Removal characteristics and distribution of indoor tobacco smoke particles using a room air cleaner

The objective of this study is to analyze the removal characteristics and distribution of indoor air pollutants by a room air cleaner. A pollutant removal effect according to room volume and measurement point was evaluated in an indoor room. A series of filtration efficiency tests were performed on only the electrostatic precipitator of the room air cleaner. The measurements of filter efficiency and pressure drop across the electrostatic precipitator were made using an ASHRAE 52.1-1992 filter test system and an opacity meter to measure the particle concentration upstream and downstream of the test filter. Also the performance of the air cleaner in the room was evaluated by examining tobacco smoke particle concentration. The size distribution of the tobacco smoke particles was 1.27 μm in mass median diameter and a geometric standard deviation of 1.313 μm. The efficiency of the electrostatic filter was measured as 78.6% with dust particles of 1.96 μm in mass median diameter and 1.5m/s face velocity. The tobacco smoke particle concentration as a function of time decayed exponentially. The contaminant removal effect was increased when increasing the effective clean air exchange rate (ηQ/V), which is 0.0780 min^?1 for 51 m³ room and 0.0235 min^?1 for 149 m³ room. This study clearly shows that a room air cleaner with an electrostatic precipitator is effective in removing tobacco smoke particles. The removal characteristics and distribution of indoor air pollutants in other rooms is predicted based on empirical modeling.     

Exhaust Aerosol of a Plasma Enhanced CVD System: II. Electrical Charging and Transport

The microelectronics industry has been concerned about the loss of product yield in its semiconductor wafer processing steps from killer defects caused by the presence and deposition of contaminant particles. Reactant gases used in plasma enhanced chemical vapor deposition (PECVD) can form nanometer sized particles from homogeneous nucleation. Once the particles grow to a few nanometers, they become negatively charged due to the collected ion and electron currents on the particle surface. A gradient of the electron and ion concentration between the sheath and bulk plasma causes an electric field to develop directed to the walls. Contaminant particles can eventually become trapped in electrostatic potential wells due to the higher charge density of positive ions near the powered electrode. The traps fill in the plasma sheath region until some particles are "leaked out" by gas drag forces. Therefore particles formed solely in the plasma volume are theorized to possess a distinct charge level from condensation particles originating within the exhaust line alone. Consequently, plasma properties determine the size and charge distribution of contaminants that exit the reactor and enter the exhaust line. The intended contribution of this research was to (1) develop the capability to monitor charged and uncharged contaminant particle fractions during a thin film deposition cycle and (2) to understand the coupled effect of particle transport and charging in an radio frequency (RF) plasma. Therefore the size distribution and absolute electrical charge were measured in the vacuum exhaust line during a SiO 2 thin film cycle using an integral mobility charge analyzer. Experiments confirm that over 50% of fine particles in the exhaust were neutral. However, a moderately charged coarse fraction was measured between 0.15 and 0.3 w m. The larger particles are hypothesized to be reactor particles gradually released from the potential wells in the plasma sheath. Process variables, including the RF power and the reactor pressure, directly affected the size and charge characteristics measured on particles in the exhaust line. The first paper in the series "Exhaust Aerosol of a Plasma Enhanced CVD System" uses an in-line exhaust sampling system to measure the size distribution of contaminant particles exiting the plasma.     

Exhaust Aerosol of a Plasma Enhanced CVD System: I. Size Distribution Measurements

