凝胶汽油双股撞击式雾化速度场实验研究

为研究凝胶剂含量、撞击角以及喷射压力等参数对凝胶汽油双股撞击式雾化速度场的影响,实验室制备了凝胶剂含量分别为4%和5%的QNJ-4、QNJ-5凝胶汽油样品。利用旋转式流变仪分别对QNJ-4、QNJ-5凝胶汽油的表观粘度进行了测量,并拟合了反映其表观粘度变化的幂率公式。采用粒子图像速度仪测量了撞击角θ分别为60°、75°、90°、105°和120°,喷射压力p为0.5 MPa、0.75 MPa、1.0 MPa和1.25 MPa条件下双股撞击式雾化流场的速度分布。结果表明:凝胶剂含量越高,反映凝胶汽油表观粘度变化的幂率公式中,粘度系数k越大,流动指数n越小;凝胶剂含量越高,凝胶汽油撞击雾化后的液滴速度越小;在撞击点下游,中心轴线上的液滴速度vl沿轴线呈总体下降的趋势,但由于撞击点产生的不稳定波的作用,液滴速度vl会出现波动;随着撞击角的不断增大,凝胶液滴的核心速度vc不断减小,但在撞击角为105°会出现暂时增大;随着喷射压力的增大,凝胶汽油雾化后的核心速度vc不断增大,但增大幅度越来越小。

Experimental Research on Velocity Field of Impinging Atomization of Gel Gasoline

Gel gasoline samples of QNJ-4 and QNJ-5 are prepared to investigate the influence of the factors, such as gel content, impinging angle and injection pressure, on velocity field of impingement atomization. The apparent viscosity of gel gasoline is researched by rotational rheometer with cone-and-plate configuration, and the power-low model is used to fit the apparent-viscosity to shear-rate curves of QNJ-4 and QNJ-5. The velocity field of impinging atomization with impinging angles of 60°, 75°, 90°, 105°and 120° and injection pressures of 0.50 MPa, 0.75 MPa, 1.00 MPa and 1.25 MPa is researched by the particle image velocity (PIV) system. The results indicate that the consistency index k increases with the increase in gel content maintaining while the flow index n decreases at the same time. The velocity of drops, which is produced by impinging atomization of gel gasoline, is decreased with the increase in gel content. The drop velocity on the axis of atomization area becomes smaller and smaller from impinging point to downstream, and there is the same fluctuation of the speed which is induced by the circular instable waves generating from the impact point. The core speed of gel gasoline drops is decreased with the increase in impinging angle and the reduce in injection pressure.