摘要
拉瓦尔喷管拥有将气体从亚音速加速至超音速的能力,具有广泛的应用场景和重要的研究意义。超音速火焰喷涂(HVOF)技术产生的较高的焰流速度和较低的焰流温度也得益于拉瓦尔喷管结构设计,其中在拉瓦尔喷管型线设计中,由于马赫数和气体温度的剧烈变化,应着重考虑比热比变化的影响。聚焦于超音速流场中真实的气体效应,采用特征线法分别设计定比热比与变比热比条件下的拉瓦尔喷管扩张段型线,借助ANSYS Fluent软件建立超音速火焰喷枪的二维轴对称数值模型,对气体流场的仿真结果进行比较。研究发现,当马赫数小于1.5时,定比热比与变比热比的型线接近,可以忽略比热比变化的影响;当马赫数大于2时,二者差异较大,比热比变化不容忽视。考虑燃烧反应后,超音速段轴线上的焰流温度分布集中且高达2000~3000 K;焰流在拉瓦尔喷管喉部得到充分加速,速度达到2000 m/s;在比热比为1.32条件下设计的拉瓦尔喷管相较其他喷管在焰流速度上优化了1%~3%,并且随着轴向距离的增加,变比热比喷管具有速度降低趋势更缓慢等优点。
Laval nozzle has the ability to accelerate gas from subsonic to supersonic,so it has a wide range of application background and a high priority of research value.The higher flame velocity and lower flame temperature generated by High Velocity Oxygen Fuel(HVOF)technology also benefit from the structural design of Laval nozzle.In the contour design of Laval nozzle,the influence of specific heat ratio change should be taken into account due to the drastic changes of Mach number and gas temperature.Focusing on the real gas effect in the supersonic flow field,the characteristic line method was used to design the expansion section contour of Laval nozzle under the condition of constant specific heat ratio and variable specific heat ratio respectively.The two-dimensional axisymmetric numerical model of supersonic flame spray gun was established by ANSYS Fluent software,and the simulation results of gas flow field were compared.Findings:when the Mach number is less than 1.5,the contour of constant specific heat ratio is close to that of variable specific heat ratio,and the influence of specific heat ratio change can be ignored,but when the Mach number is greater than 2,the difference between them is great,thus the specific heat ratio change cannot be ignored;considering the combustion reaction,the temperature distribution of the flame flow on the axis of the supersonic section is concentrated and up to 2000~3000 K,and the flame flow is fully accelerated at the throat of Laval nozzle,with the velocity is up to 2000 m/s;the Laval nozzle designed under the condition of specific heat ratio of 1.32 has optimized the velocity of 1%~3%compared with other nozzles,and with the increase of axial distance,the variable specific heat ratio nozzle has the advantages of slower speed decrease.
作者
詹银晓
徐天艺
戴万祥
王珂
张帅
ZHAN Yinxiao;XU Tianyi;DAI Wanxiang;WANG Ke;ZHANG Shuai(College of Mechanical Engineering,Ningxia University,Yinchuan 750000,China;Wuzhong Instrument Co.,Ltd.,Wuzhong 751100,China)
出处
《工业技术创新》
2023年第2期20-31,共12页
Industrial Technology Innovation
基金
宁夏自然科学基金资助项目(2021AAC03038)。
关键词
拉瓦尔喷管
型线
比热比
马赫数
焰流温度
Laval Nozzle
Contour
Specific Heat Ratio
Mach Number
Flame Temperature
