Jamal Naser

Some of the major concerns regarding sewer overflows to receiving water bodies include serious environmental, aesthetic and public health problems. A noble self-cleansing sewer overflow screening device having a sewer overflow chamber, a rectangular tank and a slotted ogee weir to capture the gross pollutants has been investigated. Computational Fluid Dynamics (CFD) techniques are used to simulate the flow phenomena with two different inlet orientations; parallel and perpendicular to the weir direction. CFD simulation results are compared with analytical results. Numerical results show that the flow is not uniform (across the width of the inclined surface) near the top of the inclined surface. The flow becomes uniform near the bottom of the inclined surface, with significant increase of shear stress. The simulation results promises for an effective and efficient self-cleansing sewer overflow screening device by comparing hydrodynamic results. Keywords—Hydrodynamic Characteristics, O...

Abstract A comprehensive 3D numerical investigation of the behaviour of particles flowing through a horizontal pipe has been studied in this paper. The multiphase mixture module available in the computational fluid dynamics (CFD) model FLUENT 6.2 is used in this study. Five different time-dependent flows and particle-load profiles have been used to simulate particle flow behaviour though the pipeline. The deposition of particles along the pipe has been investigated. The effect of unsteady fluid velocity over particle loads has also been investigated. Results show that after a certain length of pipe and/or travel time, when the velocity becomes steady after a deceleration period, the pipe shear stress is strong enough to cause some particle deposition or rolling along the bottom surface of the pipe wall, creating a secondary accumulation of particles (called shoot). Various velocity and particle load profiles have been considered in the light of real phenomena occurring in Melbourne’s South East Water Ltd distribution network. The paper is expected to help the water authorities in understanding the propagation of turbidity spikes in pipe networks.

In recent years, significant progress has been achieved in the study of aqueous foams. Having said this, a better understanding of foam physics requires a deeper and profound study of foam elements. This paper reviews the studies in the microscale of aqueous foams. The elements of aqueous foams are interior Plateau borders, exterior Plateau borders, nodes, and films. Furthermore, these elements' contribution to the drainage of foam and hydraulic resistance are studied. The Marangoni phenomena that can happen in aqueous foams are listed as Marangoni recirculation in the transition region, Marangoni-driven flow from Plateau border towards the film in the foam fractionation process, and Marangoni flow caused by exposure of foam containing photosurfactants under UV. Then, the flow analysis of combined elements of foam such as PB-film along with Marangoni flow and PB-node are studied. Next, we contrast the behavior of foams in different conditions. These various conditions can be per...

The pedagogy of engineering requires a better understanding of the requirements of students' abilities to learning the skills necessary for working in the engineering community. In many engineering courses around the world, one of the key aspects required of the students is that they complete an independent project in their final year of studies incorporating information retrieval and subsequent communication skills. The current work provides details teaching and learning approaches to enhance student abilities and expertise involving research skills, communication skills, and information retrieval integrated within capstone projects. Findings from this the work indicated that both domestic and international students benefited from the intensive tutorial activities involving computer based information retrieval skills. The implementation of active tutorial sessions resulted in increased grades for the majority of students, highlighting the importance of intensive active learning...

Abstract The cutting performance of an abrasive water jet mainly depends on the abrasive particle’s velocities and impact angles as well as the physical properties of the particles and the workpiece being cut. This ultimately causes the different modes of erosion process at the time of cutting of the job specimen. During the cutting process the cutting profile changes with the depth of the cut to form the kerf. Due to the change of radius of curvature of the cutting surface with depth, the erosion process per unit depth decreases because of the changing of the impact angle. Here comprehensive numerical studies have been carried out to find the particle impact characteristics on the groove wall (cutting surface) as well as side walls for different radii of curvature. The results obtained from the simulations have indicated that the particle impact angles depend on the radius of curvature. The study has shown that the particles have a tendency to slide or stay close to the cutting surface for the large radius of curvature and have very small impact angles. The particles’ primary impact velocity are decreased little, however, the particle’s impact velocities are significantly decreased for the secondary, tertiary and following impacts due to fluid drag. The numerical simulation results have been used to calculate the particle’s distribution factor for both deformation wear and cutting wear. The distribution factors indicate that the particles have tendency to slide on the groove wall for higher radius of curvature. These findings are consistent with the literature.

