CFD在“机电一体化”导管桨性能分析及优化设计中的应用

Hydrodynamic Performance Analysis and Optimization Design of Mechatronic Ducted Propeller with CFD

将计算流体力学(Computational fluid dynamics,CFD)应用于"机电一体化"导管桨水动力性能分析和优化设计的全过程。对某后置定子式导管推进器敞水性能进行计算,在大范围进速系数下计算推力系数和力矩系数均与试验值吻合良好,检验计算方法的有效性。对初始设计导管桨水动力性能采用同样的方法进行计算,包括从流体力学的角度计算确定导管的主要尺寸,并结合网格类型和网格密度的影响分析了计算结果的有效性,分析设计工况下未缠绕线圈的环对间隙流场特征和导管、桨以及整体水动力性能的影响,提出将环变短变厚及相应改变叶片型值的改进设计思路,以改善间隙流动,提高敞水效率。对再设计导管桨设计工况和非设计工况性能进行计算,将环表面压力分布和导管桨推进性能与初始桨进行了比较,并利用水动力试验值再次检验了计算结果。结果表明:两次利用试验值校验计算值均吻合良好,说明将CFD用于导管推进器初始设计和分析是有效的。间隙径向距离大,间隙内泄压和局部滞止流动区域范围也大;环轴向距离长,环两端的间隙内流动旋涡程度也大。环的存在对导管桨导管产生推力是有利的,但对叶片产生推力是不利的,使导管桨敞水效率降低。再设计导管桨桨的推力系数比初始设计导管桨高、力矩系数低,敞水效率要高,说明改进方向正确。

Computational fluid dynamics （CFD） is applied in the whole process of hydrodynamic performance analysis and optimization design of a mechatronic ducted propeller. The open water characteristics of a ducted propulsor with a stator behind its rotor are calculated, hydrodynamic force coefficients show good agreement with the experiment data, which indicates the validity of CFD method. The hydrodynamic performances of the preliminary design mechatronic ducted propeller are calculated with the same CFD method, including putting forward the major geometrical dimensions of the shrouded duct in hydrodynamics terms by simulation, and validating the calculated results by changing the mesh type and distribution. An optimization design, which improves the tip flow and enhances the open water efficiency, can be achieved by shortening and thickening the ring and changing the blade geometry correspondingly after analyzing the effect of ring without winding to the flow pattern of tip clearance and hydrodynamics of ducted propeller, as to the component duct or propeller itself and to the whole geometry. Numerical simulation is conducted to the secondary design ducted propeller under design and off-design conditions. The calculated pressure distribution around the ring is compared with that of the preliminary one, and comparison of the propulsion performance is also completed with the second one to the first one, and to the experiment simultaneously. It is shown that the use of CFD to the preliminary design and performance analysis of the duct propulsor is effective. With a large radial distance of the clearance, the pressure reduction in the clearance and the range of local stagnation flow region will be large also. The longer the ring in the axial direction is, the more vortexes in the turnaround tip flow will be. The existence of the ring is beneficial to axial force of the duct, but not to the blade, as it makes the efficiency of the ducted propeller lower. The thrust coefficient of the redesigned ducted propeller is higher than that of the first one, moreover, the torque coefficient is lower, and the open water efficiency is higher, thus showing the correctness of the improvement.