基于CFD的猪舍内外环境空气质量模拟研究

发布时间：2018-01-09 18:21

本文关键词：基于CFD的猪舍内外环境空气质量模拟研究　出处：《浙江大学》2017年硕士论文　论文类型：学位论文

【摘要】：猪舍内气流流速、温度、相对湿度等湿热环境及氨气(NH3)浓度是影响猪只健康及生产性能非常重要的因素,对这些主要的猪舍内环境参数进行评估分析能有效地发现猪舍环境问题,并提供改善意见及时减少养殖场经济损失。同时,随着养殖场规模及集约化程度逐渐增加,养殖场向外排放的空气污染物,已不容忽视,空气污染物扩散模拟方法是目前对养殖场空气污染浓度影响评价的主要途径。本研究应用计算流体力学(CFD)技术对猪舍内、外环境质量进行评估分析,并模拟对比了不同清粪方式对猪舍内环境质量的影响和不同主导风向对猪场产生的NH3扩散影响。研究结果可为集约化猪场的选址布局和具体设计建造提供理论依据和指导。本研究选取两个规模猪场分别进行猪舍内外环境质量研究,以计算流体力学为理论基础,采用Navier-stokes和Species transport方程组以及RNG k-ε湍流模型,运用GAMBIT 2.4.6和FLUENT 16.0软件为工具对中国东南地区典型的限位饲养模式的怀孕母猪舍内气流流速、温度、相对湿度和氨气浓度进行了三维稳态模拟,以及具有代表性的集约化养殖场NH3排放扩散模拟,研究结果如下:1)以限位饲养、水泡粪清粪方式、机械通风的怀孕母猪舍为研究对象,运用FLUENT对冬季舍内环境最恶劣时期的气流流速、温度、相对湿度和NH3浓度进行模拟。模拟结果为:该怀孕母猪舍内动物呼吸带高度的气流流速范围为0～0.83m/s,平均风速为0.31m/s;温度范围为11.5～25℃,平均17.1℃;相对湿度范围为35.3%～51.5%,平均43.6%;NH3浓度范围为1.5～7.5 mg/m~3,平均NH3浓度为4.72 mg/m~3。舍内环境基本符合冬季怀孕母猪对环境的需求,不过存在NH3略高、部分区域气流流速过大、分布不均匀以及通风死区的情况。根据该怀孕母猪舍的现有条件,提出设计了一种采用干湿分离机械清粪方式的猪舍,对比两种猪舍内环境发现,采用干湿分离机械清粪方式的猪舍气流流速得以减小,舍内NH3浓度也从平均4.72 mg/m~3下降至2.63 mg/m~3,整体环境比之前有所改善。2)以中国东南地区一所典型的集约化猪场为研究对象,检测并分析其中不同生长阶段的猪舍内NH3浓度,得出育肥舍、保育舍、怀孕母猪舍和分娩母猪舍内NH3浓度分别为 6.91±4.59mg/m~3、5.02±3.13mg/m~3、4.37±2.96mg/m~3 和 3.68±2.68mg/m~3。基于该试验数据,将猪舍作为NH3排放源,运用FLUENT软件模拟了主导风向分别为东北风、南风、北风和西南风向情况下NH3扩散情况,模拟结果为:当校正系数为0.05～1.38时,可认为NH3扩散模拟与实测值吻合度良好,主导风向和风速是影响NH3扩散的主要因素,风速越大,NH3扩散距离也越远,冬季最远可达700m。该猪场下风向处存在人群密集场所,冬季这些区域NH3浓度甚至达到3mg/m~3,对周围居民的影响已不容忽视。
[Abstract]:The air velocity, temperature and relative humidity in piggery, hot and humid environment and ammonia (NH3) concentration is an important factor affecting the health and production performance of pigs, analysis and evaluation can effectively find the piggery environment problems of environmental parameters of the main house, and provide improvement suggestions in a timely manner to reduce farm economic loss. At the same time, along with the culture field scale and intensive degree increased gradually, the farm of the emission of air pollutants, can not be ignored, air pollutant diffusion method is present on the evaluation of effect of air pollution concentration farms in the main way. The research and application of computational fluid dynamics (CFD) technology of Ishane, analyze the external environment quality assessment, and simulation the effects of different methods on environmental quality of pig manure removal in different dominant wind direction of the farm produce and the influence of NH3 diffusion. The results can be used for intensive pig farms The layout of the site and the specific design and construction to provide a theoretical basis and guidance. This study selected two pig farms were studied the internal and external environment of pig, based on theory of computational fluid dynamics, using Navier-stokes and Species transport equations and RNG k- turbulence model, using GAMBIT 2.4.6 and FLUENT 16 software flow of pregnant sows limit the typical region in the Southeast China bit feeding mode of the flow velocity, temperature, relative humidity and ammonia concentration of the three-dimensional steady state simulation, and the intensive farms NH3 representative emission diffusion simulation, the results are as follows: 1) to stop feeding, vesicular droppings dung cleaning, mechanical ventilation of pregnant sows to study the object, using the air flow, the worst winter indoor environment FLUENT temperature, relative humidity and NH3 concentration were simulated. The simulation results for the pregnant sows Can animal breathing zone air velocity height range is 0 ~ 0.83m/s, the average wind speed is 0.31m/s; the temperature range of 11.5 to 25 DEG C, average 17.1 DEG C; relative humidity ranges from 35.3% to 51.5%, average 43.6%; NH3 concentration range of 1.5 ~ 7.5 mg/m~3, the average NH3 concentration of 4.72 mg/m~3. shed environment accords with the winter pregnant sows needs of the environment, but there is a slightly higher NH3, part of the regional air velocity is too large, uneven distribution of ventilation and dead zone. According to the existing conditions of the pregnant sow house, put forward a design method of pig manure removal by dry separation machine, a comparison of two in piggery environment, pig airflow velocity the mechanical separation of wet and dry dung cleaning mode can be reduced, indoor NH3 concentrations from an average of 4.72 mg/m~3 down to 2.63 mg/m~3, the overall environment has improved than before.2) in intensive southeast region of a typical China Pig farm as the research object, the detection and analysis of different growth stages in the piggery NH3 concentration, the fattening of homes, nursery, pregnancy and childbirth parent homes NH3 concentration were 6.91 sows in piggery + 4.59mg/m~3,5.02 + 3.13mg/m~3,4.37 + 2.96mg/m~3 and 3.68 + 2.68mg/m~3. of the test data will be based on pig as NH3 emission source, using FLUENT software simulation of the dominant wind direction respectively, northeast, South, North and southwest wind NH3 diffusion case, simulation shows: when the correction coefficient is 0.05 ~ 1.38, can think of the NH3 diffusion simulation and measured values in good agreement, the dominant wind direction and wind speed are the main factors affecting the diffusion of NH3, the greater the wind speed, the diffusion of NH3 the distance is far, far away as the winter 700m. farms leeward existence of crowded places, the concentration of NH3 in winter and even reached 3mg/m~3, the impact on the surrounding residents have been ignored.

【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S828

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