Offshore wind has potential to generate electric power at lower prices than other renewable energy. However it is said offshore wind generation is more costly than onshore. Therefore we verified power curves for time varying wind velocities offshore and on land, taking into consideration the difference of mean wind speed ratio, vertical distributions of wind velocity, and wind spectra of the offshore and land respectively. As a result we found that while the power curve for the land is worse than that for the offshore, they are inferior to the theoretical power curve as a steady velocity. Then we estimated power generation yields and costs for land and offshore wind farms by using the actual data i.e. the annual occurrence of mean wind velocities measured at the Port of Akita and Akita Regional Meteorological Observatory. Thus the annual energy yields depends on the ratio of mean velocity offshore to on land and the offshore is more competitive from 1.1 to 1.9 than the land. Furthermore, condition of being feasible is that the mean velocity offshore is twenty percent larger than on land. The paper also describes dynamic structural analytical results against wind and wave loadings as vibration characteristics of wind turbine system consists of blade; turbine, tower and sub sea base structure which become important to design the offshore wind farm.
A 73-year-old man visited our hospital complaining of a headache, mild visual disturbance in the left eye, left oculomotor palsy and abducens palsy. X-ray, CT and MRI examinations suggested posterior paranasal sinusitis or a tumor, probably in the sphenoid sinusitis. Either a cystic change or bone defect was detected. We opened the left sphenoid sinus through the maxillary and ethmoid sinuses. No tumor was found. In the sphenoid sinus, there was mucosal thickening with pus. All ocular complications except for abducens palsy disappeared within a few day after the operation. It was concluded that sphenoid sinusitis without mucocele caused the ophthalmological complications.
In order to clarify the effects of vortex core radius on the vortex bursting phenomenon, the premixed flame propagation in swirling flow has been examined by the numerical calculation for various vortex core radii. In this calculation, the flame is fixed in the computational domain by adding an axial flow to the unburnt premixed gas so as to obtain the steady state propagation characteristics. The obtained results are as follows : The obtained relationships between the maximum circumferential velocity and the flame propagation speed or the flame region radius agree with the previous studies. Moreover, the effect of vortex core radius on the flame propagation speed and flame shape are clarified. When the vortex core radius is less than 7 mm, the flame propagation speed is dependent on both the angular speed and the vortex core radius. On the other hand, when the vortex core radius is more than 7 mm, the flame propagation speed is directly proportionate to the angular speed not but the maximum circumferential speed, and it is not dependent on the vortex core radius.
To investigate effects of ambient atmosphere on flame spread, an experimental study has been conducted. The downward flame spread over solid fuel has been examined in a combustion chamber with a vertical duct to obtain uniform ambient atmosphere. The flame spread rate is measured with constant inflow velocity. Two kinds of paper sheet are used as samples. Ambient temperature is increased up to 150°C, and oxygen concentration is reduced to examine the diluent effect, adding carbon dioxide and nitrogen to the ambient air. The gas temperature is measured by thermocouples. Results show that, the flame spread rate is decreased with a smaller oxygen concentration, resulting in smaller heat flow into the preheat region, Q. Diluent effect of carbon dioxide is larger than that of nitrogen to reduce flame spread rate, with larger limiting oxygen concentration. In the gas temperature distribution, the maximum temperature is located around the flame zone, which is defined as the flame temperature. As oxygen concentration is decreased, the flame temperature is reduced. Hence, as the flame temperature is decreased, the heat flow into the preheat region is resultantly smaller. The temperature where the flame can not propagate is almost constant for all cases. Therefore, at extinction limit, the flame temperature is low so that the flame spread can not be supported due to smaller Q.
Numerical analysis of ultra-micro combustor was carried out by comparing with experimental results. First of all, we aimed at agreement of temperature distribution in the combustion chamber to the experimental result, which was basic data provided from a combustion phenomenon. We succeeded in simulating influence of porous material as inflow entrance and were able to confirm reliability of the present analytical model. Furthermore, we examined flame stability limits and influences of mixture preheating and wall surface temperature by using detailed chemical kinetics. The obtained results are as follows: Main combustion reaction occurs intensely near the outward wall of a combustion chamber. An increase of wall surface temperature brings high-intensity combustion of the whole combustion chamber.
Techniques updating bottom topographical data are described.Positional data from a RTK-GPS are transformed to rectangular coordinates by the Gauss-Krüger Projection, and synchronized with depth data from an echo-sounder to generate three dimensional topographical data.A bottom topography over a triangular mesh is updated by two methods.Errors due to the movement of a boat are corrected by outcomes from a clinometers and a compass.
For a power-to-gas (PtG) system, methanation has attracted attention to synthesize methane from carbon dioxide and hydrogen. There is a problem that heat generated by the reaction causes thermal degradation of the catalyst. Then, we have proposed a methanation reactor with circulation (MeRCi), where the temperature of the catalyst bed is controlled by recycling a part of the product gas. In this study, a one-dimensional model of the MeRCi was developed, and the methanation process was numerically simulated for assessment of reaction characteristics. The catalyst amount, the recycle ratio, and the catalyst bed length were changed. For comparison, the simulation of a straight-tube fixed-bed reactor was also simulated. Based on the gas temperature distribution of the straight-tube reactor, the simulation results show a good agreement with the experimental data, and the validity of our numerical model was confirmed. Even for the higher recycle ratio, the methane conversion rate at the reactor outlet does not change much, showing the high conversion rate within the simulation conditions. The increase of the catalyst packing density as well as the catalyst bed length enlarges the methane conversion rate. By considering the fact that the methane conversion rate is sufficiently high when the catalyst packing density is over 500 kg/m3, the reaction rate must be kept at certain level to keep the high methane conversion rate. As for the catalyst bed length, there is a minimum value at which the methane conversion rate unexpectedly dropped where unreacted hydrogen and carbon dioxide are retained in the products.
