A Method for Determining the Basic Operating Conditions of the Hydraulic Transient Process in a Long-Distance Fully Pressurized Water Conveyance System

Abstract

The present invention provides a method for formulating the basic conditions of the hydraulic transient process of a long-distance fully pressurized water conveyance system, which includes the following steps: determining the pipeline size according to the water supply demand; identifying the key nodes of the pressure fluctuation source and the key nodes for pressure stabilization; segmenting the pressurized water conveyance system according to the positions of the key nodes for pressure stabilization, and further dividing each pipeline section into gravity pipeline sections and pumping pipeline sections according to the water supply energy source; formulating the adjustment principle for the pressure fluctuation source nodes in the basic conditions of the transient process; analyzing the transient process conditions of the pumping pipeline sections and the gravity pipeline sections, and adjusting the designed bearing pressure of the pipeline according to the analysis results; outputting the pipeline characteristic table of the pressurized water conveyance system according to the pressure regulation results, and compiling the adjustment guidance manual for the hydraulic transient process. Without missing the relatively unfavorable conditions, the present invention greatly reduces the number of basic conditions of the transient process of multiple water diversion outlets, making up for the deficiency of the empirical method in determining the transient process conditions, which is prone to missing unfavorable conditions, and reducing the workload of the transient process analysis in the design stage of the pressure pipeline system.

Description

Technical Field

[0001] The invention belongs to the field of long-distance water diversion and regulation engineering and municipal water supply engineering, and specifically relates to a method for formulating basic working conditions of a hydraulic transition process of a long-distance fully pressurized water delivery system. Background Art

[0002] With the development of the economy, the water demand for industrial and agricultural production continues to increase, and the contradiction of spatial imbalance of water resources has become increasingly prominent. As an important means of regulating regional water resources, the long-distance pressurized water transmission system is increasingly favored by water diversion projects due to its high water transmission efficiency and low environmental impact. The main feature of the long-distance fully pressurized water transmission system is that any adjustment of any water diversion outlet or pump station unit will have an impact on the entire system. In the design stage, the main difficulty is to find the more unfavorable working conditions among the many possible adjustment combinations for research, and to ensure the safety of the operation period by adjusting the structural design strength, optimizing the adjustment process and the layout of the pressure regulating facilities. Traditionally, the formulation of unfavorable working conditions mainly depends on the engineering experience of designers, and some unfavorable working conditions are easy to be missed. If the more unfavorable working conditions are not found in the design stage, the structural design strength is low or there are loopholes in the operation and scheduling rules, and there are greater safety risks during system operation. The present invention provides a method for formulating the basic operating conditions of the hydraulic transition process of a fully pressurized water delivery system, which greatly reduces the number of basic operating conditions of the transition process of multiple water outlets without omitting more unfavorable operating conditions. This not only makes up for the deficiency that the empirical method for determining the transition process conditions is prone to omitting unfavorable conditions, but also reduces the workload of transition process analysis in the design and operation stages of the pressure pipeline system. Summary of the invention

[0003] In order to overcome the problem that the traditional method for formulating the working conditions of the hydraulic transition process of a fully pressurized system relies on experience and is prone to omission of unfavorable working conditions, the present invention provides a method for formulating the basic working conditions of the hydraulic transition process of a long-distance fully pressurized water delivery system, comprising the following steps:

[0004] Determine pipe sizes based on water supply needs;

[0005] Determine the key nodes of pressure fluctuation sources and key nodes of pressure stabilization;

[0006] The pressurized water delivery system is segmented according to the location of the key nodes for stabilizing pressure, and each pipe section is further divided into a gravity pipe section and a pumping pipe section according to the water supply energy source;

[0007] Formulate the adjustment principle of the nodes of the pressure fluctuation source under the basic working condition of the transition process;

[0008] Analyze the transition process conditions of the pumping section and the gravity section, and adjust the hydraulic parameters of the pipeline design pressure bearing and pressure regulating facilities according to the analysis results;

[0009] Output the pipeline characteristic table of the pressurized water supply system based on the adjustment results, and compile a guidance manual for the hydraulic transition process regulation.

