Dynamic field measurements of submicron particles from diesel engines

We present new tools and a complete setup with which the submicron particle s, emitted from combustion processes, can he measured and classified accord ing to their chemical nature even in the field. Diesel engines are the pred ominant source of these particles in the industrialized countries. The setu p comprises an exhaust conditioning part including means for precipitation of the coarse particle fraction, dilution, and removal of volatile material . The submicron particles are detected with three different sensors: one fo r particle number concentration (condensation particle counter, CPC), one f or the particle "Fuchs"-surface (diffusion charger, DC), and one that respo nds specifically to the carbonaceous particles (photoelectric aerosol senso r, PAS). These sensors possess a short response time so that transients suc h as those occurring in the free acceleration mode may be observed as well. Experiments on a conventional engine test bench demonstrate the tools. The test results are highly reassuring. Correct handling of the volatile fract ion is essential to avoid severe artifacts from gas to particle reactions p articularly in exhaust from engines equipped with particle traps.