氧化催化器出口温度控制研究

Investigation on Temperature Control of Diesel Oxidation Catalyst Outlet

氧化催化器(DOC)出口温度控制是实现颗粒捕集器(DPF)主动再生控制热管理的关键。本文结合DOC系统的实际特征对系统进行分析,研究DOC传热及化学反应特性,建立了DOC一阶加延迟的载体出口温度响应模型,并利用载体试验数据进行了模型参数校核,同时建立了热响应特征模型时间常数及延迟时间常数与排气流量的关系。依据系统模型特征,研究了基于内模控制架构的PID控制策略,采用Pade二阶非对称近似方法对系统响应延迟部分进行处理,利用经典PID控制器与内模PID控制器等效方法建立了PID参数求解方程,分析了滤波器参数的设置方法。该控制策略通过台架试验,选取连续变化工况进行测试,DOC出口温度在排气流量及入口温度均大幅变化的情况下,可以确保出口温度控制在(575±20)℃范围内。

Diesel oxidation catalyst outlet temperature control is crucial for heat management to realize diesel particulate filter active regenerative control. Combined with the actual characteristics of DOC to analyze and research the heat transfer process and chemical reaction characteristics in DOC,a first-order plus delay response model was established for the DOC carrier outlet temperature control. And the model was verified by the carrier test data on the engine bench. The relationships were described by a linear equation between the exhaust flow and thermal response time constant and a hyperbola equation with exhaust flow rate and delay time constant. According to the system characteristics,a PID control strategy was developed based on the internal model control structure,and the delay part of the system response used two order Pade non symmetry approximation method to substitute. Based on the internal model control structure,a filter was proposed to establish. The filter can regulate the response time and system stability. And by turning the parameter of filter,it can calculate the parameters of PID. The proposed control strategy was tested by engine test bench. To test a dynamic control effects,a continuous variety working condition with significantly changes in the exhaust flow and the entrance temperature of DOC for testing,the outlet temperature can be controlled within ± 20℃ at the target temperature of 575℃. The test results proved that the strategy was effective to control the temperature of oxidation catalyst outlet,and the strategy can provide a rational thermal management for DPF active regeneration.