bluuebunny/crossref_metadata_2025 huggingface dataset:
A review of clinical manifestations in adolescent and young adults after use of synthetic cannabinoids
Authors: Brewer Tracy L. , Collins Margie
Published: December 2013

Purpose

The purpose of this review is to heighten the awareness of the increased use and risks of synthetic cannabinoids (SCs) and associated clinical manifestations among adolescents and young adults.

Conclusions

Reviewed case studies suggest that the use of SCs have unpredictable negative psychological and physiological effects. Predominant manifestations reported were anxiety, agitation, paranoia, hallucinations, tachycardia, nausea and vomiting, and diaphoresis.

Practice Implications

Nurses provide the most direct and supportive care to patients who present for medical treatment after the use of SCs. Knowledge of clinical manifestations can facilitate supportive management of patients suspected of SCs use.
Rapid evolution of an invasive weed
Authors: Turner Kathryn G. , Hufbauer Ruth A. , Rieseberg Loren H.
Published: December 2013

Trade‐offs between performance and the ability to tolerate abiotic and biotic stress have been suggested to explain both the success of invasive species and phenotypic differentiation between native and invasive populations. It is critical to sample broadly across both ranges and to account for latitudinal clines and maternal effects when testing this premise.

Wild‐collected Centaurea diffusa seeds were grown in benign and stressful conditions (drought, flooding, nutrient stress and simulated herbivory), to evaluate whether native and introduced individuals differ in performance or life history phenotypes. A second experiment used glasshouse‐grown seeds to evaluate whether patterns remain comparable when maternal environment is consistent.

Many traits differed between ranges, and in all cases but one, invasive individuals grew larger, performed better, or matured later. No trade‐off in performance with herbivore defense was evident. Invasive populations may have been released from a trade‐off between growth and drought tolerance apparent in the native range.

Larger individuals with delayed maturity and greater reproductive potential have evolved in invasive populations, a pattern evident across broad population sampling, and after latitude and maternal environment were considered. Release from abiotic stress tolerance trade‐offs may be important for the invasion success of Centaurea diffusa.
The molecular basis for the development of neural maps
Authors: Wei Yi , Tsigankov Dmitry , Koulakov Alexei
Published: December 2013

Neural development leads to the establishment of precise connectivity in the nervous system. By contrasting the information capacities of cortical connectivity and the genome, we suggest that simplifying rules are necessary in order to create cortical connections from the limited set of instructions contained in the genome. One of these rules may be employed by the visual system, where connections are formed on the basis of the interplay of molecular gradients and activity‐dependent synaptic plasticity. We show how a simple model that accounts for such interplay can create both neural topographic maps and more complex patterns of ocular dominance, that is, the segregated binary mixture of projections from two eyes converging in the same visual area. With regard to the ocular dominance patterns, we show that pattern orientation may be instructed by the direction of the gradients of molecular labels. We also show that the periodicity of ocular dominance patterns may result from the interplay of the effects of molecular gradients and correlated neural activity. Overall, we propose that simple mechanisms can account for the formation of apparently complex features of neuronal connections.
A juvenile turtle (Testudines, Eucryptodira) from the Upper Jurassic of Langenberg Quarry, Oker, Northern Germany
Authors: Jansen Maren , Klein Nicole
Published: December 2013

Turtles are frequently found in fluviatile to lagoonal and shallow marine sediments in the Upper Jurassic of Western Europe. These turtles usually show a mixture of basal and derived characters, but phylogenetic relationships are still largely unresolved. This is mainly due to the incompleteness of fossils and the lack of taxonomically unambiguous characters and is also related to the presence of different ontogenetic stages, which are not easy to compare. The morphological description of a new turtle from the Upper Jurassic of Langenberg Quarry (Oker, Lower Saxony, Germany) gives further insights into the ontogeny of basal eucryptodire turtles as well as into aquatic adaptation of Upper Jurassic turtles. The specimen is herein left in open nomenclature, due to the fact that it represents a juvenile individual. Several characters define the specimen as juvenile: its small size (7.28 cm carapace length); lateral carapacial fontanelles; enlarged vertebral scutes; a radial striation pattern covering the entire carapace; and the grade of ossification of preserved skull and limb elements. A clear aquatic adaptation of the individual is the elongated manus, a feature that is independent of ontogenetic age. The elongated manus may indicate a marine lifestyle and the individual possibly inhabited nearshore to offshore areas around the former Jurassic islands, which today form the Saxony Basin. The ossification pattern of the carapace of this eucryptodire turtle resembles that of known Jurassic paracryptodires and thus provides new insights to the ontogeny of Jurassic turtles.
Characterization of the Triplet State of Tanshinone IIA and its Reactivity by Laser Flash Photolysis
Authors: Li Kun , Zhang Qin , Wang Mei , Zhu Rongrong , Sun Xiaoyu , Wu Xianzheng , Wang Shi‐Long
Published: December 2013

