bluuebunny/crossref_metadata_2025 huggingface dataset:
System y+L: the broad scope and cation modulated amino acid transporter
Authors: Deves R , Angelo S , Rojas AM
Published: December 2014

The properties are discussed of system y+L, a broad scope amino acid transporter which was first identified in human erythrocytes. System y+L exhibits two distinctive properties: (a) it can bind and translocate cationic and neutral amino acids, and (b) its specificity varies depending on the ionic composition of the medium. In Na+ medium, the half‐saturation constant for L‐lysine influx was 9.5 +/− 0.67 microM and the inhibition constant (Ki) for L‐leucine was 10.7 +/− 0.72 microM. L‐Leucine is the neutral amino acid that binds more powerfully, whereas smaller analogues, such as L‐alanine and L‐serine interact less strongly (the corresponding inhibition constants were Ki,Ala, 0.62 +/− 0.11 mM; Ki,Ser, 0.49 +/− 0.08 mM). In the presence of K+, the carrier functions as a cationic amino acid specific carrier, but Li+ is able to substitute for Na+ facilitating neutral amino acid binding. The effect of the inorganic cations is restricted to the recognition of neutral amino acids; translocation occurs at similar rates in the presence of Na+, K+ and Li+. The only structural feature that appears to impair translocation is bulkiness and substrates with half‐saturation constants differing by more than 100‐fold translocate at the same rate. This suggests that translocation is largely independent of the forces of interaction between the substrate and the carrier site. System y+L activity has been observed in Xenopus laevis oocytes injected with the cRNA for the heavy chain of the 4F2 human surface antigen. 4F2hc is an integral membrane protein with a single putative membrane‐spanning domain and it remains to be clarified whether it is part of the transporter or an activator protein.
Proteins that interact with facilitative glucose transporters: implication for function
Authors: Jung CY
Published: December 2014

The cellular uptake of glucose catalysed by the facilitated glucose transporter (GLUT) family is further regulated by metabolites and hormones, most importantly by insulin. All of the six isoforms known in this family possess a large cytoplasmic domain of divergent amino acid sequence. A body of evidence indicates that this domain is important for GLUT regulation. Exactly how this domain participates in the regulation, however, is not known. A likely possibility is that a specific cellular protein interacts with GLUT at this domain, and thus modulates the function. This putative, glucose transporter binding protein (GTBP) may be an enzyme, or a non‐enzymic adaptor or docking protein. Indeed, we have identified several cellular proteins that bind to the cytoplasmic domain of GLUT proteins; these include glyceraldehyde‐3‐phosphate dehydrogenase, glucokinase, GTBP70, GTBP85, GTBP28 and L‐3‐hydroxyacyl‐CoA dehydrogenase. Some of these GLUT‐GTPB interactions are functionally coupled. Whether any of these interactions actually participates in the insulin‐induced GLUT regulation is yet to be determined.
Rapid modulation of L‐type calcium current by acutely applied oestrogens in isolated cardiac myocytes from human, guinea‐pig and rat
Authors: Meyer R , Linz KW , Surges R , Meinardus S , Vees J , Hoffmann A , Windholz O , Grohe C
Published: December 2014

Gender‐based differences in cardiovascular mortality may be due to a cardio‐protective effect of oestrogens on the myocardium. However, mRNA expression of oestrogen receptors in myocardial tissue of the adult heart has yet to be demonstrated. Furthermore, a calcium antagonistic action of 17beta‐oestradiol on myocardial tissue has been discussed. Therefore, two subjects were investigated in atrial myocytes of the human, and ventricular myocytes of guinea‐pig and rat in this study. (1) Are oestrogen receptors expressed in adult myocardial cells? (2) Is there an influence of oestrogens on the L‐type calcium current of cardiac myocytes? Expression of oestrogen receptors was investigated by reverse polymerase chain reaction. L‐type calcium current was usually measured by the patch‐clamp technique in whole‐cell recording mode under selective recording conditions, i.e. overlapping currents were blocked. One series of experiments was performed in perforated patch configuration to avoid internal perfusion. 17beta‐oestradiol inhibited L‐type calcium current reversibly in all three species. At 10(−5) M, the inhibition was 15–20%. This inhibition was independent of the sex and the species. A full concentration response curve of 17beta‐oestradiol on basal L‐type current was recorded from female guinea‐pig myocytes. The inhibition increased from 2% at 10(−7) M to about 30% at 10(−4) M 17beta‐oestradiol. The values could be fitted by a sum of two sigmoidal functions with log EC50 values of −6.5 and −4.9 M and Hill slopes of 2.5 for both. The specificity of the 17beta‐oestradiol action was tested by recording the L‐type current in the presence of 17alpha‐oestradiol and oestrone. 17alpha‐oestradiol also inhibited the current, but with a maximal inhibition of only 17%. The concentration‐response curve could be fitted by a single sigmoidal function (log EC50 −6−3 M; Hill slope 0.55). Oestrone did not influence the current at all. The decrease in L‐type current after the application of 17beta‐oestradiol via a rapid perfusion system developed with a time constant of 3–4 s, which was in the same range as that for the influence of isoprenaline. The isoprenaline‐stimulated L‐type current was much more susceptible to the inhibition by 17beta‐oestradiol, i.e. in pre‐stimulated cells (1) the inhibitory effect is significantly higher (e.g. at 10(−5) M, inhibition was 36.3% compared with 11.2% in untreated cells) and (2) an inhibitory effect can be seen with oestradiol concentrations as low as 10(−9) M. Although the concentrations needed to gain a calcium antagonistic influence on the basal current were much too high to explain a cardio‐protective influence of oestrogens, the presence of oestrogen receptors in cardiac myocytes of all three species, together with the shift in concentration dependence following pre‐stimulation by isoprenaline, suggest that myocytes are a potential target for oestrogen.
Changes in contraction, cytosolic Ca2+ and pH during metabolic inhibition and upon restoration of mitochondrial respiration in rat ventricular myocytes
Authors: Lancaster MK , Harrison SM
Published: December 2014

