Air Inlet Configurations Research Articles

Fluidized bed hydrodynamics under variable air inlet configurations to enhance gasification reactor efficiency: Computational study

This study employs diverse strategies to enhance motion dynamics within the reactor, with a specific focus on the critical geometric parameter of air nozzle configuration. Methodical analysis of various air nozzle angles, 0°, 45o, and 90° relative to the horizontal bottom line is undertaken to discern their influence on these key parameters throughout multiple stages during the recorded flow duration. A CFD model of the physical model is constructed and solved using ANSYS software. Parameters scrutinized include the longitudinal and lateral distribution of particle volume fraction, alongside radial and axial velocities of particles. The results emphasize the significant impact of air-feeding orientation on both radial and axial particle velocities. Notably, 45° air nozzle angle is the best orientation for the fluidized bed reactor displaying maximal values in particle volume fraction fluctuations and bed height. Furthermore, peak values for radial and axial velocity persist consistently throughout the entire flow duration.

Sustainable Energy from Waste: A Feasibility Study in Miri, Malaysia

The growth of urban populations, industrialization, and economic development has led to a surge in solid waste production. When local recycling infrastructure falls short, much of this waste ends up in landfills, causing environmental and social challenges. This study aims to assess the feasibility of converting municipal solid waste (MSW) into energy, with a focus on combustion chamber modeling in Miri, Sarawak. Data on MSW composition are obtained from secondary sources. Ansys Fluent software is used to model the combustion chamber, and simulations are conducted to explore temperature, turbulence, and species distribution. MSW composition illustrates higher substantial fractions, with 39.8% being food waste, followed by 20.7% plastic/rubber. Calorific values range from 4652 kJ/kg for food waste to 32564 kJ/kg for plastic/rubber. Combustion simulations result in maximum flue gas temperatures of 1500 °C, 1200 °C, and 1800 °C under varying air inlet conditions. Turbulence intensities on the grate range from 125% to 174% for these air inlet configurations. The study concludes that moisture content significantly affects calorific value and heat generation during combustion. Higher turbulence intensities lead to increased reaction rates and heat generation, improving the energy efficiency of the process.

Algoritmo genético no projeto de silos de soja visando a homogeneização do fluxo de ar

ABSTRACT One of the main processes used to maintain grain quality in large storage bins is aeration. An optimization model that considers the limited and discrete nature of the air inlets, in addition to the geometric characteristics of the storage bin, could produce results more easily applicable results for the design of new grain storage bins. The objective of this study was to parameterize and to apply the Darcy-Forchheimer model for simulating airflow in soybean grain mass as function of grain layer height, and develop an artificial intelligence method based on genetic algorithm for optimizing grain storage bin dimensions and air inlet configurations to obtain a more homogeneous airflow in the grain mass. The parameterization considered the effect of grain compaction and the OpenFOAM simulations showed good agreement with the experimental data. The proposed genetic algorithm was able to increase the airflow homogenization when compared to the grain storage bin used as reference.

Experimental study and numerical simulation of resistance to airflow in a storage bin of rough rice with three inlet duct configurations

The measurement and estimation of pressure drop through porous beds are important in the design and development of grain drying and aeration systems. Three inlet interconnected channels were designed and developed as inlet duct floors of an experimental grain silo. The channels were formed into shapes resembling the characters E, F and H. The pressure drop and air distribution were evaluated at different airflow rates for use as a small scale on-farm grain silo. It was observed that the pressure drop increased with the airflow rate and the height of the rough rice in the storage bin. Duct configuration of F and H represents the maximum and minimum values for pressure drop, respectively. The pressure at different heights inside the bed was uniform for all three air inlet duct configurations. Hukill & Ives and Ergun equations were used to fit with experimental data. The modified constant coefficients of both equations were determined for each of the three configurations. The Ergun equation fitted best the experimental data for the entire airflows range. Using the modified Ergun equation, a numerical simulation of the flow inside the rough rice bed was performed in the COMSOL Multiphysics software v6.1 and the velocity distribution inside the bed was presented. The simulated results revealed that the bin with H inlet duct configuration has better performance in continuous aeration process compared to E and F configurations, whereas an F duct configuration has better air penetration ability at the bottom and near the centre of the bin.

