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。

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。

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.

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.

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.

Endoscopic transluminal pancreatic necrosectomy using a self-expanding metal stent and high-flow water-jet system

Walled-off pancreatic necrosis and a pancreatic abscess are the most severe complications of acute pancreatitis. Surgery in such critically ill patients is often associated with significant morbidity and mortality within the first few weeks after the onset of symptoms. Minimal invasive approaches with high success and low mortality rates are therefore of considerable interest. Endoscopic therapy has the potential to offer safe and effective alternative treatment. We report here on 3 consecutive patients with infected walled-off pancreatic necrosis and 1 patient with a pancreatic abscess who underwent direct endoscopic necrosectomy 19-21 d after the onset of acute pancreatitis. The infected pancreatic necrosis or abscess was punctured transluminally with a cystostome and, after balloon dilatation, a non-covered self-expanding biliary metal stent was placed into the necrotic cavity. Following stent deployment, a nasobiliary pigtail catheter was placed into the cavity to ensure continuous irrigation. After 5-7 d, the metal stent was removed endoscopically and the necrotic cavity was entered with a therapeutic gastroscope. Endoscopic debridement was performed via the simultaneous application of a high-flow water-jet system; using a flush knife, a Dormia basket, and hot biopsy forceps. The transluminal endotherapy was repeated 2-5 times daily during the next 10 d. Supportive care included parenteral antibiotics and jejunal feeding. All patients improved dramatically and with resolution of their septic conditions; 3 patients were completely cured without any further complications or the need for surgery. One patient died from a complication of prolonged ventilation severe bilateral pneumonia, not related to the endoscopic procedure. No procedure related complications were observed. Transluminal endoscopic necrosectomy with temporary application of a self-expanding metal stent and a high-flow water-jet system shows promise for enhancing the potential of this endoscopic approach in patients with walled-off pancreatic necrosis and/or a pancreatic abscess.

Formation Control for Water-Jet USV Based on Bio-Inspired Method

The formation control problem for underactuated unmanned surface vehicles(USVs) is addressed by a distributed strategy based on virtual leader strategy. The control system takes account of disturbance induced by external environment. With the coordinate transformation, the advantage of the proposed scheme is that the control point can be any point of the ship instead of the center of gravity. By introducing bio-inspired model, the formation control problem is addressed with backstepping method. This avoids complicated computation, simplifies the control law,and smoothes the input signals. The system uniform ultimate boundness is proven by Lyapunov stability theory with Young inequality. Simulation results are presented to verify the effectiveness and robust of the proposed controller.

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.

Trans-umbilical endoscopic cholecystectomy with a water-jet hybrid-knife:A pilot animal study

AIM:To investigate the feasibility and safety of Natural orifice trans-umbilical endoscopic cholecystectomy with a water-jet hybrid-knife in a non-survival porcine model.METHODS:Pure natural orifice transluminal endoscopic surgery(NOTES) cholecystectomy was performed on three non-survival pigs,by transumbilical approach,using a water-jet hybrid-knife. Under general anesthesia,the following steps detailed the procedure:(1) incision of the umbilicus followed by the passage of a double-channel flexible endsocope through an overtube into the peritoneal cavity;(2) establishment of pneumoperitoneum;(3) abdominal exploration;(4)endoscopic cholecystectomy:dissection of the gallbladder performed using water jet equipment,ligation of the cystic artery and duct conducted using nylon loops;and(5) necropsy with macroscopic evaluation.RESULTS:Transumbilical endoscopic cholecystectomy was successfully completed in the first and third pig,with minor bleedings. The dissection times were 137and 42 min,respectively. The total operation times were 167 and 69 min,respectively. And the lengths of resected specimen were 6.5 and 6.1 cm,respectively.Instillation of the fluid into the gallbladder bed produced edematous,distended tissue making separation safe and easy. Reliable ligation using double nylon loops insured the safety of cutting between the loops.There were no intraoperative complications or hemodynamic instability. Uncontrolled introperative bleeding occurred in the second case,leading to the operation failure.CONCLUSION:Pure NOTES trans-umbilical cholecystectomy with a water-jet hybrid-knife appears to be feasible and safe. Further investigation of this technique with long-term follow-up in animals is needed to confirm the preliminary observation.

Water-Jet Cavitation Shock Bulging as Novel Microforming Technique

With the continuous expansion of the application range of microelectromechanical systems,microdevice forming technology has achieved remarkable results.However,it is challenging to develop new microforming processes that are low cost,environmentally friendly,and highly flexible;the high-energy shock wave in a cavitation bubble's collapse process is used as the loading force.Herein,a new process for the microbulging of the water-jet cavitation is proposed.A series of experiments involving the water-jet cavitation shock microbulging process for TA2 titanium foil is performed on an experimental system.The microforming feasibility of the water-jet cavitation is investigated by characterizing the shape of the formed part.Subsequently,the effects of the main parameters of the water-jet cavitation on the bulging profile,forming depth,surface roughness,and bulging thickness distribution of TA2 titanium foil are revealed.The results show that the plastic deformation increases nonlinearly with the incident pressure.When the incident pressure is 20 MPa,the maximum deformation exceeds 240 pm,and the thickness thinning ratio changes within 10%.The microbulging feasibility of water-jet cavitation is verified by this phenomenon.

