Analysis of The Effect of Pitch Angle on Propeller Modification by Considering Wake Distribution on Propeller Performance

Abstract

The propeller is an important component of the ship’s propulsion system, and its design related to the safety and ship’s cost. The propeller is operated in an uneven flow field behind the ship so it has an important influence on the cavity, vibration and hydrodynamic performance. Therefore, optimization calculations are needed to get most economical in addition to meeting the provisions of the Energy Efficiency Design Index. Optimization software through polynomial regression values can be used for selecting propeller. However, when the propeller is installed on the hull, the Velocity Advance (Va) on the propeller will change from the distribution at the time of the open water test because of the shape of the hull. This reduces the performance of propeller. So it is necessary to calculate the engine propeller hull matching to get a match on each propulsion component. Blade element theory concept can be used in designing the propeller for the engine hull matching, with the hypothesis that if the pitch angle is greater than Va, cavitation will occur. This condition is not allowed and if the pitch angle is too small for Va, the thrust cannot be maximized against flow, then it must adjust to the Velocity Advance (Va) distribution on the ship’s hull, because increasing the thrust value will also increasing propeller’s relative rotative efficiency (ηR) and open water efficiency (ηO) and hull efficiency (ηH). This situation makes a proportional increase in the value of the propulsive coefficient. The simulations are carried out on the size of the model with a dual domain (single-hull) by turning the propeller while the ship is stationary and seeing the convergent speed generated by the ship. The simulation data that will be taken are propeller thrust and torque because these values are considered sufficient to compare the simulation results. It’s getting the thrust foil value that making model S_T, S_eta and S_KomL S_T model is done by looking at the highest thrust, S_eta model with highest efficiency method and on S_KomL with highest thrust and efficiency by looking at the streamlined model, the thrust and efficiency values are equal to or higher of the MP687. It is showed that open water efficiency value in the two modified models has decreased, namely S_T model of 0.341, S_KomL of 0.345 and S_eta of 0.301 with original MP687 model of 0.371. While the hull efficiency of S_T model has decreased to 1,449 and S_KomL model increased by 1,591 and S_eta model increased by 3.8 but in MP687 model was 1,526, and the relative rotate efficiency of S_T model increased to 1,096, S_KomL model also increased by 1,099 and also S_eta model of 1.08 which originally on the MP687 1,055 model. This will result in the Propulsive Coefficient (PC) value in S_T model of 0.543 with decreasing, S_KomL 0.604 and S_eta 1.25 with an increase from the original MP687 0.597