Takeshi Nakazawa

Performance of Air-Water Separator by Coulomb Force

The air-water separators in this study are based on the principle of the electrostatic precipitator with the positive and negative poles, which has been widely utilized to collect the dust contained in flue gas exhausted from the industrial plants such as coal fired power station.This mechanism of separation is that the water droplets charged negative ions by corona discharge are collected on the positive pole by the Coulomb force operating between the both poles.Two kinds of experimental separators for vertical upward flow are used, one consists of a duct with a crosssection of 52×52mm and length of 700mm made of transparent acrylic plate with two sheets of zinc plate as positive pole and copper wires of φ 0.32mm as negative pole, and the other consists of a cylinder of φ 57.2mm and maximum length of 462mm made of stainless steel as positive pole and a stainless wire of φ 1.0mm as negative pole.The whole experimental duct is of the same material and the same sross-section as the former separator so that the atomizing condition of water from the nozzle and the behavior of water droplets can easily be observed.Experiments were conducted at 2.2 to 4.0m/s in mean air velocity and 0 to 17kV in DC high voltage, and the fractional separation efficiency and overall efficiency were obtained, and the performances of all separators were discussed.

Determination of Droplet Size Distributions using Image Processing System

This paper describes the image processing system that automatically analyzes the size distributions in droplet video images.This processing system, based on a conventional video camera, a digital image processor, a 32 bit personal computer and a monitor, is operated by a software written by the Basic of program language.Images are generated by taking the microphotographs of the water droplets captured on a plate of glass coated with a slightly deteriorated cylinder oil. After image acquisition, the recorded video frames are replayed and analyzed under computer control.The performance data are given from the experiment which is carried out to compare measurements of real spray distribution obtained by using the automatic system with those manually obtained from a microphotograph of water droplets.Consequently, the accuracy for the both measurements is 7.54 % in relative error for 290 water droplets used here being varied over the range of 3 to 136μm in diameter.Furthermore, it is found that by utilizing the image processing algorithm, the optimum threshold level is selected and this level is the value just before the black shadow begins to appear in the background of a monitor.

Calculation for Roughness Increase of Ship Equipped with CPP by Personal Computer

One of the author had published the paper of“On the Presumption of Bottoms Roughness with Making Use of Propeller Efficiency (Open) on CPP”. When calculating the increase of the bottoms roughness using the personal computer, it is important to give the good approximate performance curves between delivered horse power and ship speed.So, it was found that interpolation method with a cubic periodic spline gives good approximate values.If the spline function gained with the only four measured points can not give the good values, then, by adding two estimated points on the range of low and high ship speed, good performance curves could be gained effectively.Based on the accurate approximation of the performance curves, the increase of the bottoms roughness can easily obtained on the stand-by condition for short time by a personal computer.

Droplet Separation Performance of Corrugated Eliminator in Vertical Upward Air Flow

In this paper, the separation performance of corrugated eliminators is investigated experimentally, and the eliminators are all held perpendicular to the vertical upward flow of air laden with water droplets.The plates of eliminators used here are made of polyvinyl chloride, and are approximately represented by the sine-wave form. These eliminators have four different wavelengths of 130, 76, 63, 32 mm, wave amplitudes of 18, 9.0, 8.0, 4.5 mm and gaps between the plates of 30, 15, 15, 12 mm, respectively, and their bending numbers are six.Experiments have been made varing from 0.5 to 3.0 m/s in mean air velocity. In vertical upward air flow, the acceleration of gravity has slightly influence on the separation efficiency and the water-film on the eliminator plate surface has also slightly influence on the pressure loss coefficient, respectively.Obtained separation performances are compared with the results predicted by theoretical analysis which has been presented before.

Separation Performance of Wire-mesh Demister in Vertical Upward Air Flow

In this paper, effects of the number of the layers on the separation characteristics of the wire-mesh demister is described. The wire-mesh demister used here is constructed with galvanized iron wires 850μm in diameter, and is held perpendicular to the vertical upward flow of air laden with water droplets.Experiments have been made with mesh layers from one to four layers and for mean air velocity from 0.5 to 4.0 m/s. In the case of the vertical upward air flow, the water-film on the wire-mesh surface has important influences on the size distribution of water droplets, the separation efficiency and the pressure loss coefficient.Obtained separation performances are compared with the results predicted by theoretical analysis which has been presented before.