Opacity and Photoacoustic Measurements of Diesel Particle Mass Emissions

We have compared the capabilities of two optical instruments -- a conventional opacity meter and a photoacoustic device developed in our laboratory -- as tools for measurement of diesel particulate emissions. The devices were tested using emissions from several 5.7 ℓ engines operated at various steady-state conditions of speed and load and also over the Federal Test Procedure driving cycle. The photoacoustic instrument is about 10 times more sensitive than the opacity meter. Further, unlike the opacity meter, its calibration to give mass concentration is independent of particle size variations.