Study Of Propeller Hydrodynamic Performance Under Ice-Propeller-Flow Interaction

In recent years,with the rising concern of the international community on the Arctic waterways and polar resources,the research on ice-going ships has received more attentions and made considerable developments.Because of the multi-operating condition of ice-going ships,the working environment of its propulsion device is different from conventional ships.Especially in the ice-breaking condition,the brash ice frequently soaks to the ship's bottom surface,skids to the flow field in front of the propeller,produces extreme loads on propeller blade,influents on hydrodynamic performance of propeller and even causes serious noise,vibration and cavitation problems.By combining potential flow panel method,viscous flow CFD technology and model test,the thesis conducted an in-depth and systematic study on the load and performance of propellers operating in the ice conditions.It analyzed the hydrodynamic performance of the propeller under the multi-operating conditions,carried out researches on calculation methods of steady and non-steady propeller performance under the ice disturbance,discussed influence rules on propeller hydrodynamic performance with different ice geometry parameters and positions,carried out unsteady analyses on the interaction between ice and propeller in viscous flow field,conducted a series of propeller's model test studies on interaction problems between ice and propeller in the non-contact condition,and compared with the theoretical and numerical methods.In order to discuss the hydrodynamic performance of propeller under the multi-operating conditions in ice area,this thesis took a controllable pitch propeller as the study object,based on panel method and the principle of coordinate transformation,calculated thrust and torque,efficiency,and spindle torque of propeller with different main parameters and working conditions,systematically discussed the influence laws on the hydrodynamic performance of controllable pitch propellers according to different geometric parameters.It also simulated blade section distortion in the control pitch process,analyzed the influences of rake,skew,blade area ratio and hub diameter ratio on the hydrodynamic performance.The conclusions showed that the pressure distribution and the hydrodynamic coefficient of propeller which were effected by the blade distortion were different in heading and astern condition,however,the effect to cavitation was opposite in the above situation.The effect to spindle torque was subtle,but the effect to efficiency was considerable.Based on the potential multi-body panel method theory and the induced velocity iterative method,it simulated the interaction between propeller and ice by the numerical methods.Taking Icepropeller I as the model propeller,ice-class propeller's thrust and torque under different advanced speeds were calculated,and the numerical results were compared with experimental results ro verify the feasible of the method.At the same time,the influences on pressure distribution,radial circulation distribution and induced velocity by ice block in the flow field were analyzed.Calculation results showed that presence of ice block will cause the pressure distribution of radius blade sections to change.The pressure on blades suction side become smaller,the pressure on pressure side will increase,which increases the propeller whole thrust.In addition,ice creates a blocking zone in the propeller disk with high flow,and that is more obvious under high advance coefficient condition.In order to further study the effect laws on hydrodynamic performance of propeller by the different ice geometric sizes and positions during the interaction between ice and propeller,based on the steady calculation method of ice-propeller disturbance,the paper carried out the preliminary impact analysis of propeller steady performance.Results showed that effects of ice on the propeller were generated at both the area of propeller wake region situated in part of the propeller disk area inside and the relative position between interfere region and propeller.Results showed that the ice disturbance increases with the reduction of the axial distance,also,the tendency was more obvious before the axial distance DA=2R,andand the ice disturbance can be neglected when DA>5R.In the propeller disk range,interference increased with the radial position of the ice,and the maximum value can be obtained nearby the 0.7R position.The ice width and thickness greatly effected on propeller performance,but the influence of the length change was small.Based on potential flow theory unsteady panel method with lifting body and non-lifting body interference,the paper established unsteady method for solving ice-propeller interference problem in non-contact condition.The ice model used non-lift body quasi-steady panel method theory to calculate the induced velocity of propeller,the propeller used lift body unsteady panel method theory to calculate the induced velocity interference on ice model.The interaction between ice and propeller was solved by iterative calculations,until the propeller's unsteady hydrodynamic performance converged.The unsteady hydrodynamic performance calculation was carried out using this algorithm,and propeller's thrust and torque and axial force fluctuation were computed under the effect by single block ice,multi-block ice and ice model of various shapes,the unsteady characteristic of propeller were analyzed in the ice block effect under different ice propeller positions and different model sizes.Calculation results indicated that this calculation method can be used to research unsteady characteristics of ice-propeller interference;when ice position changes along the radial direction on the propeller disk,the amplitude of,thrust and torque was dominated by first-order,and the effect of ice model shapes on main component of each order thrust and torque amplitude was minimal,but it will affect the size of each order amplitude.Based on the viscous fluid dynamics theory,combined with overlapping grids,the paper carried on the simulation forecast about the ice class propeller's hydrodynamic performance and flow characteristics in cutting condition.Trimmed Mesh was used in the entire calculation domain,and theoverlay grid method was used for the information transfer between propeller rotation calculation domain and the ice surface computing domain.The mesh of blade surface,ice surface and clearance of ice and propeller were used partial encryption processing,as to obtain the flow field data in detail and to ensure the accuracy of the grids' data.,Simultaneously by using the SST k-? turbulence model,the computation analyzes of influences on the propeller hydrodynamic parameters,the surface pressure and the flow field situation under the different gaps between the cutting ice and propeller.Results showed that the viscous flow computation method which based on overset grid method for solving interference problems with the ice had better usability and reliability.After the blade turned into the ice effect domain,in the leading edge near the leaf area,the change of the pressure gradient will increase,the significant high pressure area will appear,and the high pressure area range will increase as the increasing blade area in ice effect domain.In the Harbin Engineering University horizontal circulating water tank,the experimental research was carried out to measure the influence on disturbance hydrodynamic performance during the ice-propeller interaction process with different advance speeds,ice sizes and relative positions.It took Icepropeller I as the model propeller,the test results and calculation resultshad been compared in order to verify each other.It indicated the model test results and the computed results have a good uniformity which can confirm the reliability and the accuracy of the proposed method in this thesis.