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With a large number of recreational craft there is an interest in the development of efficient, high thrust outboard propellers. There has been some success with ‘cupped' propellers with a bent trailing edge. Along the same lines is a simpler idea of attaching a raised bar called an ‘Interceptor' or ‘Spoiler' on the propeller blade trailing edge. For the small diameter propeller, this simplifies the design to adjusting the height of the bar. This paper presents a three-part design study which examines the range of available outboard propellers, the optimum size of outboard propellers, and the capability of predicting the influence of the spoiler on the outboard propeller performance. The results indicate the feasibility of the outboard propeller with spoiler. 相似文献
3.
H. Schwanecke 《Ocean Engineering》1982,9(3):271-280
The thrust produced by a marine propeller operating in a spatially non-homogeneous flow is reduced by inhomogenities depending on the angular co-ordinate. The loss of efficiency caused by this reduction of thrust is to a certain extent compensated by increasing the design thrust, a procedure called “unsteady wake adaption”. Numerical calculations show improvements of propeller efficiency which are dependent on the degree of inhomogenity of the flow fielf. 相似文献
4.
A two-frame particle image velocimetry (PIV) technique is used to investigate the wake characteristics behind a marine propeller with 4 blades at high Reynolds number. For each of 9 different blade phases from 0° to 80°, 150 instantaneous velocity fields are measured. They are ensemble averaged to study the spatial evolution of the propeller wake in the region ranging from the trailing edge to one propeller diameter (D) downstream location. The phase-averaged mean velocity shows that the trailing vorticity is related to radial velocity jump, and the viscous wake is affected by boundary layers developed on the blade surfaces and centrifugal force. Both Galilean decomposition method and vortex identification method using swirling strength calculation are very useful for the study of vortex behaviors in the propeller wake region. The slipstream contraction occurs in the near-wake region up to about X/D=0.53 downstream. Thereafter, unstable oscillation occurs because of the reduction of interaction between the tip vortex and the wake sheet behind the maximum contraction point. 相似文献
5.
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. 相似文献
6.
Marine cycloidal propulsion system is efficient in maneuvering ships like tugs, ferries, etc. It is capable of vectoring thrust in all direction in a horizontal plane. When used in pair, the system enables a vessel to perform maneuvers like moving sideways, perform rotation about a point, i.e. turning diameter of its own length, etc. In this system, the propeller blades have to change their angle of attack at different angular position of the disc. Due to this reason, the inflow velocity vector to propeller blades changes continuously. The propeller blade oscillates about a vertical axis passing through its body and at the same time rotates about a point. Superposed on these motions is the dynamics of the ship on which the propulsion system is installed. This results in a formidable and challenging hydrodynamics problem. Each of the propeller blade sections could be considered as an aerofoil operating in combined heave and pitch oscillation mode. Due to the constantly varying inflow velocity, the hydrodynamic flow is unsteady. The unsteady hydrodynamic flow is simulated by incorporating the effect of shed vortices at different time instant behind the trailing edge. Due to the kinematics of the problem, the blade is subjected to higher structural deformation and vibration load. The structural deformation and vibration when coupled with the hydrodynamic loading add another level of complexity to the problem. In this paper, the variation of hydrodynamic load on the propeller blade due to steady and unsteady flow is compared. We also model the structural dynamics of the blade and study its effect on the hydrodynamic loading. Finally, we couple the structural dynamics with hydrodynamics loading and study its influence on the propeller blade for different operating regimes. 相似文献
7.
Traditionally, propeller design has been focused on all activities necessary to obtain a propeller featuring a high efficiency, avoiding erosive cavitation for given operating conditions and having adequate structural strength. In recent years, more and more challenging requirements have been imposed, such as the reduction of radiated noise and pressures pulses, requiring more precise analyses and methods in the optimization of the propeller performance. On the other hand, the evaluation of the propeller strength still relies on simplified methods, which basically consider the blade as a cantilever beam subjected to characteristic static forces. Since the loads acting on a blade are variable in the blade revolution and in different operating conditions throughout the ship life, a procedure to account for the influence of fatigue phenomena is proposed. The fatigue assessment could reduce the safety factor in the propeller scantling rules and allow improving the quality of propeller design (e.g. obtaining higher efficiency, margin on cavitation phenomena, less noise). 相似文献
8.
