[题名] 新型 OFR 的设计和表征：颗粒形成加速器 ( PFA )

[作者] Ningjin Xu, Don R. Collins

[摘要] 在我们的研究中，我们设计了一个新的全氟聚合物反应器，名为粒子形成加速器（PFA），并在实验室和环境空气中对其进行了表征。我们进行了一系列模拟和实验，以表征以下内容：（1）使用计算流体动力学（CFD）模拟来表征反应器内的流动特性；（2）反应器中的紫外线强度分布以及紫外线强度、臭氧浓度和相对湿度（RH）对等效羟基暴露（OHexp）的影响；（3）气体和颗粒的传输效率；（4）使用计算模拟和实验验证来表征气体和颗粒的停留时间分布（RTD）；（5）α-蒎烯和间二甲苯氧化的二次有机气溶胶（SOA）的生产产量；（6）种子颗粒对生成的SA浓度的影响；（7）从美国加利福尼亚州里弗赛德市的环境空气中产生的SA。我们将反应器的响应和特性与一个烟雾室（加州理工学院）、其他氧化流动反应器（多伦多光氧化管（TPOT）、加州理工学院光氧化流动管（CPOT）以及 Potential Aerosol Mass 反应器的石英和铝版本（PAMs））进行了比较。

PFA具有以下优点：（1）由于全氟聚合物材料的使用，该反应器对各种化学物质具有良好的惰性，并且对所有溶剂具有极高的抗性；（2）它具有适中的气体透过率，因此适合在微通道中长时间培养细胞；（3）与PDMS相比，它不吸收小分子，很少将生物分子吸附到通道壁上，并且没有残余分子从材料本体中浸出到通道中的溶液中。

我们的研究表明： (1) OHexp可以变化范围与其他的，(2)粒子传输效率超过75 %大小从50到200海里，在最小化静电特氟乙烯表面，(3)二氧化碳和硫2的渗透效率为0.90 ± 0.02和0.76 ± 0.04，后者与估计LVOCs，(4)近层流剖面预计基于CFD模拟和RTD 25实验结果，(5)二甲苯SOA和α-pinene SOA产量为0.22和0.37，分别在约3×1011摩尔。厘米−3s哦暴露，(6)种子颗粒与前体气体的质量比对SOA的形成量有显著影响，(7)在测量SA生产在河边采样环境空气时，反应器中形成的SA的质量浓度平均为环境气溶胶的1.8倍。

[关键词]  氧化流反应器、粒子传输、、二氧化碳、粒子形成加速器（PFA）、臭氧浓度

[Title] Design and Characterization of a new OFR: The Particle Formation Accelerator (PFA)

[Author] Ningjin Xu, Don R. Collins

[Abstract] Oxidation flow reactors (OFRs) are frequently used to study the formation and evolution of secondary aerosol (SA)  in the atmosphere and have become valuable tools for improving the accuracy of model simulations and for depicting and  accelerating realistic atmospheric chemistry. Driven by rapid development of OFR techniques and the increasing appreciation  of their wide application, we designed a new all-Teflon reactor, the Particle Formation Accelerator (PFA), and characterized  it in the laboratory and with ambient air. A series of simulations and experiments were performed to characterize: (1) flow  profiles in the reactor using computational fluid dynamics (CFD) simulations, (2) the UV intensity distribution in the reactor  and the influence of it and varying O3 concentration and relative humidity (RH) on the resulting equivalent OH exposure   (OHexp), (3) transmission efficiencies for gases and particles, (4) residence time distributions (RTD) for gases and particles  using both computational simulations and experimental verification, (5) the production yield of secondary organic aerosol  (SOA) from oxidation of α-pinene and m-xylene, (6) the effect of seed particles on resulting SA concentration, and (7) SA  production from ambient air in Riverside, CA, U.S. The reactor response and characteristics are compared with those of a  smog chamber (Caltech) and of other oxidation flow reactors (the Toronto Photo-Oxidation Tube (TPOT), the Caltech Photooxidation Flow Tube (CPOT), and quartz and aluminum versions of Potential Aerosol Mass reactors (PAMs)).

Our studies show that: (1) OHexp can be varied over a range comparable to that of other OFRs, (2) particle transmission  efficiency is over 75 % in the size range from 50 to 200 nm, after minimizing static charge on the Teflon surfaces, (3) the  penetration efficiencies of CO2 and SO2 are 0.90 ± 0.02 and 0.76 ± 0.04, respectively, the latter of which is comparable to  estimates for LVOCs, (4) a near laminar flow profile is expected based on CFD simulations and suggested by the RTD  25 experiment results, (5) m-xylene SOA and α-pinene SOA yields were 0.22 and 0.37, respectively, at about 3 × 1011 molec. cm−3 s OH exposure, (6) the mass ratio of seed particles to precursor gas has a significant effect on the amount of SOA formed,  and (7) during measurements of SA production when sampling ambient air in Riverside, the mass concentration of SA formed  in the reactor was an average of 1.8 times that of the ambient aerosol at the same time.

[Keywords] Oxidation flow reactors (OFRs)、particle transmission 、CO2、the Particle Formation Accelerator (PFA)、O3 concentration