bluuebunny/crossref_metadata_2025 huggingface dataset:
Basic fibroblast growth factor induces myocardial hypertrophy following acute infarction in rats
Authors: Scheinowitz M , Kotlyar A , Zimand S , Ohad D , Leibovitz I , Bloom N , Goldberg I , Nass D , Engelberg S , Savion N , Eldar M
Published: December 2014

Basic fibroblast growth factor (bFGF) is a potent mitogen which induces growth of collateral vessels in ischaemic and infarcted myocardium. The effect of systemically administered bFGF on left ventricular (LV) function, myocardial hypertrophy and LV remodelling following acute myocardial infarction (MI) have not yet been fully investigated. Thirty Sprague‐Dawley male rats were randomized to receive bFGF (0.5 mg) or rat albumin intraperitoneally for 1 week, beginning immediately after the induction of MI. Five animals served as controls and did not undergo any operation. Animals were killed 6 weeks after surgery and the hearts were perfused and fixed at physiological pressure. Transverse cross‐sections from infarcted areas were stained with antibodies against proliferating cell nuclear antigen (PCNA) and Masson‐trichrome and analysed with a coloured‐image analyser for LV area (mm2), LV cavity diameter (mm), infarcted area (%), and wall thickness (mm) in infarcted and non‐infarcted regions. LV area was similar in MI rats and in controls (41.7 +/− 6.9 and 43.0 +/− 1.5 mm2, respectively) and was significantly larger in MI bFGF‐treated (MI/bFGF) animals (47.6 +/− 7.1 mm2) (P = 0.023). LV cavity diameter was significantly larger in the MI group than in MI/bFGF and control animals (6.0 +/− 0.8, 4.9 +/− 1.4, and 4.4 +/− 0.8 mm, respectively, P = 0.018). Wall thickness in the non‐infarcted region was significantly smaller in MI animals (1.4 +/− 0.3 mm) than in MI/bFGF animals (1.6 +/− 0.4 mm) and the control group (1.6 +/− 0.1 mm) (P = 0.015). The ratio between LV cavity diameter/non‐MI wall thickness was higher in MI than in control and MI/bFGF groups (4.8 +/− 1.6, 2.7 +/− 0.6 and 3.3 +/− 1.8, respectively, P = 0.03). Proliferating endothelial cells were significantly more abundant in infarcted than in normal areas in both MI and MI/bFGF groups, but with no significant differences between the groups. Intraperitoneal administration of bFGF did not cause any untoward extracardiac effects. Thus, systemic bFGF administration following acute MI in rats prevents dilatation of the LV, induces hypertrophy of the non‐infarcted myocardium and exerts no untoward effects on extracardiac organs.
Physiological responses to moderate cold stress in man and the influence of prior prolonged exhaustive exercise
Authors: Weller AS , Greenhaff PL , Macdonald IA
Published: December 2014

A study was undertaken in man to investigate whether during moderate cold stress, the proportion of carbohydrate (CHO) oxidized is increased, and whether prior prolonged exhaustive exercise compromises thermoregulation. Eight euglycaemic men were cooled by a liquid‐conditioned suit (1) after an overnight fast (Con) and (2) approximately 2 h after an exercise protocol in which CHO availability was substantially lowered (Post‐Ex). The cooling stimulus lasted 90 min (Cooling) and was preceded by a 30 min thermo‐neutral baseline phase (Base). In Con, aural temperature (T(aural)) and the rate of CHO oxidized (CHOox) were not altered from the values at Base during Cooling, whereas the following were increased: the rate of heat production (Hprod, approximately 1.9‐fold), thigh electromyographical activity (EMG, approximately 2.5‐fold), and the rate of fat oxidized (FATox, approximately 1.7‐fold). In Post‐Ex, T(aural) did not decrease from the value at Base during Cooling, and compared with Con, EMG, CHOox and the rate of heat loss were not different, whereas Hprod (P < or = 0.01), FATox (P < or = 0.01) and mean skin temperature (P < or = 0.01) were higher, and T(aural) was lower (P < or = 0.05). It is concluded that during moderate cold stress, shivering thermogenesis is supported by an increase in the oxidation of fat, and despite an alteration in the initial thermoregulatory responses to Cooling approximately 2 h after exhaustive exercise, thermoregulation was not impaired.
Effects of peptide fragments of protein kinase C on isolated rat osteoclasts
Authors: Moonga BS , Dempster DW
Published: December 2014

