Study on the influence of the expansion angle of the side inlet/outlet roof on the velocity distribution of the trash rack section
The two-way flow of the side inlet/outlet of the pumped storage power station,the size of the roof ex-pansion angle will directly affect the uniformity of the flow velocity distribution of the trash rack section,and even the reverse flow velocity.The design code of pumped storage power station takes 3°～5° as the recommended range of expansion angle of side inlet/outlet roof,which is based on the expansion angle with the smallest resistance coef-ficient of rectangular diffuser.However,the shape of side inlet/outlet is much more complicated,so it is necessary to further explore.In this paper,a side inlet/outlet shape is taken as the research object,and the numerical simu-lation method is used to study the influence of the roof expansion angle of 11 angles on the flow velocity distribution of the trash rack section under the outflow condition and the inflow condition.The results show that under the out-flow condition,with the increase of the expansion angle of the roof,the mainstream position of the middle-hole trash rack section gradually decreases from the middle to the bottom,and the flow velocity distribution of the sec-tion tends from basically symmetrical to asymmetrical with larger at bottom and smaller on the top.When the expan-sion angle of the roof is large,the reverse flow velocity appears in the upper part of the middle-hole trash rack sec-tion.With the increase of the expansion angle of the roof,the velocity distribution of the side hole trash rack section gradually changes from the basic uniformity to the uneven distribution of the bottom and the upper part.With the in-crease of the roof expansion angle,the non-uniformity coefficient of the flow velocity at the orifices of the middle and side holes gradually increases,but the flow velocity distribution of the middle hole trash rack section is more affected by the roof expansion angle.In the inflow condition,with the increase of the roof expansion angle,the velocity dis-tribution of the middle and side hole trash rack section and the non-uniformity coefficient of the orifice velocity have no obvious influence.The research results can provide guidance for optimizing the design of side inlet/outlet.
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