[0010] Furthermore, the pipeline size is specifically determined according to the water supply demand:

[0011] Obtain the characteristic water level of the reservoir and the design roughness of the pipeline;

[0012] According to the characteristic water level of the reservoir and the design roughness of the pipeline, the constant flow calculation formula of the pressure pipeline is used to verify the pipeline flow capacity, and the pipeline size and water pump head are adjusted to meet the water demand of each water outlet.

[0013] Furthermore, the key nodes of the pressure fluctuation source include: a water pump and a large flow regulating valve;

[0014] The key pressure stabilization nodes include: reservoirs and large-volume pressure regulating wells.

[0015] Furthermore, the basic working condition pressure fluctuation source node adjustment principle is specifically as follows:

[0016] When adjusting a key node of a pressure fluctuation source, keep the valve opening or pump head of other nodes unchanged, and adjust multiple nodes through the front and back combination of multiple basic working conditions;

[0017] Gravity flow sections need to be analyzed simultaneously if they affect each other, while pumping sections can be analyzed independently.

[0018] Furthermore, the transition process conditions of the pumping pipe section are specifically as follows:

[0019] 1) Fluctuations caused by the self-regulation of the pipe section, that is, when the water level in the forebay of the pumping station is horizontal, the basic working conditions of the pumping pipe section revolve around the combination of the main water diversion outlet of the pipe section and the pump regulation;

[0020] 2) Fluctuations caused by adjustments in other pipe sections, that is, when the water level in the forebay of the pumping station is affected by other pipe sections, the basic operating conditions of the pumping section revolve around the impact of the water level fluctuation in the forebay on the pipeline pressure under different water supply combinations of the section, and determine the allowable fluctuation amplitude and speed of the water level in the forebay.

[0021] Furthermore, the transition process conditions of the gravity flow section are specifically as follows:

[0022] The basic operating conditions of the transition process of the gravity pipe section are determined based on the different operating water levels of the reservoir, the opening and closing status of the key nodes of the pressure fluctuation source of the pipe section, and the arrangement and combination of whether the pumping pipe section is supplying water. The water level fluctuation in the front pool of the pumping pipe section caused by the adjustment of the gravity pipe section during the transition process shall not exceed the fluctuation amplitude and speed permitted in the transition process conditions of the pumping pipe section.

[0023] Furthermore, the pumping pipe section only includes two situations: full load water supply and no water supply.

[0024] Furthermore, the pipeline pressure is adjusted according to the analysis results as follows:

[0025] By optimizing the opening and closing process, adjusting the pipeline design strength, and adjusting the pressure regulating facilities until the pipeline pressure is within a safe range.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] The present invention identifies the key nodes of the pressure fluctuation source and the key nodes of the pressure stabilization, limits the adjustment to only one of the key nodes of the pressure fluctuation source in the same basic working condition, simplifies the complex working condition adjustment of multiple water outlets into the front and back combined adjustment of multiple basic working conditions, and formulates the working condition from the perspective of permutation and combination, thereby ensuring that the proposed working condition can cover all possible adverse working conditions.

[0028] The present invention divides the long-distance complex pressurized water transmission system into gravity pipe sections and pumping pipe sections according to the pressure fluctuation sources of the fully pressurized water transmission system, the pressure wave propagation characteristics of the pressurized pipe sections and the pressure buffering mechanism of the pressure stabilizing nodes, and formulates their basic operating condition combinations according to the differences in pressure bearing size and fluctuation change rate between the two types of pipe sections, thereby greatly reducing the number of basic operating conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings generally illustrate various embodiments by way of example and not limitation, and together with the description and claims, serve to illustrate the embodiments of the invention. Where appropriate, the same reference numerals are used throughout the drawings to refer to the same or similar parts. Such embodiments are illustrative and are not intended to be exhaustive or exclusive embodiments of the present apparatus or method.