Tanshinone IIA (Tan IIA) has the properties of cardiovascular protection, anti‐inflammation, antioxidation and anticancer. Its light‐induced instability has drawn our interests in its photochemistry. Therefore, laser flash photolysis herein was used to investigate the transient photochemistry of Tan IIA. Our results show that direct photoexcitation by 355 nm laser pulses or photosensitization by energy transfer can lead to the formation of the triplet state of Tan IIA (3Tan IIA*). The triplet absorption spectrum and molar absorption coefficient, and ISC quantum yield were determined. Self‐quenching of 3Tan IIA* by its ground state was identified as an autooxidation reaction. 3Tan IIA* was proved to react quickly with N, N‐dimethylaniline, tert‐butylhydroquinone and propyl gallate via electron transfer with the diffusion‐controlled rate constants. One of the products with maximum absorption around 390 nm was assigned to the radical anion of Tan IIA. Our results indicate that 3Tan IIA* is a reactive transient species and can be generated by photosensitization or direct photoexcitation. According to our results, the possible role of Tan IIA as a photosensitizer to induce potential phototoxicity via Type‐II pathway in the presence of O2 can be predicted.
Modifiable risk factors in periodontal disease
Authors: Barros Silvana P. , Offenbacher Steven
Published: December 2013

Epigenetics as a modifiable risk factor in periodontal diseases has been investigated in light of the current knowledge of how chronic infection and inflammation can affect gene‐specific epigenetic reprogramming in periodontal tissues. Epigenomic programming might be particularly sensitive to environmental influences, and a combination of physiological stressors and environmental exposures appears to affect the epigenomic program acquired by a cell during differentiation and throughout the cellular lineage lifespan. Viral and bacterial infections can establish several types of epigenetic modifications, which sometimes engage in a complex epigenetic crosstalk also reflecting in the establishment and progress of periodontal diseases. The inflammatory and metabolic states of the periodontal tissues are driven by the infectious stimuli, and the magnitude of the cellular and molecular signature response is further dictated by the host genetic and epigenetic traits associated with various systemic exposures, including smoking, obesity and diabetes/hyperglycemia. This review discusses the advances in epigenetics, focusing on the role of DNA methylation in the pathogenesis of periodontal disease and the potential of epigenetic therapy.
Modifiable risk factors in periodontitis: at the intersection of aging and disease
Authors: Reynolds Mark A.
Published: December 2013

Chronic inflammation is a prominent feature of aging and of common age‐related diseases, including atherosclerosis, cancer and periodontitis. This volume examines modifiable risk factors for periodontitis and other chronic inflammatory diseases. Oral bacterial communities and viral infections, particularly with cytomegalovirus and other herpesviruses, elicit distinct immune responses and are central in the initiation of periodontal diseases. Risk of disease is dynamic and changes in response to complex interactions of genetic, environmental and stochastic factors over the lifespan. Many modifiable risk factors, such as smoking and excess caloric intake, contribute to increases in systemic markers of inflammation and can modify gene regulation through a variety of biologic mechanisms (e.g. epigenetic modifications). Periodontitis and other common chronic inflammatory diseases share multiple modifiable risk factors, such as tobacco smoking, psychological stress and depression, alcohol consumption, obesity, diabetes, metabolic syndrome and osteoporosis. Interventions that target modifiable risk factors have the potential to improve risk profiles for periodontitis as well as for other common chronic diseases.
Do Blood Pressure Levels and Other Patient Characteristics Influence Native Fistula Patency?
Authors: Irvinn Jeyna , Oldman Nicola , Sedgwick Philip , Chemla Eric
Published: December 2013

Arteriovenous fistulas (AVFs) play an important role in access for hemodialysis, yet premature thrombosis is a challenge. This study identifies factors influencing primary patency in a series of AVF creations. Postoperative systolic blood pressure (BP) was of principal interest; demographical information, comorbidities, smoking status, warfarin, aspirin, clopidogrel, and statins were considered.

A retrospective review of AVF creations performed by one surgeon between January 2008 and September 2010 was conducted. Fistula patency was denoted by a bruit and measured at 3 weeks and 12 months after surgery.

One hundred and fifty‐one AVF creations were studied; 134 fistulas (88.7%) were patent at 3 weeks and 85 (56.3%) at 12 months. The odds ratio (OR) for thrombosis at 12 months was 0.16 (95% CI: 0.04, 0.62; p = 0.008) among patients with a postoperative systolic BP of 120–139 mmHg compared with those with a BP of ≤119 mmHg. Patients taking warfarin yielded an OR of 5.71 at 3 weeks (95% CI: 1.20, 27.11; p = 0.028), and 3.33 at 12 months (95% CI: 1.01, 10.99; p = 0.048). No other variables were statistically significant.

