In this study, a renewal planning problem of energy supply system is formulated as a large scale mixed-integer linear programming problem, in which the objective function to the minimized is the average value of annual total cost during system's evaluation period. By adopting the programming language AMPL and CPLEX solver, a numerical study is carried out for a hospital, where electrical(e.g., heat pump) and gas(e.g., gas engine cogeneration) systems are compared together with arbitrary combination one, which is composed of electrical and gas driven pieces of equipment, by focusing particularly on the influence of initial system's difference. The main results obtained are as follows: (a) If the initial system is gas one, it is better to renew it to the electrical one as soon as possible due to relatively low energy efficiency of gas utilizing pieces of equipment, the high price of gas input energy and so on. (b) If the initial system is electrical one, the optimal renewal year becomes relatively later year, because it is economically better to use the initially installed high efficiency system as long as possible. (c) Theoretically, the arbitrary combination system is of course the best renewal one. However, there is no economic difference between the arbitrary combination system and the electrical one.
This paper describes a gas turbine inlet air cooling system using high pressure spray nozzle. Scale model inlet duct is manufactured within water spray of inlet fogging system, and many testing was conducted on the condition of same level of actual velocity with inlet duct at site. As testing results, droplet size finally reduce to SMD 80μm at 1st blade leading edge. Next, water spray adjusting actual attack to blade is provided to test piece of same material with actual compressor blade, and weigh is measured at every constant time period for getting averaged erosion depth. As a result, it is concluded that erosion at leading edge of 1st compressor blade is predicted to be approx 1.2mm at maximum per 10 years less than acceptable limit of depth, and it may have no need for maintenance of blade replacement and so on in 10 years.
私が大阪大学工学部機械工学科を卒業したのが 1963 年であった.当時,卒業研究は夏休み前から始められた. 配属先は小笠原光信先生ご担当の内燃機関研究室であった.黒板に書かれたいくつかのテーマから卒業論文とし て「噴霧燃焼の解析」を選んだ.これは,博士課程 2 年生であった水谷幸夫先生の博士論文の主題であり,すで に理論の構成,方程式等すべて水谷先生が考えておられた.私は,約半年間,朝から晩まで,手回し計算機で微 分方程式の数値計算をした.それが水平方向に伝播する噴霧燃焼速度の一部に使われた.それで,なんとか卒業さ せていただいた. 修士課程では石谷清幹先生ご担当の蒸気工学研究室に移った.これは,卒業研究とは異なる研究をしてみたかっ たからである.研究室を自主的に移ることは,私たちの学年では比較的多かった.配属後の 1 年間は先輩の「蒸 気・水二相流の圧力損失の測定」のお手伝いをしながら,研究室のボイラの熱出力を約 10 倍にあげる改造や熱交 換器を含む実験装置の計画等を行った.1 年を経て,今度は自分の番になった.先輩の後を継げば装置は揃って いるが,熱が直接関連するテーマにしようと思い,「局所加熱による蒸気・水二相流の水平流路内熱伝達」に関す る研究を立ち上げた.水平流路の上部と下部を別々に加熱した.興味深かったことは,水平流路を二相流が流れる ときは,特に流速の遅い時には相分離が生じ, 上部と下部で熱伝達の状況が著しく異なることであった.水平流路 を流れる二相流の流動状況はすでに理解されていたが,熱を加えた研究は当時無かった.しかし,ここで得られた 結果は,まだ初期段階であった.それで,系統的なデータを得るための実験と解析的な研究が必要であると考えた. それで,博士課程に行くことになった.テーマは「水平流路内沸騰における限界熱負荷に関する研究」であった. 実験は,蒸気・水二相流を高圧蒸気で加熱したり,電気を直接管に流して加熱したりして,水平流路の上部およ び下部における沸騰曲線や上部におけるドライアウト,高速流におけるバーンアウト等の結果を得た.解析では, 一部,電子計算機を使う必要があったが,当時のコンピュータはカード形式であり,カードを箱につめて計算セ ンターへ通った.JSME 1967 Semi-International Symposium が東京の経団連会館で開かれた.機械工学の全領域を 含む大きな Symposium であった.二相流の相分離による dryout に関する研究を,当時は模造紙にマジックインク を使った手書きの図を使って発表させていただいた.私にとって英語で発表するのが最初の経験であった.その 後,博士課程の 3 年間の成果を 4 編の論文として発表した. 博士課程を修了した頃,産業機械工学科が新設され,私は同学科に創られた小笠原光信先生ご担当の熱および 物質移動学研究室の助手,半年後に助教授にしていただいた. その研究室は新しく出発したもので,それまでの 高城 敏美
