CN111736488A - Method for automatically searching flow instability boundary of parallel channel - Google Patents
Method for automatically searching flow instability boundary of parallel channel Download PDFInfo
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- CN111736488A CN111736488A CN202010628631.3A CN202010628631A CN111736488A CN 111736488 A CN111736488 A CN 111736488A CN 202010628631 A CN202010628631 A CN 202010628631A CN 111736488 A CN111736488 A CN 111736488A
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- 238000000034 method Methods 0.000 title claims abstract description 18
- 230000001052 transient effect Effects 0.000 claims abstract description 11
- 230000010349 pulsation Effects 0.000 claims abstract description 6
- 238000012544 monitoring process Methods 0.000 claims description 3
- 238000002474 experimental method Methods 0.000 abstract description 10
- 230000010355 oscillation Effects 0.000 description 6
- 230000001105 regulatory effect Effects 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000009835 boiling Methods 0.000 description 2
- 230000000295 complement effect Effects 0.000 description 2
- 238000012512 characterization method Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 238000005057 refrigeration Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 230000005514 two-phase flow Effects 0.000 description 1
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B17/00—Systems involving the use of models or simulators of said systems
- G05B17/02—Systems involving the use of models or simulators of said systems electric
Abstract
The invention discloses a method for automatically searching a flow instability boundary of a parallel channel, which comprises the following steps of measuring flow pulsation amplitude, judging a threshold value, changing a valve opening set value: if the difference between the inlet valve flow transient value and the time average value is less than or equal to 10%, increasing a valve opening set value, and adjusting the valve opening through an automatic control algorithm to reach the set value; if the difference between the transient inlet valve flow value and the time average value is larger than 10%, the opening of the inlet valve is finely adjusted through an automatic control algorithm so that the mass flow rate reaches a set value. The technology utilizes an automatic control technology to automatically and quickly search the flow instability boundary of the parallel channel in an experiment, solves the problem that when the number of parallel pipes or channels is too large, the flow instability boundary is difficult to find by manually adjusting the inlet resistance of the parallel pipes or channels, improves the efficiency of searching the flow instability boundary of the parallel channel, reduces the working load of personnel, and saves the experiment cost.
Description
Technical Field
The invention belongs to the technical field of thermal hydraulic control, and particularly relates to the field of automatic parallel channel searching flow.
Background
Flow instability refers to flow pulsations of constant or varying amplitude. The boiling channel causes the density of the mixture to change due to the change of the vapor content, which may cause two-phase flow pulsation. Flow instabilities can occur in equipment having a large number of parallel tubes or channels in industrial systems such as boiler waterwalls, reactors, petroleum, chemical, refrigeration, etc. The flow instability is mainly manifested in the following: (1) mechanical vibration and thermal stress alternation caused by flow pulsation accelerate fatigue of equipment; (2) controlling interference; (3) the local heat transfer characteristics are affected, causing the boiling crisis to occur in advance. In order to avoid flow instability, it must be predicted and analyzed at the plant design stage in order to take effective precautions. The study methods of the flow instability include an experimental method and a theoretical analysis method. The theoretical analysis method is economical and convenient, is less limited by conditions, but has poor accuracy. The experimental method has reliable results but large investment. These two methods complement each other and complement each other, and usually, in order to verify the result of theoretical analysis, experimental studies must be performed.
In industrial systems, flow instability is inhibited by adding resistance to the parallel tubes or channel inlets, where too little inlet resistance will not effectively inhibit flow instability, and too much inlet resistance will result in greater head loss. It becomes important to find the boundaries of flow instabilities and thus determine the inlet resistance of parallel tubes or channels. In the experimental process, the inlet resistance is often adjusted through the adjusting valve in front of the parallel pipes or the channels, but when the number of the parallel pipes or the channels is too large, due to mutual influence among the channels, the flow distribution of the whole system is influenced unpredictably by manually adjusting the inlet resistance one by one, so that the flow instability boundary is difficult to find by manually adjusting the inlet resistance of the parallel pipes or the channels one by one through experience. The patent provides a method for automatically searching for a parallel channel flow instability boundary by using an automatic control technology, and the method can greatly improve the efficiency of searching for the parallel channel flow instability boundary in an experiment and reduce the workload of personnel.
