Symmetrically distributed line for testing flow characteristics of porous media of biomass

Abstract

The present application belongs to the technical field of biomass physical property testing, and discloses a symmetrically distributed pipeline for testing flow characteristics of biomass porous medium. The test platform comprises a gas pump, a horizontal pipeline, a vertical pipeline and a cylinder connected in sequence. The gas pump is connected with the cylinder through the horizontal pipeline and the vertical pipeline. The flow characteristics of the biomass porous medium to be tested are obtained by measuring the air pressure at the upper end and the lower end of the biomass porous medium to be tested, and by introducing flow gas into the biomass porous medium to be tested. The horizontal pipeline comprises a front half and a rear half. The front half comprises a plurality of parallel branch pipelines. The pipeline of the rear half comprises two symmetrically distributed branch pipelines. Each branch pipeline gradually increases from front to rear and then converges into one pipeline. The vertical pipeline gradually increases in diameter from bottom to top and is provided with a plurality of stages of rectifier orifice plates. The present application can realize wide flow range testing, reduce measurement parameter fluctuation and make air flow distribution more uniform.

Description

Technical Field

[0001] This invention belongs to the technical field of biomass physical property testing, and more specifically, relates to a symmetrically distributed pipeline for testing the flow characteristics of biomass porous media. Background Technology

[0002] my country boasts abundant and diverse biomass resources across its regions, with varied acquisition and utilization methods. The economic benefits of rationally utilizing biomass resources are substantial. Due to the carbon sequestration process in most biomass formation, it can also be considered a near-zero-carbon green fuel. However, the seasonality and regional variations in biomass supply mean that its utilization is unevenly distributed in time and space, inevitably requiring significant turnover and storage. Therefore, research on the ventilation and flow characteristics and fire mechanisms of porous biomass media is increasingly valued by scholars and engineers.

[0003] Traditional methods for testing the flow characteristics of porous media involve ventilating the biomass porous media with a fan and then obtaining the flow characteristic parameters by measuring the air pressure difference across the front and back of the biomass porous media (hereafter referred to as the traditional experimental method). However, this traditional experimental method has four significant drawbacks. First, biomass stacks with fire risks are often several meters or even tens of meters in size, making it difficult for the traditional experimental method to simulate such large-scale stacks. Second, the traditional experimental method, using a single air supply duct, easily leads to uneven airflow distribution within the stack, reducing the accuracy of the experimental measurements. Third, fluctuations in air pressure in the gas pipeline cause frequent fluctuations in the measured parameters, resulting in unstable and unreliable measurements. Fourth, the traditional experimental method does not consider the reduction in porosity caused by mutual compression within the biomass stack, nor does it consider the reduction in porosity caused by the expansion of biomass after absorbing moisture. Both of these phenomena significantly affect the test results of the flow characteristics of biomass porous media. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the prior art, the present invention provides a symmetrically distributed pipeline for testing the flow characteristics of biomass porous media, which can realize flexible testing over a wide flow range; reduce fluctuations in measurement parameters caused by airflow pulsation; and make the airflow distribution in the cross-section of the pipeline more uniform.

[0005] To achieve the above objectives, according to the present invention, a symmetrically distributed pipeline for testing the flow characteristics of porous biomass media is provided. This test platform includes a pump, a horizontal pipeline, a vertical pipeline, and a cylinder connected in sequence.

[0006] The air pump is connected to the cylinder through horizontal and vertical pipes to introduce gas into the cylinder. The biomass porous medium to be tested is placed in the cylinder. By introducing flowing gas into the biomass porous medium to be tested in the cylinder, the air pressure at the upper and lower ends of the biomass porous medium to be tested is measured to obtain the flow characteristics of the biomass porous medium to be tested.

[0007] The horizontal pipeline includes a front half and a rear half. The front half includes multiple parallel branch pipelines, and the rear half includes two symmetrically distributed branch pipelines. The diameter of each branch pipeline gradually increases from front to back. The vertical pipeline has a diameter that gradually increases from bottom to top.

