Asymmetric Blade Research Articles

G171012 非対称性回転翼を持つユネイト型風車([G171-01]産業・化学機械と安全部門,一般セッション(1))

G171012 非対称性回転翼を持つユネイト型風車([G171-01]産業・化学機械と安全部門,一般セッション(1))

A numerical investigation of new film cooling hole configuration at the leading edge of asymmetrical turbine blade: part A

The focus of the first part of this numerical study is to investigate the effects of two new configurations: (1) slot with cylindrical end and (2) slot with median cylindrical hole, generated by the combination between two film cooling configurations: cylindrical hole and uniform slot. Computational results are presented for a row of coolant injection holes on each side of an asymmetrical turbine blade model near the leading edge. For each configuration, three values of the radius are taken: R = 0.4, R = 0.8 and R = 1.2. The six cases simulations, thus obtained, are conducted for the same density ratio of 1.0 and the same inlet plenum pressure. A new parameter, Rc, is defined to measure the rate of blade coverage by the film cooling. Results show that, at the pressure side; for the two new configurations, the six studied cases exceed the case baseline in cooling effectiveness term with the best result obtained for R = 0.8 (case 2). For the suction side, only configurations with R = 0.4 (cases 1 and 4) provide an increase of film effectiveness compared to the case baseline. The following configuration: Cases 1 or 4 at the suction side and case 2 at the pressure side, gets the best thermal protection because of their higher coverage and strong cooling effectiveness.

FIRST REPORT OF GRAPEVINE DEFORMATION VIRUS AND GRAPEVINE ANATOLIAN RING SPOT VIRUS IN IRAN

Viral diseases are major limiting factors for grapevine (Vitis vinifera) production in northwest Iran, in the vineyards of which samples were collected from vegetating symptomatic plants dur- ing summer 2010. Total nucleic acid (TNA) was extracted from the leaves of 137 vines by the silica capture method and used as templates for RT-PCR using random hexamer primers. PCR frag- ments 371 and 425 bp in size were amplified using two pairs of primers for the specific recognition of Grapevine deformation virus (GDefV) and Grapevine Anatolian ringspot virus (GARSV), respectively (Digiaro et al., 2007). A GDefV-specific 371 bp DNA fragment was amplified from 1 of the 137 samples. The vine infected by this virus displayed distorted and mottled leaves with asymmetric blades, irregular branching of the canes and short internodes, as reported from Turkey (Gokalp et al., 2003). A GARSV-specific 425 bp DNA fragment was amplified from an- other of the 137 vines, which showed distorted and mottled leaves, asymmetric blades and chlorotic spots, i.e. symptoms that do not correspond to those shown by Turkish vines affected by the same virus (Cigsar et al., 2003). Such diverse symptomatology may be accounted for by differences in the genotype of GARSV isolates, or in grapevine cultivars, or a combination of both. On the basis of these data, we conclude that GDefV and GARSV are present in Iran, from where they are reported for the first time. Both viruses were discovered in Turkey in 2003 (Gokalp et al., 2003; Cigsar et al., 2003) but have not been found elsewhere.

Instability zones for isotropic and anisotropic multibladed rotor configurations

Helicopter ground resonance is an unstable dynamic phenomenon which can lead to the total destruction of the aircraft during take-off or landing phases. The earliest research in this domain was carried out by Coleman and Feingold during the decade of 60s. The instability was predicted by using classical procedures once the rotor was considered as isotropic, consequently, the periodic equations of motion could be simplified to a system with constant coefficients by introducing a change of variables, known as the Coleman Variable Transformation. The goal of the present work is to further comprehend the phenomenon and the influence of the anisotropic properties of rotors by analyzing the periodic set of equations of motion. For this, Floquet's Theory (Floquet's Method — FM) is used. The analysis for predicting the ground resonance phenomenon in isotropic and anisotropic rotor configurations is explored. The conclusions lead to verify the appearance of bifurcation points depending on the anisotropic characteristic present in the rotor. The temporal response analysis in the motion of helicopter with one asymmetric blade at unstable regions highlighted the presence of non symmetric rotor deformation shapes.

