超声速气流中简化微小液滴横向喷射的汽化过程探索

摘要

为研究超声速气流中简化液滴的汽化过程问题,本文分析了两相流计算中已有的两相传热模型,并对简化液滴绕流开展数值计算.在来流Ma≤0.6的条件下,数值计算得到的简化液滴-气流之间的传热速率与已有模型得到的结果相一致,而在来流Ma≥0.9的条件下,数值计算得到的简化液滴-气流之间的传热速率与已有模型得到的结果存在很大偏差.由此建立了考虑简化液滴与气流相对超声速相互作用的两相传热模型.进一步,采用Charles B.Henderson阻力系数关系式与新建立的传热模型,对不同直径简化液滴的运动与汽化开展工程计算.在来流2.7Ma的二维平板超声速流场中选取一个截面,作为气相流场,结果显示,(1)简化液滴与主气流存在相对超声速作用.当简化液滴直径dk≤0.12mm时,作用区域约为0.1m～0.4m,当dk>0.12mm时,作用区域明显增大,(2)简化液滴的穿透尺度不超过0.011m/m(深度/长度),时间尺度约为0.28ms～3ms,(3)简化液滴完成汽化的空间尺度约为0.1m(dk>=0.03mm)、0.45m(dk>=0.05mm)与1.24m(dk>=0.075mm),而当dk>0.09mm时,简化液滴完成汽化的空间尺度则大于1.9m.使用考虑简化液滴与气流相对超声速相互作用的两相传热模型与使用传统的传热模型对简化液滴的运动轨迹没有影响,而对简化液滴的汽化过程有较大影响.%To explore the process of evaporation of simplified droplet in supersonic flow, the existing two phase heat transfer models used in two phase flow calculation are analyzed and the numerical simulation of flow passing simplified droplet is carried out. Under the condition of Ma 0.6 inflow the obtained results of simplified droplet - gas heat transfer rate accord with those of the existing model. But under the condition of Ma 0.9 inflow the obtained results of simplified droplet - gas heat transfer rate show large deviations from those of the existing model. So based on the. numerical simulation data a new heat transfer model of two phase flow with considering the relative supersonic interaction is established. Further more, the drag coefficient formula given by Charles B. Henderson and the new heat transfer model are applied to calculate the motion and evaporation of the simplified droplets with different diameters. One section of two dimensional supersonic flat flow with Ma 2.7 inflow is chosen as gas flow field and the results show that,( 1 ) there is relative supersonic interaction between the simplified droplet and the main gas flow, the distance of which is about 0. lm ～0.4m for the simplified droplets with dk ≤0.12mm diameters and increases obviously for those with dk ＞0.12mm diameters, (2) the penetration scale of simplified droplets is not beyond the 0.011 m/m (deep/distance)and the time scale is about 0.28ms ～ 3ms, (3) the distance scale of simplified droplet completing evaporation is about 0. lm for the simplified droplet with 0. 03mm diameter, about 0.45m for one with 0.05mm diameter, and about 1.24m for one with 0.075mm diameter, but for those of dk ＞0.09mm the distance scale is greater than 1.9m. Using the two heat transfer models there are no effect in the traces of simplified droplet but much effect in the evaporation process of simplified droplet.