[0008] More preferably, each branch of the front half of the horizontal pipe is equipped with a flow meter and a gas valve.

[0009] More preferably, the vertical pipeline is provided with multiple perforated plate bottom plates.

[0010] More preferably, the cylinder is provided with a support perforated plate and a top plate of the perforated plate. The support perforated plate is used to support the biomass porous medium to be tested, and the top plate of the perforated plate is placed on the biomass porous medium to be tested and is used to compact the biomass porous medium to be tested.

[0011] More preferably, the porosity of the bottom plate, the supporting plate, and the top plate of the perforated plate is greater than the overall porosity of the biomass porous medium under test.

[0012] More preferably, the supporting perforated plate and the top plate of the perforated plate include multiple rings of evenly distributed holes, wherein the holes on adjacent rings are staggered.

[0013] More preferably, the top plate of the perforated plate is provided with a weight rack and weights. The weights are used to apply pressure to the biomass porous medium to be tested, thereby simulating the phenomenon of the expansion of biomass after absorbing water and the mutual compression inside the biomass porous medium, as well as the decrease in porosity of the biomass porous medium under different bulk densities.

[0014] More preferably, a pressure stabilizing pipe is provided at the connection point of multiple parallel branches in the first half of the horizontal pipeline to regulate the pressure of the pipeline.

[0015] More preferably, one or more sealing gaskets are provided on the outside of the cylinder between the support perforated plate and the top plate of the perforated plate.

[0016] More preferably, a pressure gauge is provided below the support plate and above the top plate of the plate to detect the pressure of the porous biomass medium to be tested.

[0017] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art:

[0018] 1. In this invention, the rear half of the horizontal pipe adopts two horizontally symmetrically distributed pipelines, and the airflow collision design in front of the vertical pipe is adopted to alleviate the airflow deflection effect of high-speed airflow at the bend; the front half of the horizontal pipe adopts a multi-stage gas uniform distribution orifice plate and expansion section to uniformly distribute and rectify the airflow in the pipeline, which can make the high-speed airflow more uniformly distributed in the cross-section of the pipeline.

[0019] 2. The horizontal pipe of the present invention has multiple parallel branches in the front part, which can simultaneously realize flow regulation over a wide flow range with a difference of more than several orders of magnitude, thus expanding the flexibility of experimental working condition settings.

[0020] 3. The vertical pipe of the present invention adopts a pipe diameter that is smaller at the bottom and larger at the top. Structurally, this makes the pipe diameter change smoother. In terms of aerodynamic characteristics, it can make the flow inside the pipe more uniform within the pipe cross-section, avoiding the situation where the flow is too fast in the middle and slower around the edges. At the same time, multiple orifice plates are provided in the vertical pipe. Their function is that the airflow can be re-rectified once after passing through an orifice plate, making the airflow more stable and the flow velocity more uniform when passing through the diameter change section of the vertical pipe.

[0021] 4. In this invention, a weight is placed above the biomass porous medium to be tested. By adjusting the weight of the valve, the compression state caused by the stacking of biomass porous media of different heights and weights can be simulated. At the same time, it can also simulate the phenomenon of reduced porosity of porous media caused by the expansion of biomass after absorbing water and the mutual compression inside the biomass porous medium. This makes the flow characteristics of biomass porous media measured in the experiment more consistent with the actual stacking conditions in biomass stacking. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the biomass porous media flow characteristic comprehensive testing platform constructed according to a preferred embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the structure of the horizontal and vertical pipes constructed according to a preferred embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of a support perforated plate structure constructed according to a preferred embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram of the structure of the perforated plate top plate constructed according to a preferred embodiment of the present invention;

[0026] Figure 5This is a schematic diagram of a vertical pipe constructed according to a preferred embodiment of the present invention, wherein (a) is a schematic diagram of the front structure of the vertical pipe, and (b) is a schematic diagram of the top structure of the vertical pipe.

[0027] Figure 6 This is an experimental procedure for testing the flow characteristics of biomass porous media constructed according to a preferred embodiment of the present invention.