To increase load factor of nuclear power plants, it is necessary to decrease the number of days needed for periodic inspection and the number of days of unplanned outages. One of the countermeasures for these issues is to establish a prediction method for pipe wall thinning. There are two phenomena to be considered in pipe wall thinning. They are flow accelerated corrosion (FAC) and liquid droplet impingement erosion (LDI). In boiling water reactors (BWRs), LDI tends to influence pipe wall thinning more than FAC does. LDI is the wall thinning phenomena caused by droplet impingement. It is necessary to develop an appropriate method to predict the location of wall thinning. In this paper we compared measured data with computational analysis results for the location of wall thinning. By defining that the droplet frequency distribution had double peaks at the extrapolated location from the wall of an orifice toward downstream, we were able to predict the central location of the large reduction in thickness with a difference of less than about 0.2D[mm](D: pipe diameter) from the measured location in the flow direction at the elbow.
In the flow around a circular cylinder, a sudden decrease in the drag force occurs at a high Reynolds number, but the same phenomenon occurs at a lower Reynolds number in the case where there exist grooves or roughness on the circular cylinder surface. In previous study of authors, in order to investigate the effect of the depth and number of grooves on a circular cylinder for both arc and triangular grooves, the drag coefficient, pressure, turbulence intensity and velocity distribution were measured. Moreover, the flow around circular cylinders was analyzed by applying the RNG k-ε turbulent model. From these studies, it was found that in order to reduce a drag in a wide range of Reynolds number, the depth and number of grooves is increased and the circular cylinder surface is made to change to a turbulent boundary layer in a low Reynolds number. Furthermore, it was clarified that in order to prevent generating of a separating bubble, capacity of groove is made small and separation is retarded. In this paper, new shape of grooves was developed on the basis of the factor of above-mentioned drag reduction. As a result, the separation point of the circular cylinder with grooves of curved sectional shape shifts to the most downstream side and the drag coefficient becomes the smallest.
Homogeneous charge compression ignition(HCCI) combustion is promising a new combustion system reducing NOx and PM simultaneously without any penalty of fuel consumption. However, the operational range of the HCCI combustion system is limited because of some issues such as poor control of ignition timing and the excessive rate of pressure rise. In this study, a new combustion system based on an HCCI combustion process will be proposed. The combustion system has a pre-chamber in the cylinder head. On the combustion system, at first, ignition takes place in the pre-chamber, and then the burned gas ejected into the main chamber ignite the mixture in the main chamber. In the combustion system, the combustion process in the main chamber is aimed to go on same manner of the HCCI combustion process. This paper presents the concept of the combustion system and test results of some experiments.
Computational fluid dynamics (CFD) modeling and experiments have both advantages and disadvantages. Doing both can be complementary, and we can expect more effective understanding of the phenomenon. CFD is generally difficult to obtain reliable results over the wide range when compared with the experiment However, it is possible to obtain useful detailed results in any condition based on verification using the experimental results Moreover, experiments are not necessarily deliver correct results for any arbitrary condition due to limitations of the experimental equipments, the measurement errors and the problems with measurement systems. In this paper, the efficiency of a wind turbine is proposed, and the performance can be compared with the other turbomachineries, which is different from the traditional wind turbine factors, that is, the power coefficient, the torque coefficient, the thrust coefficient and so on. The characteristics of wind turbine are evaluated by combining simple approximate analysis based on wing section, CFD simulations and experimental results.
