不同预燃室结构对甲烷湍流射流点火燃烧的影响

基于光学定容燃烧弹试验平台,通过高速纹影摄像系统在相同甲烷燃料初始温度、压力及混合气浓度下,定量分析了不同结构预燃室湍流射流点火(turbulent jet ignition,TJI)的燃烧特性,包括火焰传播速度、火焰面积、火焰形态及燃烧压力等参数。研究结果表明,预燃室孔径越小,相同时间内火焰传播得越远,火焰传播速度和火焰面积增长速度越快,燃烧压力峰值越高。随着预燃室孔径减小,着火机理会由射流中带有火焰的火焰点火转变为火焰过孔时熄灭的喷射点火。喷射点火着火时刻延迟,初始火焰速度减慢,但燃烧压力峰值受影响不大。多级加速预燃室压力升高率与压力峰值与单孔预燃室相比变化不大。虽然火焰出口时速度较慢,但是火焰出口时刻提前且速度衰减较弱,因此多级加速预燃室火焰速度在短时间内超过单孔预燃室,并且压力和火焰面积也更早达到最大值。

Effect of turbulent jet ignition based on different pre-chamber structures on the combustion characteristics for methane fuel

The combustion characteristics of methane fuel under different pre-chamber structures, including flame propagation velocity, flame area, flame morphology and combustion pressure, were quantitatively analyzed by high-speed photogrammetry based on the constant volume combustion bomb. The results showed that smaller aperture can lead to larger penetrations within the same time, as well as higher peak pressure, faster flame velocity, and larger flame area growth rate. As the aperture become smaller enough, the ignition mechanism will change from flame ignition (with flame in the jet) to jet ignition (flame quenches when passing through the orifice). In the case of jet ignition, ignition timing is delayed and initial flame velocity is also slowed down, while the peak pressure is almost unaffected. Similar peak pressures and pressure rise rates were observed in all pre-chamber structures, though the exit velocity in multi-stage pre-chambers was lower. The slower velocity deceleration in multi-stage pre-chambers made the flame advances that in other single-stage pre-chambers in a short time. Meanwhile, the pressure and the flame area reached its maximum value earlier.