[0028] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0029] 1-Weight, 2-Weight holder, 31-Top plate of orifice plate, 32-Supporting orifice plate, 33-Bottom plate of orifice plate, 4-Barometer, 5-Cylinder, 6-Porous biomass medium to be tested, 7-Sealing gasket, 8-Base, 9-Air pump, 10-Flow meter, 11-Air valve, 12-Pressure stabilizing tank, 13-Horizontal pipe, 14-Vertical pipe. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0031] A symmetrically distributed pipeline for testing the flow characteristics of biomass porous media first considers the actual stacking conditions of the biomass porous media material. On the one hand, according to actual needs, the biomass porous media material undergoes different degrees of atomization and humidification pretreatment, which can simulate the phenomenon of reduced porosity caused by the expansion of porous media after biomass absorbs water. On the other hand, in the experimental platform of this invention, weights are used to apply vertical gravity to the biomass porous media, which can simulate the phenomenon of reduced porosity caused by mutual compression within large biomass stacks. Then, a new layout is proposed for the pneumatic channel of the biomass porous media flow characteristic testing platform. A multi-stage gas uniformly distributed orifice plate bottom plate and expansion section are used to uniformly distribute and secondary rectify the airflow in the pipeline. A horizontally symmetrically distributed two-way pipeline airflow collision design is used to alleviate the deflection effect of high-speed airflow at bends. Three parallel pipelines are set at the air pump outlet to simultaneously achieve flow regulation over a wide flow range with a difference of more than three orders of magnitude, and a pressure stabilizing tank is set on the pipeline to stabilize the high-frequency fluctuating air pressure.

[0032] like Figure 1As shown, a symmetrically distributed pipeline for testing the flow characteristics of porous biomass media includes, in sequence from the beginning to the end of a positive pressure system: an air pump 9, a flow meter 10 with three flow meters capable of measuring and adjusting different flow ranges and an air valve 11, a pressure stabilizing tank 12, two horizontally distributed pipes 13 symmetrically distributed along an axis, a vertical pipe 14 with three sets of gas uniformly distributed orifice plates, a pressure gauge 4, a supporting top plate 32, a sealing ring, a cylinder 5, an orifice plate top plate 31, a pressure gauge 4, and a weight rack and weights.

[0033] The feature of the three-way flow meter 10 and air valve capable of measuring and adjusting different flow ranges is as follows: three sets of flow measurement and adjustment ranges are selected, and one more flow meter 10 and corresponding air valve 11 are added to each set. The set of flow meter 10 and air valve 11 with the largest gas flow is set in the middle of the three pipelines.

[0034] like Figure 2 As shown, two horizontal pipes 13 are distributed symmetrically along the axis. Both pipes need to be equipped with a variable diameter section that increases in size along the direction of airflow. The two pipes need to be installed in a mutually symmetrical structure along the central axis of the vertical pipe 14.

[0035] like Figure 2 and 5 As shown, the vertical pipe 14 adopts a variable diameter section with a smaller bottom and a larger top, and the upper end is connected to the experimental platform base 8 by a flange seal. Three orifice plate bottom plates 33 are installed in the vertical pipe 14.

[0036] In this embodiment, the pipe diameters of each pipe are as follows: DN60 for the fan outlet, three flow meters and valves, the three pipes are combined into the pressure stabilizing tank, and then split into two to enter the horizontal branch pipes, the pipe diameter changes from DN60 to DN110 (first diameter change transition); the latter half of the horizontal pipes each pass through DN110 bends and then merge into one after airflow collision, this is a T-junction, the two horizontal collisions enter, and after merging, the flow flows upward;

[0037] After the airflow merges, it enters the vertical pipe, where the diameter changes from DN110 to DN300, and flows through the perforated plate and the biomass porous medium.

[0038] The pipe at the fan outlet is relatively thin, and the pipe at both ends is set with a diameter change section between the pipe and the relatively thick pipe in the cylinder. This can effectively reduce the pressure loss when the airflow suddenly enters the thick pipe from the thin pipe and reduce the airflow unevenness caused by the discontinuity between the thin and thick pipes.