Exposure of cardiac muscle to metabolic poisons reduces the availability of cellular ATP and cardiac dysfunction ensues. In this study rat ventricular myocytes were exposed to 2‐deoxyglucose, iodoacetate and cyanide to induce complete metabolic blockade. Changes in contraction, cytosolic Ca2+ and pH were determined during metabolic blockade and following restoration of mitochondrial ATP production. Metabolic blockade resulted in a rapid failure of contractions and Ca2+ transients, a rise of diastolic Ca2+, a cytosolic acidosis and ultimately a rigor contracture. Washing out cyanide during the development of the rigor contracture led to a rapid relaxation of the contracture, a fall in cytosolic Ca2+ and a rapid, partial reversal of the cytosolic acidosis. The partial reversal of the cytosolic acidosis and fall of cytosolic Ca2+ were abolished in the presence of oligomycin. This suggests that the rapid partial recovery of cytosolic acidosis could result from the rephosphorylation of ADP to ATP by the mitochondrial F1,F0‐ATPase (a reaction that consumes protons).
Daily patterns of secretion of neurohypophysial hormones in man: effect of age
Authors: Forsling ML , Montgomery H , Halpin D , Windle RJ , Treacher DF
Published: December 2014

The neurohypophysial hormone vasopressin contributes to control of urine output and, while urine flow shows a clear daily rhythm, there has been debate as to whether this is true of neurohypophysial hormones. A study was performed on fifteen adult males, with a mean age of 25 years, over a 24 h period, nine blood samples being taken at regular intervals for the determination of neurohypophysial hormones and indices of fluid balance. Samples were taken via an indwelling cannula so that sleep was undisturbed. A daily variation in the plasma concentrations of oxytocin and vasopressin was demonstrated with concentrations reaching a nadir in the late afternoon. Concentrations of both hormones peaked at 02.00 h. Vasopressin concentrations were inversely correlated with packed cell volume, indicating that the altered hormone release was affecting fluid retention. Consistent with this was the observation that the relationship of plasma osmolality to vasopressin depended on the time of day. To determine the effect of ageing, a similar study was performed on nine healthy elderly subjects with a mean age of 70 years. The nocturnal peak of vasopressin was markedly attenuated, while oxytocin release was similar to that in the younger group. These observations confirm the existence of a daily rhythm in the plasma concentrations of neurohypophysial hormones and indicate that the amplitude of the vasopressin change decreases with age.
Thermoregulation in newborn lambs: influence of feeding and ambient temperature on brown adipose tissue
Authors: Clarke L , Symonds ME
Published: December 2014

We have previously shown that feeding 50 ml of colostrum can increase the thermogenic activity of brown adipose tissue (BAT) in newborn lambs maintained at a warm (30 degrees C) ambient temperature. This study further examines the effect of ambient temperature on BAT and thermoregulation by investigating the response to feeding 50 ml of water. Immediately after vaginal birth, lambs were placed in either a warm (30 degrees C) or cool (15 degrees C) environment a ambient temperature and measurements of colonic temperature and heat production were recorded for 6 h. Lambs were fed 50 ml of water when 5 h old. The level of guanosine 5'‐diphosphate (GDP) binding was higher, but adrenaline content lower in BAT sampled from lambs maintained at 15 degrees C compared with those at 30 degrees C. Feeding was associated with an increase in colonic temperature and plasma concentrations of glucose and non‐esterified fatty acids in lambs maintained at 15 degrees C only. In this group plasma concentrations of adrenaline and dopamine declined after feeding, but noradrenaline concentrations were not influenced by feeding in either group of lambs. O2 consumption and CO2 production were higher in lambs maintained at 15 degrees C but were not influenced by ambient temperature or feeding. It is concluded that feeding a small volume of water can influence thermoregulation by a mechanism that is dependent on the ambient temperature at which the lamb is maintained.
Thermoregulatory responses of the newborn pig during experimentally induced hypothermia and rewarming
Authors: Lossec G , Herpin P , Le Dividich J
Published: December 2014

