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Article
Publication date: 1 September 1995

K. Renap and J.P. Kruth

Most stereolithography systems use a blade to accomplish the recoating of the part being built with a new layer of resin. States the problems associated with this…

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Abstract

Most stereolithography systems use a blade to accomplish the recoating of the part being built with a new layer of resin. States the problems associated with this technique and describes experiments conducted to determine how recoating parameters should be controlled. Differentiates between recoating over an entirely solid substrate and over one consisting of solid and liquid, i.e. the “trapped volume” condition. Discusses parameter control for both of these conditions. Concludes that recoating is an important part of the stereolithography process which must be optimized to ensure accuracy of prototype parts.

Details

Rapid Prototyping Journal, vol. 1 no. 3
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 20 November 2007

Lingjiu Zhou, Zhengwei Wang, Ruofu Xiao and Yongyao Luo

Some comparison of unsteady flow calculation and the measured stress showed that the dynamic stresses in blades are closely related to hydraulic instability. However, few…

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1011

Abstract

Purpose

Some comparison of unsteady flow calculation and the measured stress showed that the dynamic stresses in blades are closely related to hydraulic instability. However, few studies have been conducted for the hydraulic machinery to calculate dynamic stresses caused by the unsteady hydraulic load. The present paper aims to analyse the stresses in blades of a Kaplan turbine.

Design/methodology/approach

By employing a partially coupled solution of 3D unsteady flow through its flow passage, the dynamic interaction problem of the blades was analyzed. The unsteady Reynolds‐averaged Navier‐Stokes equations with the SST κω turbulence model were solved to model the flow within the entire flow path of the Kaplan turbine. The time‐dependent hydraulic forces on the blades were used as the boundary condition for the dynamics problem for blades.

Findings

The results showed that the dynamic stress in the blade is low under approximately optimum operating conditions and is high under low‐output conditions with a small guide vane opening, a small blade angle and a high head.

Research limitations/implications

It is assumed that there is no feedback of blade motion on the flow. Self‐excited oscillations are beyond the scope of the present paper.

Originality/value

The authors developed a code to transfer the pressure on blades as a boundary condition for structure analysis without any interpolation. The study indicates that the prediction of dynamic stress during the design stage is possible. To ensure the safety of the blades it is recommended to check the safety coefficient during the design stage for at least two conditions: the 100 percent output with lower head and the 50 percent output with the highest head.

Details

Engineering Computations, vol. 24 no. 8
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 23 February 2015

Manoj Kumar Chaudhary and Anindita Roy

A small wind turbine blade was designed and optimized in this research paper. The blade plays an important role, because it is the most important part of the energy…

Abstract

A small wind turbine blade was designed and optimized in this research paper. The blade plays an important role, because it is the most important part of the energy absorption system. Consequently, the blade has to be designed carefully to enable to absorb energy with its greatest efficiency. The main objective of this paper is to optimized blade number and selection of tip speed ratio corresponding to the solidity. The power performance of small horizontal axis wind turbines was simulated in detail using blade element momentum methods (BEM). In this paper for wind blade design various factors such as tip loss, hub loss, drag coefficient, and wake were considered. The design process includes the selection of the wind turbine type and the determination of the blade airfoil, twist angle distribution along the radius, and chord length distribution along the radius. A parametric study that will determine if the optimized values of blade twist angle and chord length create the most efficient blade geometry. The 3-bladed, 5-bladed and 7-bladed rotor achieved maximum values of Cp 0.46, 0.5 and 0.48 at the tip speed ratio 7, 5 and 4 respectively. It was observed that using BEM theory, maximum Cp varied with strongly solidity and weakly with the blade number. The studies showed that the power coefficient increases upto blade number B = 5, while the blade number if increased above 5 then the power coefficient decreases at operating pitch angle equal to 3°. Highest Cp would have solidity between 4% to 6% for number of blade 3 and design point tip speed ratio of about "7". Highest Cp would have solidity ranging from 5% to 10% for number of blade 5 and 7 and design point tip speed ratio of about 5 and 4 respectively.

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World Journal of Engineering, vol. 12 no. 1
Type: Research Article
ISSN: 1708-5284

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Article
Publication date: 22 June 2012

Haijun Zeng and Youchao Sun

The purpose of this paper is to introduce parametered modeling technology for the civil aircraft engine fan blade, to design the fan blade rapidly and accurately.

Abstract

Purpose

The purpose of this paper is to introduce parametered modeling technology for the civil aircraft engine fan blade, to design the fan blade rapidly and accurately.

Design/methodology/approach

The entire fan blade consists of three crucial parts: blade airfoil, tenon and airfoil root. Blade airfoil with a free surface feature is formed through the blade profiles from the hub to tip in the radial direction. The non‐uniform rational basis spline (NURBS) is utilized to describe the blade profile. The geometry model of fan blade tenon is generated by extruding the sketch of the tenon. And the fillet section is designed to achieve the smooth transition of the up surface and the bottom surface of the blade root. Furthermore, the fan blade of a typical commercial engine is redesigned by the above method.

