bluuebunny/crossref_metadata_2025 huggingface dataset:
Flow cytometry in Spermatology: A bright future ahead
Authors: Ortega‐Ferrusola C , Gil MC , Rodríguez‐Martínez H , Anel L , Peña FJ , Martín‐Muñoz P
Published: August 2017

Contents

Techniques such as mass spectrometry have led to unprecedented knowledge of the proteins that are present in the spermatozoa of humans and other mammals. However, in spite of their high‐throughput and fractioning techniques, most of the techniques in use only offer average values for the entire sperm population. Yet, ejaculate is very heterogeneous, and average values may mask relevant biological information.The application of flow cytometry may overcome this disadvantage, allowing proteomic analysis at the single‐cell level. Moreover, recent advances in cytometry, allowing multiple analyses within a single cell combined with powerful statistical tools, as an expanding subfield in spermatology, are described. The increased use of advanced flow cytometers in andrology laboratories will allow the rapid development of multiparametric, multicolour flow cytometry in andrology that will expand the clinical applications and research possibilities of flow cytometry‐based proteomic approaches, especially in the subfields of clinical andrology and sperm biotechnology.
What drives the localization of Spanish multinationals in developing and transition countries?
Authors: Alguacil Maite , Martí Josep , Orts Vicente
Published: August 2017

In this paper, we investigate the location determinants of Spanish multinational firms in developing and transition economies. We pay particular attention to the role played by market potential and agglomeration economies as decisive factors in location. We also analyze whether, beyond the observed attributes, there are any significant differences across regions in terms of attracting foreign affiliates. With this aim, we estimate a mixed logit model, which allows us to endogenously consider the existence of complex substitution patterns among different destinations. Our results confirm that Spanish investment in developing and transition countries depends on market potential and agglomeration externalities. The intensity of these externalities, however, depends on the nationality of competitors, greater rivalry being observed among Spanish‐owned affiliates. Furthermore, our findings show that the location of multinational firms responds both to factors related to the local business environment, including the cost and quality of labor and infrastructures, and to the existence of specific regional effects.
Export tightening, competition, and firm innovation: Evidence from the renminbi appreciation
Authors: Dai Mi , Yu Miaojie , Zhao Chunming
Published: August 2017

This paper investigates how firm innovation reacts to changes in competitive pressure in the export market. We use the exchange rate appreciation of the renminbi during 2005–2007 as a natural experiment and exploit its differential impact on Chinese manufacturing firms with different export exposure. The appreciation reduced exports and imposed greater competitive pressure on exporters relative to non‐exporters. In response, exporters increased innovation activities more than non‐exporters. Using a difference‐in‐difference approach, we find that the research and development expenditure of exporters increased by 11% more than that of non‐exporters during the appreciation period, and the new product development of exporters increased by nearly 1.5 times more than that of non‐exporters. These results highlight the important role of competition in providing incentives for firm innovation.
The Role of Scientific Excellence in the Changing Meaning of Maize in Mexico
Authors: Castro Colina Libertad , Montpetit Éric
Published: August 2017

Making policy is giving a meaning to objects. This perspective on policy making gained importance in the 1990s with the emergence of discursive approaches. In this article, we use the concepts of Hajer's discourse coalition approach to shed light on the evolving meaning of maize in Mexican society. Specifically, we trace a parallel between the evolution of biotechnology policy and discourses on maize over a 25‐year period. The article argues that until recently, the protection against biotechnological manipulations enjoyed by maize has been bolstered by a discourse granting the plant a special status in the country's history. However, the emergence of a new discourse grounded on the practice of scientific excellence is now challenging the old perspectives, and also finding support among government officials. As a result, the Mexican policies granting maize special protection is changing, and this policy change will likely trigger changes in the symbolic meaning of maize.
Sluggish cognitive tempo in children and adolescents with higher functioning autism spectrum disorders: Social impairments and internalizing symptoms
Authors: Reinvall Outi , Kujala Teija , Voutilainen Arja , Moisio Anu‐Liisa , Lahti‐Nuuttila Pekka , Laasonen Marja
Published: August 2017

