bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of a combination of 0.1% octenidine dihydrochloride and 2% 2‐phenoxyethanol (octenisept®) on wound healing in pigs in vivo and its in vitro percutaneous permeation through intact and barrier disrupted porcine skin
Authors: Stahl Jessica , Braun Michael , Siebert Joerg , Kietzmann Manfred
Published: February 2010

A combination of 0.1% octenidine dihydrochloride and 2% 2‐phenoxyethanol (octenisept®) is a commonly used disinfectant in human medicine. As porcine skin represents an adequate model for human skin, the effect of octenidine dihydrochloride and phenoxyethanol on wound healing is studied in pigs. Furthermore, the in vitro percutaneous permeation of the test substances is studied. The impact of the test formulations on wound healing is examined (A) under non occlusive conditions and (B) in comparison to another disinfectant based on povidone‐iodine under occlusive conditions, while wounds are treated daily with the test substances. The percutaneous permeation of octenidine dihydrochloride and phenoxyethanol is studied in Franz‐type diffusion cells with intact skin as well as barrier disrupted after tape stripping. Compared with povidone‐iodine or vehicle treatment as well as untreated control wounds the treatment of wounds with the test formulation has no influence on the healing rate in pigs and does not induce retardation of wound healing. The in vitro diffusion experiment reveals that octenidine dihydrochloride is only detectable in the acceptor chamber of three‐barrier disrupted skin samples. Phenoxyethanol permeates through intact porcine skin in amounts of 11.3% and through barrier disrupted skin in amounts of 43.9%
Comparison of 2,4‐D and dicamba treatments for embryo development and plant regeneration in crosses between Lolium multiflorum Lam. and Dactylis glomerata L.
Authors: Komatsu Toshinori , Uchiyama Kazuhiro , Arakawa Akira , Tase Kazuhiro
Published: February 2010

We compared the effects of 2,4‐dichlorophenoxy acetic acid (2,4‐D) and 6‐dichloro‐2‐methoxybenzoic acid (dicamba) treatments on embryo development and plant regeneration in crosses between Lolium multiflorum Lam. and Dactylis glomerata L. Two embryos (1.1% of pollinated florets) were obtained after 2,4‐D treatment for 2 days. They germinated on hormone‐free Murashige and Skoog (MS) medium containing 1 g L−1 yeast extract, 70 g L−1 sucrose and 6 g L−1 agar, and developed into green seedlings. Dicamba treatment for 2 days gave higher frequencies of embryo development (4.3% of pollinated florets) than did 2,4‐D treatment, but only one embryo (0.4% of pollinated florets) germinated on hormone‐free MS agar medium, and no seedling was obtained. These results show that 2,4‐D is more effective than dicamba at producing F1 hybrids on hormone‐free MS agar medium. The F1 plant was intermediate between the parents in height, inflorescence morphology and lower leaf appearance. The folding of leaves in young shoots and the number of glumes resembled those of D. glomerata. Anthers did not dehisce. The F1 plant was an aneuploid with 26 chromosomes. The mean chromosome association was 0.04 trivalents, 10.36 bivalents and 5.16 univalents at metaphase I in pollen mother cells.
Responses of vegetation to soil disturbance by Sibelian marmots within a landscape and between landscape positions in Hustai National Park, Mongolia
Authors: Yoshihara Yu , Okuro Toshiya , Buuveibaatar Bayarbaatar , Undarmaa Jamsran , Takeuchi Kazuhiko
Published: February 2010

Can an examination of the interactive effects of soil disturbance by rodents and landscape positions on vegetation response evaluate the ecological role of the keystone species (ecosystem engineers) at a broad scale, thereby providing good approaches to the management of the key engineers for healthy Mongolian steppes? To answer this question, we surveyed plants growing on and off the mounds created by Siberian marmots (Marmota sibirica) among 14 landscape positions and within a single mountain slope in a forested steppe region of Mongolia. Significant interactions between landscape position and soil disturbance by marmots were seen in forb volume. The impact of soil disturbance on species composition was low in mountain areas and high on depositional plains. Soil disturbance may have changed microenvironments from xeric to more humid or from moist to more xeric, depending on the other site characteristics. Collectively, our results suggest that sedimentation and pre‐existing water conditions modify the relationships between soil disturbance and landscape position. Because the landscapes can be divided clearly into those that received only positive influences and those that received only negative influence from the marmot disturbance, zoning becomes more meaningful. Our a priori evaluation of the influence of keystone engineers on ecosystems at a broad scale could provide insights into how to optimize the performance of ecosystem engineering in a way that is beneficial to ecosystem management.
MASS TRANSFER KINETICS OF BANANA SLICES DURING OSMO‐CONVECTIVE DRYING
Authors: KADAM DATTATREYA M. , DHINGRA DEVINDER
Published: February 2010