[0030] Figure 1 Draft a flow chart for the basic working conditions of the transition process of the pressurized water supply system;

[0031] Figure 2 Schematic diagram of long distance pressurized water transmission system pipeline. DETAILED DESCRIPTION

[0032] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0033] The embodiment of the present invention is as follows Figure 2Take the long-distance pressurized water transmission system shown as an example. The entire water transmission system draws water from the reservoir, and a large-volume pressure regulating well (0# pressure regulating well) is set in the middle of the system. There are 4 branches in total. Branch 1 connects the reservoir and the 0# pressure regulating well; branch 2 connects the 0# pressure regulating well and user 3; branch 3 connects the 0# pressure regulating well and user 10, passing through the 1# water pump (or gravity flow regulating valve) and the middle flow regulating valve. When the water level of the reservoir is high and the overall flow of other branches is small, branch 3 can supply water through the gravity flow regulating valve without turning on the water pump; branch 4 connects the 0# pressure regulating well and user 15, passing through the 2# water pump. There are 15 water diversion outlets (users) in total, including 7 large-flow water diversion outlets (the design flow of the water diversion outlet is greater than 1m 3 / s), accounting for 94.7% of the total water supply flow. In the figure, a flow regulating valve is set in front of each of the 15 water outlets. The user icon is the design flow of the water outlet, and the water outlet with a shaded flow is the large flow outlet.

[0034] Traditionally, when designing the transition process conditions, only the opening and closing effects of large flow diversion outlets are considered. As shown in Table 1, if all 7 outlets are initially open, one diversion outlet is closed (7 to 6); if 6 diversion outlets are initially open, the remaining one is opened (6 to 7); and so on. There are 14 types of conditions in total. The reservoir water level is considered as high, medium and low water levels. Theoretically, the number of conditions is as high as 2688. If the influence of roughness uncertainty is taken into account, the number of conditions can reach tens of thousands, which is difficult to complete in the design stage. If the basic conditions are reduced based on experience, there is a large randomness and it is easy to miss the less favorable conditions.

[0035] Table 1 Theoretical operating conditions

[0036]

[0037] According to the method provided by the present invention, the basic working condition formulation includes the following steps:

[0038] 1. Determine the pipe size according to water supply demand

[0039] According to the characteristic water level of the reservoir and the design roughness of the pipeline, the constant flow calculation formula of the pressure pipeline is used to verify the pipeline flow capacity. In this case, the pipeline size and pump head are adjusted according to the calculation results so that each branch pipeline can meet the water demand of each water outlet.

[0040] 2. Determine the key nodes of pressure fluctuation sources and key nodes of pressure stabilization

[0041] In this case, the key nodes of the pressure fluctuation source are two pump stations, seven large-flow water diversion valves and the middle flow regulating valve in branch line 3. The regulation of these 10 key nodes will have a great impact on the pressure system. The key nodes for pressure stabilization are reservoirs and pressure regulating wells. Among them, the diameter of the 0# pressure regulating well is 20m and the regulating volume is large, while the diameter of other pressure regulating wells is only 6.8m and the regulating volume is small, so they are not listed as key nodes for pressure stabilization.

[0042] 3. Divide the pipe sections of the fully pressurized water supply system into gravity sections and pumping sections

[0043] The pressure of the gravity pipe section is obviously affected by the reservoir, and its operating pressure varies widely; while from the perspective of water pump energy saving, the pump head of the pump section can be adjusted according to the water supply demand, and the operating pressure is usually stable within a small range. In this case, the entire water pipeline is divided into 4 sections through the 0# pressure regulating well, of which branch lines 1 and 2 are gravity pipe sections, branch line 4 is a pumping pipe section, and branch line 3 is a gravity pipe section under a few working conditions and a pumping pipe section under most working conditions.

