Engine Intake Throttling for Active Regeneration of Diesel Particle Filters

Abstract

<div class="htmlview paragraph">By means of catalysts, either coatings or fuel-borne, the temperature level for triggering the combustion of soot stored in particulate traps can be lowered from 600°C to 300°C, in case of CRT even to 250°C; but even that may fail, if in dense traffic application of a city-bus only 150 - 200°C are attained - similar situations of low load duty cycles exist in most other applications too. Mere passive regeneration may then not be sufficient, active support is needed.</div> <div class="htmlview paragraph">This paper presents an “active” method applicable to any Diesel engine to increase the exhaust temperature whenever required: load of Diesel engines is controlled by the fuel flow only; consequently, excess of air above stochiometric requirement is increasing from λ = 1.5 to λ = 8 with decreasing load, which is in fact the principal cause of the low temperature at light loads. By throttling the air flow simultaneously with the fuel flow, λ is reduced leading to an increased temperature of the exhaust gas, which can be as high as 300 Centigrade.</div> <div class="htmlview paragraph">The paper reports an investigation of intake air-flow throttling as an active tool to increase the exhaust temperature whenever needed for regeneration of a particulate filter by means of a computational simulation as well as an experimental verification concluding that throttling downstream of the turbocharger compressor will be the most advisable method.</div> <div class="htmlview paragraph">Influence on fuel economy remains negligible because of the very short operation time.</div> <div class="htmlview paragraph">Fast responding actuators are required to take care of rapid load changes.</div> <div class="htmlview paragraph">Operation strategy can be electronically based on engine map data, but also more simple solutions are possible which are well suited to retrofit engines of older pure mechanical design.</div> <div class="htmlview paragraph">It is recommended to use air intake throttling in combination with catalytic coating of particle filters or fuel borne catalysts to cover a very wide range of engine applications and operation conditions.</div>