The mass transfer kinetics of banana slices during osmotic dehydration in terms of water loss and solid gain in sugar syrup was studied. The effect of process parameters such as thickness of banana slices (4, 8 and 12 mm), sugar syrup concentration (40, 50 and 60% w/w) and sample‐to‐sugar syrup solution ratio (1:2, 1:4 and 1:6) on water loss and solute gain were also evaluated. Water losses and solid gains were increased with increase in sugar syrup concentration and banana slice sample‐to‐sugar syrup solution ratio and it has increased with the decrease in thickness of banana slices. Two‐factor analysis of variance for all experiments indicated that osmosis time of banana and sugar syrup solution concentration, sample‐to‐sugar ratio and thickness of banana slices were highly significant, whereas combination osmosis time and sugar syrup solution concentration, sample‐to‐sugar ratio and thickness of banana slices were nonsignificant. Osmotic time of 5–6 h was required to attain maximum water loss and solid gain by banana slices. The optimum best combination of banana osmosis for water loss and solid gain were found to be: 50% sugar syrup solution + 8 mm thickness of banana slices + 1:6 sample‐to‐sugar syrup solution ratio. Drying kinetics of osmosis banana slices were studied in a laboratory model tray dryer at 55, 60 and 65C air temperature. Seven thin‐layer drying models were fitted to the experimental moisture ratio data. Among the mathematical models investigated, the Wang and Singh model satisfactorily described the drying behavior of banana with high r2 values of 0.9989. The effective moisture diffusivity ranged from 5.3 × 10−8to 9.3 × 10−8 m2/s.

PRACTICAL APPLICATIONS

The process of osmotic dehydration can be used for the preparation of shelf‐stable products for the purpose of use during off‐season. The quality of pre‐osmosed banana slices are much more superior to the product dehydrated with the convectional method of convective dehydration. The osmotically dehydrated banana slices can be used as banana‐figs, fruit candy, fruit toffee, infant food and it can become part of foodstuffs like cakes, pastries and many others.
KINETICS OF MASS TRANSFER DURING CONVECTIVE DEHYDRATION OF COATED OSMOSED PINEAPPLE SAMPLES
Authors: SINGH C. , SHARMA H.K. , SARKAR B.C.
Published: February 2010

The pineapple samples were coated with sodium alginate (0.5–5%) and osmosed in sucrose solution. The effect of coating and temperature (55, 65 and 75C) on the convective dehydration characteristics and quality parameters of dried pineapple samples were studied. The mass transfer kinetics were then evaluated. The dehydration time for the uncoated sample was less than the coated sample at all the three temperatures. The drying rate of the uncoated sample was more than the coated sample. The effective moisture diffusivity varied in the range of 2.09 × 10−10–3.42 × 10−10 m2/s. A nonlinear regression procedure was used to fit five thin‐layer drying models to the experimental drying curves. The models were compared using the coefficient of determination, mean relative percent error, root mean square error and reduced chi‐square. The Midilli model has shown a better fit to the experimental drying data as compared with other models.

PRACTICAL APPLICATIONS

The treatment of coating before osmotic dehydration helps in reducing the problem of large solute intake without affecting much on the water removal. The fruits obtained by combining coating, osmotic dehydration and convective dehydration exhibit better nutritional quality, good appearance and extended shelf life. The product can be used in the areas of nonavailability of fruit. The fruits after rehydration can be added in ice cream, yoghurt and confectionary products.
The role of soil community biodiversity in insect biodiversity
Authors: BENNETT ALISON
Published: February 2010

Abstract. 1. This study demonstrates that feedback loops between plants and insects contribute to both plant and insect diversity. Synthesis of several studies reveals that both bottom‐up and top‐down forces are important for plant and insect communities.

2. Feedback loops between plants and soil organisms contribute to plant and soil diversity. An analysis of multiple systems reveals that pathogens, mutualists, and a wide variety of soil fauna directly influence, and are influenced by, plant diversity.

3. The connection of plant–insect and soil–plant feedback loops leads to the maintenance of all three groups, and the maintenance of these feedback loops crucially affects insect diversity. Examples of the influence of soil community diversity on insect diversity, and the influence of insect diversity on soil community diversity, as well as feedbacks through all three trophic levels are provided.

4. Finally, means of conserving and restoring soil communities to influence the conservation and restoration of insect communities are discussed.
Update: Application of the Finite Element Method to Linear Elastic Fracture Mechanics
Authors: Banks-Sills Leslie
Published: February 2010

Since the previous paper was written (Banks-Sills, 1991, “Application of the Finite Element Method to Linear Elastic Fracture Mechanics,” Appl. Mech. Rev., 44, pp. 447–461), much progress has been made in applying the finite element method to linear elastic fracture mechanics. In this paper, the problem of calculating stress intensity factors in two- and three-dimensional mixed mode problems will be considered for isotropic and anisotropic materials. The square-root singular stresses in the neighborhood of the crack tip will be modeled by quarter-point, square and collapsed, triangular elements for two-dimensional problems, respectively, and by brick and collapsed, prismatic elements in three dimensions. The stress intensity factors are obtained by means of the interaction energy or M-integral. Displacement extrapolation is employed as a check on the results. In addition, the problem of interface cracks between homogeneous, isotropic, and anisotropic materials is presented. The purpose of this paper is to present an accurate and efficient method for calculating stress intensity factors for mixed mode deformation. The equations presented here should aid workers in this field to carry out similar analyses, as well as to check their calculations with respect to the examples described.
Gas Temperature Profile Attenuation Through a Multistage Axial-Flow Turbine
Authors: Mamaev Boris I. , Petukhovskiy Mikhail M.
Published: February 2010

