A Method for Calculating the Hydrodynamic Characteristics of the Nozzle Propeller

Abstract

With a recent tendency toward larger-sized and higher-powered ships the lowering of the propeller efficiency due to the increase of the propeller load is becoming a problem. Because of this, some attempts have been made to use other propulsion devices than a conventional propeller. Of these devices, a nozzle propeller has been actually adopted on large vessels, and several comparison data of performance between this and conventional propeller have been published.In the nozzle propeller, the propulsion system consists of the nozzle and the propeller. It involves new complicated problems in the point that various performances depend on the strong interaction between the nozzle and the propeller. It is, therefore, desired to make further theoretical and experimental clarification.In this paper we aimed at grasping the performance of the axisymmetric nozzle propeller in axisymmetric flow as a starting point of theoretical clarification. That is, by combining and iterating the propeller lifting line theory and annular lifting surface theory we carried out the performance and mean velocity field of the nozzle propeller and compared them with the test result. And further, we made the same calculation and test for the conventional propeller and made direct comparison of the performance and mean velocity field of the nozzle propeller and the conventional propeller. From this we could grasp the macro- and micro-scopic performance of the nozzle propeller.