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钻头喷咀距井底岩石面的距离关系到洗井液射流能量能否被充分利用。 用入口为圆锥形的喷咀产生的淹没非自由射流冲蚀人造砂岩及天然岩石的实验证明,随着喷咀与岩石面距离的增加,射流冲蚀岩石体积也增加,在某一个距离上冲蚀体积达到最大值。这个距离大于射流的等速核长度。距离继续增加,射流冲蚀岩石的体积减少直到为零。 产生最大冲蚀体积的距离与喷咀结构有关,与射流压力与冲蚀时间无关。 淹没非自由射流冲蚀岩石的主要原因之一是在射流中存在有空化冲蚀现象。
The distance from the bit nozzle to the rock face at the bottom of the well relates to whether the jet fluid energy of the wellbore can be fully utilized. Experiments on erosion of artificial sandstone and natural rock by submerged non-free jets created by conical nozzles have shown that as the distance between the nozzle and the rock surface increases, the volume of the jet erosion rock also increases, and at some distance, Erosion volume reached its maximum. This distance is greater than the jet’s isokinetic length. The distance continues to increase, and the volume of the jet erosion rock decreases until it reaches zero. The distance that produces the largest erosion volume is related to the nozzle structure, regardless of jet pressure and erosion time. Inundation of non-free jet erosion of rock one of the main reasons is the presence of jet cavitation erosion phenomenon.