AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
A New Oxidation Flow Tube for Measuring Secondary Aerosol of Rapidly Changing Emission Sources
PAULI SIMONEN, Erkka Saukko, Panu Karjalainen, Miikka Dal Maso, Topi Rönkkö, Jorma Keskinen, Tampere University of Technology
Abstract Number: 666 Working Group: Aerosol Chemistry
Abstract Both diesel and gasoline engines emit gaseous compounds that may form secondary aerosol mass through atmospheric oxidation. The formation of secondary aerosol mass from engine exhaust is often studied using large smog chambers by injecting exhaust to the chamber and oxidizing the sample thereafter. This kind of measurement does not give information on how different driving conditions affect the level of secondary aerosol mass, because the sample is either a mixture of exhaust from different driving conditions or exhaust of an idling engine.
Oxidation flow tubes afford faster oxidation, shorter residence time and thus a faster response time than smog chambers. A new oxidation flow tube, TSAR (TUT Secondary Aerosol Reactor), was designed at Tampere University of Technology to measure the potential secondary aerosol mass of engine exhaust. The laminar flow and short residence time enables the measurement of secondary aerosol mass of engine exhaust even in transient driving conditions.
The working principle of TSAR is similar to the PAM chamber. The flow tube is a quartz glass cylinder and there are two UV lamps outside the cylinder. The UV lamps emit only 254 nm radiation, so the lamps do not produce ozone. Ozone is mixed to the sample before exposure to the UV lamps. Based on CO2 residence time distributions, the flow in TSAR is nearly laminar, and losses of 10-100 nm particles are negligible. The oxidant exposure can be controlled by humidity and the amount of ozone injected to the flow tube. The maximum exposure is equivalent to the oxidation that takes place in the atmosphere in approximately one week. Dynamometer experiments showed that TSAR can be applied to differentiate between different driving conditions during a standardized 30-minute driving cycle.