CN116497755A - Method for improving inflow flow state of gate station combined pump station by using bridge pier diversion of trash remover - Google Patents
Method for improving inflow flow state of gate station combined pump station by using bridge pier diversion of trash remover Download PDFInfo
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- E—FIXED CONSTRUCTIONS
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- E02B—HYDRAULIC ENGINEERING
- E02B1/00—Equipment or apparatus for, or methods of, general hydraulic engineering, e.g. protection of constructions against ice-strains
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Abstract
The invention provides a method for improving the flow state of a front pool of a gate station combined pump station by using the diversion of a bridge pier of a sewage disposal machine, which belongs to the technical field of pump station engineering and comprises the steps that the front ends of diversion walls at two sides of the downstream of the gate station combined pump station are provided with the bridge pier of the sewage disposal machine, and the bridge pier of the sewage disposal machine is supported by a plurality of pier walls; the middle part of the front pool adopts an in-line bridge pier, and the bridge pier is parallel to the longitudinal center line of the front pool; the outer bridge piers are symmetrical in pairs relative to the longitudinal center line of the front pool, the horizontal center line of the bridge piers deflects outwards along the water flow direction, the flow direction is adjusted to be axial, the flow speed is uniform, the low-speed area of the front pool is reduced, the deflection angles of the symmetrical eight-shaped bridge piers of each group are optimized by calculating and analyzing CFD values of the downstream of a pump station, particularly the water flow field of the front pool, the flow state of the front pool is greatly improved, the area proportion of the low-speed area is reduced to be below 1% from more than 10%, sediment accumulation is avoided, the inlet drift of the water inlet flow channel of the side unit is eliminated, and the energy efficiency of the pump device is improved.
Description
Technical Field
The invention belongs to the technical field of pump station engineering, in particular to a method for improving the inflow state of a combined pump station of a gate station by using bridge pier diversion of a sewage disposal machine aiming at the pump station-water gate combined engineering.
Background
Large river channels in plain areas of China are usually required to have flood-driving, navigation and water-lifting irrigation functions, and a throttle gate and a pump station for controlling water level in a sectional mode are required to be constructed. In order to save land and engineering construction cost, a dam is usually built by blocking a river, and a throttle and a pump station are arranged in parallel on a dam body to form a water conservancy junction. In order to ensure the symmetry of water flow, the pump station is generally arranged in the middle of the barrage, the sluice is symmetrically arranged at two sides of the pump station, and the guide wall is arranged at the boundary between two sides of the downstream of the pump station and the sluice to ensure the inflow state of the pump station.
However, in practice, the gate station is combined with the pump station, and as the flow cross section in front of the diversion walls at the two sides of the downstream of the pump station is very wide, the flow is suddenly reduced from the very wide cross section to the front pool area between the two diversion walls, so that the front pool is close to the two side areas of the diversion walls to generate a larger low-speed swirling area, and larger transverse flow is generated in front of the inlet of the water inlet flow channel of the two side units, the flow in the front pool is extremely uneven and non-axial, so that sediment accumulation in a larger area is formed, and the efficiency characteristics of the pump station are influenced. Therefore, a technology is urgently needed to be invented, the front Chi Liutai of the station gate combined pump station is improved, sediment accumulation is eliminated, and the efficiency of the pump station is improved.
Disclosure of Invention
The invention aims to: the invention aims to overcome the defects that a large-area vortex low-speed area exists in a front pool of a pump station combined with a conventional gate station and a large transverse flow velocity exists in front of a side water inlet channel of the pump station, so that the large-area sediment accumulation of the front pool and the energy characteristic of a pump device are low.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a method for improving the inflow state of a gate station combined pump station by using the bridge pier diversion of a sewage disposal machine comprises the following steps:
A. gate station combines pump station downstream to set up the guide wall only-scheme one forebay flow CFD computational analysis:
the stop flow rate of the sediment is the critical flow rate of the sediment from moving to static in the water flow, and the calculation formula is as follows:
wherein: u (U) S Stopping the flow rate of the sediment, m/s; ρ s Is of sediment density, kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the ρ is the density of clear water, kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the g is gravity acceleration, m/s 2 The method comprises the steps of carrying out a first treatment on the surface of the d is in suspended sandValue particle size, m.