The intracellular mechanisms responsible for inhibition of osteoclast activity are of significant interest in the search for more effective ways of managing bone diseases associated with enhanced bone resorption. Previous studies have suggested that the protein kinase C (PKC) pathway is an important inhibitory second messenger in osteoclasts. We, therefore, investigated the effects of the synthetic peptide fragments, PKC(530–558) and (19–36), which correspond to parts of the catalytic and regulatory domains of PKC, on the activity of isolated osteoclasts. These fragments have been shown to activate and inhibit PKC, respectively, in biochemical studies employing isolated rat brain PKC, but have rarely been employed in studies of cellular activity. PKC(19–36), an enzyme inhibitor (PKC‐I), had no effect by itself on osteoclastic bone resorption. However, PKC(530–558), a PKC activator (PKC‐A), caused a dose‐responsive inhibition of bone resorption, which was accompanied by a rapid and distinctive change in osteoclast morphology. This effect was reversible: (a) upon removal of PKC‐A, (b) upon continuous exposure to this fragment for more than 36 h, or (c) in the presence of PKC‐I. In conclusion, a short synthetic peptide fragment of PKC (PKC‐A) significantly inhibits osteoclastic bone resorption; this, together with the fact that the inhibitory effect is abolished in the presence of PKC‐I, provides further evidence for an important physiological role for the PKC pathway in the regulation of osteoclast activity. Selective activation of this pathway may have important therapeutic implications for the management of bone diseases associated with enhanced resorption.
Effects of arginine vasotocin, isotocin and melatonin on blood pressure in the conscious atlantic cod (Gadus morhua): hormonal interactions?
Authors: Kulczykowska E
Published: December 2014

The effects of exogenous arginine vasotocin (AVT), isotocin (IT) and melatonin on the blood pressure of conscious Atlantic cod (Gadus morhua) were examined. Ventral aortic blood pressure (PVA) was recorded from a cannula inserted into the afferent branchial artery of the third gill arch. Dorsal aortic blood pressure (PDA) was recorded via a cannula implanted into the efferent branchial artery in the same gill arch. Each fish received two doses (10 and 50 ng kg‐1) of AVT, IT and melatonin. AVT was also administered in combination with melatonin. Injection of 10 ng kg‐1 AVT produced significant hypertension, especially in animals injected during the daytime. In contrast, the same dose of IT induced no significant change in either PVA or PDA. Administration of 10 ng kg‐1 melatonin at night caused a long‐lasting decrease in both parameters. Melatonin also inhibited the increase in blood pressure elicited by AVT. These results indicate that AVT, but not IT, is vasopressor in the cod. The effects of combined administration of melatonin and AVT show the antihypertensive action of melatonin in AVT‐induced hypertension.
The control of timing and amplitude of EMG activity in landing movements in humans
Authors: Santello M , McDonagh MJ
Published: December 2014

The control of self‐initiated falls from different heights was studied. The objective of the study was to investigate in a quantitative manner the modulation of EMG timing (i.e. onset from take‐off and duration from onset to touch‐down) and amplitude (before and after foot contact) as a function of fall height. The muscles studied were m. soleus and m. tibialis anterior. Kinematic (ankle joint angle) and kinetic (ground reaction force) variables were also measured. Six subjects took part in the experiments that consisted of ten landings from each of five heights (0.2, 0.4, 0.6, 0.8 and 1 m) onto a force platform. We found a consistent pattern of co‐contraction before and after touch‐down across the fall heights studied. In both muscles, the onset of pre‐landing EMG activity occurred at a longer latency following take‐off when landing from greater heights. The absolute EMG duration was affected to a lesser extent by increasing fall height. These findings suggest that the onset of muscle activity of the muscles studied prior to foot contact is timed relative to the expected time of foot contact. Pre‐ and post‐landing EMG amplitude tended to increase with height. Despite a doubling in the magnitude of ground reaction force, the amplitude of ankle joint rotation caused by the impact remained constant across heights. These findings suggest that the observed pattern of co‐contraction is responsible for increasing ankle joint stiffness as fall height is increased. The attainment of an appropriate level of EMG amplitude seems to be controlled by (a) timing muscle activation at a latency timed from the expected instant of foot contact and (b) varying the rate at which EMG builds up.
Cardiovascular and respiratory responses to chronic intermittent hypoxia in adult female rats
Authors: Souza George Miguel P. R. , Bonagamba Leni G. H. , Amorim Mateus R. , Moraes Davi J. A. , Machado Benedito H.
Published: December 2014

New Findings

What is the central question of this study?

Chronic intermittent hypoxia (CIH) induces hypertension in male rats. There is evidence that the development of high blood pressure in females is attenuated in other models of hypertension. Due to the lack of information about the cardiovascular effect of CIH in female rats, we set out to determine whether female rats develop hypertension after CIH.

What is the main finding and its importance?

Different from other experimental models of hypertension, adult female rats develop high blood pressure after CIH. These findings provide new perspectives for a better understanding of the neural mechanisms underlying the development of hypertension in females.