Exposure to a temperature of 14 degrees C was used to induce a progressive hypothermia in fourteen conscious newborn piglets. Heat production, body (rectal) and skin (between the shoulders) temperatures and shivering intensity assessed as the electromyographic activity (EMG) of longissimus thoracis muscle were measured until body temperature reached 30 degrees C and during a recovery period of 2 h at an ambient temperature of 24 degrees C (n = 7) or 34 degrees C (n = 7). During body cooling, heat production increased up to 9.67 +/− 1.28 W (kg BW)‐1, but started to decrease below a body temperature threshold of 34.4 +/− 0.7 degrees C. EMG activity increased (P < 0.023) curvilinearly during body cooling; the main increase occurred between body temperatures of 38 and 33 degrees C (+142%, P < 0.001), and changes in EMG activity between 33 and 30 degrees C were not significant (+18%, P > 0.1). A marked increase in circulating levels of glucose (+312%, P < 0.001), glucagon (+76%, P < 0.05), adrenaline (+172%, P < 0.05) and noradrenaline (+113%, P < 0.05) occurred during body cooling. Insulin levels were not detectable at 2 h of life and increased during body cooling. During 2 h of rewarming at 24 degrees C, heat production and EMG activity remained elevated, changes in carbohydrate metabolism were not completely reversed and the final body temperature was only 35.6 +/− 0.9 degrees C. Rewarming of the piglets was faster at 34 degrees C. There was a net influx of heat into the animals and heat production and shivering activity decreased when body temperature reached 33.9 +/− 0.5 degrees C; the final body temperature was 37.5 +/− 0.2 degrees C. Circulating levels of lactate, glucagon and catecholamines returned to control levels. These results show that in conscious piglets exposed to a constant cold temperature there is an inverse relationship between EMG activity and body temperature during moderate hypothermia and that the thermoregulatory response and carbohydrate metabolism of the piglet are seriously impaired below a body temperature of 34 degrees C.
Secretory Agonists Stimulate a Rise in Intracellular Cyclic Amp But Not Ca2+ and Inositol Phosphates in Cultured Rat Epididymal Epithelium
Authors: Wong P. Y. D. , Huang S. J.
Published: December 2014

Primary monolayer cultures of rat epididymal cells have been shown to secrete chloride and bicarbonate when stimulated with ß‐adrenergic agents, humoral agents and vasoactive peptides. The intracellular messengers mediating the secretory response are unknown. In this study intracellular AMP, Ca2+ and inositol phosphates were measured in epididymal monolayers at rest and upon stimulation with various secretory agonists. Adrenaline, forskolin, lysylbradykinin, prostaglandin, endothelin, angiotensin II, antidiuretic hormone and vasoactive intestinal peptide at concentrations that stimulate anion secretion caused a rise in intracellular cyclic AMP. The increase in cyclic AMP by adrenaline was blocked by propranolol but not by phentolamine. Studies of the concentration‐effect relationships showed that for adrenaline and endothelin the EC50 for stimulation of cyclic AMP was higher than that for stimulation of anion secretion. None of these agonists affects intracellular Ca2+ concentration and inositol phosphate contents in epididymal monolayers. Ca2+ ionophores A21387, ionomycin and erythrosin B (with irradiation with white light), at concentrations that stimulate anion secretion, also stimulated a rise in intracellular cyclic AMP and concomitantly increased intracellular Ca2+. The increase in cyclic AMP was dependent on extracellular Ca2+. It is not known whether the secretory response to Ca2+ ionophores was mediated by an increase in cell Ca2+ per se, or cyclic AMP. However, it can be concluded that cyclic AMP is the second messenger which mediates the secretory responses to physiological stimuli.
Accurate Characterization of Torsional Stiffness of Flexible Disk Couplings
Authors: Francis Alex , Avdeev Ilya , Hamann Joseph , Ananthasivan Sundar
Published: December 2014

Flexible torsional couplings are used primarily to transmit power between rotating components in industrial power systems, including turbomachinery, while allowing for small amounts of misalignment that may otherwise lead to equipment failure. The torsional coupling lumped characteristics, such as torsional- and flexural stiffness, as well as natural frequencies of vibration are important for design of the entire power system and, therefore, must be calculated or computed with a high degree of accuracy. In this paper, we compare theoretical-, computational-, and experimental methods of characterizing torsional stiffness of a family of metallic disk type flexible couplings. We demonstrate the sensitivity of torsional stiffness to various design parameters and characterization assumptions, including boundary conditions, level of model detail, and material properties of the coupling's components. We also develop a full 3D parametric finite element model of the coupling and report on its experimental validation.
Optimum Damping Control of the Flexible Rotor in High Energy Density Magnetically Suspended Motor
Authors: Fang Jiancheng , Tang Enqiong , Zheng Shiqiang
Published: December 2014

