底部掺气设施水流掺气量的计算

Calculation of air entrainment for bottom aeration devices

掺气减蚀是高速水流泄水建筑物减免空蚀破坏的重要措施。为了有效地实现掺气减蚀,必须使通过掺气设施后的强迫掺气水流达到一定浓度的掺气量。利用本文提出的掺气坎射流轨迹的微分方程计算出了掺气空腔长度,并通过掺气坎供气系统的供气量与水流掺气量的平衡,给出了一种通过计算掺气坎射流空腔负压来确定水流掺气量的计算方法。计算结果与试验结果吻合良好。利用该方法,可对通风系统和掺气坎的设计体型进行初步验算,以判别掺气设施能否满足掺气减蚀要求。

The air entrainment to alleviate cavitation is an important measure to derate cavitation from the high velocity discharge structure. In order to realize air entrainment and alleviation of cavitation effectively, the air entrainment with a certain concentration must be got from the forced aerated flow through the aeration devices. The cavity length of aeration is calculated out with the differential equation given herein for jet trajectory of aeration device, and then a calculation method for defining the air entrainment based on the calculation of the negative pressure in the cavity of the aeration device is put forward through the balance between the air supply from the air supply system for the aeration device and the air entrainment into water flow. The calculation result is better fitted with that of the relevant test. On the basis of this method, a preliminary check can be made on the pattern design of both the aerating system and the aeration device, so as to judge whether the requirement of the air entrainment can be met with the aerating facility concerned.