Adult male rats develop hypertension in response to chronic intermittent hypoxia (CIH). Female rats are known to be protected against the development of hypertension in several experimental models. In this study, we aimed to verify whether the development of hypertension was also prevented in female rats exposed to CIH. Adult female rats were submitted to 35 days of CIH, 8 h per day. At the end of the CIH protocol, the rats were anaesthetized for the implantation of an arterial catheter and the next day the mean arterial pressure and heart rate were recorded in conscious rats. Considering that changes in the respiratory pattern have been associated with the development of hypertension in the CIH model, the respiratory pattern of adult female rats was also evaluated after CIH exposure using whole‐body plethysmography. Adult female rats submitted to CIH (n = 27) presented a significant increase in mean arterial pressure when compared with the control group (n = 26). Moreover, CIH‐exposed female rats presented an increase in the frequency and duration of apnoeas when compared with control rats. These data show that adult female rats develop changes in the respiratory pattern and high blood pressure in response to CIH.
A Performance Prediction Model for Low-Speed Centrifugal Fans
Authors: Wolfe Tristan , Lee Yu-Tai , Slipper Michael E.
Published: December 2014

A generalized model for mapping the trend of the performance characteristics of a double-discharge centrifugal fan is developed based on the work by Casey and Robinson (C&R), which formulated compressor performance maps for tip-speed Mach numbers ranging from 0.4 to 2 using test data obtained from turbochargers with vaneless diffusers. The current paper focuses on low-speed applications for Mach number below 0.4. The C&R model uses four nondimensional parameters at the design condition including the flow coefficient, the work input coefficient, the tip-speed Mach number, and the polytropic efficiency, in developing a prediction model that requires limited geometrical knowledge of the centrifugal turbomachine. For the low-speed fan case, the C&R formulas are further extended to a low-speed, incompressible analysis. The effort described in this paper begins by comparing generalized results using efficiency data obtained from a series of fan measurements to that using the C&R model. For the efficiency map, the C&R model is found to heavily depend on the ratio of the flow coefficient at peak efficiency to that at the choke flow condition. Since choke flow is generally not applicable in the low-speed centrifugal fan operational environment, an alternate, but accurate estimation method based on fan free delivery derived from the fan test data is presented. Using this new estimation procedure, the modified C&R model predicts reasonably well using the double-discharge centrifugal fan data for high-flow coefficients, but fails to correlate with the data for low-flow coefficients. To address this undesirable characteristic, additional modifications to the C&R model are also presented for the fan application at low flow conditions. A Reynolds number correction is implemented in the work input prediction of the C&R model to account for low-speed test conditions. The new model provides reasonable prediction with the current fan data in both work input and pressure rise coefficients. Along with the developments for the efficiency and work input coefficient maps, the use of fan shut-off and free delivery conditions are also discussed for low-speed applications.
Conceptual Engineering of a CRGT System for Exhaust Heat Recovery in an Existing Compressor Station
Authors: Botros K. K. , de Boer M. J. , Fletcher H. G.
Published: December 2014

Conceptual engineering design of a chemically recuperated gas turbine (CRGT) system was carried out for an existing GE-LM2500 based natural gas compressor station. The configured system was evaluated using the commercial process simulation software ASPEN PLUS®. The results of the thermodynamic assessment showed an increase in thermal efficiency from 34% to 38% and an increase of the site actual output power by 15% at full load and for the same mass flow of air through the gas turbine compressors. The mass flow rate through the combustor and turbines increases only by 5%, which can be accommodated with the existing driver hardware. The present paper provides equipment identification, costs and economic evaluation for this specific system. The water needed for the CRGT system was drawn from an aquifer source through two wells capable of a continuous combined throughput of 2.8 liters/s (i.e. ∼22 GPM each). Environmental assessment of the system showed that the equivalent CO2 emission at full load decreases from ∼ 600 kg/MW.hr to 520 kg/MW.hr (i.e., 13%). The overall system economics shows that a return on capital investment is attainable in 5 years.
Optimum Load Allocation in Cogeneration Gas-Steam Combined Plants
Authors: Cerri Giovanni , Monacchia Stefano , Seyedan Babak
Published: December 2014

A procedure to optimize operations has been developed for cogeneration systems based on gas, steam and gas-steam combined cycles. Component statuses recognition by monitoring data and cost accounting technique have been taken into consideration. An objective function including components and machinery operational and availability costs has been selected. To search the minimum of such a function a simultaneous solution method with modular plant description has been adopted. The objective function is related to economic-functional models of the various components and to the boundary conditions expressing the ambient, power and heat loads. Test prototypes have shown the capability to achieve the optimum load allocation. The paper discusses the general block diagram of the system together with an application to an industrial cogeneration plant. Optimized operations are analyzed and discussed.
Technical and Economic Analysis of Repowering a Coal-Fired Power Plant
Authors: Roy-Aikins Joseph , Rampershad Reshleu J.
Published: December 2014

Owing to an abundance of coal reserves, about 92 percent of the electrical power produced in South Africa is generated in central power stations fired on cheaply priced coal. With a few power stations approaching the end of their design life, the question arises as to what to do with these outdated and inefficient plants. Retrofitting or repowering a station with gas turbines is one option being considered. As a case study, this paper investigates the technical and economic feasibility of repowering the Arnot power station to convert it to a combined cycle plant with increased capacity. This power station has six generating units, each of nominal capacity 350 MW and of average age 25 years. Four are in service, and the others are in reserve storage. Several repowering options were considered and the proposed re-design is parallel repowering, where additional steam for a steam turbine is generated in a gas turbine heat recovery steam generator to supplement the steam generated in a coal-fired boiler. Since natural gas, the preferred fuel for gas turbines, is not readily available in the country, kerosene was used as gas turbine fuel. Consequently, the performance of the chosen gas turbine had to be re-evaluated.

