圆柱形充液室中4股贴壁燃气射流扩展特性的实验研究

Experimental study on expansion characteristics of annular four wall combustion-gas jets in a liquid-filled cylindrical chamber

为了探索高温高压周向均布4股贴壁燃气射流在受限空间中的扩展特性,设计了贴壁燃气射流在圆柱形充液室内扩展的实验装置,借助数字高速录像系统,观察了4股贴壁燃气射流在充液室中的扩展过程,发现由Kelvin-Helmholtz不稳定性引起的表面不规则一直存在于整个射流扩展过程;通过处理拍摄记录的射流扩展序列图,获得不同时刻射流扩展的轴向和径向位移;对比了不同破膜喷射压力和喷孔结构参数对4股贴壁燃气射流扩展过程的影响。实验结果表明:喷孔面积越大,贴壁射流初期轴向扩展速度越大,但由于径向扩展达到交汇的时间较早,湍流掺混和干涉强烈,衰减也越快;破膜喷射压力越高,射流径向扩展到达交汇的时间越短;破膜喷射压力从12 MPa升高到20 MPa,射流轴向扩展速度大幅增加,气液湍流掺混效应增强。

The combustion-gas generator and liquid-filled cylindrical chamber are designed to study the expansion characteristics of annular four wall combustion-gas jets under high temperature and high pressure in a confined space. The expansion processes of Taylor cavities formed by combustion-gas jets are observed by means of a high-speed digital photographic system. It is shown that the irregular interface induced by the KelvinHelmholtz instability exists in the entire expansion process of the jets. The axial and radial displacements at different times are obtained from a series of expansion photographs of gas jets. The effects of the blasting injection pressure and the parameters of the nozzle structure on the expansion characteristics of the annular four wall combustion-gas jets are discussed. The experimental results indicate that,the larger the nozzle orifice area,the greater the axial expansion velocity of the wall jets in the prime stage. Meanwhile,the axial expansion velocity attenuates more quickly due to the effect of turbulent mixing and interference. The higher the blasting injection pressure,the earlier the four jets begin converging. Moreover,the axial expansion velocity of the wall jet increases substantially and the gas-liquid turbulent mixing effect becomes much stronger when the blasting injection pressure increases from 12 MPa to 20 MPa.