bluuebunny/crossref_metadata_2025 huggingface dataset:
Peakedness‐Based Staffing for Call Center Outsourcing
Authors: Van denSchrieck Jean‐Christophe , Akşin Zeynep , Chevalier Philippe
Published: July 2013

This study considers the staffing problem of a vendor call center in a co‐sourcing setting. The aim is to take short‐term variability and correlations in time for call arrivals at such a vendor call center into account. To do so, peakedness is proposed as a useful measure of the burstiness in the arrival stream. The study empirically demonstrates the presence of bursty arrivals at a call center and proposes an approach to the measurement of the peakedness of the arrival stream making use of standard call center data. The problematic nature of bursty arrivals in the context of call center co‐sourcing is demonstrated along with an asymptotic result establishing that the problem persists in large call centers. The study then analyzes two peakedness‐based staffing methods: one which is a well known extension of the square root staffing rule and another which makes use of the Hayward approximation principles. Both approaches are simple and enable the vendor to improve its staffing procedure with good accuracy.
The ‘Modified Union Jack’ Repair of a Lesser Tuberosity Osteotomy in Total Shoulder Arthroplasty: Surgical Technique and Radiological Results
Authors: Smith Geoffrey C. S. , Da Costa Thomas Mendes , Sarangi Partha
Published: July 2013

Background

Several different techniques have been described for repairing a lesser tuberosity osteotomy in shoulder arthroplasty, although all have potential drawbacks. We describe a novel repair technique and its radiological results.

Methods

All patients undergoing a total shoulder arthroplasty using a resurfacing humeral component from 2008 to date were identified retrospectively. Anteroposterior (AP) and axial radiographs at a minimum of 3 months postoperatively were used to assess union of the osteotomy fragment.

Results

Seventy-six total shoulder replacements in 65 patients were eligible for review. Seven were excluded as a result of inadequate radiographs. Sixty-six of 69 had united (95.6%). There were two cases (2.9%) of a complete non-union that was undisplaced. In one patient (1.4%), the osteotomy fragment had displaced and this was apparent on the initial postoperative AP radiograph.

Conclusions

The modified union jack repair technique is simple, fast, economical and reliable.
Scapular Winging
Authors: Gooding Benjamin W. T. , Geoghegan John M. , Wallace W. Angus , Manning Paul A.
Published: July 2013

This review explores the causes of scapula winging, with overview of the relevant anatomy, proposed aetiology and treatment. Particular focus is given to lesions of the long thoracic nerve, which is reported to be the most common aetiological factor.
Adolescents Exposed to Suicidal Behavior of Others: Prevalence of Self‐Harm and Associated Psychological, Lifestyle, and Life Event Factors
Authors: McMahon Elaine M. , Corcoran Paul , Keeley Helen , Perry Ivan J. , Arensman Ella
Published: July 2013

Exposure to suicidal behavior of others was examined among 3,881 Irish adolescents in the Child and Adolescent Self‐harm in Europe (CASE) study. One third of the sample had been exposed to suicidal behavior, and exposed adolescents were eight times more likely to also report own self‐harm. Exposed adolescents shared many risk factors with those reporting own self‐harm. Those reporting both exposure and own self‐harm presented the most maladaptive profile on psychological, life event, and lifestyle domains, but neither anxiety nor depression distinguished this group. Exposed adolescents are burdened by a wide range of risk factors and in need of support.
Risk and Protective Factors that Distinguish Adolescents Who Attempt Suicide from Those Who Only Consider Suicide in the Past Year
Authors: Taliaferro Lindsay A. , Muehlenkamp Jennifer J.
Published: July 2013

Data from the 2010 Minnesota Student Survey was analyzed to identify risk and protective factors that distinguished adolescents across three groups: no suicidality, suicidal ideation only, and suicide attempt. The population‐based sample included 70,022 students in grades 9 and 12. Hopelessness and depressive symptoms emerged as important risk factors to distinguish youth who reported suicidal ideation or behavior from those without a history of suicidality. However, these factors were not as important in differentiating adolescents who attempted suicidal from those who considered suicide but did not act on their thoughts. Instead, for both genders, self‐injury represented the most important factor to distinguish these youth. Other risk factors that differentiated the latter groups, but not the former groups, for males were dating violence victimization and cigarette smoking, and for females was a same‐sex sexual experience. Running away from home also seemed to increase the risk of a suicide attempt among youth in this study. Parent connectedness and academic achievement emerged as important protective factors to differentiate all the groups, yet neighborhood safety appeared to protect against the transition from suicidal thoughts to behavior. Findings from this study suggest risk and protective factors practitioners should target in clinical assessments and intervention programs to help prevent suicidal behavior among youth at greatest risk.
Trade Creation and Diversion Effects of Regional Trade Agreements: A Product‐level Analysis
Authors: Urata Shujiro , Okabe Misa
Published: July 2013