The output of each unit increased by 77 MW and the efficiency by 8 percentage points to 43 percent, after repowering. Repowering was feasible, technically. An economic analysis was required to determine the magnitude of the economic benefits of repowering, if any, and it turned out that the cost of electricity generated by the new technology was higher than that produced by the outgoing one. It was concluded, therefore, that repowering the steam turbine units with gas turbines fired on kerosene was uneconomical, for the performance level achieved.
Effective Decision Making in Simple and Combined Cycle Schemes at the Turn of the Millennium
Authors: Gayraud Stéphane , Singh Riti
Published: December 2014

The electricity supply industry is being restructured all over the world. Privatisation, with the emergence of Independent Power Projects (IPPs), especially in developing countries, and liberalisation of the power generation market are changing decision-making processes in a radical way. New challenges of deregulation and customer demands, and economic instabilities in south-east Asia, oblige electric utilities to face a double jeopardy: least-cost planning and least-risk investments.

Consumers are encouraged to save energy and emission reduction policies are implemented to promote utilisation of high efficiency, clean power production technologies.

The aim of this paper is to introduce the concept of life cycle risk management and Decision Support System (DSS) for open and combined cycle schemes, highlighting the market potential for Flexible Mid-size Gas Turbines (FMGT) in mid-merit applications.

The DSS that has been developed at Cranfield University includes: plant simulation program, providing design and off-design performance, maintenance planning, component degradation, and load-following models. In addition several economic techniques based upon engineering finance and project accounting make power plant economic appraisals possible.

The DSS also provides a Monte Carlo risk analysis in order to deal with technical and economic uncertainties in a very effective way.

Case studies will stress several parameters that planners have to carefully assess when making decision in the context of the coming millennium, bringing all sorts of new challenges and areas of uncertainty that will be discussed in the paper.
Hybrid Brush Pocket Damper Seals for Turbomachinery
Authors: Laos Hector E. , Vance John M. , Buchanan Steven E.
Published: December 2014

Pocket damper seals perform a dual function: both sealing the pressurized gas around a rotating shaft and providing large amounts of vibration damping. The annular cavity between the labyrinth seal teeth is subdivided into separate annular cavities around the circumference of the rotor by partitioning walls. Also, the upstream and downstream teeth have different radial clearances to the rotor. These seals have been shown to provide a remarkable amount of direct damping to attenuate vibration in turbomachinery, but they generally leak more than conventional labyrinth seals if both seals have the same minimum clearance. Conversely, brush seals allow less than half the leakage of labyrinth seals, but published test results show no significant amount of damping. They are considered to be a primary choice for the seals in new aircraft engine designs because of their low leakage. This paper will describe a recently invented hybrid brush/pocket damper seal that combines high damping with low leakage. Previous brush seal results were studied and calculations were made to select a brush seal to combine with the pocket damper design. The result is a hybrid seal with high damping and low leakage. A special design feature can also allow active vibration control as a bonus benefit.

A computer code written for the original pocket damper seal was modified to include the brush element at the exit blade. Results from the computer code indicate that the hybrid seal can have less leakage than a six bladed (or 6 knives) labyrinth seal along with orders of magnitude more damping.

Experimental evaluations of the damping and leakage performance of the hybrid seal are being conducted by the authors. The experimental work reported here tested the damping capability of the new hybrid brush seal by exciting the seal journal through an impedance head. A conventional six-bladed labyrinth seal of the same working dimensions was also tested. The brush hybrid pocket damper seal is found to leak less than the labyrinth seal while producing two to three times more damping than the original pocket damper seal, (orders of magnitude more than the conventional labyrinth).
Experimental Measurements of Actively Controlled Bearing Damping With an Electrorheological Fluid
Authors: Vance John M. , Ying Daniel
Published: December 2014