Sluggish cognitive tempo (SCT) was introduced in 1980s in the field of attention deficit hyperactivity disorder (ADHD). Studies indicate that symptoms of SCT are separate from symptoms of ADHD and independently associated with multiple domains of functioning in clinical groups and in typical development. We assessed whether similar pattern would apply to higher functioning autism spectrum disorders (ASD). Children with higher functioning ASD (N = 55; 5−15 years) were divided into the ASD+High SCT (n = 17), the ASD+Medium SCT (n = 18) and the ASD+Low SCT (n = 20) groups based on parent‐rated daydreaming and slowness on the Five to Fifteen questionnaire (FTF). The groups were compared on SCT‐related impairments found in previous studies: social skills, academic functioning, psychiatric symptoms, and processing speed. Assessment methods were the FTF, the Development and Well‐Being Assessment, and the Coding subtest of the WISC‐III. The ADHD symptoms were statistically controlled due to the overlap between SCT and ADHD. The ASD+High SCT and ASD+Medium SCT groups were significantly more likely to have the most pronounced social impairments, and the ASD+High SCT group had significantly higher rate of internalizing disorders compared to the ASD+Low SCT group. Our results suggest that children with higher functioning ASD and high or medium levels of SCT symptoms could be at higher risk for psychosocial impairments than children with higher functioning ASD with low levels of SCT symptoms. Co‐occurring ADHD symptoms do not explain the finding. Recognizing SCT symptoms in higher functioning ASD would be important to targeting preventive support.
Urinary tract infections caused by ESBL‐producing Enterobacteriaceae in renal transplant recipients: A systematic review and meta‐analysis
Authors: Alevizakos Michail , Nasioudis Dimitrios , Mylonakis Eleftherios
Published: August 2017

Background

Urinary tract infections (UTIs) are the most common infectious complications among renal transplant recipients (RTR). UTIs caused by extended‐spectrum beta‐lactamase (ESBL)‐producing Enterobacteriaceae (ESBL‐PE) have been associated with inferior clinical outcomes and increased financial burden.

Methods

We performed a systematic review and meta‐analysis by searching through the PubMed and EMBASE databases (to May 20, 2016) and identifying studies that reported data on the number of RTR who developed an ESBL‐PE UTI.

Results

Our analysis included seven studies, out of 357 non‐duplicate articles, that provided data on 2824 patients. Among them, 10% (95% confidence interval [CI] 4%‐17%) developed an ESBL‐PE UTI over their follow‐up periods. The proportion of RTR affected by an ESBL‐PE UTI was 2% in North America (95% CI 1%‐3%), 5% in Europe (95% CI 4%‐6%), 17% in South America (95% CI 10%‐27%), and 33% in Asia (95% CI 27%‐41%). In addition, patients affected with an ESBL‐PE UTI were 2.75‐times (95% CI 1.97‐3.83) more likely to suffer a recurrent UTI.

Conclusions

Based on a limited number of studies, one in 10 RTR will develop a UTI caused by an ESBL‐PE, and these patients face an almost 3 times greater risk of recurrence. A more rigorous monitoring of RTR, both during and after resolution of their infection, should be evaluated in order to reduce the incidence and the clinical impact of these resistant infections.
Effect of positive perioperative donor and recipient respiratory bacterial cultures on early post‐transplant outcomes in lung transplant recipients
Authors: Howell Crystal K. , Paciullo Christopher A. , Lyon G. Marshall , Neujahr David , Lyu Peter , Cotsonis George , Hurtik Michael
Published: August 2017

Background

It is standard practice to administer prophylactic antibiotics post lung transplantation. However, no studies have evaluated the impact of culture positivity. The purpose of this study was to evaluate early post‐transplant outcomes of culture‐positive and culture‐negative lung transplant (LT) recipients and the appropriateness of the empiric regimens used.

Methods

Adult patients who received an LT at Emory University Hospital between January 1, 2010 and August 31, 2015 were reviewed and stratified into three groups: (i) culture‐positive appropriate empiric treatment, (ii) culture‐positive inappropriate empiric treatment, and (iii) culture‐negative. Antibiotics were defined as appropriate if bacteria were sensitive to the empiric regimen. The primary endpoint was 30‐day mortality. Secondary endpoints included hospital length of stay (LOS), intensive care unit (ICU) LOS, percent neutrophil count in a bronchoalveolar lavage (BAL) sample, presence of airway ischemia, and appropriateness of the empiric antibiotic regimen.

Results

Nine, zero, and four patients died within 30 days in the culture‐positive appropriate (n = 113), culture‐positive inappropriate (n = 5), and culture‐negative groups (n = 29) (P = .564) respectively. The median hospital LOS was 19, 16, and 15 days respectively. Median ICU LOS was 6, 5, and 7 respectively. The respective percent neutrophil counts in the BAL fluid were 79, 83, and 65. The presence of airway ischemia was only documented in eight patients, all in the culture‐positive appropriate group.

Conclusion

We did not identify an association between antibiotic appropriateness and 30‐day mortality, hospital LOS, or ICU LOS in post‐LT recipients.
Multidrug‐resistant Enterobacteriaceae, Pseudomonas aeruginosa, and vancomycin‐resistant Enterococcus: Three major threats to hematopoietic stem cell transplant recipients
Authors: Satlin Michael J. , Walsh Thomas J.
Published: August 2017

