Aerogel Based Diesel Particulate Filters

The goal of this project was to study the effectiveness of silica aerogels for use in diesel particulate filters (DPF’s). DPFs are implemented on all modern diesel engines to reduce the amount of harmful particulate matter that is released into the air, which is known to cause smog in large cities and lung cancer. Silica aerogels have a very low thermal conductivity and a unique microstructure which makes them attractive in filter applications. Current ceramic based filters can require costly regeneration cycles to clean the filter, out of vehicle cleaning, and oftentimes have long term reliability issues. Aerogel based filters may be able to address some of these issues. To test if they may work for making a better particulate filter, silica aerogel test samples were exposed to the 600℃ regeneration temperatures found in modern diesel emission systems. Initial testing of large monolithic aerogel samples demonstrated that they can capture soot particles but only on the surface. As a result, 1mm aerogel granules were instead chosen to be used as the filter media because they maximized the surface area upon which soot could be captured. The granule’s flow characteristics were lab tested prior to prototype filter design and were modeled using computational fluid dynamics (CFD). Using the CFD results, a prototype aerogel filter 4” in diameter and 2” long was constructed for testing. The prototype was tested on a diesel truck and the granules captured large amounts of soot. It was determined that aerogel filters capture similar quantities of soot per volume of filter media as compared to existing cordierite filters. Design of precision test equipment to create and monitor a precise combination of air and soot particles is the next step to more accurately determine the exact effectiveness of aerogel filters.