Disclosure of Invention
The patent aims to provide a method for automatically searching for a flow instability boundary of a parallel channel in an experiment by utilizing an automatic control technology, and the method solves the problem that when the number of parallel pipes or channels is too large, the flow instability boundary is difficult to find by manually adjusting the inlet resistance of the parallel pipes or channels, improves the efficiency of searching for the flow instability boundary of the parallel channel in the experiment and reduces the working load of personnel.
A method for automatically searching for a parallel channel flow instability boundary comprises the following steps:
measuring the flow pulsation amplitude: opening an inlet valve of a pipe or a channel, gradually opening the opening of the inlet valve from small to large, and monitoring the flow of the inlet valve;
judging a threshold value: comparing the difference between the flow transient value of the inlet valve and the time-average value with a specified value;
changing the set value of the valve opening: if the difference between the inlet valve flow transient value and the time average value is less than or equal to a specified value, increasing a valve opening set value, and adjusting the valve opening through an automatic control algorithm to reach the set value; if the difference between the inlet valve flow transient value and the time average value is larger than a specified value, the opening of the inlet valve is finely adjusted through an automatic control algorithm so that the mass flow rate reaches a set value;
the specified value may be selected to be one of 10%, 8%, or 5%.
This patent utilizes automatic control technique automatic quick search parallel channel flow instability border in the experiment, when solving parallel pipe or passageway quantity too much, the artificial difficulty of adjusting parallel pipe or passageway entry resistance in order to look for flow instability border has promoted the efficiency of searching parallel channel flow instability border, reduces personnel's work load, saves the experiment cost.
Drawings
FIG. 1 is a schematic diagram of a parallel channel flow instability boundary experiment;
FIG. 2 is a schematic diagram illustrating a method for automatically searching for a boundary of a flow instability of a parallel channel by using an automatic control technique;
FIG. 3 is a method for implementing automatic searching for parallel channel flow instability boundary by MATLAB/SIMULINK platform;
FIG. 4 is a flow oscillation characterization module;
FIG. 5 is a parallel pipe or channel inlet regulating valve opening given value module;
fig. 6 is an automatic regulating module for the opening of the parallel pipe or channel inlet regulating valve.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
How the method proposed by this patent is carried out is explained below on the MATLAB/SIMULINK platform.
The overall implementation is shown in fig. 3.
The function of each module is explained separately below.
The module shown in FIG. 4 determines the magnitude of flow instability by comparing the transient flow value to the percentage deviation from the time average for characterizing the magnitude of flow oscillations.
FIG. 5 is a block diagram of the determination of the given value of the opening of the inlet regulating valve of a parallel pipe or channel, the core of which is a selector that keeps the given value of the valve opening constant when the flow oscillations are greater than a threshold value and that increases the given value of the valve opening to reduce the inlet resistance when the flow oscillations are less than the threshold value, in order to find the stability margin.
Fig. 6 is a module for automatically adjusting the opening degree of an inlet adjusting valve of a parallel pipe or channel, the core of the module is a selector, when the flow oscillation is larger than the threshold value, the system is still in an unstable state, the adjusting strategy is to use a PID algorithm to adjust the opening degree of the inlet valve so that the flow value of each pipe or channel is equal to the flow set value, and the flow set value is calculated according to the total flow and the flow area of the pipe or channel so as to ensure that the mass flow rate of each pipe or channel is consistent. When the flow oscillation is smaller than the threshold value, the system is in a stable state, the opening degree of the inlet valve can be increased to continuously search for a stable boundary, and the adjustment strategy at the moment is to adjust the opening degree of the inlet valve to follow the change of the valve opening degree set value by using a PID algorithm.
To summarize, the method for automatically searching the flow instability boundary of the parallel channel proposed by the present patent is:
(1) the inlet valve opening of each pipe or channel is increased from a smaller value until the flow can not be maintained stable under a certain opening, and the inlet resistance corresponding to the opening is the boundary of the flow instability.