Nowadays 2D through-flow models are widespread for designing and analysis of a turbine. Unlike 2D calculations, the measurements show that a non-uniform inlet gas temperature profile is strongly attenuated to the outlet of a turbine. This attenuation can be taken into account in through-flow models only using some corrective coefficients. The objective of this work was to find such an empirical coefficient. The results of full-scale tests of several power GTUs and aviation GTEs were employed to obtain values of the temperature profile attenuation coefficient in the through-flow model for various span locations of airfoil rows. During the tests detailed radial-circumferential distributions of the gas temperature upstream of each of rows and downstream of the turbines were measured (in absolute motion for stator and in relative motion for rotor). The values of the attenuation coefficient for airfoil rows of the three front stages were obtained by means comparison of experimental and computed results. The experience shows that the attenuation coefficient is easily incorporated into the 2D gas-dynamic codes. This incorporation allows spanwise distributions of flow parameters to be predicted and the airfoil geometry and cooling mass flow to be chosen more correctly.
Life Prediction Method of CC and DS Ni Base Superalloys Under High Temperature Biaxial Fatigue Loading
Authors: Ogata Takashi , Sakai Takayuki
Published: February 2010

Polycrystalline conventional casting (CC) and directionally solidified (DS) Ni base superalloys are widely used as gas turbine blade materials. It was reported that surface of a gas turbine blade is subjected to biaxial tensile-compressive fatigue loading during start-stop operation based on finite stress analysis results. It is necessary to establish life prediction method of these superalloys under biaxial fatigue loading for reliable operation. In this study, the in-plane biaxial fatigue tests with different phase of x and y directional strain cycles were conducted on both a CC and a DS Ni base superalloys (IN738LC and GTD111DS) at high temperatures. The strain ratio, φ was defined as a ratio between x and y directional strains at 1/4 cycle and was varied from 1 to −1. In φ = 1 and −1, cracks propagated in both x and y directions in the CC supealloy. On the other hand, the main cracks of the DS superalloy propagated only in the x direction indicating failure resistance in the solidified direction is weaker than that in the direction normal to the solidified direction. Although biaxial fatigue life of the CC superalloy was correlated with conventional Mises equivalent strain range, that of DS superalloy was not. New biaxial fatigue life criterion, equivalent normal strain range for the DS superalloy was derived from iso-fatigue life curve on a principal strain plane defined in this study. Fatigue life of the DS superalloy was correlated with the equivalent normal strain range. Fatigue life of the DS superalloy under equi-biaxial fatigue loading was significantly reduced by introducing compressive strain hold dwell. Life prediction under equi-biaxial fatigue loading with the compressive strain hold was successfully made by the nonlinear damage accumulation model indicating that the proposed method can apply to life prediction of gas turbine blades under biaxial fatigue loading.
The Dynamic Influence of Crystal Orientation on a Second Generation Single Crystal Material for Turbine Buckets
Authors: Manetti Marco , Giovannetti Iacopo , Pieroni Nicola , Horculescu Horia , Peano Guido , Zonfrillo Giovanni , Giannozzi Massimo
Published: February 2010

High cycle fatigue is a factor that influence gas turbine buckets lifetime and it’s due to high frequency vibrations during service. Rotation and fluid flow around the blades cause static and dynamic stresses on the buckets row. For this reason the natural frequencies and HCF resistance evaluation are fundamental in the design phase of gas turbine engines in order to avoid resonance problems during service. Single crystal and directionally solidified superalloys shows anisotropic material properties, in particular single crystal can be modeled as orthotropic material in lattice directions for FEM simulations purposes. In this paper the influence of the lattice growth orientation, identified by two angles, on the natural frequencies of first stage bucket has been investigated. Six-sigma analysis has been performed in order to obtain a transfer function between lattice orientation and bucket vibration. The Design of Experiment (DoE) has been performed using FEA modal results on ten different vibration modes. The results obtained by FEA are verified by an experimental test on the real Heavy Duty MS5002 buckets.
Experimental Investigation of Non-Axisymmetrical Flow Control in a Low Speed Axial Compressor
Authors: Jiang Huabing , Lu Yajun , Yuan Wei , Li Qiushi
Published: February 2010

