Method of regenerating particle filter for an IC engine exhaust system has soot cyclically burnt by post-injected fuel allowing for backpressure-related excess consumption

摘要

Typically, on diesel engines (12), or those running on weak petrol mixture, a particle filter (16), installed in the exhaust line (14) requires periodic regeneration to clear accumulated soot. Soot burning requires a temperature of about 550 deg.C. So the normal exhaust gas temperature of 150-250 deg.C is raised e.g. by directly (in post-combustion) or indirectly burning additional fuel when the pressure drops across the filter, measured by a differential sensor, reaches a preset threshold value. Excess consumption due to the filter arises partly from this, partly from reduced efficiency due to increased exhaust back-pressure. It is shown that excess consumption is minimized when these two components attain equality. A certain minimum mass of soot must accumulate to allow complete burn-off; however, there is a maximum above which burning will damage the filter. The time to reach a suitable point within this range is dependent on engine operational factors, loading, etc. The quantity of fuel assigned to each burn-off is kept constant, and, ideally, the duration of each cycle should be such that excess fuel consumption due to back-pressure effects, as assessed eg. by throttle opening and vehicle speed sensors, equates to this quantity.