Numerical Simulation Research On Emission Reduction Of Ceramic Catalyst Turbine Based On Vehicle Warm-up

In the cold start phase of the internal combustion engine,catalyst cannot quickly reach the ignition conditions of the catalyst due to the lower exhaust gas entering the catalyst.The harmful gas components conversion efficiency of the catalyst declined seriously under before conditions.The presented research mainly focuses on the structure and location of the catalyst,the materials of the catalyst and carrier,pre-heating or heat preservation,etc.The results are not ideal.A ceramic catalytic turbine(CCT)technical plan was proposed in this paper.It moves the catalytic reaction forward to the turbine,and the characteristics of turbulence inside the turbine and high intake temperature was used to make the catalyst ignite quickly and improve the conversion efficiency.When using the characteristics of the rapid increase in turbine inlet temperature and internal turbulence to integrated the ceramic catalytic and turbine,the turbine catalytic element can be quickly ignited and the downstream catalytic converter’s performance can be improved under the similarly cost,.A numerical simulation of the catalytic reaction of the CCT during the warm-up period of a gasoline engine is carried out in this paper.The results show that the catalytic activity can be improved by the turbulence in the turbine.CCT has a significant impact on the harmful tissue components of exhaust gas when turbine inlet temperature up to 550 K.The conversion efficiency of harmful gases in the exhaust gas is sharp rising in the range of 575-625 K.In the case of high exhaust gas temperature(above 720K),the conversion efficiency of C3H6,CO and NO reaches 23.7%,21.1%and 15.5%,respectively.At the same time,the gas temperature at the outlet of the turbine increases by about 30 K.The results shown that the influence of the slight change in the thickness of the boundary layer on the simulation can be neglected.However,the calculation divergence can be caused by extremely thin boundary layer and it also affected by the intensity of the catalytic reaction.The catalytic light-off process can be described by the moving average of the catalytic reaction and the turbine inlet temperature.Through the numerical analysis of the catalytic turbine,it shows that the harmful gas components start to react when they enter the rotor area.The efficiency of reacting is higher when the intake air temperature increasing.The reaction volume is larger at the leading and trailing edges of the blade wall than other parts.The reaction is obviously within 20% of the front edge of the suction.The turbulent kinetic energy distribution of the flow field inside the turbine rotor is similarly with the reaction state of harmful gas components distribution,which shows that turbulence has the important effect on the catalytic reaction.It also shows that the ignition temperature of the catalytic reaction can reduced by the higher turbulence of turbine.At first,the influence of changes in engine air-fuel ratio and turbine operating conditions on the catalytic reaction of the turbine was analyzed in this paper.Experimental results of the catalytic turbine during the cold start of the engine and the possible effect of the turbine turbulent flow field on the catalytic reaction mechanism is also presented in this research.And the description of catalytic effect of catalytic turbines at lower temperatures by adjusting the relevant parameters of the Arrhenius equation is finished.The study found that the engine air-fuel ratio has an important impact on the reaction efficiency of the catalytic turbine.The reaction efficiency of harmful gas components in the turbine is inverse ratio with the O2 content.Under the engine cold start condition,keep the flow constant,the conversion efficiency of the catalytic reaction increases with the increase of the engine speed when the turbine intakes at a lower temperature,and when the turbine intake temperature reaches the temperature of control,the conversion efficiency increases with the speed decreases.The number of activated molecules increasing was caused by the higher turbulent state at a constant temperature.It is equivalent to a reduction in the activation energy of the reaction,which is the reason for determining the reaction rate of the catalytic turbine.The reduction in the activation energy within the adjustable range greatly improves the reaction conversion efficiency and exhaust temperature.