Abstract Co-firing biomass is the principal means of mitigating the future energy crisis by expanding the use of renewable energy. Oxy-fuel combustion is the most capable technologies for carbon capture and storage (CCS) system. This paper presents a 3D numerical study considering co-firing concepts in a 550 MW tangentially fired furnace using a commercial CFD code AVL Fire ver.2009.2. Necessary subroutines were written and coupled with the code to account for chemical reactions, heat transfer, fluid and particle flow fields and turbulence. Due to irregularities of the biomass particle shape, a special drag effect was considered. Three different co-firing cases (20% biomass with 80% coal, 40% biomass with 60% coal and 60% biomass with 40% coal) were considered. All the co-firing cases were simulated under air-firing and three different oxy-firing cases (25% O 2 /75% CO 2 , 27% O 2 /73% CO 2 and 29% O 2 /71% CO 2 ). Level of confidence has been achieved by conducting a study on co-firing of biomass with coal in a 0.5 MW small scale furnace under air and oxy-fuel conditions. Similar findings have been observed in the present study which indicates the model can be used to aid in design and optimization of large-scale biomass co-firing under oxy-fuel conditions. This study enables the calculation of species transport and mixing phenomena and the simulation of ignition, combustion and emission formation in industrial furnace. Results were presented by the aerodynamics of burner flow, temperature distributions, gaseous emissions such as O 2 and CO 2 distributions. With the increase of biomass sharing, peak flame temperature reduced significantly. The dominant effect of the lower calorific value of biomass dampens the effect of volatile content contributing to lower temperature. Comparatively, improved burnout is observed for the improved oxy-fuel cases. But, the CFD model predicted a significant increase in unburned carbon in fly ash for the increase of biomass co-firing sharing. Overall, this study highlights the possible impact of changing the fuel ratio and combustion atmosphere on the boiler performance, underlining that minor redesign may be necessary when converting to biomass co-firing under air and oxy-fuel conditions.

Inefficient process in the thermal power station leads to greenhouse gas emission. Reductions in emissions are largely dependent on the improvement of efficiency, with lower fuel consumption as a 1% improvement in power station efficiency delivering an almost 3% reduction in CO2 emissions. Maximum CO2 reduction is also possible through the use of alternative fuels and CO2 capture. Therefore, there is a need for energy-efficient technology to improve power plants that are able to utilize alternative fuels and CO2 capture. Coal is a major source of fuel, while biomass fuels, such as energy crops, waste wood, and agricultural residues are supplementary. The design, operation, and maintenance of combustion equipment require detailed understanding of the combustion process inside the furnace. In order to explore the major challenges, experimental methods are important but often inadequate to analyze the detailed phenomena inside the boiler, especially for industrial furnaces. A computational technique provides the opportunity to investigate in detail, the combustion phenomena and contaminant development inside the furnace. In order to understand combustion-related issues and problems for direct firing or packed bed combustion, modeling and analysis are required. This chapter will briefly report the recent advances in the combustion technologies, different carbon capturing and storage systems, modeling methodology for coal combustion, biomass co-combustion, packed bed combustion, and slag formation modeling. Also, examples of coal/biomass combustion will be illustrated to investigate, in detail, the combustion phenomena and related issues in the furnace.

Abrasive water jet uses for precision cutting in modern technology. A Computational Fluid Dynamics (CFD) method has been developed to find out the particle, water and air velocity distributions for abrasive water jet. The study has been carried out using a multi-...

ABSTRACT A computational fluid dynamics (CFD) model of the pyrolysis of a Loy Yang low-rank coal in a pressurised drop tube furnace (pdtf) was undertaken evaluating Arrhenius reaction rate constants. The paper also presents predictions of an isothermal flow through the drop tube furnace. In this study, a pdtf reactor operated at pressures up to 15 bar and at a temperature of 1,173 K with particle heating rates of approximately 105 K s−1 was used. The CFD model consists of two geometrical sections; flow straightner and injector. The single reaction and two competing reaction models were employed for this numerical investigation of the pyrolysis process. The results are validated against the available experimental data in terms of velocity profiles for the drop tube furnace and the particle mass loss versus particle residence times. The isothermal flow results showed reasonable agreement with the available experimental data at different locations from the injector tip. The predicted results of both the single reaction and competing reaction modes showed slightly different results. In addition, several reaction rate constants were tested and validated against the available experimental data. The most accurate results were being Badzioch and Hawksley (Ind Eng Chem Process Des Dev 9:521–530, 1970) with a single reaction model and Ubhayakar et al. (Symp (Int) Combust 16:427–436, 1977) for two competing reactions. These numerical results can provide useful information towards future modelling of the behaviour of Loy Yang coal in a full scale tangentially-fired furnace.

