【作者】 赵阳；

【导师】 陈永平；

【作者基本信息】 东南大学 ， 动力工程（专业学位）， 2018， 硕士

【摘要】 柴油发电机为负责天文观测、冰芯勘测等多项科考任务的南极Dome A科考平台提供能源保障,其排放烟气中含有大量细颗粒物(DPM),在大气中扩散后会影响科考平台附近大气的透明度,从而影响天文观测的效果。另外,由于南极Dome A环境的特殊性,一方面,其低温、低压的特点会加重柴油机的排放,尤其是颗粒物,另一方面,其多变的风场会使烟气的影响区域更加复杂,难以界定。因此开展柴油机在南极Dome A低压环境下的各组分的排放特性及烟气的扩散行为研究,对南极能源支撑平台建设有重要的参考和指导意义。柴油机排放特性受进气压力、缸内温度、燃油类型等因素影响。虽然当前对常压条件下柴油机排放特性的已有了较为深入的研究,但针对南极高原低压环境的柴油机排放特性研究还非常缺乏。此外,低温低压环境下,柴油机烟气在Dome A特有气象环境下的扩散规律亦不清晰。为此,本文设计搭建了南极低压环境模拟平台,利用实验方法对南极模拟环境下柴油机的排放产物的浓度进行了测量。此外,本文还基于小风扩散模型和高斯烟羽模型对柴油机排放烟气在南极Dome A大气环境中的扩散规律进行了研究,并进一步考虑南极Dome A长期的风向、风速分布,建立了烟气的长期平均浓度计算模型,对柴油机排放产物中颗粒物在南极Dome A风场作用下的长期影响范围进行了研究。概括起来,本论文主要研究内容及结论如下:开展了南极柴油机排放特性实验,研究了柴油机运行转速、环境气压和燃料类型对其排放产物中各组分排量的影响规律。结果表明:(1)环境气压降低导致柴油机排放产物中CO增加,低压下CO排量的增幅更为明显,HC的排量先减小后增加,NO_X的排量下降以及柴油机颗粒物的排量增加;(2)柴油机运行转速增加导致CO的排量增加,HC的排量先降低后增加,NO_X的排量下降,柴油机颗粒物的排量先降低后增加,在转速为2400r/min时达到最低,对比常压环境,南极低压环境下,CO受运行转速的影响更为显著;(3)相比于零号柴油,柴油机使用航空煤油时能够有效降低CO和PM的排放,但NO_X的排量要高于使用零号柴油时的NO_X的排量。利用小风扩散模型和高斯烟羽模型及长期平均浓度计算模型研究了柴油机排放烟气在南极Dome A大气环境中的扩散规律及在南极Dome A风场作用下柴油机排放产物中颗粒物的长期影响范围。结果表明:(1)在单风向扩散作用下,颗粒物沿下风向的影响半径要远远大于其沿横向和纵向的扩散半径,并且风速越大,对应的烟气影响半径越小;(2)对于风速较小甚至静风时,颗粒物的扩散属于小风扩散的范畴,颗粒物沿各个方向的扩散较为均匀,烟羽表现为细长的柱状结构并向下风向倾斜,颗粒物的浓度在烟羽中心线上最大,并向四周递减(3)在长期多风向、风速耦合作用下,Dome A烟气最大影响区域集中在西南方向,烟气最小影响区域主要位于排烟口的正南方,为尽可能减小柴油机烟气对天文观测的影响,天文设备优选布置于发电舱正南方向15m以外。更多还原

【Abstract】 Several scientific exploration activities such as ice core survey and astronomical observation have been conducted at the research station in the Antarctic Dome A,which is supported by diesel generators.Emissions exhausted from the diesel generators contain a lot of fine particulate matter,which will affect atmospheric transparency near the research station and make astronomical observations worse.In addition,considering the particularity of the Antarctic environment,low temperature and low pressure will increase the amount of fine particulate matter emitted from diesel generators.Meanwhile,the variability of wind direction and speed make the scope affected by exhaust emissions difficult to determine.Therefore,research on the emission performance of diesel engine and the diffused features of diesel smoke in the South Pole have important reference value and guiding significance to the construction of the research station.The emission performance of diesel engine is affected by various factors such as intake pressure,cylinder internal temperature and fuel type.At present,numerous studies on the emission performance of diesel engine under at normal temperatures and pressures have been carried out.However,There has been a lack of research on the emission performance under low temperature and pressure like the Antarctic.Furthermore,the diffused features of diesel smoke in this Antarctic environment is still indistinct.For this purpose,the Antarctic low pressure simulation platform has been designed and built.An experiment measuring the concentration of exhaust emissions while operating under low pressure in the Antarctic has been conducted.Moreover,a research based on Gauss diffusion model and atmospheric diffusion model in conditions of light air have been conducted to study diffusion rule in the Antarctic Dome A.Finally,a scientific long-term average concentration model taking account of joint frequency distribution in both wind direction and speed has been established.It is used to study the range affected by particulate matter emitted by diesel engine under the impact of wind site at Dome A in the Antarctic.In a word,the research contents and related conclusions in this thesis can be summarized as follows:The experimental studies of particulate emissions from diesel engine in the Antarctic has been conducted in this thesis,especially the relationship between the concentration of various component and engine speed,atmospheric pressure and fuel type.This study shows:(a)With atmosphere pressure going down,carbon monoxide concentration will increase,especially there is a rapid increase under low atmosphere pressure.Hydrocarbon concentration in exhaust emissions will decrease first and then increase.Meanwhile,the concentration of Nitrogen oxide decreases and the one of particulate matter increases.(b)With the engine speed increasing,carbon monoxide concentration will increase.Hydrocarbon concentration of exhaust emissions will decrease first and then increase.Meanwhile,the concentration of Nitrogen oxide will decrease.The particulate matter concentration from diesel engine will decrease first and reaches minimum value where the engine speed is 2400 rpm,then increase.Compared with ordinary atmosphere pressure,the relationship between carbon monoxide concentration and engine speed tend to be more visible and explicit under low pressure in the Antarctic.(3)Compared to general diesel fuels,using jet fuel in diesel engine can effectively reduce the concentration of carbon monoxide and particulate matter.On the contrary,Nitrogen oxide concentration is greater than the one using general diesel fuels.Gauss diffusion model and atmospheric diffusion model under conditions with low winds have been established to study fine particulate matter diffused feature at Dome A in the Antarctic.Meanwhile,long-term average concentration model based on meteorological data has been established to study the range affected by particulate matter emitted by diesel engine under the impact of wind site at Dome A in the Antarctic.The study shows:(1)on the condition that wind direction and speed keep unchanged,the affected area to the leeward side is much larger than the one along horizontal and vertical direction.With the increase of wind speed,the affected area tends to be smaller.(2)On the condition that wind speed is very small even calm,the diffusion of particulate matter along all directions tends to be more uniform.Smoke plume presents a slender structure and lean to the leeward side.The concentration of particulate matter is the largest at the centerline of the plume and decreases toward all direction.(3)Under the combined effect of wind direction and speed in the long term.The maximum area affected by particulate matter is located in the southwest while the minimum one is located in the south direction.In order to reduce the negative effects of fine particulate matter on astronomical observation,it’s recommended that the telescopic station can be placed in the south direction of emission source.更多还原