Abstract
The positive pressure beam tube system addresses issues related to gas composition distortion, concentration variations, and long transmission delays observed in traditional negative pressure systems. It has increasingly become the primary system for early monitoring and warning of coal spontaneous combustion in goaf areas. Nevertheless, there remains a deficiency in comprehensive research concerning critical aspects like gas transmission characteristics and transmission lag time in the positive pressure beam tube system. This study aims to construct an experimental platform for the positive pressure beam tube monitoring system and systematically investigate how the choice of pressurization device, pipe length, pipe diameter, and driving pressure in the transmission pipeline affect gas transmission characteristics. The findings indicate that the most effective pressurization occurs under conditions of two-stage high positive pressure transport, with a driving gas pressure of 0.65 MPa. The optimal diameter for positive pressure gas transmission is 7 mm. Long-distance negative pressure pipelines result in decreased transmission efficiency, necessitating increased output pressure with the lengthening of positive pressure pipelines to maintain efficiency.
Supplementary Information
The online version contains supplementary material available at 10.1038/s41598-024-81963-1.
Keywords: Monitoring and early warning, Positive pressure beam tubes, Staged pressurization, Transmission characteristics
Subject terms: Engineering, Environmental impact
Introduction
Coal holds a pivotal position in China’s energy framework1, with annual production steadily rising. However, more than 90% of China’s coal seams are susceptible to spontaneous combustion or readily ignite, resulting in over 4000 mining incidents annually and necessitating the closure and preservation of significant coal reserves2. This process leads to the release of greenhouse gases like CO2 and CH4, along with toxic pollutants such as CO and SO23–8. Furthermore, it can trigger secondary disasters such as dust explosions and methane eruptions, leading to significant human casualties and economic losses9–15. Therefore, timely and effective early monitoring and warning of spontaneous combustion in mined-out areas are essential for prevention and control.
The beam tube monitoring system16 collects gas from the goaf’s monitoring points via embedded beam tube pipelines, transporting it to the analysis and detection center. The gas composition including CH4, O2, CO, C2H4, and others17in the monitored gas is analyzed using chromatography to assess the goaf’s ignition status18. The conventional beam tube monitoring system draws gas from monitoring points to the surface for negative-pressure analysis and detection19–21. However, this method is prone to gas sample distortion, low transmission efficiency, and long analysis cycles22,23. Lu Wei et al.24,25 suggested employing positive pressure for gas sampling transport, pioneering a positive pressure beam tube monitoring system, and implementing a pipeline transmission system for gas transport and control. Li Shangguo et al.26 confirmed that positive pressure gas transmission preserves sampled gas concentration, ensuring accurate data reflection of coal’s spontaneous combustion state. Bai Guangxing et al.27conducted comparative analysis of positive and negative pressure beam tubes using experiments and empirical function fitting. The results indicate that positive pressure beam tubes achieve superior sampling time and flow rates under equivalent sampling lengths. The positive pressure beam tube monitoring system exhibits superior sampling accuracy28,29, extended sampling distance, and reduced sampling duration30.
Currently, the positive pressure beam tube system has increasingly replaced the traditional beam tube system as a prevalent monitoring system in mines. Many scholars have progressively conducted research on optimizing the performance of the positive pressure beam tube system. However, there have been few studies on how tube length, diameter, and driving pressure influence the gas transmission characteristics of the positive pressure beam tube system. This study constructs an experimental platform for the positive pressure beam tube monitoring system to investigate the stable gas transmission flow and transmission time under varying compression ratios, gas transmission pipe diameters, lengths of acquisition and transmission pipes, and driving air pressures. This enhances the reliability and accuracy of the positive pressure beam tube monitoring system in mines, thereby offering insights for predicting spontaneous combustion in goaf under comparable conditions.
