超声速混合层凹腔隔板的自激振动特性实验研究

Experimental Studies on Self-Excited Vibration Characteristicsof Splitter Plate with a Cavity in Supersonic Mixing Layer

关键词:  超声速混合层  凹腔  混合增强  自激振动  声学自激振荡

Key words:  Supersonic mixing layer  Cavity  Mixing enhancement  Self-excited vibration  Acoustics self-oscillation

摘要:

为了克服强迫振动诱导混合增强难以工程实现的缺陷，提出隔板自激振动诱导混合增强的新技术，而设计最优自激振动频率的隔板是该技术的难题。采用平板开凹腔的隔板构型，通过实验手段并结合数值仿真，分析了凹腔隔板的自激振动特性。研究表明，凹腔的声学自激振荡引起压力随时间的波动是隔板自激振动的直接原因；隔板的约束条件与凹腔的构型参数长深比、后缘倾角对自激振动特性有重要影响；自激振动频率与限位尺寸呈反相关，当限位尺寸为0时，频率提高了324.63%；与凹腔长深比[K=1]时相比，[K=7]的频率降低了19.36%。自激振动频率与后缘倾角呈正相关，后缘倾角为[90°]时，频率提高了23.15%。改变约束条件可大幅提高自激振动频率，是隔板优化设计的一个重要方向。

Abstract:

In order to surmount the disadvantage that mixing enhancement induced by forced vibration cannot achieve easily in engineering application， a new technique that employing self-excited vibration splitter enhances mixing process was proposed. The design method for a splitter plate with certain band frequency is the key problem in this technique. The splitter plate with a cavity was employed in this paper and characteristics of self-excited vibration were analyzed systematically mainly through experimental study combing with numerical simulation. Results indicate that fluctuation of pressure resulting from acoustic self-oscillation of a cavity on the upper surface is the immediate cause of self-excited vibration. Factors such as constraint condition of the splitter plate， length depth ratio and ramp angle of the cavity play a significant role on characteristics of self-excited vibration. The frequency of self-excited vibration is inversely correlated with limit distance. Frequency grows sharply by 324.63% when limit distance is 0mm. It decreases by 19.36% at length depth ratio [K=7]comparing with [K=1].Besides， frequency of self-excited vibration and ramp angle of cavity have positive correlation and it increases by 23.15% at the angle of [90°].Changing constraint condition is a chief orientation to optimize splitter plate because it can obtain an outstanding increase in frequency.