The starting flow velocity of the sediment is the critical flow velocity of the sediment on the river bed surface under the action of the water flow when the sediment is transferred from rest to motion, and the calculation formula is as follows:
wherein: u (U) e Starting the flow rate for silt, m/s; h is the average water depth, m; ρ s Is of sediment density, kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the ρ is the density of clear water, kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the g is gravity acceleration, m/s 2 The method comprises the steps of carrying out a first treatment on the surface of the d is the median diameter of the suspended sand; m.
Taking the straight river channel flow section of the position 5-8 times the water depth of the downstream diffusion section of the gate station as an inlet section, and taking the straight section of the water inlet channels of all operation units of the pump station as an outlet section as a water body part calculation domain, wherein the calculation domain also comprises an air domain with the height of 2m above the water surface; and (3) carrying out unstructured grid division on the calculation domain by using Mesh, wherein the overall maximum size of the prototype is not more than 1m, encrypting is carried out at the inlet and outlet of the calculation domain and the water surface, and the grid number needs to meet the requirement of independence verification.
Calculating the given mass flow of the inlet of the domain, the given mass flow of the outlet, and setting the solid wall boundary as a non-slip wall surface.
The calculation model considers the gravity influence, carries out CFD (Computational Fluid Dynamics) calculation on water flow in a calculation area at the downstream of the pump station, captures the water surface by adopting a VOF (Volume of Fluid) method, carries out post-treatment on the calculation result, obtains the water flow velocity and streamline distribution of the calculation area including the front pool of the pump station, observes the flow state in the front pool, judges the position and the area size of a sediment accumulation area in the front pool by using a formula (1), and judges the position and the area size of the area where sediment accumulation cannot be flushed away by using a formula (2). The severity of the forehearth silt deposition is expressed as a percentage of the deposition area to the forehearth area, and the ratio of the low-speed deposition area of the forehearth is calculated by applying the formula (3):
in the middle of: lambda is the area proportion of a low-speed area with the flow velocity of the front pool lower than the stop flow velocity of sediment; a is that l Is the area of a low-speed zone of a front pool at the inner side of the guide wall, m 2 ；A t Is the total area of the front pool on the inner side of the guide wall, m 2 。
When all units of the pump station operate, the flow state of the front pool is disturbed, a large-range low-speed swirling area exists inside the guide wall, the flow speed of the low-speed swirling area is lower than the stop flow speed of sediment, and sediment accumulation can be generated; the low-speed areas on the two sides of the front pool are used for back-extruding the main flow, so that the inflow side bias flow of the water inlet flow channels of the units on the two sides is serious except the middle unit.
B. The gate station is combined with the pump station inlet sewage disposal machine bridge layout position selection-layout is arranged at the front end of the downstream guide wall:
pump stations arranged on river channels are blocked, and three choices are arranged at the arrangement positions of the trash remover bridge: the first water pump unit is arranged at the inlet of the water inlet flow channel of each water pump unit, and one sewage disposal unit is arranged in one water pump unit. However, the sewage blocking resistance of the scheme can directly influence the inflow state and the performance of the pump device, and is rarely adopted at present; and secondly, the water pump station is arranged on the section of the river channel of the downstream river of the pump station, which is a common practice of arranging pump stations on the river at present. However, if the gate station is combined with the pump station, the trash rack is arranged on the river course, when the gate is opened by the hub to discharge floodwater and flow backwards, the water flow direction is opposite to the water flow direction when the pump station pumps water, the water flow is large, the incoming flow dirt amount is large, the trash rack can be blocked reversely, and the trash rack must be hoisted up to avoid blocking dirt in water when the river is discharged, so that the engineering equipment cost and the operation management difficulty are greatly increased. Moreover, when the pump station is switched to a water pumping working condition, dirt such as water grass in a river channel between the dirt removing bridge and the pump station can flow along with water flow to enter the water pump to cause blockage, the flow of the water pump is reduced if the water pump is light, the blades are broken if the water pump is heavy, and the operation safety of the water pump unit is seriously influenced; in order to solve the problems, a trash remover bridge is arranged between the heads of the two guide walls of the front pool of the pump station, and a trash rack and the trash remover are arranged, so that the water in the water is prevented from entering the water pump and is removed in time when water is pumped, and the influence on the flood discharge of the throttle valve is avoided. Meanwhile, the sewage disposal bridge adopts pier wall type piers, the head and the tail of the piers adopt streamline forms with small resistance, the piers are symmetrically arranged relative to the longitudinal central line of the front pool, the pier diversion of the sewage disposal bridge is adopted, the flow direction of water flow is adjusted to be axial, the flow speed is uniform, and the flow state of the front pool is improved.