Positive pressure beam tube monitoring system
Mine positive pressure beam tube monitoring system composition
The system is composed of five primary components: a gas positive pressure conveying module, a gas analysis module, a control module, a data acquisition module, and a workstation, depicted in Fig. 1. The positive pressure beam tube monitoring system is designed to extract gas from monitoring points in the goaf of the working face through negative pressure gas collection methods. The extracted gas is subsequently pressurized and conveyed to a monitoring station either on the surface or underground using a positive pressure pump. Subsequently, comprehensive analysis of gas composition and concentration is undertaken to enable monitoring and prediction of mine fires.
Fig. 1.
Structure composition of positive pressure beam tube system. 1-negative pressure gas pipeline; 2-filter; 3 - gas path switching cabinet; 4-positive pressure booster pump; 5-positive pressure gas pipeline; 6-gas exhaust pipeline; 7-gas path switching control cabinet; 8 - Inlet gas pipeline.
Grading pressurized beam tube gas conveying platform
An experimental platform was constructed to simulate the operational workflow of the positive pressure beam tube monitoring system. The platform primarily comprises a driving air compressor, high-pressure gas storage cylinder, pressure gauge, pneumatic high positive pressure pressurization equipment, electronic flowmeter, negative pressure collection pipeline, positive pressure conveying pipeline, dust filter, water filter, and gas sensor, depicted in Fig. 2.
Fig. 2.
Positive pressure beam tube long distance gas transmission test system device.
The driving air compressor serves as the power source for the pneumatic high positive pressure pressurization equipment, driving its operation. The pneumatic high positive pressure booster equipment consists primarily of two pneumatic booster pumps. The pump body operates by using low-pressure gas on the large-area piston end to generate high-pressure fluid on the small-area piston end. Initially, negative pressure gas undergoes first-stage compression to become low positive pressure gas, which is further pressurized in a second stage to achieve stable pressurized output from the negative pressure collection.
The experimental high positive pressure gas transmission device with two-stage compression technology divides the entire gas pressurization process into two stages, with each stage overcoming a small fraction of resistance, in accordance with the ideal gas law:
 |
1 |
In the equation, 
denotes pressure, Pa; 
signifies gas volume, m³; 
indicates temperature, K; 
represents the amount of substance, mol; and 
is identified as the ideal gas constant, commonly referred to as the universal gas constant, J/(mol·K).
From Eq. (1), it can be deduced that when the quantity of compressed gas remains constant, the temperature 
within the cylinder will rise during the pressurization process, exhibiting a more pronounced temperature variation at elevated compression ratios. Therefore, the high compression ratio of a single cylinder can lead to excessive temperatures during gas pressurization, potentially causing equipment damage during prolonged high-temperature operation. Hence, the compressor supplies high-pressure gas for staged compression, illustrated in Fig. 3.
Fig. 3.
Two-stage compression schematic.
In the context of staged compression, the first-stage compression cylinder operates with a compression ratio of 1:3, while the second-stage compression cylinder operates at a ratio of 1:8. The first-stage compression employs a low compression ratio, followed by isobaric cooling facilitated by a cooler. This process reduces temperature, increases density, and facilitates further compression. Following the second-stage compression, low-pressure gas is elevated to high-pressure gas. Hierarchical compression conserves power consumption and achieves near-isothermal compression conditions.
Assembly and operation of the booster pump necessitate a clearance volume within the cylinder. The presence of clearance volume decreases actual exhaust volume and reduces the utilization efficiency of the cylinder’s working volume during compression, thereby leading to a reduction in volumetric efficiency. The relationship between actual exhaust volume and volumetric efficiency31 is expressed in Eq. (2):
 |
2 |
In the formula, 
represents volumetric efficiency; 
denotes actual exhaust volume, m3; 
signifies cylinder volume, m3. Volumetric efficiency is defined as the ratio of the actual volume of the mixture inhaled by the cylinder to the cylinder volume during the intake stroke. The increase in clearance volume not only decreases the volumetric efficiency 
of the cylinder, but also necessitates the expansion of residual high-pressure gas to suction pressure before the cylinder can intake fresh gas, thereby further reducing the volumetric efficiency 
of the cylinder32. Higher pressure ratios lead to more violent expansion of residual gas in clearance volume, thereby reducing the volumetric efficiency33. Hence, employing graded compression to reduce cylinder clearance volume enhances cylinder volumetric efficiency34, thereby enhancing the efficiency of the positive pressure beam tube system in pressurizing collected gas. The experimental platform for the beam tube was constructed using assembled graded pressurization equipment to experimentally investigate the impact of driving pressure, negative pressure gas collection section diameter, and positive pressure conveying pipe diameter and length on gas transmission.
