C919飞机边线噪声级预测算法

为了新飞机试飞前能获得飞机边线噪声级,缩短新飞机噪声合格审定周期,对飞机边线有效感觉噪声级预测方法进行了研究,利用飞机相关物理参数及声压公式建立了完整的飞机边界噪声级预测算法。以波音、空客、CRJ系列飞机为例,验证该算法的有效性。控制飞机单一物理参数变化,分析各参数对飞机边线有效感觉边界噪声值的影响等级,提出降低飞机边线有效感觉噪声值的建议。将该算法应用于预测C919飞机边线噪声值,阐明了该算法在飞机噪声适航审定工作中的重要作用。     

城市交通噪声的统计特性

一、城市交通噪声的统计特性随着国民经济的发展,城市交通运输日益繁忙,机动车辆的数目增加的很快,交通噪声也越来越严重。交通噪声与一般工厂噪声不同,是一种不稳定的噪声。对某一个固定地点来说,交通噪声与附近经过车辆的种类、数量、车速和距离等有关;也和道路的宽窄建筑物的高低有关。由于因素复杂,偶然因素很多,因此噪声不断变化。国内外的研究结果表明,城市交通噪声的A声级的分布基本上符合正态(高斯)分布,正态分布可以表达为:     

道路交通噪声预测模式预测结果的比较

为了分析实际环境影响评价中常用的各种公路交通噪声预测模型预测结果之间存在的差异,并验证各预测方式与实测值之间的相符性,通过对选取的高速公路和市政快速公路采用各种预测模型计算比较,并用实际监测值对各模型预测结果进行验证,结果发现,不同的预测方式会造成预测结果之间昼间4～9 dB、夜间5～10 dB的差异,采用2006版规范计算车速和单车噪声源强,距离衰减考虑车流量大小的预测方式得到的预测结果与实测值最为接近。     

空压机噪声的治理方案和效果

不同的噪声源有不同的治理方法,同一类噪声源,由于所处的地域不同、场所的不同以及标准要求不同,治理方案往往也不同.一项噪声治理工程,既可以是声源控制、消声、吸气、隔声和减振各项措施的综合运用,也可以单独采用某项措施去达标,其差异之一就体现在工程的经济性.宁波市海曙噪声防治研究所在治理一例空压机噪声时,则很恰当地把握了治理工程的经济性原则.充分考虑治理的经济条件,使企业少花钱,又能达到预其的效果.治理后,真正     

牡丹江市交通噪声2000年预测研究

目前,噪声预测的模型较多,本文所应用的负指数模型车流噪声预报公式的推广就是设法证明当多车通的车辆分布服从泊松时,并用一等效车道来近似代替多车道,便可将多车道车流简化为行驶在等效车道上的合成流泊松流来考虑。然后分类叠加合成车流中各辆车对测点的声强贡献,通过求声强的累积量母函数和n阶累积量表达式入手,求出声强分布的特征函败。对此特征函数作逆傅氏变换便得出声强分布的概率密度函数。在满足各态历经过程的假设下,根据声强与声压的关系及统计声级的定义求出系统计声级与等效声级。     

基于数值模拟和响应面法的PRB设计影响研究

影响PRB设计的因素很多,利用COMSOL Multiphysics软件建立地下水连续PRB的流体流动和溶质运移的数值模型,采用响应面方法研究了PRB与含水层渗透系数的比log K、PRB的位置D及PRB的墙体厚度W对水力停留时间和捕获区域宽度的影响。多元回归分析得到水力停留时间的二次方程模型,方差分析结果显示P0.0001,表明方程模型的显著性很高,拟合度好。其中,最显著的影响因子是PRB的墙体厚度。一定范围内捕获区域宽度随着log K的增加而变小,超过某一值时,并不变化。污染源与PRB距离越近,所需捕获区域宽度越小,墙体的厚度越大;距离越远,所需捕获区域宽度越大,污染范围越广,不利于污染物的治理与控制。设计PRB应用时,需平衡各因素之间的关系,兼顾效率与效益,同时注意安全因子的量化。     

