共查询到20条相似文献，搜索用时 31 毫秒
1.
The propulsive efficiency maximization of contra-rotating azimuth propulsor (CRAP) at model scale is investigated through searching the optimal matching rotational speeds of the forward propeller (FP) and rear propeller (RP) of CRAP based on the potential-based panel method. The hydrodynamic performance of CRAP with changing rotational speeds (FP and RP may have different rotational speeds) are calculated. When the inflow velocity is certain, the cubic spline interpolation method is used to get the equal thrust points at which CRAP has the same thrust with the corresponding conventional propeller (CP). Then, the delivered powers at these equal thrust points are further obtained through cubic spline interpolation method. The rotational speeds of FP and RP at the equal thrust point corresponding to the minimal delivered power are the optimal matching rotational speeds of CRAP. The optimal matching calculations are carried out at different inflow velocities. The results of the optimal matching investigation show that CRAP has the lowest delivered powers when FP and RP have the optimal matching rotational speeds and that the energy saving level decreases with the increase of inflow velocity. The optimal matching rotational speed ratio decreases with the increase of inflow velocity. In general, the delivered powers of CRAP having optimal matching rotational speeds at different inflow velocities are obviously smaller than those of CP. 相似文献
2.
The scale effect of hydrodynamic performance of the hybrid CRP pod propulsion system was investigated numerically using the RANS method combined with SST k − ω turbulence model and moving mesh method. The pod resistance influence factor was introduced to represent the effect of wake field of CRP on the pod resistance. Results showed the pod resistance influence factor to be a function of the Reynolds number and revolution ratio. Representative function expression can be obtained by regression analysis using multiplication of multinomial polynomials and linear function. The standard ITTC 1978 extrapolation procedure can be utilized to predict hydrodynamic performance of forward propeller because of the slightness of the influence of the pod unit on the forward propeller. The thrust and torque coefficient influence factors of aft propeller were introduced, and they were found to represent the effect of wake field of forward propeller and blockage effect of the pod on the hydrodynamic performance of aft propeller. It shows that thrust and torque coefficient influence factors are independent of the Reynolds number and have a linear relationship with the revolution ratio. On this basis, a method of estimating the hydrodynamic performance was proposed for full scale propulsion system. 相似文献
3.
A computational method has been developed to predict the hydrodynamic performance of the propeller–rudder systems (PRS) and azimuthing podded drive (AZIPOD) systems. The method employs a vortex-based lifting theory for the propeller and the potential surface panel method for the steering system. Three propeller models along with three steering systems (rudder and strut, flap and pod (SFP)) are implemented in the present calculations for the cases of uniform and non-uniform conditions. Computed velocity components show good agreement with the experimental measurements behind a propeller with or without the rudder. Calculated thrust, torque and lift also agree well with the experimental results. Computations are also performed for an AZIPOD system in order to obtain the pressure distributions on the SFP, and the hydrodynamic performance (thrust, torque and lift coefficients). The present method is useful for examining the performance of the PRS and AZIPOD systems in the hope of estimating the propulsion and the maneuverability characteristics of the marine vehicles more accurately. 相似文献
4.
The hydrodynamic performance of a hybrid CRP pod propulsion system was studied by RANS method with SST turbulence model and sliding mesh. The effect of axial spacing on the hydrodynamic performance of the hybrid CRP pod propulsion system was investigated numerically and experimentally. It shows that RANS with the sliding mesh method and SST turbulence model predicts accurately the hydrodynamic performance of the hybrid CRP pod propulsion system. The axial spacing has little influence on the hydrodynamic performance of the forward propeller, but great influence on that of the pod unit. Thrust coefficient of the pod unit declines with the increase of the axial spacing, but the trend becomes weaker, and the decreasing amplitude at the lower advance coefficient is larger than that at the higher advance coefficient. The thrust coefficient and open water efficiency of the hybrid CRP pod propulsion system decrease with the increase of the axial spacing, while the torque coefficient keeps almost constant. On this basis, the design principle of axial spacing of the hybrid CRP pod propulsion system was proposed. 相似文献
5.
