自吸式离心泵装有吸入箱与压出箱。吸入箱与压出箱之间有连接管道和节流孔。但是在所有工况下,液体都自压出箱灌回吸入箱,因此泵的流量减小而箱的容积必须增大。本发明的目的是增大自吸期间泵的排气量并提高泵抽吸单相液体时的效率。为此在吸入箱与压出箱之间装设一只常开 Self-priming centrifugal pump equipped with suction box and pressure box. There is a connecting pipe and orifice between suction box and pressure box. However, in all conditions, the liquid is pumped back into the suction tank from the pressure tank, so the pump flow decreases and the tank volume must increase. The object of the present invention is to increase the pump displacement during self-priming and to increase the efficiency of the pump when pumping single-phase fluids. For this purpose, a normally open space is provided between the suction box and the pressure box