Hematopoietic stem cell transplant (HSCT) recipients are uniquely threatened by the emergence of multidrug‐resistant (MDR) bacteria because these patients rely on immediate active antimicrobial therapy to combat bacterial infections. This review describes the epidemiology and treatment considerations for three challenging MDR bacterial pathogens in HSCT recipients: MDR Enterobacteriaceae, including extended‐spectrum β‐lactamase (ESBL)‐producing and carbapenem‐resistant Enterobacteriaceae (CRE), Pseudomonas aeruginosa, and vancomycin‐resistant Enterococcus (VRE). These bacteria are common causes of infection in this population and bacteremias caused by these organisms are associated with high mortality rates. Carbapenems remain the treatments of choice for serious infections due to ESBL‐producing Enterobacteriaceae in HSCT recipients. Administration of β‐lactam agents as an extended infusion is associated with improved outcomes in patients with severe infections caused by P. aeruginosa. Older agents used for the treatment of CRE and MDR P. aeruginosa infections, such as polymyxins and aminoglycosides, have major limitations. Newer agents, such as ceftazidime‐avibactam and ceftolozane‐tazobactam have great potential for the treatment of Klebsiella pneumoniae carbapemenase‐producing CRE and MDR P. aeruginosa, respectively, but more pre‐clinical and clinical data are needed to better evaluate their efficacy. Daptomycin dosages ≥8 mg/kg/day are recommended to treat VRE infections in this population, particularly in the setting of increasing daptomycin resistance. Strategies to prevent these infections include strict adherence to recommended infection control practices and multidisciplinary antimicrobial stewardship. Last, gastrointestinal screening to guide empirical therapy and the use of polymerase chain reaction‐based rapid diagnostics may decrease the time to administration of appropriate therapy for these infections, thereby leading to improved outcomes.
Direct Digital Subtractive Manufacturing of a Functional Assembly Using Voxel-Based Models
Authors: Lynn Roby , Dinar Mahmoud , Huang Nuodi , Collins James , Yu Jing , Greer Clayton , Tucker Tommy , Kurfess Thomas
Published: August 2017

Direct digital manufacturing (DDM) is the creation of a physical part directly from a computer-aided design (CAD) model with minimal process planning and is typically applied to additive manufacturing (AM) processes to fabricate complex geometry. AM is preferred for DDM because of its minimal user input requirements; as a result, users can focus on exploiting other advantages of AM, such as the creation of intricate mechanisms that require no assembly after fabrication. Such assembly free mechanisms can be created using DDM during a single build process. In contrast, subtractive manufacturing (SM) enables the creation of higher strength parts that do not suffer from the material anisotropy inherent in AM. However, process planning for SM is more difficult than it is for AM due to geometric constraints imposed by the machining process; thus, the application of SM to the fabrication of assembly free mechanisms is challenging. This research describes a voxel-based computer-aided manufacturing (CAM) system that enables direct digital subtractive manufacturing (DDSM) of an assembly free mechanism. Process planning for SM involves voxel-by-voxel removal of material in the same way that an AM process consists of layer-by-layer addition of material. The voxelized CAM system minimizes user input by automatically generating toolpaths based on an analysis of accessible material to remove for a certain clearance in the mechanism's assembled state. The DDSM process is validated and compared to AM using case studies of the manufacture of two assembly free ball-in-socket mechanisms.
Experimental Study on Failure Mechanism of Casing Under the Synergy of Temperature and Internal Pressure
Authors: Deng Kuanhai , Lin Yuanhua , Liu Wanying , Zeng Dezhi , Yuan Jiping
Published: August 2017

In recent years, the gas wells with high pressure, high temperature, and high H2S are increasing gradually, but the burst of casing and tubing in these wells will cause the gas channeling and overflow, and the gas with H2S flows up to surface, which causes huge damage. Although the API 5C3 and ISO 10400 standards have presented the prediction model of minimum internal pressure yield strength (IPYS) and burst strength for the casing and tubing in the process of strength design, the effect of temperature on the internal pressure strength is not considered completely. It is well known that it is extremely important to understand the failure mechanism of casing and tubing under the synergy of temperature and internal pressure. Hence, the full-scale internal pressure test is performed for N80 casing under temperature and internal pressure by adopting self-developed experimental equipment, by which the important mechanical parameters (such as minimum IPYS, burst strength, stress-hardening rate, and so on) of casing before and after hardening have been obtained. The impacts of temperature on the internal pressure strength are analyzed based on the comparison of test values with theoretical values given by API 5C3 and ISO 10400 standards. Finally, the failure mechanism and hardening characteristic of N80 casing have been clarified under the synergy of temperature and internal pressure. Research results can provide important references for internal pressure strength design of casing in deep well with high temperature.
Time-Response of Recent Prefilming Airblast Atomization Models in an Oscillating Air Flow Field
Authors: Chaussonnet G. , Müller A. , Holz S. , Koch R. , Bauer H.-J.
Published: August 2017

