水射流喷嘴增强气力提升性能的实验研究

Experimental Study on Airlift Performance Reinforced by Water Jet Nozzle

在钻孔水力开采过程中,井底对岩屑产生的压持效应易导致气力提升系统输送能力减弱。为此,采用与实际作业相近的槽内供砂方式并引入水射流喷嘴研究其影响系统性能曲线及临界工况点的机理及规律。结果表明:水射流喷嘴数量N=3时就可消除槽底压持效应,起到大幅提高颗粒质量流量与提升效率之目的,之后则随其增加又对气力提升性能影响甚微。水射流喷嘴分布的非均匀性过高与过低均不利于增强气力提升性能。此外,水射流喷嘴在气举头埋入砂层(即气举头底部至砂床表层距离H<0)后可显著提高颗粒质量流量与提升效率。临界输砂研究结果表明,水射流喷嘴未影响排水时的临界气量值Q_G,L,但却导致输砂临界气量值Q_G,S及与之对应的临界水流表观速度J_L,c_(ri)因压持效应得到解除而大幅减弱,而后则随N增加仅微量减小。实测值J_L,c_(ri)在H=0与理论模型中临界水流速度的计算值u_(Lcri)极为接近,但随H加大两者差异升高。

In the process of borehole hydraulic jet mining, the effect of chip hold-down produced at the bottom of the well on debris easily leads to poor transport capacity of an airlift system. To solve this problem, a new particle feeding method similar to the real situation was proposed, and the water jet nozzles were introduced to investigate the airlift performance and its critical points. The results are found as follows： The chip hold-down could be eliminated in the case of N= 3, in turn, this makes the mass flow rate of solids and lifting efficiency increase greatly and then have a slight variations with increasing N; The appropriate inhomogeneity of spatial distribution of the water jet nozzles are also given to promote the airlift performance. Moreover, the mass flow rate of solids and lifting efficiency are especially improved by using water jet nozzles in the case of H〈0. The research results of critical points show that the water jet nozzles have little effect on the critical air flow rate QG, L for conveying water. However, the critical air flow rate Qc, S and the critical volumetric flux JL, cri corresponding to lifting river sand are significantly decreased due to the disappearance of chip hold-down and then have a slight decrease with the increase of N. The JL ,cri is very close to the computational value of theoretical model uLcri when H=0. But as H rises, their differences increase gradually.