机匣开槽控制喷水推进器不稳定流动的数值研究

针对喷水推进器小流量工况下的驼峰区不稳定流动,采用计算流体力学方法研究了其失稳特性。结果表明,随着流量的减少,推进泵的扬程和效率显著下降,扬程曲线在0.42Qd~0.8Qd范围内呈现出正斜率的驼峰特性,同时内部流场变得紊乱,并出现流动分离和回流等现象。为了改善这一不稳定流动,采用了机匣开槽技术进行流动控制,使驼峰现象得到明显改善。在最佳槽体结构参数下,深度失速工况点的扬程和效率分别比原模型提高了约147.6%和70.3%。机匣开槽一方面能够对进口来流进行整流,起到减少预旋和增大轴向进流速度的作用,另一方面可以抑制主流区漩涡的形成以及叶轮进口位置的低频压力脉动。

基于DDES耦合FW-H方法的吊舱推进器水动力噪声特性

为研究吊舱推进器非定常流场和诱发的声场结构,采用DDES耦合FW-H方法,对其开展了高精度非定常数值计算.结果表明:由于吊柱诱发的强烈动静干涉作用,使螺旋桨至吊柱区域内的压力脉动幅值上升;吊舱推进器的涡量分布较为复杂,由于吊舱体的扰流作用,除螺旋桨本身产生的主、副涡外,还出现干涉尾涡结构,且主涡区向上偏移.通过计算盘面上各个声接收点处的谐波频率标准差发现,声场在浆盘面上无明显声指向性.通过设置空间曲面内的声接收点阵列,获得了吊舱推进器的声场空间分布特性.发现轴频和叶频始终是其主要频率;在螺旋桨桨盘面附近的声压脉动无明显指向性,但在空间曲面上,轴频和叶频的分布特征明显,存在有明显形状的高低值区;在吊舱推进器后方,声压逐渐衰减,但叶频处能量衰减趋势小于轴频处.

基于沟槽结构的泵喷推进器导管脉动压力控制研究

本文借鉴航空发动机中的压气机“处理机匣”技术,在泵喷推进器导管内壁开设一定数量的轴向沟槽结构,用于减弱泵喷推进器的梢涡,从而减小泵喷推进器导管内壁上的脉动压力。结合分离涡模拟(DES)方法和滑移网格方法对椭圆形水翼的梢涡流场进行数值模拟,数值计算结果与试验值吻合度较高,验证了数值计算方法的可靠性与适用性。在此基础上,分别对有无沟槽结构的泵喷推进器进行数值模拟,对比分析沟槽结构对梢涡涡核压力、导管内壁脉动压力和水动力性能的影响。结果表明:沟槽结构可以显著增大梢涡涡核压力,并对导管内壁面上脉动压力幅值有明显的降低效果,且对水动力性能影响较小。

轮缘驱动泵喷推进器的螺旋桨性能优化方法

为得到适用于新型轮缘驱动泵喷推进器的螺旋桨,在传统泵喷推进器螺旋桨的基础上进行性能优化方法研究十分必要。利用CFD数值模拟方法对推进器进行水动力仿真,分别对比3个不同的螺旋桨孔径比和3种桨叶厚度分布方案对推进器敞水性能的影响。对比结果发现小孔径比对推进器敞水性能更为有利,其中0.1孔径比推进器比0.3孔径比推进器的敞水效率最大提升了3.25%。厚度反置导致轮缘驱动螺旋桨高半径处压力分布不均匀,扭矩大幅提升,敞水效率大幅降低。轮缘驱动螺旋桨的厚度越小,扭矩越低,敞水效率越高,其中方案C桨的扭矩比方案A最大降低了21.74%,敞水效率最大提升了12.9%。

泵喷推进器间隙流场尺度效应数值研究

由于泵喷推进器转子与导管之间有间隙的存在,内流场特性较复杂.为了探究尺度效应对泵喷推进器间隙流场的影响,采用非定常雷诺平均Navier-Stokes(URANS)方程和SST k-ω湍流模型,利用全结构化网格对计算域进行离散处理,滑移网格用于处理转子和其他部件之间的相对运动.首先通过网格不确定分析来验证本文数值方法的可行性,数值计算结果与模型试验数据进行了比较,两者吻合良好;然后对3种尺度泵喷推进器模型的敞水性能进行了数值计算,从涡量场和压力场的角度进行了分析.结果表明,全进速系数下,实尺度模型的效率会提高;实尺度模型的叶梢泄漏涡(TLV)涡量溃灭提前,涡量强度更低,并且TLV涡核中心压力系数更小,间隙间的脉动压力幅值更低.

