워터젯 추진 선박의 유량 측정을 위한 T관 설계

Abstract

Abstract The momentum flux method is generally employed to evaluate the powering performance of waterjet propulsion vessels since it was proposed in the 21st International Towing Tank Conference (ITTC) High-Speed Marine Vehicle Committee. It is important to accurately estimate the flowrate of the waterjet system to effectively implement the method. In KRISO towing tanks, we use the relation between thrust and pressure in bollard pull condition to improve the accuracy of the estimated flow rate under self-propelled conditions. However, in this method, it is difficult to determine the position of the pressure sensor when the waterjet nozzles are exposed above free surfaces. In this study, direct thrust measurements and pressure measurement techniques were compared in terms of measuring the flowrate precisely. For the waterjet system and ship models, the RV Athena model was used, which was discussed in the benchmark study of 24th ITTC Special Committee on Waterjets. The direct thrust is measured using a T-shaped tube. This tube is designed through a preliminary experiment using a magnetic flowmeter and load cell. In this experiment, the final designed T-tube exhibited sufficient correlation between the measured flowrate and the calculated flowrate from momentum equation. The direct thrust by the designed T-tube and pressure are measured under the bollard pull condition for the RV Athena model. The derived flow rate from each technique is compared with benchmark test results.