废弃印刷电路板上电子元器件拆卸新工艺及其机理

为了明确利用热空气模拟工业余热作为热源和脉动喷吹动力源拆卸废弃印刷电路板上电子元器件的拆卸机制,分析了废弃印刷电路板脉动喷吹性质,设计并建立了废弃印刷电路板拆卸实验室小试系统,利用Fluent数值模拟软件对拆卸过程中废弃印刷电路板自动拆卸设备内部温度场进行了详细考察,在此基础上,对实验结果进行验证。结果表明,短重边最佳喷吹条件(0.14 MPa,10 mm)下,振动角度为75°;短轻边最佳喷吹条件(0.12 MPa,10 mm)下,振动角度为76°;下进气条件(温度场更均匀,焊料面平均受热温度为198.81℃)更利于废弃印刷电路板上电子元器件的拆卸;采用下进气方式、当预热温度120℃、通气温度为260℃、设备内部达195℃继续通气(拆卸时间)1 min、短重边脉动喷吹压力0.14 MPa、短重边喷吹距离10 mm、短轻边脉动喷吹压力0.12 MPa、短轻边喷吹距离10 mm时,元器件拆卸率为95.1%,且元器件外观完好。本研究明确了废弃印刷电路板拆卸过程中的受热与受力机制,实现了废弃印刷电路板上电子元器件的高效拆卸,为此工艺大规模、工业化生产的实现奠定了理论基础。     

小氮肥厂噪声的治理

随着小氮肥工业的发展,噪声污染问题愈来愈引起人们的关切和重视.我厂系5000吨规模的小氮肥厂,现将我们治理噪声、保护环境的做法做一简要介绍. 一、我厂噪声的分布及治理前的污染情况石家庄地区环办曾对我厂生产区噪声进行了两次测定,使用江西红声器材厂生产的NDZ型精密声级计倍频程滤波器.治理前的主要噪声源情况见图一和表一,所列声压级均指A网络.     

滤袋数目对翼形上进风袋式除尘器内流场影响的数值模拟研究

针对实际运行过程中,袋式除尘器滤袋使用寿命短,压力损失过大的问题,本文以翼形上进风袋式除尘器为研究对象,采用CFD(computational fluid dynamics)技术模拟分析不同滤袋数(分别为92、88、84、80、76和72)时袋式除尘器内气流分布和压力损失规律。主要考察了流量分配系数、最大流量不均幅值、气流迹线、滤袋表面速度分布与压降等指标。结果表明,滤袋数为76个时,气流分布最为均匀,各滤袋负载均衡;相同过滤速度下,装置的压降随滤袋数目的增加而上升,即压降大小顺序为9288847672;与72个滤袋相比,76个滤袋的可用过滤面积更大。综合考虑,袋式除尘器的最优滤袋数目为76个。模拟结果为袋式除尘器的设计和优化提供了依据。     

小城市的交通噪声污染及控制

一、引言随着工业和交通运输的发展,城市道路交通噪声(简称交通噪声)日趋严重。交通噪声已是现代城市中最主要的噪声源。七十年代以来,在交通噪声预报理论和车流的计算机模拟的研究上取得不少进展。但是,这些研究大多针对发达的大中城市,对于小城市交通噪声的研究很少涉及。如我国1979年开始对城市交通噪声进行调查,但只限于大城市。截止1989年底,我国共设市450个,其中县级市262个,占百分之五十八,且大多是近几年设置的。在改革开放、搞活经济的方针指引下,这些城市的     

挥发性污染物苯在水气界面耦合扩散的浓度分布

为研究苯水体泄漏后水气污染的浓度时空分布，利用挥发性污染物水气耦合扩散模型进行预测计算，预测结果与水槽实验相结合，准确地描述了苯在水气界面耦合扩散的浓度分布规律：沿水流方向（x轴）浓度随时间向前推移，距离投放点越远，浓度峰值越小，出现时刻越晚；沿水流深度方向（y轴）浓度分布关于投放点z=0.20 m纵断面对称，在水气界面和空间变化界面（水槽边缘）浓度出现极小值，随着挥发量的增加，浓度峰值出现的位置由水中推移至大气中；沿水流宽度方向（z轴）浓度由投放点向两侧推移。分析了亨利常数、水流速度及风速对苯耦合扩散浓度分布的影响。     