C. The front end of the gate station combined pump station downstream guide wall is provided with a trash remover bridge, and the trash remover bridge adopts an in-line pier-scheme II guide to improve the flow state calculation and effect of the front pool:
the front end of the guide wall is provided with an in-line pier, the length direction of the in-line pier is vertical to the length direction of the bridge deck along the main flow direction, and the in-line pier is parallel to the guide wall, so that the front pool inflow contraction is prevented, and the water flow tends to flow uniformly along the axial direction of the front pool, thereby improving the front pool flow.
And C, carrying out CFD calculation on a downstream water flow calculation domain of the pump station, carrying out post-treatment on a calculation result to obtain streamline and flow velocity distribution in a front pool between two guide walls, calculating the proportion of the flow velocity smaller than the area of a sediment stop flow velocity region, observing the flow direction before the inlet of a water inlet flow channel of the water pump, and obviously reducing the area proportion of a low-speed region in the front pool and obviously improving the drift of the inlet flow channel compared with the case that no sewage disposal bridge is arranged.
D. A method for determining scheme III, namely, arranging a sewage disposal machine bridge at the front end of a downstream guide wall of a gate station combined pump station, wherein the sewage disposal machine bridge is an optimal splayed pier, and improving the flow state effect:
considering that the in-line piers of the front end sewage disposal machine bridge of the downstream flow guide wall of the second pump station have larger intervals, the in-line piers can not completely eliminate the phenomenon that the inflow of the front pool converges towards the middle due to the inertia of converging the inflow water towards the middle, and a low-speed swirling area with larger area still exists at the two sides of the front pool. In order to further reduce or eliminate the low-speed swirling areas on two sides of the front pool, the horizontal longitudinal center line of the front pool is taken as a reference, symmetrical straight bridge piers on two sides are deflected outwards by a certain angle around the vertical center line of the bridge piers along the water flow direction, the deflection angles of the two symmetrical bridge piers on two sides of the longitudinal center line of the front pool are equal, the deflection directions are opposite, the bridge piers on the left side of the longitudinal center line of the front pool are deflected clockwise when seen from top to bottom in the direction facing the incoming flow direction, the right bridge piers are deflected anticlockwise, the symmetrical bridge piers are distributed in an eight shape, water flow is guided to two sides of the front pool by the eight-shaped bridge piers, the low-speed swirling areas are eliminated, and the flow state of the front pool is improved.
Preferably, the deflection angle of the splayed symmetrical bridge pier is determined: the middle bridge pier positioned on the center line of the front pool is not deflected; and C, setting deflection angles of a plurality of groups of symmetrical piers at 5 degrees, 10 degrees and 15 degrees respectively, applying the method of the step A to each combined deflection scheme of the piers according to the sequence of the total deflection angles from small to large, performing CFD calculation on a calculation domain of a downstream water flow field of a pump station, performing post-treatment on a calculation result to obtain streamline and flow velocity distribution in a front pool between two diversion walls, calculating the proportion of the flow velocity in the front pool to the area of a sediment stop flow velocity according to a formula (3), observing the flow direction before an inlet of a water pump inlet channel, determining the optimal deflection angle of each group of symmetrical piers according to the influence rule of the deflection angles of the piers on the inflow direction of the front pool and the area of a low-speed vortex area of the front pool, and further refining the deflection angles of the piers until the proportion of the area of the front pool, which is smaller than the sediment stop flow velocity, is smaller than 1%.
E. The multiple scheme comparison determines the last preferred scheme:
and comparing the ratio of the low-speed areas of the front pool of each of the schemes of the scheme III (1), the scheme III (2) and the scheme …, wherein the ratio of the area of the low-speed area of the front pool is less than 1%, and the bridge pier arrangement scheme for basically eliminating the inflow bias current of the water inlet flow channel of the side unit is the optimal scheme.
The beneficial effects are that: the front end of the front pool of the gate station combined pump station is provided with the sewage disposal bridge, the optimized splayed pier is adopted to guide inflow of the front pool, prevent contraction, adjust the flow direction of water flow to be axial and uniform in flow speed, eliminate large-area vortex low-speed areas at two sides of the front pool and inflow drift of the water inlet flow channel, and achieve the purposes of improving the flow state of the front pool, avoiding sediment accumulation and improving the energy efficiency of the pump station.
