除霜喷嘴的高压射流特性分析与结构优化
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摘要
针对蒸发器除霜效率低的问题,设计了两种喷嘴:喷嘴1的射流收缩段为圆弧收缩,引流段和扩散段呈圆柱状;喷嘴2的射流收缩段为直线收缩,引流段和扩散段呈圆锥状。采用理论计算和数值仿真两种方法获得了入口气压在0.3 s内从0.6 MPa快速降至0.1 MPa时的喷嘴射流参数。理论计算与数值仿真结果相近,而数值仿真更为具体地揭示出:喷嘴2的能量损失高于喷嘴1;喷嘴2的气压波动幅度大于喷嘴1;喷嘴2的出口质量平均速度优于喷嘴1。据此设计了综合2种喷嘴特点的喷嘴3,并对喷嘴3的圆弧半径作优化设计。结果表明:当该半径为11 mm时,喷嘴3的射流除霜能力优于喷嘴1和喷嘴2。本文所得结果可为除霜喷嘴的工程设计提供理论支撑。
Aiming at the problem of low defrost efficiency of evaporator, two kinds of nozzles were designed. The contraction section of nozzle 1 was circular arc. The drainage section and diffusion section of nozzle 1 were cylindrical. The contraction section of nozzle 2 was linear. The drainage and diffusion sections of nozzle 2 were conical. The nozzle jet parameters were obtained by theoretical calculation and numerical simulation when the inlet pressure dropped rapidly from0.6 MPa to 0.1 MPa in 0.3 seconds. The results obtained by the theoretical calculation were close to the numerical simulation results. The numerical simulation results showed that the energy loss of nozzle 2 was more than that of nozzle 1. The fluctuation amplitude of air pressure of nozzle2 was higher than that of nozzle 1. The mass average velocity of nozzle 2 was better than that of nozzle 1.On the basis of this, nozzle 3 with the characteristics of two nozzles was designed,and the circular radius of nozzles 3 was optimized. The optimization result showed that the defrosting ability of nozzles 3 was better than nozzle 1 and nozzle 2 when the radius was 11 mm.The results can provide theoretical support for engineering design of defrosting nozzle.
Aiming at the problem of low defrost efficiency of evaporator, two kinds of nozzles were designed. The contraction section of nozzle 1 was circular arc. The drainage section and diffusion section of nozzle 1 were cylindrical. The contraction section of nozzle 2 was linear. The drainage and diffusion sections of nozzle 2 were conical. The nozzle jet parameters were obtained by theoretical calculation and numerical simulation when the inlet pressure dropped rapidly from0.6 MPa to 0.1 MPa in 0.3 seconds. The results obtained by the theoretical calculation were close to the numerical simulation results. The numerical simulation results showed that the energy loss of nozzle 2 was more than that of nozzle 1. The fluctuation amplitude of air pressure of nozzle2 was higher than that of nozzle 1. The mass average velocity of nozzle 2 was better than that of nozzle 1.On the basis of this, nozzle 3 with the characteristics of two nozzles was designed,and the circular radius of nozzles 3 was optimized. The optimization result showed that the defrosting ability of nozzles 3 was better than nozzle 1 and nozzle 2 when the radius was 11 mm.The results can provide theoretical support for engineering design of defrosting nozzle.
引文
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[2]陈巧兰,王鸿博,高卫东,等.喷气织机单圆孔辅助喷嘴结构优化[J].纺织学报,2016,37(1):142-146.
[3]蔡毅,苏国兵.高压水射流喷嘴设计及有限元分析[J].机械设计与研究,2017(6):163-167.
[4]胡俊,郭绍刚,邱明勇,等.激光切割中的超声速喷嘴辅助气体流场分析与结构改进[J].机械工程学报,2009,45(6):251-255.
[5]何青,刘婧,赵晓彤,等.直接空冷凝汽器干式吹扫系统喷嘴结构特性[J].中国电机工程学报,2015,35(13):3351-3357.
[6]KUMAR M,SAHOO R K,BEHERA S K.Design and numerical investigation to visualize the fluid flow and thermal characteristics of non-axisymmetric convergent nozzle[J].Engineering Science and Technology,an International Journal,2018.https://doi.org/10.1016/j.jestch.2018.10.006
[7]杨友胜,张建平,聂松林.水射流喷嘴能量损失研究[J].机械工程学报,2013,49(2):139-145.
[8]李烈.高压水射流掘进机截割头设计[J].机械设计与制造[J],2017(04):77-80.
[9]李海军,何远航,段卓平,等.超高压水射流形成过程中的压力损失研究[J].高压物理学报,2004,18(02):44-48.
[10]盛敬超.液压流体力学[M].北京:机械工业出版社,1980.137-139.
[11]陈凤官,綦耀光,刘新福,等.射流喷嘴流量系数及射流功率转换效率的分析[J].矿山机械,2010(23):20-22.
[12]王玉岭,闫清东,李晋,等.基于CFD的液力变矩器内部流场分布特征研究[J].液压与气动,2015(7):36-40.