The non-axisymmetric feature of the compressor separated flow field should be considered when flow control technology is utilized to improve compressor performance. An experiment is performed to investigate the effectiveness of non-axisymmetric flow control using arc curve skewed slot casing treatment in the paper. A simplified non-axisymmetric excitation model is presented with variable circumferential excitation extent and location. FFT analysis results indicate that the frequency spectrum of the non-axisymmetric excitation is similar with that of the whole circumferential excitation. The non-axisymmetric excitation possesses the same dominate frequency, smaller amplitude and wider frequency bandwidth compared to the whole circumferential excitation. A simplified circumferential non-axisymmetric arc curve skewed slot casing treatment is utilized to perform non-axisymmetric excitation on the separated flow field of a low speed single stage axial compressor under both uniform and distorted inlet conditions. Experimental results indicate that the non-axisymmetric slotted casing treatment presents strong flow control capability, which could improve compressor efficiency, total pressure rise coefficient and stall margin. For the distorted inlet condition, the stall margin, total pressure rise and efficiency of the compressor are respectively improved by 47.4%, 12.7% and 0.7% compared to the solid casing, and the compressor efficiency is improved by 1.4% compared to the whole circumferential excitation. For uniform inlet condition, the non-axisymmetric excitation can improve compressor efficiency by 1.0% and 1.5% respectively compared to the solid casing and the whole circumferential excitation. The whole circumferential excitation can also improve the compressor total pressure rise coefficient and stall margin, on the contrary, it decreases compressor efficiency. As a result, the non-axisymmetric slotted casing treatment can achieve more excellent compressor performance than the whole circumferential excitation does. Experimental results also indicate that the circumferential extent and location of the non-axisymmetric excitation can influence the effectiveness of the non-axisymmetric excitation. The best compressor performance can be achieved only when the non-axisymmetric excitation is tuned to match the asymmetric compressor separated flow field. Analysis on the experimental results indicates that compressor efficiency improvement achieved with the non-axisymmetric excitation can not simply attribute to the flow loss reduction induced by fewer casing slots. The flow loss reduction within undistorted sector, the circumferential flow exchange and the dynamic response induced by the non-axisymmetric excitation, the unsteady coupling between the non-axisymmetric excitation and the separated flow field might be the key flow factors to influence the compressor flow field structure, and hence influence the compressor performance.
Preliminary Flutter Design Method for Supersonic Low Pressure Turbines
Authors: Meingast Markus , Kielb Robert E. , Thomas Jeffrey P.
Published: February 2010

The “Tie-Dye” (TD) method is a well-known preliminary flutter design method for subsonic low pressure turbine (LPT) blades. In this paper, a study of 2D mode shape sensitivity using the TD-method for supersonic exit Mach numbers is presented. Using a harmonic balance CFD method, TD maps displaying the critical reduced frequency for a range of pitching axis locations were created. The TD method was run on two geometrically different blades. Subsonically, the characteristic appearance does not change much over airfoil types. An even lesser amount of morphing can be observed between the different profiles in the supersonic range, than for the subsonic cases. Pure bending modes show a high sensitiviy to the actual bending direction. Therefore the single critical reduced frequency value criteria does not hold up for all cases. The method is applicable for supersonic exit flows, and is even more predictable and universal than for the subsonic cases.
Optimization of Turbocharger Ported Shroud Compressor Stages
Authors: Yin Junfei , Li Penny , Pees Stephane
Published: February 2010

With increasing low-end torque and high-power requirements, passenger vehicle applications need large map-width compressor-stages at high-pressure ratio (3.0 and above). Compressor stages in which wheels operate in a normal housing exhibit limitations in stability at high-pressure ratio and in maximal flow capacity. The application of a ported shroud typically improves the surge characteristics of a centrifugal compressor. In this paper, an optimisation procedure for ported-shroud compressor stages was developed based on Design Of Experiment (DOE) procedure. Two DOE procedures are used. The first one is used to optimize the port location, wheel exducer width and diffuser width; the second is used to optimise the housing volute throat area, diffuser width and diffuser outlet radius. The compressor-stage performance was obtained by using a commercial CFD package. After the first DOE, an experimental DOE with a reduced design space was carried out to obtain the optimised port location and wheel exducer width. After the second DOE and optimization, only most promising configurations were manufactured for tests. The DOEs’ procedures and results as well as the CFD results are discussed and analyzed in the paper. Finally, the relative difference between the CFD and tests are discussed. In comparison to the baseline ported-shroud housing, the final configuration has improved map width by 9%, an increased pressure ratio by 0.2 and a higher peak efficiency by about 1 point.
Synchronous Response to Rotor Imbalance Using a Damped Gas Bearing
Authors: Ertas Bugra H. , Camatti Massimo , Mariotti Gabriele
Published: February 2010

One type of test performed for evaluating bearings for application into turbomachinery is the synchronous bearing response to rotor imbalance. This paper presents rotordynamic tests on a rotor system using a 70mm diameter damped gas bearing reaching ultra-high speeds of 50,000 rpm. The main objective of the study was to experimentally evaluate the ability of the damped gas bearing to withstand large rotor excursions and provide adequate damping through critical speed transitions. Two critical speeds were excited through varying amounts and configurations of rotor imbalance, while measuring synchronous rotordynamic response at two different axial locations. The results indicated a well-damped rotor system and demonstrated the ability of the gas bearing to safely withstand rotor vibration levels while subjected to severe imbalance loading. Also, a waterfall plot was used to verify ultra high-speed stability of the rotor system throughout the speed range of the test vehicle. In addition to the experimental tests, a rotordynamic computer model was developed for the rotor-bearing system. Using the amplitude/frequency dependent stiffness and damping coefficients for the ball bearing support and the damped gas-bearing support, a pseudo-nonlinear rotordynamic response to imbalance was performed and compared to the experiments.
Experimental Investigation on the Effects of Unsteady Excitation Frequency of Casing Treatment on Transonic Compressor Performance
Authors: Tuo Wei , Lu Yajun , Yuan Wei , Zhou Sheng , Li Qiushi
Published: February 2010