斜航工况下吊舱推进器水动力性能数值及试验研究

为了探讨吊舱推进器在斜航工况下的水动力性能变化,以某豪华邮轮吊舱推进器为研究对象,采用STAR CCM+软件基于RANS(Reynolds-averaged Navier-Stokes)方法并结合标准速系数和偏转角的水动力性能进行数值模拟。同时,利用拖曳水池和吊舱动力仪进行试验研究,并与仿真数据进行比较分析,进一步讨论螺旋桨与吊舱之间的相互作用对水动力性能的影响。结果表明,本文采用的数值模拟方法可较准确预测斜航工况下的水动力性能。螺旋桨推力系数、扭矩系数关于直航工况点对称,其数值随着偏转角的增大而增大;吊舱单元推力系数随着偏转角的增大而减小,吊舱侧向力随着偏转角的增大而增大;螺旋桨单元流场压力和流速在叶梢处达到最大值,吊舱左侧比右侧承担更多的表面压力幅值。

后置定子泵喷推进器噪声辐射特性分析

为了探究后置定子对泵喷推进器噪声的影响,本文利用杆-翼模型完成了噪声数值方法的验证,并基于分块结构性网格对研究模型进行了瞬态模拟。分析了后置定子对流场的影响,提取了模型周围若干监测点噪声数据,探究了其噪声辐射特性。结果表明:定子叶片增大了转子尾流的轴向速度,提高了推进器的推进性能;定子叶片还能够平衡转子产生的压力涡旋,均匀尾流压力;从整体声场指向性分布来看,在轴向方向转子噪声占据主导影响,在小范围的径向方向导管噪声对整体噪声影响较大,定子噪声对整体噪声影响最小;随着距离增加,声场中的低压区指向性由前缘120°和240°向中部收缩,最终整体呈现“∞”型;在轴向方向低频段噪声衰减最快,并且随着距离的增加,衰减速度越来越快,在径向方向上,低频段噪声衰减速度变化并不明显。

后置定子泵喷推进器压力脉动特性分析

基于改进的延迟分离涡模型对后置定子泵喷推进器瞬态流场进行数值模拟,所得推力计算值与试验值最大误差为4.68%,验证数值模拟的可靠性。分析泵喷推进器近流场压力脉动时频域特性,研究多工况下后置定子表面压力系数、声压脉动时均值的分布规律。结果表明,泵喷推进器内压力脉动主要受转子影响,脉动周期与转子旋转周期一致,频域峰值出现在低频段且均为转子叶片通过频率的整数倍;后置定子平衡转子扭矩的做功区集中在定子前缘,并沿弦向贡献逐渐降低,尾缘约1.8%定子弦长位置对平衡扭矩近乎无贡献;前缘是定子噪声的主要贡献源,在高进速系数下,尾缘表现为定子噪声的次要贡献源,随着进速系数的降低,尾缘对定子噪声贡献逐渐降低。

泵喷推进器梢涡空化计算方法

在泵喷推进器梢涡流动数值计算中,转子梢部涡系对转子梢部附近网格质量要求极高,为了准确计算转子梢涡空化,本文首先完成梢涡空化观测试验,并根据空化试验条件布置数值计算,分析常用多通道周期性结构网格在计算准确性上的不足,进而在其基础上,结合梢涡流动特点,提出一种在转子域中进行局部网格重构的方法。通过数值计算结果与空泡观测试验结果对比显示,本文所提出的计算方法既能够满足梢涡空化计算对局部网格质量的超高要求,又能以较少的网格量准确预测梢涡空化。

Numerical and Experimental Studies on the Propulsion Performance of A Wave Glide Propulsor

