导管螺旋桨叶梢泄漏涡机理研究及一种推迟梢涡空化的方法

文章运用数值模拟研究了导管螺旋桨叶梢泄漏涡机理，并提供了一种推迟泄漏涡空化的方法。通过分析不同间隙时的泄漏涡的空泡数发现，随着间隙增大，最小空泡数发生了位置向下游移动，靠近桨叶吸力面，其数值减小。间隙尺寸影响梢涡空泡数的机理很复杂，可以从三个方面来解释：第一、间隙大小改变了泄漏流动速度，从而影响了泄漏涡水动力参数；第二、间隙大小影响叶梢区域压强分布，泄漏涡压强随之改变；第三、间隙大小改变了间隙内黏流的产生和发展，影响泄漏涡黏性分布。而且叶梢泄漏涡核是导管螺旋桨空泡初生位置。文中研究一种叶梢喷射流方法降低叶梢涡核压降，推迟空化初生，探究了不同喷射速度和喷射间隙高度、喷射角度对泄漏涡空泡数的影响。从模拟结果看，叶梢喷射可以降低叶梢翼型载荷，改善泄漏涡核压强分布，推迟泄漏涡空化。比较不同喷射速度，发现速度越高，越能有效提高泄漏涡核压强，速度足够高时甚至可以“吹掉”涡核；研究不同喷射间隙高度发现，间隙越高，越能有效提高泄漏涡核压强，但由于会降低了叶梢更大区域的载荷，降低了桨叶推力；喷射角度的研究表明，轻微的正向预旋对推迟叶梢空化有利。

Mechanism Study on Tip Leakage Vortex in Ducted Propeller and a Method to Delay TLV Cavitation

This paper studies the mechanism of Tip Leakage Vortex (TLV) in ducted propeller through numerical simulation and presents a method to delay TLV cavitation. From the analysis of the TLV cavitation number in different clearances, it is discovered that with increasing tip clearance, the position of the minimum cavitation number moves downstream and closer to the suction side of the blade, and the value of the minimum cavitation number decreases. The mechanism how tip clearance affects the TLV cavitation number is very complicated and can be interpreted in terms of three as-pects: (1) The change of tip clearance alters the velocity of the tip leakage flow, hence its hydrody-namic parameters; (2) It affects the pressure distribution near blade tip, along with the pressure in TLV; (3) It influences generation and development of the vorticity in tip clearance as well as in TLV. Since TLV core is the primary cavitation inception position in a ducted propeller, in order to delay cavitation inception, the blade tip injection (BTI) is numerically investigated to reduce pressure drop in TLV core. Influence of BTI parameters of injection velocity, injector gap height and injection an-gle on TLV cavitation number is studied. Simulation results reveal that the BTI can decrease the tip foil loading, therefore improve the TLV core pressure and delay TLV cavitation. The higher injection velocity can more effectively raise TLV core pressure comparing different injection velocities, and the injection of sufficient velocity even blows off TLV. The analysis of injectors of different gap heights indicates that higher gap is better at raising core pressure, but also decreases propeller thrust, as the higher gap reduces blade tip loading at larger region. The investigation of injection angle states that the injection with a slight positive pre-whirl flow is beneficial to TLV cavitation delay.