拦污栅结构对进出水口水力特性影响试验研究

Experimental study on effect of trash rack structure on hydraulic characteristics of inlet and outlet

对于进出水口水力特性研究,尤其是物理模型试验,由于拦污栅栅条细、间隔近,模型模拟困难,因此一般不模拟拦污栅结构本身。为探究双向流动条件下拦污栅结构对进出水口水力特性的影响,本文建立了大尺度进出水口试验装置,开展模拟拦污栅结构(有栅)和不模拟拦污栅结构(无栅)的进出水口水力特性试验研究。结果表明:拦污栅结构使断面时均流速分布均匀化,出流工况有栅的流速不均匀系数比无栅的改善了7.1%,进流工况有栅的流速不均匀系数与无栅的基本相同;拦污栅结构对水流的扰动使流速脉动剧烈,紊动强度增大,出流工况和进流工况有栅的平均紊动强度比无栅的分别增大了49.0%和38.5%;拦污栅结构对进出水口流量分配基本无影响;拦污栅结构使进出水口水头损失有所增大,出流工况和进流工况有栅的进出水口水头损失系数比无栅的分别增大了6.3%和7.2%。有栅和无栅的进出水口水力指标,除紊动强度差别较大外,其余差别不大,因此研究进出水口水力特性时不模拟拦污栅结构的结果基本能反映进出水口的水力学特性。研究成果可为进出水口及拦污栅设计提供参考。

In the study of hydraulic characteristics of the inlet and outlet, especially in physical model tests, the trash rack structure is generally not simulated because of the difficulty in modelling its closely spaced thin fence bars. To investigate the influence of a barrier structure on the hydraulic characteristics of an inlet and outlet under two-way flow conditions, we build a large-scale inlet and outlet test facility,conduct an experiment on a model inlet and outlet that is equipped with a trash rack structure, and compare it with the no trash rack case. The results show adding this structure results in a uniform distribution of time-average flow velocity behind it. In the outlet mode, the coefficient of flow uniformity is reduced by 7.1% from the no rack to the trash rack case;in the inlet mode, it is nearly the same in both cases. The rack disturbs the flow and intensifies velocity pulsation and turbulence intensity. Under its disturbance,the average turbulence intensity is increased by 49.0% and 38.5% in the outlet mode and inlet mode respectively, but flow distribution across different channels has little change in either flow mode. The trash rack structure produces head loss: the loss coefficient in the trash rack case is increased by 6.3% and 7.2% in the outlet mode and inlet mode respectively. The hydraulic indexes of the inlet and outlet in the two cases are not very different except for a large difference in turbulence level. This demonstrates the fact that the results obtained from a model inlet and outlet of no trash rack modeling can basically reflect its hydraulic characteristics.