Gas Flow Distribution Research Articles

Manifold geometry optimization and flow distribution analysis in commercial-scale proton exchange membrane fuel cell stacks

The manifold structure in high-power Proton Exchange Membrane Fuel Cell (PEMFC) stacks critically influences airflow distribution, thereby affecting stack performance, temperature uniformity, and longevity. Therefore, this paper explores how manifold geometry affects fluid distribution within the manifold of a fuel cell stack. In addition, a new step-shaped manifold structure is established to improve the manifold flow field structure and enhance the uniformity of gas flow distribution in each single cell. In our study, each cell within the stack is modeled as a porous medium. We examine how varying the height at different positions within the manifold impacts the uniformity of gas flow distribution, focusing on different length ratios and heights. Our results demonstrate that adjusting the manifold shape improves airflow uniformity, with length ratios having a more pronounced impact than height variations. Specifically, the mass flow coefficient of variation decreased by 22.62 % and 23.07 % for cases 9 and 12, respectively. Similarly, the velocity inhomogeneity coefficient in the inlet manifold decreased by 21.22 % and 21.34 % for cases 9 and 12, respectively. Additionally, pressure distribution in case 9 showed greater uniformity. Our findings indicate that a manifold shape with a length ratio of 2/3 and a height of 2.5 mm delivers optimal performance.

Optimising the feeding system for improving pellet distribution levels in gas-based shaft furnace based on the improved analytic hierarchy process

To improve the gas flow distribution inside the gas-based shaft furnace and ensure the chemical reaction, the discrete element method was used to calculate the effects of revolving chute inclination, particle size mass distribution, particle size distribution width, and hopper angle on the pellet distribution indicators (particle segregation, porosity, gas permeability and feeding time). An improved analytic hierarchy process was presented to fully analyse the nine schemes set up as part of the research. The findings demonstrated that the positive segregation of small particles at the furnace's centre and wall occurred with several feeding systems. The largest influences on porosity were differences in particle size mass distribution and particle size distribution width, and an increase in the proportion of small particles resulted in a significant decrease in porosity. The increase of the mass ratio of large particles made the highest permeability, but also caused uneven distribution of the furnace charge along the radial direction. The simulation results and the ranking of benefits and drawbacks produced by the improved analytic hierarchy process approach agree, demonstrating the applicability of the method to optimise the feeding system as well as its value in identifying the major influences on the feeding system.

Spatio-temporal and multi-mode prediction for blast furnace gas flow

The reasonable and stable distribution of blast furnace (BF) gas flow is the basis for maintaining the smooth operation of BF. Therefore, the accurate detection of the gas flow distribution is essential in the BF ironmaking process due to the direct impact on productivity, stability, and efficiency. However, there is a significant challenge to capture the complex interactions and dynamic changes of the ironmaking process by single predictive mode and two-dimensional (2D) distribution, leading to a lack of flexibility and interpretability in dealing with different abnormalities. To address this issue, a novel spatio-temporal multi-mode approach for three-dimensional (3D) BF gas flow prediction is proposed in this article. First, Pearson correlation analysis is employed to evaluate correlated variables in the spatial dimension. The precise temporal correlations among the multiple variables are matched with mutual information (MI) to extract spatio-temporal variables. Next, the spatio-temporal variables are decomposed utilizing variation mode decomposition (VMD), and the noise is removed with integrated correlation analysis and Fourier transform (FT) to identify and retain the relevant information. Finally, the MI-VMD-Informer is innovatively proposed to establish three different prediction modes based on spatio-temporal features, thus obtaining 2D and 3D gas flow distributions. The superiority of the proposed method is verified by actual BF production data.

Effects of particle size composition and burden ratio on burden segregation in the blast furnace throat based on DEM

In blast furnace charging, burden segregation affects the distribution of gas flow and the efficiency of chemical reactions, which in turn impacts the overall efficiency and quality of ironmaking. This work developed a bell-less top charging model based on the DEM to analyze burden segregation at the furnace throat under various particle size compositions, chute inclinations, and burden ratios. The results show that the burden exhibits a ring-like distribution around the furnace throat, with smaller particles concentrated in the inner ring near the center. When particle size difference of the burden is significant, adjusting the proportion of large or small particles has a more pronounced effect on particle size segregation near the center of the blast furnace. The smaller the chute inclination, the more serious the particle size segregation of the burden. Pellet tends to accumulate near the center of the blast furnace, with a segregation index reaching 0.8 in this region. Adjusting the burden ratio has a more pronounced effect on the segregation of sinter. This work provides theoretical support for charging optimization in blast furnace operation.

