Methods of Measuring Particulate Matter Emissions

According to the definition of particles, testing them requires dilution of the exhaust gas in the dilution tunnel at full or partial flow. Additional considerations to be taken into account when measuring are the degree of dilution, the mass of the filter before and after the measurement, the air humidity and the sample collection time. Tests of particle mass are therefore carried out in several stages; it is a long-term process, requiring that the filters be kept for 8 h in air at constant humidity and temperature, both before and after the measurement. This means that the results cannot be obtained directly during engine operation. Thus, the mass of particles collected on the measuring filter is an average value resulting from the collection time of the exhaust gas sample. This method is most commonly used to determine the mass of particulate matter at a certain time, e.g. for regular, repetitive operational conditions of the engine. The mass method for determining the mass of particulate matter does not guarantee obtaining data on the emission rate under variable conditions, e.g. while increasing the engine load; it is possible, however, to obtain the total mass of particles in these conditions over the selected time interval.