The rated rotational speed of the magnetically suspended motor (MSM) is always above the bending critical speed to achieve high energy density. The rotor will have a dramatic resonance when it passes the critical speed. Then, the magnetic bearing has to provide large bearing force to suppress the synchronous vibration. However, the bearing force is always limited by magnetic saturation and power amplifier voltage saturation. This paper proposed an optimum damping control method which can make effective use of the limited bearing force to minimize the synchronous vibration amplitude of the rotor nearby the critical speed. The accurate rotor model is obtained by theoretical analysis and system identification. The unbalance force response of the bending mode of the rotor is analyzed. The small gain theorem is used to determine the range of the magnitude of the control system. Then, the relationship of the optimum damping varying with the magnitude and phase of the control system nearby the critical speed is analyzed. The run-up experiments are carried out in 315 kW MSM and the results show the effectiveness and superiority of the optimum damping control method.
A Mechanism of Combustion Instability in Lean Premixed Gas Turbine Combustors
Authors: Lieuwen Tim , Torres Hector , Johnson Clifford , Zinn Ben T.
Published: December 2014

There has been increased demand in recent years for gas turbines that operate in a lean, premixed (LP) mode of combustion in an effort to meet stringent emissions goals. Unfortunately, detrimental combustion instabilities are often excited within the combustor when it operates under lean conditions, degrading performance and reducing combustor life. To eliminate the onset of these instabilities and develop effective approaches for their control, the mechanisms responsible for their occurrence must be understood.

This paper describes the results of an investigation of the mechanisms responsible for these instabilities and approaches for their control. These studies found that combustors operating in a LP mode of combustion are highly sensitive to variations in the equivalence ratio (ϕ) of the mixture that enters the combustor. Furthermore, it was found that such ϕ variations can be induced by interactions of the pressure and flow oscillations with the reactant supply rates. The ϕ perturbations formed in the inlet duct (near the fuel injector) are convected by the mean flow to the combustor where they produce large amplitude heat release oscillations that drive combustor pressure oscillations. It is shown that the dominant characteristic time associated with this mechanism is the convective time from the point of formation of the reactive mixture at the fuel injector to the point where it is consumed at the flame. Instabilities occur when the ratio of this convective time and the period of the oscillations equals a specific constant, whose magnitude depends upon the combustor design. Significantly, these predictions are in good agreement with available experimental data, strongly suggesting that the proposed mechanism properly accounts for the essential physics of the problem. The predictions of this study also indicate, however, that simple design changes (i.e., passive control approaches) may not, in general, provide a viable means for controlling these instabilities, due to the multiple number of modes that may be excited by the combustion process. This conclusion indicates that active control strategies may be necessary for controlling these instabilities.
An Experimental and Modeling Study of Humid Air Premixed Flames
Authors: Bhargava Anuj , Colket Med , Sowa William , Casleton Kent , Maloney Dan
Published: December 2014

An experimental and modeling study has been performed jointly by UTRC and DOE-FETC to determine the effect of humidity in the combustion air on emissions and stability limits of gas turbine premixed flames. This study focuses on developing gas turbine combustor design criteria for the Humid Air Turbine (HAT) cycle. The experiments were conducted at different moisture levels (0%, 5%, 10% and 15% by mass in the air), at a total pressure of 200 psi, pilot levels (0%, 1%, 3% and 5% total fuel), and equivalence ratio (0.4 to 0.8 depending on the moisture levels). The moisture levels were achieved by injecting steam into dry air well upstream of the fuel-air premixing nozzle. Computations were made for comparison to the experiments using GRI Mech 2.11 kinetics and thermodynamic database for modeling the flame chemistry. A Perfectly Stirred Reactor (PSR) network code was used to create a network of PSRs to simulate the flame. Excellent agreement between the measured and modeled NOx (5–10%) was obtained. Trends of added moisture reducing NOx and the effects of equivalence ratio and piloting level were well predicted. The CO predictions were higher by about 30–50%. The CO discrepancies are attributed to in-probe oxidation. The agreement between the data and model predictions over a wide range of conditions indicate the consistency and reliability of the measured data and usefulness of the modeling approach. An analysis of NOx formation revealed that at constant equilibrium temperature, Teq, the presence of steam leads to lower O-atom concentration which reduces “Zeldovich and N2O” NOx while higher OH-atom concentration reduces “Fenimore” NOx.
Equations of State for Gas Compressor Design and Testing
Authors: Kumar Sumit K. , Kurz Rainer , O’Connell John P.
Published: December 2014

In the design and testing of gas compressors, the correct determination of the thermodynamic properties of the gas. such as enthalpy, entropy and density from pressure, temperature and composition, plays an important role. Due to the wide range of conditions encountered, pressure, specific volume and temperature (p-v-T) equations of state (EOS) and ideal gas heat capacities, along with measured data, are used to determine the isentropic efficiency of a compressor configuration and to model the actual behavior of real gases and compressors.

There are many possible model choices. The final selection should depend on the applicability of the EOS to the gas and the temperature dependence of the heat capacities, as well as the particular process of interest along with the range of pressures and temperatures encountered. This paper compares the thermodynamic properties from five commonly used equations in the gas compressor industry: the Redlich-Kwong (RK), Redlich-Kwong-Soave (RKS), Peog-Robinson (PR), Benedict-Webb-Rubin-Starling (BWRS), and Lee-Kesler-Plocker (LKP) models. It also compares them with a high accuracy EOS for methane from Wagner and Setzmann in the common range for gas compressors. The validity of a linear temperature dependence for ideal gas heat capacities is also evaluated. The objective was to determine if the models give significant differences in their predicted efficiencies.