NACA0015익형을 가지는 로터 깃 끝와류의 후류유동구조

대칭익형 단면을 가지는 모형 깃 끝와류의 후류유동구조의 전개과정을 관찰하기 위하여 2차원 LDV 시스템을 이용하여 끝와류의 회전성분과 축성분을 상평균 기법으로 측정하였다. 비대칭익 로터 깃의 특징에 비하여 대칭익 로터깃의 끝와류는 <TEX>$27^{\circ}$</TEX> 부근까지 성장 과정이 진행되어 다소 늦게 형성되었으며 그 이후부터 상대적으로 완만하게 확산모드가 진행되었다. 회전성분은 실험이 진행된 <TEX>$360^{\circ}$</TEX> 까지 Vatistas의 n=2모델에 우수한 접근성을 보이면서 자기상사성을 갖는 것으로 관찰되었고 축방향성분은 비대칭익에 비하여 훨씬 강한 세기로 나타나면서 정규분포 성향을 나타내었다. 이들의 결과들은 대칭익의 경우 로터의 추력 발생면에서 끝단손실이 상대적으로 큰 것으로 확인이 되었다. Evolution of tip vortex generated by a model rotor blade which has a symmetric blade section has been investigated by use of the laser doppler anemometry. Swirl and axial velocity components of tip vortex were measured by the phase averaging technique within one revolution of a rotor blade. It was found that tip vortex becomes matured until 27 degrees and diffuses afterwards with diffusing rate becoming slower compared to the case of the asymmetric blade section, but the tip loss was expected to become more substantial. Swirl velocity components were well fit to n=2 model of Vatistas within measured wake ages, showing the self-similarity exists for the swirl velocity components. The axial components were followed with Gaussian profiles, but had much higher peak values than those of the symmetric blade section.

Numerical investigation of the influence of incidence angle on asymmetrical turbine blade model showerhead film cooling effectiveness

The influence of various incidence angles on film cooling effectiveness of an axial turbine blade cascade with leading edge ejection from two rows of cooling holes is numerically investigated. The rows are located in the vicinity of the stagnation line. One row is located on the suction side and the other one is on the pressure side. The predicted pressure field for various blowing ratios (M = 0.7, 1.1 and 1.5) is compared with available experimental results at the design condition. Moreover, the effect of various incidence angles (−10°, −5°, 0°, 5° and 10°) at three blowing rates is investigated by analyzing the results of both laterally averaged and area averaged values of adiabatic film cooling effectiveness. Numerical results indicate that the incidence angle can strongly affect the thermal protection of the blade at low blowing ratio but becomes less dominant at high blowing ratio. In fact, for the low blowing ratio, a small change in the incidence angle that relates to the design condition can deeply affect the thermal protection of the blade, which is evident from the laterally and area averaged film cooling effectiveness distributions.

K‐space undersampling in PROPELLER imaging

PROPELLER MRI (periodically rotated overlapping parallel lines with enhanced reconstruction) provides images with significantly fewer B(0)-related artifacts than echo-planar imaging (EPI), as well as reduced sensitivity to motion compared to conventional multiple-shot fast spin-echo (FSE). However, the minimum imaging time in PROPELLER is markedly longer than in EPI and 50% longer than in conventional multiple-shot FSE. Often in MRI, imaging time is reduced by undersampling k-space. In the present study, the effects of undersampling on PROPELLER images were evaluated using simulated and in vivo data sets. Undersampling using PROPELLER patterns with reduced number of samples per line, number of lines per blade, or number of blades per acquisition, while maintaining the same k-space field of view (FOV(k)) and uniform sampling at the edges of FOV(k), reduced imaging time but led to severe image artifacts. In contrast, undersampling by means of removing whole blades from a PROPELLER sampling pattern that sufficiently samples k-space produced only minimal image artifacts, mainly manifested as blurring in directions parallel to the blades removed, even when reducing imaging time by as much as 50%. Finally, undersampling using asymmetric blades and taking advantage of Hermitian symmetries to fill-in the missing data significantly reduced imaging time without causing image artifacts.

Low-Noise Design for Fans. Blade Arrangements for Reducing the Blade Passing Tones and Minimizing the Unbalanced Forces of Rotors.

