Film cooling behavior in thin rectangular channel was studied experimentally by using water. The film thickness and the wall temperature distribution were visualized with an ink and a thermochromic liquid crystal sheet, respectively. The wavy temperature distributions on the wall just after injection slit was observed in spite of the two-dimensional film. The empirical film cooling model by Goldstein et al., which was developed based on gas flow, failed to predict the film cooling effectiveness using water. The k-ε low Reynolds number turblent model predicted well the experimental results of the relatively low injection rate but overestimated the film cooling effectiveness at the higher injection rate. The overestimation was considered to be due to the underestimation of fluid mixing near the wall in the model.
For the water quality control of marine boiler, it is very important to investigate the effects of sea water mixing on the conditions of boiler water quality such as pH, concentrations of phosphoric ion PO43-, chloric ion Cl-, and electric conductivity EC. At first, the paper investigates theoretically the change of pH, that is molarity of hydroxyl [OH-], PO43- concentration and EC due to mixing of sea water into boiler water by the consideration of the chemical reactions between scale components and phosphate/alkali type of water treatment chemicals. According to this investigation, the paper proposes a method of automatic water quality control. Secondly the paper carries out an experimental study by the use of an actual boiler in order to confirm the validity of the above theoretical investigation. The experiment reveals the followings; (1) There is some difference between the theoretical estimation and the measurement result regarding the change of pH, PO43- concentration and EC due to sea water mixing. It is found, however, the difference has a certain regular trend being related with the mixing rate of sea water. (2) The PO43- concentration can be arranged corresponding to the addition rate of some blended type of phosphate/alkali treatment chemicals even when Cl- concentration is high, provided that hardness components do not exist. (3) When the pH is kept around 11.0, there are good correlations between concentration of [OH-] and concentrations of P-Alkalinity, M-Alkalinity and PO43-, and also between EC and Cl-. Using adequately these correlations, therefore, there would be a possibility of automatic control of boiler water quality.
In order to establish several techniques of cleaning, deburring and scaling by high-speed water-jets in air, we carefully observe the eroded surface on aluminum-alloy test-pieces in relation to the breakup length of the jet. The impact pressures induced by the impinging jet are also measured by means of pressure-sensitive film. Our experiments are carried out by using the jet test device of 0.5mm in nozzle diameter and 117m/s in jet velocity. The experimental results are as follows : The detected impact pressures were found to be of the order of 130MPa at 117m/s jet velocity. The central concentrated pressure on the impinging surface was observed to be very high locally. Good correlations were found between the impact pressure at the jet axis and maximun erosion depth. The actual erosion pattern on the aluminum specimen was closely related to the distribution of the detected impact pressure in the defused flow region.