Gas transmission characteristics under various operational conditions within the negative pressure section
During gas transmission in pipelines, the length of the negative pressure gas collection section significantly affects gas collection efficiency, while the pipeline characteristics are closely tied to pressure losses during transmission. According to the principles of fluid mechanics, the formula for calculating pressure loss during gas transmission is35
 |
3 |
The formula comprises the following variables: 
represents the pressure loss, Pa; 
stands for the experimental proportional coefficient; 
denotes the pipeline length, m; 
indicates the mass flow rate, kg/sec; 
signifies the gas density, kg/m³; and d represents the inner diameter of the pipeline, m.
The calculation formula of pipeline gas transmission time is35
 |
4 |
where 
is the gas volume, m3; 
is the pipeline characteristic parameter that is related to the properties of the fluid, flow conditions, or system design; 
is the transmission time, s.
Equations (3) and (4) indicate that during pipeline gas transmission, factors such as pipeline length, pipe diameter, and friction coefficient significantly impact gas pressure loss, subsequently influencing gas transmission efficiency. Experimental setups involved varying compression conditions and lengths of the negative pressure gas recovery section. Sensors and electronic flowmeters were installed at the positive pressure pipeline’s end to precisely record the duration and stable flow rates required for extracting and transferring marker gas from the negative to positive pressure ends, facilitating the positive pressure gas transportation experiment.
The impact of negative pressure section length on gas collection efficiency
Variations in the length of the negative pressure gas collection pipeline affect the gas transmission characteristics of the positive pressure beam tube. Various lengths of the negative pressure gas collection pipeline (ranging from 0 to 1 km) were connected, and a negative pressure vacuum meter was installed at the pipeline’s end to monitor gas collection pressures. During the experiment, the 4 km length of the positive pressure pipeline and the driving pressure of 0.2 MPa were kept constant. Stable pressure readings were recorded at the collection pipeline’s end using the negative pressure meter for different pipeline lengths, as detailed in Table 1.
Table 1.
The variation of negative pressure with pipeline length.
| Tube length/m | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900 | 1000 |
|---|---|---|---|---|---|---|---|---|---|---|
| Negative pressure/-kpa | 74.2 | 58.3 | 47.4 | 36.6 | 30.7 | 24.3 | 15.6 | 12.2 | 9.32 | 7.64 |
The relationship between negative pressure and pipeline length is derived from the data in Table 1. Figure 4 illustrates that the negative pressure at the end gas collection point decreases from 74.2 kPa when the negative pressure section length is 100 m to 7.64 kPa when it increases to 1000 m. The farther the gas collection point at the end of the negative pressure pipeline is from the inlet end of the pneumatic pressurization equipment, the lower the negative pressure, approaching atmospheric pressure.
Fig. 4.
The relationship between the negative pressure and the length of the pipeline.