It was found that different EOS gave somewhat different enthalpy changes for methane, ethane and nitrogen for real compressions. This appeared to be connected to the different densities given by the models. Interestingly, the isentropic enthalpy changes are quite similar, suggesting that the effect is canceled out when two properties are involved. However, since the efficiency is the ratio of isentropic enthalpy change to actual enthalpy change, the EOS yield different efficiencies. These differences are on the same order as the typical tolerances allowed for prediction and testing of industrial gas compressors (3 to 5%) and comparisons with the highly accurate equation of state for pure methane from Wagner and Setzmann (1991) showed similar differences.

Commonly, the ideal gas heat capacity is assumed linear in temperature from 10 to 150°C (50 to 300°F). Comparison of this form with a quadratic expression from the literature and the highly accurate equation of Wagner and Setzmann for methane, showed insignificant differences among the methods for temperatures up to 600°K (1080°R).
Vapor Phase Lubrication for Expendable Gas Turbine Engines
Authors: Wagner Matthew J. , Forster Nelson H. , Van Treuren Kenneth W. , Gerardi David T.
Published: December 2014

Vapor Phase Lubrication (VPL) is an emerging technology that is currently targeted for application in limited life, expendable engines. It has the potential to cut 90% of the cost and weight of the lubrication system, when compared to a conventional liquid lubricated system. VPL is effective at much higher temperatures than conventional liquid lubrication (600°C vs. 200°C), so considerably less cooling for the bearing is required, to the extent that the bearing materials often dictate the maximum upper temperature for its use. The hot #8 bearing and the cold #1 bearing of the T63 engine were used to evaluate the applicability of this technology to the expendable engine environment. The #8 bearing was a custom made hybrid with T15 steel races, silicon nitride balls, and a carbon-carbon composite cage; it was run for 10.7 hours at a race temperature of 450°C at full power, without incident. Prior to engine tests, a bearing rig test of the #8 bearing demonstrated an 18.6-hour life at a race temperature of 500°C at engine full power speed of 50,000 rpm. Cold bearing performance was tested with the standard #1 bearing, which consisted of 52100 steel races and bails, and a bronze cage; it was run for 7.5 hours at a race temperature of 34°C at flight idle power, without incident. A self-contained lubricant misting system, running off compressor bleed air, provided lubricant at flow rates of 7–25 ml/hr, depending on engine operating conditions. These tests have demonstrated for the first time, that a single self-contained VPL system can provide adequate lubrication to both the hot and cold bearings for the required life of an expendable cruise missile engine.
Prediction of By-Pass Transition by Means of a Turbulence Weighting Factor: Part II — Application on Turbine Cascades
Authors: Steelant J. , Dick E.
Published: December 2014

To simulate transitional heat transfer experiments in turbine cascades, the conditionally averaged Navier-Stokes equations are used. To cover both the physics of freestream turbulence and the intermittent flow behaviour during transition, a turbulence weighting factor τ is used. A transport equation for this factor, constructed for low Mach number flows, is extended to cope with compressibility. Compressibility in combination with turbulence level and pressure gradient are prime factors for the correct evaluation of the transitional zone. The method is validated on transitional heat transfer measurements in a linear turbine cascade at typical operational conditions.
An Experimental Study on the Aerodynamics and the Heat Transfer of a Suction Side Film Cooled Large Scale Turbine Cascade
Authors: Ganzert Wolfgang , Fottner Leonhard
Published: December 2014

As a part of a more complex research program systematic isothermal investigations on the aerodynamics and heat transfer of a large scale turbine cascade with suction side film cooling were carried out. The film cooling through a row of holes at forty percent chord length on the suction side was supplied by a large plenum chamber. Two injection geometries were hitherto tested and evaluated: cylindrical holes with thirty respectively fifty degrees axial inclination angle and no lateral inclination. Typical engine conditions for the Mach and Reynolds number as well as the inlet turbulence level were maintained.

The aerodynamic studies are based on steady state pressure measurements. The static profile pressure distribution together with oil-and-dye flow visualisation gives information on the surface flow conditions and boundary layer development especially in the near hole region. The measured data also comprise local and integral total pressure loss coefficients obtained by pressure probe traversing at mid span downstream of the cascade. The heat transfer examination set-up is based on the steady state liquid crystal technique using a compound of a thermochromic sheet combined with an electrical surface heating layer attached on an adiabatic blade corpus. Two dimensional pseudo colour plots are used for the documentation of the local surface heat transfer coefficient distribution and hot spot estimation. Laterally averaged and statistically analysed data of the surface heat transfer is applied in overall heat transfer examinations.

All this data is used for a joint aerodynamic flow and surface heat transfer optimisation of a blowing configuration in suction side film cooled turbine cascade.

The most important conclusions can be summarised as follows: Aiming at an optimised design of cylindrical film cooling configurations the axial inclination of the holes should be kept low thus diminishing the suction peak value at the cooling position in the profile pressure distribution and decreasing the mainstream deceleration area upstream of the jets. This also leads to reduced total pressure losses. Through the high influence of the blowing on the aerodynamics the flow in the near hole mixing region is highly three-dimensional. This shows significant effects in the two-dimensional surface distribution and the laterally averaged heat transfer coefficient.

