两阶段喷油在催化转化器性能考评台架中的应用

Application of two-stage injection in the catalytic converter test bench

催化转化器性能考评台架可以快速、有效的评价催化器的性能,具有较高的应用价值.在对催化转化器性能考评过程中,汽油机燃烧循环变动带来的转速波动,降低了空燃比控制的精度,从而影响了考评结果的可信性.为了降低燃烧循环变动,采用两阶段喷油的方式,将每循环所需的燃油一次喷射在进气冲程之前,形成缸内均质混合气;另一次喷射在进气冲程,用于提高点火瞬间火花塞附近混合气质量分数.通过对比不同喷油时刻和喷油比例时发动机的转速波动,分析了两阶段喷油参数对燃烧循环变动的影响.采用两阶段喷油进行了催化转化器空燃比特性试验,试验结果表明,通过优化喷油参数可以降低转速波动,提高空燃比控制精度.

The test bench has high value applications, which can quickly and effectively evaluate performance of the catalytic converter. During the bench the test process, gasoline engine cycle variation leads to speed fluctuations that will reduce control precision of A/F and the credibility of the bench test. Two-stage injections is adopted to reduce cycle variation. The first injection is before the intake stroke, which forms a homogeneous gas mixture. The other fuel is injected in the intake stroke, which enhances the gas mixture concentration around the spark plug during ignition. The impact of two-stage injections on cycle variation is studied by com- paring the speed fluctuations with different injection timings and injection proportion. The A/F characteristic of the catalytic converter is evaluated by adopting two-stage injections. Results show that speed fluctuation can be reduced by optimizing the injection parameter and A/F control accuracy can also be enhanced.