Selection criteria and design evaluations of several types of bearing dampers with active control for application to aircraft engines were described in a companion paper (Vance, Ying, and Nikolajsen, 1999). A disk type electrorheological (ER) damper was chosen for further study and testing. The results of the tests and the final conclusions of the study are described in this paper. Experimental results including stiffness and damping coefficients are presented for the ER bearing damper with two types of ER fluid, 350 CS and 10 CS (centistokes) viscosity. The vibration attenuation performance of the ER damper was measured on a rotordynamic test rig in the form of free vibration decay, rotor orbits, and runup unbalance responses. The results show that the ER fluid with lower viscosity has the better characteristics for rotordynamic applications. It was found that ER fluids produce both Coulomb and viscous damping. If only the damping is considered, the Coulomb type is less desirable, but with active control it can also achieve control of rotor stiffness as analyzed in Vance and San Andres (1999). A feedback control system was developed and applied to the ER damper with the objective of improving the overall rotordynamic performance of the rotor bearing system, considering both vibration amplitudes and dynamic bearing forces. A “bang-bang” (on and off) simple control logic was found to work better in practice than more sophisticated schemes. The measured runup responses of the rotor-bearing system with this control approximated the desired vibration response curves fairly well. The tests highlighted some of the practical considerations that would be important for aircraft engine applications, such as the ER fluid limitations, the electrical power supply requirements, the electrical insulation requirements, the nonlinear relationship between the voltage and the damping, and the relative benefits of active control. It is concluded that active control of bearing damping is probably not a practical improvement over the passive squeeze film dampers currently used in most aircraft gas turbine engines.
Steady and Dynamic Stall Analysis of the NLR 7301 Airfoil
Authors: Weber Stefan , Platzer Max F.
Published: December 2014

The static and dynamic stall behavior of the supercritical NLR 7301 airfoil is analyzed with a 2D thin-layer Navier-Stokes code. The code solves the compressible Reynolds-averaged Navier-Stokes equations with an upwind biased numerical scheme in combination with the Baldwin-Lomax or the Baldwin-Barth turbulence models. The effect of boundary layer transition is incorporated using the transition length model of Gostelow et al. The transition onset location is determined with Michel’s formula or it can be specified as an input parameter. The two turbulence models yield significantly different steady-state lift coefficients at incidences greater than 8 degrees. Also, the lift hysteresis loops are strongly affected by the choice of the turbulence model. The use of the one-equation Baldwin-Barth model together with the Gostelow transition model is found to give substantially better agreement with the experimental data of McCroskey et al. than the Baldwin-Lomax model.
Turbomachinery Wakes: Differential Work and Mixing Losses
Authors: Rose Martin G. , Harvey Neil W.
Published: December 2014

In this paper the mixing of stator wakes in turbomachinery is considered. An extension is made to the existing model of Denton (1993), which addresses the effects of acceleration before mixing. Denton showed that if a total pressure wake was accelerated mixing loss diminished and vice versa. Here a total temperature wake is shown to exhibit a reverse trend. An attempt is also made to better understand the work transfer process between a stator wake and a rotor. The paper concentrates on axial turbines, but a brief look at compressors is included. It is argued that the freestream work is not the same as the wake work and the concept of ‘Differential Work’ is introduced. A simple steady velocity triangle based model is proposed to give an estimate of the ratio of wake work to freestream work (μ see later). The model is compared to an unsteady CFD result to offer some verification of the assumptions. It is concluded that the rotodynamic work process tends to reduce total pressure wake depths in turbines and compressors and therefore mixing losses. The mixing loss due to total temperature wakes is less strongly affected by the differential work process.
Deviation in Axial Turbines at Subsonic Conditions
Authors: Islam A. M. T. , Sjolander S. A.
Published: December 2014

An improved correlation is presented for the deviation in axial turbines at subsonic flow conditions. Development of the correlation began with the assumption that the deviation is primarily determined by the blade loading (pressure difference) towards the trailing edge. The blade row parameters which influence this pressure difference are identified. A functional form for the correlation was then assumed and the unknown coefficients in the function were determined based on a database of known values of the deviation. This database includes in-house experimental results, estimates of deviation obtained from Navier-Stokes simulations, as well as cases from the literature for which sufficient geometric data are provided. The evaluation of the empirical coefficients of the correlation was treated as an optimization problem. The optimization was performed using a genetic algorithm which proved very effective and robust. The new deviation correlation appears to be significantly more successful than existing correlations.
Film Cooling Effectiveness and Heat Transfer Coefficient Distributions Around Diffusion Shaped Holes
Authors: Yu Y. , Yen C-H. , Shih T. I-P. , Chyu M. K. , Gogineni S.
Published: December 2014

Presented in this paper is an experimental study focusing on the effects of diffusion hole-geometry on overall film cooling performance. The study consists of three different but closely related hole shapes: (1) Shape A: straight circular hole with a 30-degree inclined injection, (2) Shape B: same as Shape A but with a 10-degree forward diffusion, and (3) Shape C: same as Shape B with an additional 10-degree lateral diffusion. The blowing ratios tested are 0.5 and 1.0. The density ratio is nominally equal to one. Measurements of the experiment use a transient liquid crystal technique that reveals local distributions of both film effectiveness (η) and heat transfer coefficient (h). The data obtained indicate that Shape C with a combined forward and lateral diffusion produces a significant increase in η and decrease in h as compared to Shape A, the baseline case. These improvements combined yield an about 30% to 50% reduction in heat transfer or thermal load on the film protected surface. Shape B, with forward diffusion only, shows a much less significant change in both film effectiveness and overall heat transfer reduction than Shape C. However, it has the lowest heat transfer coefficient in the vicinity of the injection hole among all the three hole-shapes studied. A flow visualization study using pulsed laser sheet-light reveals that Shape A and Shape B inherit quite similar flow structures. The coolant injected out of Shape C flows much closer to the protected wall than that of Shape A and Shape B.
Heat Transfer on a Film-Cooled Rotating Blade
Authors: Garg Vijay K.
Published: December 2014