[0039] The reason for branching the horizontal duct in the latter half is to avoid the deflection problem caused by centrifugal force when the high-speed airflow bends upward from the horizontal to the vertical duct in a single duct. The symmetrical branching duct provided by this invention divides the horizontal airflow into two paths, which then merge through two bends before entering the vertical duct. During the merging of the two symmetrical airflow paths, the centrifugal force of the bends can be offset by collision, making the airflow more evenly distributed after entering the vertical duct from the horizontal duct.

[0040] In addition, the above structure can also offset some of the wind pressure pulsations caused by the blower by colliding during the convergence of two symmetrical airflows.

[0041] like Figure 3 and 4 As shown, the characteristics of the orifice plate top plate 31, the supporting top plate 32, and the three orifice plate bottom plates 33 are as follows: the opening ratio of the above orifice plates is greater than the overall porosity of the biomass porous medium 6 to be tested. Among them, the orifice plate top plate 31 and the supporting top plate 32 need to withstand the weight load applied in the vertical direction. By default, the orifice plate that needs to be subjected to the vertical load is preferably made of stainless steel with a thickness of 6mm, provided that the strength is sufficient. The orifice plate opening ratio range is selected from 0.3 to 0.8. If the strength of the orifice plate does not meet the requirements when subjected to the vertical load, stainless steel orifice plates with a thickness of 8mm and 10mm can be appropriately selected, but the thickness should not exceed 10mm.

[0042] A method for comprehensive testing of the flow characteristics of biomass porous media includes the following steps:

[0043] like Figure 6 As shown, the biomass porous media material is pretreated by first adjusting the initial moisture content of the biomass porous media material through an atomizing humidifier and a vacuum drying oven. Then, the biomass porous media material is stacked in the cylinder of the biomass porous media flow characteristic test platform. A perforated plate top plate 31 and a weight rack are placed above the biomass porous media material. Then, according to the experimental needs, a certain mass of weights are placed on the weight rack. This pretreatment process is used to realistically simulate the actual porosity of biomass porous media under different moisture contents and different bulk densities.

[0044] After pretreatment, select one gas flow channel in the three parallel horizontal pipes 13 according to the required experimental flow range. Sequentially open the gas valve, flow meter and air pump 9 on this channel. Adjust the closure degree of the gas valve on this channel to make the flow meter reach the experimental target flow. After the flow meter flow stabilizes, read the gas pressure measured by the gas pressure tester 4 on both sides of the biomass porous medium. Record the flow characteristic data under this working condition, and change the working condition to carry out the next set of experiments until the end.

[0045] The following example illustrates the application of the biomass corn cob porous media flow characteristic testing method on the integrated platform for biomass porous media flow characteristics.

[0046] The biomass corn cob porous media flow characteristic comprehensive testing platform of this invention is connected sequentially from the beginning to the end of the positive pressure system as follows: air pump 9, pipeline containing three flow meters 10 and air valves 11 capable of measuring and adjusting different flow ranges, pressure stabilizing tank 12, two horizontally distributed axially symmetrical pipes 13, vertical pipe 14 containing three sets of gas uniform distribution orifice plates, pressure gauge 4, gas uniform distribution support orifice plate 32, sealing gasket 7, cylinder 5, orifice plate top plate 31, pressure gauge 4, weight rack 2, and weight 1. Except for the flexible rubber connection between the horizontal pipe 13 and the vertical pipe 14 for vibration isolation, the other pipelines and fittings are connected by flange seals. All orifice plates are made of 6mm thick stainless steel plate with an opening ratio of 0.6.

