Gas Flow Rate Distribution Research Articles

Design and experimental research of a rolling-adsorption wall-climbing robot

PurposeWith the popularity of high-rise buildings, wall inspection and cleaning are becoming more difficult and associated with danger. The best solution is to replace manual work with wall-climbing robots. Therefore, this paper proposes a design method for a rolling-adsorption wall-climbing robot (RWCR) based on vacuum negative pressure adsorption of the crawler. It can improve the operation efficiency while solving the safety problems.Design/methodology/approachThe pulleys and tracks are used to form a dynamic sealing chamber to improve the dynamic adsorption effect and motion flexibility of the RWCR. The mapping relationship between the critical minimum adsorption force required for RWCR downward slip, longitudinal tipping and lateral overturning conditions for tipping and the wall inclination angle is calculated using the ultimate force method. The pressure and gas flow rate distribution of the negative pressure chamber under different slit heights of the negative pressure mechanism is analysed by the fluid dynamics software to derive the minimum negative pressure value that the fan needs to provide.FindingsSimulation and test results show that the load capacity of the RWCR can reach up to 6.2 kg on the smooth glass wall, and the maximum load in the case of lateral movement is 4.2 kg, which verifies the rationality and effectiveness of the design.Originality/valueThis paper presents a new design method of a RWCR for different rough wall surfaces and analyses the ultimate force state and hydrodynamic characteristics.

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%.

Analysis of various mathematical models of turbulence when calculating the gas dynamics in a classifier with coaxially arranged pipes

This scientific article deals with the problem of choosing the mathematical model for calculating the gas dynamics in a classifier with coaxially arranged pipes. Various mathematical models were analyzed in ANSYS Fluent software package. Laminar, Spalart-Allmaras, k-ω, RSM and Transition SST were considered as mathematical models. The influence of number of cells in the calculation grid on the pressure loss change in the classifier for various mathematical models was also analyzed. The results of study showed that the pressure loss in the classifier with coaxially arranged pipes is not more than 395 Pa at the inlet gas flow rate of 10 m/s. Among the considered models i.e. laminar, Spalart-Allmaras, k-ω, RSM and Transition SST, the most adequate one is Transition SST model. When changing the number of cells in the calculation grid from 1241551 to 3159388 for this model, the deviation of pressure loss in the classifier was 0.43%. The article includes an equation for the dependence of pressure loss in the classifier on the inlet rate. The distribution of gas flow rate over various sections of rectangular gaps is shown.

LSTM Model Based on Multi-Feature Extractor to Detect Flow Pattern Change Characteristics and Parameter Measurement

In the field of petroleum multiphase flow research, accurate measurement of oil-gas two-phase flow parameters is the research focus. This paper analyzes the changing characteristics of the flow pattern of oil-gas two-phase flow and measures the parameters. The experimental phenomenon shows that under different oil and gas flow rate, the flow patterns upstream and downstream of the venturi tube will change to varying degrees. The Convolutional Neural Network often used in the study of flow patterns, but the flow pattern recognition by the CNN model cannot consider the time series relationship. Therefore, this paper proposes a multi-feature extractor-based LSTM (MFE-LSTM) model to predict the parameters. First, the flow pattern features are extracted through the CNN model, and then the features extracted from different CNN models are combined to form a sentence. The relationship between different words in a sentence and different sentences is explored through the LSTM model. The MFE-LSTM algorithm analyzes the changing relationship between flow patterns with time series and spatial position. In addition, in this paper, the flow pattern horizontal splicing model and the flow pattern channel superposition model are designed. In this experiment, the distribution of oil flow rate is 1- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10~ m^{3}/h $ </tex-math></inline-formula> , the distribution of gas flow rate is 20- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$150~ m^{3}/h $ </tex-math></inline-formula> , and the distribution of GVF (gas void fraction) is 0.25-0.95. The experimental results show that the MFE-LSTM model has the best prediction effect. The average prediction relative error of gas flow rate is 0.387%. The average prediction relative error of oil flow rate is 2.081%.