A multi-block, three-dimensional Navier-Stokes code has been used to compute heat transfer coefficient on the blade, hub and shroud for a rotating high-pressure turbine blade with 172 film-cooling holes in eight rows. Film cooling effectiveness is also computed on the adiabatic blade. Wilcox’s k-ω model is used for modeling the turbulence. Of the eight rows of holes, three are staggered on the shower-head with compound-angled holes. With so many holes on the blade it was somewhat of a challenge to get a good quality grid on and around the blade and in the tip clearance region. The final multi-block grid consists of 4784 elementary blocks which were merged into 276 super blocks. The viscous grid has over 2.2 million cells. Each hole exit, in its true oval shape, has 80 cells within it so that coolant velocity, temperature, k and ω distributions can be specified at these hole exits. It is found that for the given parameters, heat transfer coefficient on the cooled, isothermal blade is highest in the leading edge region and in the tip region. Also, the effectiveness over the cooled, adiabatic blade is the lowest in these regions. Results for an uncooled blade are also shown, providing a direct comparison with those for the cooled blade. Also, the heat transfer coefficient is much higher on the shroud as compared to that on the hub for both the cooled and the uncooled cases.
Effects of Flow Gap Atop Pin Elements on the Heat Transfer From Pin Fin Arrays
Authors: Chyu M. K. , Yen C. H. , Ma W. , Shih T. I-P.
Published: December 2014

This study investigates the effect of gap atop an inline array of cubic fins on the heat transfer from various participating surfaces in the channel housing the array. Five different gap sizes of C/H = 0.25, 0.5, 1.0 and 2.0, as well as the baseline case without gap (C/H = 0.0) are examined and compared. The array consists of twelve rows of three columns. All tests use a unified Reynolds number at 16,000 based on the mean velocity in the channel and cube height. The heat transfer measurement uses a liquid crystal imaging technique combined with a one-dimensional, transient conduction mode) and a lumped heat-capacity model. The results reveal that the heat transfer from the surfaces uncovered by the cubic fins in the test channel generally decreases with the size of the clearance atop the array. However, such a decreasing trend is insignificant for cases with relatively smaller gaps, i.e. C/H = 0.25 and 0.5. Under these conditions, the heat transfer from the surface of cubic fin, in fact, is higher than that of the baseline case. The vortex enriched shear layer separated from the sharp edges around the cube top is considered to be responsible for this phenomenon.
Aerodynamic Damping Characteristics of a Transonic Turbine Cascade
Authors: Aotsuka Mizuho , Watanabe Toshinori , Machida Yasuo
Published: December 2014

The unsteady aerodynamic characteristics of oscillating thin turbine blades were studied both experimentally and numerically to obtain the comprehensive knowledge on the aerodynamic damping of the blades operating in transonic flows. The experiment was carried out in a linear cascade tunnel by use of the influence coefficient method. The two flow conditions were adopted, namely, a near-design condition and an off-design condition with a higher back pressure. In the results for the near-design case, a strong vibration instability was observed in the positive side of the interblade phase angle. In the off-design case, however, the instability did not appear for almost all the interblade phase angles. A drastic change was found in the phase angle of unsteady aerodynamic force between the two cases, which change was a governing factor for the oscillation instability. Numerical simulation based on 2-D Euler equation revealed that the phase change came from the change in phase of the unsteady surface pressure across the shock impingement point on the blade suction surface in the off-design case. The numerical results also showed that the aerodynamic damping increased with increasing reduced frequency, and that the oscillation instability disappeared.
Application of a Thermal-Hydraulic Management Model to Gas Turbine Combustors and Fuel Systems
Authors: Mawid M. A. , Arana C. A. , Sekar B.
Published: December 2014