An Improved Air Distribution System for Infection Reduction in Economy-Class Passenger Airplanes

In a previous work performed by the authors, a Personalized Ventilation (PV) system, combined with Under Floor Air Distribution (UFAD) has been found to provide an air shield between passengers in an airplane and reduce the chances of viruses spreading. A new PV system with a front-back design has been adopted. Combined with UFAD, the new system has achieved thermal comfort for the passengers, as well as a reduction of contaminants spreading. However, the PV system can be further improved by changing the air inlet and outlet configurations. In this work, two new PV system configurations are investigated with changed locations of the air outlets. In addition to an improved air shield between passengers and hence better infection reduction, the new configurations have also improved the predictive mean vote to the value of 0.51, and the predicted percentage dissatisfied to 13.9%.

Influence of burner nozzle configuration, and inlet gas composition on combustion, gas dynamics, temperature and concentration profile in a rotary hearth furnace

ABSTRACT A CDF model for simulating gas dynamics, heat and mass transfer in the freeboard of a pilot-scale Rotary Hearth Furnace (RHF) is developed in conjunction with an independent solid reduction model at the bottom of the hearth. The effect of air-inlet configuration and inlet fuel composition on the fuel requirement, exit gas composition, fluid flow, temperature, and gaseous composition distribution have been investigated using this model. The lower air-inlet tubes orientated at 5° upwards keeping remaining air and fuel tubes horizontal emerged as the most recommended burner configuration. Various alternative fuels categorized in terms of calorific values, demonstrated that the fuel with high calorific value required less fuel and produced less CO2 emission. Interestingly, it was found that for the same calorific value a combination of blast furnace gas and coke oven gas (BF+COG) produced less CO2 emission compared to a combination of COG+BF+NG (Natural gas).

Computational Fluid Dynamics aided investigation and optimization of a tunnel-ventilated poultry house in China

Ventilation system is crucial for poultry houses to control the indoor climate and air quality. The tunnel ventilation system is widely applied for large-scale poultry buildings in China but only limited scientific researches regarding the flow pattern, temperature distribution and design criteria are available in the literature. Thanks to the fast development of computer technology, Computational Fluid Dynamics (CFD) techniques were used in present study to investigate the indoor air movement, air temperature and relatively humidity. A three-dimensional CFD model was built according to the real dimensions of a laying hen house and the model was validated by comparing the simulation results with the field measurements at 30 positions. Meanwhile, statistical analysis was performed to determine the differences between different boundary conditions regarding the agreement between measured and CFD simulated results. Optimization of air inlet configurations was performed by using the validated CFD model and it was found that the uniformity of indoor air movement could prevent excessive local convective heat losses and reduce the temperature at the end of the house. Furthermore, the air inlets placed at the middle of the side wall could significantly reduce the high temperature expected at the end of the building without using extra energy, which is especially important for large-scale poultry farms with long buildings. The performance of side-wall windows was also examined and preliminary guidance was provided to effectively regulate the indoor climate by using these windows with the help of environmental monitoring systems. The present study contributes to the understanding and design of the tunnel ventilation system used in poultry houses.

Optimal Aerodynamic Shape Optimization of a Paraglider Airfoil Based on the Sharknose Concept

The effects of classical air inlet configurations on the aerodynamic performance of a paraglider airfoil are firstly presented. Followed by conducting gradient-based aerodynamic shape optimization of the baseline airfoil used in the investigation of the classical air inlets. Different air inlet configurations are introduced to the optimized profile, and there effects on the aerodynamic performance are then compared to the initial and optimized airfoils. The Reynolds averaged Navier-Stokes equations (RANS) are solved for the flow field around the closed and open airfoils. The canopy is assumed to be smooth, rigid and impermeable. Results are focused on both of lift and drag coefficients for performance analysis and on the internal pressure coefficient which can be critical for a real flexible wing regarding the risk of collapse.

Influence of the air inlet configuration on the performances of a paraglider open airfoil

A finite volume flow solver was used to solve the Reynolds averaged Navier-Stokes equations for the 2D flow field on a paraglider open airfoil. The canopy was assumed to be smooth, rigid and impermeable. The parametric study performed concerns the position and the width of the air inlet at the leading edge. The range of values used covers the air inlet geometries from classical ram-air parafoil to sport paraglider airfoil, including transition towards the full closed baseline airfoil. Results are focused both on lift and drag coefficients for performance analysis and on the internal pressure coefficient, which can be critical for a real flexible wing regarding the risk of collapse. Depending on the appearance of a separation bubble over the upper edge, two well separated behaviours can be observed. The first behaviour is more typical of ram-air parachutes and the second one corresponds to the design of performance paragliders. For paraglider configurations, it is shown that the aerodynamic coefficients of the open airfoil can be easily deduced from the pressure coefficients of the baseline airfoil without solving the internal flow.