Anders Smrup Olsen 《Ocean Engineering》2004,31(3-4):401-416
The efficiency for a propeller is calculated by energy coefficients. These coefficients are related to four types of losses, i.e. the axial, the rotational, the frictional, and the finite blade number loss, and one gain, i.e. the axial gain. The energy coefficients are derived by use of the potential theory with the propeller modelled as an actuator disk. The efficiency based on the energy coefficients is calculated for a propeller series. The results show a good agreement between the efficiency based on the energy coefficients and the efficiency obtained by a vortex-lattice method. 相似文献
9.
The blade frequency noise of non-cavitation propeller in a uniform flow is analyzed in time domain. The unsteady loading (dipole source) on the blade surface is calculated by a potential-based surface panel method. Then the time- dependent pressure data is used as the input for Ffowcs Williams-Hawkings formulation to predict the acoustics pressure. The integration of noise source is performed over the true blade surface rather than the nothickness blade surface, and the effect of hub can be considered. The noise characteristics of the non-cavitation propeller and the numerical discretization forms are discussed. 相似文献
10.
In this study, non-cavitating and cavitating flow around the benchmark DTMB 4119 model propeller are solved using both viscous and potential based solvers. Cavitating and non-cavitating propeller radiated noises are then predicted by using a hybrid method in which RANS(Reynolds-averaged Navier-Stokes) and FWH(Ffowcs Williams Hawkings) equations are solved together in open water conditions. Sheet cavitation on the propeller blades is modelled by using a VOF(Volume of Fiuld) method equipped with Schnerr-Sauer cavitation model.Nevertheless, tip vortex cavitation noise is estimated by using two different semi-empirical techniques, namely Tip Vortex Index(TVI, based on potential flow theory) and Tip Vortex Contribution(TVC). As the reference distance between noise source and receiver is not defined in open water case for TVI technique, one of the outputs of this study is to propose a reference distance for TVI technique by coupling two semi-empirical techniques and ITTC distance normalization. At the defined distance, the starting point of the tip vortex cavitation is determined for different advance ratios and cavitation numbers using potential flow solver. Also, it is examined that whether the hybrid method and potential flow solver give the same noise results at the inception point of tip vortex cavitation.Results show that TVI method based on potential flow theory is reliable and can practically be used to replace the hybrid method(RANS with FWH approach) when tip vortex cavitation starts. 相似文献
11.
Unsteady forces, torques and bending moments were predicted for a model podded propulsor unit at various azimuth angles. Predictions in time history include propeller shaft thrust, propulsor unit thrust, normal forces to the propeller shaft bearing, total forces acting on the propulsor unit, propeller shaft torque, blade spindle torque, in-plane and out-of-plane bending moments, and propulsor unit stock shaft torque and bending moments. Analysis was performed for averaged forces and their fluctuations as well. A time-domain unsteady multi-body panel method code, PROPELLA, was further developed for this prediction work. Predictions were compared with a set of time averaged in-house experimental data for a puller-type podded propulsor configuration in the first quadrant operation. Unsteady fluctuations of forces were predicted numerically. Analysis was made for the bending moment on propeller blades, shaft and the propulsor unit stock shaft for azimuth angles from 0° to 45°. It indicates that the magnitude and fluctuation of the forces are significant and they are essential for structural strength and design optimization. The predicted bending moment and global forces on the propulsor unit provide some useful data for ship maneuvering motion and simulation in off-design conditions. 相似文献
12.