The present study investigates the response of recent primary breakup models in the presence of an oscillating air flow, and compares them to an experiment realized by Müller and coworkers in 2008. The experiment showed that the oscillating flow field has a significant influence on the Sauter Mean Diameter (SMD) up to a given frequency. This observation highlights the low-pass filter character of the prefilming airblast atomization phenomenon, which also introduces a significant phase shift on the dynamics of SMD of the generated spray. The models are tested in their original formulations without any calibration in order to assess their robustness versus different experiments in terms of SMD and time-response to an oscillating flow field. Special emphasis is put to identify the advantages and weaknesses of theses models, in order to facilitate their future implementation in CFD codes. It is observed that some models need an additional calibration of the time constant in order to match the time shift observed in the experiment, whereas some others show a good agreement with the experiment without any modification. Finally, it is demonstrated that the low-pass filter character of the breakup phenomenon can be retrieved by considering the history of the local gas velocity, instead of the instantaneous velocity. This might result in a higher simulation fidelity within CFD codes.
Efficient Three Dimensional Time-Domain Combustion Noise Simulation of a Premixed Flame Using Acoustic Perturbation Equations and Incompressible LES
Authors: Lackhove Kilian , Sadiki Amsini , Janicka Johannes
Published: August 2017

Combustion noise has become a significant contributor to the overall noise emitted by modern aero-engines. This development is attributed to reduced noise sources in other components due to design improvements and the introduction of premixed combustors that burn more unsteadily and hence emit more noise. These next generation combustion systems are more prone to acoustic instabilities and thus require improved methods for the prediction of combustion noise. This paper presents a numerical approach which exploits the different scales prevalent in these combustion systems by computing the flow field and acoustics separately and coupling both simulations in real time. To demonstrate its capabilities, the methodology is successfully applied to a premixed and pressurized propane flame which was experimentally investigated by CNRS [1] and for which pressure measurement data are available. In the present numerical model, the separation of the physical phenomena facilitates the application of the most suitable numerical schemes and governing equations to both sets of problems. Due to the low Mach numbers governing typical combustors, the flow field can be adequately described by the incompressible Navier-Stokes equations. These are solved by an implicit finite volume flow solver which is supplemented by a tabulated chemistry approach to account for the combustion processes. For the acoustics, the three dimensional Acoustic Perturbation Equations (APE) are solved using a state of the art, low dispersion Discontinuous Galerkin CAA tool. Both codes are run in parallel and exchange fields on-line to maintain the highest possible temporal resolution and data transfer rates. The different natures of both phenomena require an elaborate coupling scheme that comprises temporal and spatial interpolation and filtering. Since the incompressible formulation of the flow solver allows for considerably larger time steps and the acoustics solver employs much simpler governing equations, the overall computational costs of this approach are up to 10 times lower than those of a compressible simulation with similar fidelity.
Transient Power Operation of a Supercritical Carbon Dioxide Brayton Cycle
Authors: Clementoni Eric M. , Cox Timothy L. , King Martha A. , Rahner Kevin D.
Published: August 2017

The Naval Nuclear Laboratory has been operating the Integrated System Test (IST) with the objective of demonstrating the ability to operate and control a supercritical carbon dioxide (sCO2) Brayton power cycle over a wide range of conditions. The IST is a two shaft recuperated closed sCO2 Brayton cycle with a variable speed turbine-driven compressor and a constant speed turbine-driven generator designed to output 100 kWe. This paper presents a thermal-hydraulic lead control strategy for operation of the cycle over a range of operating conditions along with predicted and actual IST system response to power level changes using this control strategy.
Robust Optimization Design of Compressor Blade Considering Machining Error
Authors: Ma Chi , Gao Limin , Cai Yutong , Li Ruiyu
Published: August 2017

The machining error is inevitably produced during the actual manufacturing process of the compressor blade, which leads to the degradation of the aerodynamic performance to some extent. In order to reduce the influence of the machining error, this paper carried out a research on the robust optimization design considering manufacturing error. Scheme of optimization design in this paper is more economical than the scheme of directly increasing the manufacturing precision. The controlled diffused airfoil in the research is parameterized by the application of Non-Uniform Rational B Spline (NURBS) curve. A coordinate measuring machine is used to obtain the distribution of the machining error uncertainty. To ensure the high efficiency of the robust design, the uncertainty quantification is made by using the method of Non-intrusive polynomial chaos (NIPC) expansion. In the key nodes of NIPC, several surrogate models are established based on Latin Hypercube Design (LHD) + Kriging, which further reduces the costs of optimization design. Finally, a new design framework has been established and the optimization design has been made successfully. Under the condition of the machining accuracy unchanged, it reduces the sensitivity of aerodynamic performance to the machining error, and increases its stability.
Gas-Dynamics Design of Reversible Turbine for Marine Gas Turbine Engine
Authors: Niu Xiying , Lin Feng , Li Weishun , Liang Chen , Yu Shunwang , Xu Bo
Published: August 2017

Gas turbine engines are widely used as the marine main power system. However, they can’t reverse like diesel engine. If the reversal is realized, other ways must be adopted, for example, controllable pitch propeller (CPP) and reversible gearing.

Although CPP has widespread use, the actuator installation inside the hub of the propeller lead to the decrease in efficiency, and it takes one minute to switch “full speed ahead” to “full speed astern”. In addition, some devices need to be added for the reversible gearing, and it takes five minutes to switch from “full speed ahead” “to “full speed astern”.