This paper examines the impacts of regional trade agreements (RTAs) on trade flows at product level, with a particular focus on trade creation and diversion. Based on estimation of the gravity equation, dealing with the zero trade flows and endogeneity bias problems, we analyse the impacts of various types of RTAs involving 67 countries for 20 products during the 1980–2006 period. We find that RTAs among developing countries tend to cause trade diversion compared with RTAs among developed countries. Taking the higher external tariff rates of developing countries compared with developed countries into consideration, our results suggest trade diversion is likely to be caused by remaining high tariffs on imports from non‐members. In addition, we find the trade creation effect for many products in the cases of Customs Unions and plurilateral RTAs. These results imply that trade creation would be caused by various factors besides the reduction in tariff rates. Based on these results, we draw a policy implication that external tariff rate reduction is an important factor in avoiding trade diversion in the formation of RTAs, in particular for RTAs among developing countries, while a large number of members and the common external tariff appear to be important for generating the trade creation effect.
Intravenous administration of desmopressin acetate to reverse acetylsalicylic acid‐induced coagulopathy in three dogs
Authors: Di Mauro Francesca M. , Holowaychuk Marie K.
Published: July 2013

Background

Acetylsalicylic acid (ie, aspirin) administration inhibits platelet aggregation in dogs and is associated with increased perioperative blood loss and transfusion requirements in people. Desmopressin acetate (DDAVP) is used to control or prevent bleeding in dogs with type 1 von Willebrand disease and is also widely reported in the human literature as an emergency antithrombotic reversal agent.

Key Findings

Three dogs undergoing surgery for intervertebral disc disease had marked prolongations in buccal mucosal bleeding time (BMBT) after aspirin administration. DDAVP was given intravenously preoperatively and achieved prompt reversal of the prolongation in BMBT. None of the dogs experienced intraoperative bleeding complications.

Significance

IV DDAVP corrected prolongations in BMBT in dogs given aspirin and should be considered in dogs requiring prompt reversal of aspirin‐induced coagulopathies to reduce the risk of bleeding complications.
Pneumomediastinum in cats: 45 cases (2000–2010)
Authors: Thomas Emily K. , Syring Rebecca S.
Published: July 2013

Objective

To characterize the incidence, etiology, presenting complaint, clinical course, and outcome of cats with pneumomediastinum.

Design

Retrospective study from the period of January 1st, 2000 to December 31st, 2010.

Setting

University teaching hospital.

Animals

Forty‐five cats with a radiographic diagnosis of pneumomediastinum.

Interventions

None.

Measurements and Main Results

Medical and radiographic records were reviewed to identify cats with a radiographic diagnosis of pneumomediastinum. Clinical data were retrieved, including signalment, history, presenting clinical signs, diagnostic test results, treatment, complications, and survival to discharge. In 31 of 45 (69%) cats the pneumomediastinum was secondary to an obvious inciting cause. General anesthesia with endotracheal intubation and positive pressure ventilation was the most common cause in 17 of 45 (38%) cases. This was followed by trauma in 12 of 45 (27%) cats, and tracheal foreign bodies in 2 of 45 (4%) cats. Spontaneous pneumomediastinum (unknown underlying cause) was diagnosed in 14 of 45 (31%) of cases. Onset of clinical signs and diagnosis of spontaneous pneumomediastinum was preceded by emesis in 6 of 14 cats. Common presenting signs were tachypnea seen in 27 of 45 (60%) cats, increased respiratory effort in 26 of 45 (58%) cats, and subcutaneous emphysema in 30 of 45 (66%) cats. Concurrent pneumothorax was identified in 21 of 45 (47%) cats, pleural effusion in 10 of 45 (22%), and pneumoretroperitoneum in 21 of 45 (47%). The mainstay of treatment was supportive care and treatment of the underlying disease process. The prognosis for recovery was good, with 87% survival until hospital discharge.

Conclusions

Pneumomediastinum in cats is an infrequently diagnosed condition. It is often secondary to an event such as general anesthesia with endotracheal intubation and positive pressure ventilation but less frequently may occur spontaneously. The prognosis is good with appropriate supportive care.
Management of acute respiratory distress syndrome in a French Bulldog using airway pressure release ventilation
Authors: Sabino Catherine V. , Holowaychuk Marie , Bateman Shane
Published: July 2013

Objective

To describe the successful clinical management of a dog with acute respiratory distress syndrome (ARDS) using airway pressure release ventilation (APRV).

Case Summary

An 18‐month‐old female French Bulldog was presented for routine ovariohysterectomy and correction of brachycephalic airway obstruction syndrome. Following the surgical procedures, the dog developed aspiration pneumonia and ARDS. Her clinical condition failed to improve with conventional pressure‐support mechanical ventilation and she was subsequently managed with APRV. She recovered fully and exhibited no clinical or radiographic abnormalities during follow‐up examinations.