A Self-Adaption Growth Model for the Burden Packing Process in a Bell-Less Blast Furnace

The burden structure directly decides the distribution of gas flow inside a blast furnace (BF). Falling, stacking, and descending bulk materials are the three main processes for burden formation, among which the stacking process plays a decisive role. The Discrete Element Method (DEM) and theoretical modelling were combined to predict stacking behavior in this study. Falling and stacking behaviors were first simulated based on DEM. The repose angle during the stacking process and mass fraction distribution in the radial direction were analyzed. Then, the upper, centroid, and lower trajectory falling lines were determined, and a polynomial relation was found between the angle and the packing height. The influences of three parameters on the repose angle were investigated. Compared with the natural repose angle and chute inclination angle, the effects of the trajectory line depth appeared trivial. The polynomial relation between the repose angle and the packing height was specified to be a function of the natural angle of repose and the chute inclination angle. A three-trajectory falling model and quadratic expression were embedded in the theoretical model, yielding a self-adaption packing model. The model was proved reliable with a low relative error, below 15%.

Fabrication of diamond film under low methane concentration by hot filament chemical vapor deposition with magnetic field assistance

This study focused on improving diamond film growth through hot filament chemical vapor deposition (HFCVD) with an innovative method, magnetic field assistance. The effects on diamond films were thoroughly investigated using a combination of experiments and simulations. The results of scanning electron microscopy (SEM), Raman spectroscopy, and X-ray diffraction (XRD) all showed significant improvements in nucleation rates, film thickness, and grain size, particularly for grains with (111) orientation, when exposed to a 400 mT magnetic field during HFCVD compared to non-magnetic conditions. Magnetic field application in HFCVD was found to promote the formation of larger diamond grains and increase the film growth rate by nearly 45 %. Concurrent Finite Element Method simulations confirmed that the magnetic field improved reactive gas flow and temperature distribution across the substrate, which was consistent with experimental results. These findings suggest that magnetic field assistance in HFCVD may mitigate the limitations of bias assistance, such as the antenna effect, overheating, and stress imbalance. This approach is especially useful for substrates with complex geometries, such as the sharp edges of cutting tools, as it promotes even film growth.

The high-temperature gas soft measurement method based on the temperature attenuation patterns of flowing argon gas inside a cavity

The device for generating the airflow temperature signal is employed in aircraft ground simulation. This process involves heating the argon gas by the arc discharge to generate high-temperature gas, which subsequently flows into the cavity and mixes with cold gas to produce the temperature signal. However, the temperature of argon gas at the entrance of the cavity is excessively high, and sensor installation is challenging, making direct measurement difficult. This paper introduces a high-temperature gas soft measurement method based on the temperature attenuation patterns of flowing argon gas inside the cavity, and establishes a mathematical model for the flow and temperature distribution of argon gas within the cavity. The method calculates the target temperature at the entrance of the cavity by measuring the lower-temperature argon gas at the outlet of the cavity. Furthermore, a simulation and experimental platform were set up to validate the proposed method. The experimental results indicate that there is a 7.9% deviation between the soft measurement values and the directly measured values of argon gas temperature in the middle of the cavity. At the outlet of the cavity, the maximum deviation between the directly measured argon gas temperature and the simulation calculation results based on the soft measurement values at the entrance temperature is 5.2%. The paper rigorously validates the accuracy of the soft measurement method from various perspectives. Notably, this method offers the advantage of remote indirect measurement, and indirectly expanding the upper limit of the temperature sensor.

Application of laser surface detection technology in blast furnace gas flow control and optimization

Abstract The gas flow distribution inside a blast furnace affects its smelting. Laser surface detection technology can control the gas flow distribution and promote the stable and smooth running of blast furnace by observing and adjusting the surface condition in the blast furnace in real-time. The laser surface inspection technology in blast furnace gas flow control and optimization was introduced, with Masteel 4,000 m3 blast furnace as an example. The results showed that the 30 W high-power laser had good penetration performance and could obtain clear scanning images of the material surface. In the process of strengthening smelting, the laser detection system determined that the central airflow of blast furnace was insufficient, resulting in a decrease in furnace condition stability, and promptly took measures to adjust the angle of the mineral coke fabric equipment and lifting line. After adjusting the material line, the central airflow was properly suppressed and stabilized, the angle of edge platform increased, the airflow developed properly, and two suitable gas flows were formed, which finally stabilized the furnace condition. Meanwhile, the small duct airflow other than the central airflow was found in time through the laser detection system, which provided conditions for operators to take measures to effectively eliminate the duct airflow, thereby avoiding big impacts on the blast furnace operation and technical and economic indexes. Therefore, the laser surface detection technology could effectively judge the gas flow distribution in the furnace, which contributed to timely adjustment of process parameters and optimization of blast furnace operation.