This paper introduces a newly developed Unmanned Wave Glide Vehicle （UWGV）, which is driven only by extracting energy from gravity waves, and presents a comprehensive study on the propulsion performance of the UWGV＇s propulsor-Wave Glide Propulsor （WGP） in a regular wave. By simplifying the WGP as six 2D tandem asynchronous flapping foils （TAFFs）, a CFD method based on Navier-Stokes equations was first used to analyze the hydrodynamic performance of TAFFs with different parameters of non-dimensional wave length rn and non-dimensional wave height n. Then, a series of hydrodynamic experiments were performed. The computational results agree well with the experimental results when n〈0.07 and both of them show the thrust force and input power of the WGP are larger at smaller m or larger n. By analyzing the flow field of TAFFs, we can see that a larger m is beneficial to the forming, merging and shredding of the TAFFs＇ vortices; as TAFFs are arranged in tandem and have the same motions, the leading edge vortex and wake vortex of the TAFFs are meaningful for improving the thrust force of their adjacent ones.

RANS Simulation of Podded Propulsor Performances in Straight Forward Motion

The Computational Fluid Dynamics （CFD） approach is adopted to study the steady and unsteady performances of the podded propulsor by the Fluent software package. While the interactions of the propeller blades with the pod and strut are time-dependent by nature, the mixing plane model is employed firstly to predict the steady performance, where the interactions are time-averaged. Numerical experiments are carried out with systematically varied mesh sizes to investigate the dependence of the predicted force values on the mesh sizes. Furthermore, the sliding mesh model is employed to simulate the unsteady interactions between the blades, pod and strut. Based on the numerical results, the characteristics of unsteady hydrodynamic forces are discussed, and the applicability of the mixing plane model is investigated for puller-type podded propulsor.

Simulation of Hydrodynamic Performance of Drag and Double Reverse Propeller Podded Propulsors

The unsteady performance of drag and double reverse propeller podded propulsors in open water was numerically simulated using a computational fluid dynamics （CFD） method. A moving mesh method was used to more realistically simulate propulsor working conditions, and the thrust, torque, and lateral force coefficients of both propulsors were compared and analyzed. Forces acting on different parts of the propulsors along with the flow field distribution of steady and unsteady results at different advance coefficients were compared. Moreover, the change of the lateral force and the difference between the abovementioned two methods were mainly analyzed. It was shown that the thrust and torque results of both methods were similar, with the lateral force results having the highest deviation

Experimental Study on Hydrodynamics of L-type Podded Propulsor in Straight-ahead Motion and Off-Design Conditions

Experimental tests were conducted to evaluate the hydrodynamic performance of an L-type podded propulsor in straight-ahead motion and off-design conditions using an open-water measuring instrument developed by the authors for podded propulsors, a ship model towing tank, and under water particle image velocimetry （PIV） measurement systems. Under the three types of conditions, the main parameters of an L-type podded propulsor were measured, including the propeller thrust and torque, as well as the thrust, side force, and moment of the whole pod unit.In addition, the flow field on the section between the propeller and the strut was analyzed. Experimental results demonstrate that the dynamic azimuthing rate and direction and the turning direction affect the forces on the propeller and the whole pod unit. Forces are asymmetrically distributed between the left and right azimuthing directions because of the effect of propeller rotation. The findings of this study provide a foundation for further research on L-type podded propulsors.

Research of Podded Propulsors with Varied Geometry in Viscous Flow

Based on the model test of podded propulsor in straight forward motion, the paper presents the results of the effects of geometric parameters on the propulsive characteristics of podded propulsors in viscous flow. Three main geometrical parameters, i.e. pod diameter, strut distance from the propeller plane, and the maximum thickness of strut are studied with systematically varied geometry while the parameters of propeller blades are fixed. The RANS approach is adopted to study the steady perfomaance using the Huent software package. While the interactions of the propeller blades with the pod and strut are time-dependent by nature, the mixing plane model is employed to predict the steady perfomlance. In considera- tion of the complexity, the research does not deal with the effects of the combination of such three main parameters.

Flapping dynamics of a flexible propulsor near ground

The flapping motion of a flexible propulsor near the ground was simulated using the immersed boundary method. The hydrodynamic benefits of the propulsor near the ground were explored by varying the heaving frequency (St) of the leading edge of the flexible propulsor. Propulsion near the ground had some advantages in generating thrust and propelling faster than propulsion away from the ground. The mode analysis and flapping amplitude along the Lagrangian coordinate were examined to analyze the kinematics as a function of the ground proximity (d) and St. The trailing edge amplitude (\(a_\mathrm{tail}\)) and the net thrust (\(\overline{{F}}_x\)) were influenced by St of the flexible propulsor. The vortical structures in the wake were analyzed for different flapping conditions.

