小桐子油及其生物柴油在旋流喷嘴中雾化特性数值模拟

为了掌握入射压力对生物质燃油在旋流喷嘴中雾化特性的影响规律,在不同入射压力条件下,采用Fluent数值模拟的方法对小桐子油和小桐子生物柴油进行雾化过程模拟仿真研究。结果表明:使用的旋流雾化喷嘴比普通喷嘴对索特平均直径(D32)有更好的优化效果,内螺旋结构增强了雾化的湍流强度,使得气液两相混合及对雾化液滴的破碎效果更好;在等温条件下,不同入射压力对D32、雾化总表面积、雾化速度、雾化贯穿距影响较大。入射压力越大,D32越小;入射压力越大,雾化总表面积、雾化速度、雾化贯穿距越大。入射压力对D32的影响存在临界值,即小桐子油雾化入射压力达到0.8 MPa、小桐子生物柴油雾化入射压力达到0.7 MPa后,D32趋于稳定,不会随入射压力的增大继续减小;通过曲线拟合及雾滴粒径数量密度分析,得到了不同入射压力距离喷嘴不同位置处轴向D32变化的拟合方程及雾化液滴不同粒径数量密度分布情况。

Numerical simulation of atomization characteristics of Jatropha curcas oil and Jatropha biodiesel in a swirl nozzle

In order to understand the influence of incident pressure on the atomization characteristics of biomass fuel in a swirl nozzle, Fluent numerical simulation method was used to simulate the atomization process of Jatropha curcas oil and Jatropha biodiesel under different incident pressures. The results showed that compared with the ordinary nozzle, the swirl atomization nozzle used had better optimization effect on the average Sauter diameter (D32) ,and the internal spiral structure enhanced the turbulent intensity of atomization, making the gas-liquid two-phase mixing and the effect of breaking the droplets better. Under isothermal conditions, different incident pressures had greater influences on D32, total surface area of atomization, atomization speed and atomization penetration distance. The greater the incident pressure, the smaller the D32; the greater the incident pressure, the greater the total surface area of atomization, atomization speed and atomization penetration distance. There was a critical value for the influence of the incident pressure on D32. After the atomization incident pressure of Jatropha curcas oil and Jatropha biodiesel respectivly reached 0.8 MPa and 0.7 MPa, D32 tended to be stable and would not continue to decrease with the increase of incident pressure.Through curve fitting and analysis of droplet particle size number density, the fitting equation of the axial D32 change at different incident pressure away from different positions of the nozzle and the number density distribution of different particle sizes of atomized droplets were obtained.