Outlet Edge Research Articles

Distortion Behavior of a Heavy Hydro Turbine Blade Casting During Forced Air Cooling in Normalizing Treatment Process

Distortion behavior of blade castings in heat treatment process determines their geometrical accuracy, and improper control of it may result in additional repair, shape righting, or even rejection. This article presents a novel approach for discovering the distortion behavior of heavy blade castings during heat treatment process in production. Real-time measurements of distortion and temperature field of a heavy hydro turbine blade casting weighted 17 ton during forced air cooling in normalizing treatment process were carried out by using deformation measurement instruments and an infrared thermal imaging camera. The distortion processes of the typical locations of blade and the temperature field of the blade were obtained. One corner on the blade outlet edge side exhibits variation of distortion with two peaks and a valley. The range reaches 97 mm and the final distortion value is 76 mm. The maximum temperature difference on blade surface reaches 460 °C after 80 min of cooling. Influences of thermal stress and phase transformation stress on the distortion of the blade were elucidated and discussed. The results are of great significance for the understanding and control of the distortion behavior of hydro turbine blades in heat treatment.

Analysis of outlet edge cogging force at the Permanent Magnet Linear Synchronous Motor According to Difference of the Winding Method

PMLSM is structurally simple and it have a lot of merits such high speed, high thrust force etc., but cogging force by slot-teeth structure of armature and cogging force by outlet edge effect occurs. This is the cause of thrust force ripple and generate the noise and vibration. Therefore, in this paper we proposed installation of an auxiliary pole to mover of the PMLSM in order to decrease cogging force by the outlet edge which came necessarily into being discontinuous arrangement of the armature. Also, outlet edge cogging force designed a form of the auxiliary pole which the minimum became, and we compared a outlet edge cogging force characteristic along a winding method of an armature as we used 2-D of finite element analysis.

캐비테이션 감소를 위한 혼타의 형상 연구

This paper studies on the rudder shapes for the suppression of the cavitation around a horn-type rudder. To improve the problems due to cavitation, there have been several studies. However, these some studies are recognized as incomplete ways to suppress the rudder cavitation. In this study, the section shapes to suppress the cavitation phenomena are determined by moving the location of maximum thickness for reducing the curvature variation and changing the radius of leading edge. Also, in the pintle part, the curvature radius of the inlet outlet edge of rudder plate is changed. During the design of rudder shape, two-dimensional numerical simulations are firstly performed because those offer some advantages with that cavitation phenomena becomes predictable for a short time, and then the three-dimensional numerical simulations are performed to confirm the determination. The time mean distribution of the propeller slipstream is imposed on the inlet boundary condition. As some results, this paper shows the effects reducing the range of the occurrence of cavitation, and suggests the references on the design of a horn-type rudder for the suppression of cavitation phenomena.

Cogging Force Reduction of a Stationary Discontinuous Armature PM-LSM by Magnet Segmentation

Recently, permanent magnet type linear synchronous motors have been used as a driving source of transportation systems, to satisfy requirements such as speeding up of transportation systems and also to simplify maintenance. The authors' laboratory has proposed a stationary discontinuous armature PM-LSM in which the armature is engaged only when accelerated and decelerated operation is necessary, in order to resolve the problem of higher costs, when PM-LSM is used with long-distance transportation systems in factories. However, the stationary discontinuous armature PM-LSM contains the outlet edges which always exist as a result of the discontinuous arrangement of the armature. These edges become a problem, because the cogging force that they exert influences the controllability of the motor. This paper presents the results of an experimental examination and three-dimensional numerical analysis by the finite element method of the cogging force exerted by the outlet edge. Moreover, we modified the permanent magnet on the mover to decrease the cogging force at the outlet edge, and the results are examined using three-dimensional numerical analysis by the finite element method.

Numerical analysis of free surface instabilities in the IFMIF lithium target

The International Fusion Materials Irradiation Facility (IFMIF) uses a high speed (10–20 m/s) lithium (Li)-jet flow as a target for two 40 MeV/125 mA deuteron beams. The major function of the Li target is to provide a stable Li jet for the production of an intense neutron flux. Different hydrodynamic instability mechanisms are possible in the Li-jet flow. The main objective of this study is to provide a detailed numerical analysis of instabilities in the Li-jet flow caused by separation of the flow near the nozzle outlet. Experimental observations have shown that the change of the nozzle geometry at the outlet or nozzle edge defects causes the flow separation and occurrence of longitudinal periodic structures on the free surface. Target surface fluctuations of large magnitude can lead to the penetration of the deuteron beam in the target structure and cause the local overheating of the back plate. This work is focused on the validation the CFD code Star-CD and choice of the suitable simulation technique for further calculations of lithium target flow. Two simulation methods, Large Eddy Simulation (LES) and Reynolds Averaged Navier–Stokes method using the Shear Stress Transport (SST) turbulence model have been validated against the experimental data. Two experimental cases with two different kinds of instability sources were used to test the suitability of turbulence models to predict waves generated near the nozzle edge. While in the first case the instability source is a stationary located obstacle at the nozzle edge, in the second one the position of the instability sources is influenced from turbulent fluctuations in the boundary layer near the nozzle edge. LES has a reasonable agreement with experimental data. SST turbulence model is not able to predict the local flow separations at the nozzle edge caused by turbulence fluctuations and to reproduce instabilities of small magnitudes.

