Design And Experimental Investigations On Performance Of The HC Adsorptin-desorption System During The Cold Start

Improving the engine thermal efficiency and reducing the toxic emissions have become important in the development of internal combustion engines.With the increase of the vehicle number,the influence of engine emissions to the environment also increasingly obvious.The engine may expel large amounts of HC emissions during the cold and even warm starting conditions.In the cold start period,as the low exhaust temperature,the three way catalyst could not reach its light-off temperature.It leads to a high concentration of exhaust emissions could not be converted by the TWC and this could be occurred in the warm start conditions as well.The adsorption could be occurred under high pressure and low temperature conditions,whereas desorption could be taken place under low pressure and high temperature conditions.The above characteristics of absorber makes it could efficiently adsorb HC emissions to the surface of sorbent.Activated carbon materials are widely used in the field of gas or liquid purification because of its strong adsorption.However,few studies reported the activated carbon on adsorbing HC emissions under the real engine conditions.Therefore,the general purpose of this work is to examine the adsorption and desorption characteristics of activated carbon materials for reducing and desorbing HC emissions from the gasoline engine under different starting coolant temperatures and different heating temperatures.The general purpose of this work is to reduce HC emissions from the gasoline engine under starting conditions.Three kinds of activated carbon materials(activated carbon honeycomb,activated carbon foams and activated carbon fibers)were selected to adsorb HC emissions within 80 s from the onset of starting at different coolant temperatures of 25,35,45 and 55 ?,respectively.The experimental results showed that the total HC adsorption rates of activated carbon materials declined with the increase of coolant temperatures.The total HC adsorption rates of activated carbon honeycomb,foams and fibers were 68.6%,66.1% and 53.5% under the coolant temperature of 25 ?.The early desorption was found for activated carbon foams,which was getting severe with the increase of coolant temperatures.Then,the adsorption performance of activated carbon honeycomb was further investigated at the repeated engine starting conditions.Under the repeated starting conditions,the total HC adsorption rates of activated carbon honeycomb decreased with the increase of adsorption times in the test.The total HC adsorption efficiencies of the first three times under repeated starting conditions were 76.4%,63.7% and 54.0%,respectively.The results showed that the adsorption processes could be divided into three phases based on the adsorption characteristics,which were rapid adsorption phase,interim adsorption phase and slow adsorption phase,respectively.In order to solve the decreased HC adsorption rates in the repeated engine starting adsorption experiment,an adsorption-desorption system was designed to reduce and recycle HC emissions generated within the gasoline engines during the cold start.The HC desorption ability of activated carbon honeycomb after adsorption was investigated at different heating temperatures of 200,240,280 and 320 ? for 80 min.A heating ring was adopted to simulate the exhaust temperatures during desorption.The HC desorption abilities at heating temperatures of 200 and 320 ? were further investigated.The results showed that at different heating temperatures,two peak HC concentrations were found in desorption process,which were generally appeared at the 5 and 20 to 30 min from the onset of desorption.The first and latter peak values of the desorbed HC emissions were increased with the heating temperatures.The HC adsorption rates at different heating temperatures were first gradually decreased and finally become stable during the adsorption-desorption cycles.