Oil-and-dye pictures confirm the observations qualitatively.
Film Cooling Effectiveness in the Showerhead Region of a Gas Turbine Vane: Part II — Stagnation Region and Near-Suction Side
Authors: Witteveld Virginia C. , Polanka Marc D. , Bogard David G.
Published: December 2014

An experimental study was conducted to determine the effects of film cooling on a gas turbine vane at two mainstream turbulence intensities of Tu = 0.5% and Tu = 22%. The low speed turbine vane test facility was designed to match the Reynolds number of operating engine conditions. The nine-time scale model airfoil simulates a gas turbine first-stage stator vane. The leading edge film cooling hole showerhead array included six rows of film cooling holes configured with one stagnation row, two pressure side rows, and three suction side rows. This paper presents film cooling effectiveness measurements in the stagnation region and near-suction side. Cooled air injection was used to conduct the tests at a density ratio of DR = 1.8 and blowing conditions over a range of M = 0.5 to M = 2.9. Infrared imaging techniques were used to measure the surface temperature distribution. The results provide a detailed evaluation of the effects of blowing ratio, mainstream turbulence, and stagnation line position on the measured effectiveness in the showerhead. The effect of increasing blowing ratio generally resulted in increased spanwise averaged effectiveness levels. The effect of mainstream turbulence varies with blowing ratio within the showerhead region. At low blowing ratio, high turbulence produced greater effectiveness, whereas at high blowing ratio, low turbulence produced greater effectiveness. The effect of stagnation line position also varied with blowing ratio. Overall, the dominating effect occurred when the blowing ratio was sufficiently strong to cause a spanwise merging of adjacent cooling jets resulting in very good spanwise uniformity and high adiabatic effectiveness.
Status of Catalytic Combustion R&D for the Department of Energy Advanced Turbine Systems Program
Authors: Fant D. B. , Jackson G. S. , Karim H. , Newburry D. M. , Dutta P. , Smith K. O. , Dibble R. W.
Published: December 2014

This paper discusses some of the advanced concepts and research and development associated with implementing catalytic combustion to achieve ultra-low-NOx emissions in the next generation of land-based gas turbine engines. In particular, the paper presents current development status and design challenges being addressed by Siemens Westinghouse Power Corp. for large industrial engines (> 200 MW) and by Solar Turbines for smaller engines (< 20 MW) as part of the U.S. Department of Energy’s (DOE) Advanced Turbine Systems (ATS) program. Operational issues in implementing catalytic combustion and the current needs for research in catalyst durability and operability are also discussed. This paper indicates how recent advances in reactor design and catalytic coatings have made catalytic combustion a viable technology for advanced turbine engines and how further research and development may improve catalytic combustion systems to better meet the durability and operability challenges presented by the high-efficiency, ultra-low emissions ATS program goals.
Performance of a Reduced NOx Diffusion Flame Combustor for the MS5002 Gas Turbine
Authors: Feitelberg Alan S. , Starkey Michael D. , Schiefer Richard B. , Pavri Roointon E. , Bender Matt , Booth John L. , Schmidt Gordon R.
Published: December 2014

This paper describes a reduced NOx diffusion flame combustor that has been developed for the MS5002 gas turbine. Laboratory tests have shown that when firing with natural gas, without water or steam injection, NOx emissions from the new combustor are about 40% lower than NOx emissions from the standard MS5002 combustor. CO emissions are virtually unchanged at base load, but increase at part load conditions. The laboratory results were confirmed in 1997 by a commercial demonstration test at a British Petroleum site in Prudhoe Bay, Alaska.

The standard MS5002 gas turbine is equipped with a conventional, swirl stabilized diffusion flame combustion system. The twelve standard combustors in an MS5002 turbine are cylindrical cans, approximately 27 cm (10.5 inches) in diameter and 112 cm (44 inches) long. A small, annular, vortex generator surrounds the single fuel nozzle that is centered at the inlet to each can. The walls of the cans are louvered for cooling, and contain an array of mixing and dilution holes that provide the air needed to complete combustion and dilute the burned gas to the desired turbine inlet temperature.

The new, reduced NOx emissions combustor (referred to as a “lean head end”, or LHE, combustor) retains all of the key features of the conventional combustor: the only significant difference is the arrangement of the mixing and dilution holes in the cylindrical combustor can. By optimizing the number, diameter, and location of these holes, NOx emissions were substantially reduced. The materials of construction, fuel nozzle, and total combustor air flow were unchanged.

The differences in NOx emissions between the standard and LHE combustors, as well as the variations in NOx emissions with firing temperature, were well correlated using turbulent flame length arguments. Details of this correlation are also presented.
Design and Evaluation of an Auto-Tuning Control System for an Altitude Test Facility
Authors: Luppold R. H. , Meisner R. , Norton J. M.
Published: December 2014

Simulated altitude testing of large aircraft engines is a very expensive, but essential step in the development and certification of gas turbines used by commercial airlines. A significant contributor to the cost of this process is the time-intensive task of manually tuning the facility control system that regulates the simulated flight condition. Moreover, control system tuning must be performed each time the test conductor changes the flight condition. An adaptive control system that automatically performs this task can significantly reduce the costs associated with this type of engine testing.