Effect of surface roughness on the squeeze film lubrication between curved annular plates

PurposeThis paper aims to study the effects of surface roughness on the characteristics of squeeze film lubrication between curved annular plates.Design/methodology/approachThe modified Reynolds type equation governing the fluid film pressure is derived. The stochastic method for rough surfaces developed by Christensen is to derive stochastic type equation and has been solved for two types of one‐dimensional roughness patterns. Closed form expressions of mean squeeze film pressure and mean load carrying capacity are obtained.FindingsThe bearing characteristics are computed for various values of roughness parameter. It is found that the effect of radial (circumferential) roughness pattern is to shift the point of maximum pressure towards the inlet (outlet) edge and also observe that the mean load‐carrying capacity increases (decreases) for the circumferential (radial) roughness pattern compared with the corresponding smooth case, for both concave and convex pad geometries.Research limitations/implicationsThe analysis is useful in obtaining suitable mathematical model of physical problems. The one which we have considered here is the idealized form of functioning of bearings in general. Analysis of finer models requires pure numerical schemes, for which the present model is a base.Practical applicationsFindings of the present paper have applications in machine elements like clutch plates and collar bearings.Originality/valueInclusions of surface roughness effect on the characteristics of bearings are original contributions in tribology.

Driving characteristics analysis of stationary discontinuous armature permanent magnet linear synchronous motor for factory automation systems

The stationary discontinuous armatures in permanent magnet linear synchronous motors (PM-LSMs), which consist of several stator sections that are distributed along the track and that the mover with PM is running without thrust force between these sections, have been proposed as a driving source for transportation systems. This design is very economical in long-distance transportation systems in factories, because the armature is engaged only when accelerated and decelerated operation is necessary. However, the stationary discontinuous armature PM-LSM contains the outlet edges which always exist as a result of the discontinuous arrangement of the armature. For this reason, the high alteration of the thrust force and the attractive force produced between the armature’s core and the mover’s permanent magnet when a mover goes through the between the armature’s installation part and non-installation part has been indicated as the problem of the stationary discontinuous armature PM-LSM. As a result, the stationary discontinuous armature design involves the velocity ripple of the mover with PM during acceleration when freewheeling changes over to re-acceleration. We have proposed and examined constant load angle control without position feedback in order to suppress the velocity ripple which occurs at the re-accelerator with the aim of achieving smooth drive of the stationary discontinuous armature PM-LSM. This paper describes the examination of constant load angle control without position feedback with the aim of suppressing the velocity ripple, which occurs in the re-acceleration portion. Also, we have examined the analysis of the effect of the outlet edge on the mover’s drive which exists as a result of the discontinuous arrangement of the armature side based on the re-acceleration characteristics obtained using constant load angle control without position feedback.

Cogging Force Verification by Deforming the Shape of the Outlet Edge at the Armature of a Stationary Discontinuous Armature PM-LSM

Stationary discontinuous armatures that are used in permanent magnet linear synchronous motors (PM-LSM) have been proposed as a driving source of transportation systems. However, the stationary discontinuous armature PM-LSM contains the outlet edges which always exist as a result of the discontinuous arrangement of the armature. These edges become a problem because the cogging force that they exert influences the controllability of the motor. This paper presents the results of three-dimensional numerical analysis by the finite-element method of the cogging force exerted by the outlet edge

Effect of the Outlet Edge at the Stationary Discontinuous Armature Permanent Magnet Linear Synchronous Motor

Effect of the Outlet Edge at the Stationary Discontinuous Armature Permanent Magnet Linear Synchronous Motor

Cogging Force Verification at the Outlet Edge of the Armature of a Stationary Discontinuous Armature Permanent Magnet Linear Synchronous Motor

Cogging Force Verification at the Outlet Edge of the Armature of a Stationary Discontinuous Armature Permanent Magnet Linear Synchronous Motor

