基于空燃比控制的可调两级增压动态性能研究

以6缸可调两级增压柴油机为研究对象,设计了高压涡轮旁通闭环控制系统;建立了前馈式PI闭环控制算法,在瞬态过程中采用根据空燃比及其变化率对旁通阀开度进行调节的策略。瞬态工况试验表明,设计的闭环控制系统和算法对发动机动态响应性能的提高具有明显的效果。当发动机喷油量或者转速增加时,系统判断其进入加速或加载阶段,旁通阀立即关闭,进气压力迅速建立,减弱了涡轮增压系统的迟滞效应;当过量空气系数出现上升趋势时,旁通阀调节至查表所得的开度,待发动机喷油量和转速均不发生变化时,系统判断发动机恢复稳态,进入稳态闭环调节模式。对比其他不含动态判断的情况,发动机动态响应特性明显提升。

Study on the Transient Performance of Regulate Two Stage TurbochargingBased on the Air-Fuel Ratio Control

Taking a six-cylinder R2S turbocharging diesel engine as the research object, closed-loop control system of high-pressure turbine bypass valve was designed, and the feedforward PI algorithm was established. In transient process, the strategy that the bypass valve opening was controlled in accordance with the air-fuel ratio and its rate of variation was used. The results of the transient operation tests showed that certain closed-loop control system and algorithm had a substantial effect on the improvement of the performance of engine transient response. When the engine fuel injection quantity or speed increase, the system turns into transient condition, the bypass valve shuts down quickly and the boost pressure raises, which weaken the hysteresis effect of turbocharging system. When the excess air coefficient has a rising trend, the bypass valve will adjust to the angle from Map. When engine speed and fuel injection quantity do not change, the engine will turn into steady state, and the system will use the steady state closed-loop regulation mode. Compared with the system without transient judgment condition, the transient performance of engine had improved substantially.