排气质量流量和过量空气系数对三效催化转换器动态特性的影响

Effect of Exhaust Mass Flow and Inlet Excess Air Ratio on Dynamic Characteristic of Three-Way Catalytic Converter

在发动机瞬态工况下,试验研究了排气质量流量、过量空气系数的阶跃幅值和周期对三效催化转换器动态特性的影响规律.试验结果表明,排气质量流量、过量空气系数的阶跃幅值和周期对三效催化转换器活性层中铈(Ce)表面氧气吸附和脱附存储能力(OSC)、排放影响显著.稀混合气向浓混合气阶跃后,排气质量流量增加,出口过量空气系数在理论混合气的时间并不线性增加,三效催化转换器出口排放降低,排气流量增加到一定值时,排放性能恶化.由浓混合气向稀混合气阶跃后,催化转换器出口的过量空气系数在理论混合气的时间随排气质量流量、过量空气系数的幅值线性增加.老化三效催化转换器的氧存储力减弱,是车载自动诊断系统(OBD)检测催化转换器是否老化的依据.

Dynamic response of three-way catalytic converter with different exhaust mass flows, inlet amplitude and period was analyzed experimentally under transient conditions. Results show that engine emissions and oxygen storage capacity （OSC）of three-way catalytic converter with Ceria （Ce）catalyst on the washcoat is affected by exhaust mass flow, amplitude and period of inlet excess air ratio. When ex- haust mass flow increases, emissions decrease at the beginning and turn deteriorated at some mass flow, and duration of outlet excess air ratio at stoichiometry increases non-linearly after the lean-rich step. Dura- tion of outlet excess air ratio at stoichiometry increases linearly as increasing exhaust mass flow and outlet excess air ratio amplitude after the rich-lean step. Oxygen storage capacity of Ceria of aged three-way cata- lytic converter is low and the on-board diagnostics （OBD） can diagnose the condition of three-way cata- lytic converter.