Experimental and numerical study of installing a dune model in a 90° bend in the horizontal-vertical pneumatic conveying system

In the pneumatic conveying process,particles move to the bend under the influence of inertia to form a particle rope,which will cause serious wear between the particles and the pipe wall,and then the dune model is designed and installed in the 90° bend to reduce energy consumption and wear in this study.Firstly,the minimum pressure drop velocity of particles transported by different size dune models was obtained through experimental study.Then the energy saving mechanism of the dune model is studied by CFD-DEM coupling.The experimental results show that the installation of the dune model reduces the minimum pressure drop velocity.The numerical simulation results show that the number of collisions between the particles and the tube wall in the vertical tube decreases after the installation of the dune model,which reduces the energy loss.Moreover,the increasing of tail size of the dune model is beneficial to the diffusion and acceleration of the particles in the vertical tube.

Multi-scale analysis on the pulverized coal flow behaviors under high,pressure dense-phase pneumatic conveying

To deeply knowledge of the flow behaviors of pulverized coal particles in dense gas-solid two-phase flow,a multi-scale analysis method based on electrostatic sensor array is applied for the multi-scale characterization of flow behaviors of dense gas-solid flow.The experimental results indicate that:for steady flow,with the increment of conveying pressure difference,the individual particles increase and the particle clusters decrease,the individual particle distribution is always inhomogeneous but the particle cluster distribution tends to be more homogeneous over the cross-section of pipe,while the average flow behavior of pulverized coal particles is always in the relatively static state.For unsteady flow,the average flow behavior of pulverized coal particles is dynamic,and the flow behaviors of the multi-scale flow structures over the cross-section of pipe are all significantly inhomogeneous.Moreover,the effect of particle size on flow behavior of pulverized coal is also investigated and validated.

Experimental study on dense-phase pneumatic conveying of coal powder at high pressures

Clean utilization and conversion of coal resources is significant to China’s energy sustainable development.Entrained-flow coal gasification technology is an important method used for clean and efficient conversion of coal.The characteristics and stability of high-pressure dense-phase pneumatic conveying of pulverized coal is crucial to the safe and stable operation of dry-feed entrained-flow coal gasifiers.Dense-phase pneumatic conveying experiments were carried out using a high-volatile bituminous coal in pipes with diameters of 25,15 and 10 mm,respectively,and at back pressures of 1.0-4.0 MPag.The conveying characteristics and effects of operating and structure parameters were studied.Pressure drop models were established for horizontal and vertical upward conveying.The prediction uncertainty was within±30%for the horizontal conveying and±20%for the vertical upward conveying.The relative standard deviation of solid flow rate was proposed to explain conveying stability.The effect of operating parameters on conveying stability was systematically analyzed.The gas velocity-related criterion was proposed for stable conveying.

An assessment of steady-state conditions in single slug horizontal pneumatic conveying

This study used a 3D coupled CFD–DEM model to assess how slugs tend towards steady state in single slug horizontal pneumatic conveying.Initial slug length,inlet velocity and initial stationary layer fractions were systematically varied for a total of 72 simulations.Previously made observation that slugs tend towards a steady state was confirmed via a theoretical derivation.The derivation shows that slugs move towards their steady state lengths exponentially.This allowed for a calculation of a characteristic time scale which is a measure of how quickly a slug tends towards the steady state.The theoretical estimate which is a function of slug porosity,steady length,velocity and stationary layer fraction has good agreement with simulated results.A link between steady slug length and solids loading ratio was also shown.