[0044] 4. Formulate the adjustment principle of the node of the pressure fluctuation source under the basic working condition of the transition process

[0045] The adjustment principle in this example is: in a basic working condition, the 10 key nodes of the pressure fluctuation source cannot be adjusted at the same time, and the hydraulic transition process state is divided into the initial state, the adjustment state and the target state, and the adjustment state is divided into three stages: pre-adjustment, adjustment and post-adjustment. Pre-adjustment includes adjusting the pump station output to meet the water supply capacity of the target state and fine-tuning the bypass valve opening to increase the safety margin of subsequent adjustments; adjustment refers to adjusting the proposed additional or closed water outlets to the target opening; post-adjustment is to fine-tune each water outlet to its respective target water supply state.

[0046] 5. Plan the transition process conditions of the pumping pipe section and conduct analysis

[0047] According to the aforementioned pipe section division and key node adjustment principles, the basic working conditions of branch line 3 during pumping are mainly carried out around the opening and closing combination of flow regulating valves 4, 8 and 10. The working condition combination is shown in Table 2. For the opening working condition, the opening process is a pressure reduction process for the pipeline. Before opening, the pipeline pressure must be increased to a certain value (with the water level of the 1# pressure regulating well as the pressure reference point) by the water pump, and then the flow regulating valve is opened. Similarly, when closing the flow regulating valve, the water pump head must be lowered (the water level of the low pressure regulating well is lowered), and then the flow regulating valve is closed. The water pump head adjustment ensures that no matter what the water level of the 0# pressure regulating well is, the pressure of branch line 3 pipeline varies within a small range. The working condition table is formulated in a permutation and combination manner to ensure that some unfavorable working conditions will not be missed.

[0048] Branch line 4 is mainly carried out around the opening and closing combination of flow regulating valves 12 and 15, and its operating condition combination is shown in Table 3. Taking the water level of 2# pressure regulating well as the pressure reference point, its regulation rule is basically consistent with the pumping condition of branch line 3.

[0049] Table 2 Basic operating conditions of branch line 3 (pumping)

[0050]

[0051] Table 3 Basic operating conditions of branch line 4

[0052]

[0053] 6. Formulate the transition process conditions of the gravity flow section and conduct analysis

[0054] Since the pressure of the gravity pipe section is significantly affected by the water level of the reservoir, the pressure characteristics of the pipeline must be considered from the perspectives of high, medium and low water levels when formulating the transition process conditions. The opening of the regulating valve is a pressure-reducing condition. From the perspective of unfavorable conditions, the low water level of the reservoir is taken when the working condition is formulated. The closing of the regulating valve is a pressure-raising condition. The high water level of the reservoir is taken when the working condition is formulated. In addition, if the pump station loses power when branch line 1 and branch line 2 are at medium and high water levels, there is a risk of overpressure. Therefore, the power-off condition of the pump station must be considered when pumping water for branch line 3 or branch line 4. The basic working condition tables of branch line 1 and branch line 2 are shown in Table 4 and Table 5.

[0055] When branch line 3 is supplying water by gravity, the reservoir must be at a medium-high water level, and due to the pressure requirements of the pipe section, the pipeline design pressure after the middle flow regulating valve is relatively small. The middle flow regulating valve must be used to adjust the downstream pressure and then adjust the user flow regulating valve to supply water.

[0056] Table 4 Basic operating conditions of branch line 1

[0057]

[0058] Table 5 Basic operating conditions of branch line 2

[0059]

[0060] Table 6 Basic operating conditions of branch line 3 (self-flow)

[0061]

[0062] 7. After analyzing the system transition process for the proposed operating conditions in steps 5 and 6, optimize the opening and closing process, adjust the pipeline design strength, adjust the pressure regulating facilities, etc. until the pipeline pressure is within a safe range.

[0063] 8. Output the pipeline characteristic table of the pressurized water delivery system and compile a hydraulic transition process adjustment guide. This step is basically the same as the traditional method of outputting results, so it will not be described in detail here.

[0064] According to the propagation mechanism of water hammer waves, the present invention divides the fully pressurized water delivery system into gravity pipe sections and pumping pipe sections, and formulates basic working conditions to carry out transition process analysis according to the pressure increase and pressure reduction rules of the pressure fluctuation source and the arrangement and combination of key nodes, which can greatly reduce the number of working condition combinations of the fully pressurized water delivery system without missing any adverse working conditions. In this example, there are 2688 working condition combinations in theory, and the working condition combinations are reduced to 116 groups (Tables 2 to 6) after the method provided by the present invention is adopted, which not only ensures the safety of the project, but also reduces the workload of hydraulic transition process analysis.