Patients with postoperative systolic BP of 120–139 mmHg showed a reduction in fistula thromboses compared with patients with a systolic BP of ≤119 mmHg. Patients on warfarin were less likely to maintain a patent fistula.
Outcomes of Single‐Stage Compared to Two‐Stage Basilic Vein Transposition Fistulae
Authors: Agarwal Amol , Mantell Mark , Cohen Raphael , Yan Yan , Trerotola Scott , Clark Timothy W
Published: December 2013

Basilic vein transposition (BVT) fistulae are increasing in prevalence in the United States. We examined outcomes of BVT fistulae created in a single stage compared to those created in two stages. Prospective QA databases identified a consecutive cohort of 144 patients with BVT fistulae. Of these, 42% were created in one stage and 58% in two stages. Fistula maturation rates, mean time to fistula use and intensity of percutaneous interventions were compared; patency rates were compared from time of first intervention. Maturation rates (including assisted maturation) were 90% among 1‐stage and 75% among 2‐stage BVT (p = 0.02). Mean time to initiation of fistula use was 142 days (1‐stage) and 146 days (2‐stage) (p = 0.92). Intensity of percutaneous interventions was 1.84/patient‐year of dialysis (PYD) (1‐stage) and 2.15/PYD (2‐stage) (p = 0.57). Secondary patency at 1, 2, 3, and 4 years for 1‐stage BVT was 86%, 75%, 69%, and 57%; secondary patency at 1, 2, 3, and 4 years for 2‐stage BVT was 76%, 71%, 49%, and 25%, respectively (p = 0.12). BVT creation in two stages confers only a modest reduction in maturation rates and secondary patency and therefore should be considered over a synthetic graft in patients with basilic veins deemed inadequate for 1‐stage BVT.
Setting Up a Useful Gas Cooler Equation and its Performance Tests
Authors: Bainier Francis , Belgodère Rémy , Routhieau Vincent , Pillay Tony
Published: December 2013

The purpose of this paper is to determine an equation enabling the calculation of the temperature at the exit of a gas cooler, knowing the input temperature, the flow rate, the pressure, the gas composition, the temperature of the heat transfer fluid as well as the heat transfer coefficient of the gas cooler and its transfer surface with the constrain to be easily applied and to give acceptable results.

This research has been initiated by compressor engineers and experts in charge of checking the compressor installations.

This paper consists of 3 parts.

• Determining the equation:

This section sets out the equations of continuity, momentum and energy applied to a gas particle flowing within a pipe, by using some assumptions. The most important assumption allows us to consider the gas particle as a very thin disk with the same diameter as the “equivalent tube” of the gas cooler and of which the normal is parallel to the axis of the tube. This gas particle therefore has two faces perpendicular to the gas flow. At the end of the demonstration, the gas cooler could be described in a equation where the inputs are the temperature of the gas entering the gas cooler, the outside temperature of the system considered to be that of the heat transfer fluid of the gas cooler, the total transfer surface of the gas cooler, the average molar heat capacity at constant pressure of the gas, the molar mass of the gas, the mass flow rate, the heat transfer coefficient of the gas cooler; and at the end, a fouling factor is introduced to achieve the purpose of this paper.

• Numerical application:

In this section, the global heat transfer coefficient of a gas cooler is determined. Knowing this value, The error between temperature T2 established by the provider of the equipment at the exit of the gas cooler and temperature T2calc calculated according to the proposed formula in this paper is determined. The error margin is systematically less than ±0.5 °C.

• Field tests:

Field tests using this method showed:

- the tested gas cooler does not meet the specified requirements,

- the accuracy of the method applied in field tests is 98%,

- the method is very easy to apply on site and gives acceptable results.
Computing Gas Turbine Fuel Consumption to Firm Up Wind Power
Authors: Branchini L. , Perez-Blanco H.
Published: December 2013

As wind power installed capacities increase, it is necessary to deal with the inevitable variability of renewables. Some of that variability can undoubtedly be predicted, but some will in all probability remain unpredictable. In either case, reserve power must be made available. It is clear that the ramp rates that the reserve power must meet will stress technology and call for part-load operation at reduced efficiencies. In the present work, we use a gas turbine (GT) dynamic models to simulate the provision of firm power in the Pennsylvania, New Jersey and Maryland grid, PJM. Rowen GT models [1, 2], well established in the literature, are modified to take into account GT ramp rates constrains and fuel consumption at full and partial load, as well as during startup and shutdown. The GTs operational requirements for two summer days in the PJM area are determined, by selecting their number and capacities to result on at least a few units operating at full load. The dynamic models [1, 2] are implemented in the VisSim simulation environment. The results of the work show how the chosen GTs must be operated to provide firm power. Although the operational strategy determined in this paper meets the firm power, in two occasions during the day excess power is produced during a few minutes, to avoid ramping the units down too fast.
Investigations on Maximum Amplitude Amplification Factor of Real Mistuned Bladed Structures
Authors: Hemberger David , Filsinger Dietmar , Bauer Hans-Jörg
Published: December 2013

The production of bladed structures, e.g. turbine and compressor wheels, is a subject of statistical scatter. The blades are designed to be identical but differ due to small manufacturing tolerances. This can be local variance of material properties and geometrical deviations, which is indicated as mistuning of the structure. This article deals with the amplitude amplification factor of bladed structures caused by mistuning of real geometries.