A drop actuation utilizing the wettability change by laser beam irradiation was studied by numerical simulations. The drop is actuated because surface tension force acts on the irradiated side more strongly in the wall parallel direction due to the smaller contact angle on that side. On the other hand, the temperature gradient due to laser irradiation causes surface tension gradient, then so-called Marangoni flow is caused. Each flow direction due to the wettability effect and the Marangoni effect is opposite. Those effects were evaluated by numerical simulations by a front-tracking method, which can properly evaluate the surface tension effect even on the solid surface and even with spatial gradient. As the results, we found that a simple model considering the macroscopic force balance could predict the moving condition due to wettability change fairly well although it could not predict the condition of movement caused by Marangoni effect. It is shown that the present numerical approach is very useful to predict such complex interfacial phenomena.
LDV (Laser Doppler Velocimetry) measurement has been made near a rough surface to clarify the effect of momentum transports to pressure distribution acting on a roughness element. The measurements were performed for an equilibrium boundary layer developing over the rough surface that the roughness height is proportional to a streamwise distance. The momentum thickness and roughness Reynolds numbers are 6000 and 150, respectively. The accuracy of the mean velocities and turbulence in LDV measurement was checked by a momentum balance method and the estimated value was compared with the local skin friction coefficient measured by a direct measurement. Near the rough surface except for a cavity region, it was confirmed analytically and experimentally that the averaged shear stress profile given as a sum of apparent shear stress due to waviness of mean streamlines, Reynolds shear stress and viscous stress per a roughness pitch length is approximately equal to the wall shear stress. In the cavity region, the averaged shear stress profile can be expressed as a function of an integral of the mean pressure difference on downstream and upstream sidewalls of the cavity, and takes positive value except for the bottom region. In the present rough surface, the gradient of spatially-averaged Reynolds shear stress with respect to height will mainly contribute to the mean pressure difference on sidewalls in the cavity.
The effects of the applied voltage and electrode dimensions on the backward jet induced by a dielectric barrier discharge plasma actuator (DBD-PA) are investigated experimentally. The applied voltage waveform used in this study is a pulse waveform with an amplitude V PP = 8 kV (-8 kV ≤ V ≤ 0 kV) and a frequency f = 5 kHz. With respect to duty ratio D of the applied voltage waveform, it is found that the backward jet induced by the DBD-PA is only generated for 93% ≤ D ≤ 93.5%. On the other hand, the forward jet is only generated for 10% ≤ D ≤ 92%, and the velocity and direction of the jet are significantly dependent on the duty ratio. These jets do not occur when D < 10% and D > 93.5%. With respect to the electrode width, the backward jet is generated for an upper electrode of sufficient width (10 mm in this study), even if the lower electrode width is short. In contrast, the forward jet is generated when the upper electrode width is short (5 mm or less), and the velocity of the jet increases as the upper electrode width decreases.
In the previous report, as a new application of Stirling cycle, it is proposed to apply the Stirling cycle to heat speaker which amplifies sound vibration by means of thermal energy. In present report, the characteristic of this speaker was discussed and applying this theory an experimental device of heat speaker was developed. Using this device, the frequency characteristic of heat speaker was investigated. As a result, the amplification factor by heating decreased with frequency, and at the level of above 85[Hz] the amplification factors were minus value. The result of decreasing amplification factor is likely caused by decreasing of the movement of displacer attached to the voice coil.