Understanding the origin and fate of plasma-enhanced chemical vapor deposition (CVD) contaminant particles is a critical issue in semiconductor manufacturing in order to improve thin film deposition on wafer surfaces. Several competing external forces will affect a particle's motion in the plasma field prior to either landing on the wafer or entering the exhaust line. Electrical forces dominate during plasma radio frequency (RF) activation creating regions of potential wells. If trapped, the nucleated particles can continue to grow and gain electron charges until gas or ion drag forces can overcome the potential barrier. Mutual electrostatic repulsion between particles can also cause the traps to "leak" out contaminants into the exhaust line. In this way, contaminants formed solely in the plasma volume are hypothesized to possess a distinctive size and charge distribution independent of condensation particles originating from gas compression by the oil-based rotary pump. For these reasons, a novel experimental aerosol sampling system was designed to continuously monitor submicron particles carried during a thin film deposition cycle without disturbing the internal operation of the plasma. Sampling from the plasma enhanced chemical vapor deposition (PECVD) process exhaust gases using an oil-free mechanical piston pump parallel to the main vacuum line is considered to be an effective alternative to in situ probe measurement. Concentration and size distribution data were continuously measured using a condensation nucleus counter and an optical spectrometer. Results show that the particles in the reactor exhaust line are bimodal or made up of fine and coarse sizes divided near 100 nm. Experimental results show the fine fraction increases in the exhaust line after a certain time interval. This delay is hypothesized to be the initial period the nucleated particles were trapped inside the plasma's potential wells. Once trapped, reactor particles can continue to grow in agreement with free molecular coagulation models. A larger particle will experience greater gas drag to eventually overcome the electrical forces. The delay, or critical transport time, depends upon the reactor pressure and plasma power, which also affect the size of the trapping field. The second paper in the series "Exhaust Aerosol of a Plasma Enhanced CVD System" compares a computational charging model of the plasma sheath with experimental charge distribution measurements of contaminant particles carried through the CVD exhaust.     

Physicochemical Factors Influencing Colloidal Particle Transport in Porous Media

Abstract

The mobilization/immobilization of colloidal-sized particles which have high surface areas per unit mass is an important process occurring in groundwater flow systems. Association of contaminants with mobile colloidal particles may enhance the transport of adsorbed pollutants, or deposition of colloidal particles in porous media may decrease permeability and reduce contaminant transport. The general objective of this work was to elucidate physical and chemical factors affecting colloidal particle (Brownian and non-Brownian) transport in porous media under typical groundwater flow velocities. The most critical chemical factor influencing Brownian particle (0.1 and 1.0 μm) transport in a packed column was found to be pH. The next most critical factor was electrolyte concentration (calcium ion and sodium ion concentration). Gravitational force was found to be an important factor for non-Brownian particle (10 μm) transport. The non-Brownian particle transport was observed to be independent of solution chemistry. Increases in superficial velocity (from 0.9 to 2.7 m/day) resulted in different types of behavior for Brownian and non-Brownian particle transport under different conditions. The Brownian particle throughputs at a superficial velocity of 0.9 m/day were mainly controlled by the surface interaction forces, that is, hydrodynamic action was not important. The difference in Brownian diffusivity between 0.1 and 1.0 μm particles caused opposite results in particle throughputs in all experimental columns regardless of solution chemistries. Particles of 0.1 μm produced the maximum transport in the column filled with the smallest glass beads, while 1.0 μm particles produced the maximum transport in the column packed with the largest glass beads.     

大空间重气泄漏下速度场、浓度场特性分析

在实际的工业场景中，机器设备等障碍物的存在对污染物的扩散及分布有着很重要的影响。考虑了在有障碍物的大空间中，泄漏位置在障碍物两侧的场景。定义了污染源重力作用强度指标、无量纲浓度以及易燃易爆区域占比。用实验验证了计算流体力学（CFD）模型的准确性，进而用CFD计算了不同污染物释放速率时的速度场及浓度场。计算结果表明，随着污染物释放速率的增加，速度场的结构和浓度场的分布形式都发生变化。当无量纲数θ_inlet超过0.0288时，污染源附近会出现新的涡流，而无量纲浓度分布开始出现垂直分层的趋势。当污染源体积释放速率超过2.66667×10^-5 m³/s时易燃易爆区域的大小变得显著，导致潜在的爆炸风险。     

Development of a Versatile Aerosol Generation System for Use in a Large Wind Tunnel

A novel aerosol generation system has been constructed for use in a large wind tunnel for two distinct research projects. One project requires a uniform aerosol concentration over the wind tunnel cross section, while the other project demands a stratified aerosol concentration distribution. The system consists of an array of venturi nozzles, which entrains particulate matter from a moving conveyor belt and disperses it into the tunnel under the force provided by a compressed air source. For the stratified release configuration, only the bottom row of nozzles was used and a confinement sleeve was installed to prevent mixing with clean air; the mixing fans were omitted from this configuration. The uniform release arrangement was tested by gravimetrically measuring particle concentration over the cross section of the tunnel for tunnel speeds of 0.1 and 1.0 m/s; uniformity was achieved within a coefficient of variation of 6.4%. The stratified distribution results show a high concentration near the floor, which diminishes with increased height. Particle size distribution was also determined on filter samples using scanning electron microscopy analysis for the uniform release experiments. No appreciable difference in mass median diameter or geometric standard deviation could be discerned for the various sampling points.     