The purpose of this paper is to optimise the hydroelastic performance of a composite marine propeller to reduce vibration and dynamic stress. A hydroelasticity method based on the finite element method (FEM) coupled with computational fluid dynamics (CFD) is used to simulate the composite marine propeller in a non-uniform wake. Composite blades can be considered as a cantilever-like laminated structure experiencing an unsteady hydrodynamic load and centrifugal force. The objective of the improved design is to minimise the vibratory hub loads. The ply angle and stacking sequence are considered as the design variables. The nonlinear periodic transient responses and vibration hub loads of the composite blade are obtained by solving coupled equations using the Newton–Raphson numerical procedure. Compared to the starting design of the propeller, the optimum solution results in a 49.6–70.6% reduction of the 7/rev hub loads. 相似文献
13.
水平轴海流能发电机叶片设计与性能分析 总被引：2，自引：1，他引：1
全球海洋蕴藏着丰富的海流能,合理利用海流能可以有效缓解能源危机。以额定工况下获能系数达到最大值为目标,利用叶素-动量理论设计了150 kW水平轴海流能发电机的叶片。使用叶素-动量理论结合普朗特修正和葛劳渥修正的方法,预测了海流机在不同尖速比以及不同桨距角下的水动力性能,分析了攻角和载荷沿着叶片径向的分布规律。使用CFD方法计算了海流机在不同尖速比下的水动力性能,并与理论方法的计算结果进行了比较。理论方法和CFD方法的结果均表明,所设计的海流机最大获能系数位于设计尖速比处,证明基于叶素-动量理论的水平轴海流机叶片设计方法是有效的。 相似文献
14.
导管桨的尾流不稳定性在其性能评价中非常重要,不但是其能否提供稳定推力的保证,而且也与螺旋桨的尾流噪声直接相关。为了改善导管桨的尾流,提高尾流稳定性,并优化导管桨的流场脉动,根据座头鲸鳍肢前缘结节的仿生原理,对导管桨叶片的导边进行改进,提出了两种仿生桨型,采用IDDES湍流模型对低进速系数下常规导管桨和仿生叶片导管桨进行数值模拟,探究叶片构型对导管桨性能和尾流不稳定性的影响。计算结果表明,前缘结节可以有效降低叶片受力波动的幅值和叶片所受合力的主频域峰值,具有较大结节的叶片对导管桨尾流有明显的优化作用,在尾流远场中扩大了流动稳定区,延后了尾流处涡破碎的发生,改善了能量谱密度的频域分布。进一步,大前缘结节叶片导管桨应用在低速工况下时,可以大量减少尾流泄涡区域的二次涡产生,这是由于前缘结节提升了相邻涡互感的强度,使得尾流更加稳定,而小结节叶片仿生桨型对导管桨尾流则无明显优化作用。研究方法和成果可为螺旋桨尤其是导管桨尾流不稳定性研究提供参考,不仅验证了前缘结节在导管桨叶片应用的合理性,而且揭示了其优化尾流稳定性的机理。 相似文献
15.
《中国海洋工程》2021,(3)
Three blade-geometry optimization models derived along with assumptions from the blade element momentum(BEM) approach are studied by using a steady BEM code to improve a small horizontal-axis rotor of three blades that has been previously used in experiments. The base rotor blade has linear-radially varying chord length and pitch angle, while the other three models noted as Burton, Implicit and Hansen due to their references and characteristics yield blades of non-linearly varying chord length and pitch angle. The aim is to compare these rapid models and study how assumptions embedded in them affect performance and induction factors. It is found that the model that has the least assumptions(Hansen) and which considers the blade-profile drag in its optimization procedure yields the highest power coefficient, C_P, at the optimal tip speed ratio(TSR), about 7% higher than the base one and also higher C_P at high TSR. It produces an axial induction factor distribution along the blade that is closest to the 1 D optimal value of 1/3. All optimized tangential induction-factor distributions along the blade closely vary as inverse to the square of the radial distance, while being mildly higher than the base distribution. It shows that sufficient swirl is necessary to increase power but at a level causing not too much energy loss in unnecessary swirl of the wake. At high TSR, all optimized rotors adversely produce higher thrust than the base one, but the one with most embedded assumptions(Burton) produces the highest thrust. Details of all three optimization models are given along with the distributions of the power, thrust, blade hydrodynamic efficiency and induction factors. 相似文献
16.