Theoretical investigations and also experimental results show, that mistuning of the structure leads to an amplification of blade vibration amplitudes and hence to increased stresses in blades. The existing theoretical considerations by Whitehead from 1966 and Kenyon & Griffin from 2001 are compared with results of blade vibration measurements. For that purpose, measurement results of turbine and compressor wheels from publication in recent years were analyzed. These experimental results stem from measurements with strain gauges as well as tip timing measurements to determine blade vibration amplitudes. In addition to this extended literature survey, the authors also examined results from in-house tip timing measurements of a radial turbine wheel from a vehicular turbocharger.

The maximum amplification factor (MAF) and the degree of localization were evaluated. The comparison with the theory by Kenyon & Griffith revealed that the estimated maximum amplification factor was always higher than the values from the analyzed data. The measured MAF were besides one exception of a highly localized vibration form, which does not meet the theory’s assumptions, between 54% and 99.5% of the expected value. In this sense the theory has been proven.
Effect of Material Damping of Steam Turbine Vane on Flutter Suppression
Authors: Kaneko Yasutomo , Mori Kazushi , Ohyama Hiroharu
Published: December 2013

The vane used in a low pressure end of steam turbine is usually fixed to shroud and casing by welding both ends. In such a vane structure, the damping in loading operation is comprised of the material damping and the aerodynamic damping, because the structural damping is very small. In this paper, first, the vane is modeled by the uniform beam fixed at both ends, and the effect of the material damping on the vane flutter is studied. In the stability analysis, the simple one-degree-of-freedom model is applied, where the linear aerodynamic model is used. In other words, it is assumed that the aerodynamic force due to the working fluid is proportional to the vane velocity and the negative damping coefficient does not change with amplitude. The allowable aerodynamic damping for the vane flutter is calculated and compared for the solid vane and the hollow vane. In addition, the vibration analysis of the actual steam turbine vane is carried out by 3D FEA (Finite Element Analysis), and the material damping of the solid and hollow vane is calculated by use of the results by FEA. The stability of the solid vane and the hollow vane on the flutter is also evaluated by use of the results calculated by FEA. From these results, the material damping characteristics of the steam turbine vane are clarified, as well as the effect of the material damping of the steam turbine vane on the flutter suppression.
High-Cycle Fatigue of Fan Blades Accounting for Fluid-Structure Interaction
Authors: Dhopade Priyanka , Neely Andrew J. , Young John , Shankar Krishna
Published: December 2013

Gas turbine engine components are subject to both low-cycle fatigue (LCF) and high-cycle fatigue (HCF) loads. To improve engine reliability, durability, and maintainability, it is necessary to understand the interaction of LCF and HCF in these components, which can adversely affect the overall life of the engine. The LCF loads result from the aircraft flight profile and are typically high stress, nominally rotational and aerodynamic loads. HCF loads are a consequence of high frequency vibrations, such as the fluctuating loads on blades as they rotate through the wakes from the upstream stator vanes. This paper demonstrates the importance of a fully coupled FSI analysis in conjunction with a fatigue analysis to predict the effect of representative fluctuating loads on the fatigue life of blisk fan blades. The fully-coupled FSI analysis is compared to the partially coupled FSI analysis and it is found that the former better predicts the the structural response of the titanium alloy blade to the wake impingement from the upstream stator. This results in a non-linear stress history compared to the linear response of the partially coupled system which also under-predicts the peak stress by 24%. The fatigue analysis shows the blade will fail near the root with a maximum damage of 1.079(10−17) using Miner’s rule to calculate cumulative damage. The implications of this research can influence future experimental studies that aim to generate meaningful fatigue data, which will assist in the management of safe operation of gas turbines.
Simulation of Non-Synchronous Blade Vibration of an Axial Compressor Using a Fully Coupled Fluid/Structure Interaction
Authors: Im Hong-Sik , Zha Ge-Cheng
Published: December 2013

In this paper non-synchronous vibration (NSV) of a GE axial compressor is simulated using a fully coupled fluid/strcuture interaction (FSI). Time accurate Navier-Stokes equations are solved with a system of 5 decoupled structure modal equations in a fully coupled manner. A 3rd order WENO scheme for the inviscid flux and a 2nd order central differencing for the viscous terms are used to resolve nonlinear interaction between vibrating blades and fluid flow. 1/7th annulus is used with a time shifted phase-lag (TSPL) boundary condition to reduce computational efforts. A fully conservative rotor/stator sliding boundary condition is employed to accurately capture unsteady wake propagation between the rotor and stator blades. The predicted dominant frequencies using the blade tip response signals are not harmonic to the engine order, which is the NSV. The blade vibration is torsionally coupled with highly oscillating blade pressure and is not damped out during the NSV. No resonance to the blade natural frequencies is found. The instability of tornado vortices in the vicinity of the rotor tip due to the strong interaction of incoming flow, tip vortex and tip leakage flow is the main cause of the NSV observed in this study.
Load Rejection Tests and Their Dynamic Simulations With a 150 kW Class Microsteam Turbine
Authors: Nakano Susumu , Tsubouchi Kuniyoshi , Shiraiwa Hiroyuki , Hayashi Kazutaka , Yamada Hiroyuki
Published: December 2013