An advanced thermal management analysis tool, named Advanced Thermal Hydraulic Energy Network Analyzer (ATHENA), has been used to simulate a fuel system for gas turbine engines. The ATHENA tool was modified to account for JP-8/dodecane fuel properties. The JP-8/dodecane fuel thermodynamic properties were obtained from the SUPERTRAP property program. A series of tests of a fuel system simulator located at the Air Force Research Laboratory (AFRL)/Wright Patterson Air Force Base were conducted to characterize the steady state and dynamic behavior of the fuel system. Temperature, pressures and fuel flows for various fuel pump speeds, pressure rise and flow control valve stem positions (orifice areas), heat loads and engine fuel flows were measured. The predicted results were compared to the measured data and found to be in excellent agreement. This demonstrates the capability of the ATHENA tool to reproduce the experimental data and, consequently, its validity as an analysis tool that can be used to carry out analysis and design of fuel systems for advanced gas turbine engines. However, some key components in the fuel system simulator such as control components, which regulate the engine fuel flow based on predetermined parameters such as fan speed, compressor inlet and exit pressures and temperatures, combustor pressure, turbine temperature and power demand, were not simulated in the present investigation due to their complex interactions with other components functions. Efforts are currently underway to simulate the operation of the fuel system components with control as the engine fuel flow and power demands are varied.
One Step Ahead Adaptive Control for Gas Turbine Power Plants
Authors: Camporeale S. M. , Dambrosio L. , Fortunato B.
Published: December 2014

The feasibility of the application of One Step Ahead Adaptive (OSAA) Control technique to a gas turbine power plant is investigated. The OSAA technique is a control algorithm especially suitable for non-linear and time-varying systems. This technique uses the Least Square algorithm to estimate in real-time a linear model of the controlled system, and, uses the estimated linear model to evaluate the feedback control variables.

The proposed technique allows to control the Gas Turbine power plant in a wide range of electric loads due to its intrinsic adaptive capabilities. Moreover, the OSAA control does not require the knowledge of the dynamic characteristics (e.g. state space systems or transfer functions) in order to design the control system.

The OSAA control system has been applied to a single shaft Gas Turbine power plant, which is numerically simulated. The proposed control technique has been tested both in Single-Input Single Output (SISO) mode and in Multi-Input Multi-Output (MIMO) mode. Starting from a steady-state condition, the power plant has been supposed to undergo a step reduction of the electric load. The results show that the OSAA control technique effectively counteracts the load reduction with limited overshoots in the controlled variables and, introducing a integral correction, a negligible static error.
Full Load and Part-Load Performance Prediction for Integrated SOFC and Microturbine Systems
Authors: Campanari Stefano
Published: December 2014

During the last years, two new subjects among the others have risen interest in the field of small scale electric power generation: advanced microturbines and Solid Oxide Fuel Cells.

This paper investigates the thermodynamic potential of the integration of the Solid Oxide Fuel Cell technology with microturbine systems, in order to obtain ultra-high efficiency small capacity plants, generating electric power in the range of 250 kW with 65% LHV net electrical efficiency and with the possibility of cogenerating heat. A detailed description of the calculation model is presented, capable of full and part-load performances analysis of the microturbine and of the integrated SOFC+microturbine system.
Suppression of Secondary Flows in a Turbine Nozzle With Controlled Stacking Shape and Exit Circulation by 3D Inverse Design Method
Authors: Watanabe H. , Harada H.
Published: December 2014

For the axial turbine stage, the design of circulation rVθ¯ distribution between the nozzle and blade has an important effect on the stage performance, because it determines the work distribution in the blade, the stage reaction and the twisting shape of the blade. This paper describes the new method of full 3D design for axial turbine nozzles and blades by applying the 3D inverse design method in which the blade geometry can be determined by specified distributions of circulation rVθ¯ and blade thickness. In this 3D inverse design method, spanwise work distribution of the turbine stage is controlled by specifying the rVθ¯ distribution of the nozzle exit. In this design procedure, rVθ¯ distribution at the nozzle exit and 3D stacking condition are both controlled by 3D inverse method so as to suppress the nozzle secondary flows effectively. The desirable rVθ¯ distribution and 3D stacking shape which were obtained by the 3D inverse method were confirmed by Dawes’ 3D Navier-Stokes analysis. The results shows that the secondary loss is reduced when the design rVθ¯ at the mid-span is set larger compared to that near the endwall. In addition to the control of the rVθ¯ distribution, 3D stacking shape added only in the front part of the nozzle is very effective to suppress the secondary flows, although this 3D stacking shape is very simple compared to a conventional bowed type stacking. Moreover, when this stacking shape is used, spanwise distribution of work does not change from the design condition unlike the case of conventional bowed type stacking shape. The results of single stage performance test conducted using an air turbine facility show an improvement in efficiency compared to the 2D designed stage and prove viability of the 30 inverse design of axial turbine blades.
A Parametric Design Tool for Cascades of Airfoils
Authors: Corral Roque , Pastor Guillermo
Published: December 2014

