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1、水工建筑物，29卷，9号，1995旋涡隧道溢洪道。液压操作条件M . A 戈蓝，B. zhivotovskii,我诺维科娃，V . B 罗季奥诺夫，和NN罗萨娜 娃隧道式溢洪道，广泛应用于中、高压液压工程。因此研究这类溢洪道这是 一个重要的和紧迫的任务，帮助在水工建筑中使用这些类型的溢洪道可以帮助制 定最佳的和可靠的溢洪道结构。有鉴于此，我们希望引起读者的注意，基本上是 新的概念（即，在配置和操作条件），利用旋涡流溢洪道1, 2, 3, 4。一方面， 这些类型的溢洪道可能大规模的耗散的动能的流动的尾段。因此，流量稍涡旋式 和轴向流经溢洪道的尾端，不会产生汽蚀损害。另一方面，在危险的影响下，高

2、流量的流线型面下降超过长度时，最初的尾水管增加的压力在墙上所造成的离心 力的影响。一些结构性的研究隧道溢洪道液压等工程rogunskii，泰瑞， telmamskii，和tupolangskii液压工程的基础上存在的不同的经营原则现在已经 完成了。这些结构可能是分为以下基本组：-涡旋式（或所谓的single-vortex型）与光滑溢洪道水流的消能在隧道的长度时 的研究的直径和高度的隧道；参看。图1）,而横截面的隧道是圆或近圆其整个 长度。涡旋式溢洪道-与越来越大的能量耗散的旋涡流在较短的长度- (60 - 80)hT or (60 - 80)dT (where dT and hT are th

3、e diameter and height of the tunnel; cf.Fig. 1), while the cross-section of the tunnel is either circular or near-circular throughout its length.- vortex-type spillways with increasingly greater dissipation of the energy of the vortex-type flow over a shorter length Lr -It should be noted that the e

4、ddy node is designed so that A = Areq, where Are q is the value of the geometric parameter of the vortex generator needed to maintain the required prerotation of the flow. For example, for the conditions of the Tupolangskii vortex-type spillway, Are q = 1.4; for the Telmamskii hydraulic works, Are q

5、 = 0.6; and for the Rogunskii spillway, Ar:q = 1.1.A second parameter which characterizes the degree of rotation of the flow on individual legs of the tailrace segment is the integral flow rotation parameter II 1, 2. The prerotation 17 0 behind the vortex generating device at a distance 3.0dT from t

6、he axis of the shaft may be determined on the basis of graphical dependences thus: 17_o = f(A) (Fig. 4).Tailrace tmmd. The overall widths of the tunnel are determined by the type of spillway design which is selected and the method decided on for dissipation of the excess energy (either by means of s

7、mooth or increasingly more intensive dissipation). Energy Dissipation Chamber. The choice of design and dimensions depends on the rate of rotation of the flow at the inlet to the chamber and on the length of the tailrace tunnel following the chamber. For a tailrace tunnel with LT/d T _ 60, it is bes

8、t to use a converging tube (or cylindrical) segment as the conjugating element between the tangential vortex generator and the energy dissipation chamber. The segment will be responsible for the following functions: reduction of the rate of rotation of the flow at the inlet to the energy dissipation

9、 chamber, equalization of flow rates accompanied by a shift in the maximum axial component of the flow rate into the central portion, and reduction of the dynamic loads at the rotation node of the flow.From the foregoing discussion it follows that in those cases in which there is no entrapment of ai

10、r, vortex spillways may be modeled with respect to all the required criteria. The situation is different in the case of aerated flow, which is also difficult to model. In hydraulic models with external atmospheric pressure, the volumetric content of air varies slightly as the flow is transported dow

11、n the shaft to the critical section, whereas in the physical structure, the entrapped air, moving downwards, is compressed by the increasing pressure of the liquid. Thus, in the case of the spillway at the Teri hydraulic works (Fig. 1), the percent compression in the physical structure is as much as

12、 15-fold, whereas in the open model constructed on a 1:60 scale, the percent compression is in the range 1.4-1.5, i.e., one-tenth that of the values found in the field. Moreover, in the experiments using the models, there was an increase noted in the angles of rotation of the flow in the initial seg

13、ment of the tailrace tunnel as the escapagedischarge was decreased and the content of air in the mixture was increased.Inasmuch as in the physical object the air content in the critical section is always insignificant, the increase in theangles of rotation as the volume of escapage discharge was dec

14、reased was unexpected. To create a reliable model of vortextype flow when there is a free level in the stem of the shaft and abundant air entrapment by the flow, it is necessary to isolatethe region of air in the upper and lower ponds from the external atmosphere and to reduce the air pressure in th

15、ese regions through creation of a vacuum in accordance with the geometric scale of the model. Hydraulic Conditions throughout the Spillway Segment. The hydraulic conditions of operation of vortex spillwaysdiffer substantially from the corresponding conditions for spillways constructed in the traditi

16、onal configuration. Let us consider these differences on the basis of the results of laboratory studies of the operational spillways of the Rogunskii hydroelectric plant (which includes an energy dissipation chamber) and the spillway of the Teri hydraulic works (which operates with smooth dissipatio