Reduction of the Cogging Force at the Outlet Edge of a Stationary Discontinuous Primary Linear Synchronous Motor

Recently, permanent-magnet-type linear synchronous motors (PM-LSMs) have been used as a driving source of transportation systems, to satisfy requirements such as speeding up of transportation systems and also to simplify maintenance. The authors' laboratory has proposed a stationary discontinuous primary PM-LSM in which the primary is engaged only when accelerated and decelerated operation is necessary, in order to resolve the problem of higher costs, when PM-LSM is used with long-distance transportation systems in factories. However, the stationary discontinuous primary PM-LSM contains the outlet edges which always exist as a result of the discontinuous arrangement of the primary. These edges become a problem, because the cogging force that they exert influences the controllability of the motor. This paper presents the results of an experimental examination and three-dimensional (3-D) numerical analysis by the finite-element method (FEM) of the cogging force exerted by the outlet edge. Moreover, we deformed the shape of the primary to decrease the cogging force at the outlet edge, and the results are examined using 3-D numerical analysis by the FEM

一次側間欠配置リニア同期モータの端部コギング力の低減

Recently, linear motors capable of transmitting motive power without the use of mechanical converters have been attracting attention as drive sources for transportation systems, and there have been practical implementations of linear induction motors and linear synchronous motors. The authors have been engaged in developing transportation applications of permanent magnet linear synchronous motors using high-energy magnetic materials. We have proposed a discontinuous armature LSM in witch the armature side is engaged only when accelerated/decelerated operation is necessary, instead of one in which thrust is constantly applied. However, an outlet edge certainly exists, because the armature uses a discontinuous arrangement method. This edge becomes a problem, because the cogging force that it exerts influences the controllability of the motor. This paper presents the results of an experimental examination and three-dimensional analysis of the cogging force exerted by the outlet edge. We deformed the shape of the armature to decrease the cogging force at the outlet edge, and the results are examined by using three-dimensional analysis.

Influence of blades’ stress state on Francis turbine runner’s invalidation

Numerical simulation on Francis turbine runner's welding temperature field and welding tress field is carried out on the base of solving the problem of welding heat source's movement along any spatial routes and the problem of heat elimination between the complicated blade and air. The evolvement law of welding stress and the distribution of the stress field after welding are obtained. The results indicate that the peak value of the welding residual stress appears on the outlet edge of blade near the contact area between blade and band or blade and crown. Associated with the distribution of the runner's working stress, the invalidation reason of the Francis turbine runner is explained.

Pressure Fluctuation in a Vaned Diffuser Downstream from a Centrifugal Pump Impeller

Periodic flows downstream from a centrifugal pump impeller in vaneless and vaned diffusers were measured by using a single hole yawmeter and a phase‐locked sampling method. The flows were also calculated by an inviscid flow analysis using the blade‐surface singularity method. The periodic variations in calculated static pressure with the impeller rotating quantitatively agree well with the measured ones. The flow behaviors in the vaned diffuser are discussed, citing measured and calculated results. The potential interaction between the impeller and the diffuser blades appears more strongly than the impeller‐wake interaction. The appearance of static pressure fluctuations due to the impeller′s rotating in the fully vaned zone is different from that in the semivaned zone of the diffuser. The existence of the peripheral blade surface of the impeller outlet with an outlet edge of the pressure surface causes violent pressure fluctuations in the vaned diffuser.

Residual moisture reduction in coarse coal centrifuges using air purging. Part 3. Commercial scale trials

CSIRO/Novatech Consulting have been developing air purging as a new way of reducing the moisture content of coarse coal products from vibrating basket centrifuges. The process involves injecting a turbulent stream of high velocity air, via an air knife manifold, through the coal bed as it traverses the centrifuge basket. This paper describes the results obtained when the process was trialled in a commercial scale centrifuge, following successful previous bench and pilot scale work reported previously. Five manifolds of different shapes and sizes were tested. The best results were achieved with units of square cross-section, located close to the outlet edge of the basket. Depending on air speed, product moisture was reduced by between 0.7 and 0.9 wt% at a confidence level exceeding 95%. The best results approached closely the 1.0 wt% moisture reduction target which had been adopted as the project objective. Air purging had no significant effect on the content or size distribution of the solids in the centrate. Increasing air speed led to larger moisture reductions. Higher air speeds were needed compared with previous pilot scale work probably due to the thicker beds encountered in the full scale centrifuge. Despite the higher air speed, the actual air usage (cfm/t of coal) was much more efficient at full scale, being less than half that at pilot scale.

