| The Euro III and Eoro IV emission regulations require the emission test of the HC and CO of the light gasoline engines during the cold-start period,which are named IV experiment.The HC exhaust emission of the gasoline engine used in the Euro III emission regulations cycling test during the former 195 second of the cold-start period at the environment temperature of -7°C is 15 times more than that at the normal temperature,which is indicated on the coverd experimental report. In this paper, in order for gasoline vehicles to meet the Euro III emission regulation, an air heater was used to increase the cooling water's temperature before cold-start of the gasoline, which was hoped to solve the problems of quicken light-off of catalyst and reduce exhaust emissions at -7°C ambient temperature.The plan is using an air heater to increase the cooling water's temperature before cold-start of the gasoline,and the emission of the air heater is vented via the catalyst to improve the intake temperature of the catalyst.The plan which is a effectual measure to decrease the cold-start period emission can improve the cylinder wall temperature,cut down the quench effect, mend mixture and decrease the emission in the cylinder during the cold-start period.And also the way can improve the tempertature of the catalyst which has high transfer efficiency.And also this plan demand that the emission of the air heater is better than that of the engine.So the Other task is doing the simulation of the flow and combustion of the chamber of the air heater produced by Hebei Hongye Machinery Co.Ltd using the CFD software-STAR-CD.By analyzing the fluent,combustion, temperature field and the emission concentration field of the chamber ,to obtain the theory to design the air heater with low pollution and high efficiency. The simulation displayed that the highest velocity appears at the tangential air inlet flue.of the secondary air which accords with the planning programming.This can make the mixture more homogeneous and supply enough oxidant for the afterburning.The secondary air's velocity is higher head and shoulders above than the first air, which forms the negative pressure field and results in back flow when they encounter.So the mixture can obtains combustion stability and complete combustion. The experiment on engine test bench which can simulate and test the cold start characteristics of gasoline vehicles was done. The result indicated that this method can effectively reduce the exhaust emission of CO, HC and NOx during the cold-start period. Most of the HC emission is produced during the cold-start and the warming-up period which may be the former 90s.and the peak is at the speed-down moment of the engine.This experiment reduced 58.7% of the total HC emission before the catalyst and reduced 53.8% of the total HC emission behind the catalyst after the engine warm-up using the air heater.The peak of the CO emission which was most produced during the cold-start period and was oxidated after the catalyst initiation was at the speed-down moment no matter using the air heater or not. The overrich mixture ,lower air-fuel ratio and the catalyst not-initiation may be the reasons of the mass CO emission produced during the cold-start period. This experiment reduced 8.15% of the total CO emission before the catalyst and reduced 20.2% of the total CO emission behind the catalyst after using the air heater.For more fuel injected, inhomogeneous cylinder air-fuel ratio and higer combustion temperature are along with the higer working conditions of the engine, the peak of the NOx emission corresponds to the medium and higher working conditions of the engine. This experiment reduced 73.6% of the total NOx emission before the catalyst and reduced 71.4% of the total NOx emission behind the catalyst after the engine warm-up using the air heater. |
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