Preferential attachment of contaminants to filter media in oil

In oil filtration, particles must attach to the filter medium, typically fibres. Attachment is a function of the chemical and physical properties of both the contaminant and the filter medium. Cellulose and synthetic filter media are commonly used in oil filtration. The contaminants include wear metal particles, silica and soot. Because of differences in size and in physical and chemical characteristics, significant differences in contaminant attachment and removal are expected. Experiments were conducted in which filters were challenged with contaminants exhibiting different physical and chemical characteristics. It was found that contaminant shape, roughness and size distribution influence removal. Indirect evidence suggests that chemical interactions also influence removal. The structure of the filter medium mediates these effects.     

Evaluation of downer reactor performance by catalytic ozone decomposition

Radial distribution profiles of ozone concentrations were measured along an 8.50 m high and 0.09 m inside diameter gas/solid co-current down-flow circulating fluidized bed (downer) to characterize the reactor performance. Tests were conducted under a series of operating conditions at room temperature and near atmospheric pressure, with FCC particles as the bed material. Results show that the concentration distribution of the ozone tracer gas correlates well with the flow structure of the downer. There is quite a uniform radial distribution of ozone concentrations in the core region of all tested axial sections in the fully developed region of the downer, except for the near-wall region where there is a sharp decrease in ozone concentration. And there exists a relatively significant non-uniform distribution in the entrance acceleration region of the downer.     

Concentration and Size Distribution of Culturable Airborne Microorganisms in Outdoor Environments in Beijing,China

A one-year (from June 2003 to May 2004) study of airborne microbial concentration and size distribution was conducted systematically at three selected sampling sites in Beijing. Microbial samples were collected in triplicate for 3 min, 3 times per day, for 3 consecutive days of each month using FA-I sampler (imitated Andersen sampler, made by Applied Technical Institute of Liaoyang, China). Results showed that the concentration of total culturable microorganisms ranged from 4.8 × 10 ² colony forming units (CFU)/m ³ to 2.4 × 10 ⁴ CFU/m ³ , with an arithmetic mean of 3.7 × 10 ³ ± 2.1 × 10 ² (standard deviation) CFU/m ³ . As a whole, the percentage of airborne bacteria, accounting for 59.0% of the total culturable microorganisms, was significantly higher than those of airborne fungi (35.2%) and actinomycetes (5.8%). At RCEES (Research Center for Eco-Environmental Sciences—a culture and education area) and XZM (Xizhimen—a main traffic line), significantly higher percentages of airborne bacteria were found as compared to airborne fungi. No significant difference was observed between airborne bacteria and fungi at BBG (Beijing Botanical Garden—a green garden area). The total microbial concentration was significantly higher at RCEES than at XZM and BBG (*P < 0.05), and no significant difference between XZM and BBG was observed (P > 0.05). Total microbial concentrations were higher in summer and autumn, and lower in spring and winter at RCEES and XZM (*P < 0.05). At BBG, higher concentration was observed in summer during the sampling periods (***P < 0.001). The size distribution of airborne bacteria showed a skewed distribution at three sampling sites. The proportion of bacterial particles decreased gradually from Stage 1 ( > 7.0 μm) to Stage 6 (0.65 ～ 1.1 μm), and there was an obvious downtrend on Stage 2 (4.7 ～ 7.0 μm). Bacterial particles were mainly distributed at the first four Stages ( > 2.1 μm), accounting for 78.6% at RCEES, 84.0% at XZM, and 81.5% at BBG. The size distribution pattern of airborne fungi was found with normal logarithmic distribution at three sampling sites. Fungal particles were mainly distributed at Stage 3 (3.0 ～ 6.0 μ m), Stage 4 (2.0 ～ 3.5 μ m) and Stage 5 (1.0 ～ 2.0 μ m), composing 71.6% of the population at RCEES, 74.2% at XZM, and 68.3% at BBG. However, different distribution patterns were found in different dominant fungal genera. Cladosporium, Penicillium, and Aspergillus were present with normal logarithmic distribution, while Alternaria and sterile mycelia were found with skewed distribution. In opposition to the distribution pattern of fungal particles, the actinomycete particles at all sampling sites were primarily collected on Stage 1, Stage 5, and Stage 6, accounting for 61.1% at RCEES, 60.7% at XZM, and 64.8% at BBG.     

