In the foreseeable future, legal regulations will require accurate measurement of the number of particles in motor exhaust emissions.
Motor exhaust can contain both condensates (sulfates, water, HC) and solid particles. The number of condensates particles may lie as much as two to three orders of magnitude above the number of solid particles.
In order to generate meaningful particle number measurements, a way must be found to reliably avoid formation of condensate particles, particularly the so-called nucleation particles (≤50 nm).
Here we present a measuring system and characterize the effects of the exhaust gas recirculation rate, the rail pressure and the fuel injection time. Particularly, we show that a full-load preconditioning leads to elimination of condensate particles and to reproducible measurements of solid particle numbers.