New or Unique Information Provided

This is the first reported use of APRV to manage refractory hypoxemia associated with ARDS in a dog. This alternative mode of mechanical ventilation can be considered a feasible alternative in canine patients with ARDS.
Evaluation of the shock index in dogs presenting as emergencies
Authors: Porter Adam E. , Rozanski Elizabeth A. , Sharp Claire R. , Dixon Kursten L. , Price Lori Lyn , Shaw Scott P.
Published: July 2013

Objectives

To (1) determine a reference interval for shock index (SI) [defined as heart rate (HR)/systolic blood pressure (SBP)], in a group of healthy dogs, and (2) compare SI in healthy dogs with dogs presenting to the emergency room (ER) deemed to be in or not in a state of shock.

Design

Prospective study.

Animals

Sixty‐eight clinically normal dogs, 18 dogs that were presented to the ER deemed to be in shock and 19 dogs presenting to the ER not deemed to be in shock.

Setting

University teaching hospital.

Interventions

Peripheral or central venous blood sampling.

Measurements and Main Results

Heart rate and SBP were recorded on simulated presentation (healthy dogs), and emergency presentations for both dogs deemed to be in shock and dogs not deemed in shock. Dogs in shock had a median SI of 1.37 (0.87–3.13), which was significantly higher than both other groups; dogs not deemed in shock had median SI 0.73 (0.56–1.20),P< 0.0001 and healthy dogs had median SI 0.78 (0.37–1.30)P< 0.0001), respectively. Receiver operator characteristic curve analysis suggested a SI cut‐off of 1.0, yielding an area under the receiver operator characteristic (AUROC) of 0.89 (Specificity (Sp) 89, Sensitivity (Sn) 90) when comparing dogs deemed in shock with healthy dogs, and 0.92 (Sp 95, Sn 89) when comparing dogs in shock with to dogs not deemed in shock.

Conclusions

The SI is an easy and noninvasive patient parameter that is higher in dogs that are deemed to be in shock than both healthy dogs and dogs presented as emergencies but not deemed to be in a state of shock. The measurement of SI may have some benefit in clinical assessment of emergency patients.
Reliability-Based Factors of Safety for Vortex Induced Vibration Fatigue Using Field Measurements
Authors: Tognarelli Michael , Fontaine Emmanuel , Beynet Pierre , Santosa Mikhail , Marcollo Hayden
Published: July 2013

The development of a vortex induced vibration (VIV) fatigue factor of safety (FoS) consistent with state-of-the-art industry design practice is cast within the coherent framework of reliability analysis. The proposed methodology consists of the following steps: (i) define the failure criteria or limit-state function (ii) setup a deterministic analysis model (iii) characterize the uncertainties involved in the problem (iv) propagate the uncertainties through the deterministic model and assess the probability of failure due to VIV fatigue and (v) calculate the FoS required to achieve a given failure probability. The proposed methodology is demonstrated by determining the FoS associated with using state-of-the-art VIV prediction models to attain varying reliability levels (probabilities of failure) in a hypothetical design scenario. Prediction uncertainty is based herein on measured flow and response data for several full-scale drilling risers working in the field. Results indicate that depending on the reliability level required of a particular design, different FoS than those that currently appear in guidance may be appropriate. Results also indicate the sensitivity of the FoS to the riser and prevailing current type, analysis program and input parameters, and accumulation of conservatism in aggregate versus single-event damage predictions.
Experimental and Numerical Plastic Response and Failure of Laterally Impacted Rectangular Plates
Authors: Liu B. , Villavicencio R. , Guedes Soares C.
Published: July 2013

Experimental and numerical results of drop weight impact test are presented on the plastic behavior and fracture of rectangular plates stuck laterally by a mass with a hemispherical indenter. Six specimens were tested in order to study the influence of the impact velocity and the diameter of the indenter. The impact scenarios could represent abnormal actions on marine structures, such as ship collision and grounding or dropped objects on deck structures. The tests are conducted on a fully instrumented impact tester machine. The obtained force-displacement response is compared with numerical simulations, performed by the LS-DYNA finite element solver. The simulations aim at proposing techniques for defining the material and restraints on finite element models which analyze the crashworthiness of marine structures. The mesh size and the critical failure strain are predicted by numerical simulations of the tensile tests used to obtain the mechanical properties of the material. The experimental boundary conditions are modeled in order to represent the reacting forces developed during the impact. The results show that the critical impact energy until failure is strongly sensitive to the diameter of the striker. The shape of the failure modes is well predicted by the finite element models when a relatively fine mesh is used. Comments on the process of initiation and propagation of fracture are presented.
Impact of Product Design Representation on Customer Judgment
Authors: Reid Tahira N. , MacDonald Erin F. , Du Ping
Published: July 2013

