Hidechito Hayashi

Power generation with salinity gradient by pressure retarded osmosis using concentrated brine from SWRO system and treated sewage as pure water

Abstract Salinity power generation using hollow fiber modules was examined using the pressure-retarded osmosis (PRO) system between pure water and concentrated brine. Pure water and concentrated brine were supplied from a regional sewage treatment facility and sea water desalination (sea water reverse osmosis [SWRO]) plant. To minimize the effect of the concentration polarization near the membrane surface on the pure water side, the number of open ports in the module was increased from 3 to 4 and that modification was found to be effective because non-permeating pure water, which left the module through fourth port, flushed leaked salt from the brine side through the membrane. Our prototype PRO plant got the maximum output power density, 7.7 W/m2 at a 2.5 MPa hydraulic pressure difference and a 38% permeation of pure water into the brine. To remove the organic foulant in the pure water, a low pressure Reverse Osmosis (RO) membrane and coagulation–sedimentation method with ozonation showed good results. Ho...

Flow Characteristics in Scroll Casing of Sirocco Fan

The sirocco fan is advanced in compact with high pressure and large flow rate. But the efficiency of it is relatively low. One of the reasons is the complex and large flow in the scroll casing. Then it is expected to clear the influence of the geometry of the casing to the fan performance and to make compact the fan without reduce the performance. This paper presents the flow characteristics in the scroll casing for four types geometries. The flow characteristics are examined in experiments and numerical simulations. The net flow out of the impeller is biased to the hub side and the circulating flow is generated near the shroud in the scroll casing. The pressure is large in the hub side and gradually decreased toward to the shroud. The pressure distributions are different for each scroll casing until the end of the scroll, and then it is emerged the pressure drop near the end of scroll casing. After it, there are a rapid pressure raise in all types. The pressure out of the fan becomes almost the same in a...

Prediction of Specific Noise Based on Internal Flow of Forward Curved Fan

In this study, a prediction theory for specific noise that is the overall characteristic of the fan has been proposed. This theory is based on total pressure prediction and broadband noise prediction. The specific noises of two forward curved fans with different number of blades were predicted. The flow around the impeller having 120 blades (MF120) was more biased at a certain positions than the impeller with 40 blades (MF40). An effective domain of the energy conversion of MF40 has extended overall than MF120. The total pressure was affected by the slip factor and pressure loss caused by the vortex flow. The suppression of a major pressure drop by the vortex flow and expansion of the effective domain for energy conversion contributed to an increase in the total pressure of MF40 at the design point. The position of maximum relative velocity was different for each fan. The relative velocity of MF120 was less than that of MF40 due to the deviation angle. The specific noise of MF120 was 2.7 dB less than that of MF40 due to the difference in internal flow. It has been quantitatively estimated that the deceleration in the relative velocity contributed to the improvement in the overall performance.

Effect of spindle speed control of air turbine spindle on milling for difficult-to-cut materials

In precision machining, machining efficiency is improved by high-feed, high-rotation milling using small-diameter ball end milling. Additionally, static air bearings having excellent properties including low friction, low vibration, high accuracy, and rapid response have been used widely to maintain cutting speed. However, insufficient investigations have been conducted of the stabilization of rotational speed during processing with an air turbine spindle used to drive the main shaft. We have been unable to conduct a systematic evaluation of the effects of changes of the rotational speed during processing on a machined surface with periodic cutting force. Therefore, this study controlled the rotational speed of the air turbine spindle using a high-precision, quick-response (HPQR) pneumatic pressure regulator to examine its effects on the material surface roughness. 1) Rotation-controlled milling was conducted with aluminum alloy and steel alloy, which has good machinability. Then its surface roughness was investigated. Aggravation of the surface roughness was prevented by maintaining the rotation speed: the cutting speed. 2) Rough milling for difficult-to-cut materials by the air turbine spindle without control was impossible. In the worst case, the rotation stopped because the spindle torque was insufficient. However, the rotation speed control of air turbine spindle resolved the torque shortage. An appropriate cutting speed was maintained throughout the milling process. These results demonstrated that the surface roughness was improved compared with non-controlled surface roughness.

The flow simulation in the membrane module of PRO using concentrated brine

The flow simulation of the membrane module of PRO, the following results obtained. 1. There is distorted flow in a module. 2. Amount of osmosis is different in a module. At the fresh water collects the amount of osmosis is rapidly decrease. 3. Amount of osmosis in hollow fiber area is about ten percent of the whole.

103 Relationship between Aeolian tone and Wake Vortex from Inclined Flat Blade : Characteristics of Vortex Shedding in Spanwise Direction

The three dimensional structure of the wake vortex was investigated in relating to the aeolian tone from the inclined blade. It was pointed out that the aeolian tone is largest not at zero, but at ten degree of the inclined angle. The correlation length of the wake vortex in span becomes large at small inclined angles. The large scale structures of the wake vortex are generated in zero and ten degree of inclined angle. The shape of the structure is influenced with the span-wise velocity in the dead air region. There are small scale spots of the pressure fluctuation at the trailing edge. The spots are interacted each other and make a large cluster of the pressure fluctuation. It is proposed that the scale of it is decided by the timing of the wake vortex formation. And the shape of the wake vortex structure is closely related with the scale of it. The correlation length of the wake vortex is calculated from the shape of the structure. The estimation of aeolian tone by using the length with Fukanos model is well coincided to experiments.

Improvement of Centrifugal Fan on Noise With Inducer

We improved the centrifugal fan for the noise and fluid performance. The fan has the inducer that is unified to the main blade. The geometry of the inducer was obtained with the tuft method and is unique. The fluid turns from axis- to radial-direction in the inducer. The inlet angle and the chord length of the inducer vary in span position. The aerodynamic and noise characteristics of the impeller with inducer have been compared to one without inducer. The total pressure and the efficiency of the impeller with inducer are increased about 20% and 5% in all flow rate. Because the pressure rise occurs in the inducer. And the pressure loss at the inlet of the blade becomes very small. The influence of the leakage flow between the shroud and the bellmouth is restricted near the front shroud, and then the separation of the boundary layer is controlled. The wake width of the main blade becomes fairly small. The specific noise level, which presents the noise performance of the fan, can be reduced about 2–4dB in wide flow rate.Copyright

Reduction of Turbulent Noise Generated from a Counter-Rotating Fan Using a Sound-Absorbing Duct

The purpose of this study is to investigate the effects of the length and the arrangement of a sound-absorbing duct on the aerodynamic characteristics and the turbulent noise of a counterrotating fan. Moreover, we performed a theoretical investigation of the turbulent noise reduction in relation to the thickness of sound-absorbing materials and the length of a sound-absorbing duct. The results are summarized as follows. The sound absorbing duct reduces a considerable amount of noise generated from the counter-rotating fan without degrading the aerodynamic characteristics. The sound-absorbing duct set upstream of the fan only reduces the noise radiated to the upstream and has no effect on that radiated to the downstream. The duct set downstream of the fan has an opposite effect. The agreement between predicted and measured values for the noise reduction is satisfactory.