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This study relates to the simultaneous reduction of NOx and soot exhausted from Direct Injection Diesel Engine. With use of the surface treated carbon fiber, NOx is significantly reduced through the adsorption and chemical conversion into N2 and CO2. With use of stainless steel nets connected with the cathode and electro conductive material composed of Cu coated cloth, carbon fiber and stainless steel net connected with anode of the car battery, soot is collected electrically and is easily removal and combustible into CO2. The test result operated with 500 ml D.I. Diesel Engine shows excellent performance of NOx and Soot at more than 50% reduction with the long recycle life of the used material.

Since the engine noise of a small portable single cylinder 2 or 4 cycle gasoline engine exceeds 100 dB (A), making the reduction of noise levels is very important. Conventional noise reduction measures have been to expend the pulse flow energy of the exhaust gas even at some sacrifice of engine performance, that is, resistance is introduced to lower the flow rate. Recently, we have developed a carbon fiber felt from coal tar pitch, which shows high resistance to oxidation and physically and chemically stable properties, and used it in the exhaust muffler and in the bottom of the engine crankcase, enabling the reduction of noise emitted from the engine package by approximately 3 dB (A). Compared with rock wool and glass wool, this carbon felt has the superior characteristics of (a) lower mass and (b) larger surface area per unit weight (1)*.

Evidence has been obtained in this study to indicate that the hybrid muffler made up of heat-resistant thermosetting resin, ceramic paper, and carbon fiber felt used as a noise absorbing material, can reduce the noise without any compromise in engine performance. Further, it has been confirmed that a highly reliable muffler may be designed using this approach.