This paper describes a new design method for electric fans not only to reduce the blade passing frequency (BPF) noise but also to minimize the unbalanced forces of rotors. For the suppression of BPF level, the fans with unequally spaced blades have been proposed. Such fans, however, are likely to cause unbalanced vibrations by the asymmetric blades. In this paper, the relations between the unbalanced forces of rotors and the blade arrangements are discussed, and the design methods for minimizing the unbalanced forces are proposed. Furthermore, the condition for realizing completely balanced fans is derived.

Performance of a Gas Dispersion Impeller with Vertically Asymmetric Blades

Gas dispersion impellers, such as the Rushton turbine and the more recent concave blade turbines, all feature blades that are symmetric with respect to the plane of the disc. This despite the fact that the gas usually enters from the bottom, and thus causes a flow pattern that is distinctly asymmetric. This article discusses the performance of a gas dispersion impeller with blades that are vertically asymmetric, i.e. the blade shape above the disk is different from the shape below the disk. It is shown that this impeller has a gassed power curve that is flatter than that of other impellers. Furthermore, it can disperse more gas before flooding than the impellers with symmetric blades.

The Application of Advanced PDC Concepts Proves Effective in South Texas

Summary Over the years, a variety of problems with polycrystalline diamond compact (PDC) bit design and application has been documented, with "bit whirl" being identified as the cause of many inherent problems. The goal of most PDC manufacturers, and the subject of this paper, is development of a better-performing, "whirl-resistant" PDC bit design. Similarly, the goal for most operators is the lower cost resulting from effective application of such bits. Toward those ends, a cooperative development effort between operators and a manufacturer was undertaken to apply advanced concepts effectively to the design, manufacture, and application of a new series of PDC bits in south Texas. Adoption of design concepts, such as force-balanced cutting structures, asymmetric blade layouts, spiral blade designs, and tracking cutter arrangements, proved effective in countering the destructive effects of bit whirl, and allowed PDC bits to be used in harder formations. Summaries of both operational and economic performance confirm the success of the undertaking.

Transmaxillosphenoidal approach to tumors invading the medial compartment of the cavernous sinus.

A transmaxillosphenoidal approach was used to remove sellar tumors invading the cavernous sinus. This procedure, a widening of the standard transsphenoidal approach to the sella turcica, uses the sublabial or transnasal route in which the medial wall of the maxillary sinus is laterally dislocated. This method provides good exposure of the prominences of bone above the carotid artery which lies on the posterolateral wall of the sphenoid sinus. This bone area is the key to opening the cavernous sinus inferomedially and removing lesions within its medial compartment. The inferomedial approach takes an entirely extracerebral route so that tumors invading the cavernous sinus through its medial wall are approached inferomedially following the direction of tumor growth. It also allows direct visualization of the intracavernous carotid artery during tumor removal, thus sparing the cranial nerves, which run on the opposite side. Adequate surgical exposure of a pituitary adenoma is achieved with a custom-made sphenoidal retractor with asymmetric blades, the shorter blade holding aside the thin medial wall of the maxillary sinus. Between October, 1989, and July, 1993, 11 patients with tumors invading the cavernous sinus underwent surgery via this approach; 10 had pituitary adenomas and one had a craniopharyngioma. Eight tumors were treated by primary operation: four tumors were totally and four subtotally (> 80%) removed; one tumor already operated on elsewhere was totally removed; and of two tumors already operated on and irradiated, one was subtotally removed and the other only partially (approximately 40%) removed owing to marked postirradiation scarring. None of the patients suffered permanent cranial nerve deficit and all but one showed marked clinical improvement.

