A study on heat transfer by pulsation of exhaust flow

Abstract

In recent years, the number of cars and motorcycles has increased around the world and now reached more than a billion. The environmental pollution is caused by the traffic emissions, being critical problem. As one of the countermeasures, higher and higher level standards of emissions have been defined in developed countries. A catalytic converter is one of the most important parts of vehicles' emissions control system, its operating temperature being very high. Vehicles emit most of their pollution during the first a few minutes of engine operation before the catalytic converter has warmed up sufficiently to be effective. Therefore, this study focuses on heating the converter up to the operating temperature, using wave phenomena formed in the exhaust pipe. A real automotive exhaust pipe is modelled as a straight pipe with an obstacle having honeycomb structure, instead of the catalytic converter. A pulsating flow is generated in the pipe using a rotary valve of which opening area changes with time corresponding to that of the exhaust port in a real engine. The pressure histories along the pipe and the temperature in the obstacle are measured. Analyzing the measurement data, the formation of shock is found to play an important role in the temperature rise of the obstacle. Furthermore, the relation is discussed between the wave phenomena and the heat transfer to the obstacle.