开孔壁蜂窝器整流特性实验研究

Experimental study of flow straightening and turbulence reduction characteristics for porosity honeycomb

蜂窝器是安装在风洞稳定段中用来提高风洞试验段气流均匀性、降低气流偏角及湍流度的重要整流装置。普通的实壁蜂窝器需要通过提高蜂窝器单元的长径比来达到提升整流特性的目的,但同时带来了损失系数增加等问题。设计了一种在蜂窝单元壁面开孔的蜂窝器,通过蜂窝器壁面上的开孔,实现了蜂窝器单元之间的旋涡和压力的传递,可以有效地提高蜂窝器的整流效果。在0.55m×0.4m低噪声航空声学风洞闭口试验段中,在不同来流速度条件下,使用热线风速仪对普通蜂窝器和开孔壁蜂窝器下游的速度及湍流度分布特性进行了试验研究。实验结果表明,与普通的实壁蜂窝器相比,开孔率为50%的开孔壁蜂窝器下游的湍流度可降低13.8%,蜂窝器下游的速度分布得到了改善,局部气流偏角也明显减小。在风洞设计中,使用优化后的开孔壁蜂窝器可以减少阻尼网的层数或收缩段的收缩比,从而降低风洞的运行能耗,并减少风洞的建设费用。

The honeycomb is an important device which is installed in wind tunnel settling chamber to improve the flow uniformity and decrease the flow angle as well as the turbulence intensity in the wind tunnel test section. For a regular honeycomb, in order to improve the flow straightening and turbulence reduction characteristics, a large length-diameter ratio must be used in the design of the honeycomb which results in the increase of total pressure loss of the honeycomb. A new type of honeycomb with a group of small holes on the wall of honeycomb cells is designed. This type of porosity honeycomb can achieve the exchange of the vortices and pressure between different cells to significantly improve the flow quality downstream the honeycomb. In the solid wall test section of the 0.55m×0.40m low noise aeronautic acoustic wind tunnel, the 2D hot wire is used to measure the turbulence intensity and velocity distribution downstream the porosity honeycomb and the regular one respectively with different flow velocities. The experimental results indicate that the honeycomb with 50% transverse porosity can reduce the turbulence intensity by 13.8% compared against the regular one. The velocity distribution downstream the honeycomb becomes smoother and the flow angle is also reduced. The design of the flow straightening and turbulence reduction system for the wind tunnel with the optimized porosity honeycomb can reduce the number of screens or the constriction ratio of the wind tunnel, and therefore, reduce the power consumption and the construction budget of wind tunnels.