Abstract：To explore pressure drop in a hydraulic capsule transportation pipeline and pressure between two moving capsules extensively, the pressure distribution in the annular gap between a capsule and the pipe, the pressure distribution between two capsules as well as the pressure drop across capsules were measured and analyzed by using two capsules(length-100 mm, diameter-60 mm, weight-750 g)in 10 cm apart at 30, 40, 50, 60 and 70 m3/h flow rates. It is shown that the pressure in each test section increases with increasing flow rate. At a certain flow rate, the pressure on the capsule body presents a minimum. The pressure drop across the second capsule is substantially higher than that across the first one. In the annular gap, the pressure is low on the pipe wall and capsule body, but is the highest in the middle of the gap. The pressure shows a decline downstream in the gap of the first capsule, further the pressure gradient in the gap of the second capsule is higher than that in the first one. Under various flow conditions, the pressure distribution between two capsules is uneven in some degree, but the maximum pressure is achieved on the pipe wall and the minimum one is nearly at the pipe centre. The pressure gradient between two capsules increases with flow rate.
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