Evaluation of various strategies for continuous regeneration of particulate filters

Exhaust gases of diesel engines may be cleaned of particulates fairly effectively by filtering the gases through various types of beds. Filter regeneration is however, necessary to maintain a clean filter and to keep its flow resistance low. Uninterrupted regeneration may be achieved by burning up the trapped particulates in a continuous manner. Under high engine load conditions, this is attainable by reducing the ignition temperature of the particulates by means of suitable fuel additives, or by means of an appropriate catalytic coating of the relevant filter components. However, under low engine loads, the exhaust gas temperature might be too low and another sensible method has to be employed to continuously ignite the particulates. Apparently, the minimum required exhaust temperature may be achieved over a fairly wide range of engine operation conditions by using several simple-to-employ means. These include inlet throttling (IAT), inlet preheating (IAP), exhaust gas recirculation (EGR), exhaust throttling (EGT), and the like. We ask to what extent these straightforward means can affect the exhaust gas temperature at the relevant range of engine speeds and loads. Prior to performing extensive and expensive experimental research-or investing in a reliable numerical model to simulate the engine operation under these different operation conditions, it seems appropriate to perform a crude evaluation. We wish to evaluate the effects of these means, and to provide a rough indication of how to plan the experiment more effectively. For this purpose a simplified model-can no doubt be beneficial. In this paper we will explore how feasible it is to keep the exhaust gas temperature above a given pre-determined temperature-by using these simple-to-employ means.