Measurements of particulate mass concentration using atapered-element oscillating microbalance and a flameionization detector

Abstract

Measurement of particulate mass concentration in the exhaust of automotive engines by means of the filter sampling method prescribed by the USA's Environmental Protection Agency (EPA) is tedious, costly, time consuming and labour intensive. This paper presents a new approach, which is capable of measuring real-time particulate mass emissions in the exhaust of a diesel engine by using a tapered-element oscillating microbalance (TEOM) and a fast-response flame ionization detector (FID). The measuring principle rests on the fact that, by operating the TEOM at 50 °C, water interference is minimized, albeit at the expense of reducing the hydrocarbon content condensed on the particles. This is corrected by a method that consists of a measurement of hydrocarbon gas concentration, used with an empirical correction factor to recover what the filter sampling method would produce. The time resolution for the measurement using this new method is limited by the sampling window of the TEOM which is 0.42 s, though the response of the FID offers a time resolution of milliseconds. Results show that the mass concentration of particulate matter measured by TEOM and FID is well correlated to that based on the conventional EPA filter sampling method. Keywords: particulate mass concentration, tapered-element oscillating microbalance, flame ionization detector, diesel exhaust particulate measurement, correlation to EPA (USA) standard