Influence of Ice Size Parameter Variation on Hydrodynamic Performance of Podded Propulsor

During ice-breaking navigation, a massive amount of crushed ice blocks with different sizes is accumulated under the hull of an ice-going ship. This ice slides into the flow field in the forward side of the podded propulsor, affecting the surrounding flow field and aggravating the non-uniformity of the propeller wake. A pulsating load is formed on the propeller, which affects the hydrodynamic performance of the podded propulsor. To study the changes in the propeller hydrodynamic performance during the ice podded propulsor interaction, the overlapping grid technique is used to simulate the unsteady hydrodynamic performance of the podded propulsor at different propeller rotation angles and different ice block sizes. Hence, the hydrodynamic blade behavior during propeller rotation under the interaction between the ice and podded propulsor is discussed. The unsteady propeller loads and surrounding flow fields obtained for ice blocks with different sizes interacting with the podded propulsor are analyzed in detail. The variation in the hydrodynamic performance during the circular motion of a propeller and the influence of ice size variation on the propeller thrust and torque are determined. The calculation results have certain reference significance for experiment-based research, theoretical calculations and numerical simulation concerning ice podded propulsor interaction.

Influence of fins on tractor-type podded propulsor performance

A mathematical model of podded propulsors was established in order to investigate the influence of fins. The hydrodynamic performance of podded propulsors with and without fins was calculated, with interactions between propellers and pods and fins derived by iterative calculation. The differential equation based on velocity potential was adopted and hyperboloidal panels were used to avoid gaps between surface panels. The Newton-Raphson iterative procedure was used on the trailing edge to meet the pressure Kutta condition. The velocity distribution was calculated with the Yanagizawa method to eliminate the singularity caused by use of the numerical differential. Comparisons of the performance of podded propulsors with different fins showed that the thrust of propeller in a podded propulsor with fins is greater. The resistance of the pod is also reduced because of the thrust of the fin. The hydrodynamic performance of a podded propulsor with two fins is found to be best, the performance of a podded propulsor with one fin is not as good as two fins, and the performance of the common type is the worst.

转子梢部带圆环并嵌入导管内壁凹槽的泵喷推进器水动力性能研究

针对泵喷推进器梢部流动引起的梢隙空化和梢涡空化问题,本文设计了一种转子梢部带圆环并嵌入导管内壁凹槽的改进型泵喷推进器。基于RANS方程,结合SST k-ω湍流模型,采用分块网格技术,对水下航行体后的泵喷推进器模型进行数值模拟,来分析梢部带圆环并嵌入导管内壁凹槽结构对梢隙空化与梢涡空化的控制效果以及对导管内壁脉动压力和泵喷推进性能的影响。结果显示,梢部带圆环并嵌入导管凹槽结构能明显增大转子梢部的压力以及梢涡涡核压力,减弱梢涡强度,避免梢隙空化的发生和推迟梢涡空化的发生,同时能有效降低导管内壁的脉动压力幅值,降低引起导管结构振动的激励源,并且对推进效率影响较小。该研究结果为泵喷推进器的减振降噪提供了新途径。

来流条件对轴流喷水推进器性能的影响研究

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。

导管对泵喷推进器艇后推进特性的影响

为研究泵喷推进器的艇后推进特性及导管主要参数对推进特性的影响,给出基于推进效率和推进器功率的导管主要参数选择范围,该文通过改进的延迟脱体涡模拟(improved delayed detached eddy simulation,IDDES)方法求解艇后泵喷推进器在不同航速、转速和导管主要参数下的流场,研究了不同航速和不同导管主要参数下的泵喷推进性能和自航因子,其中导管主要参数包括倾角、轴向长度、最大厚度、进口直径和出口直径。结果显示:除导管最大厚度外,导管的倾角、轴向长度、进出口直径对自航因子及推进器功率有较明显影响,倾角和出口直径的变化会显著改变推进器流量,进而影响功率和推进效率。结论表明:选择艇用泵喷推进器导管主要参数时,除了取值要在合理范围,倾角和出口直径还要根据艇体尾段的线型和角度来优化取最佳值。