Based on the gas turbine engine itself, a reversible gas turbine engine is proposed, which can rotate positively or reversely. Most important of all, reversible gas turbine engine can realize operating states of “full speed ahead”, “full speed astern“ and “stop propeller”. And, it just takes half of one minute to switch “full speed ahead” to “full speed astern”.

Since reversible gas turbine engines have compensating advantages, and especially in recent years computational fluid dynamics (CFD) technology and turbine gas-dynamics design level develop rapidly, reversible gas turbine engines will be a good direction for ship astern.

In this paper, the power turbine of a marine gas turbine engine was redesigned by three dimensional shape modification, and the flow field is analyzed using CFD, in order to redesign into a reverse turbine. The last stage vanes and blades of this power turbine were changed to double-layer structure. That is, the outer one is reversible turbine, while the inner is the ahead one. Note that their rotational directions are opposite. In order to realize switching between rotation ahead and rotation astern, switching devices were designed, which locate in the duct between the low pressure turbine and power turbine. Moreover, In order to reduce the blade windage loss caused by the reversible turbine during working ahead, baffle plates were used before and after the reversible rotor blades.

This paper mainly studied how to increase the efficiency of the reversible turbine stage, the torque change under different operating conditions, rotational speed and rotational directions, and flow field under typical operating conditions. A perfect profile is expected to provide for reversible power turbine, and it can decrease the blade windage loss, and increase the efficiency of the whole gas turbine engine. Overall, the efficiency of the newly designed reversible turbine is up to 85.7%, and the output power is more than 10 MW, which can meet requirements of no less than 30% power of rated condition. Most importantly, the shaft is not over torque under all ahead and astern conditions. Detailed results about these are presented and discussed in the paper.
Investigation of Lean Combustion Stability, Pressure Drop, and Material Durability in Porous Media Burners
Authors: Sobhani Sadaf , Haley Bret , Bartz Dave , Dunnmon Jared , Sullivan John , Ihme Matthias
Published: August 2017

The operational stability and thermal durability of combustion in two-zone porous media burners (PMBs) is examined experimentally and computationally. Long-term material durability tests at constant and cycled on-off conditions are performed, along with a characterization of combustion stability, pressure drop and pollutant emissions for a range of equivalence ratios, mass flow rates, and burner setups. Experimental thermocouple temperature measurements and pressure drop data are presented and compared to results obtained from one-dimensional volume-averaged simulations. Experimental and model results show good agreement for temperature profiles and pressure drop evaluated using the Darcy-Forchheimer equation with Ergun’s relations. Enhanced flame stability is observed for burners with Yttria-stabilized Zirconia Alumina (YZA) upstream and Silicon Carbide (SiC) in the downstream combustion zone. Measurements of product gas concentrations illustrate highest emissions of CO at conditions close to flash-back and, as expected, higher NOx emissions with increasing equivalence ratios.
Influence of Main Stage Air Splits on the Ignition Performance of TeLESS-II Combustor
Authors: Mi Xiaotong , Zhang Chi , Wang Bo , Lin Yuzhen
Published: August 2017

The centrally staged layout is preferred in the advanced aero-engine combustor to achieve low pollutant emissions as well as stable operation in lean premixed prevaporized combustion. However, because the high-speed main stage airflow prevents the pilot fuel droplets arriving at igniter tip and has a strong convection effect on the initial flame kernel, the application of centrally staged combustor is restricted by its poor ignition and lean blow-out performance. In the centrally staged combustor, the main stage and pilot stage have strong coupled influences on the flow field and fuel distribution. The aim of this paper is to research the impact of the main stage air split on the ignition performance for the baseline case and the comparison case of the main swirler in the TeLESS-II combustor. The main stage air flow rate of the comparison case is about 8 percent less than that of the baseline case. The results of the ignition test at room inlet temperature and pressure indicate that the ignition performance of the comparison case is significantly better than that of the baseline case. The results of the lean blow-out tests show that the main stage air splits do not make the lean blow-out performance worse. To achieve a better understanding of the test results, PLIF technology and CFD analysis were used to measure the fuel distribution and non-reacting flow field. The PLIF and CFD results demonstrate that the most of the fuel spray disperse outward into the main stage cold airflow in the baseline case so that the pilot flame is hard to be established, which leads to poor ignition performance. On the other hand, in the comparison case, the most of the fuel is confined in the recirculation region, which gives a better ignition performance. Compared with the baseline case, the main stage airflow velocity decays faster in the comparison case. It changes the direction of the instantaneous velocity in the spark vicinity, which makes it more likely for the ignition kernel to be captured by the recirculation stream in the comparison case. Therefore, the different fuel distribution and flow field characteristics cause the ignition performance improvement in the comparison case. The improvement is due to the different main stage air flow rates, which is the consequence of the main stage air split.
Predicting Thermoacoustic Instability in an Industrial Gas Turbine Combustor: Combining a Low Order Network Model With Flame LES
Authors: Xia Y. , Morgans A. S. , Jones W. P. , Rogerson J. , Bulat G. , Han X.
Published: August 2017