室外大型空气压缩机的噪声治理技术

某室外安装的大型空气压缩机对环境造成了严重噪声污染,离机器2m远处噪声高达114 5dB(A)。在不允许停机的情况下,充分利用现场条件,采取了为空气压缩机加隔声罩、进气口滤清器加消声百页和管道作隔声包扎等综合治理措施,相应测点噪声已降至88 7dB(A),厂界噪声降至机器安装前背景值。室外机器的噪声控制方法与室内机器有许多不同,分析了这些差异并重点介绍了所设计的隔声罩在声学、通风、耐气候性和结构等方面的设计要点。     

Energy Choices and Public Policy

The subject of energy choices and public policy is one that has interested me at a professional level. The outlook for energy supply for Americans is uncertain. Will the OPEC crank the per barrel price of world oil up again this fall by three or four dollars? We don’t know. Will the cost of finding and developing new domestic oil reserves continue to rise, and will the domestic production continue to fall as it has been doing since 1970? We don’t know. Would regulating the price of old oil and natural gas entering into interstate commerce bring forth significantly increased supplies? We don’t know. The chances for reducing oil consumption—or at least checking the rate of increase—are equally uncertain. Will still higher prices, brought on by whatever means, cause people and industries to use less oil? We don’t know. Will demand shift away from oil and natural gas to cheaper, more plentiful energy sources? We don’t know. Will penalties, taxes, or exhortations get the motor vehicle industry to produce more gasoline efficient cars and trucks? We don’t know. We may not even get a chance to try. Will new, less energy intensive lifestyles take over? We don’t know.     

Development of a microscale emission factor model for particulate matter for predicting real-time motor vehicle emissions

The U.S. Environmental Protection Agency's National Exposure Research Laboratory is pursuing a project to improve the methodology for modeling human exposure to motor vehicle emissions. The overall project goal is to develop improved methods for modeling the source through the air pathway to human exposure in significant exposure microenvironments. Current particulate matter (PM) emission models, particle emission factor model (used in the United States, except California) and motor vehicle emission factor model (used in California only), are suitable only for county-scale modeling and emission inventories. There is a need to develop a site-specific real-time emission factor model for PM emissions to support human exposure studies near roadways. A microscale emission factor model for predicting site-specific real-time motor vehicle PM (MicroFacPM) emissions for total suspended PM, PM less than 10 microm aerodynamic diameter, and PM less than 2.5 microm aerodynamic diameter has been developed. The algorithm used to calculate emission factors in MicroFacPM is disaggregated, and emission factors are calculated from a real-time fleet, rather than from a fleet-wide average estimated by a vehicle-miles-traveled weighting of the emission factors for different vehicle classes. MicroFacPM requires input information necessary to characterize the site-specific real-time fleet being modeled. Other variables required include average vehicle speed, time and day of the year, ambient temperature, and relative humidity.     

Source apportionment of PM2.5 and PM10 aerosols in Brisbane (Australia) by receptor modelling

Aerosol samples for PM_2.5 and PM₁₀ (particulate matter with aerodynamic diameters less than 2.5 and 10 μm, respectively) were collected from 1993 to 1995 at five sites in Brisbane, a subtropical coastal city in Australia. This paper investigates the contributions of emission sources to PM_2.5 and PM₁₀ aerosol mass in Brisbane. Source apportionment results derived from the chemical mass balance (CMB), target transformation factor analysis (TTFA) and multiple linear regression (MLR) methods agree well with each other. The contributions from emission sources exhibit large variations in particle size with temporal and spatial differences. On average, the major contributors of PM₁₀ aerosol mass in Brisbane include: soil/road side dusts (25% by mass), motor vehicle exhausts (13%, not including the secondary products), sea salt (12%), Ca-rich and Ti-rich compounds (11%, from cement works and mineral processing industries), biomass burning (7%), and elemental carbon and secondary products contribute to around 15% of the aerosol mass on average. The major sources of PM_2.5 aerosols at the Griffith University (GU) site (a suburban site surrounded by forest area) are: elemental carbon (24% by mass), secondary organics (21%), biomass burning (15%) and secondary sulphate (14%). Most of the secondary products are related to motor vehicle exhausts, so, although motor vehicle exhausts contribute directly to only 6% of the PM_2.5 aerosol mass, their total contribution (including their secondary products) could be substantial. This pattern of source contribution is similar to the results for Rozelle (Sydney) among the major Australian studies, and is less in contributions from industrial and motor vehicular exhausts than the other cities. An attempt was made to estimate the contribution of rural dust and road side dust. The results show that road side dusts could contribute more than half of the crustal matter. More than 80% of the contribution of vehicle exhausts arises from diesel-fuelled trucks/buses. Biomass burning, large contributions of crustal matter, and/or local contributing sources under calm weather conditions, are often the cause of the high PM₁₀ episodes at the GU site in Brisbane.     

