to safely provide for a fast-start capability. The change in the code was issued in the 2011 Edition of NFPA 85 and titled the Combustion Turbine Purge Credit. For a cycling plant and hot start conditions, implementation of purge credit can reduce normal start-to-load by 15–30 minutes. Part of the time saving is the reduction of the purge time itself, and the rest is faster ramp rates due to a higher initial temperature and pressure in the heat recovery steam generator (HRSG).
This paper details the technical analysis and implementation of the NFPA purge credit recommendations on GE Power and Water aeroderivative gas turbines. This includes the hardware changes, triple block and double vent valve system (or drain for liquid fuels), and software changes that include monitoring and alarms managed by the control system.
Ridge Estimation and Principal Component Analysis to Solve an Ill-Conditioned Problem of Estimating Unmeasured Gas Turbine Parameters
Authors: Shevchenko Maksim , Yepifanov Sergiy , Loboda Igor 
Published: November 2013

This paper addresses the problem of estimation of unmeasured gas turbine engine variables using statistical analysis of measured data. Possible changes of an engine health condition and lack of information about these changes caused by limited instrumentation are taken into account. Engine thrust is under consideration as one of the most important unmeasured parameters. Two common methods of aircraft gas turbine engine (GTE) thrust monitoring and their errors due to health condition changes are analyzed. Additionally, two mathematical techniques that allow reducing in-flight thrust estimation errors in the case of GTE deterioration are suggested and verified in the paper. They are a ridge trace and a principal component analysis.
A turbofan engine has been chosen as a test case. The engine has five measured variables and 23 health parameters to describe its health condition. Measurement errors are simulated using a generator of random numbers with the normal distribution. The engine is presented in calculations by its nonlinear component level model (CLM). Results of the comparison of thrust estimates computed by the CLM and the proposed techniques confirm accuracy of the techniques. The regression model on principal components has demonstrated the highest accuracy.