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
6.
The hydrodynamic characteristics of a marine propeller operating in oblique inflow are investigated by using CFD method. Two propellers with different geometries are selected as the study subjects. RANS simulation is carried out for the propellers working at a wide range of advance coefficients and incidence angles. The effects of axial inflow and lateral inflow are demonstrated with the hydrodynamic force on the propeller under different working conditions. Based on the obtained flow field details, the hydrodynamic mechanism of propeller operating in oblique inflow is analyzed further. The trailing vortex wake of propeller is highly affected by the lateral inflow, resulting in the deflected development path and the circumferentially non-uniform structure, as well as the enhanced axial velocity in slipstream. Different flow patterns are observed on the propeller blade with the variation of circumferential position. Combined with the computed hydrodynamic forces and pressure distribution on propeller, the mechanism resulting in the increase of propulsive loads and the generation of propeller side force is explored. Finally, a systematic analysis is carried out for the propulsive loads and propeller side force as a function of axial and lateral advance coefficients. The major terms that play a dominant role in the modeling of propulsive loads and propeller side force are determined through the sensitivity analysis. This study provides a deeper insight into the hydrodynamic characteristics of propeller operating in oblique inflow, which is useful to the investigation of propeller performance during ship maneuvers. 相似文献
7.
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
8.
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
9.
螺旋桨工作时在其周围形成诱导速度场,诱导速度随到桨叶距离的增大而衰减。采用CFD方法模拟螺旋桨敞水性能时,只能截取有限尺度的流域进行计算,此时计算域边界上诱导速度并不为零,将进口速度设为进速是近似的。一般采用足够大的计算域,使螺旋桨前方及侧面边界尽量远离桨叶。为了在较小的计算域中实现螺旋桨敞水性能的准确预报,提出在设定进口速度时计入螺旋桨诱导速度的CFD模拟方法。应用升力面方法计算诱导速度,将进口速度设为进速与诱导速度之和。逐步减小计算域尺度,考察敞水性能及压力分布计算结果的变化情况及精度。算例比较表明:通过考虑诱导速度,可以大幅度减小进口与螺旋桨的距离而不降低计算精度。 相似文献
10.
This paper provides an overview of a bioinspired delay stall propulsor (BDSP) concept that employs delayed stall unsteady lift enhancement to increase the lift on propeller blades without adding any complexity to the propulsor. This BDSP concept can provide greatly increased propeller thrust for a given propeller diameter, leading to both increased speed and/or maneuverability. Alternately, this technology offers reduced radiated noise while maintaining current thrust levels through reduction in both propulsor rotation speed and acoustic cancellation. Preliminary two-dimensional simulations have shown a potential 36% reduction in rotational speed at constant thrust, leading to an estimated 4-dB reduction in the total radiated acoustic power. It is believed that the BDSP concept will be simple to manufacture, rugged, and easy to retrofit into existing marine propulsors. This technology has direct application to torpedoes, unmanned underwater vehicles, maneuvering thrusters, submarines, and other propeller-driven devices. 相似文献
11.
Surface-Piercing Propellers (SPPs) are the preferred propulsion system for light to moderately loaded high-speed applications due to the high fuel efficiency. For highly loaded applications, the efficiency of SPPs tends to decrease because of the limited submerged blade area and the presence of large suction side cavities. Moreover, it is a challenge to design large-scale SPPs that can maintain reliable fatigue strength and avoid vibration issues while maximizing the propeller thrust for a given power input. In this work, three SPP designs are presented for different size Surface Effect Ships (SESs) that can attain a maximum advance speed of 25.72 m/s (50 knots). A previously developed and validated three-dimensional (3-D) coupled boundary element method-finite element method (BEM-FEM) is used for the transient hydroelastic analysis of SPPs. The method is validated by comparing the predicted hydrodynamic performance with those obtained using a vortex-lattice method (VLM) and a Reynolds Averaged Navier-Stokes (RANS) solver. The hydrodynamic and structural dynamic performance of the SPPs are presented. Finally, challenges associated with the design related analyzes of large-scale SPPs are discussed. 相似文献
12.
