In order to realize an auto feeding and rotary water jet drilling of the in seam gas drainage borehole in the underground mine,the paper had a study to realize an auto feeding and jet type drilling high pressure nozzle.The nozzle had jet orifices set at the forward direction and backward direction of the nozzle.The jetting angle of the forward orifice was successively increased.During the jetting drilling operation,the backward orifice would have a jetting force higher than the forward jetting force and the jet water flow had a certain angle along the nozzle circumferential.With the hydraulics calculation on the nozzle and the jetting drilling experiment of the model under the jet pressure of 30 MPa,the relationship on the jetting hole diameter,drilling speed and rock sample strength was obtained.The study results showed that the nozzle experiment data and the theoretical calculation results were well fitted,the auto feeding and rotary jet drilling could be released and the average auto feeding force would reach at 63 N.With the pressure bellowed 15 MPa,the jetting hole diameter in the rock sample would be over 60 mm and the drilling speed would not be less than 8.16 m/h.The paper had proposals on the further improvement of the nozzle.%为实现井下煤层瓦斯抽采孔自推进旋转喷射钻进,研究能够实现自推进喷射式钻进的高压喷头,该喷头的前向及后向均布设喷孔,且前向喷孔喷射角度逐次增大,喷射钻进时后喷射力远大于前喷射力,且喷射水流沿喷头周向有一定偏斜角度.通过对该喷头进行水力学计算和30 MPa射流压力下模型射流钻进试验,得出了射流孔径、钻进速度与岩样强度的关系.研究结果表明:该喷头试验数据与理论计算结果较吻合,可实现自推进旋转喷射钻进,平均自推进力可达63 N,对于15 MPa以下的岩样射流孔径在60mm以上,且钻进速度不小于8.16 m/h.同时对喷头下一步的改进提出建议.
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