When researchers ask customers to judge product form during the design process, they often manipulate simplified product representations, such as silhouettes and sketches, to gather information on which designs customers prefer. Using simplified forms, as opposed to detailed realistic models, make the analysis of gathered information tractable and also allows the researcher to guide customer focus. The theory of constructed preferences from psychology suggests that the product form presented will influence customer judgments. This paper presents a study in which subjects were shown computer sketches, front/side view silhouettes, simplified renderings, and realistic renderings to test the extent to which a variety of judgments including opinions, objective evaluations, and inferences are affected by form presentation. Results show a variety of phenomena including preference inconsistencies and ordering effects that differed across type of judgment. For example, while inferences were consistent across form, opinions were not. An eye tracker identified differences in viewing strategies while making decisions. Associated data, such as fixation times and fixation counts, provide additional insight into findings.
Optimizing Gas Turbine Bearing Vibration Using 2D D’Alembert’s Equation
Authors: Ogbonnaya Ezenwa A. , Ugwu Hyginus U. , Theophilus-Johnson Kombo , Forsman Peter B. , Orji Charles U.
Published: July 2013

The ability to identify faulty equipment under severe conditions allows the manufacturers and operators to take appropriate proactive measures to rectify the faults and provide an assessment for early detection of the engine defects that could lead to catastrophic failure. This work therefore shows that such counter measures can be carried out by optimization, modeling, simulation or using a reliable analysis of gas turbine engine, rotor shaft and bearing vibration data through 2-Dimensional D’Alembert’s equation. Gas turbine plants on industrial duty for electricity generation were thus used to actualize the research. The data for vibration amplitude of rotor bearings from the reference engine which varied between 0.19 and 3.81 mm/s were compared with those obtained from a failed engine of similar characteristics just before failure and used for the simulation and modeling. The given engine speed and active load were also determined as falling between 7264 rpm to 7436 rpm and 10 MW to 20 MW respectively. A well packaged computer program code-named “MELBF” written in C++ programming language was developed. The results show that the machine should not be run beyond 3.81 mm/s vibration amplitude in order to avoid resonance and downtime of the engine.
The Influence of the Characteristics of a Centrifugal Compressor on System Stability and Distortion Response
Authors: Cousins William T. , Davis Milt W.
Published: July 2013

In many future propulsion applications, the compression system size will be such that either an all centrifugal or an axial-centrifugal compressor will provide an efficiency benefit to the propulsion cycle over an all-axial compressor. The aerodynamic response of a centrifugal compressor provides an inherent stability benefit to a compression system. This work examines the influence of a centrifugal impeller on axial-centrifugal compression system stability under clean and distorted conditions. A dynamic parallel compressor model is used to simulate the behavior, and comparisons to data are performed. The effects of pressure distortion are examined, and details of the physics of the system response explained. The influence of the location of the stall trigger on the stalling and recovery behavior of the compression system is demonstrated and discussed. The work demonstrates that a simple dynamic parallel compressor model can be utilized to assist in the understanding and enhancement of compression system dynamic behavior involving centrifugal impellers.
Fuelling Micro Gas Turbines With Vegetable Oils: Part I — Straight and Blended Vegetable Oil Properties
Authors: Cavarzere A. , Morini M. , Pinelli M. , Spina P. R. , Vaccari A. , Venturini M.
Published: July 2013

Current energy policies tend to encourage the production of renewable energy for environmental reasons and energy independence. Among renewable sources, biomass can play a key role, because of economic, environmental and political factors, such as the need to diversify and improve energy supply, reduce the greenhouse effect and support rural areas.

For the case of liquid biofuels derived from agricultural crops, several possibilities can be considered, such as straight vegetable oil (SVO), oil-derived esters, bioethanol or blends with conventional fuels (diesel or gasoline). The use of SVOs and their derivatives usually poses some problems, that essentially derive from their much higher viscosity and higher boiling temperature.

In order to evaluate the technical feasibility of the use of SVOs within gas turbine combustors, this paper reports the results of the experimental characterization of different vegetable oils, derived from dedicated crops. Moreover, blends composed of diesel and vegetable oil in different concentrations (from pure diesel to pure vegetable oil) are also considered and their experimental characterization is also reported, with particular focus on blend viscosity. The considered vegetable oils were obtained from different types of oilseeds (rapeseed, sunflower, soybean) and were cultivated under different agronomic scenarios. The SVO properties determined experimentally are SVO elemental composition, lower heating value, density, specific heat and viscosity, for which this paper provides a practical overview, coming both from experiments and literature data.
Optical Structures for High Speed Gas Temperature Measurement
Authors: Harpin A. P. R. , Langton C.
Published: July 2013

This paper reports on recent work to produce a sensor based on optical waveguides. The geometry of the structure will be described and its response to changes in gas temperature will be modelled. The validity of the modelling will be examined by comparing with actual results — taken with preliminary flowing gas/heat gun experiments, and by using the technique of heating the sensor with a laser and measuring the decay time, and examining its causes. The response of a bulk sapphire sensor of the sort currently suited to installation in a gas turbine will be similarly examined. This will show the advantage of the waveguide sensor in terms of speed and the pros and cons of each type will be evaluated for a gas turbine, using published data for gas flows and convection coefficients in a gas turbine representative location.

The requirements for high speed of operation (i.e. rapid response to changes in surrounding gas temperature) and low conduction to the sensor package/mounting will be examined and the arrival at a waveguide based structure will be justified. A diaphragm structure is proposed, modelled and fabricated. It is found that there are tradeoffs in the design for speed of response against conduction crosstalk, and limitations on the gas flows that will yield accurate results. These will be examined theoretically and experimentally.