可回转桨的水动力模型与操纵性能 总被引：1，自引：0，他引：1
可回转桨在船后形成复杂的流场,难以建立准确的数学模型,因此对其推力进行理论计算十分困难。本文根据实验数据,用神经网络辨识方法建立了船后可回转桨的水动力模型,并在此基础上研究了可回转桨的操纵性能。仿真结果表明：用神经网络系统辨识方法所建立的数学模型能够真实地反映可回转浆的推力特性。本文为研究复杂的水动力问题提供了一种行之有效的方法。 相似文献
13.
A numerical method is proposed to predict the effective wake profiles of high speed underwater vehicles propelled by contra-rotating propellers (CRPs), in which the hydrodynamic effects of the CRPs are simulated by distributed body forces. First, Reynolds-averaged Navier-Stokes (RANS) simulations are conducted for identical body-force distributions in open-water and self-propulsion conditions. The effective wake profiles at the CRP disks are then obtained by subtracting the velocities induced by the body forces in the open water from those induced by the body forces in the self-propulsion condition. The effective wake profiles were then predicted for a generic underwater vehicle with an established CRP design. Next, the hydrodynamic performance of the CRPs in the effective wake was computed using an in-house vortex-lattice code. The potential-flow results agree well with those provided by the RANS simulation under the self-propulsion condition, indicating that the proposed method can predict the effective wake profiles for CRPs with reasonable accuracy. The influences of different wake components on the blade forces were investigated, determining that for CRPs, and especially for the aft propeller, the circumferential wake cannot be neglected in the design. 相似文献
14.
An integral panel method (IPM) that treats the different components of multi-component propulsors as a whole is presented for efficient propulsor performance analysis. The IPM requires consider only one blade of the propeller in the performance analysis, which significantly reduces the number of computation grid. The control equations of the IPM are derived in detail for podded propulsors, contra-rotating propellers and hybrid contra-rotating shaft pod propulsors, and based on these derivations, a general control equation for multi-component propulsors with propeller is derived. Comparison between numerical results and experimental data show that the IPM provides good accuracy for the performance analysis of multi-component propulsors with propeller. In addition, the error sources of IPM are discussed, and the reasonableness of these errors is evaluated. 相似文献
15.
Numerical simulation and experimental research on hydrodynamic performance of propeller with varying shaft depths 总被引：2，自引：0，他引：2
In order to study hydrodynamic performance of a propeller in the free surface, the numerical simulation and open-water experiments are carried out with varying shaft depths of propeller. The influences of shaft depths of a propeller on thrust and torque coefficient in calm water are mainly studied. Meanwhile, this paper also studies the propeller air-ingestion under special working conditions by experiment and theoretical calculation method, and compares the calculation results and experimental results. The results prove that the theoretical calculation model used in this paper can imitate the propeller air-ingestion successfully. The successful phenomenon simulation provides an essential theoretical basis to understand the physical essence of the propeller air-ingestion. 相似文献
16.
The existing propulsor that can perform both propulsion and maneuvering along axis of rotation is propeller/rotor for a helicopter. Helicopter propellers when maneuvering increase or decrease their blades’ pitch cyclically to create imbalanced thrust and hence maneuvering force/torque. A “maneuverable propeller” was developed and its performance on both maneuvering and propulsion is assessed. The “maneuverable propeller” is an alternative of the existing helicopter rotors. The novelty of this propulsor is that the imbalanced thrust force/torque is created by cyclically increasing or decreasing the angular speed of their blades relatively to the hubs/shafts, to provide the desired maneuvering torque. This maneuverable propeller is hence defined as the Cyclic Blade Variable Rotational Speed Propeller (CBVRP). One of the best advantages is that the maneuvering torque created by the “maneuverable propeller” is much higher, about 5 times of the shaft torque of the same propeller at thrust only mode. The “maneuverable propeller” has wide applications for both surface ships and underwater vehicles that require high maneuverability for cruising inside the narrow passage. 相似文献
17.
