多点电喷气体发动机燃气脉宽控制策略设计

Design of MPI Gas Engine’s Gas Pulse Width Control Strategy

针对某品牌六缸多点电喷发动机,设计了发动机正常工况下的燃气脉宽控制策略。发动机控制器根据采集到的传感器信号,如转速信号、进气压力、进气温度等,分别计算出气缸的容积效率和空气质量流量。根据氧传感器信号的正常与否分别对空燃比进行开环、闭环控制,并根据进气温度、冷却水温和蓄电池电压等信号对空燃比进行修正。根据计算所需喷气量和喷气阀的流量特性确定发动机在正常工况下所需的燃气脉宽。在稳态情况下采用速度密度法求解空气质量流量,对于空气进气量的判断更为准确。通过PI控制调节空燃比的大小,能够快速将空燃比稳定在合适的范围,且调节响应速度快,超调量小。从而实现了对燃气脉宽的精准控制,提升了气体发动机的燃烧效率,降低了有害、有毒物质的排放。

A control strategy of gas pulse width under normal working condition is designed based on a certain brand of sixcylinder MPI engine. The ECU calculates volume efficiency and the mass flow of air respectively in the light of collected sensor signals, such as the engine speed, the intake pressure, the intake air temperature and so on. ECU performs the open-loop or closedloop control for air-fuel ratio according to whether the oxygen sensor signal is normal or not, and corrects it on the basis of intake air temperature, coolant temperature, the battery voltage and so on. Finally, ECU calculates gas pulse width combined the gas volume needed with the flow characteristics of injector under normal working condition. In steady state, it's more accurate to calculate the air intake quantity by the means of speed density formula. By adjusting the air-fuel ratio by PI control, the air-fuel ratio can be quickly stabilized in a suitable range, and the adjustment response speed is fast and the overshoot is small. Thus, the precise control of the gas pulse width is achieved, the combustion efficiency of the gas engine is enhanced and the harmful and toxic substances are reduced.