Due to the use of fibre optic interconnects between the sensor and the remote interrogator, EMI (electromagnetic interference) issues are well controlled. The packaging scheme used to package such a sensor including its optical connection will be described, and its performance in harsh environments such as an engine exhaust will be demonstrated.

Finally, the performance of such a sensor in a reciprocating engine manifold will be presented, together with an interpretation of the results and conclusions therefrom.
Transient Temperature Measurements in the Contact Zone Between Brush Seals of Kevlar and Metallic Type for Bearing Chamber Sealing Using a Pyrometric Technique
Authors: Flouros Michael , Stadlbauer Martin , Cottier Francois , Proestler Stephan , Beichl Stefan
Published: July 2013

For the past 25 years brush seal technologies evolved into the aero engine designs and more general into the gas turbine world not only for sealing gas areas at different pressure levels but also for sealing gas/liquid environments. This is the case in an aero engine where the bearing chambers are sealed. Aero engine bearing chambers enclose oil lubricated components such bearings and gears. In order to avoid contamination of the turbo machinery through oil loss, air blown seals are used to retain the oil into the bearing chamber. Oil loss may cause coking or ignition with the probability of an uncontained destruction of rotating parts like disks or blades. It may also cause contamination of the air conditioning system with oil fumes thus cause health problems to the passengers and crew from such exposure.

The most widely known seals for bearing chamber sealing are the labyrinth seals but in the recent years also brush seals and carbon seals are used. The latter are contact seals, that is, they may be installed having zero clearance to the rotating part and lift during operation when their air side is pressurized.

During this survey an actual aero engine bearing chamber was modified to run with brush seals in a simulating rig. Two types of brush seals were used: a) with bristles made of Kevlar and b) bristles made of metallic material. Both types were installed with an overlap to the rotor.

The targets set were twofold: a) to measure the transient temperatures in the rotor and particularly in the contact zone between the bristles and the rotor and b) to measure the air leakage through the seals at different operating conditions.

In order to obtain the transient temperature measurements with high fidelity, a new pyrometric technique was developed and was applied for the first time in brush seals. This technique has enabled placing the pyrometer into the bristle’s pack of the seal adjacent to the rotating surface and could record the frictional temperature evolution in the bristles/rotor contact zone during acceleration or deceleration of the rotor. Additionally, the air consumption of the seals was measured and was compared to the air consumption through the labyrinth seals. For the metallic brush seal, up to 80% of the required sealing air can be saved which can result in return into a reduction in fuel burned by up to 1%. Further, a design simplification of the bearing chamber architecture can be achieved by taking into account the reduced air flow. Even though the rotor was accelerated to high speeds up to 19500rpm, the produced temperature overshoots in the seal/rotor contact zone have caused no deterioration in either the materials or the oil.

This work is part of the European Union funded research programme ELUBSYS (Engine LUBrication System TechnologieS) within the 7th EU Frame Programme for Aeronautics and Transport (AAT.2008.4.2.3).
Fuel System Design for the More Electric Engine
Authors: Morioka Noriko , Oyori Hitoshi
Published: July 2013

This paper describes the system design of an electric motor-driven fuel pump system for the MEE (More Electric Engine). The MEE is a new aircraft engine system concept which will reduce fuel burn and CO2 emissions, and improve engine safety, reliability and maintainability. At the initial concept design stage of the MEE, a feasibility study indicated that the electric fuel pump system helped improve engine efficiency. The selected fuel pump system configuration for the MEE was a fixed displacement gear pump system, the speed of which is controlled by an electric motor. Simplification of the fuel system will be expected because the electric gear pump itself is used as a metering device, but there are several technical challenges which should be overcome to realize the system.

One of the technical challenges involves ensuring fuel metering accuracy via motor speed control. To address the issue, studies of the fuel flow rate feedback system were performed. A novel flow feedback system was investigated and the potential to ensure metering accuracy was confirmed.

The other technical challenge is the wide speed range operation of the gear pump system. If only a single electric gear pump is used in the MEE system, the pump should accommodate a speed range of 5 to 100% because the ground starting flow rate is about 5% of the maximum flow. Operation at such low speeds is significantly harsh for the LP pump pressurizing capability and bearing film lubrication. However, optimized pump performance and operational condition were established, and it is expected that a single pump system, in which both LP and HP pumps are directly motor-driven via a single shaft, can be constructed. In addition, there is a technical challenge involved in supplying electrical power to the pump motor during the windmill engine start-up.

The system design focused on the above technical challenges, and the consequent feasibility of the simplified MEE fuel pump system construction was confirmed.
Comparing Lensed and Un-Lensed Optical Spot Probes for Blade Tip Timing Measurements
Authors: Hockaday Bruce D.
Published: July 2013

Detection of airfoil time-of-arrival with optical probes has been evolving since the 1980s. Time of arrival data are used to infer airfoil stresses caused by vibration through a sequence of manipulations. The data conversion begins by converting arrival time to blade position, so blade deflection can be determined from the expected non-vibrating position. Various methods are used in the industry to convert deflection data to frequency, amplitude, and stress, which is beyond the scope of this paper. Regardless of the analytical approach used, producing accurate stress information relies on the precise detection and measurement of time-of-arrival, which equates to blade position.

