Fig.2 Schematic of Experiment of Water Droplet Flow
To get the optimum distance between the scanning lines, the distribution of the droplet flow is to be grasped. As shown in Fig.2, the distance between the nozzle and the test wall is 5 m, and the angle of elevation is 8°, the diameter of nozzle is 2.5 mm, the water pressure is 250 kPa, then the water jet is shot to the test wall. As test liquid, glycerin, ethylene glycol and water, which were colored with red dye were used. The test liquids were spread with a brush on the test board. The state of washing is photographed with motor driven camera, and the washing effect state on upper ward, dawn ward, right side and left side is investigated. The distribution of quantity of water droplet flow is obtained with using 8 mm diameter pipe freed to the traverse. Then the quantity of water droplet per time, per area is calculated.
2.2 Washing with falling film flow
In order to estimate the rate of washing out the clinging liquid film hα (μm/s), the apparatus for washing with falling water film flow is made as shown in Fig.3. The outer diameter is 60 mm and the length is 2070 min. In this test, the rather thick film flow is tested as it is stable. The test section is from 250 mm to 750 mm under upper end and the test liquid is spread with brush. The amount of the thickness of the clinging liquid is given by dividing amount of clinging liquid by test surface area. The state of washing is caught with a motor driven camera and the needed time to wash out is obtained. Dividing clinging film thickness with washing time, the rate of washing out the clinging liquid hα is obtained.
Fig.3 Test apparatus for washing with falling water Filmflow
3 Result and Discussion
3.1 Washing with water droplet flow
Using red colored water (Viscosity: 1.4 mPa, Average thickness of clinging liquid film: 16 μm), red colored ethylene glycol (Viscosity: 20 mPa-s, Average of clinging film thickness: 24 μm) and red colored glycerin (Viscosity: 900 mPa-s, Average clinging film thickness: 42 μm), the washing test with water droplet flow is done. In any case of them, the clinging liquids were washed easily with droplets flow. An example of result about the high viscosity liquid case of glycerin is shown in Fig.4. In these experiment, the test liquid is spread with brush. In the case of adhered by sprinkling, the film thickness of glycerin was 56 μm, the one of ethylene glycol was 15 μm, the ease of colored water was 17 μm.
Fig.4 Washing of Colored Glycerin
When the clinging liquids are water-soluble, the effect of viscosity is small. The comparison between the case of the jet flow where the distance from the jet nozzle and the test wall is 0.65m, and the case of water droplet flow where the distance from the jet nozzle to the test wall is 5 m is shown in Figure 5. In the case of the washing with water droplet flow, the wide extent is washed at the same time. In the case of washing of water jet flow, the washing is done with water film flow film center to outside according to the time lapse. In Figure 6, the distribution of water droplet flow is shown.