Surface Piercing Propellers (SPPs) are a particular kind of propellers which are partially submerged operating at the interface of air and water. They are more efficient than submerged propellers for the propulsion system of high-speed crafts because of larger propeller diameter, replacing cavitation with ventilation, decreasing the torque and higher efficiency. This study presents a reliable numerical simulation to predict SPP performance using Unsteady Reynolds-Averaged Navier–Stokes (URANS) method. A numerical study on 841-B SPP is performed in open water condition. The free surface is modeled by Volume of Fluid (VOF) approach and the sliding mesh technique is implemented to model the propeller rotational motion. The sliding mesh allows capturing the process of water entry and water exit of blades. The propeller hydrodynamic characteristics, the ventilation pattern and the time history of blade loads are validated through the comparison with available experimental data. For the studied case, it was found that the common grid independence study approach is not sufficient. The grid should be elaborately generated fine enough based on the flow pattern and turbulence modeling parameters in regions near the blade's tip, trailing and leading edges and over the suction side. Details of URANS simulations including optimal time-step size based on propeller revolution rate and the required number of propeller revolutions for periodical results are presented and discussed. 相似文献
18.
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. 相似文献
19.
The paper presents the effects of blade twist and nacelle shape on the performance of horizontal axis tidal current turbines using both analytical and numerical methods. Firstly, in the hydrodynamic design procedure, the optimal profiles of untwisted and twisted blades and their predicted theoretical turbine performance are obtained using the genetic algorithm method. Although both blade profiles produce desired rated rotational speed, the twisted blade achieves higher power and thrust performance. Secondly, numerical simulation is performed using sliding mesh technique to mimic rotating turbine in ANSYS FLUENT to validate the analytical results. The Reynolds-Averaged Navier-Stokes (RANS) approximation of the turbulence parameters is applied to obtain the flow field around the turbine. It is found that power and axial thrust force from BEMT (Blade Element Momentum Theory) method are under-predicted by 2% and 8% respectively, compared with numerical results. Afterwards, the downstream wake field of the turbine is investigated with two different nacelle shapes. It is found that the rotor performance is not significantly affected by the different nacelle shapes. However, the structural turbulence caused by the conventional nacelle is stronger than that by the NACA-profiled shape, and the former can cause detrimental effect on the performance of the downstream turbines in tidal farms. 相似文献
20.
Under real sea conditions, the hydrodynamic performance of floating vertical-axis tidal current turbines is affected by waves and currents. The wave circular frequency is a significant factor in determining the frequencies of the wave-induced motion responses of turbines. In this study, the ANSYS-CFX software (manufacturer: ANSYS Inc., Pittsburgh, Pennsylvania, United States) is used to analyse the hydrodynamic performance of a vertical-axis turbine for different yawing frequencies and to study how the yawing frequencies affect the main hydrodynamic coefficients of the turbine, including the power coefficient, thrust coefficient, lateral force coefficient, and yawing moment coefficient. The time-varying curves obtained from the CFX software are fitted using the least-squares method; the damping and added mass coefficients are then calculated to analyse the influence of different yawing frequencies. The simulation results demonstrate that when analysing non-yawing turbines rotating under constant inflow, the main hydrodynamic coefficient time-varying curves of yawing turbines exhibit an additional fluctuation. Furthermore, the amplitude is positively correlated with the yawing frequency, and the oscillation amplitudes also increase with increasing yawing frequency; however, the average values of the hydrodynamic coefficients (except the power coefficient) are only weakly influenced by yawing motion. The power coefficient under yawing motion is lower than that under non-yawing motion, which means that yawing motion will cause the annual energy production of a turbine to decrease. The fitting results show that the damping term and the added mass term exert effects of the same level on the loads and moments of vertical-axis turbines under yawing motion. The results of this study can facilitate the study of the motion response of floating vertical-axis tidal current turbine systems in waves. 相似文献