17、n of energy throughout the length of the tunnel).The initial design of the Rogunskii hydroelectric plant called for a chute as the terminus structure of the operational spillway; it was intended that the flow rate at the end of the chute was to reach 60 m/sec. Understandably, flow rates that arethis

18、 high entail adoption of special measures to protect the streamlined surfaces of the spillway from cavitation damage and the stream course from dangerous degradation. To meet this need, the Tashkent Hydroelectric Authority, working with the Division of Hydrodynamic Research (now the Central Hydrauli

19、c Institute, Society of the Scientific Research Institute on the Economics of Construction), developed several alternative versions of spillway designs intended to dissipate a significant portion of the energy of the flow within the spillway and to substantially reduce the flow rate in the tailrace

20、tunnel and at the point where the flow is discharged into the stream course. In one of the versions that were considered, the bend in the turning segment that is part of the traditional configuration of a shaft spillway was replaced by a tangential flow vortex generator. Similarly. vortex-type flow

21、is created throughout the entire length of the tailrace segment. Hydraulic studies were performed on a model that simulated a shaft spillway at a scale of 1:50 and consisted of a shaft measuring 13 m in diameter and 148 m in height, a tangential vortex generating device, and a tailrace tunnel.The st

22、udies that were performed showed that in the shaft which delivers water to the flow rotation node, an intermediate water level is maintained when the flow rate is less than the design rate. This bench mark depends on the magnitude of the escapage discharge and the resistance of the spillway segment

23、situated at a lower level . In the constructions that have been considered here, maximum (design) flow rates through the shaft are achieved when the shaft is flooded and there is no access to the air. In the model nearly complete entrapment of air from the water surface occurred with intermediate wa

24、ter levels in the shaft; moreover, the lower the level of the water surface, the more the air restrained the water flow and transformed the flow into a rotation node (Fig. 7). Stable vortex-type flow with a peripheral water ring and internal gas-vapor core is formed beyond the tangential vortex gene

25、rator. Due to asymmetric delivery of water into the vortex generator in the initial segments, the core of the flow is noncircular and situated away from the center of the cross section. Throughout the length of the initial cylindrical segment of the conduit, the gas-vapor core possesses a wave-like

26、curved axis which coincides with the axis of the tunnel even as close as 10dx from the axis of the shaft. As nonaerated flow enters the tailrace conduit through the rotation node, a vacuum-gauge pressure is established in the gas-vapor core, and in the case of highly aerated flow, gauge pressure, Th

27、e reduction in pressure in the gas-vapor core is associated with the effect of centrifugal forces in vortex-type flow, while an increase in pressure is associated with nearly complete release of air from the aerated flow into the core induced by the transport of air bubbles from the periphery to the

28、 center under the effect of the pressure gradient.For a tailrace conduit with cylindrical initial segment, the free area downstream increases from 0.7 in the section at a distance 1.3dv from the axis of the shaft to 0.77 in the section at a distance 12.4dr, while the angle of flow rotation and the a

29、xial and circumferential flow rates all decrease. In the case of a conical initial segment, the relative area of the gas-vapor core decreases from 0.987 to 0.874 over the length of the conical segment, while the angle of flow rotation decreases tobetween one-half and two-thirds its initial value ove

30、r this segment.A characteristic feature of the construction that is being proposed in the present article is the presence of an energy dissipation chamber in which vortex-type flow experiences an abrupt expansion and is rapidly transformed into axial flow if the discharge of flow from the tailrace t

31、unnel is directed into the atmosphere.Equality of the centrifugal acceleration to the free fall acceleration is an essential condition for breakdown of thevortex structure of the flow in the tunnel. Once equality is achieved, the mass of water traveling along the roof of the tunnel caves in, and mix

32、es easily with the air in the flow core. The transformation of vortex-like flow into axial flow that occurs here is accompanied by /*八significant dissipation of energy.The rate of energy dissipation differs between the two versions that are beingconsidered here (Fig. 8).In the case of a cylindrical

33、initialsegment, energy dissipation occurs smoothly, with only 60% of the initial energy ofthe flow dissipating overa distance of 15dw (Fig. 8a). In asystem with a conical vortex generator and energy dissipation chamber behind the generator, 86% of the initial energy of the flow dissipates as it trav

34、els through this segment,CONCLUSIONSApplication of the constructions ot vortex tunnel spillways that we have considered enable us to ensure effectivedissipation of the excess kinetic energy and overall reliability of the structure. The operating reliability of vortex spillways that are based on ener

35、gy dissipation in the tailrace tunnel in accordance with the schemes that have been considered in the present article is confirmed by the fact that the pressure fluctuations and the intensity of the turbulence dissipate smoothly throughout the tunnel and by the fact that these quantities are low level at the point of discharge of the flow into the lower pond. The conditions imposed by the configuration of a vortex spillway that is part of a hydraulic project are of decisive importance in deciding which energy dissipation scheme to adopt.