- 期刊
Experimental Study of the Flow in the Suction Pipe of A Centrifugal Impeller: Steady Conditions Compared with Fast Start-Up
摘要
It is common practice to assume that the pump characteristic expressed in nondimensional variables is not altered by a rotation speed variation. However previous experiments have shown that it is not the case when the rotation speed variation is very fast. In that case, the flow rate increases at a lower gradient than the rotation speed and partial load conditions prevail at the beginning of the start up period. The question is: is there recirculation and if so, what is its axial extent within the suction pipe compared to steady flow conditions at equal nondimensional flow rate? An experimental program has been set up to answer that question in the Laboratoire de Mécanique de Lille. This paper presents the experimental study of the influence of the operating point on the axial development of the inlet recirculation. The tests were carried out by means of a camcorder, Particles Image Velocimetry and Pressure measurements in the suction pipe, near the inlet of a centrifugal pump, at partial flow rates, in steady conditions and during a fast start up of the pump. All the experiments were performed on the DERAP test bench of the Laboratoire de Mécanique de L'Ecole Nationale Supérieure d'Arts et Métiers de Lille. Standard methods enabled the determining of the recirculation critical flow rate at the pump inlet. Visualization methods showed that the axial growth of the recirculation and the prerotation with the flow rate is considerably reduced during a fast start up compared to steady conditions.