The thermoacoustic modes of a full scale industrial gas turbine combustor have been predicted numerically. The predictive approach combines low order network modelling of the acoustic waves in a simplified geometry, with a weakly nonlinear flame describing function, obtained from incompressible large eddy simulations of the flame region under upstream forced velocity perturbations, incorporating reduced chemistry mechanisms. Two incompressible solvers, each employing different numbers of reduced chemistry mechanism steps, are used to simulate the turbulent reacting flowfield to predict the flame describing functions. The predictions differ slightly between reduced chemistry approximations, indicating the need for more involved chemistry. These are then incorporated into a low order thermoacoustic solver to predict thermoacoustic modes. For the combustor operating at two different pressures, most thermoacoustic modes are predicted to be stable, in agreement with the experiments. The predicted modal frequencies are in good agreement with the measurements, although some mismatches in the predicted modal growth rates and hence modal stabilities are observed. Overall, these findings lend confidence in this coupled approach for real industrial gas turbine combustors.
The Dynamic Characteristic Analysis of Elastic Ring Squeeze Film Damper by Fluid-Structure Interaction Approach
Authors: Wang ZhenLin , Xu Ning , Yu XiangYu , Liu ZhanSheng , Zhang GuangHui
Published: August 2017

SFD (short for squeeze film damper) is a kind of passive vibration isolator widely used in rotor supporting structures of aero-engines for stabilization and vibration control. However, the conventional SFDs are highly nonlinear in terms of damping coefficient, which lead to complex response such as bitable state. In this paper, numerical simulations are carried out to investigate a new kind of SFD, elastic ring squeeze film damper (ERSFD). The elastic ring is modeled by FEM and the film is analyzed by CFD, the orifices on the ring is also included. An FSI approach is introduced to account for the influence of elastic ring’s deformation on oil film thickness. The Zwart-Gerber-Belamri model is included to account for air ingestion and cavitation in the damper land. The characteristics such as pressure distribution, oil film force and the deformation of the ring are obtained and compared with the results without FSI to reveal the self-adaptive mechanism of film thickness. The force coefficients for ERSFD are derived and gained by the FFT method. The dynamic coefficients for ERSFD versus whirl frequency are obtained and compared with corresponding air volume fraction.
Performance Improvement Program for Kawasaki Gas Turbine
Authors: Taniguchi Tomoki , Tamai Ryoji , Muto Yoshihiko , Takami Satoshi , Tanaka Ryozo , Ryu Masanori
Published: August 2017

Kawasaki Heavy Industries, Ltd (KHI) has started a comprehensive program to further improve performance and availability of existing Kawasaki gas turbines. In the program, one of the Kawasaki’s existing gas turbine was selected from the broad product line and various kinds of technology were investigated and adopted to further improve its thermal performance and availability. The new technologies involve novel film cooling of turbine nozzles, advanced and large-scale numerical simulations, new thermal barrier coating. The thermal performance target is combined cycle efficiency of 51.6% and the target ramp rate is 20% load per minute. The program started in 2015 and engine testing has just started. In this paper, details of the program are described, focusing on design procedure.
Semi-Closed Recuperated Cycle With Wet Compression
Authors: Wettstein Hans E.
Published: August 2017

The semi-closed recuperated cycle (SCRC) has been suggested earlier by the author in several versions. The best of them used two compressors with one intercooling stage each. In this paper the intercooled main compressor has been replaced by a compressor with high fogging and no intercooling anymore. It is assumed that the system and the main compressor have its design points in the middle of the intended fogging water injection range. This turns out to allow another thermal efficiency gain by 2 to 3 percent points to clearly above 60% also combined with increased specific power related to the consumed combustion air and with no bottoming cycle.

This paper demonstrates the technical feasibility based on Turbomachinery technologies, which have already proven commercial viability. The thermodynamic assumptions have been derived from existing gas turbine (GT) technology and are used within already confirmed operating ranges. With the same firing temperature also the thermal efficiency level of current Combined Cycles (GTCC) can be achieved.

A special feature of the SCRC is the opportunity for inventory control of part load operation. This means that part load operation can be made by pressure reduction instead of temperature reduction as in open gas turbines. Thermal transients leading to hot part life consumption can therefore be avoided to a large extent and the combustor can operate at nearly constant temperature also at low part load with corresponding low emissions. Low part load operation achieves the same efficiency as base load. The result is more flexibility than in current GTCC technology associated with less complexity due to the needlessness of an extra bottoming cycle.

Realizing this type of cycle aiming at its best efficiency potential however needs the development capability of a highly skilled gas turbine manufacturer. But it could also be developed for a lower efficiency range by using existing components with conservative data. The SCRC concept could also be aimed at combined heat and power applications or at naval propulsion by replacing CODOG’s.