The primary purpose of this work was to develop a parametric tool to ease the generation of two-dimensional airfoil shapes. The present methodology was initially conceived to design turbine blades and therefore some characteristics of the approach were oriented towards the solution of this specific problem, however, most of the basic formulation is readily extended to the design of other aerodynamic shapes (wings, compressors, etc.). The system combines a CAD oriented methodology, where the user may interactively define the blade by means of control points, with the requirement of producing a highly differentiable curve. Both statements are essentially contradictory since high degree polynomials tend to be extremely sensitive to variations in either its coefficients or control points and therefore not well suited for its direct manipulation. The solution adopted is based on the generation of two chains of highly differentiable Bézier curves where the design is carried out in the downstream direction. A methodology is described to generate low and high turning low pressure turbine airfoils as well as OGV’s.
Modeling Shrouded Stator Cavity Flows in Axial-Flow Compressors
Authors: Wellborn Steven R. , Tolchinsky Ilya , Okiishi Theodore H.
Published: December 2014

Experiments and computational analyses were completed to understand the nature of shrouded stator cavity flows. From this understanding, a one-dimensional model of the flow through shrouded stator cavities was developed. This model estimates the leakage massflow, temperature rise and angular momentum increase through the cavity, given geometry parameters and the flow conditions at the interface between the cavity and primary flow path. This cavity model consists of two components, one which estimates the flow characteristics through the labyrinth seals and the other which predicts the transfer of momentum due to windage. A description of the one-dimensional model is given. The incorporation and use of the one-dimensional model in a multistage compressor primary flow analysis tool is described. The combination of this model and the primary flow solver was used to reliably simulate the significant impact on performance of the increase of hub seal leakage in a twelve stage axial-flow compressor. Observed higher temperatures of the hub region fluid, different stage matching and lower overall efficiencies and core flow than expected could be correctly linked to increased hub seal clearance with this new technique. The importance of including these leakage flows in compressor simulations is shown.
Aerodynamic Analysis of Multistage Turbomachinery Flows in Support of Aerodynamic Design
Authors: Adamczyk John J.
Published: December 2014

This paper summarizes the state of 3D CFD based models of the time average flow field within axial flow multistage turbomachines. Emphasis is placed on models which are compatible with the industrial design environment and those models which offer the potential of providing credible results at both design and off-design operating conditions. The need to develop models which are free of aerodynamic input from semi-empirical design systems is stressed. The accuracy of such models is shown to be dependent upon their ability to account for the unsteady flow environment in multistage turbomachinery. The relevant flow physics associated with some of the unsteady flow processes present in axial flow multistage machinery are presented along with procedures which can be used to account for them in 3D CFD simulations. Sample results are presented for both axial flow compressors and axial flow turbines which help to illustrate the enhanced predictive capabilities afforded by including these procedures in 3D CFD simulations. Finally, suggestions are given for future work on the development of time average flow models.
Failure Analysis of the Steam Injected Aeroderivative Gas Generator During Acceptance Running
Authors: Haq Inam U.
Published: December 2014

This paper discusses the extensive failure of a widely used aeroderivative gas generator during certification running. The steam-injected engine had 1241 hours of logged operation in a regeneration facility providing process steam to the gas plants and electric power to the grid. The engine operating parameters and metallurgy of the damaged hardware’s components are reviewed. External and internal evidences displayed serious damage of the compressor rear frame assembly caused by an internal fire. The major damage was in the axial direction from aft of the compressor rotating CDP (compressor discharge pressure) seal and ended at the stage one high pressure turbine nozzle support. The internal fire was caused by lube oil leaking through a worm-hole in the oil supply tube connector located at the CRF (compressor rear frame). The hole was made by rubbing of the oil supply tube with the edges of the insulation blanket. The air at this location carries sufficient thermal energy at high power settings to create auto-ignition condition. The failure was an isolated event in the well-reputed history of the engine.
The NEREUS Installation — The Non-Nuclear Part (GT)
Authors: Crommelin G. A. K.
Published: December 2014

This paper should be read in conjunction with the paper The NEREUS installation — the nuclear part (HTR). This part will discuss the non-nuclear part of the nuclear gas turbine installation called the NEREUS installation.

It will discuss the non-nuclear part of a modular energy production installation consisting of an inherently safe, helium cooled, graphite moderated nuclear reactor, which acts as heat source to an energy conversion unit consisting of a closed-cycle recuperative gas turbine driving a generator (abbreviated as HTR-GT) (see also ref. 11 and 12). The paper is based upon an ongoing study, supported by specialists and scientists, among others of the Delft University of Technology, of most aspects concerning this type of power producing unit. This paper will discuss its (non-nuclear) components, efficiency, market potential and costing in comparison with existing and comparable installations. So it will report on a pre-feasibility study, based upon existing reports, publications, estimations by specialists and from active projects.
Cyclic Finite Element Modeling of Shrouded Turbine Blades Including Frictional Contacts
Authors: Szwedowicz J.
Published: December 2014

A new cyclic finite element model for shrouded blades is proposed. Using this technique, a contact area between the shrouds is computed with a good accuracy. Imposing a no-slip condition on the computed contact area, eigen-frequencies of the shrouded blades are calculated with very good agreement in relation to measurements. This method is verified with measurements of non-rotating and rotating bladed disc assemblies.