CO2管线泄漏扩散小尺度实验研究

CO₂气体综合开发和利用过程中涉及很多安全问题,为了研究CO₂作为典型重质气体从输送管线泄漏后的扩散规律,在综述重气扩散实验的基础上设计了CO₂管线泄漏扩散缩比例实验;通过幂函数拟合得到监测点峰值浓度曲线,并据此确定了生产现场的安全距离;根据危险气体非正常排放模型对实验进行了理论预测,结果与实验值进行了对比。结果表明小风条件下,当以950 m³·h^-1初始流量释放20 min左右的CO₂时,现场安全距离可设为46 m,而当初始流量为6300 m³·h^-1时,现场安全距离为160 m;实验值和理论预测值的偏差最小为-3.0%,最大为28.1%。经分析可知CO₂管线泄漏近源区一定距离内主要靠射流动能扩散,其后范围主要受浓度梯度的影响,危险气体非正常排放模型可较准确地预测近源区的扩散情况;安全距离与泄放流量基本呈指数关系。     

Physical Characterization of Cigarette Smoke Aerosol Generated from a Walton Smoke Machine

Mainstream cigarette smoke generated using a Walton smoking machine and Kentucky 2R1 research cigarettes was studied. Results showed that puff volume and total particulate matter were consistent after the first puff, with average values of 35.6 cm³ and 3.37 mg, respectively. The particle size distribution, measured with a multijet cascade impactor, was not related to butt length or relative humidity (≤95%), but was strongly dependent on the aging time. Based on simple monodisperse coagulation, the mass median aerodynamic diameter was calculated to be 0.45 μm at a dilution ratio of 21.7. Using a technique based on the dimensional change of collected droplet particles at various viewing angles of a scanning electron microscope, the count median diameter was estimated to be 0.22 μm. These values were in good agreement with those reported by others. The results suggest that there is a dilution value critical to the rapid evaporation and final particle size of the cigarette smoke aerosol. Once reaching this value, further dilution has little effect on the final particle size. By using the derived mass concentration and size distribution, the particle density, number concentration, and coagulation coefficient of the cigarette smoke aerosol were estimated to be 1.12 g/cm³, 7.20 × 109 particles/cm³, and 6.64 × 10 ^?10 cm³/s respectively. Solid particles > 1 μm were found in the first few puffs. These were considered to consist of tobacco debris.     

Indoor Sources of Ultrafine and Accumulation Mode Particles: Size Distributions,Size-Resolved Concentrations,and Source Strengths

Ultrafine (< 100 nm) and accumulation mode (0.1–1 μm) particles were monitored in an occupied suburban house at 5-minute intervals for 37 consecutive months between November 21, 1997 and December 31, 2000. Number concentrations for 126 particle sizes from 9.8–947 nm were measured in 259,176 scans. Of 282 separate activities, 18 were chosen for detailed analysis. These included cooking with a gas stove, toasting with electric toasters and toaster ovens, burning candles and incense, and using a gas-powered clothes dryer. Activities leading to increased particle concentrations occurred 17.5% of the time, and accounted for more than half the total concentration of ultrafines and about a quarter of the total accumulation mode particles. The average duration of elevated particle concentrations ranged from 20 minutes to 3 hours. Combustion of natural gas (boiling water, gas clothes dryer) showed number peaks near 10 nm, while the electric toaster and toaster oven had peaks close to 30 nm. More complex cooking (burners plus gas oven) produced peaks in the 35–50 nm range. Burning candles and incense resulted in peaks in the 60-nm range. Finally, outdoor sources peaked at nearly 70 nm, indicating the influence of aging in shifting modes to higher diameters. The highest mean number concentrations were due to complex cooking, producing average number concentrations of 35,000–50,000 cm^{? 3}, compared to 12,000 cm^?3 outdoors and less than 3500 cm^?3 indoors when no sources were observed. A strong contribution of the vented gas-powered clothes dryer was also noted (30,000 cm^{? 3}). Volume concentrations due to these combustion events ranged from < 1 (μm/cm)³ to nearly 100 (μm/cm)³. Source strengths were calculated for three common cooking types (boiling water, deep-frying, oven baking, and broiling) and ranged from 5 × 10 ¹² to 4 × 10 ¹³ particles per cooking event. The detailed concentration and size distribution data collected here may be useful for models of indoor air particle concentrations due to indoor sources and infiltration.     

