| As the engines are widely used nowadays, their exhausts become a more and moreserious problem, so it is very important to decrease the emission. EGR and Miller Cycle aretwo effective technologies to decrease the exhaust, many researchers have studyed theirperformance, but rarely refered to the effect of reducing NO_x by combining of these twotechniques, based on this fact, we got an idea that to simulate the performance of thecombined techniques.The single-cylinder engine was modeled with GT-Power (a simulation software), andthen regulated the accuracy of this quasi-dimensional model. In order to study the EGR, it’svery significant to bring the exhaust into the intake-tube smoothly, a venturi was designed tohelp carry the Lower pressure exhaust into the higher pressure intake-tube, there were twoinstall types of Venturi: in series and in parallel, then calculated and compared the impact onthe engine performance by these two connection types. The result shows that, both of thesetwo connection types would rise fuel consumption, and the in series installation type had themost high fuel consumption and the worst economical efficiency. For the in series installationtype’s throat of Venturi was too small to bring enough fresh air into the engine, it resulted inhigher fuel consumption. So, suggested to choose the parallel one as the final simulationmode to study EGR.On the parallel installation type, based on keeping the original engine intake pressure andincreasing the intake pressure projects, Then study the effect of the different EGR rate impacton the engine performance and the NO_x reduce.The computing results show that both ofthem could reduce the NO_x by a ratio of about70%at15%EGR ratios, the second one had abetter decreasing performance and a lower fuel consumption and Soot. In a word, theincreasing intake pressure EGR project had a better economical efficiency and loweremission.Based on Vary CAM Timing Miller Cycle and vary valve overlap Miller Cycle. Studythe different Miller Timing influence on the engine performance and NO_x emission. First ofall, we should design different Miller Timing and corresponding valve lift curve, thencomputed them, the result shows that the two kinds of c decreased the NO_x as the increasingof Miller timing, with the increasing of Miller timing, both projects’ fuel consumption increase, for Soot, with the increasing of Miller Timing, Vary CAM Timing Miller Cycle’Soot decrease, but varying valve overlap angle Miller Cycle’s Soot increase. And both ofthem can decrease the NO_x emission by60%with the highest Miller Timing. The result alsoshowed that vary valve overlap Miller Cycle had a better performance of decreasing NO_xemission but its Soot and fuel consumption was higher than Vary CAM Timing MillerCycle’s. Then, researched different compress ratios impact the performance and emission onthe Vary CAM Timing Miller Cycle engine, and the results showed that with the decreasingof compress ratio, the NO_x and Soot emisssion decreases, but the fuel consumption increasesand the engine needs a higher pressure to increase the pressure.Used the EGR combined with Miller Cycle to study the influence in economicalefficiency and emission of the engine. The results showed that with the variation of EGR rateand Miller timing, the fuel consumption and Soot had no regularly variation, but NO_xdecrease with the increase of EGR rate. The results were also compared with results of twokinds of Miller Cycle projects and two EGR projects, we found that when the EGR ratio waslower than9%, no matter how big the Miller ratio, the economical efficiency and emission ofEGR combined with Miller Cycle benefits a little, but when the EGR ratio is bigger than9%,EGR combined with Miller Cycle can decrease the NO_x emission by60%with the conditionof some low boost pressure and Miller ratio, while keeping a limited increasing of the oilconsumption and Soot, this solution maintain the economical efficiency while decrease theemission. |
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