Study on the High-Temperature Interaction between Coke and Iron Ores with Different Layer Thicknesses.

Coke plays a key role as the skeleton of the charge column in BF. The gas path formed by the coke layer in the BF has a decisive influence on gas permeability. At high temperatures, the interface between coke and ore undergoes a melting reaction of coke and a reduction reaction of ore. The better the reducibility of the ore, the more conducive it is to the coupling reaction of ore and coke. The melting loss reaction of coke becomes more intense, and the corresponding strength of coke will decrease, which will affect the permeability of the blast furnace and is not conducive to the smooth operation of the blast furnace. Especially with a deterioration in iron ore quality, BF operation faces severe challenges, which makes it necessary to find an effective way to strengthen BF operation. In this study, a melting-dropping furnace was used to develop and clarify the high-temperature interaction between coke and iron ores with different layer thicknesses. The influencing factors were studied by establishing a gas permeability mathematical model and observing the metallographic microscope images of samples after the coke solution loss reaction. The relationships between coke layer thickness, distribution of gas flow, and pressure drop were obtained. The results showed that, under certain conditions, the gas permeability property of a furnace burden has been improved after the coke layer thickness increased. Upon observing the size of coke particles at the interface reaction site, the degree of melting loss reaction can be determined. A smaller particle size indicates more melting loss reaction. A dripping eigenvalue for molten metal was introduced to evaluate the dynamic changes in the comprehensive dripping properties of molten metal of furnace burden, which showed that the dripping eigenvalue for the molten metal could deteriorate because of the unruly thickness and the coke layer thickness should be limited through considering the operational indicators of the blast furnace.

Emission and spatial variation characteristics of odorous pollutants in the aerobic tank of an underground wastewater treatment plant (UWWTP) in southern China

In this study, the spatial concentration of odorous pollutants in the aerobic tank of an underground wastewater treatment plant (UWWTP) in southern China is monitored. The odour activity value, odour contribution rate, and chemical concentration contribution rate are used to evaluate the degree of contribution of odorous substances. Computational fluid dynamics (CFD) simulations of odorous pollutant diffusion are also established. The study shows that the odorous substances detected in the aerobic tank mainly included ammonia (NH3), hydrogen sulfide (H2S), trimethylamine (C3H9N), and methanethiol (CH3SH), and their concentrations are 1.160, 0.778, 0.022, and 0.0006 mg/m3, respectively. The total odour activity value of the aerobic tank is 450.72 (dimensionless), of which the odour activity value of H2S is 432.22, and the contribution rate reaches 95.9%. H2S is the main contributor to odour and a key controlled substance. The air inlets and exhaust outlets in the aerobic tank are cross-arranged at the top of the space, and the CFD model of odorous pollutant diffusion shows that the gas flow organization determines the odorous pollutant diffusion. The spatial distribution of gas flow and odorous substances in the aerobic tank is relatively uniform, and the odour collection efficiency is higher. The production flux and production coefficient of H2S in the aerobic tank are calculated as 25.831 mg/(m2·h) and 14.149 mg/t, respectively. This study determines the reasonable air supply and exhaust design of the aerobic tank, the number of odour pollutants, and the key controlled substances. These findings offer guidance and serve as useful references for the prevention and control of odour pollution in aerobic tanks of the same type of UWWTPs.

An Electrochemical Performance Model Considering of Non-Uniform Gas Distribution Based on Porous Media Method in PEMFC Stack

Proton exchange membrane fuel cell (PEMFC) is significant and favorable to the long-range and short refueling time in the vehicle industry. However, the non-uniform distribution of gas flow supply, particularly in the fuel cell stack is neglected in the electrochemical model for PEMFC performance optimization. The purpose of this study is to break through this limitation to establish an optimized electrochemical fuel cell performance model, with porous media methods considering the non-uniform gas flow distribution in fuel cell stack with different compression of the gas distribution layer (GDL). The numerical models are validated by experimentation of a practical fuel cell stack. For the established fuel cell model, there is a 5% difference between the maximum and minimum speeds of various flow channels in the anode flow field under 10% GDL compression. Furthermore, the single-channel electrochemical performance model is optimized by considering the non-uniform gas flow distribution of the fuel cell stack. The results of the optimized electrochemical fuel cell performance model demonstrate that the correlation coefficient between the experiment results and the simulation results is nearly 99.50%, which is higher than that of the original model under 20% GDL compression. This established model is effective in enhancing the prediction accuracy of the PEMFC performance.