Optical spot probes are commonly employed for blade tip sensing. Two dominant types of fiber optic probes are used in industry today; 1) un-lensed probes having their numerical aperture (NA) defined by the optical fiber and 2) lensed probes, utilizing an imaging lens to control numerical aperture and spot size. The lens adds cost and complexity to the probe but allows the probe to be installed farther away from the blade tip while keeping the sensing area small. The low-cost un-lensed probes must be installed close to the blade tip since the optical beam diverges at the angle defined by the NA of the fiber. These probes are considered interchangeable, with little regard to the inherent geometric optical differences of the beam transmission into the space where the blade travels.

This paper presents a laboratory study comparing the performance characteristics between lensed and un-lensed spot probes. The study evaluates signal amplitude and rise time and arrival errors due to optical interaction with varying tip radii geometry. The study reports rise time as return signal strength as a function of circumferential location and sensing gap. Arrival errors are reported as circumferential location errors compared to a sharp reference edge as a function of the blade-to-sensor gap. The work is presented in terms of arrival location, producing information that is independent of rotation speed and vibratory mode.
Automated Multi-Objective Optimization Process for Preliminary Engine Design
Authors: Kupijai Philipp , Bestle Dieter , Flassig Peter M. , Kickenweitz Daniel
Published: July 2013

The main challenge within the preliminary engine design phase is that only a small amount of knowledge about the engine is available, but decisions with huge impact on product life cycle costs have to be made. The paper will demonstrate how efficient optimization strategies can support the design engineer to find a proper engine concept. The proposed preliminary engine design process calculates engine performance and basic geometries. It has been automated in order to enable design studies and optimization. The design task is formulated as multi-objective optimization problem, and different solution strategies are tested and discussed. Besides a direct model optimization several surrogate modeling techniques are implemented and a reduction of the multi-objective problem to a single-objective problem using the ε-constraint method is applied which significantly increases process efficiency.
Surrogate Modeling for Simultaneous Engine Cycle and Technology Optimization for Next Generation Subsonic Aircraft
Authors: Kestner Brian , Schutte Jeff S. , Tai Jimmy C. M. , Perullo Christopher A. , Mavris Dimitri N.
Published: July 2013

This paper presents an engine sizing and cycle selection study of ultra high bypass ratio engines applied to a subsonic commercial aircraft in the N+2 (2025) timeframe. NASA has created the Environmentally Responsible Aviation (ERA) project to serve as a technology transition bridge between fundamental research (TRL 1–4) and potential commercial application (TRL 7). Specifically, ERA is focused on subsonic transport technologies that could reach TRL 6 by 2020 and can be integrated into an advanced vehicle concept to simultaneously meet the ERA project metrics for noise, emissions, and fuel burn. An important variable in exploring the technology trade space is the selection of the optimal engine cycle for use on the advanced aircraft. Previous literature demonstrated the cycle optimization using a design of experiments (DOE) to explore the engine cycle design space for a pre-defined technology package. However, since the optimal engine cycle is dependent upon the specific technology package, this process would have to be repeated to ensure optimal performance for each technology package. With more than 80 technologies to be analyzed, the combinatorial space of technology packages is enormous. As a result, executing a DOE to find the optimum engine cycle for each technology package is infeasible. To address this issue, it is proposed to use surrogate models that encompass the engine cycle and technology design space to enable fast and accurate optimization of the engine cycle for any given technology package.

This paper describes the generation and analysis of surrogate models used for technology assessment and cycle optimization of an ultra high bypass geared turbofan engine architecture. The first study in the paper shows that a single surrogate model can be used to accurately simulate both a technology and cycle design space. To demonstrate the proposed surrogate modeling approach, the cycle design space for three different technology packages was analyzed. This study demonstrated that when an optimal cycle is found within the constrained interior of a design space, the surrogate modeling approach is quite accurate. The study also established that the surrogate models can also be used to assess potential cycles at the boundaries or even outside of the region for which they were trained.
Design Feasibility of Annular Target Thrust Reversers
Authors: Gonzalez-Ruiz Enaut , Mahmood Tashfeen , Sethi Vishal , Pilidis Pericles
Published: July 2013

Concerns for ecological aviation products and the objective of reducing pollutants to meet ACARE (Advisory Council for Aeronautics Research in Europe) targets address, among other initiatives, the necessity of reducing the overall weight of the aircraft. One way of dealing with the problem of aircraft weight is by investigating thrust reversers. Reducing the reverser weight will have favourable effects on fuel consumption and CO2 emissions.