A reaction rate in a planar liquid jet with a second-order chemical reaction A+B→R is experimentally investigated. The jet flow contains the reactant A and the ambient flow contains the reactant B. The concentrations of reactive species are simultaneously measured by using the optical fiber probe based on the light absorption spectrometric method. The measurement result of mean reaction rate shows that the chemical reaction mainly occurs near the jet centerline in the upstream region, and the mean reaction rate is small in the downstream region. In the upstream region, lateral profiles of concentration correlation of reactants A and B have two local minimum values located away from the jet centerline, whereas the local minimum value of concentration correlation in the downstream region is located on the jet centerline. Comparison of concentration correlation of species A and B between the reactive and non-reactive cases shows that the chemical reaction makes the concentration correlation large near the edge of jet in the upstream region, whereas the opposite effect of chemical reaction on the concentration correlation can be seen in the other region. The concentration correlation of reactants A and B are estimated by using the Toor's hypothesis or the 3E model. The results show that the concentration correlation of reactants A and B estimated by using the Toor's hypothesis is smaller in magnitude than the experimental values, and the 3E model also fails to accurately estimate the concentration correlation.
The flow characteristics of a new hybrid vertical axis wind turbine which has advantages of the drag type and the lift type wind turbine have been investigated by the conditional sampling PIV. The experimental apparatus is constructed using the PIV measurement system with a conditional sampling device and a new hybrid vertical axis wind turbine model installed in a circulating water channel. The measured velocity vector fields have clarified that the low velocity regions are inside of rotating turbine and the downstream of it. The influences of the low velocity regions on the torque generated by the blades are investigated by the tangential forces calculated by the pressure distribution around the blades calculated from the velocity fields measured by PIV. And, it has been clarified that the tangential forces of the blades in the low velocity regions are small. Moreover, it has been clarified that the tangential forces generated by the rotating hybrid blades are sourced not only by the lift but also by the drag in the low tip speed ratio case. Therefore, the effectiveness of the hybrid blade for the new vertical axis wind turbine has been demonstrated.
Concentrated Solar Power, or CSP, is a system that concentrates and converts sunlight into thermal energy by tracking the sun. University of Miyazaki set up a beam-down solar concentrator, one of CSPs, on August 2012. Gardon gauge is a heat flux sensor which is generally used for measuring the heat flux on the light condensing part of CSP. Gardon gauge needs a water-cooling system, and it is impossible to measure heat flux on the sunlight condensing part where equipment is running. In this study, the thin-film heat flux sensor which can measure the heat flux by non-cooling during the equipment operation was developed. Furthermore the calibration system for the heat flux sensor was developed, and the advantages of the sensor were confirmed.
The gas turbine system known as AHAT (Advanced Humid Air Turbine) has been drawing attention. This system employs a humidification tower to increase the air mass flow at the compressor outlet. To estimate the humidifying transients, a dynamic model of the humidification tower was developed. This paper describes the humidification tower dynamics based on simultaneous differential equations considering heat and mass equilibrium of humid air, feed water, vessel materials, and packing materials. Values calculated using the model were compared to the experimental values obtained from laboratory-scale experiments. The calculation error margin was 3.8 degrees for air outlet temperature and 10.9% for air outlet absolute humidity. The developed model was then applied to a demonstration-scale conditions. The maximum change rate of absolute humidity at the humidification tower exit for startup and shutdown operations was 8.6%/s for 30 seconds. The maximum change rate of absolute humidity was influenced by the minimum area flow rate which corresponded to performance of packing materials.