Drawings
FIG. 1 is a schematic diagram of a gate station in conjunction with a river course arrangement downstream of a hub, a fluid computing domain, and water surface, middle and bottom layers;
FIG. 2 is a schematic illustration of a gate station in conjunction with fluid computing domain meshing downstream of a hub;
FIG. 3 is a flow line and velocity distribution diagram of a gate station combined with a downstream guide wall of a hub with a length of 30m without a trash disposal bridge;
FIG. 4 is a schematic diagram of a conventional trash removal bridge disposed in a river downstream of a pump station;
FIG. 5 is a schematic view of the front end of the guide wall of the present invention with the dirt removing bridge disposed downstream of the gate station and pump station;
FIG. 6 is a flow line and velocity distribution diagram of a 50m long non-fouling bridge downstream of a gate station junction hub;
FIG. 7 is a flow line and flow velocity distribution diagram of a gate station combined with a guide wall at the downstream of a hinge for 50m in length and an in-line pier trash remover bridge at the front end;
FIG. 8 is a comparison diagram of the ratio of the low-speed area of the front pool of the pump station with 50m 8 schemes of gate station combined with the downstream guide wall of the junction;
FIG. 9 is a downstream flow line and velocity profile for a preferred bridge pier arrangement of the present invention with a minimum pool to pool low velocity ratio (0.4%) in combination with a hub pump station.
Detailed Description
The following further describes the specific embodiment of the present invention by a specific application case, and verifies the provided technical scheme, and main parameters of the gate station combined pump station and the forebay thereof are as follows:
a pump station in Jiangsu province is shown in figure 1, a brake station combination mode is adopted, two ends are provided with a throttle, the middle is provided with a pump station, a 1800HD-10.5 vertical guide vane type mixed flow pump is installed, after updating and reconstruction, a TJ11-HL-05 hydraulic model is selected, the rotating speed is 250r/min, the impeller diameter is 1.68m, 5 sets are provided, 5 main motors with TL1600-20/2150 are matched, the power is 1600kW, and the capacity of a general assembly machine is 8000kW. Single machine design flow 10.8m 3 S, design lift 9.5m, pump station design flow 54m 3 And/s. Two rows of guide walls are arranged on two sides of the downstream pump station section in consideration of the guide effect, the guide walls are perpendicular to the station building, and water level combination is designed by pumping: upstream 21.5m, downstream 12m. The downstream waterway arrangement is as shown in fig. 1.
The method for improving the inflow state of the gate station combined pump station by applying the bridge pier diversion of the trash remover in the case comprises the following steps:
A. gate station combines pump station downstream to set up the guide wall only-scheme one forebay flow CFD computational analysis:
the gate station shown in fig. 1 is combined with a water conservancy junction, the lengths of the diversion walls on the two sides of the downstream of the pump station section are 30m respectively, the mesh division of the downstream flow calculation domain is shown in fig. 2, the mesh number meets the mesh independence condition when reaching 230 ten thousand, and the flow line and the flow velocity distribution of the front pool comprising the downstream of the pump station are obtained through processing the CFD calculation result and are shown in fig. 3.
In the formulas (1) and (2), ρ s ＝2650kg/m 3 ，ρ＝1000kg/m 3 ，g＝9.81m/s 2 D=0.05-0.1 mm, chi Shuishen 4.5.5 m before pumping, substituting into (1) and (2) to obtain sediment stop flow rate U S =0.06-0.1 m/s, take U S =0.1 m/s; silt starting flow velocity U e =0.44-0.55 m/s. When the flow velocity of water flow in the river is lower than the stop flow velocity, sediment accumulation is generated; when the water flow speed is higher than the silt starting flow speed, the deposited silt can be washed away by the water flow.
As shown in FIG. 3, the flow state of the front pool is disturbed when all units of the pump station in the scheme one run, a large low-speed swirling area exists near the inner side of the guide wall, and the width of the large low-speed swirling area almost accounts for 50% of the width of the front pool. The flow velocity of the low-speed vortex area is lower than the sediment stop flow velocity, so that sediment accumulation can be generated; the low-speed areas on the two sides of the front pool are used for back-extruding the main flow, so that the inflow side bias flow of the water inlet flow channels of the units on the two sides is serious except the middle unit.
