Araki S.,Kagawa University |
Yoshida H.,Kagawa University |
Nakagawa H.,DShikoku Research Institute Incorporated |
Naga K.,Shikoku Electrical Power Company
Theoretical and Applied Mechanics Japan | Year: 2013
It is required to maintain the durability of concrete structures from the viewpoint of the proper control of maintenance. Thus, it is necessary to evaluate the soundness of the structures. The ultrasonic method which is one of nondestructive tests is tried to use as an evaluation method. In the case of the object of which density is high and its distribution is homogeneous, the ultrasonic can detect defects correctly. However, a concrete is inhomogeneous, and the wave spreads intricately if it comes to a crack or a discontinuous portion. Therefore, the limit and usefulness of applicability of the ultrasonic method are indefinite. In order to apply the ultrasonic method to concrete structures, it is necessary to grasp the influence of the properties of the concrete on the propagation of the wave. In this study, numerical analyses are conducted with considering the inhomogeneous of the concrete to check the applicability of the ultrasonic to the concrete. © 2013 by National Committee for IUTAM.
Mitsubishi Group, Hokkaido Electric Power Co., Tohoku Electric Power Co., Tokyo Electric Power Company, Chubu Electric Power Co., Hokuriku Electrical Power Company, Kansai Electric Power Co., Chugoku Electric Power Co., Shikoku Electrical Power Co., Kyushu Electric Power, Electric Power Development Co., Japan Central Research Institute of Electric Power Industry and Clean Coal Power R&D Co. | Date: 2011-10-05
Provided is a ground flare in which a low-frequency vibration generated from a ground flare tower, such as a chimney, is properly adjusted to suppress it below a fixture-vibration generation limit, thereby preventing surrounding objects from resonating and vibrating. In a ground flare (10) that burns a flammable exhaust gas with a burner (11) at the lower end of a chimney, in which the lower end of the chimney (20) and the periphery of the burner (11) are surrounded by a windbreak (40), the low-frequency-noise sound pressure level of a ground flare tower composed of the chimney (20) and the windbreak (40) is reduced by selecting at least one of changing a natural frequency generated from the ground flare tower, using multiple ground flare towers, and installing a low-frequency-vibration absorber in the ground flare tower.
Mitsubishi Group, Clean Coal Power R&D Co., Hokkaido Electric Power Co., Tohoku Electric Power Co., Tokyo Electric Power Company, Chubu Electric Power Co., Hokuriku Electrical Power Company, Kansai Electric Power Co., Chugoku Electric Power Co., Shikoku Electrical Power Co., Kyushu Electric Power, Electric Power Development Co. and Japan Central Research Institute of Electric Power Industry | Date: 2011-06-15
It is possible to prevent a phenomenon by which the wall temperature of an outer cylinder rises abruptly as a layer of steam covers the inner circumferential surface of the outer cylinder and therefore decreases the heat transfer coefficient thereof, thus preventing a heat damage to the outer cylinder. Also prevented is burnout of the burner resulting from insufficient cooling due to variations in cooling efficiency at a leading end of the burner. A leading end located in a two-stage entrained-flow bed coal gasifier has a double-walled structure including an outer cylinder and an inner cylinder, and cooling water for cooling the leading end is supplied through an interior of the inner cylinder to cool the leading end and is then returned to a base end through a space formed between the outer cylinder and the inner cylinder. The space formed between the outer cylinder and the inner cylinder has a smaller channel area than the interior of the inner cylinder, and a swirling flow along a guide formed on an outer circumferential surface of the inner cylinder and a substantially linear flow in a longitudinal direction of the outer cylinder and the inner cylinder are applied to the cooling water returned to the base end through the space formed between the outer cylinder and the inner cylinder.
Mitsubishi Group, Hokkaido Electric Power Co., Tohoku Electric Power Co., Tokyo Electric Power Company, Chubu Electric Power Co., Hokuriku Electrical Power Company, Kansai Electric Power Co., Chugoku Electric Power Co., Shikoku Electrical Power Co., Kyushu Electric Power, Electric Power Development Co., Japan Central Research Institute of Electric Power Industry and Clean Coal Power R&D Co. | Date: 2012-07-25
A slag monitoring device 100 for a coal gasifier includes a slag hole camera 11 that observes a slag hole 3 from which molten slag flows out, a water surface camera 12 that observes a situation in which the slag flowing out from the slag hole 3 falls onto a water surface 5H of cooling water 5, a falling sound sensor 13 that observes a sound of the slag falling onto the water surface 5H, and a processing device 20 that determines a solidification and adhesion position of the slag based on an opening area of the slag hole 3 observed by the slag hole camera 11 and falling lines and falling positions of the slag observed by the water surface camera.
Tamura Y.,Mitsubishi Group |
Tani K.,Mitsubishi Group |
Okamoto N.,Shikoku Electrical Power Co.
IOP Conference Series: Earth and Environmental Science | Year: 2014
At both partial and full load of Francis turbines, the unsteady behavior of cavitating draft tube vortices occurs and leads to undesirable matters such as power house vibration, noise and power swing in some cases. This paper presents the investigation of the interaction between the flow pattern at runner outlet and the unsteady behavior of cavitating vortices in draft tube with experimental and numerical approaches. On the experimental research, the pressure pulsation in the draft tube is measured and the unsteady behavior of cavitating vortices is taken pictures with a high speed camera in the model test. On the numerical research, by Computational Fluid Dynamics (CFD) adopting a two-phase unsteady analysis, the analysis domain from the guide vane to the draft tube is carried out for investigating the interaction between the runner outlet flow and the vortex pattern. The pressure pulsation at the upper draft tube and the unsteady behavior of cavitating vortices obtained from CFD results are similar to those obtained in the model test. Detailed analysis of CFD results at overload indicates the repeat of expansion and contraction of cavitating vortices, which were shaped helical vortices with opposite direction of runner rotation, and the corresponding flow pattern in every time step of the pressure pulsations.
