摘要
夏季高温造成奶牛热应激,物理降温以蒸发散热缓解奶牛高温,其中喷淋降温系统是我国常用的降温方法。利用激光雨滴谱仪(LPM)对6种不同标准扇形喷嘴(9010、9030、9060、9080、90100、90120)在0.15、0.20、0.25 MPa工作压力下进行了测试,计算分析了6种喷嘴在不同工作压力下水滴粒径的分布,研究了水滴粒径与喷淋流量、单个水滴动能、喷淋强度的关系。结果表明:水滴粒径分布呈正态分布模型,不同工作压力(0.15、0.20、0.25 MPa),所测6种不同型号的喷嘴水滴平均粒径为0.475~1.210 mm;水滴粒径与喷淋流量呈线性关系(R2>0.96);9010、9030型号喷嘴在小水滴粒径0.125~0.250 mm范围内占有10%~20%的比例,易雾化飘移,不适合奶牛蒸发降温;不同工作压力下单个水滴动能随水滴粒径的增大而增大,呈幂函数关系(R2>0.96);喷嘴的平均喷淋强度和水滴平均粒径呈指数关系(R^2>0.96),平均喷淋强度均大于72 mm/h。试验得出水滴平均粒径0.801 mm(9060)、0.914 mm(9080)、1.047 mm(90100)、1.210 mm(90120)将仿真奶牛从39.3℃降温至37℃所用时间平均值为85、75、48、30 s。
The high temperature in summer causes heat stress in dairy cows,spray cooling system is one of the most effective physical cooling technologies that is widely used in practice. The laser precipitation monitor（ LPM） was used to measure droplet size,droplet velocity and intensity. Six kinds of standard fan-shaped nozzles（ 9010,9030,9060,9080,90100,90120） were measured with LPM under0. 15 MPa,0. 20 MPa,0. 25 MPa pressures,the droplet distribution,the relationship of droplet diameter and spray flow,single droplet kinetic energy,spray intensity was analyzed. The results show that： the droplet distribution normally distributed model and average droplet diameter are ranged from 0. 475 mm to1. 210 mm under 0. 15 MPa,0. 20 MPa,0. 25 MPa pressures of six different nozzles. Droplet diameter has a linear relation with spray flow（ R^2 0. 96）. 15% ～ 20% of droplet diameters within 0. 125 ～0. 250 mm were sprayed by nozzles of 9010 and 9030 type,which make it easy to drift but not suitable for cows evaporative cooling. The single droplet kinetic energy along with the water droplets was increased with the increase of droplet diameter under three different working pressures, showing a power relationship（ R^2 0. 96）. The mean nozzle spray intensity and mean droplet diameter show anexponential relationship（ R^2 0. 96）. The average intensities of spray were all greater than 72 mm / h,which satisfied the purpose of cows spray cooling system. The experiment concluded that the average drop particle diameter are 0. 801 mm（ 9060）,0. 914 mm（ 9080）,1. 047 mm（ 90100） and 1. 210 mm（ 90120）,which could cool cow from 39. 3℃to 37℃,using 85 s,75 s,48 s and 30 s,respectively.
出处
《农业机械学报》
EI
CAS
CSCD
北大核心
2016年第7期323-331,共9页
Transactions of the Chinese Society for Agricultural Machinery
基金
国家自然科学基金项目(31402115)
国家奶牛产业技术体系项目(CARS-37)
中央高校基本科研业务费专项(92015SYL001)
国家级大学生创新计划项目(2014610019072)
关键词
奶牛
热应激
喷淋降温
水滴分布
水滴动能
喷淋强度
dairy cow
heat stress
spray cooling
droplet distribution
droplet kinetic energy
spray intensity