汽轮机喷嘴内盐析颗粒分布特性

为深入了解汽轮机内盐析颗粒的微观行为,本文以某超临界汽轮机高压级喷嘴为研究对象,应用计算流体力学与群体平衡模型耦合方法,对汽轮机喷嘴内盐析颗粒在流场中的分布进行数值模拟研究,获得了盐析颗粒在喷嘴内的平均粒径、组分数及浓度分布规律。模拟结果表明：在喷嘴入口附近处盐析颗粒粒径仅发生微小变化,沿介质流动方向盐析颗粒不断长大,但在喷嘴出口截面附近处,颗粒长大的幅度又趋于平缓;此外,在盐析颗粒相互作用的影响下,20μm粒径颗粒的组分数分布沿介质流动方向逐渐减小,而80μm和140μm粒径颗粒则与其相反;20μm粒径颗粒在叶片的吸力面处组分数较高,而140μm粒径颗粒在叶片的压力面处组分数较高;盐析颗粒浓度从叶片吸力面到压力面逐渐增大,最终在压力面附近形成高浓度区。     

Soil Clean Up by in-situ Surfactant Flushing. II. Theory of Micellar Solubilization

Abstract

Mathematical models for describing the solubilization of various types of contaminants in micelles of ionic and nonionic surfactants are described. Contaminants which are purely hydrophobic compounds and those which are amphipathic are handled, and electrical effects are described by means of a Debye-Huckel theory approach. It is found that the concentration of contaminant solubilized is a linear function of the total surfactant concentration provided that this is above the critical micelle concentration of the surfactant, in agreement with experimental results.     

Characteristics of secondhand electronic cigarette aerosols from active human use

The electronic cigarette (EC) is a new source of indoor airborne particles. To better understand the impacts of secondhand vaping (SHV) emissions on indoor air quality, real-time measurements of particle size distribution, particle number concentration (PNC), fine particulate matter (PM_2.5), CO₂, CO, and formaldehyde were conducted before, during, and after 10 min EC-use among 13 experienced users in an 80 m³ room. To assess particle transport in the room, multiple sampling locations were set up at 0.8, 1.5, 2.0, and 2.5 m away from the subjects. The arithmetic mean (standard deviation) of background PNC and PM_2.5 concentrations in the room were 6.39 × 10³ (1.58 × 10²) particles/cm³ and 8 (1) μg/m³, respectively. At 0.8 m away from EC users, right after initiation of puffing, the PNC and PM_2.5 concentrations can reach a peak of ～10⁵ particles/cm³ and ～3 × 10³ µg/m³, respectively, and then dropped quickly to background levels within 20 s due to dilution and evaporation. At the 0.8 m sampling location, the mean PNC and PM_2.5 concentrations during puffing were 2.48 × 10⁴ (2.14 × 10⁴) particles/cm³ and 188 (433) µg/m³, respectively. In addition, two modes of SHV particles were observed at about 15 and 85 nm. Moreover, concentrations of SHV particles were negatively correlated with the distances to EC users. At the 1.5 m location, PNC and PM_2.5 levels were 9.91 × 10³ (1.76 × 10³) particles/cm³ and 19 (14) µg/m³, respectively. Large variations of mean PNC levels exhaled per puff were observed both within and between EC users. Data presented in this study can be used for SHV particle exposure assessment.

Copyright © 2017 American Association for Aerosol Research     

Initial Collection Performance of Resin Wool Filters and Estimation of Charge Density

Abstract

A new type of resin wool filter (RWF) that persists the load with oil droplets was developed by Kimura and colleagues. In the present work, the initial collection performances of RWF (A and C) are measured for various particle sizes (0.03, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3 μm) with different charging states at various filtration velocities (0.05, 0.1, 0.15, and 0.3 m/s). As a result, it is shown that the present RWF impregnated with PTBP resin can attain high collection efficiency (99.999% at filtration velocity of 0.05 m/s) with a pressure drop of less than 30 Pa. The charge density is estimated by applying prediction equations of single-fiber collection efficiencies of electret filters with a dipolar charge distribution because no other prediction equation for RWF are available at present. The experimental single-fiber efficiencies for uncharged particles are successfully predicted by assigning a single value of charge density in the prediction equations for dipolar fibers. The estimated charge density on RWF fibers is 2.1 × 10^{? 4} C/m², which is much higher than those of conventional electret filter media. Therefore, RWF studied in the present work is suitable for the application to respirators as well as room air cleaners.     