From Fig. 4, the mathematical empirical model can be obtained by Non-linear curve fitting function:
 |
5 |
In the formula, 
represents the pressure variable, x represents the length variable of the negative pressure pipeline, and 
and 
denote the two coefficients of the empirical formula. The high fitting degree R2 of 0.99701 characterizes the relationship between negative pressure and the length attenuation of the pipeline. This experience function can be effectively used to analyze the relationship between pressure changes along the pipeline length in the monitoring system of positive pressure beam tube for coal mine fire detection during the gas collection process. Based on theoretical Formula (3), (5) and analysis of experimental results, it is concluded that as the length of the negative pressure gas collection pipeline increases, the pump end requires higher negative pressure to collect suction gas for compression output. This ensures that the lengthening of the negative pressure collection section minimizes the impact on the overall system’s transmission efficiency. During long-distance gas collection, significant pressure loss 
occurs, resulting in notably low collection efficiency. Hence, in practical applications, excessive length of the negative pressure gas collection section compromises system efficiency.
Gas transmission characteristics under different lengths of negative pressure section
The experiment utilizes pneumatic pressurization units configured for one-stage and two-stage compression. A consistent driving gas pressure of 0.2 MPa is applied through a 4 km transmission pipeline (3
2 mm). Various lengths of the negative pressure gas recovery section are tested to investigate their impact on output flow, output pressure, and detection time under varying compression ratios. Under the conditions of two-stage compression and single-stage compression, the output pressures are 1.93 ~ 2.62Mpa and 0.81 ~ 1.23Mpa, respectively. As shown in Fig. 5, it is the change curve of the terminal stable flow rate and the gas sample detection time with the length of the negative pressure gas collection pipeline under the conditions of two-stage compression and single-stage compression, respectively.
Fig. 5.
The relationship between the stable flow rate and the detection time of the end under different compressions with the pipeline. (a) flow comparison, (b) time comparison.
Figure 5 (a) and (b) illustrate that increasing the length of the negative pressure section impacts both the terminal gas detection time and the stable flow rate. At the single-stage compression ratio, due to its low value, the output pressure reaches only 0.81 to 1.23 MPa under a driving pressure of 0.2 MPa. For a negative pressure section length of 100 m, the flow rate is 1.23 L/min, with a detection time of 2568 s. However, for a length of 1000 m in the negative pressure section, the flow rate decreases to 0.84 L/min, resulting in a significantly lower stable flow rate at the end, along with an extended detection time of up to 8014 s. Under the two-stage compression ratio, as the length of the negative pressure gas collection section increases, the gas detection time at the end of the positive pressure transmission pipeline increases, while the end flow rate decreases. For a negative pressure gas recovery section pipeline length of approximately 100 m, the end flow is substantial at 4.89 L/min, with a short detection time of 1074 s. Conversely, with an extended negative pressure section pipeline length, such as 1000 m, the end flow rate drops to 3.55 L/min, resulting in a detection time of 3452 s.
According to the Darcy-Weisbach equation, which describes the relationship between head loss due to friction in a fixed-length pipeline and the average flow velocity in the pipeline36:
 |
6 |
is the head loss caused by friction (m); 
is the length of the pipeline, m; 
is the hydraulic diameter of the pipeline, m; 
is the average velocity of the fluid, m/s; 
is the gravitational acceleration, m/s²; and 
is a dimensionless factor known as the Darcy friction factor.
By applying Formulas (3), (4) and (6) analyzing the experimental results, it is concluded that an increase in the length of the negative pressure section leads to higher negative pressure losses. Gas is pumped from the end of the negative pressure gas collection pipeline to the compression unit, requiring increased effort from the pump body and resulting in longer consumption times. Hence, an increase in the pipeline length of the negative pressure section reduces the gas sampling efficiency and complicates the gas collection process.
Gas transmission characteristics of positive pressure pipeline under different working conditions
The sizes of the positive pressure gas transmission pipeline and the pressure of the equipment driving source significantly influence resistance loss and gas transmission characteristics during gas transmission. The influence of varying experimental variables— (1) different inner diameters of positive pressure transmission pipelines, (2) varying lengths of positive pressure transmission pipelines, and (3) different driving pressures—on gas positive pressure transmission is investigated.