B. The gate station is combined with the pump station inlet to clean the front end of the downstream guide wall by selecting the layout position of the bridge
The trash remover bridge is arranged on the river course of the downstream river of the pump station, as shown in fig. 4, which is a common practice of the current river pump station; the sewage disposal bridge provided by the invention is arranged at the front ends of the two guide walls of the front pool, as shown in fig. 5, and the front part of the sewage disposal bridge is provided with the sewage disposal grating and the sewage disposal machine, so that sewage in water is prevented from entering the water pump during water pumping, the sewage blocking force loss and the influence of the sewage disposal grating on the pump device are reduced, and meanwhile, the influence on flood discharge is avoided.
The front end of the front pool guide wall is provided with a sewage disposal machine bridge, the outer gate chamber area of the guide wall adopts a bridge column, the diameter of the bridge column is 0.8m, and the interval is 9m; the inner side area of the guide wall adopts an in-line pier wall type pier, the pier length is 10.8m, the thickness is 0.7m, the distance is 4.15m, the head part and the tail part of the pier adopt streamline, 5 piers are arranged in total, and the piers are symmetrically arranged relative to the longitudinal central line of the front pool. Because the bridge pier has a larger length along the water flow direction, the guide wall is actually prolonged to 50m, and the front end part of the guide wall is used as the bridge pier.
C. The front end of the gate station combined pump station downstream guide wall is provided with a trash remover bridge, and the trash remover bridge adopts an in-line pier-scheme II guide to improve the flow state calculation and effect of the front pool:
the front end of the downstream guide wall of the gate station combined pump station is provided with a sewage disposal machine bridge, the sewage disposal machine bridge adopts 5 rows of evenly distributed in-line bridge piers for guiding in the two guide walls, and the arrangement scheme is shown in figure 5, and the length of the guide walls reaches 50m.
For comparison, the length of the downstream guide wall of the pump station in the scheme A is changed into 50m, CFD calculation is applied to treat a front pool streamline and flow velocity distribution without a dirt removing bridge and with the length of the guide wall of 50m as shown in FIG. 6, the widths of the low-speed vortex areas at two sides account for about 50% of the width of the front pool, and the area ratio of the low-speed areas at two sides of the front pool is calculated by using a formula (3) to be larger and reaches 10.7%, so that a main flow area with larger speed exists in the middle of the front pool.
The flow line and flow velocity distribution of the forehearth of the scheme II, which is obtained by calculation and has the length of the guide wall of 50m and the front end provided with the in-line bridge pier, are shown in figure 7. Comparing fig. 7 and fig. 6, it can be seen that after the front end of the front pool is provided with the in-line bridge pier for diversion, the width of the low-speed vortex areas at two sides is reduced to about 30% from 50% of the width of the front pool, the area ratio of the vortex areas of the low-speed areas is reduced to 6.9% from 10.7%, and the flow lines of other areas are basically uniform and parallel except for the small low-speed vortex areas near the inner wall of the diversion wall, so that the flow state of the front pool and the inflow of the water inlet flow passage of the side unit are obviously improved.
D. A method for determining scheme III, namely, arranging a sewage disposal machine bridge at the front end of a downstream guide wall of a gate station combined pump station, wherein the sewage disposal machine bridge is an optimal splayed pier, and improving the flow state effect:
in the scheme II, the front ends of two guide walls at the downstream of the combined pump station of the gate station are provided with in-line pier trash remover bridges, and small-area low-speed areas still exist near the guide walls at the two sides of the front pool. Considering 5 piers of the sewage disposal bridge, the middle pier is kept in line unchanged, and the two side piers are respectively outwards deflected by 6 different angle combinations, together with the first scheme and the second scheme, 8 schemes are provided, as shown in table 1. The arrow direction of the rightmost row in the table is the incoming flow direction, and 8 schemes are arranged from small to large according to the total deflection angle of the bridge pier.
