| The increasing of car ownership doesn’t only bring great convenience to people’s life,but also causes serious environmental problem. NOx (NO and NO2) is one of theautomobile’s pollutants, it is the reason that produces smoke and PM2.5, is harmful for thehuman body, and causes change of climate. Now SCR technology is one of the effectivetreatments to NOx, but also has difficulties to be solved.the catalyst and reducer of thistechnology have strong characteristics in high temperature, so could not effectively reduceemission of NOx under the condition of low exhaust temperature. Solid ammonium SCR(SSCR) technology can widen the working temperature of NOx catalytic reduction,improves NOx conversion efficiency of the engine in low exhaust temperature. Manycompanies and universities at home and abroad do a lot of experiments for the research ofSSCR they are the characteristic of ammonium salt and catalyst. They also test and verify theSSCR system in the car, but the research contents lack of study on the mixing characteristicsof tail gas and ammonia, NOx conversion efficiency analysis at low temperature.Basing on determining the reducing agent, this paper studies distribution of ammoniaand exhaust in the tail, the distribution of ammonia and NOx in the catalytic converter, NOxconversion efficiency in low temperature, the contents of the work are as follows:Using AVL BOOST software builds chemical simulation model, rectifies activationenergy and frequency factor of catalytic converter, using AVL FIRE software buildssimulation model to simulate the mixing of ammonia gas and tail gas in the exhaust duct,changes the boundary conditions such as the angle of the nozzle, the nozzle position, initialreducing agent temperature, then compares and analysis SCR system simulation graphicsjetting AdBlue. We conclude that direct injection of ammonia can not only shortens thelength of the exhaust channel, also can increases the installation angle of the nozzle, need not much too waste energy to increase the initial temperature, it has better distribution ofammonia than SCR system jetting AdBlue. We conclude directly injecting ammonia hasgood uniformity of ammonia, low requirement for the structure characteristics for catalyticconverter. Comparing with the SCR system injecting AdBlue it has small influence for thedistribution of ammonia when changes the boundary conditions such as ammonia nitrogenratio, temperature.Through changes the boundary conditions such as ammonia nitrogen ratio, temperature,airspeed, this paper does much simulation study and experimental analysis for NOxconversion efficiency. Firstly this paper researches the influence for NOx conversionefficiency when changes.This paper concludes there is a critical number of ammonianitrogen ratio it is0.8~0.9.when it is less than this value, the NOx conversion efficiencyincreases with the value increasing,when more than the value, NOx conversion efficiencygrows slowly, and causes the ammonia slip. Secondly, the influence of the airspeed value iscomplicated for NOx conversion efficiency. The airspeed value is neither too big, nor toosmall, in order to make better use of the high airspeed value,improve the conversionefficiency of NOx, we should improve the airspeed performance of catalytic converter, makeit more effectively when works at high airspeed value. Finally, when using the SSCR systemhandles NOx, the transformation effect of NOx is better in low temperature, even at150℃NOx conversion efficiency is about30%. |
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