Altered Middle Lobe Shape of Leaf Permits Rapid Diagnosis of Grapevine Fanleaf in Grapevine cv. St. George

When potted plants of cv. St. George infected with grapevine fanleaf virus (GFV) were kept under the temperature conditions of 28/23C (day/night) or 20/17C, the newly developed leaves did not show typical symptoms of GFV such as wide petiole sinus, asymmetrical blade shape and leaf blades assuming the shape of a fan until 50 days after sprouting. The denticulation of the margins of the leaf blades on infected plants also showed almost no difference from those of healthy plants during the 50 days. However, the middle lobe cusps of these leaves on the infected plants were very acute after the above incubation period, and clearly different from those of healthy plants. The symptoms appeared faster under the higher temperature condition of 28/23C than under the lower temperature condition of 20/17C. Sharpening ratios for the cusps of the middle lobes of infected and healthy leaves were compared. Infected plants were indicated by ratios exceeding 2.6 in the 50 days period. On the other hand, healthy plants were indicated by ratios less than 2.6. A sharpening ratio of 2.6 was converted into a value of 42.4 degrees for the angle of the middle lobe cusp of a leaf. Grapevine fanleaf can be rapidly diagnosed in cv. St. George within a period of 50 days after sprouting on the basis of the following criteria. At temperatures of 28/23C, values below 42.4 degrees for the angle of the middle lobe cusps of three successive leaves from the fourth to the sixth in leaf order from the base of a shoot indicate infection with grapevine fanleaf virus. The measurement of this angle is easily made by using a magnifying glass with a V mark of 42.4 degrees, or with the naked eye.

Stress state of a three-layer, shaped, asymmetric blade structure for a centrifugal turbomachine

Stress state of a three-layer, shaped, asymmetric blade structure for a centrifugal turbomachine

Study on the Generating Method of Hypoid Gears : with the Spiral Bevel Gear Generator in Kyushu Univ. by the Gleason's No. 0 Cutter only

Hypoid gears have asymmetric tooth profile. In order to cut a hypoid pair, cutters with asymmetric blades must be used, otherwise the cutter shaft must be tilted as much as the amount of asymmetricity. For the small quantity production it is desirable and convenient to use the Gleason's No. 0 cutter. In the previous report the author theoretically showed that the hypoid gear could be cut by the No. 0 cutter without tilting its shaft. In this paper he carries out the experimental check of the theory using the spiral bevel gear generator installed in Kyushu University. The experimental results show that accurate pairs with good tooth bearing can be cut and ground without any trial work.

Experimental Determination of the Centre-of-Flexure and Centre-of-Torsion Co-Ordinates of an Asymmetrical Aerofoil Cross-Section

The differential equations of motion (1)† of a vibrating cantilever blade contain coupling terms dependent upon the co-ordinates of the centre-of-flexure relative to the centroid of the blading cross-section. Complete solution of the equations, therefore, requires a knowledge of the co-ordinates. The general theoretical problem of flexure of a cantilever blade has not yet been solved but a solution (2) based on St. Venant's theory of torsion is available for the case of a blade of uniform cross-section with symmetry about one of its principal axes but asymmetrical about the other. The accuracy of the theory is confirmed by experiment (***3). The present paper describes an extension of the flexure experiment to the case of a blade of asymmetrical aerofoil cross-section, the most usual form of cross-section found in turbine and compressor blading. For a cross-section with symmetry about one of its principal axes but asymmetrical about the other it has been shown by reasoning and confirmed by experiment (3) that, providing the root fixing is encastré, the centre-of-flexure is coincident with the centre-of torsion. A second experiment is presently described in which the centre-of-torsion coordinates are determined when the cross-section is asymmetric. Close agreement is shown to exist between the co-ordinates of the centre-of-torsion and those of the centre-of-flexure of the asymmetrical aerofoil cross-section blade.

Adzes and adze-like implements from eastern Australia

Occasional edge-ground adzes have been recorded from scattered localities in Australia, and their existence as a type has been referred to by the author (1939, 4-5, figs. 2 and 8; 1940b, 227, fig.), and Noone (1943,274-5, 279, figs. 10-12, 30-31). In this paper is given a description of the examples in the collection of the Australian Museum. The chief characteristic of the adze is the asymmetrical blade with its edge above or below the middle; the upper facet is usually rounded, and the lower facet varies from convex to concave and is often at a steep angle. Such implements are hafted, with the blade at a right angle to the haft. The body of the adze varies widely in shape and in Oceania embraces examples with round, lenticular, rectangular, trapezoid, or triangular section.

32. Radford's Straight Long Forceps with Asymmetrical Blades.

32. Radford's Straight Long Forceps with Asymmetrical Blades.