The importance of the unsteady effects between casing treatment and rotor is still not clear. Experiments are conducted in a transonic compressor with arc skewed slot casing treatment configurations. The experimental results indicate that the unsteady excitation frequency due to slot number of casing treatment is one of the most important factors influencing compressor performance. And compressor performance can be overall enhanced through optimizing this unsteady excitation frequency. For the transonic compressor herein, peak efficiency, stall margin and the maximum flow mass can be improved by 0.17%, 19.86% and 0.81% respectively at near design rotating speed, which can reach up to 1.13%, 57.84% and 1.57% respectively at part design speed.
Load Capacity Measurements of Hydrostatic Bump Foil Bearing
Authors: Kumar Manish , Kim Daejong
Published: February 2010

A few years ago, a hydrostatic air foil bearing using compression springs as elastic foundation was firstly introduced by Kim and Park [1]. This paper presents recent experimental results on load capacity of a new hydrostatic air foil bearing made of corrugated bump foils. The new hydrostatic air foil bearing was designed with higher structural stiffness than the first design by [1]. A new test rig was also designed and constructed to measure load capacity of the bearing at higher speeds. The new test results indicate the hybrid operation has similar load capacity to that of hydrodynamic operation at high speeds due to dominance of hydrodynamic pressure. However, comparative tests at low speed (10,000 rpm) showed noticeable increase of load capacity in hydrostatic air foil bearing, manifesting effective hydrostatic levitation feature at low speeds.
Comparison Between Steady and Unsteady Double-Entry Turbine Performance Using the Quasi-Steady Assumption
Authors: Copeland Colin D. , Martinez-Botas Ricardo , Seiler Martin
Published: February 2010

The experimental performance evaluation of a circumferentially divided, double-entry turbocharger turbine is presented in this paper with the aim of understanding the influence of pulsating flow. By maintaining a constant speed but varying the frequency of the pulses, the influence of frequency was shown to play an important role in the performance of the turbine. A trend of decreasing cycle-averaged efficiency at lower frequencies was measured. One of the principal objectives was to assess the degree to which the unsteady performance differs from the quasi-steady assumption. In order to make the steady-unsteady comparison for a multiple entry turbine, a wide set of steady equal and unequal admission flow conditions were tested. The steady state data was then interpolated as a function of three, non-dimensional parameters in order to allow a point-by-point comparison with the instantaneous unsteady operation. As an average, the quasi-steady assumption generally under-predicted the mass flow and efficiency loss through the turbine, albeit the differences were reduced as the frequency increased. Out-of-phase pulsations produced unsteady operating orbits that corresponded to a significant steady state, partial admission loss, and this was reflected as a drop in the quasi-steady efficiency. However, these differences between quasi-steady in-phase and out-of-phase predictions were not replicated in the measured results, suggesting that the unequal admission loss is not as significant in pulsating flow as it is in steady flow.
Measurement of Structural Stiffness and Damping Coefficients in a Metal Mesh Foil Bearing
Authors: San Andre´s Luis , Chirathadam Thomas Abraham , Kim Tae-Ho
Published: February 2010

Engineered Metal Mesh Foil Bearings (MMFB) are a promising low cost bearing technology for oil-free microturbomachinery. In a MMFB, a ring shaped metal mesh (MM) provides a soft elastic support to a smooth arcuate foil wrapped around a rotating shaft. The paper details the construction of a MMFB and the static and dynamic load tests conducted on the bearing for estimation of its structural stiffness and equivalent viscous damping. The 28.00 mm diameter, 28.05 mm long bearing, with a metal mesh ring made of 0.3 mm Copper wire and compactness of 20%, is installed on a test shaft with a slight preload. Static load versus bearing deflection measurements display a cubic nonlinearity with large hysteresis. The bearing deflection varies linearly during loading, but nonlinearly during the unloading process. An electromagnetic shaker applies on the test bearing loads of controlled amplitude over a frequency range. In the frequency domain, the ratio of applied force to bearing deflection gives the bearing mechanical impedance, whose real part and imaginary part give the structural stiffness and damping coefficients, respectively. As with prior art published in the literature, the bearing stiffness decreases significantly with the amplitude of motion and shows a gradual increasing trend with frequency. The bearing equivalent viscous damping is inversely proportional to the excitation frequency and motion amplitude. Hence, it is best to describe the mechanical energy dissipation characteristics of the MMFB with a structural loss factor (material damping). The experimental results show a loss factor as high as 0.7 though dependent on the amplitude of motion. Empirically based formulas, originally developed for metal mesh rings, predict bearing structural stiffness and damping coefficients agreeing well with the experimentally estimated parameters. Note, however, that the metal mesh ring, after continuous operation and various dismantling and reassembly processes, showed significant creep or sag that resulted in a gradual decrease of its structural force coefficients.
Application of a Navier-Stokes Solver to the Study of Open Rotor Aerodynamics
Authors: Zachariadis Alexios , Hall Cesare A.
Published: February 2010