Influence of the air inlet configuration on the performances of a paraglider open airfoil

A finite volume flow solver was used to solve the Reynolds averaged Navier-Stokes equations for the 2D flow field on a paraglider open airfoil. The canopy was assumed to be smooth, rigid and impermeable. The parametric study performed concerns the position and the width of the air inlet at the leading edge. The range of values used covers the air inlet geometries from classical ram-air parafoil to sport paraglider airfoil, including transition toward the full closed baseline airfoil. Results are focused both on lift and drag coefficients for performance analysis and on the internal pressure coefficient which can be critical for a real flexible wing regarding the risk of collapse. Depending on the appearance of a separation bubble over the upper edge, two well separated behaviours can be observed. The first behaviour is more typical of ram-air parachutes and the second one corresponds to the design of performance paragliders. For paraglider configurations, it is shown that the aerodynamic coefficients of the open airfoil can be easily deduced from the pressure coefficients of the baseline airfoil without solving the internal flow.

Fuel design in co-combustion of demolition wood chips and municipal sewage sludge

Municipal sewage sludge (MSS) is a waste stream resource which contains both energy and elements such as phosphorus which could be recycled. If these two aspects of this waste stream resource are to be used to their full potential the sludge should not be used in landfills or road construction. There is some use of sludge in agriculture today but not all MSS produced is suitable for direct use on arable land due to its content of potentially harmful elements, pathogens or anthropogenic chemicals. By combusting sludge that is not used directly in agriculture the problematic organic content could be destroyed. The combustion process also produces an ash that possibly could be used either directly in agriculture or as a raw material for recovering phosphorus and energy could be recovered. Building mono-combustion plants for sewage sludge is not economically feasible in all parts of the world so it is of interest to investigate how MSS can be introduced together with other fuels in existing infrastructure which already have extensive cleaning systems for potentially harmful elements.To investigate this possible path, demolition wood chips (DWC) were co-combusted with municipal sewage sludge (MSS) in a grate-fired combined heat and power plant running at 50% capacity producing 25MWth and 9MWel. The amount of MSS that was suitable to introduce in blends was determined using a “fuel fingerprint” based on the composition of the raw materials. Thermodynamic equilibrium calculations were made to evaluate potential problems with slagging based on the ash content prior to the combustion experiments. The fuels were introduced as a reference case with only demolition wood and pre-blended fuel mixtures in two ratios; 65w/w-% DWC/35w/w-% MSS and 55w/w-% DWC/45w/w-% MSS and were fired for 12h. The high water content of the MSS affected how much MSS that could be introduced without compromising the heat and power production.The fuel blends worked nicely for 12h of continuous combustion with small adjustments where the primarily the air inlet configuration was changed. The main problems encountered related to cleaning of the flue gases and to some extent ash removal. The bed ash and fly ash produced was analysed both using ICP-AES (elemental) and XRD (speciation) and the bottom ash was subjected to ash melting tests. The major nutrient phosphorus was mainly found in bottom ash (80w/w-%) as whitlockites with some hydroxyapatite whereas fly ash (20w/w-%) contained larger amounts of hydroxyapatite, especially for the reference fuel. The amount of alkali chloride in the fly ash was reduced in favour of alkali sulphate formation.

Effects of Air Inlet Configuration on Forced-Ventilation Enclosure Fires on a Naval Ship

The effects of air inlet configuration on pool fire behavior in a mechanically ventilated cabin were investigated. The closed cabin used was a model of a certain machinery cabin on a naval ship. Two air inlet configurations of one vent and two vents were taken into account together with five different elevations of air inlet. In one-vent cases, mass loss rate and gas temperature were lower and oxygen concentrations were higher than those of two-vent cases. With the increase of air inlet elevation, a sudden drop in average mass loss rate and peak temperature were found in the two-vent cases at the air inlet elevation of 1.56 m. In one-vent cases, a similar drop in average mass loss rate was found at the air inlet elevation of 0.88 m, while the peak temperature was almost unaffected by inlet elevation. According to temperature profiles and the characteristic parameter of the smoke layer stability, the formation of the smoke layer was destroyed by increasing the air inlet elevation or reducing the air inlets, and furthermore a more uniform distribution could be found. For the current cabin, the one-vent case with a lower air inlet elevation was recommended for smoke control, and the inlet should be set away from the essential equipment and the entrances of the cabin.

