火焰预热塞汽化腔内柴油流动汽化特性研究

基于预热塞汽化腔内的燃油流动汽化特性及火焰稳定性对重型柴油机的冷起动特性的影响，设计加工了石英预热塞对柴油流动汽化过程进行可视化研究，同时采用流体体积（VOF）模型和流固耦合模型对不同流量的柴油在汽化腔内的流动和汽化过程进行数值模拟.结果表明：柴油泵入火焰预热塞后呈扇形扩散并在边缘开始发生汽化，进而出现大量气泡；柴油流量增大加速油液扩散，更早地接触到加热棒的发热区域并发生汽化，但也会带走更多热量并缩短与高温壁面作用的时间，导致汽化能力减弱，使稳态下汽化腔内和出口位置的柴油蒸汽体积分数减小；较大流量的柴油也会使加热棒温度上升放缓甚至出现下降的趋势，不利于后续泵入柴油的汽化.因此需要合理控制火焰预热塞内的柴油流量以保证汽化特性，进而保证良好的火焰特性及进气预热效果.

Numerical Simulation of Diesel Flow in Vaporization Chamber of Intake Manifold Burner

The combustion characteristics of intake manifold burner have a great influence on cold start characteristics of heavy-duty diesel engine, and the flow and vaporization characteristics of fuel in vaporizing chamber determine the ignition characteristics and flame stability of intake manifold burner. In this paper, a quartz intake manifold burner was designed to visually study the flow and vaporization process of diesel. At the same time, the flow and vaporization process of diesel with different flow rates in vaporization chamber were simulated based on volume of fluid (VOF) model and fluid-solid coupled model. The results show that the diffusion of diesel at the inlet is fan-shaped after pumping fuel into the burner, and diesel begins to vaporize at the edge of sector area. When diesel flows into the high-temperature region close to the heating rod, a large number of bubbles generate, namely the vaporization occurs. Compared with the case of low flow rate, the diesel with large flow rate diffuses faster and flows into the heating area earlier, while more heat is taken away and the interaction time with high-temperature wall is shortened, resulting in the weakening of vaporization capacity and the reduction of diesel vapor volume fraction in vaporization chamber and at the outlet in the steady state. Large flow rate of diesel also slows down or even declines the temperature rise of heating rods, which is not conducive to the vaporization of subsequent diesel. Therefore, it is necessary to reasonably control the diesel flow rate in intake manifold burner to ensure the vaporization, so as to ensure the stable development of flame and intake air preheating performance.