机载条件下单液滴撞击热固壁面相变特性

Phase Transition Characteristics of A Single Droplet Impinging on Thermosetting Wall under Airborne Conditions

为了获得机载工况下液滴换热特性和相变过程,基于耦合体积分数(coupled volume fraction,CLSVOF)法,研究不同撞击角度和不同加速度情况下R1234yf撞击壁面的铺展和传热行为。结果表明:当撞击角或加速度较小时,液滴在铺展过程中出现回缩现象,且液滴边缘会出现润浸现象,热流密度较高;液滴铺展速度和直径也随撞击角的增大呈先增大后减小的趋势。发生Leidenfrost现象时刻对应的壁面热流密度降低,说明撞击角对液滴与壁面的换热影响较大,且其值越小则液滴与壁面之间的换热越明显。液滴铺展速度和直径随飞机加速度的减小呈减小趋势,发生Leidenfrost现象时刻对应的壁面热流密度增大,说明加速度的增大导致换热被削弱。

In order to obtain the droplet heat transfer characteristics and phase change process under airborne conditions.Based on the coupled volume fraction(CLSVOF)method,the spreading and heat transfer behavior of R1234yf impacting the wall under different impact angles and different accelerations were studied.The results show that when the impact angle or the acceleration is small,the droplet shrinks during the spreading process,and the edge of the droplet infiltrates,and the heat flux density is higher.The spreading velocity and diameter of the droplets also increase first and then decrease with the increase of the impact angle.When the Leidenfrost phenomenon occurs,the wall heat flux density decreases,indicating that the impact angle has a greater impact on the heat transfer between the droplet and the wall,and the smaller its value,the more obvious the heat transfer between the droplet and the wall.The droplet spreading velocity and diameter show a decreasing trend with the decrease of the aircraft acceleration,and the wall heat flux density increases when the Leidenfrost phenomenon occurs,indicating that the increase of acceleration leads to weakening of heat transfer.