Due to its specific features the SCRC in general or with wet compression could be developed in the micro turbine power output size as well as up to above 1000MW single block size. Its inherent water condensation at elevated pressure makes an external source of make-up water obsolete.
Effects of Geometry and Spacing in Additively Manufactured Microchannel Pin Fin Arrays
Authors: Ferster Katharine K. , Kirsch Kathryn L. , Thole Karen A.
Published: August 2017

The demand for higher efficiency is ever-present in the gas turbine field and can be achieved through many different approaches. While additively manufactured parts have only recently been introduced into the hot section of a gas turbine engine, the manufacturing technology shows promise for more widespread implementation since the process allows a designer to push the limits on capabilities of traditional machining and potentially impact turbine efficiencies.

Pin fins are conventionally used in turbine airfoils to remove heat from locations in which high thermal and mechanical stresses are present. This study employs the benefits of additive manufacturing to make uniquely shaped pin fins, with the goal of increased performance over conventional cylindrical pin fin arrays. Triangular, star, and spherical shaped pin fins placed in microchannel test coupons were manufactured using Direct Metal Laser Sintering. These coupons were experimentally investigated for pressure loss and heat transfer at a range of Reynolds numbers. Spacing, number of pin fins in the array, and pin fin geometry were variables that changed pressure loss and heat transfer in this study. Results indicate that the additively manufactured triangles and cylinders outperform conventional pin fin arrays, while stars and dimpled spheres did not.
Geometric Model Update of Blisks and its Experimental Validation for a Wide Frequency Range
Authors: Maywald Thomas , Backhaus Thomas , Schrape Sven , Kühhorn Arnold
Published: August 2017

The contribution discusses a model update procedure and its experimental validation in the context of blisk mistuning. Object of investigation is an industrial test blisk of an axial compressor which is milled from solid using a state of the art 5-axis milling machine. First, the blisk geometry is digitized by a blue light fringe projector. Digitization is largely automated using an industrial robot cell in order to guarantee high repeatability of the measurement results. Additionally, frequency mistuning patterns are identified based on vibration measurements. Here, the system excitation is realized by a modal impact hammer. The blade response is detected using a laser scanning vibrometer. Furthermore, all blades except the currently excited one are detuned with additional masses. Applying these masses allows to identify a blade dominated natural frequency for each blade and every mode of interest. Finally, these blade dominated frequencies are summarized to mode specific mistuning patterns. The key part of the contribution presents a model update approach which is focused on small geometric deviations between real engine parts and idealized simulation models. Within this update procedure the nodal coordinates of an initially tuned finite element blisk model were modified in order to match the geometry of the real part measured by blue light fringe projection. All essential pre- and post-processing steps of the mesh morphing procedure are described and illustrated. It could be proven that locally remaining geometric deviations between updated finite element model and the optical measurement results are below 5 μm. For the purpose of validation blade dominated natural frequencies of the updated finite element blisk model are calculated for each sector up to a frequency of 17 kHz. Finally, the numerically predicted mistuning patterns are compared against the experimentally identified counterparts. At this point a very good agreement between experimentally identified and numerically predicted mistuning patterns can be proven across several mode families. Even mistuning patterns of higher modes at about 17 kHz are well predicted by the geometrically mistuned finite element model. Within the last section of the paper, possible uncertainties of the presented model update procedure are analyzed. As a part of the study the digitization of the investigated blisk has been repeated for ten times. These measurement results serve as input for the model update procedure described before. In the context of this investigation ten independent geometrical mistuned simulation models are created and the corresponding mistuning patterns are calculated.
Comparison of a Heat Soakage Model With Turbofan Transient Engine Data
Authors: Vieweg Maximilian , Wolters Florian , Becker Richard-Gregor
Published: August 2017

In the present paper, a transient performance code is employed to predict on-wing test data of the IAE-V2500 engine mounted on an Airbus A320-232. The test data was recorded by the engine control system and may serve as an open basis for validation of future transient studies. For the current investigation, the employed code considers the fundamental equations of the constant mass flow method as well as heat transfer effects by a lumped parameter approach.

The study focuses on seven accelerations and one deceleration. Engine test data was gathered with 10Hz sampling rate, imprinting the applied time step of the model. First, the steady-state matching of the test data was conducted. Subsequently, the measurement quantities fuel flow, inlet temperature and inlet pressure were prescribed as time-varying boundary conditions to the transient model. The results of the standard transient model and the model including thermal effects were compared with temperatures, pressures and shaft speeds. The LPT outlet temperature and the working line excursion in the booster map were examined in detail. The outcome concurs with the original statement that thermal effects are mandatory to enhance model accuracy. Lastly, a sensitivity analysis of the thermal input parameters was accomplished and its influence on model prediction investigated.
Loss Generation in Transonic Turbine Blading
Authors: Duan Penghao , Tan Choon S. , Scribner Andrew , Malandra Anthony
Published: August 2017

