| 摘要 |
A multi-stage centrifugal pump wherein a casing surrounds an impeller and a fluid flow guiding insert in each pump stage. The casing is made of a ferritic material, and the inserts are made of an austenitic material. The casing defines with each insert a first clearance wherein a cylindrical surface of the casing is surrounded by a cylindrical surface of the respective insert so that the width of the clearance increases in response to heating of the inserts and of the casing at the respective first clearances. The casing further defines with each insert a second clearance which is disposed radially outwardly of the respective first clearance and wherein a frustoconical surface of the casing surrounds a complementary frustoconical surface of the respective insert so that the width of each second clearance decreases in response to heating of the casing and of the inserts at the respective second clearances. The width of the first clearances is zero or close to zero within a relatively low first range of temperatures, and the width of the second clearances is zero or close to zero within a relatively high second range of temperatures.
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