选择性催化还原系统防沉积物堵塞喷嘴设计与喷射特性分析

针对选择性催化还原系统产生的沉积物易造成喷嘴堵塞,引起喷嘴管路背压过高及雾化喷射不均匀等问题,设计并研制了一种防沉积物堵塞喷嘴。该喷嘴通过调节喷嘴芯与螺套的锁紧量调定喷嘴的稳定喷射压力,并通过对喷嘴芯的最大开度进行机械限位,有效避免了尿素雾化喷射不均匀及NH 3逃逸等问题。对喷嘴的起闭特性与孔口径向截面的流量特性进行了理论分析,结果表明:当喷嘴因沉积物造成堵塞时,喷嘴芯开度随压力升高而增大,喷嘴孔口径向截面面积及截面质量流量也随之增大,有效提高了喷嘴内部沉积物的排出率,并降低了孔口外部沉积物的凝结风险。采用流体仿真软件Fluent对喷嘴的喷射特性进行了数值模拟,进一步探究了不同喷嘴芯开度及锥度角对喷嘴孔口径向截面面积、截面速度分布及截面流量特性的影响。最后,通过试验验证了喷嘴的喷射效果与开启压力精度。试验结果表明:采用该喷嘴后,喷嘴雾滴分布均匀,雾化效果良好,且在各稳定喷射压力下喷嘴均可以稳定开启,开启压力精度为±5%。

Design and Injection Characteristic Analysis of Anti-Sediment Clogging Nozzle for Selective Catalytic Reduction System

Aiming at the problem of nozzle clogging caused by the sediment produced by selective catalytic reduction (SCR) system, and the problems of high back pressure in nozzle pipeline and uneven atomization spray caused by the sediment, an anti sediment clogging nozzle was designed and developed. The structure and working principle of the nozzle were introduced. The stable injection pressure of the nozzle can be set by adjusting the locking amount between the nozzle core and the screw sleeve. The maximum opening of the nozzle core could be mechanically limited, which can effectively avoid the problems of uneven atomization spray of urea and the escape of NH3. The opening and closing characteristics of the nozzle core and the mass flow rate characteristics of the orifice section were analyzed theoretically. The results show that when the nozzle is clogged by sediment, the nozzle core opening will increase with the increase of the pressure inside the nozzle, and the nozzle orifice radial section area and mass flow rate also increase, which not only effectively improves the discharge rate of sediment inside the nozzle, but also reduces the risk of sediment condensation outside the orifice. The numerical simulation of the atomization spray characteristics of the nozzle was carried out by using the fluid simulation software Fluent. The influence of different nozzle core openings and taper angles on the orifice radial section area, orifice section velocity distribution and orifice section mass flow rate characteristics of the nozzle was further studied. Finally, the atomization spray effect and opening pressure accuracy of the nozzle was verified by test. The test results show that the atomization spray effect of the nozzle is satisfactory, and the droplet distribution is relatively uniform. And at each stable injection pressure, the nozzle can be stably opened, and the opening pressure accuracy is ± 5%.