This paper examines the features of an auto-tuning controller architecture that contains both disturbance feedforward and PID feedback components in a two-input, two-output multivariable configuration. The paper reviews the underlying concepts of an auto-tuning system and contrasts its advantages/disadvantages with respect to other adaptive control techniques. The algorithm used to automatically tune the controller does not require a facility model. However, a nonlinear facility model was developed and used to substantiate a decoupled-loop design approach, to validate the controller design concept, and to evaluate the resulting adaptive control system design performance. This analysis and other practical design issues that impact the auto-tuning control system performance are addressed in the paper. The paper also presents results that illustrate the automatic tuning sequence and the disturbance rejection performance exhibited by this system during large engine transients at several key points in the flight envelope. The auto-tuning controller described in the paper was implemented at a Pratt & Whitney flight test facility used in the development of large, high bypass ratio gas turbines.
Effect of Blade Curving on the Flow Field Structure in an Annular Turbine Cascade
Authors: Song Yanping , Wang Zhongqi , Lu Wencai , Xu Wenyuan
Published: December 2014

In the present paper, two annular turbine cascades have been tested in order to investigate the effect of blade curving on the structure of the three-dimensional flow field. The blades in all two cascades have the same section and they are stacked on the trailing edge that is straight in the first and a circular arc in the second. Detailed cascade tests consisted of passage flow parameter traverses, blade and endwall surface pressure distribution, and flow visualization.

The results show that the flow field is three dimensional in an annular cascade with different pressure distributions near two endwalls, whose direct effect is amplified through the creation of passage vortices of different scale and strength at hub and tip. Blade curving changes the pressure field completely, in axial, pitchwise and spanwise directions. The combined effect of 3-D characteristics and blade curving causes significant differences of flow field structure in curved blade.
Evaluation of Higher-Order Terms in the Throughflow Approximation Using 3D Navier-Stokes Computations of a Transonic Compressor Rotor
Authors: Baralon Stephane , Eriksson Lars-Erik , Håll Ulf
Published: December 2014

Two three-dimensional Reynolds-averaged Navier-Stokes solutions of the Nasa 67 transonic compressor rotor with tip clearance, computed at near-peak efficiency and near-stall flow conditions, have been circumferentially averaged in order to evaluate the circumferential spatial fluctuation terms such as u′u′, u′v′, u′w′, etc. The three-dimensional distribution of these fluctuations is presented and physically interpreted for the two flow conditions. Then, the meridional distributions of the tangential average of each of these fluctuation terms, the so-called perturbation stresses, are described and interpreted for the two flow conditions. A meridional throughflow computation for which all stresses were included has been performed for the near-peak efficiency flow condition using a time-marching finite-volume solver. The calculation proved to be in good agreement with the tangentially averaged 3D solution. Moreover, the relative importance of the perturbation and viscous stresses has been investigated. The influence of the viscous stresses on the meridional flow was not found important whereas the perturbation stresses were identified as significant contributors to the blade passage losses and to the spanwise mixing phenomenon. Furthermore, the relative effects of each perturbation term on the meridional flow prediction have been investigated for the near-peak efficiency case. The u′w′~, v′w′~, u′v′~ and u′u′~ stresses proved to exert a significant influence on the prediction of blade design key parameters such as flow angles and losses in the tip region, essentially.
An Average Passage Closure Model for General Meshes
Authors: Kirtley K. R. , Turner M. G. , Saeidi S.
Published: December 2014

Use of the average passage equations for simulating the steady flow in multistage tarbomachinery has been limited in practice to H-type meshes with a “pure” or “strict” character in which pitchwise mesh lines have no axial or radial variation. This requirement is due to the original implementation of the model for the deterministic component of the Adamczyk stress tensor which closes the average passage equations. Such meshes can be highly distorted, especially near blunt leading edges or around highly staggered airfoils. A more general implementation of the closure model is developed which permits the use of general meshes of varying topology and character and exploits the conservation properties of the underlying CFD algorithm. The derivation of the new implementation is based on the FAS multigrid forcing function construction and is identical to the original implementation when applied to pure H-meshes. An isolated cascade simulation is presented which demonstrates a typical improvement in accuracy when non-pure H-meshes are employed. Also, results for a two and one half stage research turbine are presented which employed the new closure implementation and show some of the other benefits of using more general grids, namely improved convergence rate and reduced computation times.
A Transonic Compressor Design Methodology Including the Influence of 3D Passage Shock Waves
Authors: Gui X. , Zhou S.
Published: December 2014

Throughflow theory, as a design problem, is extensively used in the design of transonic axial flow compressors and fans. The losses caused by a simplified passage shock named shock loss model were taken into account in the design of transonic stages. However, the influences of shock waves on flow fields are still under development for transonic design. This problem is studied in the present paper.