Findings

The stress analysis of the fan blade shows that the fan blade model designed in this work is reasonable.

Originality/value

The parametered fan blade model is presented on the basics of feature‐based modeling technology.

Details

Multidiscipline Modeling in Materials and Structures, vol. 8 no. 1
Type: Research Article
ISSN: 1573-6105

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Article
Publication date: 1 October 1999

Marc P. Mignolet, Alejandro Rivas‐Guerra and Brandon LaBorde

The objective of the present article is to provide a progress report on, and highlight, some ongoing efforts regarding the available techniques for the direct (i.e. not…

Abstract

The objective of the present article is to provide a progress report on, and highlight, some ongoing efforts regarding the available techniques for the direct (i.e. not based on Monte Carlo simulations) prediction of the distribution of the forced response of turbomachinery bladed disks that exhibit small blade‐to‐blade variations in their structural properties (random mistuning). The focus of this effort is on the statistical distributions of the amplitudes of response of a typical blade at a given frequency (level 1), of the maximum responding blade on the disk at a given frequency (level 2), and finally of the maximum responding blade on the disk over a frequency sweep (level 3). When appropriate, emphasis will be placed on the reliability of these techniques as a function of the blade‐to‐blade coupling strength.

Details

Aircraft Engineering and Aerospace Technology, vol. 71 no. 5
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 18 April 2017

Lingjiu Zhou, Meng Liu, Zhengwei Wang, Demin Liu and Yongzhi Zhao

This study analyzes the blade channel vortices inside Francis runner with a particular focus on the identification of different types of vortices and their causes.

Abstract

Purpose

This study analyzes the blade channel vortices inside Francis runner with a particular focus on the identification of different types of vortices and their causes.

Design/methodology/approach

A single-flow passage of the Francis runner with refined mesh and periodic boundary conditions was used for the numerical simulation to reduce the computational resource. The steady-state Reynolds-averaged Navier–Stokes equations closed with the k-ω shear–stress transport (SST) turbulence model were solved by ANSYS CFX to determine the flow field. The vortices were identified by the second largest eigenvalue of velocity.

Findings

Four types of vortices were identified inside the runner. Three types were related to the inlet flow. The last one (Type 4) was caused by the reversed flow near the runner crown and had the lowest pressure inside the core near the runner outlet. Thus, in the blade channel vortex inception line, Type 4 vortex would appear earlier than the other three ones. Besides, the Type 4 vortex emerged from the crown and shed toward the blade-trailing edge. And its location moved from near the crown down to near the band when the unit speed increased or unit discharge decreased.

Research limitations/implications

Although the refined mesh was used and the main vortices in the Francis runner were well predicted, the current mesh is not enough to accurately predict the lowest pressure in the channel vortex core.

Practical/implications

This knowledge is instructive in the runner blade design and troubleshooting related to the channel vortex.

Originality/value

This study gives an overview of the main observed blade channel vortices and their causes, and points out the important role the reversed flow plays in the formation of blade channel vortices. This knowledge is instructive in the runner blade design and troubleshooting related to blade channel vortices.

Details

Engineering Computations, vol. 34 no. 2
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 February 1939

Fig. 2 shows a blade carried by a head of the kind described in Specification. 435,818. The root of the blade comprises a steel tube 32 provided with a fairing 33, Fig. 3…

Abstract

Fig. 2 shows a blade carried by a head of the kind described in Specification. 435,818. The root of the blade comprises a steel tube 32 provided with a fairing 33, Fig. 3, which is a sliding fit over supporting arm 30 and is rotatable to vary the blade pitch. The outer end of tube 32 is secured to blade spar proper 34. The blade is anchored to the hub by a torsionally resilient tie rod 35 screwed at its outer end into spar 34 and secured by a nut and tapered collet device 36. At the inner end rod 35 is secured into arm 30 and secured by a screwed plug and taper pin assembly 37. The blade is of lancet shape and is arranged so that axis B—B of the spar intersects the flapping and drag pivot axes and in the normal mean position of the blade intersects the axis of rotation at the mean centre of oscillation F of the blade pitch control gear. The masses and aerofoil sections of the blade are such that the centres of mass and mean centres of pressure of all the sections lie along axis B—B. The construction of the blade is such that the “ neutral torsional axis,” defined as the locus of points in the chord at which an applied vertical thrust produces equal degrees of flexure of the leading and trailing edges, is at or slightly in front of the axis B—B. In the latter case increase in lift tends to decrease the angle of incidence of the blade as is shown in Fig. 6 wherein C is the centre of pressure, L the lift force, and 0 the neutral torsional axis. In either arrangement aerofoil sections having a stable centre of pressure travel may be employed. In order to bring the neutral axis forward, the nose portion of the blade, in the case of hollow stressed‐skin construction, may be reinforced by additional layers of material or may comprise material having a higher modulus of elasticity than the remainder. In order to compensate the resulting forward movement of the centre of mass, a small amount of non‐structural mass may bo incorporated in the blade. In one form in which the neutral torsional axis is coincident with the B—B axis, the blade comprises a spar and an aerofoil‐shaped fairing of material of the synthetic resin or plastic group of which the modulus of elasticity is so much lower than that of the spar as not to relieve the latter appreciably of its loads. Fig. 7 shows the method of construction of such a blade comprising a steel spar having a moulded fairing. A first mould comprises upper and lower dies 1, 2 and an interposed core 3. Spar 4 is located by pegs 5 and by rows of spaced raised points 6, and is also fluted to key the moulding. Steel wires 8, 9 are strung in the spaces forming the leading and trailing edges. The blade is formed with a solid nose and with internal ribs 10 and webs 11, the latter being produced by slots formed in the upper side of core die 3. After moulding as shown, dies 2 and 3 are removed, pegs 5 cut off, countersunk, and plugged, Fig. 9, and a lower die 13 placed in position and heat applied to unite the lower skin to ribs 10 and to seal the trailing edge. A suitable plastic material is stated to be “ plastic glass.”

