拍动翼海流能采集系统水动力学性能研究

发布时间：2017-12-27 04:13

本文关键词：拍动翼海流能采集系统水动力学性能研究　出处：《浙江大学》2017年博士论文　论文类型：学位论文

【摘要】：海洋中蕴藏着巨大能量的可再生清洁能源,包括海流能、波浪能、风能、海水盐度差能、海洋热能等等。拍动翼海流能采集系统是受水生动物运动能力启发而提出的一种新的海流能采集方法。与传统的用于采集海流能的叶轮机相比,拍动翼海流能采集系统具有易于在潜水中布置、能充分利用空间、对水生动物更加友好、对通航影响较小等特点。根据目前拍动翼能量采集系统的研究现状,本文考虑翼与周围流体之间的流固耦合,对拍动翼海流能采集系统进行了系统研究。首先,本文确定了系统最优的(f*,θ0)参数空间,其中f*为拍动频率,θ0为转角幅值;评估了非正弦转动提高拍动翼海流能采集系统能量采集性能的效果;研究了惯性和阻尼对非正弦拍动翼海流能采集系统的影响;另外,本文还研究了由翼尖效应和三维不稳定性引起的三维效应。最后本文基于全主动运动模型研究了自由面对拍动翼海流能采集系统的影响。首先,在关于非正弦转动对拍动翼海流能采集系统影响的研究中,本文确定了正弦转动下使系统取得最高能量采集效率的参数组合为θ0 = 75°,f*= 0.16,取得的最高能量采集效率为32%。然后,本文通过增加控制翼转动轨迹的参数β的值使翼的转动轨迹由正弦转动转变为方波型转动,研究了非正弦转动的影响。本文研究发现,当系统以最优参数组合运行时,非正弦转动提高其能量采集性能的作用非常有限,系统能量采集效率的上限并没有提高。对于小转角幅值的工况,本文得到了与前人一致的结论,采用非正弦转动确实可以提高系统的能量采集效率。但当转角幅值及拍动频率都取最优值的时候,非正弦转动对系统能量采集效率的影响是负面的。根据本文的研究结果,采用简单的方波型非正弦转动方式不能提高半主动拍动翼海流能采集系统的能量采集效率上限。第二,在关于惯性和阻尼对半主动拍动翼海流能采集系统影响的研究中,本文首先在质量比r = 1时进行了参数化研究,确定了系统运行的最佳运动参数,取得的最高能量采集效率为η=34%。然后在最优运动参数下进行了r = 0.125到r = 100的计算。本文发现,半主动系统的能量采集效率随着水翼与其排开的流体的质量之比r的增加而单调下降。对于r10的工况,系统的输出功率随质量比的变化较小,一直保持在较高的水平,因此,从输出功率的角度来讲,此时惯性的影响可以忽略不计。半主动拍动翼海流能采集系统的转动与平动之间的相位差具有自适应性,在该部分的研究中取得的转动与平动最优相位差为Φ≈82°。此时,水翼运动与周围涡的发展具有良好的同步性。本文关于阻尼对拍动翼海流能采集系统影响的研究发现,系统的能量采集效率随着阻尼的增加先上升后下降,存在使系统的能量采集效率最高的最优阻尼c*≈0.5—0.7。该结论与线性理论分析的结果有差别。这是因为线性理论仅适用于雷诺数无限大的情况,并且没有考虑前缘涡的影响。第三,在三维效应对系统能量采集性能影响的研究中,本文选取有限展长的水翼及展向设为周期性边界条件的工况进行研究。根据本文的计算,对于有限翼展的工况,系统的能量采集效率随展弦比的减小而降低。不同拍动频率的工况对翼展的敏感程度不同,大。因此,系统的最优拍动频率随展弦比增大而增大。另外,本文发现,三维效应包含两方面因素:翼尖效应和流场的三维不稳定性。本文基于全主动模型,运用Floquet稳定性分析,研究了雷诺数对三维不稳定性的影响,确定了尾流转捩的临界雷诺数。三维直接数值模拟取得了与Floquet稳定性分析一致的结果。最后,关于自由面对拍动翼海流能采集系统影响的研究,本文首先根据系统的实际工作状况选取三个傅汝德数研究了浸没深度的影响。研究发现,当水翼浸没深度与弦长之比较小的时候(d/c8),自由面对系统能量采集效率的影响比较显著,此时系统的能量采集效率随着浸没深度的减小而迅速升高。本文还对傅汝德数的影响进行了研究。当Fr1.2时可以不考虑傅汝德数的影响,在此傅汝德数范围内系统的能量采集效率表现出很好的稳定性。但是,当傅汝德数进一步增大的时候,极端傅汝德数会使系统的能量采集效率降低。
[Abstract]:In the ocean, there are renewable and clean energy with great energy, including current energy, wave energy, wind energy, sea salinity difference energy, marine heat energy and so on. The current flapping wing energy acquisition system is a new kind of current aquatic animal movement inspired by the collection method. Compared with the traditional turbine for collecting ocean current energy, ocean current energy acquisition system of flapping wing is easily in diving arrangement, can make full use of space, more friendly, the characteristics of aquatic animal navigation has little impact. According to the current research status of flapping wing energy acquisition system at present, considering the coupling between the wing and the surrounding fluid flow, the flapping wing current energy acquisition system were studied. First of all, this paper determined the optimal system (f*. 0) parameter space, where f* is the flapping frequency, 0 angle theta amplitude; evaluation of the non sinusoidal currents can improve rotation of the flapping wing energy acquisition performance data acquisition system effect; inertia and damping can influence the acquisition system of non sinusoidal flapping wing flow on the sea; in addition, this paper also studies the 3D effect caused by the tip effect and three-dimensional instability. Finally, all active motion model is studied based on the free face of flapping wing ocean current energy acquisition system. First of all, in the study of non sinusoidal rotational energy acquisition system influence on flapping wing currents, we determined the parameters of combined sine rotation to achieve the maximum efficiency of energy acquisition system for 0 theta = 75 DEG, f*= 0.16, the highest energy collection efficiency is achieved 32%. Then, by increasing the parameter beta of the control wing's rotation trajectory, the rotation trajectory of the wing is changed from sinusoidal rotation to square wave rotation, and the influence of non sinusoidal rotation is studied. This paper finds that when the system runs in the best parameter combination, the effect of non sinusoidal rotation on improving the energy collection performance is very limited, and the upper limit of the energy collection efficiency of the system is not improved. For the condition of the small angle amplitude, this paper obtains the agreement with the predecessors. The non sinusoidal