ABSTRACT In the present paper, a three-dimensional numerical investigation of pulverized dry lignite was undertaken, integrating the combustion of four different scenarios adopted experimentally in a 100-kW Chalmers laboratory-scale furnace. A hybrid unstructured grid computational fluid dynamics (CFD) code was used to model and analyze: an air-fired, oxy-fuel OF25 (25 vol % O2 concentration), oxy-fuel OF27 (27 vol % O2 concentration), and oxy-fuel OF29 (29 vol % O2 concentration). The appropriate mathematical models with the related kinetics parameters were implemented to calculate the temperature distributions, species concentrations (O2, CO2, CO, H2O, and H2), NOx emission concentrations, and the radiation heat transfer. The multistep chemical reaction mechanisms were conducted on the gas phase and solid phase of coal reaction in one-, two-, and three-step reaction schemes. The predicted results showed reasonably good agreement against the measured data for all combustion cases; however, in the three-step scheme, the results were highly improved, particularly in the flame envelope zone. For the NOx calculations, the obvious differences between the air-fired and oxy-fuel (OF27 and OF29) cases were evident. In the OF27 and OF29 cases, the expected increase in the flame temperatures and CO2 and H2O concentrations led to a slight increase in the radiative heat fluxes on the furnace wall, with respect to the air-fired case. As a continuation of improvement to the oxy-fuel combustion model, this numerical investigation might probably provide important information toward future modeling of a 550-MW, large-scale, brown coal oxyfuel tangentially fired furnace

Numerical solution based on the control volume method is presented for the study of heat transfer for forced convective flow in a channel filled with a fluid saturated porous media. The solution of the conservative differential equations governing the flow is performed using ...

Numerical solution based on the control volume method is presented for the study of heat transfer for forced convective flow in a channel filled with a fluid saturated porous media. The solution of the conservative differential equations governing the flow is performed using ...

ABSTRACT A computational fluid dynamics (CFD) model of the pyrolysis of a Loy Yang low-rank coal in a pressurised drop tube furnace (pdtf) was undertaken evaluating Arrhenius reaction rate constants. The paper also presents predictions of an isothermal flow through the drop tube furnace. In this study, a pdtf reactor operated at pressures up to 15 bar and at a temperature of 1,173 K with particle heating rates of approximately 105 K s−1 was used. The CFD model consists of two geometrical sections; flow straightner and injector. The single reaction and two competing reaction models were employed for this numerical investigation of the pyrolysis process. The results are validated against the available experimental data in terms of velocity profiles for the drop tube furnace and the particle mass loss versus particle residence times. The isothermal flow results showed reasonable agreement with the available experimental data at different locations from the injector tip. The predicted results of both the single reaction and competing reaction modes showed slightly different results. In addition, several reaction rate constants were tested and validated against the available experimental data. The most accurate results were being Badzioch and Hawksley (Ind Eng Chem Process Des Dev 9:521–530, 1970) with a single reaction model and Ubhayakar et al. (Symp (Int) Combust 16:427–436, 1977) for two competing reactions. These numerical results can provide useful information towards future modelling of the behaviour of Loy Yang coal in a full scale tangentially-fired furnace.

ABSTRACT In the present paper, a three-dimensional numerical investigation of pulverized dry lignite was undertaken, integrating the combustion of four different scenarios adopted experimentally in a 100-kW Chalmers laboratory-scale furnace. A hybrid unstructured grid computational fluid dynamics (CFD) code was used to model and analyze: an air-fired, oxy-fuel OF25 (25 vol % O2 concentration), oxy-fuel OF27 (27 vol % O2 concentration), and oxy-fuel OF29 (29 vol % O2 concentration). The appropriate mathematical models with the related kinetics parameters were implemented to calculate the temperature distributions, species concentrations (O2, CO2, CO, H2O, and H2), NOx emission concentrations, and the radiation heat transfer. The multistep chemical reaction mechanisms were conducted on the gas phase and solid phase of coal reaction in one-, two-, and three-step reaction schemes. The predicted results showed reasonably good agreement against the measured data for all combustion cases; however, in the three-step scheme, the results were highly improved, particularly in the flame envelope zone. For the NOx calculations, the obvious differences between the air-fired and oxy-fuel (OF27 and OF29) cases were evident. In the OF27 and OF29 cases, the expected increase in the flame temperatures and CO2 and H2O concentrations led to a slight increase in the radiative heat fluxes on the furnace wall, with respect to the air-fired case. As a continuation of improvement to the oxy-fuel combustion model, this numerical investigation might probably provide important information toward future modeling of a 550-MW, large-scale, brown coal oxyfuel tangentially fired furnace