Abstract
Full-scale sea trials demonstrate a ship’s performance under real operating conditions to confirm whether a ship meets its specifications and requirements. The determination of the performance through a sea trial is the most important stage in the ship design cycle. If one is relying on measurements of propeller shaft power or fuel consumption, the distinction between the propeller and hull efficiencies may not be made. In order to be able to identify the propeller efficiency separate from the hull, full-scale propeller thrust should be accurately measured. In this study, full-scale measurements of the propeller thrust, torque, and revolution for a series of crude oil tankers and twin-skeg LNG carrier were conducted during the speed trials. Two different measuring systems, strain gauge and optical type, were implemented to compare the performance of sensors. As a result, it was shown that the strain gauge type-measuring device matched the model test results relatively well compared to the optical device. Above all, in the case of the optical device, it has been demonstrated that the zero setting is important to increase the accuracy of the full-scale measurements.
Highlights
The interest in developing low-resistance hull form, high-efficiency propeller and energy saving devices is rapidly increasing in shipping and shipbuilding companies in accordance with rules and regulations that require minimizing fuel oil consumption and greenhouse gas emissions
The discrepancy of the slope is caused by the gauge factor
The gauge factor is evaluated based on the shop test
Summary
The interest in developing low-resistance hull form, high-efficiency propeller and energy saving devices is rapidly increasing in shipping and shipbuilding companies in accordance with rules and regulations that require minimizing fuel oil consumption and greenhouse gas emissions. The ITTC-recommended procedures [1] assume that the form factor is the same for the model and full-scale ship and is independent of ship speed These assumptions have been investigated with model tests [2] and numerical analyses [3]. For the substantial improvement of the hull form, propeller and energy saving devices [9], it is essential to estimate ship performance in full scale and understand the scaling effect more deeply [10] because through the full-scale speed trials, the performance prediction from the model test can be verified [11]. The relation of the propeller thrust and torque due to draught and trim conditions is rarely changed, which can be confirmed by the prediction results from model tests. The results of thrust measurement at the same torque show approximately 10% difference from the model test results, mainly due to the stability of the zero value, which is found as a problem to be solved for the stable and reliable measurement of thrust
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