Geometric optimisation of piezoelectric fan arrays for low energy cooling
Geometric optimisation of piezoelectric fan arrays for low energy cooling
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DOI：
10.1016/j.ijheatmasstransfer.2019.03.086
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发表时间：
2019-07
影响因子：
5.2
通讯作者：
A. Hales;Xi Jiang
中科院分区：
文献类型：
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作者：
A. Hales;Xi Jiang
建立了一个典型压电风扇叶片的数值模型，并与实验数据进行了对比验证。采用两种数据比较方法，数值误差分别为5.4%和9.8%。该模型是用来探索作为振幅的函数，A，有限的两个叶片的压电风扇阵列在面对面的方向，与叶片振荡的同相和反相的变化。据报道，同相振荡对于在无约束条件下产生最大下游速度和流率是最佳的，这至少部分地是由于相邻叶片之间的有益耦合导致振荡幅度增加。本模型表明，约束有一个显着的有害影响同相振荡。即使在低桨距下，反相振荡也会产生增强的下游空气速度和流速。在P= 8A时，反相振荡产生的下游气流速度相对于单个叶片产生的气流速度可最大地提高17.7%。在相同的螺距的流量增强被发现是18.6%。相比之下，相同桨距下的同相振荡输出的峰值下游空气速度和流量相对于单个叶片产生的峰值下游空气速度和流量减少了23.9%和24.8%。这个最佳的间距，相当于那些在文献中报道的，表明反相振荡是受约束。由于相邻叶片之间跨度上的下游速度虽小但很大，因此通过反相振荡产生大量气流的最佳桨距很大，P> 16 A。然而，通过考虑受限空间中的设计，反相间距应最小化，以最大化通道流应用内的特定横截面积产生的整体气流。定量值被发现偏离到一个小的程度，其他几何和操作参数是不同的，但建立的关系保持。
A numerical model of a typical piezoelectric fan blade is derived and validated against experimental data. Numerical error is found to be 5.4% and 9.8% using two data comparison methods. The model is used to explore the variation of pitch as a function of amplitude, A, for a confined two-blade piezoelectric fan array in face-to-face orientation, with the blades oscillating both in-phase and counter-phase. It has been reported that in-phase oscillation is optimal for generating maximum downstream velocity and flow rate in unconfined conditions, due at least in part to the beneficial coupling between the adjacent blades that leads to an increased oscillation amplitude. The present model demonstrates that confinement has a significant detrimental effect on in-phase oscillation. Even at low pitch, counter-phase oscillation produces enhanced downstream air velocities and flow rates. Downstream air velocity from counter-phase oscillation can be maximally enhanced, relative to that generated from a single blade, by 17.7% at P= 8 A. Flow rate enhancement at the same pitch is found to be 18.6%. By comparison, in-phase oscillation at the same pitch outputs 23.9% and 24.8% reductions in peak downstream air velocity and flow rate, relative to that generated from a single blade. This optimal pitch, equivalent to those reported in the literature, suggests that counter-phase oscillation is less affected by confinement. The optimal pitch for generating bulk airflow from counter-phase oscillation is large, P> 16 A, due to the small but significant downstream velocity across the span between adjacent blades. However, by considering design in a confined space, counter-phase pitch should be minimised to maximise the bulk airflow generated from a certain cross-sectional area within a channel flow application. Quantitative values are found to deviate to a small degree as other geometric and operational parameters are varied, but the established relationships are maintained.