采用态-态模型的高温空气非平衡喷管流数值研究
NUMERICAL STUDY OF HIGH-TEMPERATURE NONEQUILIBRIUM AIR NOZZLE FLOW WITH STATE-TO-STATE MODEL
王辉 1曾明 1段欣葵 1王东方 1刘伟1
作者信息
- 1. 国防科技大学空天科学学院,长沙 410073
- 折叠
摘要
采用态-态模型在总温T0=2000 K～8000 K、总压p0=1～20 MPa范围,开展高温空气准一维非平衡喷管流动数值模拟.考虑 5 种化学组元(N2,O2,NO,N,O),其中N2,O2,NO分别有 61,46,48 个振动能级,将不同振动能级上的粒子视为不同组元,共 157 个组元.对未见公开文献给出速率系数的分子能级跃迁过程,综合振动能方程松弛时间和其他类似微观过程跃迁速率系数进行折算.计算结果表明,喷管喉道前流动接近平衡,喉道后出现非平衡,喉道下游不远处发生化学组元质量分数、较低振动能级分子数和表征振动能的振动温度的冻结,N2 的振动温度冻结较NO和O2 早,冻结值也更高;对振动能级跃迁起主导作用的微观机制是平动-振动能量交换(VT)过程,复合反应生成的分子更多位于中等振动能级;喷管非平衡和冻结区域分子能级分布偏离振动温度下的玻尔兹曼分布,高能级出现过分布;提高驻室总压能够降低喷管流动非平衡程度,推迟热化学冻结发生.
Abstract
Using state-to-state model,quasi-one-dimensional nozzle flow of high-temperature nonequilibrium air is investigated numerically.The five chemical species mixture N2/O2/NO/N/O is considered with 61 bound vibrational levels for N2,46 for O2,and 48 for NO.Each vibrational state is regarded as a pseudo species,which leads to a total of 157 species for the air mixture.The state-specific transition rate coefficients of some processes,which have no available data,are calculated based on the relaxation time and the rate coefficients of other similar processes.The flow simulation and analysis are made for reservoir temperature from 2000 to 8000 K and pressure from 1 to 20 MPa.The nozzle flow is essentially in equilibrium before the throat,but deviates from equilibrium shortly after the throat.The mass fraction of chemical species,populations of lower energy levels,and vibrational temperatures are frozen in the downstream not far away from the throat.The vibrational temperature of N2 is freezing earlier and has a higher frozen value than that of NO and O2.The process of vibration-translation(VT)energy exchange is predominant for vibrational transition,the recombination reaction generates molecules preferably to middle vibrational levels.Throughout the nonequilibrium and frozen zone,the vibrational population distributions are far from Boltzmann distribution at vibrational temperature,and feature a large overpopulation of the high-lying vibrational levels.Increasing the reservoir pressure could reduce the nonequilibrium to a certain extent and delay the flow thermochemical freezing.
关键词
热化学非平衡/态-态模型/振动能级分布/喷管流动/高焓风洞Key words
thermochemical nonequilibrium/state-to-state model/vibrational population distribution/nozzle flow/high enthalpy wind tunnel引用本文复制引用
出版年
2024
NETL
NSTL
万方数据