This paper establishes a proven computational approach for open rotor configurations that can be used as a basis for further studies involving open rotor aerodynamics and design. Many of the difficulties encountered in the application of computational fluid dynamics to an open rotor engine arise due to the removal of the casing that is present in conventional aeroengine turbomachinery. In this work, an advanced three-dimensional Navier-Stokes solver is applied to the open rotor. The approach needed to accurately capture the aerodynamics is investigated with particular attention to the mesh configuration and the specification of boundary conditions. A new three-step meshing strategy for generating the mesh and the most suitable type of far-field boundary condition are discussed. A control volume analysis approach is proposed for post-processing the numerical results for rotor performance. The capabilities of the solver and the applied methodology are demonstrated at both cruise and take-off operating conditions. The comparison of computational results with experimental measurements shows good agreement for both data trend and magnitudes.
An Absorbing Inlet Buffer Layer for Rotor Wake/Stator Time Domain Computations
Authors: Olausson Martin , Eriksson Lars-Erik
Published: February 2010

This paper presents a method that concerns how absorbing buffer layers can be used at the inlet of nonlinear rotor wake/stator computations using an URANS solver with chorochronic, time lag, periodic boundaries in order to avoid spurious reflections of acoustic waves. If a part of the inlet to the stator domain rotates with the wake at the same speed as the rotor, the wake is stationary in this rotating inlet zone, and a standard buffer layer method can be used in the rotating frame of reference without destroying the wake. The rotating inlet buffer layer should have the same periodicity as the rotor and a chorochronic, Fourier-based in time and tangential direction, blade row interface can then be used between the rotating domain and the stator domain. This new method, using a rotating inlet buffer layer, is compared to other absorbing inlet boundary conditions, for example the 1D type (axial characteristics) or 2D type (axial-tangential characteristics), for a realistic high bypass ratio stator vane geometry, considering tone noise generation from the impingement of rotor wakes on the stators.
A Three-Dimensional CFD Design Study of a Circulation Control Inlet Guide Vane for a Transonic Compressor
Authors: Gunter Sandra L. , Guillot Stephen A. , Ng Wing F. , Bailie S. Todd
Published: February 2010

A three-dimensional computational investigation was conducted to evaluate the performance of a circulation control inlet guide vane (IGV) designed for a transonic compressor test rig. The general configuration of the IGV is an uncambered airfoil designed to exploit the Coanda effect for flow turning through the use of a jet that exhausts along a curved trailing edge. Computational fluid dynamics (CFD) was used in conjunction with an optimization approach to design an IGV that balances performance potential with manufacturing cost and complexity. Optimization parameters include geometry specifications such as jet height and trailing edge radius, as well as operational parameters such as jet supply pressure and inlet Mach number. The potential for positive flow turning was shown for all geometries examined. Operational goals such as increased turning at lower off-design inlet Mach numbers were demonstrated, and an optimum configuration was established.
The Numerical and Experimental Characteristics of Multi-Mode Dry-Friction Whip and Whirl
Authors: Wilkes Jason C. , Dyck Benjamin J. , Childs Dara W. , Phillips Stephen G.
Published: February 2010

The nature of dry-friction whip and whirl is investigated through experimental and numerical methods. A test rig was designed and constructed to demonstrate and record the character of multi-mode dry-friction whip and whirl. These tests examined steady state whip and whirl characteristics for a variety of rub materials and clearances. A simulation model was constructed using tapered Timoshenko beam finite elements to form multiple-degree-of-freedom rotor and stator models. These models were reduced by component mode synthesis to discard high-frequency modes while retaining physical coordinates at the rub location to model rotor-stator interaction using a nonlinear contact model with Coulomb friction. Simulations were performed for specific test cases and compared against experimental data; these comparisons are favorable. Experimental data analysis showed multiple whirl and whip regions, despite claims of previous investigators that these regions are predicted analytically but not produced in simulations or experiments. Spectral analysis illustrates the presence of harmonic sidebands that accompany the fundamental whirl solution. These sidebands are more evident in whip and can excite higher-frequency whirl solutions.
Fan Root Aerodynamics for Large Bypass Gas Turbine Engines: Influence on the Engine Performance and 3D Design
Authors: Zamboni Giulio , Xu Liping
Published: February 2010