A novel detection method for ore-coke ratio of blast furnace based on structure-texture entropy of images

The ore-coke ratio is crucial for regulating gas flow distribution, enhancing permeability, and ensuring smooth operation of the blast furnace. Direct detection of the ore-coke ratio, leveraging the structure and texture differences in ore and coke images, is a widely accepted method. The harsh environment of the blast furnace results in unclear burden surface images, making it challenging to differentiate between ore and coke. This complicates image-based direct detection for ore-coke ratio, with few studies addressing this issue. This paper firstly introduces a structure-texture entropy, grounded in information entropy, to effectively differentiate between ore and coke. Then, a structure-texture enhancement algorithm based on image extreme dark features is proposed to optimize the accuracy of the structure-texture entropy. Finally, based on the high-accuracy structure-texture entropy, a novel algorithm for burden surface area extraction is presented. This method uses feature vector clustering and functional optimization for real-time ore-coke ratio detection. Industrial experiments demonstrate that the proposed method achieves high-accuracy ore-coke ratio detection, meeting the requirements for long-term stability of the blast furnace.

System for recognizing gas flow distribution patterns in blast furnace centre based on computer vision

System for recognizing gas flow distribution patterns in blast furnace centre based on computer vision

Optimization of gas extraction of producing wells to increase the efficiency of condensate production

The article discusses ways to increase the efficiency of condensate production due to the optimal distribution of gas flows between producing wells. For a large number of wells, the solution of this problem becomes nontrivial and requires special methods of nonlinear optimization. The main aim of research is obtaining accurate solutions to the problem of optimizing condensate production using direct dependencies between gas and condensate production. The minimum set of reliable field information has been determined, which allows solving the problem of optimal distribution of gas production between wells at the maximum condensate flow rate. An optimization problem is formulated for this model. The conditions under which the initial problem is divided into a system of optimization subtasks for subgroups of wells are considered. By the method of pairwise optimization, analytical expressions were found for optimal ratios of gas flow rates in a group of wells. Based on the expressions obtained, an algorithm has been developed for the exact solution of the problem of short-term optimization of the well operation mode.

Characteristics analysis of multi-channel ceramic membranes for dilute gas absorption in falling film operation

Capturing dilute gases has posed a significant challenge due to the extremely low mass transfer driving force associated with them. Falling film-based absorption using porous membranes emerges as a promising technology for gas separation, offering a substantial gas–liquid interface area while simultaneously eliminating mass transfer resistance within pores that is inherent in hydrophobic membrane-based absorption processes. In this study, we investigated the mass transfer performance of multi-channel ceramic membranes in falling film-based dilute CO2 absorption under various gas and liquid operating conditions. Experimental tests and computational fluid dynamics (CFD) simulations were conducted to examine the effects of pore size and geometrical configuration on the distribution of liquid and gas flows across different channels. Simulations indicated that the optimization of multi-channel ceramic membranes for the falling film-based dilute gas absorption should prioritize achieving a more rational distribution of gas–liquid flows. When the disparity between liquid and gas distribution in the outermost channels exceeded 40%, as opposed to cases where the difference was within 20%, there was a reduction of over 50% in mass transfer performance.

Совершенствование конструкции насадочных аппаратов за счет равномерного распределения газового потока

The modern technical level of solving the problem of efficient operation of adsorbers due to the uniform distri-bution of gas inside the apparatus is considered in detail and ways to improve the adsorbers are proposed. The disadvantages of modern designs of adsorbers and the areas of their use are noted. A brief critical analysis of the designs of devices for uniform loading of adsorbent is given. Based on the analysis and experimental studies, the design of the apparatus has been developed, which ensures a uniform distribution of gas flows inside the apparatus. The objective of the experimental studies was to evaluate the characteristics of the developed design of the apparatus for gas adsorption from gas mixtures. Simplicity of dense uniform loading of adsorbent, increase of process efficiency, low hydraulic resistance of the device are provided. To solve these tasks, an experimental setup has been developed to study the efficiency of the adsorption process using the example of adsorption silica gel of water vapor from a mixture with air. It has been experimentally confirmed that the device has competitive advantages. The design provides a tightly packed adsorbent layer, without voids, which means that the uniformity of the load layer in terms of wear and moisture is ensured. In the design of the adsorber, the possibility of entrainment of adsorbent particles during reverse purging is excluded. The design allows you to flexibly change the performance. The total cross-sectional area of the adsorbent increases in proportion to the vertically number of adsorption baskets. An increase in the number of cycles of the adsorption process will entail an increase in the adsorption capacity of the adsorbent. The design of the device helps to reduce energy consumption, reduce capital costs and increase the productivity of the adsorption plant. The introduction of the adsorber into the technology will ensure reliable operation, energy efficiency and high quality of the process.