Depicting the role of gas–solid interactions on the hydrodynamics of converging pneumatic riser

The understanding of the flow characteristics and effect of gas–solid interactions in pneumatic risers is fundamental to investigate to ensure effective design cost-effective operation.Thus,to understand the effect of gas–solid interactions on the hydrodynamics of newly proposed conversing risers,this study mainly focused on predicting pressure drop in the dilute phase pneumatic conveying system.The experiments were conducted in a converging riser having a convergence angle of 0.2693°.Various solid particles such as sago,black mustard,and alumina have been considered to study the effect of particle sizes and density on the pressure drop.The experimental outcomes indicate that the total pressure drop increases with an increase in the solid density and gas mass flow rate.Moreover,smaller particle sizes are also increased the pressure drop.An empirical correlation is developed for the prediction of total pressure dropΔPTin converging pneumatic riser via dimensional analysis.All dependent variables such as particle and air density,drag force,acceleration due to gravity,the mass flow rate of air and particle,the diameter of particle and converging riser,the height of converging riser were considered to develop the empirical correlation.The established relationship is tested,and experimental data have been fitted for its validation.The estimated relative error of less than 0.05 proved the significance of the developed correlation.Hence,it can be stated that the established relationship is useful in studying the effects of various parameters on the pressure drop across the length of the conversing riser.

About the Change in Air Pressure in the Pipeline during the Pneumatic Transportation of Cotton

The article is devoted to the study of the issues of determining the patterns of changes in air pressure along the length of a pneumatic transmission pipeline for raw cotton at different flow parameters and different pipeline diameters. Theoretical studies have proved the reduction of static and total pressure along the line of pneumatic cotton transportation. The dependence of the pressure change on the diameter of the transport line and the aerodynamic drag of the pipeline is obtained. The results obtained are recommended for use in the design of raw cotton pneumatic transport systems.

Modelling the Influence of Air Jet Configurations on Non-Woven Steel Fibre Mixing in the Melt Overflow Process

The mixing of non-woven steel fibres in melt overflow process for use in automotive muffler systems was simulated. The aim was to identify optimum parameters for achieving a good fibre mix. Numerical models of mixing chambers of melt overflow process were developed. Multiphysics analyses involving heat transfer, fluid flow and particle tracking were carried out using COMSOL code. The influence of air jet configurations on the fibre distribution was studied. The fibres settled on the moving bed within the mixing chamber were examined for their uniformity. The effect of additional air jets to the existing chamber in a range of regions was explored. An optimum configuration was identified by analyzing the compactness of the particle clusters deposited in the simulation and validated using pixel data acquired from real time imaging. The results showed that by employing dual air jets at the front end of the chamber, the density of the fibre material has improved. We conclude that through multi-physics modelling, it was possible to identify the optimum air-jet configurations leading to fibre uniformity and its distribution. This work also paves the way for incorporating a vision system to evaluate fibre density in real time.

Design and Development of Seed Cotton Pre-Cleaner Machinery

The process of transporting and cleaning seed cotton is carried out by passing raw materials through many machines. The efficiency of a cleaner machine depends on many factors and mainly machine design. The cleaner machines clean the seed cotton using mechanical forces, and these forces have a negative effect on the quality of the fiber and seeds. This paper provides results of the experimental research to improve the technology of pre-cleaning seed cotton from foreign matters. The results of research were conducted to reduce the number of machines in the cleaning process and design a new pre-cleaner machine.

Comprehensive Euler/Lagrange modelling including particle erosion for confined gas-solid flows