This paper discusses the target type thrust reverser concept. This concept was proposed by NASA and has a potential of reducing the reverser weight on future high bypass ratio turbofan engines. A feasibility study of the annular target thrust reverser in terms of engine performance and reverse thrust achieved was carried out. It comprises 2D CFD analyses of the thrust reverser and the effect of the reverser on the engine performance for different deflector configurations.

The turbofan engine chosen for this study is CUTS_TF (Cranfield University Twin Spool Turbo Fan) which is similar to the GE90-85B and the information available in the public domain [1] [2] is used for the engine performance analysis along with the gas turbine performance software, GasTurb 10 [3]. CFD analyses were performed using the FLUENT software [4] to investigate the thrust reverser flow dynamics at landing at maximum reverse thrust.
Experimental Investigation of the Acoustic Reflection Coefficient of a Modeled Gas Turbine Impingement Cooling Section
Authors: Jörg Christoph , Wagner Michael , Sattelmayer Thomas
Published: July 2013

The thermoacoustic stability of gas turbines depends on a balance of acoustic energy inside the engine. While the flames produce acoustic energy, other areas like the impingement cooling system contribute to damping. In this paper, we investigate the damping potential of an annular impingement sleeve geometry embedded into a realistic environment. A cold flow test rig was designed to represent real engine conditions in terms of geometry, and flow situation. High quality data was delivered by six piezoelectric dynamic pressure sensors. Experiments were carried out for different mean flow velocities through the cooling holes. The acoustic reflection coefficient of the impingement sleeve was evaluated at a downstream reference location. Further parameters investigated were the number of cooling holes, and the geometry of the chamber surrounding the impingement sleeve. Experimental results show that the determining parameter for the reflection coefficient is the mean flow velocity through the impingement holes. An increase of the mean flow velocity leads to significantly increased damping, and to low values of the reflection coefficient.
Efficient Operation of a Gas Turbine on Methanol Using Chemical Recuperation
Authors: Duwig Christophe , Nyberg Björn , Thern Marcus
Published: July 2013

Environmental and political concerns, together with new legislations, are pushing for a fuel shift in the power industry and more generally for many thermal applications. Adding to the coming decrease of oil and natural availability (or price increase), it opens avenues for new fuels. Among those, alcohols are strong candidates. In fact, short alcohols are easily produced and stored and require only moderate modifications of existing combustion systems. For example, operating an existing gas turbine (GT) on methanol requires moderate modifications (mainly in the combustion system). However, methanol can be used more efficiently. Unlike methane or other hydrocarbons that decompose at high temperature (1000K), methanol undergoes an endothermic decomposition at low temperatures (400K to 600K) to give CO and H2. It therefore opens avenue for coupling the GT with a chemical recuperation system. In other words, the methanol will be cracked using the waste heat of the flue gases with a gain in fuel heating value hence the original fuel is thermally upgraded. The present study will investigate the upgraded fuel combustion properties. The laminar flame speed of the upgraded fuel/air mixtures will be presented and compared to methane and methanol under conditions relevant to GT combustion. Several upgraded fuel compositions will be considered depending on the water content in the feed methanol. Further, we consider a recuperated micro GT (Turbec T100) based cycle fueled with methanol. The numerical study focuses on different thermodynamic cycles. Firstly, a reference case is considered assuming a direct fueled GT. Further, cycles including the cracker are studied keeping the power constant. The fuel efficiency gain due to the cracker will be investigated as function of the water content in the feed methanol. Finally, a case including CO2-removal will be presented and it will be shown that the cracker enables an efficient carbon capture and sequestration scheme.
Aircraft Propulsion System Flight Test: Analysis and Evaluation Challenges and Solutions
Authors: Binkley Brian A. , Malloy Donald J. , Patterson Grant T. , Hansen Eric R. , Kidman David S.
Published: July 2013

The paper describes the challenges and solution methodologies associated with the flight test and evaluation of the propulsion system for a twin engine military legacy aircraft. Recent flight-test programs evaluated the effects of temperature distortion and biased engine inlet total temperature measurement (TT2) on engine scheduling and compressor stability margin. The challenges are associated with the limited instrumentation and the repeatability of the flight-test points. During the test program it was necessary to employ techniques to extend the usefulness of the data beyond that provided by the acquired and reduced data sets to address the challenges associated with flight-test analysis. The challenges were addressed using mathematical models, engine cycle decks, uninstalled ground-test data, computational fluid dynamics, or some combination of these. Several specific challenges and solutions are described in detail in the paper.
Microwave Blade Tip Clearance Measurements: Principles, Current Practices and Future Opportunities
Authors: Maslovskiy Alexander , Bakulin Mikhail , Snitko Maksim
Published: July 2013

This article is devoted to the principles of construction of the microwave tip clearance measurement system in gas turbine engines and describes a microwave sensor that designed to operate in temperatures up to 1700C with a resolution of 0.05 mm. The sensor can effectively operate in dirty environments and has the ability to see through oil, combustion products, and other common contaminants. Also the article is devoted to the use of microwave measurement systems to solve other practical problems (measurements tip-timing, vibration, pressure and etc). The main applications of these systems are discussed on the basis of the plant tests and laboratory tests of aircraft turbine engines.
Cycle Design Exploration Using Multi-Design Point Approach
Authors: Schutte Jeffrey , Tai Jimmy , Sands Jonathan , Mavris Dimitri
Published: July 2013

