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压气沿钻杆和吹洗空间流动时,由于气体的内摩擦,会产生压力的沿程损失。为保证压缩空气的流动,必须有一个压力差,其值应符合于给定的吹洗炮孔的耗气量。如果在吹洗空间的A_1和A_2(A_1至A_2的长度为l)截面内(图1),A_1和A_2上的气压分别与P_1和P_2相对应,且P_1>P_2,我们即可确定出气体流动速度及耗气量。压力差△P_(TP)=P_1-P_2。将气流划出一个半径为r和厚度为dr的环形层来。作用于环形层端面的压力为N_1
Compression flow along the drill pipe and purge space, due to gas internal friction, there will be pressure loss along the way. In order to ensure the flow of compressed air, there must be a pressure difference that corresponds to the air consumption of a given purge borehole. If the air pressures on A_1 and A_2 correspond to P_1 and P_2, respectively, and P_1> P_2 in the section A_1 and A_2 of the purge space (A_1 to A_2 have a length of 1), we can determine the gas Flow rate and air consumption. Pressure difference △ P_ (TP) = P_1-P_2. Define the flow as a ring of radius r and thickness dr. The pressure acting on the end face of the annular layer is N_1