Shingai K.,Hitachi Ltd. |
Shingai K.,Mitsubishi Group |
Okamoto N.,Shikoku Electrical Power Co. |
Tamura Y.,Mitsubishi Group |
Tani K.,Mitsubishi Group
Journal of Fluids Engineering, Transactions of the ASME | Year: 2014
A series of numerical simulations for a Francis turbine were carried out to estimate the unsteady motion of the cavity in the draft tube of the turbine under a much larger flow rate condition than the swirl-free flow rate. The evaporation and condensation process was described by using a simplified Rayleigh-Plesset equation. A two-phase homogeneous model was adopted to calculate the mixture of gas and liquid phases. Instantaneous pressure monitored at a point on the draft tube formed long-period pulsations. Detailed analysis of the simulation results clarified the occurrence of a uniquely shaped cavity and the corresponding flow pattern in every period of the pressure pulsations. The existence of a uniquely shaped cavity was verified with an experimental approach. A simulation without rotor-stator interaction also obtained long-period pulsations after an extremely long computational time. This result shows that the rotor-stator interaction does not contribute to the excitation of long-period pulsations. Copyright © 2014 by ASME.
Ikeda M.,Shikoku Research Institute |
Kato S.,Shikoku Research Institute |
Nishizaka N.,Shikoku Electrical Power Company Inc. |
Ohno Y.,Shikoku Electrical Power Company Inc. |
And 2 more authors.
Tectonophysics | Year: 2013
We carried out a magnetotelluric (MT) survey along a profile crossing the Median Tectonic Line (MTL) in western Shikoku, Japan. The MTL is a terrane boundary that formed during the Cretaceous between the Sanbagawa belt, consisting of high pressure/temperature (P/T) metamorphic rocks, and the Ryoke belt of granites and low P/T metamorphic rocks. The MT image shows a zone of remarkably low resistivity, dipping northward at 40°, at the surface coincides with the surface trace of the MTL. The low-resistivity zone probably corresponds to a fluid-filled damaged zone of porous media composed of clay minerals and cracked rocks, formed by repeated faulting of the MTL since Late Cretaceous time. The calculated maximum porosity of the damaged zone is 7.1%, which is clearly higher than that of the non-damaged crystalline rocks. © 2013 Elsevier B.V.
Okumoto Y.,Chugoku Electric Power Co. |
Yorino N.,Hiroshima University |
Sasaki Y.,Hiroshima University |
Zoka Y.,Hiroshima University |
And 2 more authors.
IEEJ Transactions on Power and Energy | Year: 2012
Mega penetration of photovoltaic power generations (PV) will be introduced in future electric power systems, coping with environmental problems such as global warming and energy exhaustion. The authors have pointed out that difficulties will arise in performing the N-1 security standard if increase in uncertainties cannot be avoided caused by the PV penetration. Then, we have proposed a new concept of "robust power system security" together with the several conditions to be satisfied to guarantee the N-1 security standard under the uncertainties. In this paper, (1) a model of uncertainties by PV generation is proposed based on the robust power system security; a method for proper parameter selection is also provided. Then, (2) the influence on the stability by the PV and load disconnection from the power system is studied through simulation using the model system; (3) the effect of PV's fault ride through (FRT) on the stability is investigated as well as dynamic voltage support (DVS). Finally, it is shown that (4) complicated burden tasks will be considerably increased in power system operation planning and real time operation in the future circumstance by the mega penetration of PV. © 2012 The Institute of Electrical Engineers of Japan.
Minato S.,Kyoto University |
Tsuji T.,Kyoto University |
Matsuoka T.,Kyoto University |
Nishizaka N.,Shikoku Electrical Power Co. Inc. |
Ikeda M.,Shikoku Research Institute
Exploration Geophysics | Year: 2012
The common reflection surface (CRS) stack is an alternative method of producing a zero-offset stacked section with a higher signal-to-noise ratio (SNR) than the conventional normal moveout (NMO)/dip moveout (DMO) stack method. Since, however, it is difficult to determine global optimal parameters for the CRS stack method by the conventional three-step search method, especially for complex structures and low-fold data, we investigate the ability of simulated annealing (SA) to optimise our estimation of these parameters. We show a detailed but practical procedure for the application of SA to the CRS stack method. We applied the CRS stack method with SA to numerically modelled seismic reflection data, and to multichannel marine seismic data over complicated geological structures around the Median Tectonic Line (MTL) in Japan. We used the results of the conventional three-step search algorithm as the initial model for the SA search and showed that with this approach SA can estimate CRS parameters accurately within a reasonable number of calculations. The CRS stack method with this approach provided a clearer seismic profile with a higher SNR than either a conventional NMO stack method or a conventional CRS stack method. © 2012 ASEG.
Itoh J.-I.,Nagaoka University of Technology |
Hayashi F.,Shikoku Electrical Power Company
IEEE Transactions on Power Electronics | Year: 2010
A ripple current reduction method is proposed that does not require additional switching devices. A current ripple that has twice the frequency component of the power supply is generated in the dc part when a single-phase pulsewidth-modulated inverter is used for a grid connection. The current ripple causes shortening of the lifetime of electrolytic capacitors, batteries, and fuel cells. The proposed circuit realizes a dc active filter function without increasing the number of switching devices, because the energy buffer capacitor is connected to the center tap of the isolation transformer. In addition, the buffer capacitor voltage is controlled by the common-mode voltage of the inverter. The features of the proposed circuit, control strategy, and experimental results are described, including the result of ripple reduction, to approximately 20% that of the conventional circuit. © 2010 IEEE.