An Automatic Control Method of the no Removal System using Barrier Discharge

Abstract

Summary form only given. Diesel engine exhaust gas is one of the causes of air pollution. In order to reduce NOx emission from diesel exhaust gases, plasma processes have been studied in many places. However such studies are concentrated on plasma process itself. When we wish to industrialize the NOx removal system, it is natural that automatic NOx emission control system should be required. In our laboratory, we have studied an automatic control method of the NOx removal system using the barrier discharge, and we have succeeded to develop a method with which the NOx emission can be controlled in low level without using any NOx sensor. The automatic control system consists of an engine load measuring device, discharge power and hydrocarbon addition control systems. From the engine load, we can estimate the NO concentration at the engine outlet, and the NO concentration can be reduced to the required values by controlling the discharge power and the amount of hydrocarbon addition respectively. As the barrier discharge power is a non-linear function of the applied voltage and the frequency, a set of voltage and frequency was prepared to get linear relationship between discharge power and control instruction. Since hydrocarbon (gasoline) is very effective to increase the NO removal efficiency, it is injected into exhaust gases using a fuel injector. Addition of hydrocarbon makes controllable range wider and limits the discharge power to a moderate level. The automatic control method was applied to the NOx emission control system of a 2.4 kVA diesel engine generator and it demonstrated a successful NO emission control. In the presentation, we will introduce the algorithm that decides both the necessary discharge power and the amount of hydrocarbon, and also present the practical method of the hydrocarbon injection of required amount together with the total control program.