In this study, we experimentally investigated the effects of additives such as rust inhibitors, propylene glycol, coconut fatty acid, and potassium hydroxide on the drag reduction of a surfactant solution, Ethoquad O/12. To study the drag reduction mechanism, we measured the particle size distribution in test solutions using a dynamic light scattering spectrophotometer. The results demonstrated that 1250 ppm Ethoquad O/12 aqueous solution showed drag reduction by about 60% at a Reynolds number of 8000. Further, addition of rust inhibitors such as benzotriazole, amine salts, and tolyltriazole appeared to have little effect on the drag reduction. However, addition of propylene glycol to Ethoquad O/12 aqueous solution reduced the rate of drag reduction to about 50%. In contrast, addition of coconut fatty acid and potassium hydroxide resulted in the drag reduction effect disappearing altogether. Peak diameters of the particle distribution of 180 nm and 50 nm were observed in Ethoquad O/12 aqueous solution, which indicated the drag reduction effect. The peak diameters in the solution with added propylene glycol changed to 230 nm and 75 nm. In contrast, the peak diameters in the solutions with added coconut fatty acid and potassium hydroxide, which were without the drag reduction effect, changed to 17 nm and 5 nm—obviously very small particle sizes. Therefore, we conclude from the results that the drag reduction effect is closely related to a change in the particle size of a surfactant solution.
Flow Accelerated Corrosion (FAC) is one of the issues to be noticed considerably in plant piping management. For the integrity and safety of the plant, the wall-thinning and thinning rate due to FAC should be predicted, and we hope to construct the model to predict the wall thinning rate. We have studied FAC from the view point of flow dynamics. The mass transfer coefficient and the velocity fluctuation are measured simultaneously behind the orifice in pipe. The former is obtained by the electrochemical method and the latter is PIV measurement. Space-time correlation and conditional sampling technique reveal that the large scale motions play an important role for the mass transfer rate at the wall and there is a time lag between mass transfer and velocity fluctuations. They may be useful for the model to evaluate the wall-thinning rate.
To investigate the front shape and fluctuation of cellular flames on a flat burner, we treated CH4/Air mixtures and two types of CH4/O2/CO2 mixtures. We obtained the front shape of cellular flames, i.e. the cell width and cell depth, by the planar laser-induced fluorescence of CH radicals (CH-PLIF) and measured the light emission to clarify the characteristics of fluctuation of premixed flames. As the flow rate of methane decreased, the cell width and cell depth became larger, and the size of attractors increased. Compared with CH4/Air mixtures, cellular fronts were observed at large flow rates of methane in CH4/O2/CO2 mixtures, and the trajectory of attractors was complicated. These were because of high intensity of diffusive-thermal instability resulting from the replacement of N2 with CO2.
Mainly steam is utilized as a means for thermal energy supply in industrial fields. It is important to be aware of the steam flow rate in the view point of energy management. However, steam becomes wet in many cases in the process to be sent through steam pipes to machinery using steam. It is well known that the wetness of steam sometimes causes measurement errors of the steam flow rate, and there has scarcely been the established method for estimating the error caused by the wetness of steam flow. Accordingly, we conducted the experiments of wet steam flow rate measurement to clarify the measurement error caused by the wetness of steam. This paper reports the measurement using a vortex flow meter, following our previous paper using an orifice flow meter(1). The experiments were conducted with the conditions in changing the flow rate, pressure and wetness. As a result, the correlation between the measurement error and the flow condition was clarified.
This paper presents a numerical solution to multi-objective shape optimization problems of steady heat-convection fields. In previous study, it has been dealt with a shape optimization problem for total dissipated energy minimization in the domain of a viscous flow field and a shape determination problem of temperature distribution prescribed problem in sub-domains of heat-convection fields. In this study, a multi-objective shape optimization problem using normalized objective functional is formulated for the total dissipated energy minimization problem and the temperature distribution prescribed problem in steady heat-convection fields. In addition, another multi-objective shape optimization problem is formulated for the temperature distribution prescribed problem, while the total dissipated energy is constrained to less than a desired value, in the steady forced heat-convection fields. Shape gradients of these multi-objective shape optimization problems are derived theoretically using the Lagrange multiplier method, adjoint variable method, and the formulae of the material derivative. Reshaping is carried out by the traction method proposed as an approach to solving shape optimization problems. The validity of proposed method is confirmed by results of 2D numerical analysis.