Simulation method for load rejection with a 150 kW class radial inflow steam turbine system was proposed to determine over rotational speed at load rejection. Simulations were carried out for several parameters of valves which are operated in an emergency. And load rejection tests were carried out to confirm the machine reliability and to obtain results for comparison with the simulation results. Simulation results show that operation delay times of the steam release and vacuum break valves greatly affect over rotational speed at load rejection. Load rejection tests were done for generator outputs from 69 kW to 113 kW. Maximum over rotational speed of 54,160 rpm was measured at the generator output of 113 kW. Over rotational speed calculated by the dynamic simulation has relatively good agreement with the result for the operation delay time of 0.21 s. If the operation delay time of the steam release valves are kept as 0.21 s at the load rejection for the rated load of 150 kW, the over rotational speed is suppressed within 55,200 rpm which is less than the allowed rotational speed of 56,100 rpm.
On the Simplifications for the Thermal Modeling of Tilting-Pad Journal Bearings Under Thermoelastohydrodynamic Regime
Authors: Cerda Varela Alejandro , Fillon Michel , Santos Ilmar Ferreira
Published: December 2013

The relevance of calculating accurately the oil film temperature build up when modeling tilting-pad journal bearings is well established within the literature on the subject. This work studies the feasibility of using a thermal model for the tilting-pad journal bearing which includes a simplified formulation for inclusion of the heat transfer effects between oil film and pad surface. Such simplified approach becomes necessary when modeling the behavior of tilting-pad journal bearings operating on controllable lubrication regime. Three different simplified heat transfer models are tested, by comparing their results against the ones obtained from an state of the art tilting-pad journal bearing model, where the heat transfer effects are throughly implemented, as well as against some experimental results from the literature. The results obtained show that the validity of the simplified heat transfer models are strongly dependent on the Reynolds number for the oil flow in the bearing. For bearings operating in laminar regime, the decoupling of the oil film energy equation solving procedure, with no heat transfer terms included, with the pad heat conduction problem, where the oil film temperature is applied at the boundary as a Dirichlet condition, showed a good balance between quality of the results, implementation easiness and reduction in calculation time. For bearings on the upper limit of the laminar regime, the calculation of an approximated oil film temperature gradient in the radial direction, as proposed by Knight and Barrett, delivered the best results.
Management of Gas Turbine Performance in GRTgaz Gas Network in France
Authors: Bainier Francis , Belgodère Rémy , Routhieau Vincent , Pillay Tony , Kurz Rainer
Published: December 2013

This paper explains how to obtain and manage reliable information on current and planned performance of turbines by using an appropriate method for planning and controlling turbine degradation. In this paper a useful calculation method is described to manage the performance of gas turbine driven centrifugal compressors. The method is based on the knowledge of its current performance of installations and their degradation.

The paper consists of 4 parts:

– general information about turbine fouling and deterioration,

– calculation methods,

– measurements influences,

– field results.
On the Effect of Thermal Energy Transport to the Performance of (Semi)Floating Ring Bearing Systems for Automotive Turbochargers
Authors: San Andrés Luis , Barbarie Vince , Bhattacharya Avijit , Gjika Kostandin
Published: December 2013

Bearing systems in engine-oil lubricated turbochargers (TCs) must operate reliably over a wide range of shaft speeds and withstanding severe axial and radial thermal gradients. An engineered thermal management of the energy flows into and out of the bearing system is paramount to ensure the components mechanical integrity and the robustness of the bearing system. The bearings, radial and thrust type, act both as a load bearing and low friction support with the lubricant carrying away a large fraction of the thermal energy generated by rotational drag and the heat flow disposed from a hot shaft. The paper introduces a thermohydrodynamic analysis for prediction of the pressure and temperature fields in a (semi) floating ring bearing system. The analysis solves simultaneously the Reynolds equation with variable oil viscosity and the thermal energy transport equation in the inner and outer films of the bearing system. Flow conditions in both films are coupled to the temperature distribution and heat flow thru the (semi)floating ring. Other constraints include calculating the fluid films’ forces reacting to the externally applied load and to determine the operating journal and ring eccentricities. Predictions of performance for a unique realistic (S)FRB configuration at typical TC operating conditions reveal distinct knowledge: (a) the heat flow from the shaft into the inner film is overwhelming, in particular at the inlet lubricant plane where the temperature difference with the cold oil is largest; (b) the inner film temperature increases quickly as soon as the (cold) lubricant enters the film and due to the large amount of energy generated by shear drag and the heat transfer from the shaft; (c) a floating ring develops a significant radial temperature gradient; (d) at all shaft speeds, low and high, the thermal energy carried away by the lubricant streams is no less that 70% of the total energy input; the rest is conducted through the TC casing. To warrant this thermal energy distribution, enough lubricant flow must be supplied to the bearing system. The efficient computational model offers a distinct advantage over existing lumped parameters thermal models and with no penalty in execution time.
Life Prediction and Metallographical Examination of SAGBO Cracking in RB211 High Pressure Turbine Blades
Authors: Kibsey Mitch , Huang Xiao , Koul Ashok , Hildebrand Michael
Published: December 2013