Effect of Surface Roughness on Hydrodynamic Lubrication of Slider Bearings

The effect of surface roughness on the performance of hydrodynamic slider bearings is studied. A generalized form of surface roughness characterized by a stochastic random variable with non-zero mean, variance and skewness is assumed to define the bearing surface topography. Various film shapes such as: plane slider, exponential, secant and hyperbolic are considered. The results are obtained for the general lubricant film shape in integral form which are numerically computed for the shapes under consideration. The results are presented both graphically as well as in tabular form. The performance of a rough bearing can be considered in terms of an identical smooth bearing with an equivalent film thickness. It is observed, for the lubricant film shapes under consideration, that the increasing positive values of α, σ and ε decrease the load carrying capacity, frictional force and temperature rise while it increases the coefficient of friction. Increasing positive values of α and ε shift the center of pressure towards the outlet edge. For negative values of α, the increasing value reverses the trend of the effect on performance characteristics which is in conformity with the physical aspects of the problem. A similar trend is observed in case of the effect of negative values of ε. Thus, a negatively skewed surface roughness modifies the performance of the slider bearings whereas the performance of a bearing suffers on account of positively skewed surface roughness. Moreover, it is noticed that in the case of exponential and hyperbolic slider bearings the effect of increasing values of σ is more pronounced whereas in case of plane slider and secant shaped slider this effect is marginal.

Study of Periodic Flow in Diffuser Downstream of Centrifugal Pump Impeller.

Periodic flows downstream of centrifugal pump impeller in vaneless and vaned diffusers were measured by using a single hole yawmeter with a phase locked sampling method. The flows were also calculated by a inviscid flow analysis with the blade surface singularity method. The periodic variations in calculated static pressure with impeller rotating quantitatively agree well with measured ones. The flow behaviors in the vaned diffuser are discussed with measured and calculated results. The potential interaction between the impeller and diffuser blades appears more strongly than the impeller wake interaction. The appearance of static pressure fluctuations due to the impeller rotating in the fully vaned zone is different from that in the semi vaned zone of the diffuser. The existing of the peripheral surface of impeller outlet and the outlet edge of pressure surface of impeller blade causes the large pressure fluctuations in diffuser.

Capillary end effect in a water saturated porous layer

The uni-directional propagation of oil injected into water flowing through a water wetted porous slab of a finite length is investigated. The inlet and outlet edges of the slab are impermeable to the oil flux. Hence, the oil accumulates within the slab, thereby leading to a saturation build-up-capillary end effect. This phenomenon is studied analytically on the basis of a nonlinear equation describing oil-water transport in porous media. A dimensionless criterion is derived, which governs the appearance and relative strength of the capillary end effect. For weak oil-water interfacial tension (large capillary number) and long porous slabs the above effect is not observed and the temporal evolution of the oil saturation is described by the Buckley-Leverett solution. Short porous slabs are found to be almost entirely subjected to the capillary end effect. Intermediate situations are identified and quantitatively described, in which the downstream part of the slab may be divided into two zones: one-characterized by the capillary end effect, and the other being a Buckley-Leverett zone.

Studies on estimating the performances of impellers with cut down of the blade edge of centrifugal pumps by the surface singularity method.

Pump performance depends on the outlet flow of the impeller. A method of surface singularities for core flow in the centrifugal impeller, combined with an integral method for a boundary layer, would explain the mechanism of the performance change with cutting the outlet edge of the impeller blades down. This method is applied to flows in the impellers with various cut downs of the blade edge, and then the calculated results are compared with the experimental ones. Both results are shown to be in quantitatively good agreement. On the influence of cutting the blade edge on the outlet flow, it is indicated that the cut of the pressure surface results in the decrease of relative flow angles with the decrease of radial velocity in the core flow, while that of the suction surface results in only decrease of the radial velocity. The change of the flow separation region due to the cut on the suction surface, however, combines to cause the pump performance to deteriorate.

Flow analysis in two-dimensional impeller of centrifugal pump by the surface singularity method combined with a flow-model of three-dimensional boundary layer.

An iterative solution method has been developed for calculating flows in two-dimensional centrifugal pump impellers. The method was formed by combining an integral calculation method for a three-dimensional boundary layer on the whole channel wall with a surface singularity method for a two-dimensional inviscid core-flow. In the inviscid analysis, the blade shape and the area of flow passage were modified by calculated displacement thickness of boundary layer, and then a finite number of vortices were distributed on the modified blade surfaces with the Kutta condition at the outlet edge on the suction surface. This method was applied to flows in two impellers with different blade thicknesses. Comparing the results of calculated and measured flows, both were qualitatively in good agreement, including an effect of the outlet blade surface with constant radius, which showed that relative velocity near the pressure surface was faster than one near the suction surface.