The Development of a Sampling System for Determining Odor Emission Rates from Areal Surfaces: Part I. Aerodynamic Performance

Abstract

An improved portable odor sampling system (OSS) of the wind tunnel type was designed to determine odor emissions from areal sources. The aerodynamics of the odor emission hood was observed using a number of smoke tests and dry ice tests. The velocity profiles were also measured horizontally and vertically in the hood by an anemometer. Modifications in the form of an extension inlet duct, flat vanes, and a baffle were necessary to achieve repeatable, uniform, and steady velocity profiles inside the hood. The optimum velocity for use of the OSS was found to be 0.33 m/s, based upon the aerodynamic performance of the OSS and the sensitivity of the anemometer at a lower velocity.     

Characterization of ambient fine particles in the northwestern area and Anchorage, Alaska

Ambient PM2.5 (particulate matter less than 2.5 microm in aerodynamic diameter) in the northwestern United States and Alaska is dominated by carbonaceous compounds associated with wood burning and transportation sources. PM2.5 source characterization studies analyzing recent PM2.5 speciation data have not been previously reported for these areas. In this study, ambient PM2.5 speciation samples collected at two monitoring sites located in the northwestern area, Olympic Peninsula, WA, and Portland, OR, and one monitoring site located in Anchorage, AK, were characterized through source apportionments. Gasoline vehicle, secondary sulfate, and wood smoke were the largest sources of PM2.5 collected at the Anchorage, Olympic, and Portland monitoring sites, respectively. Secondary sulfates showed an April peak at Anchorage and a November peak at Portland that are likely related to the increased photochemical reaction and long-range transport in Anchorage and meteorological stagnation in Portland. Secondary nitrate at the Olympic site showed a weak summer high peak that could be caused by seasonal tourism in the national park. Backward trajectories suggested that the elevated aged sea salt concentrations at the Portland monitoring site could be regional transport of sea salt that passed through other contaminated air sheds along the coast. Oil combustion emissions that might originate from ships and ferries were observed at the Olympic monitoring site.     

Methods of characterizing the distribution of exhaust emissions from light-duty, gasoline-powered motor vehicles in the U.S. fleet

Mobile sources significantly contribute to ambient concentrations of airborne particulate matter (PM). Source apportionment studies for PM10 (PM < or = 10 microm in aerodynamic diameter) and PM2.5 (PM < or = 2.5 microm in aerodynamic diameter) indicate that mobile sources can be responsible for over half of the ambient PM measured in an urban area. Recent source apportionment studies attempted to differentiate between contributions from gasoline and diesel motor vehicle combustion. Several source apportionment studies conducted in the United States suggested that gasoline combustion from mobile sources contributed more to ambient PM than diesel combustion. However, existing emission inventories for the United States indicated that diesels contribute more than gasoline vehicles to ambient PM concentrations. A comprehensive testing program was initiated in the Kansas City metropolitan area to measure PM emissions in the light-duty, gasoline-powered, on-road mobile source fleet to provide data for PM inventory and emissions modeling. The vehicle recruitment design produced a sample that could represent the regional fleet, and by extension, the national fleet. All vehicles were recruited from a stratified sample on the basis of vehicle class (car, truck) and model-year group. The pool of available vehicles was drawn primarily from a sample of vehicle owners designed to represent the selected demographic and geographic characteristics of the Kansas City population. Emissions testing utilized a portable, light-duty chassis dynamometer with vehicles tested using the LA-92 driving cycle, on-board emissions measurement systems, and remote sensing devices. Particulate mass emissions were the focus of the study, with continuous and integrated samples collected. In addition, sample analyses included criteria gases (carbon monoxide, carbon dioxide, nitric oxide/nitrogen dioxide, hydrocarbons), air toxics (speciated volatile organic compounds), and PM constituents (elemental/organic carbon, metals, semi-volatile organic compounds). Results indicated that PM emissions from the in-use fleet varied by up to 3 orders of magnitude, with emissions generally increasing for older model-year vehicles. The study also identified a strong influence of ambient temperature on vehicle PM mass emissions, with rates increasing with decreasing temperatures.     