The present research aims to assess the capability of a comprehensive Euler/Lagrange approach for predicting gas-solid flows and the associated solid particle erosion.The open-source code OpenFOAM®4.1 was used to carry out the numerical simulations,where the standard Lagrangian libraries were substantially extended to account for all necessary models.Particles are tracked considering both translational and rotational motion as well as all relevant forces,such as gravity/buoyancy,drag and transverse lift due to shear and particle rotation.The tracking time step was dynamically adapted ac-cording to the locally relevant time scales,which drastically reduces computational times.Stochastic approaches are adopted to model particle turbulent dispersion,particle collisions with rough walls and particle-particle interactions.Five solid particle erosion models,available in the literature,were considered to estimate pipe bend erosion.Three study cases are provided to validate the adopted nu-merical approach and erosion models extensively.The first case intends to evaluate the ability of the extended CFD code to predict the behaviour of gas-solid flows in pneumatic conveying systems.This goal is achieved by comparing the numerical results with the experimental data obtained by Huber(1997)and Huber and Sommerfeld(1994,1998)in a pneumatic conveying system.Here,the importance of considering inter-particle collisions and surface roughness for predicting particle velocity,mass flux and mean diameter distributions in gas-solid flows is highlighted.The second and third case intend to evaluate the ability of the erosion models in estimating bend erosion in diluted gas-solid flows.The erosion data obtained experimentally by Mazumder et al.(2008)and Solnordal et al.(2015)in very dilut pneumatic conveying systems is used for validating the numerical results,neglecting now inter-particle collisions and two-way coupling.Besides a comprehensive analysis of the different influential properties on erosion,the innovation of the present study is as follows.For the first time also a temporal modifi-cation of the surface roughness due to the erosion was considered in the simulations obtained from previous measurements(Novelletto Ricardo&Sommerfeld,2020).As the surface roughness is increased due to erosion,eventually erosion rate becomes lower.This is the result of diminishing wall collision frequency.Simulations for several degrees of surface roughness showed that larger roughness is coupled with a drastic reduction of erosion.Hence,numerical simulations neglecting wall surface roughness are not realistic.The consideration of a particle size distribution instead of mono-sized computations showed a possible reduction of erosion rate.The detailed analysis of the different single-particle erosion models revealed that the model proposed by Oka et al.(2005)and Oka and Yoshida(2005)yields the best agreement with the measurements,however particle and wall properties are needed.

A new design approach for the established flow region of vertical,dilute-phase pneumatic conveyors

An analysis has been completed for a comprehensive set of vertical,dilute-phase pneumatic conveying pressure drop data from an investigation by Flatow.The data were collected in the established flow region for eight different materials conveyed in 0.05-,0.10-,0.20-m internal diameter,20-m tall steel risers.Particle velocities derived from the pressure drop data were used to develop an equation of motion that includes terms for pipe diameter,terminal velocity,coefficient of restitution,and particle shape.The best data fit was achieved using the actual gas density and the actual gas velocity adjusted for voidage.Adjusting the terminal velocity for voidage,an approach recommended by many investigators,did not improve the fit for reasons identified by the present research.Using the equation of motion,particle velocities were predicted and used to calculate total pressure drops that are within±15%of the measured values.The calculated values also produce the characteristic trough-shaped total pressure drop curves allowing the minimum pressure drop gas velocity to be determined without recourse to a separate correlation.A comparison with other studies using shorter risers indicates that data from these studies likely include acceleration effects.A separate study will investigate this observation further.

A low-error calibration function for an electrostatic gas-solid flow meter obtained via machine learning techniques with experimental data

In this paper,modeling and machine learning with experimental data and a novel calibration function for a gas-solid flow sensor fusion are presented.Sensor fusion is the use of software that intelligently combines data from multiple sensors in order to improve overall system performance.This technique can be applied to measurement of mass flow rate of solids in a pipeline with non-intrusive electrostatic techniques.Data fusion from multiple heterogeneous/homogenous sensors can overcome the limitations of an individual sensor and measured variable.It is shown that the output voltage of a ring-shaped electrode is predominantly a function of solids mass flow rate and velocity for a flow of bulk solids in a pipeline,when particle size,properties and ambient conditions remain constant.By incorporating solids flow velocity in a proposed mathematical model(obtained via machine learning),meter output voltage could be predicted with superior accuracy,for wide range of different flow pa-rameters from numerous experiments with a pneumatic conveying system.Transposing the model yields a new calibration function which,when deployed in signal processing software,enables accurate mass flow measure-ment with velocity compensation.The described method also de-necessitates determination of air solids ratio or solids volumetric concentration,thereby enabling simplification of the overall measurement system whilst yielding higher accuracy than calibration methods from previous studies.Accurate flow measurement facilitates enhanced monitoring and controllability of blast furnaces,power stations,chemical reactors,process plants etc.where there are bulk solids flows in pipelines.Optimization of such highly materially consumptive and energy intensive processes can yield significant reductions in waste and emissions(CO 2,NOx)and increased efficiencies in global production of energy and materials.