The focus of this study is to compare the aerothermodynamic cycle design space of a gas turbine engine generated using two on-design approaches. The traditional approach uses a single design point (SDP) for on-design cycle analysis, where off-design cycle analysis must be performed at other operating conditions of interest. A multi-design point (MDP) method performs on-design cycle analysis at all operating conditions where performance requirements are specified. Effects on the topography of the cycle design space as well as the feasibility of the space are examined. The impacts that performance requirements and cycle assumptions have on the bounds and topography of the feasible space are investigated. The deficiencies of a SDP method in determining an optimum gas turbine engine will be shown for a given set of requirements. Analysis will demonstrate that the MDP method, unlike the SDP method, always obtains a properly sized engine for a set of given requirements and cycle design variables, resulting in an increased feasible region of the aerothermodynamic cycle design space from which the optimum performance engine can be obtained.
Assessing Alternative Fuels for Helicopter Operation
Authors: Alexiou A. , Tsalavoutas A. , Pons B. , Aretakis N. , Roumeliotis I. , Mathioudakis K.
Published: July 2013

At present, nearly 100% of aviation fuel is derived from petroleum using conventional and well known refining technology. However, the fluctuations of the fuel price and the vulnerability of crude oil sources have increased the interest of aviation industry in alternate energy sources. The motivation of this interest is actually twofold: firstly alternative fuels will help to stabilize price fluctuations by relieving the world wide demand for conventional fuel. Secondly alternative fuels could provide environmental benefits including a substantial reduction of emitted CO2 over the fuel life cycle. Thus, the ideal alternative fuel will fulfil both requirements: relieve the demand for fuels derived from crude oil and significantly reduce CO2 emissions.

In the present paper, the effects of various alternative fuels on the operation of a medium transport/utility helicopter are investigated using performance models of the helicopter and its associated turboshaft engine. These models are developed in an object-oriented simulation environment that allows a direct mechanical connection to be established between them in order to create an integrated model. Considering the case of a typical mission for the specific helicopter/engine combination, a comparative evaluation of conventional and alternative fuels is then carried out and performance results are presented at both engine and helicopter level.
Hot-Jet Noise Test of a Revised Notched Nozzle
Authors: Ishii Tatsuya , Tanaka Nozomi , Oinuma Hideshi , Oishi Tsutomu
Published: July 2013

Jet noise remains a significant noise component in modern commercial aero-engines. A high-speed flow mixing with the surrounding air constitutes noise sources behind the nozzle. One noise-reduction technology is a mixing device attached to the nozzle. Several fixed-geometry mixers such as chevrons have been studied by both computational and experimental approaches. The authors have previously proposed a notched nozzle with dents allocated along the nozzle lip and discussed its ability to reduce the noise level. The revised notch was expected to suppress the broadband jet-mixing noise as well as additional noise at higher frequencies. However, further assessments are required before proceeding to a large-scale engine test in an outdoor environment. First, the influence of the gas temperature on acoustic results must be tested because the temperature affects the mean jet velocity and sound propagation. As the preliminary noise test in the previous paper was limited to the cold-jet condition, far-field noise data under the hot-jet condition should be investigated. Second, the aerodynamic performance must be evaluated. Data on the flow rate and thrust would help in considering the aerodynamic performances between the baseline, notched, and chevron nozzles. This study focuses on noise tests for the finer-notched nozzle under the hot-gas condition. A small jet engine for model jet planes was employed to generate a high-temperature jet. An engine test stand was designed to monitor the engine performance data, consisting of the pressure and temperature at several positions, the fuel flow rate, and the thrust. The hot-jet test with and without the mixing device served as a compact and flexible test for aerodynamic evaluation of the nozzle. The noise test results under the hot-jet condition with this rig showed that the noise reduction characteristics of the finer-notched nozzle are different from those of conventional mixers.
Scavenge Flow in a Bearing Chamber With Tangential Sump Off-Take
Authors: Chandra Budi , Collicott Steven H. , Munson John H.
Published: July 2013

A tangential sump design is employed in several aero-engines mainly due to its simplicity and compactness. However various problems have prompted investigations of the sump design. An experimental program at Purdue University [1, 2] was conducted to investigate the characteristics of a tangential sump design like one used in the AE3007 aero-engine. The research employed a transparent chamber to allow unprecedented view of the flow inside the bearing chamber. It was quickly found that a persistent liquid pooling near the drain entrance of a tangential sump obstructs the outflow to the scavenge pump. The air flow near the drain entrance has been shown to have strong reverse flow, even with, or perhaps due to, substantial over-scavenging. Various modifications were tested with varying degrees of success. The work highlights limitations of a tangential sump design. Based on the lessons learned, a new sump design was proposed. Preliminary test of the new sump design has shown positive results.