Characterization, sources, and potential risk assessment of PAHs in surface sediments from nearshore and farther shore zones of the Yangtze estuary, China

The assessment of polycyclic aromatic hydrocarbons (PAHs) contamination in surface sediments from the Yangtze estuary which is a representative area affected by anthropogenic activity (rapid industrialization, high-population density, and construction of dams upstream) in the world was systematically conducted. Fifty-one samples were analyzed by high-performance liquid chromatography (HPLC). The ??PAHs in all sediments varied from 76.9 to 2,936.8?ng?g^?1. Compared with other estuaries in the world, the PAH levels in the Yangtze estuary are low to moderate. Phenanthrene, acenaphthylene, fluoranthene, and pyrene were relatively abundant. The ??PAH levels and composition varied obviously in different estuarine zones due to different sources. The highest ??PAHs concentration was observed in the nearshore of Chongming Island. The PAH composition showed that four to six ring PAHs were mainly found in the nearshore areas, while two to three ring PAHs were in the farther shore zones. The PAHs in the Yangtze estuary were derived primarily from combustion sources. A mixture of petroleum combustion and biomass combustion mainly from coal combustion and vehicle emission was the main source of PAHs from the nearshore areas, while the spill, volatilization, or combustion of petroleum from shipping process and shoreside discharge were important for PAHs in the farther shore areas. The result of potential ecotoxicological risk assessment based on sediment quality guidelines indicated low PAH ecological risk in the Yangtze estuary. The study could provide foundation for the protection of water quality of the Yangtze estuary by inducing main sources input.     

First assessment of the PM<Subscript>10</Subscript> and PM<Subscript>2.5</Subscript> particulate level in the ambient air of belgrade city

INTENTION, GOAL, SCOPE, BACKGROUND: As the strong negative health effect of exposure to the inhalable particulate matter PM10 in the urban environment has been confirmed, the study of the mass concentrations, physico-chemical characteristics, sources, as well as spatial and temporal variation of atmospheric aerosol particles becomes very important. OBJECTIVE: This work is a pilot study to assess the concentration level of ambient suspended particulate matter, with an aerodynamic diameter of less than 10 microm, in the Belgrade central urban area. Average daily concentrations of PM10 and PM2.5 have been measured at three representative points in the city between June 2002 and December 2002. The influence of meteorological parameters on PM10 and PM2.5 concentrations was analyzed, and possible pollution sources were identified. METHODS: Suspended particles were collected on Pure Teflon filters by using a Mini-Vol low-volume air sampler (Airmetrics Co., Inc.; 5 l min(-1) flow rate). Particle mass was determined gravimetrically after 48 h of conditioning in a desiccator, in a Class 100 clean room at the temperature T = 20 degrees C and at about 50% constant relative humidity (RH). RESULTS AND DISCUSSION: Analysis of the PM10 data indicated a marked difference between season without heating--(summer; mean value 56 microg m(-3)) and heating season--(winter; mean value 96 microg m3); 62% of samples exceeded the level of 50 microg m(-3). The impact of meteorological factors on PM concentrations was not immediately apparent, but there was a significant negative correlation with the wind speed. CONCLUSIONS: The PM10 and PM2.5 mass concentrations in the Belgrade urban area had high average values (77 microg m(-3) and 61 microg m(-3)) in comparison with other European cities. The main sources of particulate matter were traffic emission, road dust resuspension, and individual heating emissions. When the air masses are coming from the SW direction, the contribution from the Obrenovac power plants is evident. During days of exceptionally severe pollution, in both summer and winter periods, high production of secondary aerosols occurred, as can be seen from an increase in PM2.5 in respect to PM10 mass concentration. RECOMMENDATION AND OUTLOOK: The results obtained gave us the first impression of the concentration level of particulate matter, with an aerodynamic diameter of less than 10 microm, in the Belgrade ambient air. Due to measured high PM mass concentrations, it is obvious that it would be very difficult to meet the EU standards (EEC 1999) by 2010. It is necessary to continue with PM10 and PM2.5 sampling; and after comprehensive analysis which includes the results of chemical and physical characterization of particles, we will be able to recommend effective control measures in order to improve air quality in Belgrade.