连续波DF/HF化学激光器环形喷管与线形喷管的对比

Comparative analysis of annular nozzle and linear nozzle in CW DF/HF chemical laser

环形喷管阵列主要用于环柱型化学激光器,它可以分为两种构型:直喉道型和圆喉道型。二者都可以由线性喷管阵列变换得到。在变换前后保持相同的增益区体积的前提下,环形喷管阵列的横向尺寸将减小为线性喷管阵列的1/π倍,这将更有利于激光器的紧凑化设计。由于圆喉道型环形喷管阵列相对直喉道型更具实用价值,通过三维的数值模拟,比较了圆喉道型环形喷管单元和线形喷管单元的流场特性。结果表明:在相同截面尺寸及喉道面积的条件下,环形喷管出口气流马赫数、气流速度分别比线形喷管高4.03%,0.356%,静温、静压分别比线形喷管低6.08%,19.7%。在喷管的收缩段,两种喷管的边界层发展规律及厚度值基本相同,而环形喷管的气流速度要快于线形喷管,因此环形喷管的氟原子复合比例要略低于线形喷管。

Annular nozzle array is principally used in cylindrical laser.It contains two geometrical configurations of straight-throat style and circular-throat style.Both of them can be acquired by transforming linear nozzle array.Under conditions of constant gain volume,transverse dimension of annular nozzle array will reduced to 1/π of linear nozzle array.Thus annular nozzle array is especially suitable for the design of small-volume chemical laser.Annular nozzle array with circular throat is more applicable in actual chemical laser.Consequently flow field characteristics of annular nozzle unit with circular throat and linear nozzle unit were calculated based on three-dimension computational fluid dynamics methods.The numerical siumulation results demonstrate that Mach number and velocity magnitude in annular nozzle exit plane are higher by 4.03% and 0.356% as compared with linear nozzle under conditions of constant nozzle section dimension and throat area,whereas static temperature and static pressure of annular nozzle is lower by 6.08%,19.7%.Boundary-layer thicknesses of convergent section of two kinds of nozzles grow basically according to same trends and dimensions,nevertheless mean velocity magnitude of annular nozzle exit plane is faster than that of linear nozzle.As a result recombination proportion of F-atom is lower appreciably in annular nozzle exit plane than in linear nozzle exit plane.