Research On Hydrodynamic Performances Of HCRSP

Propeller is one of the most widely used thrusters in modern ship industry,which plays an important role in ship propulsion.As one of special propellers,contra-rotating propeller is widely used in engineering for the advantage of energy-saving and high efficiency.With the development of integrated electric technology,podded thruster is invented.Then ABB company combines it with contra-rotating propeller,and podded contra-rotating propeller is introduced,which has the advantages of both podded thruster and contra-rotating propeller,such as full utilization of energy,flexible arrangement and full circle swinging,and has received great concerns.Such thruster was named Hybrid Contra-Rotating Shaft Pod(HCRSP)at the 27th ITTC Conference.In this paper,HCRSP is researched to explore the affecting factors of hydrodynamic performance,specifically as follows:(1)The numerical simulation of HCRSP is carried out in STAR-CCM+,and the results are compared with experimental data to verify the reliability of CFD method.On this basis,the spacing between the front and rear propellers is changed and the open water performance of HCRSP is investigated.Through comparative analysis,it can be seen that with the increase of the spacing between the two propellers,for the rear propeller,the utilization ratio of the front propeller wake and the open water efficiency of HCRSP decrease gradually,and the decreasing rate of open water efficiency is slowing down.In practical application,on the basis of ensuring its steering performance,it is better to minimize the spacing between the two propellers as possible to give full play to its advantages.(2)Based on HCRSP with the optimum spacing,the effects of rake of the front and rear propellers on hydrodynamic performance are studied by CFD method.Comparing the obtained results with that of HCRSP without rake,it is found that the rake on the front propeller mainly affects the thrust of the front propeller,and there is no obvious difference between the performances of HCRSP with the rake angle of 5° and 10° on the front propeller;as for the rake of 50 and 10° on the rear propeller,they have certain influence on the thrust and torque of both front and rear propellers.For the HCPSP with 50 rake on the rear propeller,the thrust and torque of the rear propeller have decisive influence on the overall performance,and it also proves to have better performance.The optimum combination of rake is that both front and rear propellers are inclined 5° longitudinally,and its hydrodynamic performance is calculated numerically.Through comparative analysis,it is found that the hydrodynamic performance of HCRSP with 50 rake on both propellers is similar to that with 50 rake on the rear propeller,which indicates that the rake on the rear propeller has greater influence on hydrodynamic performance than rake on the front propeller.Moreover,for HCRSP with rake on single propeller and both propellers,the open water efficiency decreases under J<1.0,increases under J>1.0,and the maximum efficiency point moves backward,therefore,the rake is beneficial to high-speed HCRSP.(3)Taking the HCRSPs with and without 50 rake on both propellers as research objects,the hydrodynamic performances of which under J=1.1 and steering angle of-20°?20° are calculated.The results show that with the increase of the steering angle,the transverse deflection force of rear propeller(including pod)increases gradually,while the axial thrust decreases gradually,even negative value appears.Therefore,the open water efficiency decreases with the increasing steering angle,and the HCRSP with 50 rake on both propellers has higher open water efficiency at each steering angle than that without 5° rake on both propellers.