The exit flow field of the fan root of large turbofan engines defines the inlet conditions to the core compressor. This in turn could have significant impact to the performance of the core compressor. This study is aimed to resolve two related issues concerning the impact of the fan root flow on the core compressor performance: to establish the effect of an increased loss at the inlet on the engine specific fuel consumption (SFC) and to assess the effect of the radial distribution of the fan root flow on the engine performance. With understanding of these issues, the geometric parameters and design details which can produce a more uniform core flow at the exit of the fan stage module can be identified. The fan root flow is analysed with methods of different complexity and fidelity. A simple cycle analysis is used to assess the impact on engine SFC of a stagnation pressure deficit at the fan root; a throughflow code is used for the preliminary study of the curvature effect of the root flow path and 3D RANS CFD calculations are then used to simulate the flow path from the inlet of the fan to the first stage of the core compressor. The adequacy of the application of the numerical code in this case has been assessed and confirmed by the comparison with the experimental data for two rig configurations. The results of this study show that the flow at the fan hub region is very complex and dominated by 3D effects. The interaction of the secondary flow with real geometries, such as leakage flows, is found to have a strong detrimental effect on the core performance. The curvature of the hub end-wall is a key parameter controlling the fan root flow topology; it influences the strength of the secondary flow, the spanwise distribution of the flow and its sensitivity to leakage flow. With this understanding it is possible to redesign of the fan hub flow path to reduce the loss generation by a significant amount.
Response of Bladed Disks With Mistuned Blade-Disk Interfaces
Authors: Avalos Javier , Mignolet Marc P. , Soize Christian
Published: February 2010

This paper focuses on the determination of the effects on the bladed disk forced response of small variations (mistuning) in the blade-disk interface properties as may result from blade seating. A blade-interface-disk mean model is first developed that relies on both the Craig-Bampton approach and a local modeling of the interface. Then, both model and data uncertainties are introduced in this model using the nonparametric stochastic modeling approach. An example of application is presented that indicates a difference in physical behavior of a bladed disk with mistuned interfaces as compared to one with mistuned blade alone frequencies. Most notably, it is shown that at equal variability on the blade frequencies, the variations in blade-disk interface properties lead to a higher amplification factor.
Onset of 1/2X Vibration and Its Prevention
Authors: Yu John J.
Published: February 2010

This paper discusses real cases on three different machines where subsynchronous vibration occurred suddenly at a frequency exactly equal to one-half (1/2X) of the operational speed of 3600 rpm. In two cases, vibration amplitude increased from around 2 mils (51 μm) pp to over 12 mils (305 μm) pp, causing the machine to trip unexpectedly. The 1/2X vibration was even sustained during shutdown at speed below 3600 rpm after trip. Unlike other reported experimental results, shaft orbit measured by proximity probes was fairly circular and dominantly composed of the 1/2X component without significant components at multiple orders of the 1/2X. The onset of the subsynchronous 1/2X vibration was sometimes triggered by changes in bearing lube oil temperature and supply pressure, which would typically be believed to be caused by oil whirl that could occur at close to the 1/2X frequency. An upward shift in shaft centerline plot was observed to occur prior to the onset of the subsynchronous vibration. The 1/2X vibration was successfully prevented by changing bearing clearance or adjustment of bearing oil temperature and supply pressure. Parametric excitation analysis on 1/2X vibration is also given in this paper. The main purpose of this paper, unlike previously published papers on analytical or experimental results, is to show shaft orbital and centerline plots as well as spectrum data due to the 1/2X vibration, including effects of operating conditions in real rotating machines.
Eddy Current Damping: A Concept Study for Steam Turbine Blading
Authors: Laborenz Jacob , Siewert Christian , Panning Lars , Wallaschek Jo¨rg , Gerber Christoph , Masserey Pierre-Alain
Published: February 2010

In gas and steam turbine applications a common approach to prevent the blades from high cycle fatigue failures due to high vibration amplitudes is the usage of friction damping elements. Besides the intended amplitude reduction this procedure also features some possibly unwanted side effects like a shift in resonance frequencies due to stiffening effects caused by the contact. Thus, as an alternative an eddy current based non-contacting damping concept for the application in turbo machinery is investigated. In this paper two different types of eddy current dampers are considered. Theoretical models for both are established by applying electromagnetic-mechanical theory. The theoretical models are compared to forced response measurements that are performed at a stationary test rig.
Static Normal Stress Influence in Friction Damping of Blade Attachments
Authors: Alonso Roberto , Marquina Francisco J. , Coro Armando , Gutie´rrez Alberto
Published: February 2010

It is well known that friction is really important to reduce amplitudes of vibration of rotor blades. Several approaches based on the classical Coulomb friction law have been used in order to model the friction damping at those interfaces, but their results are not accurate enough for those cases with small displacements and high normal loads. A more accurate method has been developed (InTerPart MIcroslip COntact method in [1]) to represent the damping introduced by these kind of friction sources. An improvement of this method has been made taking into account a more-in-depth study of the influence of normal stresses in those contacts areas under high normal stresses and small displacements (using the blade attachment friction source as reference). The paper includes a detailed study of the sensitiveness of different blade attachments to different normal stress distribution along the contact face, and the influence of this distribution in damping results. Experimental results are also presented to make comparison with simulation ones. These experimental results have been obtained from the test rig used in case 3 ([1]), but using different attachment geometries under the same conditions.
Numerical Investigation of Unsteady Blade Row Interactions With Leakage Flow in Steam Turbines
Authors: Fakhari Keramat , Hofbauer Thomas , Weber Anton
Published: February 2010