Formulas (4) and (6) indicate that resistance loss in gas transmission is inversely proportional to the diameter of the pipeline and directly proportional to its length. The transmission time 
inversely correlates with the square root of the output pressure difference 
. The output pressure of the pneumatic pressurization equipment primarily depends on the pressure of the driving air source. Thus, experiments are designed to investigate how different positive pressure transmission pipelines and driving pressures affect gas transmission.
Gas transmission characteristics of a positive pressure pipeline under varying pipe diameters
The experiment involved three positive pressure pipelines with diameters of 3
2 mm, 6
4 mm, and 10
7 mm. Each diameter was tested under the same driving pressure of 0.2 MPa. The length of the positive pressure pipelines ranged from 0 to 4 km, with a 200 m length for the negative pressure gas collection section. Positive pressure conveying experiments were conducted using two-stage compression for each pipe diameter. Under constant driving pressure, variations in gas sample detection time, stable flow rate, and output pressure correlate with the length of positive pressure transmission pipelines, as depicted in Figs. 6, 7 and 8.
Fig. 6.
Curves of stable flow rate with pipeline length under different pipe diameters.
Fig. 7.
The variation curve of transmission time with pipeline length under different pipe diameters.
Fig. 8.
The variation curve of output pressure with pipeline length under different pipe diameters.
Figure 6 illustrates that the stable flow rate decreases with increasing length of the positive pressure pipeline across all three pipe diameters. Notably, the pipeline with a diameter of 10
7 mm exhibits the highest stable flow rate, ranging from 34.81 to 16.54 L/min, whereas the 3
2 mm pipeline shows the lowest stable flow rate, ranging from 7.83 to 4.51 L/min. To investigate the characteristics of gas flow variation with changes in pipe diameter during the gas transmission process, according to the formula for gas flow in horizontal pipelines37:
 |
7 |
where 
is the flow rate of gas, L/min; standard conditions are defined as 
=1.1325 × 105 Pa and 
=298.15 K; 
is the pressure at the beginning of the pipeline, Pa; 
is the pressure at the end of the pipeline, Pa; 
is the compression coefficient, dimensionless; 
is the gas constant, m2/(s2⋅K); 
is the gas temperature, K; 
is the inner diameter of the pipeline, m; 
is the length of the pipeline, m; additionally, 
is the friction factor, dimensionless.
It is evident that, under constant conditions, an increase in pipe diameter significantly enhances the gas flow rate transmitted per unit time. Specifically, when the diameter is doubled, the flow rate can increase by approximately 5.6 times. Therefore, in practical applications, it is advisable to use larger diameter pipes for gas transportation within permissible limits.
Installation of sensors at the terminus of the positive pressure conveying pipeline facilitates recording the time required for marker gas to travel from the negative pressure end to the pipeline terminus. Figure 7demonstrates that as the length of the positive pressure conveying section increases, so does the transmission detection time of the marker gas. At a pipeline length of 500 m, transmission times vary across pipe diameters: 169 s, 138 s, and 114 s. For a length of 4 km, these times increase to 1196 s,1106 s, and 1037 s, respectively. The increase in pipe diameter impacts the output pressure of the booster equipment, prompting derivation of a formula to calculate gas transmission time through the pipeline37.
 |
8 |
Substituting Eq. (7) into Eq. (8) and simplifying yields the formula for the gas transmission lag time in the pipeline:
 |
9 |
The time required for gas output depends on the pressure difference, pipe diameter, and pipe length. When the lengths of the three pipes are the same and the pressure differences are identical, doubling the pipe diameter reduces the conveying time to approximately 70% of the original. Increasing the pipe diameter reduces the challenges associated with gas transport. For instance, when the inner diameter of the pipeline increased from 2 mm to 7 mm during the experiment, the pressure decreased from [1.34,2.48] MPa to [0.63,1.31] MPa, consequently reducing the output pressure of the booster equipment.
Figure 8 illustrates that as the pipeline length increases, the output pressure also increases. For a 500 m pipeline, the output pressure ranges from 1.34 MPa to 0.63 MPa in descending order. For a 4 km pipeline, the output pressure ranges from 2.98 MPa to 1.31 MPa. Consequently, in practical applications, increasing pipeline length necessitates higher output pressures to maintain gas transmission efficiency.
