同轴旋转双射流冲蚀岩石机制与实验研究

EXPERIMENTAL STUDY ON ROCK BREAKING MECHANISM OF COAXIAL SWIRLING DUAL-JET

同轴旋转双射流是一种新型高效射流,它综合旋转射流破岩面积大和直射流破岩深度大的优点,并在较高围压下能够利用空蚀提高破岩能力。运用实验的方法研究常压淹没和围压条件下喷距、射流压力以及围压对射流破岩能力的影响。实验结果表明,双射流在冲击破岩时存在最优喷距范围,该次实验条件下最优喷距约为喷嘴当量直径的13倍;增大射流压力可大幅提高双射流的破岩体积。压力超过15MPa时,破岩体积大幅增长。双射流的破岩体积和破岩孔深均随围压的增大而急剧减小,破岩孔径随围压的增大而减小的幅度相对较小。双射流冲蚀破碎岩石机制包括空蚀破坏、直射流冲击破坏、剪切破坏以及压力波动破坏。

The coaxial swirling dual-jet inherits both the large impact area and deep penetration depth of swirling jet and round jet respectively,which is generated by placing a coaxial round jet at the axis of annular swirling jet. Under high confining pressure,the cavitation incepted by strong shear of the two jets can enhance breaking rock efficiency. Three parameters,nozzle distance,jet pressure and ambient pressure,are studied and the rock breaking mechanism is deduced. The experiments demonstrated that the rock breaking volume increases first then decreases with the increasing of nozzle distance,so an optimal nozzle distance exists′ which is 13 times of equivalent nozzle diameters. Nozzle distance also has great impacts on the rock penetration depth. With the increasing of nozzle distance,the penetration depth increases first then decreases. The rock breaking area is affected by nozzle distance too. With the increasing of nozzle distance,rock breaking area has almost linear increasing trend. The increasing of jet pressure can largely increases rock breaking volume. When the jet pressure is below than 15 MPa,the rock breaking volume hardly increases;when the jet pressure is over 15 MPa,the rock breaking volume greatly increases. Penetration depth was largely increased with the increasing of jet pressure. The rock breaking area was insensitive to jet pressure. The rock breaking volume and penetration depth will sharply decrease with the increasing of ambient pressure. But the rock breaking area is insensitive to confining pressure. The rock breaking of coaxial swirling dual-jet is a combination of cavitation erosion,jet erosion,shear breaking and pressure pulsation breaking.