| Despite the great advances in engineering, high pollution levels remain a strong environmental concern. Two of the most notable contributors include chemical and petroleum processing plants and automobiles. In this document, the designs of two new reactors which exploit a common thermal dispersion mechanism are presented as a means of efficiently reducing pollution from these sources.; Recent research has demonstrated the superiority of reverse-flow catalytic oxidation reactors for the combustion of volatile organic compounds in gaseous industrial effluents, yet widespread industrial use is limited because of its tendency towards thermal runaway. A novel reactor design is discussed here which has metal rods placed axially into the bed in an optimal configuration, which induces an enhanced transient Taylor-Aris thermal diffusivity and alleviates runaway. Analytical design correlations are derived for the optimal insert size and spacing as well as the key operating parameter, the reversal time, for arbitrary reactions and flow conditions using asymptotic expansion and scaling theories.; The catalytic converter used today is cold and ineffective during the first few minutes after a car is started. An effective redesign is presented here which shortens this transient startup period and hence drastically reduces pollution emissions. This new design consists of a bypass stream which contains an electric preheater and a cheap preigniter. During startup, only a small portion of exhaust gas travels through the bypass allowing the preheater to utilize a very low power input yet yield a rapid and desired leading-edge ignition in the preigniter. To facilitate the design, a theoretical model has been developed to predict the ignition time for any catalytic converter design under transient startup conditions. Experiments are performed on a 1986 Honda Civic to qualitatively verify the advantages of the new design.; The Lyapunov-Schmidt reduction technique was recently presented as a simple way to calculate solutal and thermal dispersion coefficients. This theory is extended here to compute higher order corrections to the effective dispersivity and show their asymptotic evolution at large times, which may be extremely important in the design of microscale devices. |