[0047] Before the experiment, the corn cob material needs to be pretreated. First, the initial moisture content of the corn cob material is adjusted to 50% by using an atomizing humidifier and a vacuum drying oven. Then, the corn cobs are stacked in cylinders 5-1 and 5-2 of the biomass porous media flow characteristic test platform. The perforated plate top plate 31 and the weight rack 2 are placed above the corn cobs. Then, according to the experimental requirements, a 100 kg weight 1 is placed on the weight rack 2 to simulate the actual porosity of the biomass porous media under 50% moisture content and 100 kg action packing density. After pretreatment, select a flow rate of 20-200 cubic meters per hour in the middle gas flow channel of the three parallel horizontal pipes 13. Open the gas valve 11, flow meter 10 and air pump 9 in the middle channel in sequence. Adjust the closing degree of the gas valve 11 in the gas channel so that the flow meter 10 reaches the experimental target flow rate of 50 cubic meters per hour. After the flow rate of the flow meter 10 stabilizes, read the gas pressure measured by the gas pressure tester 4 on both sides of the biomass porous medium, record the flow characteristic data under this working condition, and change the working condition to carry out the next set of experiments until the experiment ends.

[0048] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A symmetrically distributed pipeline for testing the flow characteristics of porous biomass media, characterized in that, The test platform includes an air pump (9), a horizontal pipe (13), a vertical pipe (14), and a cylinder (5) connected in sequence. The air pump (9) is connected to the cylinder (5) through a horizontal pipe (13) and a vertical pipe (14) for introducing gas into the cylinder (5). The biomass porous medium (6) to be tested is placed in the cylinder (5). By introducing flowing gas into the biomass porous medium to be tested in the cylinder, the air pressure at the upper and lower ends of the biomass porous medium to be tested is measured, thereby obtaining the flow characteristics of the biomass porous medium to be tested. The horizontal pipe (13) includes a front half and a rear half. The front half includes multiple parallel branch pipes, and the rear half includes two symmetrically distributed branch pipes. The diameter of each branch pipe gradually increases from front to back. The two branch pipes are merged into one pipe and then connected to the vertical pipe. The diameter of the vertical pipe (14) gradually increases from bottom to top. The cylinder (5) is provided with a support perforated plate (32) and a perforated plate top plate (31). The support perforated plate (32) is used to support the biomass porous medium to be tested, and the perforated plate top plate (31) is placed on the biomass porous medium to be tested and is used to compact the biomass porous medium to be tested. The top plate (31) of the perforated plate is provided with a weight rack (2) and a weight (1). The weight (1) is used to apply pressure to the biomass porous medium to be tested, thereby simulating the phenomenon of the expansion of biomass after absorbing water and the mutual compression inside the biomass porous medium, as well as the decrease in porosity of the biomass porous medium under different bulk densities.

2. The symmetrically distributed pipeline for testing the flow characteristics of porous biomass media as described in claim 1, characterized in that, Each branch of the front half of the horizontal pipe (13) is equipped with a flow meter (10) and a gas valve (11).

3. The symmetrically distributed pipeline for testing the flow characteristics of porous biomass media as described in claim 2, characterized in that, The vertical pipe (14) is provided with multiple perforated bottom plates (33).

4. The symmetrically distributed pipeline for testing the flow characteristics of porous biomass media as described in claim 3, characterized in that, The porosity of the bottom plate (33), the supporting plate (32), and the top plate (31) of the perforated plate is greater than the overall porosity of the biomass porous medium under test.

5. A symmetrically distributed pipeline for testing the flow characteristics of porous biomass media as described in claim 1, characterized in that, The support plate (32) and the top plate (31) of the plate include multiple rings of evenly distributed holes, wherein the holes on adjacent rings are staggered.

6. A symmetrically distributed pipeline for testing the flow characteristics of porous biomass media as described in claim 2, characterized in that, A pressure stabilizing pipe is provided at the connection of multiple parallel branches in the front half of the horizontal pipe (13) to regulate the pressure of the pipe.

7. A symmetrically distributed pipeline for testing the flow characteristics of porous biomass media as described in claim 1, characterized in that, A sealing gasket is provided between the vertical pipe (14) and the support orifice plate (32), and between the support orifice plate (32) and the cylinder (5), for sealing purposes.

8. A symmetrically distributed pipeline for testing the flow characteristics of porous biomass media as described in claim 1, characterized in that, A pressure gauge is provided below the support plate (32) and above the top plate of the plate to detect the pressure of the porous biomass medium to be tested.

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