In a previous study, high pressure turbine blades from an RB211-24C aero-derivative industrial gas turbine engine were sectioned and metallographically examined. The turbine blades were made of cast Mar-M002, a nickel-based superalloy. It was found that stress-assisted grain boundary oxidation (SAGBO) had occurred along the inner cooling channels near the leading edge at the turbine blade root, which accelerated crack formation and propagation through dynamic embrittlement. The cracks were characterized by the presence of large Hf, Al and O concentration. It appeared that the presence of oxygen in the inner cooling channels and the rapid oxidation of hafnium carbides aggravated the onset of failure through the action of SAGBO cracking. Following this examination, a creep life prediction analysis of the RB211-24C first stage blades was performed at Life Prediction Technologies Inc. (LPTi). According to the results from LPTi’s creep life prediction, the leading edge region near the blade root is most vulnerable to combined creep and oxidation damage accumulation due to high strain accumulation, as a result of high temperatures, stress, and limited inspection ability of the inner channels. In the present study, the LPTi prediction results are compared with the metallographic analysis of RB211-24C blades. It is confirmed that SAGBO in combination with creep leads to cracking in the predicted region and the worst case creep analysis results match favorably with the field experience.
Performance Evaluation of a Turbine Used in a Regenerative Organic Rankine Cycle
Authors: Li Maoqing , Wang Jiangfeng , Gao Lin , Niu Xiaoqiang , Dai Yiping
Published: December 2013

Due to environmental constraints, the Organic Rankine Cycle (ORC) is widely used to generate electricity from low grade heat sources. In ORC processes, the working fluid is an organic substance, which has a better thermodynamic performance than water for low grade heat recovery. The design of the turbine which is the key component in the ORC system strongly depends on the operating conditions and on the scale of the facility. This paper presents an experimental study on a prototype of an axial-flow turbine integrated into a regenerative ORC system with R123 as working fluid. The power output is 10kW scale, and the single-stage turbine is selected. The turbine is specially designed and manufactured, and a generator is connected to the turbine directly. In the experiment, the turbine is tested under different inlet pressure conditions (0.6–1.5MPa), different inlet temperature conditions (80–150°C) and different flow rate conditions. The experimental data such as the pressures, temperatures of the turbine inlet and outlet, flow rate, rotational speed, and electrical power generation are analyzed to find their inner relationships. During the test, the turbine rotational speed could reach more than 3010 r/min, while the design rotational speed is 3000 r/min. The isentropic efficiency of the turbine could reach 53%. The maximum electrical power generated by the turbine-generator is 6.57KW. From the test data the peak value of the temperature difference between the inlet and the outlet of the turbine is 53 °C, and the expansion ratio reaches about 11. The computational fluid dynamics (CFD) solvers is also used to analyze the performance of the turbine. The distributions of the pressure, Mach number, and static entropy in the turbine flow passage component are examined and the reasons are also obtained. This study reveals the relationships between the performance of the axial-flow turbine and its inlet and outlet vapor conditions. The experiment results and the CFD results lay a foundation for using this type turbine in the ORC systems which product electrical power from a few KW to MW.
Advancement of Experimental Methods and Cailletaud Material Model for Life Prediction of Gas Turbine Blades Exposed to Combined Cycle Fatigue
Authors: Thiele Marcus , Weser Swen , Gampe Uwe , Parchem Roland , Forest Samuel
Published: December 2013

The European project PREMECCY has been conducted to enhance predictive methods for combined cycle fatigue (CCF) of gas turbine blades, i.e. interaction of low cycle fatigue (LCF) and high cycle fatigue (HCF). While design of CCF feature tests, comprising specimen and test rig design, has already been reported, this paper presents experimental HCF/ CCF test results and progress in life prediction.

Besides standard lab specimen tests for characterization of single crystal and conventional cast material, also advanced specimens representing critical rotor blade features were tested in a hot gas rig.

Based on these experimental data an extended Cailletaud material model for stress-strain analysis has been calibrated and combined with a modified ONERA damage model for creep-fatigue interaction to estimate the lifetime of the advanced test specimens.

The model extensions address the effect of ratcheting, which is typical for CMSX-4 at asymmetric cyclic loading at elevated temperature. Caused by limitations of the Armstrong-Frederick kinematic hardening rule regarding ratcheting, three models for improved ratcheting simulation of isotropic material were adopted to anisotropic material. In addition multiple Norton-flow rules for the viscous part of the model are combined with time recovery terms in the kinematic hardening evolution to represent the behaviour of single crystal material in high temperature environment at a wide range of strain rates. Hence, an improved model for stress-strain and lifetime prediction for single crystals has been developed.
Scaling Considerations for a Multi-Megawatt Class Supercritical CO2 Brayton Cycle and Path Forward for Commercialization
Authors: Fleming Darryn , Holschuh Thomas , Conboy Tom , Rochau Gary , Fuller Robert
Published: December 2013

Small-scale supercritical CO2 demonstration loops are successful at identifying the important technical issues that one must face in order to scale up to larger power levels. The Sandia National Laboratories (Sandia) Supercritical CO2 Brayton cycle test loops are identifying technical needs to scale the technology to commercial power levels such as 10 MWe. The small demonstration loops provide a scalable approach to identify cost, technical hurdles, and future commercialization plans of commercial applications.