Heat Transfer Enhancement of Impinging Jet from Pulse Jet Combustor

The aims of this study are to investigate flow characteristics in pulse jet combustor and heat transfer characteristics of impinging jet from pulse jet combustor. The combustor is Helmholtz type which has single combustor chamber and single tailpipe. The inner diameter (D) of tailpipe was 47 mm and tailpipe length was about 16D. The effect of number of air inlets: single inlet, double inlets with 90o apart, double inlets with 180o apart and triple inlets with 90o apart on flow and heat transfer characteristics were studied. A water cooled heat flux sensor was applied to measure heat transfer rate on the surface at stagnation point. The jet-to-plate distance was varied at L=1D, 2D, 4D, 6D and 8D. Two of pressure transducers were mounted on the wall of combustion chamber and on the wall of tailpipe at 4D from tailpipe outlet to measure pressure simultaneously. It is found that the variation of pressure near the tailpipe outlet is strongly depended on air inlet configurations. The pressure variations in pulse jet combustor could be preliminary related to the temperature and velocity of jet from tailpipe and heat transfer rate on jet impingement surface.

Simplified thermo-fluid model of an engine cowling in a small airplane

Purpose – The purpose of this study is to developed a simplified thermo-fluid model of an engine cowling in a small airplane. An aircraft engine system is composed of different elements operating at various temperatures and in conjunction with the composite nacelle creates a region with high intensity of heat transfer to be covered by the cooling/ventilation systems. Therefore a thermal analysis, accounting for the complex heat transfer modes, is necessary in order to verify that an adequate cooling is ensured and that temperatures of the nacelle are maintained within the operating limits throughout the whole aircraft's flight. Design/methodology/approach – Simplified numerical simulations of conductive, convective and radiative heat transfer in the engine bay of the small airplane I-23 in a tractor arrangement were performed for different air inlet and outlet configurations and for varying conditions existing in air inlets during the flight. The model is based on the control volume approach for heat and ...

Experimental Investigation of a Novel Combustor Modelfor Gas Turbines

The present study describes the performance of a novel combustor model for gas turbines. The working principle of this combustor is based on the establishment of a large recirculation zone in the combustion chamber, where part of the inlet air is mixed with the combustion products. Efficient mixing is achieved by the use of high-velocity inlet air jets. Six different inlet air geometries have been analyzed under nonreacting and reacting conditions at atmospheric pressure. Laser-Doppler anemometry was employed to characterize the mean velocity and turbulent kinetic energy fields as a function of the air mass flow rate and geometry configuration. Measurements of mean gas species concentration (O 2 , CO 2 , CO, HC, and NO x ) at the model exhaust are reported as a function of the equivalence ratio for all configurations. The isothermal data revealed that the recirculation ratio is mainly a function of the geometry, with a minor dependence on the experimental conditions. Under reacting conditions, the data revealed that NO x emissions are low regardless of the combustor operating conditions and geometry. However, the air inlet configuration has a strong effect in combustor efficiency.

Experimental parametric study of forced and mixed convection in a passenger aircraft cabin mock-up

Forced and mixed convection has been investigated experimentally in a full scale passenger aircraft cabin mock-up. The mock-up represents a generic cabin section of the A380 upper deck. Large scale particle image velocimetry (PIV) and temperature field measurements were conducted in a cross sectional plane of the cabin mock-up. The flow fields for two different air inlet configurations were measured and analysed under isothermal and cooling conditions. Furthermore the flow rates at the different air inlet positions were varied while keeping the air exchange rate constant. Our extensive experimental parametric study demonstrates that the flow field in aircraft cabins is affected by various fluid mechanical phenomena. Interaction between the supplied air jets, negative buoyancy forces acting on these air jets and interaction of thermal plumes with the supplied air jets, all influence the flow field inside the cabin. The impact of these effects differs considerably depending on the ventilation configuration and relative mass flow settings at the supply inlets.