This paper focuses on the interaction of labyrinth seal leakage flows within two stages of a HP and an IP steam turbine. Numerical studies have been carried out with the DLR in-house code TRACE [1] to show the impact of the labyrinth seal leakage flow on the total loss generation in both steady and time accurate simulations. CFD results are verified by the in-house 2D through-flow method of Siemens Energy. The investigations are divided into five steps: 1. Real gas effects, 2. Steady simulations of the core flow alone and its interaction with the cavity flow to provide insights about loss production contributed by the mixing process of the re-entering leakage flow into the main flow, 3. Understanding and modeling of unsteady phenomena within such interacting flows, 4. Effects of reduction of the axial distance between the two stages on the mixing process in time accurate simulations. 5. Comparison of blade loads calculated by Siemens’ CAE tools and predicted by TRACE.
Testing and Calibration Procedures for Mistuning Identification and Traveling Wave Excitation of Blisks
Authors: Holland Darren E. , Filippi Sergio , Castanier Matthew P. , Ceccio Steven L. , Epureanu Bogdan I.
Published: February 2010

In this work, an integrated testing and calibration procedure is presented for performing mistuning identification (ID) and traveling wave excitation (TWE) of one-piece bladed disks (blisks). The procedure yields accurate results while also being highly efficient and is comprised of three basic phases. First, selected modes from a tuned blisk finite element model are used to determine a minimal set of measurement degrees of freedom (and locations) that will work well for mistuning ID. Second, a testing procedure is presented that allows the mistuning to be identified from relatively few vibration response measurements. A numerical validation is used to investigate the convergence of the mistuning ID results to a prescribed mistuning pattern using the proposed approach and alternative testing strategies. Third, a method is derived to iteratively calibrate the excitation applied to each blade so that differences among the blade excitation magnitudes can be minimized for single blade excitation, and also the excitation phases can be accurately set to achieve the desired traveling wave excitation. The calibration algorithm uses the principle of reciprocity and involves solving a least squares problem to reduce the effects of measurement noise and uncertainty. Because the TWE calibration procedure re-uses data collected during the mistuning ID, the overall procedure is integrated and efficient.
Study on Stabilities of Rotor-Bearing Systems With Different Types of Couplings
Authors: Zhao Guang , Liu Zhan-sheng , Wang Yong-liang , Zhang Jin-feng
Published: February 2010

Nonlinear dynamic model of gear coupling is derived, dynamic equations of rotor-bearing systems connected by rigid coupling, gear coupling and flexible coupling are established based on finite element analysis, stability simulations and experiments are also performed. Simulation and experiment results show coupling type have important influence on stability of rotor-bearing system, instabilities of rotor-bearing systems coupled through rigid coupling and flexible coupling are caused by oil whirl or oscillation. Simulation result indicates instability of rotor-gear coupling-bearing system is induced by oil whirl or oscillation, however, experiment implies that the instability caused by self-oscillation of gear coupling which is earlier than oil oscillation caused. Threshold speed of stability of rigid coupling linked is highest, while gear coupling linked is lowest. This research results can provide important criterions for design and choosing of couplings and stable operation of rotor-coupling-bearing system.
Optimization of Variable Stator’s Angle for Off Design Compression System Using Streamline Curvature Method
Authors: Shadaram Abdollah , Fathi Alireza , Azizi Ruhollah
Published: February 2010

In this study, an automated optimization tool for angel of variable stators in multistage compressors has been developed. Performance of the compressor is estimated using FORTRAN program coding based on streamline curvature method. Genetic algorithm is used to handle optimization processes. To demonstrate feasibility of the present method, a 10-stage compressor was optimized to maximize its total pressure ratio of operating point in off-design conditions. The variable geometries that were studied in this paper are: (1) VIGV; (2) VIGV and first row variable stator; (3) VIGV, first and second rows variable stator.
Effects of Tip Clearance on Unsteady Flow Characteristics in an Axial Turbine Stage
Authors: Sun Hao , Li Jun , Feng Zhenping
Published: February 2010

The clearance between the rotor blade tip and casing wall in turbomachinery passages induces leakage flow loss and thus degrades aerodynamic performance of the machine. The flow field in turbomachinery is significantly influenced by the rotor blade tip clearance size. To investigate the effects of tip clearance size on the rotor-stator interaction, the turbine stage profile from Matsunuma’s experimental tests was adopted, and the unsteady flow fields with two tip clearance sizes of 0.67% and 2.00% of blade span was numerical simulated based on Harmonic method using NUMECA software. By comparing with the domain scaling method, the accuracy of the harmonic method was verified. The interaction mechanism between the stator wake and the leakage flow was investigated. It is found that the recirculation induced by the stator wake is separated by a significant “interaction line” from the flow field close to the suction side in the clearance region. The trend of the pressure fluctuation is contrary on both sides of the line. When the stator wakes pass by the suction side, the pressure field fluctuates and the intensity of the tip leakage flow varies. With the clearance size increasing, the “interaction line” is more far away from the suction side and the intensity of tip leakage flow also fluctuates more strongly.