The basic equations of the throughflow method are re-derived under the concept of discontinuous passage averaging, and then, the distribution shock forces acied on the averaged throughflow fields are obtained. To evaluate these effects on averaged throughflow fields, a passage shock structure model is developed based on the previous models. Finally, the shock influences are assessed and compared in the present paper. It is demonstrated that the distribution shock forces have dramatically effects on the results of design.
Experimental and Numerical Investigation of the Flow in a Centrifugal Compressor Volute
Authors: Hagelstein D. , Hillewaert K. , Van den Braembussche R. A. , Engeda A. , Keiper R. , Rautenberg M.
Published: December 2014

This paper presents the experimental and numerical investigation of an outward volute of rectangular cross section. The investigation is carried out at the level of

- stage performance,

- volute performance and

- detailed flow field study at selected peripheral positions for various operating points.

The objective of the investigation was to gain further knowledge about the flow structure and loss mechanism in the volute. Simultaneously with the experimental investigation, a numerical simulation of the flow in the volute was carried out.

A 3D Euler-code was used in which a wall friction term and a tuned artificial dissipation term account for viscous effects. A reasonable agreement between the experimental and numerical results is observed. As a result a good and detailed knowledge about the pressure recovery and loss mechanism in the volute is obtained.
CFD Analysis and Optimization of Industrial Turbine Exhaust Systems
Authors: Luo Jiang , Twardochleb Chris
Published: December 2014

Numerical analyses have been carried out for the 3-D flow field inside turbine exhaust diffuser-collector systems. The analyses were performed with a multi-block computational fluid dynamics (CFD) package which solves the Reynolds-averaged Navier-Stokes equations and the turbulence (k and ε) transport equations. Complex flow features, including the 3-D screw-type vortices inside the collector as well as the flow interaction near the diffuser-collector interface are revealed and examined. Their impact on the pressure recovery of the whole exhaust system was investigated through numerical simulations. It has been found that significant performance improvement can be obtained by managing the collector vortex size and strength and reducing the interaction loss. The effects of inlet flow conditions, including the velocity profile (blockage, etc) and the turbulence level on the pressure recovery are studied. The CFD analyses have been utilized to obtain a new design of diffuser-collector system with higher pressure recovery and lower manufacturing cost. Significant performance improvement of this new design over the existing design has been confirmed by the data. Comparison of rig test data and CFD predictions indicates that the 3-D CFD procedure has captured the major flow features and can be used as a valuable design tool.
Royal Navy Experience of Propulsion Gas Turbines and How and Why This Experience is Being Incorporated Into Future Designs
Authors: Rand James , Wright Nigel
Published: December 2014

The Royal Navy (RN) has in-service experience of both marinised industrial and aero derivative propulsion gas turbines since the late 1940’s. Operating through a Memorandum of Understanding (MOU) between the British, Dutch, French and Belgian Navies the current in-service propulsion engines are marinised versions of the Rolls Royce Tyne, Olympus and Spey aero engines. Future gas turbine engines, for the Royal Navy, are expected to be the WR21 (24.5 MW), a 5 to 8 MW engine and a 1 to 2 MW engine in support of the All Electric Ship Project.

This paper will detail why the Royal Navy chose gas turbines as prime movers for warships and how Original Equipment Manufacturers (OEM) guidance has been evaluated and developed in order to extend engine life. It will examine how the fleet of engines has historically been provisioned for and how a modular engine concept has allowed less support provisioning.

The paper will detail the planned utilisation of advanced cycle gas turbines with their inherent higher thermal efficiency and environmental compliance and the case for all electric propulsion utilising high speed gas turbine alternators. It will examine the need for greater reliability / availability allowing single generator operation at sea and how by using a family of 3 engines a nearly flat Specific Fuel Consumption (SFC) down to harbour loads can be achieved.
Propagation of Multiple Short Length-Scale Stall Cells in an Axial Compressor Rotor
Authors: Inoue M. , Kuroumaru M. , Tanino T. , Furukawa M.
Published: December 2014

Evolution and structure of multiple stall cells with short length-scale in an axial compressor rotor have been investigated experimentally. In a low-speed research compressor rotor tested, a short length-scale stall cell appeared at first, but did not grow rapidly in size unlike a so-called “spike-type stall inception” observed in many multi-stage compressors. Alternatively, the number of cells increased to a certain stable state (a mild stall state) under a fixed throttle condition. In the mild stall state the multiple stall cells, size of which was on the same order of the inception cell (a few blade spacings), were rotating at 72% of rotor speed and at intervals of 4.8 blade spacings. With further throttling, a long length-scale wave appeared overlapping the multiple short length-scale waves, then developed to a deep stall state with a big cell.

In order to capture the short length-scale cells in the mild stall state, a so-called ‘double phase-locked averaging technique’ has been developed, by which the flow field can be measured phase locked to both of the rotor and the stall cell rotation. Then, time-dependent ensemble averages of the 3D velocity components upstream and downstream of the rotor have been obtained with a slanted hot-wire, and the pressure distributions on the casing wall with high response pressure transducers.

By a physically plausible explanation for the experimental results, a model for the flow mechanism of the short length-scale stall cell has been presented. The distinctive feature of the stall cell structure is on the separation vortex bubble with a leg traveling ahead of the rotor, with changing the blade in turn on which the vortex leg stands.