[0065] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for formulating basic working conditions of hydraulic transition process of long-distance fully pressurized water delivery system, characterized in that: The following steps are involved: Determine pipe sizes based on water supply needs; Determine the key nodes of pressure fluctuation sources and key nodes of pressure stabilization; The pressurized water delivery system is segmented according to the location of the key nodes for stabilizing pressure, and each pipe section is further divided into a gravity pipe section and a pumping pipe section according to the water supply energy source; Formulate the adjustment principle of the nodes of the pressure fluctuation source under the basic working condition of the transition process; Analyze the transition process conditions of the pumping section and the gravity section, and adjust the hydraulic parameters of the pipeline design pressure bearing and pressure regulating facilities according to the analysis results; Output the pipeline characteristic table of the pressurized water supply system according to the adjustment results, and compile the hydraulic transition process adjustment guidance manual; The basic working condition pressure fluctuation source node adjustment principle is specifically as follows: When adjusting a key node of a pressure fluctuation source, keep the valve opening or pump head of other nodes unchanged, and adjust multiple nodes through the front and back combination of multiple basic working conditions; Gravity pipe sections need to be analyzed simultaneously if they affect each other, while pumping pipe sections are analyzed independently; The specific transient process conditions of the pumping pipe section are as follows: 1) Fluctuations caused by the self-regulation of the pipe section, that is, when the water level in the forebay of the pumping station is constant, the basic working conditions of the pumping pipe section revolve around the combination of the main water diversion outlet of the pipe section and the pump regulation; 2) Fluctuations caused by regulation of other pipe sections, that is, when the water level in the forebay of the pumping station is affected by other pipe sections, the basic working condition of the pumping pipe section is based on the influence of the water level fluctuation in the forebay on the pipeline pressure under different water supply combinations of the pipe section, and determines the allowable fluctuation amplitude and speed of the water level in the forebay; The specific transition process conditions of the gravity flow section are as follows: The basic operating conditions of the transition process of the gravity pipe section are determined based on the different operating water levels of the reservoir, the opening and closing status of the key nodes of the pressure fluctuation source of the pipe section, and the arrangement and combination of whether the pumping pipe section is supplying water. The water level fluctuation in the front pool of the pumping pipe section caused by the adjustment of the gravity pipe section during the transition process shall not exceed the fluctuation amplitude and speed permitted in the transition process conditions of the pumping pipe section.

2. The method for formulating basic operating conditions of hydraulic transition process of long-distance fully pressurized water delivery system according to claim 1 is characterized in that: The specific pipe sizes proposed based on water supply demand are: Obtain the characteristic water level of the reservoir and the design roughness of the pipeline; According to the characteristic water level of the reservoir and the design roughness of the pipeline, the constant flow calculation formula of the pressure pipeline is used to verify the pipeline flow capacity, and the pipeline size and water pump head are adjusted to meet the water demand of each water outlet.

3. The method for formulating basic operating conditions of hydraulic transition process of long-distance fully pressurized water delivery system according to claim 1 is characterized in that: The key nodes of the pressure fluctuation source include: a water pump and a large flow regulating valve; The key pressure stabilization nodes include: reservoirs and large-volume pressure regulating wells.

4. The method for formulating basic operating conditions of hydraulic transition process of long-distance fully pressurized water delivery system according to claim 1 is characterized in that: The pumping pipe section only includes two conditions: full load water supply and no water supply.

5. The method for formulating basic operating conditions of hydraulic transition process of long-distance fully pressurized water delivery system according to claim 1 is characterized in that: According to the analysis results, the pipeline design pressure is adjusted as follows: By optimizing the opening and closing process, adjusting the pipeline design strength, and adjusting the pressure regulating facilities until the pipeline pressure is within a safe range.

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