Study Of The Effect Of Attack Angle Of The Duct And The Parameters Of The Tandem Arrangement On Propeller

Ducted propellers and tandem propellers are designed and manufactured on the basis of the wide application of ordinary marine propellers.The original design intention of the ducted propeller is to avoid the collision between the propeller and the foreign bodies,so a duct is added on the outside of the propeller.However,it is found that the ordinary propeller with a duct can make the ship travel faster and make less noise,with a higher hydrodynamic efficiency;tandem propeller is a propulsion device with two ordinary propellers installed on the same axis,and the two propellers rotate in the same direction.Compared with the single propeller system,the hydrodynamic efficiency is significantly improved and the vibration from the stern is significantly reduced under heavy load condition.In this paper,the hydrodynamic and hydroacoustic performance of the single KP458 propeller,ducted propellers with different attack angles（15°≤θ≤45°）and the tandem propellers with different spacing ratio and diameter ratio will be studied in detail under different advance ratio（0≤J≤0.75）conditions.The computational fluid dynamics method,ANSYS Fluent software,MRF method and RNG k-?turbulence model will be adopted.About the hydrodynamic performance research,the hydrodynamic performance of 15°ducted propeller,20°ducted propeller,30°ducted propeller and 45°ducted propeller is calculated.The results show that K_T,K_Q and?₀ of single propeller are larger than those of ducted propellers when J is less than 0.4,and the hydrodynamic performance of ducted propeller is better than that of single propeller when J is larger than 0.65.In addition,the thrust coefficient and torque coefficient of ducted propellers increase with attack angle,while the hydrodynamic efficiency of 30°ducted propeller is higher than that of other ducted propellers under a condition of larger advance ratio.For the tandem propeller,the results show that when the diameter ratio is 1.0,K_T reaches the maximum when the spacing ratio is0.29,while?₀ reaches the maximum when it is 0.3.When the spacing ratio is 0.29,K_T reaches the maximum when the diameter ratio is 0.97 and?₀ reaches the maximum when the diameter ratio is 0.95.About the hydroacoustic performance research,FW-H acoustic model is adopted to calculate the sound pressure level spectrums of single propeller and ducted propellers under different advance ratios.The results show that when the frequencies are at 1^st,2^nd and 3^rdBPFs,the sound pressure level of single KP458 propeller and ducted propellers is relatively higher.In addition,the sound pressure level of single KP458 propeller decreases with advance ratio,and the sound pressure level of ducted propeller is higher than that of single propeller,and it increases with attack angle.The noise directivity of single propeller and ducted propeller is also studied.It is found that the sound pressure level of 15°ducted propeller is the highest when J=0.6,and it does not change monotonously with advance ratio.The broadband noise of a 20°ducted propeller is calculated,and the distribution of acoustic power level on the blade surface is analyzed.The higher acoustic power level is distributed at the tip and leading edge of the blade,and the lower acoustic power level is concentrated near the hub of the propeller.The calculated acoustic power level distribution is consistent with the results calculated by FW-H acoustic model.