The small size of the Sandia 1 MWth loop has demonstration of the split flow loop efficiency and effectiveness of the Printed Circuit Heat Exchangers (PCHEs) leading to the design of a fully recuperated, split flow, supercritical CO2 Brayton cycle demonstration system. However there were many problems that were encountered such as; the high rotational speeds in these units identified the need to address bearing, seals, thermal boundaries, and motor controller problems to prove a reliable power source in the 300 kWe range. Although these issues were anticipated in smaller demonstration units, we also understood that commercially scaled hardware would eliminate these problems caused by high rotational speeds at small scale.

The economic viability and development of the future scalable 10 MWe solely depends on the interest of DOE and private industry. The Intellectual Property collected by Sandia proves that the ∼10 MWe Supercritical CO2 power conversion loop to be very beneficial when coupled to a 20 MWth heat source (either solar, geothermal, fossil, or nuclear). This paper will identify a commercialization plan, as well as, a roadmap from the simple 1 MWth supercritical CO2 development loop to a power producing 10 MWe supercritical CO2 Brayton loop.
Parameterization of High Solar Share Gas Turbine Systems
Authors: Heide Stephan , Felsmann Christian , Gampe Uwe , Boje Sven , Gericke Bernd , Freimark Manfred , Langnickel Ulrich , Buck Reiner , Giuliano Stefano
Published: December 2013

Existing solar thermal power plants are based on steam turbine cycles. While their process temperature is limited, solar gas turbine (GT) systems provide the opportunity to utilize solar heat at a much higher temperature. Therefore there is potential to improve the efficiency of future solar thermal power plants.

Solar based heat input to substitute fuel requires specific GT features. Currently the portfolio of available GTs with these features is restricted. Only small capacity research plants are in service or in planning. Process layout and technology studies for high solar share GT systems have been carried out and have already been reported by the authors. While these investigations are based on a commercial 10MW class GT, this paper addresses the parameterization of high solar share GT systems and is not restricted to any type of commercial GT.

Three configurations of solar hybrid GT cycles are analyzed. Besides recuperated and simple GT with bottoming Organic Rankine Cycle (ORC), a conventional combined cycle is considered.

The study addresses the GT parameterization. Therefore parametric process models are used for simulation. Maximum electrical efficiency and associated optimum compressor pressure ratio πC are derived at design conditions. The pressure losses of the additional solar components of solar hybrid GTs have a different adversely effect on the investigated systems. Further aspects like high ambient temperature, availability of water and influence of compressor pressure level on component design are discussed as well.

The present study is part of the R&D project Hybrid High Solar Share Gas Turbine Systems (HYGATE) which is funded by the German Ministry for the Environment, Nature and Nuclear Safety and the Ministry of Economics and Technology.
A Flux-Conservation Mixing Plane Algorithm for Multiphase Non-Equilibrium Steam Models
Authors: Moraga Francisco J. , Vysohlid Martin , Smelova Natalia , Mistry Hiteshkumar , Atheya Siram , Kanakala Vasudevarao
Published: December 2013

The accuracy of steady multistage turbomachinery calculations is dependent on the exchange of information at an interface, also known as mixing plane, between adjacent blade rows. This paper describes an extension of already available flux conservation mixing plane algorithm to the Eulerian-Eulerian non-equilibrium steam model. Since algorithms that conserve fluxes across the interface have been found to be more accurate and robust, greater emphasis is on the conservation of mixture and droplet fluxes across the interface. The key characteristics of the algorithm are provided, along with its application on simple two- and three-dimensional blade rows.
Contribution to Free and Forced Vibration Analysis of an Intentionally Mistuned Blisk
Authors: Schoenenborn Harald , Junge Michael , Retze Ulrich
Published: December 2013

Most of the experimental mistuning studies are performed using a blisk with random mistuning only. Intentional mistuning is often investigated analytically with respect to aeroelasticity, as it is well known that intentional mistuning reduces the flutter risk due to less interaction between the blades.

In this paper, an intentionally mistuned test blisk is investigated both analytically and experimentally with respect to free and forced vibrations. First, free vibrations are studied and aliasing effects for the intentionally mistuned blisk are analyzed in comparison with a tuned blisk. A comparison between the experimentally determined dominant nodal diameters and the computed ones shows good agreement.

Then, the blisk is experimentally excited by a travelling wave for various engine orders. Similar investigations are performed with a FEM model of the blisk and a reduced-order code. The amplification factor for some modes and several blisks is compared. The influence of the disc onto the blade mode shapes is studied for the tuned and mistuned case without and with aerodynamic coupling effects.

