旋转钻头喷嘴内流体运动规律理论研究

Law of motion of liquid in drill bit nozzles． CPM

从热力学第一定律出发，在绝对坐标系和相对坐标系下，分别分析了旋转钻头喷嘴内流体的运动规律，得出相对坐标系下喷嘴出口射流速度的计算公式。分析公式表明，喷嘴随钻头旋转时，旋转角速度、喷嘴在钻头上的位置及喷嘴内流体压差都对喷嘴射流速度有直接影响。设计钻头时要得到较高的喷嘴射流速度，应考虑增大喷嘴进出口相对钻头轴心线的距离以及提高喷嘴内部压力差。推导的公式与流体性质无关，故既适合于牛顿流体，也适合于钻井液等非牛顿流体。

s The law of motion of liquid in drill bit nozzles is analyzed respectively in the absolute and relative coordinate systems based on the first law of thermodynamics． The equation for calculating the jet velocity at the outlet of the nozzles is deduced in the relative coordinate system． When the nozzle rotates with the bit the rotary angular speed and nozzle location in the bit and pressure differential of the liquid in the nozzle all have direct impact on the jet velocity according to the result of the analysis． To obtain high jet velocity the distance between the nozzle outlet and the bit’s centerline should be enlarged and the pressure differential in the nozzle should be increased． The equation deduced is not relative to the type of the liquid it is suitable for both Newtonian liquid and non－Newtonian liquid as drilling fluid．