Patterns of Powder Transport by Spiral Drill Pipes at Different Powder Inputs and Rotation Rates

Abstract

In order to obtain the relationship between powder input, rotation rate, capacity of powder exhaust, power consumption, vibrational disturbance during normal operation of a spiral pipe, experiments of powder transport with different powder inputs (88-91, 133-137, 176-182g/s) and rotation rates (240, 300, 360, 420, 480, 540, 600rpm) are carried out. The results show that with the powder input remaining constant and the rotation rate increasing, the amount of powder residue obeys an exponential distribution and decreases gradually, and that the power consumption and vibration acceleration increase linearly. The results indicate that: (1) the capacity of powder exhaust is positively related to the rotation rate and (2) the higher the rotation rate is, the lower will be the marginal increment of powder exhaust. Through comparison of the images captured by a high-speed camera, the powder being transported falls within two flow regimes: (1) depositing and moving axially, and; (2) being stirred and moved spirally. Based on the comparison of the curves of powder residue, power consumption and vibration acceleration, a conclusion is drawn that the rotation rate of the spiral drill pipe in soft coal bed shall be controlled strictly and shall be neither too high nor too low.