来流条件对轴流喷水推进器性能的影响研究

Performance of Axial Water-Jet Propulsor under Different Inflow Conditions

关键词:  喷水推进器  来流条件  推进性能  内流特性  数值模拟

Key words:  Water-jet propulsor  Inflow conditions  Propulsion performance  Internal flow performance  Numerical simulation

摘要:

高速舰船在实际航行过程中的来流条件十分复杂，为研究不同来流条件对喷水推进器性能的影响，以轴流式喷水推进器为研究对象，基于均相流模型、Zwart空化模型和SST k-ω湍流模型，对不同来流速度和来流角度条件下的喷水推进器进行了数值模拟，通过网格不确定度分析、数值与试验结果对比及误差分析验证了数值计算方法的可靠性，最终获得了不同来流条件喷水推进器推进性能和内流特性的变化规律。结果表明：随着来流速度增大，装置流量不断增加，扬程、推力和效率先增大后减小，在来流速度为5.6m/s时性能最佳。转速为2450r/min时，叶轮空化程度较弱，当来流速度v≥8.4m/s时，流量显著增大，冲角减小，叶片工作面流动分离增强，压力面开始出现空泡。来流角度增大对低来流速度工况喷水推进器性能几乎无影响，高来流速度工况则表现出推力、扬程和效率的急剧下降，来流角度从3°增加至7°时，推力、扬程和效率降幅分别高达13.8%，13.9%与8.3%。来流角度增大，各过流部件速度不均匀性增大，叶轮和导叶区域湍流耗散增大，叶轮进口冲角减小，压力面流动分离增强，做功能力下降，推进装置性能急剧恶化。

Abstract:

The inflow conditions of high-speed ship are significantly complicated during the process of navigation. To reveal the influence of inflow conditions on propulsion performance， this paper conducted the numerical simulation under different inflow velocities and angles of the axial water-jet propulsor. The characteristics of propulsion and internal flow characteristics under different inflow conditions are obtained based on the homogeneous flow model， Zwart cavitation model and SST k-ω turbulence model. The reliability of the numerical calculation method is verified according to the grid uncertainty analysis， comparison between numerical and experimental results and the error analysis. It is found that the flow rate increases continuously， however， the head， thrust and efficiency increase firstly and then decrease with the increasing inflow velocity. The best performance of propulsion is obtained at v=5.6m/s. The cavitation occurred on the impeller is slight when the rotational speed is 2450r/min. When the inflow velocity is not less than 8.4m/s， the flow rate increases significantly， which leads to the reduction of incidence angle. Therefore， the flow separation on pressure surface is enhanced and cavitation appears on this condition. The increase of inflow angle slightly affects the propulsion performance under lower velocity condition. However， the higher inflow velocity leads to the substantial decline of thrust， head and efficiency， which decrease by 13.8%， 13.9% and 8.3%， respectively， when the inflow angle changes from 3° to 7°. The velocity inhomogeneity of each overcurrent component and the turbulence dissipation of the impeller and guide vane significantly increase with the increase of inflow angle. Moreover， the decrease of incidence angle strengthens the flow separation on pressure surface. All of those weaken the working capacity and result in a sharply deterioration of propulsion performance.