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Volume 34, Issue 6
Displaying 1-7 of 7 articles from this issue
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Technical Papers
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Jun AOYAMA, Kunio OKUDE, Eiji NAKAYAMA, Isamu IIDA2006 Volume 34 Issue 6 Pages 321-326
Published: 2006
Released on J-STAGE: August 23, 2007
JOURNAL FREE ACCESSMain parts of hydro-turbine of the hydroelectric power plants facility are operated during a long period of time, and the equipments had been renewed based on the data of preventive maintenance. In these latter days, as the deregulation of the electric power industry is moving forward, it is required an elongation of the period to renew equipments. This paper describes a newly developed method to estimate accurately the remaining life of long-operated equipments, like hydro-turbine casing and stay vane. Life estimation of these equipments becomes important because their replacement requires large-scale works. Life estimation is accomplished by grasping properly the propagation mechanism of deterioration.View full abstractDownload PDF (1449K) -
Akihiko MINATO, Kenichi KATOUNO, Takahide NAGAHARA, Kougi KARIYA, Nobu ...2006 Volume 34 Issue 6 Pages 327-335
Published: 2006
Released on J-STAGE: August 23, 2007
JOURNAL FREE ACCESSThe purpose of the present study is to develop a numerical tool for free surface flow and multi-phase flow problems in pumping stations. The benchmark experiments of sedimentation and bubble entrainment in a suction channel of a pump station were carried out. Predicted velocity profiles under free surface using SP-VOF (Simplified Piecewise Linear Interface Calculation and Volume of Fluid) method were in good agreement with experiments. Predictions of sedimentation area agreed well with experimental data taking particle size distribution, drag force and buoyancy into consideration. Bubble entrainment occurs at a junction of open and closed channel sections. Small scale tests of air entrainment were calculated and the critical velocity of incipient air entrainment was well calculated. The present numerical tool was able to treat key free surface and multi-phase flow phenomena in pumping stations.View full abstractDownload PDF (2286K) -
Hitoshi SOYAMA, Masatoshi FUTAKAWA, Takashi NAOE2006 Volume 34 Issue 6 Pages 336-342
Published: 2006
Released on J-STAGE: August 23, 2007
JOURNAL FREE ACCESSJapan Atomic Energy Agency and High Energy Accelerator Research Organization are constructing a MW-scale neutron source system, which will use liquid-mercury as a target material for spallation and to cool the target vessel in Japan Proton Accelerator Research Complex (J-PARC). The severe cavitation erosion may occur in the vessel of the target and it is necessarily to predict the life time of the target vessel, which is exposed to cavitation impact. As the target vessel is very thin and experimental erosion data induced by proton beam is very few, it is required to estimate the incubation period by a few points. The prediction method of incubation period has been proposed. In order to estimate cavitation erosion intensity on the target, an off-line test, which is modified on-beam test, was carried out. Measuring the cavitation intensity of the off-line test using a laser Doppler vibrometer, the relation between the cavitation intensity and developing time of cavitation bubble was found. The relation revealed a similarity law on scaling effect of cavitation erosion, which can be applied to cavitation erosion of pumps and turbines.View full abstractDownload PDF (1809K) -
Toshiaki SUZUKI, Sadao KUROSAWA, Yuetsu UTOH2006 Volume 34 Issue 6 Pages 343-348
Published: 2006
Released on J-STAGE: August 23, 2007
JOURNAL FREE ACCESSIn recent years, the needs of replacement of existing hydraulic power stations with power-up has been increasing. With this attempt, the value-added of power station can be improved without changing natural environment, and the effective use of clean energy can be also realized. In this paper, it is aimed to reduce the noise with low frequency, which occurs at penstock by the pressure interference of guide vanes and runner in an existing hydraulic turbine. At this time, there was a designing restriction where only runner replacement was allowed, however, the new power-upped runner which has low pressure interference and good performance has been developed, and its effect was confirmed by the three-dimensional unsteady flow analysis.View full abstractDownload PDF (1686K) -
Kenichi SUGIYAMA, Keisuke NAKANO, Shuji HATTORI2006 Volume 34 Issue 6 Pages 349-356
Published: 2006
Released on J-STAGE: August 23, 2007
JOURNAL FREE ACCESSSlurry jet tests, with an impingement angle of slurry at 60degrees, were conducted on four types of materials : HP/HVOF-sprayed 73WC-20Cr-7Ni layers, arc-sprayed 56W2C-NiCr layers, flame-sprayed and fused 41WC-NiCrCo layers, and base metal SCS6. We examined effect of slurry wear properties on cermet layers and base metal, in regards to flow velocity, sand concentration and mean diameter of sand. It was found that volume loss rates of the cermet layers were proportional to the 2.6th to 3.6th power of the flow velocity, and the exponent was slightly lower than that of metals. The volume loss rates increased approximately proportionally to the first power of sand concentration and the mean diameter of sand. The slurry wear resistance increased approximately proportionally to the third power of Vickers hardness, which corresponded to results obtained on conventional cermet layers. Therefore, volume loss rates of materials can be estimated by specifying parameters, Vickers hardness, flow velocity, sand concentration and mean diameter of sand, from the results of multiple linear regression analysis.View full abstractDownload PDF (1850K) -
Kazuyuki SUGIMURA2006 Volume 34 Issue 6 Pages 357-365
Published: 2006
Released on J-STAGE: August 23, 2007
JOURNAL FREE ACCESSAn aerodynamic optimization system for centrifugal fans consisting of an impeller and a diffuser has been developed. A fan's three-dimensional shape is represented by a non-uniform rational B-spline curve, which enhances the freedom of the blades' leading and trailing edge profiles. The fan's aerodynamic performance is predicted using commercial software, "STAR-CD." The optimization system uses a new algorithm that is a hybrid of a simulated annealing algorithm and a neural network. The hybrid algorithm not only can learn the design-space to predict better solutions, but also can analyze the space's statistical characteristics, such as its sensitivity and non-linearity. Applying this system to centrifugal fan design problems, we obtained novel fan shapes in which the leading edge of the impellers and the trailing edge of the diffusers were bent unconventionally. Important design parameters were simultaneously revealed using design-space analysis.View full abstractDownload PDF (2341K) -
Masami SUZUKI2006 Volume 34 Issue 6 Pages 366-373
Published: 2006
Released on J-STAGE: August 23, 2007
JOURNAL FREE ACCESSEvaluation of calculation accuracy is always needed when performing numerical computation. For this reason, the accuracy will be estimated by comparison with an analytical solution or experimental results. In CFD, the Navier-Stokes equation can be solved by the finite difference methods. However, it is difficult to investigate the reliability and accuracy of the calculation results, since general flows do not have an analytical solution. Moreover many guidelines exist from experience simulation about the computational domain size and other parameters. This research provides guidelines that can be used as these standards for the flow around an airfoil. First, a result calculated by a singularity method of distributing vortex sheet on an airfoil surface and a finite difference method are compared with an exact solution solved by the conformal mapping method about a potential flow, and the accuracies are checked. Finally, dealing with an actual problem of the viscous flow, the limit of the accuracy is grasped by computing the Navier-Stokes equation.View full abstractDownload PDF (2036K)
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