Mixing and flame holding with air inlet configuration in scramjet combustor

A parametric study of combustor inlet configuration for Supersonic Combustion Ramjet (SCRAMJET) Engine has been conducted by solving Two-Dimensional full Navier-Stokes equations. The main stream is air of Mach 5 entering through the configured inlet of the combustor and gaseous hydrogen is injected from the side wall at sonic condition. The parameters that include are the air inlet width and stream angle with a backward facing step under the inlet port. On the effect of inlet width variation, two competing phenomena have been observed: (i) in upstream of injector the strength of recirculation is higher for wider inlet and consequently the mixing increases and (ii) in downstream, the diffusion of hydrogen decreases with the increase of inlet width and eventually mixing decreases. As a result, in far downstream the mixing efficiency increases up to certain inlet width and then decreases for further increment of inlet width. During the variation of air stream angle, strong interaction between main and injecting flows can be observed for small angle causing sharp increase in mixing efficiency on the top of injector. Due to high momentum of air stream towards the side wall, no recirculation occurs at the upstream of injector for small angle and the system becomes unable for flame holding. Among the cases considered, the configuration of moderate air stream angle shows higher mixing efficiency and good flame holding capability.

Collection efficiency of particulate and xenon sampling in the international monitoring system of the comprehensive Nuclear-Test-Ban Treaty

Low-level monitoring of atmospheric radioactivity requires sampling with high collection efficiency for the aerosols and gases of interest. The radionuclide station network of the International Monitoring System designed to detect very low-levels of airborne radionuclides will consist of 80 particulate and 40 noble gas stations. This paper reports on studies performed to select suitable filter material and to characterise the sampling efficiency of air inlet configurations of high-volume particulate samplers. It also considers the collection characteristics of automatic xenon sampling systems.

Improving the use of mixing factors for dilution ventilation design.

In specifying dilution ventilation flow rate, a safety factor, K, is often used to provide a margin of safety and to compensate for uncertainties and health impact severity. In current practice, the selection of K is very subjective. Here the component of K accounting for imperfect mixing, Km, was studied to develop more effective and efficient design procedures. Air flow and contaminant distribution in a 10 m x 3 m x 7 m room with a single contaminant source on a 1-m high table were simulated for steady, isothermal conditions using computational fluid dynamics. A series of 10 simulations explored factorial combinations of air exchange rates (1, 2,4, 8, 16 ACH) and inlet types (a high wall jet and a ceiling diffuser). Nine additional simulations explored exhaust opening location effects and 13 other simulations investigated source location effects. Km was calculated at each of 25,600 grid locations within the room by linear regression of emission rate/flow rate (G/Q) on concentration (C). The linear relationship between C and G/Q at each of the points was nearly perfect (R2 > 0.97). For the simulations with varying dilution flow rate, Km ranged from 0.19 to 2.86 for the wall jet and from 0.94 to 4.34 for the ceiling diffuser. Holding G/Q at 100 ppm and varying source and exhaust location produced room average concentrations from 55.7 to 173 ppm. Unlike orthodox design approaches, this work suggests that air monitoring data often can be used to calculate dilution flow rate requirements. Also, dilution flow rate requirements may be reduced by enhancing room mixing with fans or altering air inlet configuration. However, mixing should not be increased if the altered room air currents could transport contaminant to an occupant's breathing zone or interfere with other control methods that depend on segregation of incoming air and contaminant.

Steady-State Waste Combustion and Air Flow Optimization in a Field Scale Rotary Kiln

This study describes a computational modeling study of a full-scale rotary kiln using the commercial CFD-code PHOENICS. A steady-state mode is assumed in which solid waste (a mixture of cellulose and toluene) is volatilized and burned. The focus of the model is on the gas phase fluid dynamics. Buoyancy is accounted for, turbulence is modeled with the κ-∈ model, radiative transfer is in a first step modeled with the composite flux model of radiation and combustion is modeled using the simple chemical reaction scheme (SCRS) model for diffusive, mixing limited reacting flows. The volatilization model makes use of a first-order Arrhenius-type reaction rate that takes the volatilization properties of both toluene and cellulose into account. The goal of this study is to screen various air inlet designs for their mixing characteristics and residence time distribution. This is translated in the destruction efficiency of selected compounds. The actual air inlet configuration in an existing full-scale incinerator is chosen as a reference for comparison. Alternative designs are analysed. The methodology and usefulness of the approach is fully demonstrated and typical design results are reported. Key words: Rotary kiln; Computational Fluid Dynamics; solid waste volatilization; air inlet design