Light scattering technique for estimating soot mass loading in diesel particulate filters

Abstract

The real-time estimation of soot mass loading on diesel particulate filters (DPF) is essential to assure perfect and fuel efficient regeneration. Computer models based on the pressure drop across the DPF are usually installed in the engine control unit to estimate the soot mass loading during vehicle driving, but this approach is still subject to uncertainty about the lack of resources available. The aim of this study is to develop a portable instrument that can make real-time measurements of soot mass loading under transient mode for calibrating the models. The instrument is based on the light scattering technique: A laser beam illuminates diesel particles in a small exhaust sample and the intensity of scattered light from soot particles is reduced to soot mass concentration using calibration data obtained under steady engine operating conditions. It is demonstrated that the prototype instrument can measure the temporal variations of cumulative soot mass and filtration efficiency of a diesel particulate filter under a transient mode, and that it has a minimum detectable concentration of 5 μg/m3, which is low enough to detect the particle breakthrough in the DPF. The proposed technique has potential to be applied for on-board diagnostics if the device is downsized.