Soot particle size and number density measurements in a direct injection diesel engine using light scattering, radiation, and extinction

In-cylinder soot particle size and number density have been measured in a single cylinder, direct injection diesel engine using principles of light scattering, extinction, and radiation. The measurements were made in a small volume approximately 1 mm in diameter and 4.2 mm long near the head over the bowl region. Two different measurement techniques were employed simultaneously and compared. The first method, radiation/scattering, involved measuring radiation from the soot along a line of sight and light scattering from a beam traversing the radiation volume. The second method used light scattering from the same measurement volume and extinction of the incident and returning light. Particulate and exhaust emission measurements were made to compliment the in-cylinder results.; The results showed an assumed mono-disperse peak soot particle size in the range of 35-55 nm. Soot sizes were found to change rapidly in the measurement volume with particle sizes near 10-15 nm early in the cycle increasing to the peak and abruptly returning to sizes less than 25 nm near the end of combustion. Peak soot volume fraction and diameter were found to increase slightly with increased equivalence ratio. A combined change of decreased intake air pressure and retarded timing slightly decreased peak soot volume fraction and diameter in the in-cylinder measurements but increased exhaust particulates by 2.5 times. The soot cloud was found to be dense and thick. Peak soot volume fraction varied from 3-7 {dollar}times{dollar} 10{dollar}sp{lcub}-5{rcub}{dollar} for the radiation/scattering method and from 4-11 {dollar}times{dollar} 10{dollar}sp{lcub}-5{rcub}{dollar} for the scattering extinction method. The soot was estimated to fill approximately half of the distance from the piston to the head or near 1 cm during the peak soot concentration portion of the cycle.