基于重叠网格模型,通过非定常RANS数值模拟与结果分析,研究了块状冰的尺寸、轴向运动和冰桨位置对螺旋桨水动力性能的影响。选用切割体网格绘制整体静止计算域的背景网格,之后结合棱柱层网格绘制螺旋桨子计算域和冰块子计算域的重叠网格,不同的计算域之间通过两者的重叠区域进行数据传递和插值。计算结果显示,当冰块固定在桨前时,螺旋桨产生的非定常推力和扭矩均以叶频为基频进行周期性变化,而且两者的时间平均值和振幅主要受冰块在螺旋桨盘面内的轴向投影面积、冰桨轴向位置和冰桨水平位置的影响;当冰块在桨前沿轴向匀速靠近螺旋桨时,冰桨轴向距离逐渐变小,冰桨周向相对位置发生周期性的变化,使得推力和扭矩两者均以叶频振荡,而且两者的时间平均值和振幅均随着冰桨轴向距离减小而增加。 相似文献
17.
The blade frequency noise of non-cavitation propeller in a uniform flow is analyzed in time domain. The unsteady loading (dipole source) on the blade surface is calculated by a potential-based surface panel method. Then the time- dependent pressure data is used as the input for Ffowcs Williams-Hawkings formulation to predict the acoustics pressure. The integration of noise source is performed over the true blade surface rather than the nothickness blade surface, and the effect of hub can be considered. The ... 相似文献
18.
In this study, the flow around the pod unit is analysed and the performance characteristics of the propeller on the pod are investigated. The main objective of the present work is to further improve the original numerical method developed before for the prediction of performance of podded propellers and to further validate the earlier developed numerical model with a specific emphasis on the hydrodynamic interaction amongst the propulsor components. While in the earlier numerical method, the axial induced velocities by pod and strut parts were included into the calculations on the propeller disc plane, in the present method the tangential induced velocities on the propeller disc plane are included in the calculations as well. The flow domain around the podded propeller is mainly divided into three parts; the axisymmetric pod part, the strut part and the propeller part. While the pod and strut parts are modelled by a low-order boundary element method (BEM), the propeller is represented by a vortex lattice method (VLM). Coupling of the BEM and the VLM is carried out in an iterative manner to incorporate the effect of the pod on the propeller, and vice versa. The present numerical method is applied to two different podded propellers with zero yaw angles in order to compare the results with those of experimental measurements. The present numerical method is also validated in the case of 15° of yaw angle for a podded propulsor. The effect of pod and strut on the propeller and vice versa are discussed. 相似文献
19.
The use of an unsteady computational fluid dynamic analysis of the manoeuvring performance of a self-propelled ship requires a large computational resource that restricts its use as part of a ship design process. A method is presented that significantly reduces computational cost by coupling a blade element momentum theory (BEMT) propeller model with the solution of the Reynolds averaged Navier Stokes (RANS) equations. The approach allows the determination of manoeuvring coefficients for a self-propelled ship travelling straight ahead, at a drift angle and for differing rudder angles. The swept volume of the propeller is divided into discrete annuli for which the axial and tangential momentum changes of the fluid passing through the propeller are balanced with the blade element performance of each propeller section. Such an approach allows the interaction effects between hull, propeller and rudder to be captured. Results are presented for the fully appended model scale self-propelled KRISO very large crude carrier 2 (KVLCC2) hull form undergoing static rudder and static drift tests at a Reynolds number of 4.6×106 acting at the ship self-propulsion point. All computations were carried out on a typical workstation using a hybrid finite volume mesh size of 2.1×106 elements. The computational uncertainty is typically 2–3% for side force and yaw moment. 相似文献
20.
A fully automated optimization process is provided for the design of ducted propellers under open water conditions, including 3D geometry modeling, meshing, optimization algorithm and CFD analysis techniques. The developed process allows the direct integration of a RANSE solver in the design stage. A practical ducted propeller design case study is carried out for validation. Numerical simulations and open water tests are fulfilled and proved that the optimum ducted propeller improves hydrodynamic performance as predicted. 相似文献