Details

Aircraft Engineering and Aerospace Technology, vol. 11 no. 2
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 October 1944

In a variable‐pitch propeller in combination, a hub, a plurality o£ blades arranged on said hub for adjustment about their longitudinal axis, means displaceable by the…

Abstract

In a variable‐pitch propeller in combination, a hub, a plurality o£ blades arranged on said hub for adjustment about their longitudinal axis, means displaceable by the action of a hydraulic pressure medium and operatively connected to said blades, an operation of said means effecting an adjustment of the blades and thus a variation of the propeller pitch, a source of hdyraulic pressure supplying liquid under pressure to said blade‐adjusting means, an additional source of hydraulic pressure also adapted to supply liquid under pressure to said blade‐adjusting means, a member determining the magnitude of the hydraulic pressure acting upon the blade adjusting means, a governing member operated by the action of centrifugal forces and a change‐over member, both these members controlling the distribution of the hydraulic pressure medium to said blade‐adjusting means, a further member adapted to interrupt the supply of hydraulic pressure medium to said blade‐adjusting means when a limit of a normal predetermined pitch range is reached, auxiliary valve means for the hydraulic‐pressure medium, which permit a further actuation of said blade‐adjusting means for the purpose of moving the blades beyond that predetermined pitch range only after increased hydraulic adjusting pressure has been able to open said auxiliary valve means, and means connecting said governing member and said change‐over member in such a way that they can be adjusted by a deliberate manual operation for the purpose of connecting said additional source of hydraulic pressure to said other source of hy‐draulic pressure, said member determining the magnitude of the hydraulic pressure acting on the blade‐adjusting means being thereby acted upon in such a way as to increase the hydraulic pressure, so that a greater quantity of pressure medium and an increased hydraulic pressure are available for adjusting the blades beyond the said normal pre‐determined pitch range.

Details

Aircraft Engineering and Aerospace Technology, vol. 16 no. 10
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 May 1939

H. Castaing

IN the construction of their airscrews the Hispano Suiza Company use principally aluminium alloys—duralumin, alfcrium, avional—with a mean density of 2·8, and with…

Abstract

IN the construction of their airscrews the Hispano Suiza Company use principally aluminium alloys—duralumin, alfcrium, avional—with a mean density of 2·8, and with mechanical properties equal to those of a half‐hard steel. They have been considering for some time the manufacture of blades of magnesium alloy, the mean density of which is 1·8, thereby offering considerable advantage over the aluminium alloys as regards weight, but, in this article, only aluminium alloy blades are dealt with.

Details

Aircraft Engineering and Aerospace Technology, vol. 11 no. 5
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 5 October 2021

Adel Ghenaiet

This study aims to investigate the trajectories of sand particles and erosion wear in a hydraulic turbine model.

Abstract

Purpose

This study aims to investigate the trajectories of sand particles and erosion wear in a hydraulic turbine model.

Design/methodology/approach

The Lagrangian-based approach is used to track large numbers of sand particles and determine their impact through the hydro turbine components. The tracking procedure includes the stochastic eddy interaction model and the squeeze film effect. The number of particles, sizes and release positions are conformed to the particle concentration and size distribution. The impact locations, frequency and conditions of impacts are used to estimate the erosion rates and thereby the eroded mass from the distributor vane and the rotor blade and their deteriorated geometry.

Findings

The patterns of erosion in the stationary and rotating parts differ significantly and the effect of the initial position of the runner blade is elucidated. The distributor vane is characterized by a widespread of erosion over the pressure side. Typically, the surface beyond the throat and the root and tip junctions are the regions prone to erosion wear. The entry region of the runner blade is subject to a high number of impacts resulting in high erosion rates visible from the forepart of the blade pressure side.

Practical implications

The erosion patterns and geometry deterioration may serve to evaluate the drop in the hydraulic performance and to select the appropriate surface coating to extend the lifetime of the turbomachinery parts and reduce the maintenance cost.

Originality/value

Erosion developments reveal a strong dependence on the blade position against the distributor vane and the particle size and concentration level.

Details

Engineering Computations, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0264-4401

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