Cyclic spacing of vanes is a concept to reduce the vibration level of downstream rotor blades by distributing the excitation onto more engine orders while reducing the overall excitation level. In this paper it is shown for blisks with and without intentional mistuning that care should be taken in applying this concept in the vicinity of veering regions, because the amplification factor in a veering region may become much higher than compared to other nodal diameters.
Rotordynamic Evaluation of Full Scale Rotor on Tilting Pad Bearings With Integral Squeeze Film Dampers
Authors: Gerbet Matthieu , Catanzaro Michael , Alban Thomas , Vannini Giuseppe
Published: December 2013

In the last 10 years, major centrifugal compressor manufacturers have been investing in developing technologies to improve their products. Following the increasing demand in terms of performance, efficiency and compactness, the current trend in the compressor industry is to increase the “power density”. One big challenge of this “power density” approach is the increase of the rotational speed which may be related to rotordynamic concerns (e.g. crossing of higher rotor modes, stability). Commonly used in the aircraft gas turbines [16], the squeeze film dampers represent an efficient solution to deal with high vibrations and to ensure stable operation for supercritical rotors. In the Oil & Gas Centrifugal Compressors world, SFDs are not so often utilized by the manufacturers but sometimes chosen by the end users as a retrofit solution when high level of synchronous/sub-synchronous vibrations are experienced in the field. The experimental activities described in this paper represent the authors’ Company effort to validate the behavior of a special, integrated SFD type in order to add this component in the available technology portfolio of a centrifugal compressor using it since the design phase. To accomplish this target, the SFD testing was performed originally at the component level and finally at a system level on a “dummy rotor”, specifically designed to mimic the rotordynamic behavior of a real rotor (e.g. running across both the two first rigid modes and the first bending mode). The main objectives of the testing activity were: to check the benefit of using SFDs in order to increase the rotor system damping, to check the SFD overall operational performances, and finally to validate the rotordynamic predictability of this new rotor system. The system level testing program was performed in a high speed balancing bunker where the rotor was equipped with a magnetic exciter able to deliver sub-synchronous excitation. The main test results which will be described in details in the paper are anticipated here. SFDs showed a significant increase in the damping of rigid modes compared to a baseline configuration (rotor running on traditional journal bearings); the SFDs behavior was fully assessed both from rotordynamic viewpoint (rotor and damper housing vibrations) and from operational viewpoint (oil temperature and pressures directly measured in the damper land); finally the rotor modal damping identification techniques are applied to this highly damped rotor system in order to compare the experiment with the relevant predictions. As a conclusion the testing activity provided the authors’ Company with confidence in the use of this integrated SFD technology and enabled a new option for centrifugal compressor design.
Effect of Tip Clearance Flow on the Evaluation of Slip Factor for Micro Impellers
Authors: Sun Qianwei , Gong Yifang , Li Qiushi
Published: December 2013

It is quite evident that the slip factor is extremely important as it enables the energy transfer between the impeller and fluid to be calculated. Therefore, it has been the subject of extensive study so that the stagnation pressure ratio developed and the power absorbed by the compressor could be accurately predicted during design process. This paper describes a CFD investigation on tip clearance flow in micro centrifugal impeller. A study is performed to analyze the influence of comparatively low operating Reynolds numbers on tip clearance flow behavior. The flow structure within micro impeller affected by tip clearance flow is then discussed. The comparative study on shrouded and unshrouded impellers is carried out to evaluate the effect of tip clearance flow on slip factor prediction for micro impeller. The result stressed significant influence of tip clearance flow on micro impeller performance revealing the failure of conventional slip factor prediction model which proposed the demand for proper evaluation of slip factor based on actual flow field.
Turbocharged SI-Engine Simulation With Cold and Hot-Measured Turbocharger Performance Maps
Authors: Aghaali Habib , Ångström Hans-Erik
Published: December 2013

Heat transfer within the turbocharger is an issue in engine simulation based on zero and one-dimensional gas dynamics. Turbocharged engine simulation is often done without taking into account the heat transfer in the turbocharger. In the simulation, using multipliers is the common way of adjusting turbocharger speed and parameters downstream of the compressor and upstream of the turbine. However, they do not represent the physical reality. The multipliers change the maps and need often to be different for different load points. The aim of this paper is to simulate a turbocharged engine and also consider heat transfer in the turbocharger. To be able to consider heat transfer in the turbine and compressor, heat is transferred from the turbine volute and into the compressor scroll. Additionally, the engine simulation was done by using two different turbocharger performance maps of a turbocharger measured under cold and hot conditions. The turbine inlet temperatures were 100 and 600°C, respectively. The turbocharged engine experiment was performed on a water-oil-cooled turbocharger (closed waste-gate), which was installed on a 2-liter gasoline direct-injected engine with variable valve timing, for different load points of the engine. In the work described in this paper, the difference between cold and hot-measured turbocharger performance maps is discussed and the quantified heat transfers from the turbine and to/from the compressor are interpreted and related to the maps.