The Effects of Bottom Blowing Gas Flow Rate Distribution During the Steelmaking Converter Process on Mixing Efficiency

Featuring the advantages of top-blown and bottom-blown oxygen converters, top and bottom combined blown converters are mainstream devices used in steelmaking converter. This study adopted the FLUENT software to develop a numerical model that simulates 3D multiphase flows of gas (air and argon), liquid steel, and slag. Ten numerical experiments were conducted to analyze the effects that the bottom blowing gas flow rate distribution patterns (uniform, linear fixed total flow rate, linear fixed maximal flow rate, and V-type) and bottom blowing gas flow distribution gradients of combined blown converters exert on slag surface stirring heights, flow field patterns, simulation system dynamic pressures, mixing time, and liquid steel–slag interface velocity. The simulation results indicated that the mixing efficiency was highest for the linear fixed total flow rate, followed by the linear fixed maximal flow rate, V-type, and uniform patterns. The bottom blowing gas flow rate distribution exhibited linear patterns and large gradients, and high bottom blowing total flow rates increased the mixing efficiency substantially. In addition, the results suggested that even when bottom blowing total flow rate was reduced, adopting effective bottom blowing gas flow rate distribution patterns and gradients could improve the mixing efficiency.

Experimental and numerical analysis of gas distribution in molten carbonate fuel cells

Flow maldistribution through the cell package affects the efficiency of the fuel cells, thus limiting the reliability and the diffusion of such a technology. This subject is a key-point in the progress of the fuel cells, so deserving the greatest attention and the most thorough research. This paper faces the issue by evidencing the possibility to improve the quality of flow distribution through an appropriate design based on the use of numerical methods. In particular, this research deals with the gas flow rate distribution in a Molten Carbonate Fuel Cell (MCFC) and with the effect on maldistribution of baffles inserted into the inlet manifolds. To this extent, an experimental set-up was built to analyze the flow field inside the cell: the test section reproduces full-scale inlet manifolds for the anodic and cathodic supply of a MCFC stack of 150 cells. Experimental runs covered start-up as well as loading conditions. Air was used to simulate actual flow conditions inside the fuel cell package, basing similarity on inlet Reynolds numbers equivalence. Gas flow rate distribution has been evaluated by measuring the exit velocity at the outlet of the experimental set-up, operating at different working conditions for both cathode and anode, with and without the presence of baffles inside the inlet manifolds. Uneven distributions were observed for high mass flow rates at the cathode manifold without baffle. For the anode, manifold flow distribution resulted acceptably uniform for all working conditions. The baffle improved the distribution for both cathode and anode manifold; particularly, sharp peaks of velocity observed for cathode in the absence of the baffle disappeared at all. Then, velocity and flow rate distributions were modelled by means of a 3D computer code. In order to validate the accuracy of the model, calculated results were compared with experimental data; as a result, their agreement was very good and suggested the opportunity of a manifold design based on a numerical approach. The numerical model was finally utilized to predict flow rate distributions for all working conditions, by taking into account the detailed actual geometry of the manifolds. Numerical analysis of flow rate distribution by means of specific indexes permitted to better understand critical conditions and the reasons of maldistribution. The model was finally used to analyze various design solutions and get a more uniform gas distribution of flow rates. Thus, the numerical modelling can be effectively used during FC plants’ design to analyze the flow distribution, by taking into account devices and systems in order to improve the uniformity of the distribution. In this way, the numerical modelling permits to avoid expensive and time-consuming experiments, and to optimize, with a limited effort, the manifolds according to the cell package characteristics and mass flow rates.

Examination of optimal separator shape of polymer electrolyte fuel cell with numerical analysis including the effect of gas flow through gas diffusion layer

This work concentrates on the effects of channel depth and separator shape on cell output performance, current density distribution and gas flow condition in various conditions with PEFC numerical analysis model including gas flow through GDL. When GDL effective porosity was small, the effect of gas flow through GDL which was changed by channel depth on cell output performance became large. However, current density distribution was ununiform. As GDL permeability became larger, cell output density increased, but current density and gas flow rate distribution were ununiform. From the results of changing the gas flow rate, it was found that the ratio of the minimum gas flow rate to the inlet flow rate depended on channel depth. Furthermore, the optimal separator, which increased output density and made the current density distribution and gas flow rate distribution uniform, was examined. It was also found that cell performance had possible to be developed by improving the turning point of the serpentine separator.

Investigation into maldistribution in a circulating fluidized bed

Experiments on maldistribution were conducted in a 8.5 m high, 1 m×0.3 m cross-section circulating fluidized bed equipped with a 33 bubble-cap distributor. There exists an uneven distribution in flow rate, the bubble caps in the center region having larger flow rates than those next to the wall. Flow resistance has been found to be the dominating factor influencing gas flow rate distribution. Increasing superficial gas velocity improves flow rate distribution for a low pressure-drop distributor. For a high pressure-drop distributor, superficial gas velocity has little effect on flow rate distribution. A ratio of maximum flow rate through a bubble cap to average flow rate through all bubble caps ( V max/ V av) characterizes the flow rate distribution. Distributor-to-bed pressure drop ratio (Δ P d/Δ P r) is another necessary parameter to achieve even flow distribution. A correlation between these two ratios is developed for predicting flow rate maldistribution in CFB bubble-cap distributor.