rotation can improve the energy acquisition efficiency of the system. But when the angle amplitude and flapping frequency are the optimal value, non sinusoidal rotation effect on the energy collection efficiency of the system is negative. According to the results of this study, using a simple square wave of non sinusoidal rotation cannot be improved semi-active flapping wing marine current energy collection efficiency limit acquisition system. Second, research on the inertia and damping semi-active flapping wing can affect the current acquisition system, firstly, when the weight ratio of R = 1 for the parametric study, the best motion parameters of the system were determined, the highest energy collection efficiency achieved for =34%. Then the calculation of R = 0.125 to r = 100 is carried out under the optimal motion parameters. It is found that the energy acquisition efficiency of a semi-active system decreases monotonically with the increase of the ratio of R to the mass of the hydrofoil and its discharged fluid. For the working condition of R10, the output power of the system changes little with the mass ratio. It keeps at a higher level. Therefore, from the point of view of output power, the influence of inertia can be ignored. Phase rotation between the semi-active flapping wing current energy acquisition system and translational difference is adaptive, made in the study of this part of the rotation and translation of the optimal phase difference phi = 82 degrees. At this time, the movement of hydrofoil and the development of the surrounding vortices have good synchronism. This paper studies on the damping effect on the flapping wing current acquisition system found that the efficiency of energy acquisition system with the increase of damping increased after the first drop, the system energy collection efficiency highest optimal damping c* = 0.5 - 0.7. The result of this conclusion is different from the result of linear theory. This is because the linear theory is only applicable to the infinitely large Reynolds number and does not take into account the influence of the leading edge vortices. Third, in the study of the influence of three-dimensional effect on the energy harvesting performance of the system, we choose the finite extended length hydrofoil and the developing conditions as periodic boundary conditions. According to the calculation in this paper, the energy acquisition efficiency of the system decreases with the decrease of the aspect ratio for the limited wingspan. The sensitivity of different flapping frequency conditions on different span, large. Therefore, the optimal flapping frequency system with the aspect ratio increases. In addition, this paper found that the 3D effect consists of two factors: the three-dimensional instability tip effect and flow field. Based on the full active model and the Floquet stability analysis, the influence of Reynolds number on the three-dimensional instability is studied, and the critical Reynolds number of the wake transition is determined. The results of the three-dimensional direct numerical simulation are consistent with the stability analysis of Floquet. Finally, research on flapping wing current acquisition system can influence the effect of free face, according to the actual working condition of the system selects three number of Fu Rude immersion depth. The study found that, when the immersion depth and length of the hydrofoil is relatively small (d/c8), when the influence of free surface energy acquisition system efficiency significantly, the efficiency of energy acquisition system increases rapidly with the decrease of the immersion depth of the. The influence of Fu Rude number is also studied in this paper. When Fr1.2 does not consider the influence of the Fu Rude number, the energy acquisition efficiency of the system in the range of the Fu Rude number shows a good stability. However, when the Fu Rude number is further increased, the extreme Fu Rude number will reduce the efficiency of the system's energy acquisition.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P743.1;O352

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