Experimental Determination of Supermicrometer Particle Fate Subsequent to a Point Release within a Room under Natural and Forced Mixing

The fate of mono-dispersed fluorescein-tagged particles with nominal aerodynamic diameters 3 μ m and 14 μ m has been measured in a room-scale chamber under natural and forced mixing conditions. The mixing time scales were measured as the time to mixing of carbon monoxide tracer gas. In the forced mixing condition, 3-axis ultrasonic anemometry was used to determine the mean and fluctuating velocity for each vector component at 106 locations. Cumulative deposited fluorescein mass at 61 locations on the chamber floor showed size-dependent and mixing-dependent particle dispersion patterns. More uniform deposition was produced under conditions with relatively shorter mixing time scales, and longer particle settling time scales. A unique data set has been generated for the evaluation of particulate contaminant transport models.     

Removal of surface contaminants by cryogenic aerosol jets

Removal of surface contaminants by various cryogenic aerosol jets has been experimentally investigated. Simplified theoretical consideration of their removal mechanism has been also presented based on the impact power of the aerosol jets. Under atmospheric operation, water vapor and carbon dioxide could make their particles independent of their concentrations in the carrier gas while argon and nitrogen could hardly solidify to their own particles. The cryogenic aerosol jets were very effective in removing both submicron particle contaminants and photoresist films on wafers. The rate of the PR film removal strongly depended on the hardness of the film. Molecular organic films could be also removed with the aerosol jets. In general, the removal of the contaminants depends primarily on the physical impact. The removal rate increased with the mass concentration of the aerosol particles, regardless of their nature. The rate also increased with the impact velocity of the jets which was controlled by either the chamber pressure or the distance between the nozzle tip and the contaminant surface. The cryogenic aerosolfree jet was much less effective than the corresponding aerosol jets but had some effectiveness compared to the noncryogenic one. The thermal shock of the film was, therefore, supposed to have a secondary effect on the contaminant removal.     

Soil Clean up by in-situ Surfactant Flushing. VI. Reclamation of Surfactant for Recycle

Abstract

Solvent extraction has been studied for use in reclaiming contaminated surfactant solutions for reuse in soil surfactant flushing in the remediation of hazardous waste sites. Hexane was used as the solvent to extract p-dichlorobenzene (DCB), naphthalene, and biphenyl from 25, 50, and 100 nM sodium dodecylsulfate (SDS) solutions in a continuous countercurrent flow column. The contaminant concentration in the aqueous SDS was followed with time, and the removal was modeled using an unsteady-state model which included diffusion kinetics. The mass transfer time constant was approximately 2 hours. The percent removal of DCB increased with increasing hexane flow rate and decreased with both increasing SDS flow rate and increasing SDS concentration. The concentrations of all three contaminants were reduced by about 90% or better. Extraction of contaminated SDS solutions with hexane appears to be an effective method for cleaning up these surfactant solutions for recycle.     

基于群体平衡的汽轮机动叶表面盐析颗粒分布特性

为深入了解汽轮机动叶内盐析颗粒的微观行为,本文以某超临界汽轮机高压级动叶为研究对象,应用计算流体力学与群体平衡模型耦合方法,对汽轮机动叶内盐析颗粒在流场中的分布进行数值模拟研究,获得了盐析颗粒在动叶内的粒径分布及不同负荷时叶片尾缘处盐析颗粒数量密度分布规律。模拟结果表明：在汽轮机动叶吸力面附近的盐析颗粒粒径较压力面附近盐析颗粒粒径小,且叶根处颗粒粒径小于叶顶处;动叶压力面的颗粒数量密度呈前缘点尾缘点处大、中间段小的分布规律,并且盐析颗粒在叶片上的数量密度分布最大值并不出现在组分数及粒径最大处,而是出现在平均粒径为110~150μm的盐析颗粒沉积位置处;当汽轮机30%负荷运行时,粒径40μm盐析颗粒的数量密度是其在汽轮机额定负荷运行时的1.5倍,而粒径140μm盐析颗粒的数量密度仅为汽轮机额定负荷运行时的80%。