Stacking Direction Gas Flow Characteristics in a Molten Carbonate Fuel Cell Stack.

A molten carbonate fuel cell (MCFC) stack using internal manifold and co-flow configuration has been recognized as a key structure for commercial plants. In a conventional stack, it is more difficult to obtain a uniform gas flow in the stacking direction than in a stack using an external manifold configuration. The uniformity of gas flow rate in each stacked cell affects the cell performance, and careful design of the gas flow rate distribution in the stacking direction is required. In this study, the stacking direction gas flow characteristics in a plate heat exchanger type MCFC stack were examined by numerical analysis. A stack consisting of 100 cells was assumed, and the fuel gas flow was calculated under various manifold section sizes, gas utilizations, and pressure conditions. The junction pressure losses and electrochemical reactions, which mainly affect the stacking direction gas flow, were considered. Considering the effect on the cell performance, a design guideline for the flow uniformity in the stacking direction was discussed.

Heat and Gas Flow Characteristics in an MCFC Stack. Effect of Gas Flow Rate Distribution on Cell Plane Temperature.

It is useful to analyze the internal temperature distribution of a molten carbonate fuel cell (MCFC) stack for the purpose of realizing the high performance and stable operation. In this paper, we developed a network model that can analyze pressure, current density and temperature distribution for cathode gas counter-flow type stack. The calculation result showed good agreement to the experimental temperature distributions, so this analysis model could be an effective method to analyze the stack performance. Using this model we proposed the gas flow type stack that can realize the uniform temperature distribution. The proposed gas flow type stack showed higher cell voltage because the higher average temperature has been accomplished.

Particulate behaviour in cyclone separators with secondary gas extraction

Particulate collection and gas flow field measurements have been made in a laboratory model nine-cell multicyclone with three different secondary gas extraction geometries. Extraction via a central nozzle in the common collection hopper gave the maximum reduction in particulate emission. The beneficial effect of secondary extraction could not be attributed to improved uniformity of gas flow rate distribution among the cells. The numerically-predicted efficiency gain for extraction from the base of a single cell was considerably less than that measured in the multicyclone.

A Study of Inlet Flow Distortion Effects on Automotive Catalytic Converters

This paper will focus on the influence exerted by a nonuniform flow distribution at the inlet of oxidizers to catalytic converters on conversion efficiency evaluated channel by channel. To this aim the flow inside the whole domain, constituted by the exhaust manifold and an elliptic-cross-sectional pipe connecting it with the converter shell, is simulated by means of a three-dimensional fluid-dynamic viscous model. In this way, after assigning typical converter size and geometry (i.e., elliptic) the gas flow rate distribution can be described at its inlet surface, also varying the total mass flow rate. After calculating the flow field at converter inlet by means of a three-dimensional model, evaluation is possible of local flow distortion in comparison with the ideal conditions of constant velocity of the gas entering the honeycomb converter channels. The abovementioned distorted flow field is then assigned as a local boundary condition for another model, developed by the authors, able to describe, through a one-dimensional fluid-dynamic approach, the reacting flow into the converter channels. It was also shown that, due to this flow distortion, honeycomb converters are not uniformly exploited in terms of pollutants of different quantities to be converted in each channel (i.e., a nonuniform exploitation of all the metals coating the ceramic monolith). Finally, the positive effects determined by a diffuser upstream of the converter on flow distribution are analyzed.

不均一分布を考慮した高炉モデル

In order to clarify the effects of radial distribution patterns of the burdens on the are reduction, heat transfer between gas and solids, and other operational results, a mathematical model taking account of an uneven radial distribution is presented.The blast furnace is divided annularly into center, intermediate and peripheral zones, to all of which the mathematical model presented before can be applied by assuming the plug flow and uniform distribution of gas as well as of burdens. The distribution of gas flow rate to the three zones is regarded to be so determined as that gas pressure is equal everywhere in any horizontal section of the furnace under the radially different gas permeability due to radial distribution of ore/coke ratio. The calculation is carried out so as to make the mean of coke temperatures at the tuyere level equal to a predetermined value under a given o/c distribution.The results of the calculation show that the increase of CO-utilization by about 1.8% and the saving of coke consumption by about 10kg/t-metal may be expected under the condition of uniform distribution in comparison with the distribution pattern in the 22th campaign of the experimental blast furnace.