Gas transmission characteristics under different driving gas pressures
Experimental findings suggest that the pressurization of pneumatic equipment assemblies depends on pipeline conditions, pre-gas inlet pressure, and the pressure from the driving gas source. Accordingly, the experiments connected the negative pressure gas collection pipeline to examine the impact of different driving pressures (0.2 MPa, 0.4 MPa, and 0.6 MPa) on the transmission of the positive pressure beam tube monitoring system.
At three distinct driving gas pressures, marker gas is drawn from the terminus of the negative pressure gas collection segment, while a sensor at the terminus of the positive pressure transmission pipeline monitors its presence. Recorded are the gas transmission time, stable flow rate, and output pressure under varying driving gas pressures. Figures 9 and 10, and 11 illustrate the correlation between flow rate, detection time at the terminal, output pressure from the positive pressure booster device, and the length of the positive pressure pipeline.
Fig. 9.
The variation curve of stable flow rate with pipeline length under different driving pressures.
Fig. 10.
The variation curve of transmission time with pipeline length under different driving pressures.
Fig. 11.
The variation curve of output pressure with pipeline length under different driving pressures.
Figure 9 illustrates that higher driving gas pressures result in increased stable gas transmission flow rates. At a driving gas pressure of 0.2 MPa, the stable gas transmission flow rate ranges from 4.51 to 7.83 L/min along the length of the positive pressure conveying section. As the driving gas pressure increases to 0.6 MPa, this range expands to 7.32 to 14.75 L/min. Consequently, selecting a higher driving gas pressure results in a higher gas flow rate.
Figure 10 depicts the transmission time curve as a function of positive pressure tube length under varying driving pressures. The figure illustrates that as the driving pressure increases, the gas transmission time decreases. As the driving gas pressure increases from 0.2 MPa to 0.6 MPa, the gas transmission time decreases from 209 to 1531 s to 139 to 943 s, respectively, as the length of the positive pressure conveying section varies. Consequently, increasing the driving gas pressure enhances gas transmission efficiency, although increasing the length of the positive pressure transmission section results in longer transmission times.
Figure 11 illustrates that increasing the driving gas pressure results in higher output pressure. At a driving gas pressure of 0.2 MPa, the output pressure of the pneumatic pressurization device ranges from 1.34 MPa to 2.48 MPa along the pipeline. At a driving gas pressure of 0.6 MPa, the output pressure ranges from 3.56 MPa to 4.72 MPa, varying with the length of the positive pressure pipeline. This increase in driving gas pressure enhances the pressurization efficiency of the booster pump, allowing for two-stage compression of the inhaled marker gas to achieve higher pressure positive gas output.
The driving pressure affects the output pressure of pneumatic boosting devices. To investigate the optimal driving pressure of such devices, experiments were conducted on gas transmission through bundled tubes at different driving pressures. The relationship between driving pressure and output pressure obtained is shown in Fig. 12.
Fig. 12.
The relationship between driving pressure and output pressure. (a) output pressure, (b) rate of change.
Analysis of Fig. 12(a) and (b) reveals that with increasing driving air pressure of the pump, the output pressure of the positively pressurized gas increases accordingly. Specifically, at a pump driving air pressure of 0.65 MPa, the output pressure reaches 4.77 MPa. Beyond this point, the rate of change in output pressure diminishes significantly with variations in driving air pressure. The increase in gas output pressure slows down, stabilizing the output pressure. Therefore, considering both energy consumption and overall driving efficiency, 0.65 MPa is chosen as the optimal driving air pressure for the pump.