Table 1 different cleaning machine bridge pier schemes
E. Performing CFD calculation on the calculation results by respectively applying the method of the step A to the calculation fields of the downstream flow fields of the pump stations combined by the bridge pier of the scheme III (1) to the scheme III (6) in the table 1, performing post-treatment on the calculation results to obtain the flow velocity and streamline distribution in the front pool between the two diversion walls, calculating the proportion of the area with the flow velocity smaller than the sediment stop flow velocity, observing the flow direction before the inlet of the water inlet flow channel of the water pump, and observing the area proportion of the front pool low-speed vortex area of the pump station of 8 schemes in the scheme I and the scheme II in the step C, wherein the area proportion of the front pool low-speed vortex area of the scheme I without a sewage disposal bridge reaches 10.7 percent as shown in fig. 8; the area proportion of the low-speed vortex area of the second forehearth of the scheme II of the in-line bridge pier is 6.9 percent, and the area proportion is reduced to some extent; the ratio of the low-speed area is the smallest, namely, the scheme III (6) that the deflection angles of the bridge piers at the outermost side and the secondary outer side are 10 degrees, the area ratio of the downstream streamline and the flow velocity distribution is shown as shown in figure 9, the area ratio of the low-speed area is only 0.4 percent and is less than 1 percent, the low-speed area and sediment accumulation in the front pool are basically eliminated, the inflow deflection phenomenon of the side unit is corrected, the flow state of the front pool of the scheme III (6) is the best, the arrangement scheme of the bridge piers of the sewage disposal bridge is the preferred scheme, and the recommended engineering is adopted.
The front end of the front pool of the gate station combined pump station is provided with the sewage disposal bridge, the optimized splayed pier is adopted to guide inflow of the front pool, prevent contraction, adjust the flow direction of water flow to be axial and uniform in flow speed, eliminate large-area vortex low-speed areas at two sides of the front pool and inflow drift of the water inlet flow channel, and achieve the purposes of improving the flow state of the front pool, avoiding sediment accumulation and improving the energy efficiency of the pump station.
Claims (3)
1. A method for improving the inflow state of a gate station combined pump station by using the bridge pier diversion of a sewage disposal machine is characterized by comprising the following steps:
A. providing a scheme I: only a guide wall is arranged at the downstream of the gate station combined pump station; CFD computational analysis was performed on the pre-cell flow of this protocol one:
the stop flow rate of the sediment is the critical flow rate of the sediment from moving to static in the water flow, and the calculation formula is as follows:
wherein: u (U) S Stopping the flow rate of the sediment, m/s; ρ s Is of sediment density, kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the ρ is the density of clear water, kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the g is gravity acceleration, m/s 2 The method comprises the steps of carrying out a first treatment on the surface of the d is the median diameter of the suspended sand, m;
the starting flow velocity of the sediment is the critical flow velocity of the sediment on the river bed surface under the action of the water flow when the sediment is transferred from rest to motion, and the calculation formula is as follows:
wherein: u (U) e Starting the flow rate for silt, m/s; h is the average water depth, m; ρ s Is of sediment density, kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the ρ is the density of clear water, kg/m3; g is gravity acceleration, m/s 2 The method comprises the steps of carrying out a first treatment on the surface of the d is the median diameter of the suspended sand; m;
taking the straight river channel flow section of the position 5-8 times the water depth of the downstream diffusion section of the gate station as an inlet section, and taking the straight section of the water inlet channels of all operation units of the pump station as an outlet section as a water body part calculation domain, wherein the calculation domain also comprises an air domain with the height of 2m above the water surface; performing unstructured grid division on a calculation domain, performing grid encryption on an inlet and an outlet of the calculation domain and a water surface, and verifying that the number of grids meets independence;
calculating the given mass flow of an inlet of the domain, the given mass flow of an outlet, and setting a solid wall boundary as a non-slip wall surface;
the calculation model takes the gravity influence into consideration, CFD calculation is carried out on water flow in a calculation area at the downstream of the pump station, the water surface is captured by a VOF method, the calculation result is subjected to post-treatment, the water flow velocity and streamline distribution of the calculation area including the front pool of the pump station are obtained, the flow state in the front pool is observed, the position and the area of a sediment accumulation area in the front pool are judged by using a formula (1), and the position and the area of the area where sediment accumulation cannot be flushed away in the front pool are judged by using a formula (2); the severity of the forehearth silt deposition is expressed as a percentage of the deposition area to the forehearth area, and the ratio of the low-speed deposition area of the forehearth is calculated by applying the formula (3):
