Bassem H. Ramadan

Development of Problem-Based Learning Modules for Engineering Thermodynamics

Problem-Based Learning (PBL) is an instructional approach that fosters active learning, supports knowledge construction, integrates disciplines, and naturally combines classroom learning with real-life applications. This approach can be described as student-centered and concept-embedded. This paper presents the development of curricular materials in Engineering Thermodynamics that are founded on PBL, supported by technology through simulations, and target higher levels of Bloom’s Taxonomy of Learning. Thermodynamics is restructured as modules presenting practical applications first whereas principles are introduced just-in-time and as encountered. Theoretical information is presented to support the understanding of knowledge as students apply inquiry-based learning. These modules are carefully designed to reflect traditional concepts but made more exciting as students discover the need for the laws and principles. The classroom format is interactive, cooperative and revolves around students’ needs. Formative and summative assessment tools are designed to examine the effectiveness of created modules.Copyright

The Effect of Piston Bowl and Spray Configuration on Diesel Combustion and Emissions

A numerical and experimental study of the effect of piston bowl and spray configuration on diesel combustion and emissions has been conducted. The objective of this study is to gain better understanding of the effect of the piston bowl shape and fuel injector configuration on fuel-air mixing, combustion, and emissions in a diesel engine. Ideally, a uniform fuel-air mixture in the cylinder is desired to prevent the formation of regions containing a rich mixture, where soot is usually formed, and regions of lean mixtures, where nitrogen oxides are formed. Different piston bowl shapes and fuel injectors (number of nozzles, spray angle) have been considered and simulated using computational fluid dynamics and experiments. CFD calculations of fuel mass fraction, and measurements of cylinder pressure and emissions species are included. The results show that computer simulations coupled with experiments provide insight into the interactions between fluid flow, fuel-air mixing, combustion, and emissions.Copyright

Effect of Damkohler Number and Non-Unity Lewis Number on a Laminar Diffusion Flame

The effect of the Damkohler number (Da ) and non-unity Lewis number on a two-dimensional, steady, laminar diffusion flame anchored by a dividing plate in a rectangular channel was considered. The governing equations were solved numerically, using the SIMPLE and ADI schemes. The results for non-unity Lewis number were compared with those for a unity Lewis number, and Da a was also varied in order to determine their effect on the flame structure. The results show that an increase in the Da causes the flame to exist closer to the trailing edge of the divider and to increase the reactivity. A non-unity Lewis number creates a non-symmetrical flame by forcing the flame to exist on the fuel side.Copyright

Numerical Study to Achieve Stratified EGR in Engines

Exhaust Gas Re-circulation (EGR) has been used in intemal combustion engines to control automotive emissions. EGR is usually used to dilute the inlet charge, which consists of air, by redirecting part of the exhaust into the inlet manifold of the engine. This results in a reduction of the oxygen mass fraction in the inlet charge. However, dilution of the air-fuel mixture in an engine using stratified EGR could offer significant fuel economy saving comparable to lean burn or stratified charge direct-injection SI engines. The most critical challenge is to keep the EGR and air-fuel mixture separated, or to minimize the mixing between the two zones to an acceptable level for stable and complete combustion. Swirl-type stratified EGR and fuel-air flow structure is considered desirable for this purpose, because the circular shape of the cylinder tends to preserve the swirl motion. Moreover, the axial piston motion has minimal effect on the swirling motion of the fluid in the cylinder. In this study, we consider intake system design in order to generate a two-zone combustion system, where EGR is maintained in a layer on the periphery of the cylinder, and the fuel-air mixture is maintained in the center of the cylinder. KIVA-3V was used to perform numerical simulations on different EGR systems. The simulations were performed to determine if the two-zones can be generated in the cylinder, and to what extent mixing between the two zones occurs. For the engine geometries considered in this study, the results showed that it is possible to generate the two zones, but mixing is difficult to control.Copyright

A Numerical Study on Combustion and Emissions in a Dual Fuel Directly Injected Engine Using Biogas and Diesel

A numerical study on the use of biogas and diesel in a dual-fueled directly-injected engine has been conducted. The objective of this study is to determine the effect of using biogas on engine performance, combustion, and emissions. The main fuel is biogas which is premixed with air in order to form a homogeneous mixture. The mixture is then compressed and ignited by injecting diesel fuel before TDC. The pilot fuel is expected to lead to multiple ignition points in the cylinder in order to achieve uniform combustion in the cylinder. The expected benefits are lower nitrogen oxides and soot compared to pure diesel combustion. Numerical simulations using CFD software were used to simulate fuel-air mixture, compression, fuel injection, combustion, and emissions. Different quantities of biogas and diesel were investigated to determine the optimum mixture ratio. Since biogas, which is natural gas produced from human waste, contains large quantities of carbon dioxide, the effect of carbon dioxide content in the fuel was investigated. The results of this study agree very well with results from other studies found in the literature.© 2014 ASME

A Three-Dimensional Transient Numerical Study of a Close-Coupled Catalytic Converter Internal Flow

This study involves a numerical and experimental investigation of fluid flow in automotive catalytic converters. The numerical work involves using computational fluid dynamics (CFD) to perform three-dimensional calculations of turbulent flow in an inlet pipe, inlet cone, catalyst substrate (porous medium), outlet cone, and outlet pipe. The experimental work includes using hot-wire anemometry to measure the velocity profile at the outlet of the catalyst substrate, and pressure drop measurements across the system. Very often, the designer may have to resort to offset inlet and outlet cones, or angled inlet pipes due to space limitations. Hence, it is very difficult to achieve a good flow distribution at the inlet cross section of the catalyst substrate. Therefore, it is important to study the effect of the geometry of the catalytic converter on flow uniformity in the substrate. The analysis involved determining back pressure (BP) across the converter system for different monolith cell densities, mass flow rates, converter aspect ratio, inlet cone angle, and inlet pipe offset. The numerical results were used to study the velocity profile at the inlet to the substrate, and were verified with experimental measurements of velocity and BP.Copyright

Numerical Prediction of Fluid Flow and Diesel Combustion in a Pre-Chamber and Main Chamber

In this study computational fluid dynamics (CFD) was used to model fluid flow and diesel combustion in an IC engine that uses a pre-chamber and a main-chamber. The pre-chamber is located in the cylinder head and a bowl in the piston serves as the main chamber. The study considers the effect of diesel combustion in the pre-chamber on turbulence generation and hence fuel-air mixing and combustion in the piston-bowl. Diesel fuel was injected directly into the pre-chamber and the piston bowl at different times. In order to better determine the effect of pre-chamber combustion on the main chamber combustion, various pre-chamber injection timings were considered. The results show that pre-chamber combustion caused the average cylinder pressure to increase by up to 20% in some cases.Copyright