Study on the effects of manifold structure on the gas flow distribution uniformity of anode of PEMFC stack with 140-cell

The gas maldistribution of the large proton exchange membrane fuel cell (PEMFC) stack leads to the deterioration of power performance. This numerical investigation studies the gas flow rate distribution in anode of two U-type stacks (a 15-cell stack and a 140-cell stack) which are composed of the same type of unit fuel cells. The anode gas channels of the two stacks are regarded as porous medium whose characteristic parameters are determined from pressure drop test data. To consider the nitrogen permeation from cathode to anode gas channel during the purging process, an expression of an additional momentum source term is proposed which helps to better fit the simulation results with pressure drop test data. Results show that the anode of the 140-cell stack has a quite good flow distribution uniformity. However, its asymmetric feed header of the manifold structure still has some negative effect. The same 140-cell stack installed with a rotational symmetric feed header is investigated and the simulation result shows that it can reduce the original maximum non-uniformity by about 50%.

Reducing boiler maintenance costs with improved materials for air-heater tubes

Corrosion of boiler air-heater tubes costs the industry several million dollars each year in repairs, reduced boiler steam output and reduced boiler efficiency. There have been many cases where the reduced boiler steam output caused by leaking air-heater tubes has reduced factory crushing rates and electricity export. Corrosion of air-heater tubes can, in many cases, be minimised by improving the gas and air flow distributions with turning vanes and ductwork redesign, but in nearly all cases, there are some tubes on the cold air side of air-heaters that are still susceptible to dew-point corrosion. Using improved tube materials in parts of boiler air-heaters that are susceptible to dew-point corrosion will significantly extend air-heater life. Available materials and coatings were reviewed, and laboratory- and factory-scale trials, metal temperature measurements, dew-point calculations and a financial analysis-based ranking of commercially available tube materials were undertaken. S-TEN 1 had a similar corrosion performance to SS304 stainless steel. Both the S-TEN 1 and SS304 stainless steel tubes had significantly greater resistance to dew-point corrosion than the carbon-steel tubes typically used in the air-heaters of Australian sugar factory boilers. The good performance of S-TEN 1 in this project is not consistent with the poor performance of S-TEN 1 (no better than carbon-steel) in earlier trials carried out by Isis Mill. The conditions experienced by the trial tubes in this project were not as severe as those experienced by the tubes in the earlier Isis Mill trials, and this appears to be the main reason for the current improved performance of the S-TEN 1 tubes. This requires further investigation.

Intelligent Prediction and Real-time Monitoring System for Gas Flow Distribution at the Top of Blast Furnace

Intelligent Prediction and Real-time Monitoring System for Gas Flow Distribution at the Top of Blast Furnace

Structural optimization and flow field simulation of gas distribution device in desulfurization tower

AbstractIn order to comply with ultra‐low emission requirements and further reduce the concentration of SO2 emissions from coal‐fired power plants, a novel distributor has been proposed to enhance the uniformity of fluid distribution in the desulfurization tower. The distributor ensures that the inlet flue gas comes into even contact with the slurry droplets ejected from the nozzle, thereby improving the removal efficiency of SO2. The research focuses on a circular desulfurization tower using ammonia‐based desulfurization. To study the enhancement of non‐empty tower desulfurization efficiency, a CFD‐DPM model based on the Euler–Lagrange method has been established. The accuracy of the model has been verified through comparison with experimental or validated data, ensuring its reliability in predicting the performance of the proposed distributor in enhancing desulfurization efficiency in the circular desulfurization tower. The simulation results demonstrate that the addition of the new inflow gas distributor leads to a significantly thinner flue gas escape zone in the circular desulfurization tower. The flue gas flow velocity at the wall side of the tower, above the distributor, increases by only about 1 m/s with the rise of the horizontal cross section, and there is hardly any flue gas escape zone observed. The addition of the distributor increases the pressure drop in the local area, while optimizing the flow field in other areas and reducing the turbulent dissipation energy, which in turn reduces the full tower pressure drop from 701 to 474 Pa. Additionally, the flue gas at the outlet of the distributor is uniformly dispersed, with gas velocity distribution unevenness values of 0.558, 0.587, and 0.601, respectively, which are 15.9%, 14.0%, and 14.0% lower than the unevenness value of the empty tower spraying, at a depth of 1 m below each spray layer. These improvements in gas flow distribution and pressure drop contribute to better control of ammonia escape and aerosol phenomenon, while also enhancing the desulfurization efficiency.