Application of findings to various gas transmission systems
In this study, we conducted a comprehensive analysis of gas transmission experiments and output pressure measurements under varying driving pressures. Our findings indicate that fluctuations in driving pressure significantly influence both gas transmission efficiency and output pressure. Regarding the positive pressure beam tube system utilized for mine fire monitoring, the results suggest that increasing the driving pressure within the design of extended pipelines can significantly enhance the stability of gas flow and reduce transmission durations. Consequently, it is imperative to integrate monitoring and regulation mechanisms into the design of fluid systems, such as electronic flow meters and pressure regulators, to ensure flow stability and facilitate timely gas transmission. Furthermore, we advocate for the integration of pressure sensors within the gas transmission system to enable real-time monitoring of output pressure.
While this study primarily addresses positive pressure beam tube monitoring systems in mine fire scenarios, its findings and methodologies are also applicable to other fluid transmission systems. For example, in practical applications within coal mining engineering—specifically nitrogen injection, carbon dioxide injection, and fire suppression systems utilizing chemical agents—driving and transmission pressures should be adjusted based on pipeline length and diameter during gas pressurization. However, parameter adjustments should be tailored to the specific properties of various media involved.
Conclusion
In comparison to the traditional negative pressure beam tube monitoring system, the positive pressure variant exhibits significant advancements in both gas transmission efficiency and minimal gas distortion. his paper constructs an experimental platform for the positive pressure beam tube monitoring system to investigate the selection and integration of booster output equipment, the impact of pipeline size variations on gas transmission characteristics, and the correlation between driving pressure and output pressure. The following conclusions are obtained:
(1) By employing a graded compression positive pressure gas conveying device with an inter-stage cooler, the operation of the pump body’s compressed gas approaches isothermal compression. This setup increases the effective cylinder volume 
, thereby enhancing volume efficiency and boost output efficiency
. Additionally, the device prevents overheating during prolonged operation and achieves a gas output effect spanning negative pressure to high positive pressure.
(2) Lengthening the negative pressure gas collection section causes the negative pressure of collected gas to decay exponentially, thereby diminishing the gas recovery and transmission efficiency of the beam tube. Conversely, extending the positive pressure transmission pipeline necessitates higher output pressure to maintain gas transmission efficiency. Experimental findings from pipelines of varying diameters reveal that the 7 mm pipeline demonstrates the shortest transmission delay, higher flow rates, and necessitates lower output pressures compared to the other diameters. Hence, the 7 mm internal diameter compressed air pipeline emerges as the optimal choice for positively pressurized gas transport.
(3)Experimental results under varying driving air pressures from 0.2 MPa to 0.8 MPa indicate that the rate of output pressure increase initially rises and then declines, stabilizing after 0.65 MPa. Therefore, it is concluded that within the range of 0.2 MPa to 0.8 MPa, 0.65 MPa represents the optimal operating pressure for the driving device.
Electronic supplementary material
Below is the link to the electronic supplementary material.
Acknowledgements
Thanks to the suggestions made by teacher Qingsong Zhang and Hui Zhuo during the research and the revision and editing of the article when it is completed.
Author contributions
Data processing writing-original draft, W.-J. L.; Writing-review and editing, Q.-S. Z. & H. Z.;construction of the experiment platform, X. Z., C.-P. Y., H.-X. W., C.-Y. X. & R. L. All authors have read and agreed to the published version of the manuscript.
Funding
National Natural Science Foundation of China (52204192); Anhui Province Excellent Research and Innovation Team Project for Universities (2022AH010051); Anhui Provincial Key Research and Development Project (2022m07020006); Scientific Research Foundation for High-level Talents of Anhui University of Science and Technology (2021yjrc42); Open Fund of Anhui Provincial Engineering Technology Research Center (Anhui University of Science and Technology) for Safe and Efficient Mining (SECM2203).
Data availability
The data supporting the results of this study can be obtained from the correspondents and supplementary information according to reasonable requirements.
Declarations
Competing interests
The authors declare no competing interests.
Footnotes
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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Data Availability Statement
The data supporting the results of this study can be obtained from the correspondents and supplementary information according to reasonable requirements.