wherein: lambda is the area proportion of a low-speed area with the flow velocity of the front pool lower than the stop flow velocity of sediment; a is that l Is the area of a low-speed zone of a front pool at the inner side of the guide wall, m 2 ；A t Is the total area of the front pool on the inner side of the guide wall, m 2 ；
B. The gate station is arranged at the front end of the downstream guide wall in combination with the pump station inlet trash remover bridge:
arranging a trash remover bridge between the two guide wall heads of the front pool of the pump station, installing trash racks and trash removers, preventing dirt in water from entering the water pump and being removed in time when pumping water, avoiding the influence on the flood discharge of the throttle valve, simultaneously, guiding by using the bridge pier of the trash remover, adjusting the flow direction of water flow to be axial and uniform in flow speed, and improving the flow state of the front pool;
C. providing a scheme II: the front end of the gate station combined pump station downstream guide wall is provided with a sewage disposal machine bridge, and the sewage disposal machine bridge adopts an in-line pier;
the front end of the guide wall is provided with an in-line pier which is parallel to the guide wall along the main flow direction;
performing CFD calculation on a downstream water flow calculation domain of the pump station by applying the method of the step A, performing post-treatment on a calculation result to obtain streamline and flow velocity distribution in a front pool between two guide walls, calculating the proportion of the flow velocity smaller than the area of a sediment stop flow velocity region, and observing the flow direction before the inlet of a water inlet flow channel of the water pump;
D. providing a scheme III: the front end of the gate station combined pump station downstream guide wall is provided with a sewage disposal machine bridge, and the sewage disposal machine bridge adopts an optimal splayed pier:
adopting a preferable splayed pier to guide water flow to two sides of the front pool, adjusting the water flow direction of the front pool to be axial and uniform in flow speed, eliminating a low-speed swirling area and improving the flow state of the front pool;
preferably, the deflection angle of the splayed symmetrical bridge pier is determined: the middle bridge pier positioned on the center line of the front pool is not deflected; setting deflection angles of a plurality of groups of symmetrical piers at 5 degrees, 10 degrees and 15 degrees respectively, applying the method of the step A to each combined deflection scheme of the piers according to the sequence from small total deflection angles to large total deflection angles, carrying out CFD calculation on a calculation domain of a downstream water flow field of a pump station, carrying out post-treatment on a calculation result to obtain streamline and flow velocity distribution in a front pool between two diversion walls, calculating the proportion of the flow velocity in the front pool to the area of a sediment stop flow velocity according to a formula (3), observing the flow direction before an inlet of a water pump inlet channel, determining the optimal deflection angle of each group of symmetrical piers according to the influence rule of the deflection angles of the piers on the inflow direction of the front pool and the area of a low-speed vortex area of the front pool, and further refining the deflection angles of the piers until the proportion of the area of the front pool, which is smaller than the sediment stop flow velocity, is smaller than 1 percent of the area of the front pool;
E. the multiple scheme comparison determines the last preferred scheme:
comparing the low-speed area proportion of the front pool in the first scheme, the second scheme and the third scheme, and selecting the bridge pier arrangement scheme with the area proportion of the low-speed area of the front pool being less than 1% and the inflow drift of the water inlet flow channel of the side unit being basically eliminated as the optimal scheme.
2. The method for improving the inflow state of a gate station combined pump station by using the diversion of the bridge pier of the trash remover according to claim 1, wherein the bridge pier of the trash remover in the step B adopts a pier wall type bridge pier to ensure the diversion effect; the head and tail of the bridge pier are streamline so as to reduce flow resistance; the plane of the main body part of the bridge pier adopts a rectangle; the bridge piers between the two guide walls are symmetrically arranged according to the longitudinal center line of the front pool so as to ensure symmetrical flow.
3. The method for improving the inflow state of a gate station combined pump station by using the diversion of a bridge pier of a trash remover according to claim 1, wherein the splayed bridge pier in the step D takes the horizontal longitudinal center line of a front pool as a reference, the in-line bridge piers symmetrically distributed about the longitudinal center line of the front pool in the step C deflect outwards by a certain angle around the vertical center line of the bridge pier along the water flow direction, the deflection angles of the two symmetrical bridge piers on two sides are equal and opposite, the left bridge pier deflects clockwise when the bridge pier facing the inflow direction is seen from top to bottom, the right bridge pier deflects anticlockwise, and the symmetrical bridge piers are distributed in a splayed shape.
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