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

不稳定的表演在开的水里拖并且加倍反向的推进器 podded propulsors 数字地用计算液体动力学(CFD ) 被模仿方法。一个动人的网孔方法习惯于更写实地模仿 propulsor 工作条件，和戳，转矩，和两 propulsors 的侧面的力量系数被比较并且分析。在不同进展系数与稳定、不稳定的结果的流动地分发一起对 propulsors 的不同部分起作用的力量被比较。而且，侧面的力量的变化和之间的差别上述二个方法主要被分析。两个方法的戳和转矩结果是类似的，这被显示出。

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

试验性的测试被进行评估 L 类型 podded propulsor 的水动力学性能在直向前，用一台开水的测量仪器的运动和离开设计条件为 podded propulsors 由作者发展了，拖引坦克的一个轮船模型，并且在水粒子图象 velocimetry (PIV ) 下面测量系统。在条件的三种类型下面， L 类型 podded propulsor 的主要参数被测量，包括推进器戳和转矩，以及整个豆荚单位的戳，方面力量，和时刻。另外，在推进器和神气之间的节上的流动领域被分析。试验性的结果证明动态 azimuthing 率和方向和转弯的方向在推进器和整个豆荚单位上影响力量。因为推进器旋转的效果，力量不均匀地在左、正确的 azimuthing 方向之间被散布。这研究的调查结果为关于 L 类型 podded propulsors 的进一步的研究提供一个基础。

Influence of long and short guide vanes on hydraulic performance of water-jet pump

Different guide vane structures will affect the flow inside the pump,and then affect the transformation of the pressure energy and kinetic energy,and change the velocity distribution of the pump outlet.In order to study the influence of long and short guide vanes on the water-jet pump,on the basis of conventional design,eight schemes of guide vane with different vertical heights were designed in the method of computational fluid dynamics for numerical calculation,the performance curve of water-jet pumps with different long and short guide vanes was obtained,and finally the influence of different guide vanes on hydraulic performance and internal flow was analyzed.The results show that all of schemes reducing the height of blade can improve the head and efficiency.In the schemes reducing the height on the shroud,the guide vanes that the height of the blade is equal to the height difference between hub and shroud in impeller have the highest head and efficiency.In all schemes decreasing the blade height,with the increase of the height difference,the velocity increases gradually and the distribution of turbulence kinetic energy becomes more reasonable in the guide vane outlet.The schemes reducing the height on the hub have more reasonable distribution of velocity and turbulence kinetic energy according to schemes reducing the height on the shroud.The guide vanes of long and short blades can be used to stagger the position of the diffusion flow generated by adjacent blades,which can reduce the effect of the velocity circulation and make the flow of the outlet position more stable.

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。

Prediction and Analysis of Surface Quality of Northeast China Ash Wood during Water-Jet Assisted CO_(2) Laser Cutting

As a natural and environmentally friendly renewable material,Northeast China ash wood(NCAW)(Fraxinus mandshurica Rupr.)was cut by water-jet assisted CO_(2) laser(WACL),the surface quality was evaluated by surface roughness of cut section.The surface roughness was measured by three-dimensional(3D)profilometry.Furthermore,the micromorphology of machined surface was observed by scanning electronic microscopy(SEM).Carbon content changes of machined surface were measured by energy dispersive spectrometer(EDS).A relationship between surface roughness and cutting parameters was established using response surface methodology(RSM).It is concluded that the cutting speed,laser power and water pressure played an important role in surface roughness of cut section.The surface roughness increased as an increase in laser power.It decreased caused by increasing of cutting speed and water pressure.Measurements revealed that the surface quality of NCAW part was improved using the optimized combination of cutting parameters.The established quadratic mathematical model of a good prediction is helpful for matching suitable cutting parameters to obtain expected surface quality.

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。

The kinematic Design of Beating-up Mechanism for Water-jet Loom Series Modified from Air-jet Loom

For Toyoda looms with air-jet weft insertion,the beat-ing-up mechanisms together with those of Tsudakomawater-jet looms are analyzed.Then by changing thecrank length of the four-bar-linkage for the air-jetlooms to get four specifications of reed travel correspond-ing to the series of Tsudakoma water-jet looms,it canbe proved by comparisons of displacements,velocities,accelerations and transmission pressure angles that thosetwo series of mechanisms have very similar kinematicproperties.So the possibility of developing a series of wa-ter-jet looms modified from Toyoda air-jet looms isproved.It is beneficial to save the machine cost andbroaden the machine types.

泵喷推进器间隙流动控制技术试验研究

[目的]旨在抑制转子叶梢间隙流动,解决其给泵喷推进器水动力性能和非定常激振力带来的问题。[方法]以某型前置定子式泵喷推进器为对象,采用环状柔性密封结构与转子端环配合的方法,研究其抑制转子叶梢的间隙流动的有效性。通过保持导管结构近似刚性固定,测得推进器转子的推力和扭矩,给出转子的敞水效率,在高功率频闪仪的辅助下,观察记录各设计工况下的空化初生点,计算绘制出推进器的空化初生特性曲线。针对有/无间隙的推进器模型,在空化/非空化状态下通过试验测得转子轴的振动加速度,以此评估间隙消除对轴系振动的影响。[结果]结果显示:带有柔性密封结构的泵喷推进器,其转子的推力和扭矩显著提升,也使得转子敞水效率在中低进速系数下得到显著提升,且在设计点附近基本保持不变,在较高进速系数下略有下降;在设计点附近一段很宽的进速系数(0.85<J<1.40)下,无间隙泵喷推进器的空化性能更优;与有间隙泵喷推进器相比,装有无间隙泵喷推进器的轴系,其轴向振动加速度幅值在大多数特征频率处都显著降低。[结论]研究结果表明,采用柔性密封结构来抑制叶顶间隙流动,对于提高中低进速系数下的转子敞水效率、优化设计点处的空化性能以及抑制推进器的轴系振动等具有积极作用。