The measured loss characteristic in a high-speed cascade tunnel of two turbine blades of different designs showed distinctly different trend with exit Mach number ranging from 0.8 to 1.4. Assessments using steady RANS computation of the flow in the two turbine blades, complemented with control volume analyses and loss modelling, elucidate why the measured loss characteristic looks the way it is. The loss model categorizes the total loss in terms of boundary layer loss, trailing edge loss and shock loss; it yields results in good agreement with the experimental data as well as steady RANS computed results. Thus RANS is an adequate tool for determining the loss variations with exit isentropic Mach number and the loss model serves as an effective tool to interpret both the computational and experimental data. The measured loss plateau in Blade 1 for exit Mach number of 1 to 1.4 is due to a balance between a decrease of blade surface boundary layer loss and an increase in the attendant shock loss with Mach number; this plateau is absent in Blade 2 due to a greater rate in shock loss increase than the corresponding decrease in boundary layer loss. For exit Mach number from 0.85 to 1, the higher loss associated with shock system in Blade 1 is due to the larger divergent angle downstream of the throat than that in Blade 2. However when exit Mach number is between 1.00 and 1.30, Blade 2 has higher shock loss. For exit Mach number above around 1.4, the shock loss for the two blades is similar as the flow downstream of the throat is completely supersonic. In the transonic to supersonic flow regime, the turbine design can be tailored to yield a shock pattern the loss of which can be mitigated in near equal amount of that from the boundary layer with increasing exit Mach number, hence yielding a loss plateau in transonic-supersonic regime.
Design of a Bimetallic Blisk Turbine for a Gas Turbine Engine and its Production Using Powder Metallurgy Methods
Authors: Magerramova Liubov , Vasilyev Boris , Nigmatullin Ravil , Kinzburskiy Vladimir
Published: August 2017

One key engine component that defines the main engine characteristics is the wheel of a high-pressure turbine. One reasonable approach for increasing the efficiency of this type of turbine is to use blade shrouding. However, this shrouding also increases the centrifugal loading on the profile part of the blades, the lock connection, and the disk. One solution to this issue is to eliminate the lock connections, i.e. to create wheels of a blisk-type design.

The bimetallic blisk was developed based on a wheel that has a lock connection for the disk and blades without shrouds. This study presents a redesign of the profile parts of the blades using computational fluid dynamics calculations, and a reintroduction of shrouds to the blade design. Connection of the blades to the disc involved a newly developed process based on powder metallurgy. The result is a bimetallic blisk consisting of single-crystal blades with shrouds and a disk consisting of a granulated heat-resistant nickel base alloy, connected by hot isostatic pressing. This bimetallic blisk satisfies the strength requirements and is detuned from the resonant frequencies. The weight is 7% lower for the developed design than for the prototype, and the turbine efficiency is increased by 2%.
Prediction of Heat Transfer for a Highly Loaded Transonic Turbine Guide Vane With the Usage of a GPU Based 3D RANS Solver
Authors: Sembritzky Marwick , Micallef Derek , Engelmann David
Published: August 2017

A GPU based 3D RANS multi-block slover with the capability of predicting heat transfer in fully resolved boundary layer flows based on the turbomachinery CFD code TBLOCK has been developed. A diabatic wall treatment and the scalar dissipation scheme have been integrated. The standard one-equation Spalart-Allmaras turbulence model with trip term is used for turbulence modeling. For validation, steady CFD results from the developed GPU version of TBLOCK are compared to a well-documented experiment of a highly loaded turbine cascade. The experiment covers a range of different Mach numbers and Reynolds numbers with static pressure and heat flux distributions on suction and pressure side of the blade. The predicted pressure and heat flux distribution show good agreement to the experimental data. A significant reduction of calculation time could be achieved compared to the authors’ CPU based MPI version of TBLOCK.
Smoothed Particle Hydrodynamics Simulation of Oil-Jet Gear Interaction
Authors: Keller Marc C. , Braun Samuel , Wieth Lars , Chaussonnet Geoffroy , Dauch Thilo F. , Koch Rainer , Schwitzke Corina , Bauer Hans-Jörg
Published: August 2017

In this paper the complex two-phase flow during oil-jet impingement on a rotating spur gear is investigated using the meshless Smoothed Particle Hydrodynamics (SPH) method. A comparison of single-phase SPH to multi-phase SPH simulation and the application of the Volume of Fluid method on the basis of a two-dimensional setup is drawn. The results of the different approaches are compared regarding the predicted flow phenomenology and computational effort. It is shown that the application of single-phase SPH is justified and that this approach is superior in computational time, enabling faster simulations. In a next step, a three-dimensional single-phase SPH setup is exploited to predict the flow phenomena during the impingement of an oil-jet on a spur gear for various jet inclination angles. Thereby, a significant effect of the inclination angle on the oil spreading and splashing process is revealed. Finally, a qualitative comparison to an experimental high-speed image shows good accordance.