(2) And continuously monitoring the inlet flow under a certain opening degree of the inlet valve of the pipe or the channel, if the difference between the transient value of the inlet flow and the time average value is within a certain range, which indicates that the flow is stable under the opening degree of the valve, increasing the set value of the opening degree of the valve, and adjusting the opening degree of the valve through an automatic control algorithm to reach the set value. If the difference between the transient inlet flow value and the time average value exceeds a certain range, which indicates that the flow is unstable under the valve opening, the valve opening is finely adjusted through an automatic control algorithm so as to enable the mass flow rate to reach a set value. Generally, maintaining the same mass flow rate per tube or channel maximizes flow stability.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include such modifications and variations. The foregoing examples or embodiments are merely illustrative of the present invention, which may be embodied in other specific forms or in other specific forms without departing from the spirit or essential characteristics thereof. The described embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. The scope of the invention should be indicated by the appended claims, and any changes that are equivalent to the intent and scope of the claims should be construed to be included therein.
Claims (1)
1. A method for automatically searching for a parallel channel flow instability boundary is characterized by comprising the following steps:
measuring the flow pulsation amplitude: opening an inlet valve of a pipe or a channel, gradually opening the opening of the inlet valve from small to large, and monitoring the flow of the inlet valve;
judging a threshold value: comparing the difference between the flow transient value of the inlet valve and the time-average value with a specified value;
changing the set value of the valve opening: if the difference between the inlet valve flow transient value and the time average value is less than or equal to a specified value, increasing a valve opening set value, and adjusting the valve opening through an automatic control algorithm to reach the set value; if the difference between the inlet valve flow transient value and the time average value is larger than a specified value, the opening of the inlet valve is finely adjusted through an automatic control algorithm so that the mass flow rate reaches a set value;
the specified value may be selected to be one of 10%, 8%, or 5%.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010628631.3A CN111736488A (en) | 2020-07-02 | 2020-07-02 | Method for automatically searching flow instability boundary of parallel channel |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010628631.3A CN111736488A (en) | 2020-07-02 | 2020-07-02 | Method for automatically searching flow instability boundary of parallel channel |
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| CN202010628631.3A Pending CN111736488A (en) | 2020-07-02 | 2020-07-02 | Method for automatically searching flow instability boundary of parallel channel |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20010004903A1 (en) * | 1999-04-16 | 2001-06-28 | Tadahiro Ohmi | Parallel divided flow-type fluid supply apparatus, and fluid-switchable pressure-type flow control method and fluid-switchable pressure-type flow control system for the same fluid supply apparatus |
| US20040226615A1 (en) * | 2003-02-24 | 2004-11-18 | Smc Corporation | Flow rate control device |
| CN107436274A (en) * | 2017-07-31 | 2017-12-05 | 中国核动力研究设计院 | Parallel port Density wave oscillation recognition methods under the conditions of multiple flow pulsation superposition |
| JP2018150882A (en) * | 2017-03-14 | 2018-09-27 | 株式会社デンソー | Fluid control device |
-
2020
- 2020-07-02 CN CN202010628631.3A patent/CN111736488A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20010004903A1 (en) * | 1999-04-16 | 2001-06-28 | Tadahiro Ohmi | Parallel divided flow-type fluid supply apparatus, and fluid-switchable pressure-type flow control method and fluid-switchable pressure-type flow control system for the same fluid supply apparatus |
| US20040226615A1 (en) * | 2003-02-24 | 2004-11-18 | Smc Corporation | Flow rate control device |
| JP2018150882A (en) * | 2017-03-14 | 2018-09-27 | 株式会社デンソー | Fluid control device |
| CN107436274A (en) * | 2017-07-31 | 2017-12-05 | 中国核动力研究设计院 | Parallel port Density wave oscillation recognition methods under the conditions of multiple flow pulsation superposition |
Non-Patent Citations (4)
| Title |
|---|
| 熊万玉等: "基于一维漂移流模型的并联矩形双通道密度波流动不稳定性数值模拟", 《原子能科学技术》 * |
| 王畅等: "摇摆条件下强迫循环流量脉动特性分析", 《核动力工程》 * |
| 王畅等: "摇摆运动对强迫循环沸腾流动特性的影响", 《核动力工程》 * |
| 管华盛等: "汽心对汽心泵供油特性的影响研究", 《中国机械工程》 * |
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