Tarek Abdel-Salam

Does the Lack of Hands-On Experience in a Remotely Delivered Laboratory Course Affect Student Learning?.

Educators question whether performing a laboratory experiment as an observer (non-hands-on), such as conducted in a distance education context, can be as effective a learning tool as personally performing the experiment in a laboratory environment. The present paper investigates this issue by comparing the performance of distance education students with their on-campus counterparts in a junior-level fluid mechanics laboratory course over a three semester period. Using digital recording methods, the on-campus versions of the laboratory experiments were formatted to accommodate distance-education students who did not have access to campus facilities. This paper compares the assessment of student performance in demonstrating both learning of technical concepts and the ability to describe these in an effective written laboratory report.

A case study: do high school GPA/SAT scores predict the performance of freshmen engineering students?

The current study examines the performance of freshman students in a new engineering program at East Carolina University and compares it to their performance at high school. ECUs engineering program started in Fall 2004 and it differs from many other engineering programs in three primary ways: (1) it emphasizes the application of engineering theory to the real world by engaging freshman students in hands-on engineering activities, (2) the mathematics and science content are integrated with the engineering courses, and (3) the students are working very closely with the engineering faculty and their mates in a team-based learning process (cohort system). The performance of the students in the engineering program is evaluated based on the details of their grades in engineering, and general education courses. Meanwhile, their GPA and Scholastic Aptitude Test (SAT) scores is used to evaluate their performance in high school

A Comprehensive Fuel Spray Model for High Pressure Fuel Injectors

Understanding the physics and chemistry involved in spray combustion, with its transient effects and the inhomogeneity of the spray is quite challenging. For efficient operation of both internal combustion and gas turbine engines, great insight into the physics of the problem can be obtained when a computational analysis is used in conjunction with either an experimental program or through published experimental data. The main area to be investigated to obtain good combustion begins with the fuel injection process and an accurate description of the mean diameter of the fuel particle, injection pressure, drag coefficient, rate shaping etc must be defined correctly. This work presents a methodology to perform the task set out in the previous paragraph and uses experimental data obtained from available literature to construct a semi-empirical numerical model for high pressure fuel injectors. A modified version of a multidimensional computer code called KIVA3V was used for the computations, with improved sub-models for mean droplet diameter, injection pressure, injection velocity, and drop distortion and drag. The results achieved show good agreement with the published in-cylinder experimental data for a Volkswagen 1.9 L turbo-charged direct injection internal combustion engine under actual operating conditions. It is crucial to model the spray distribution accurately, as the combustion process and the resulting temperature distribution and pollutant emission formation is intimately tied to the in-cylinder fuel distribution. The present scheme has achieved excellent agreement with published experimental data and will make an important contribution to the numerical simulation of the combustion process and pollutant emission formation in compression ignition direct injection engines and gas turbine engines.© 2008 ASME

Are Distance Laboratories Effective Tools for Technology Education

The ability to perform a laboratory experiment as a nonhands-on observer, such as in a distance education context, has been questioned by some educators who ponder whether distance education lab courses are as effective as those held in a physical laboratory environment. This article examines this issue and compares the performance of distance education students with their on-campus counterparts in a junior laboratory course. Data from six semesters are examined and presented. A regression model is developed to predict the performance of both distance education and on-campus students. Results of the model show that only report grades and location (whether distance education or on-campus) are statistically significant. In addition, statistical analysis of the six semesters of data shows equal performance of the two groups.

Hydrogen, Biodiesel and Ethanol for Internal Combustion Engines: A Review Paper

Alternative fuels research has been on going for well over many years at a number of institutions. Driven by oil price and consumption, engine emissions and climate change, along with the lack of sustainable fossil fuels, transportation sector has generated an interest in alternative, renewable sources of fuel for internal combustion engines. The focus has ranged from feed stock optimization to engine-out emissions, performance and durability. Biofuels for transportation sector, including alcohols (ethanol, methanol…etc.), biodiesel, and other liquid and gaseous fuels such as methane and hydrogen, have the potential to displace a considerable amount of petroleum-based fuels around the world. First generation biofuels are produced from sugars, starches, or vegetable oils. On the contrary, the second generation biofuels are produced from cellulosic materials, agricultural wastes, switch grasses and algae rather than sugar and starch. By not using food crops, second generation biofuel production is much more sustainable and has a lower impact on food production. Also known as advanced biofuels, the second-generation biofuels are still in the development stage. Combining higher energy yields, lower requirements for fertilizer and land, and the absence of competition with food, second generation biofuels, when available at prices equivalent to petroleum derived products, offer a truly sustainable alternative for transportation fuels. There are main four issues related to alternative fuels: production, transportation, storage, handling and usage. This paper presents a review of recent literature related to the alternative fuels usage and the impact of these fuels on fuel injection systems, and fuel atomization and sprays for both spark-ignition and compression-ignition engines. Effect of these renewable fuels on both internal flow and external flow characteristics of the fuel injector will be presented.Copyright

A three-dimensional computational study of the effect of the inlet conditions on supersonic mixing and combustion

In recent years, a significant amount of high-speed combustion research has been directed toward optimization of scramjet combustors, and in particular on the efficiency of fuel–air mixing and reaction taking place in the engine. This article numerically investigates the flow characteristics of a dual-mode scramjet–combustor configuration. Results are presented for a three-dimensional combustor model with a single wall-mounted raised (compression) ramp as a fuel injector. Hydrogen is used as the fuel and is injected through the raised ramp (which has an aspect ratio of 0.5) parallel to the air stream. Vitiated air with different concentrations of H2O and CO2 are used at the inlet boundary. Three equivalence ratios were simulated, 0.25, 0.31, and 0.41. Numerical results are obtained using a finite volume computational fluid dynamics code. Initially, three forms of the two-equation k–ε turbulent model were tested: the standard, the RNG, and the realizable with unstructured grids. Final results were obtained with the RNG form of the k–ε turbulent model. Results show that the combustion efficiency decreases with the increase of the equivalence ratio. Also, the cases with CO2 show slightly higher combustion efficiencies.

Computational Study of Flow and Mixing Characteristics of Turbulent Opposed Jets

The turbulent mixing of jet flows is one of the important problems of turbulent shear flow due to its application in combustion process involving fuel-oxidizer combinations such as hydrogen-air and methane-air. Fluid dynamics of opposed jets is not completely clarified as there are questions unanswered about flow stability and structure. In the present work, three-dimensional numerical simulations were conducted to study flow and mixing characteristics of turbulent opposed-jets. The numerical simulations were carried out with a finite volume CFD code. Turbulence is treated with the two equation model, the k-e model. Nozzle diameter (d) and nozzle separation (W) are kept constant and equals to 32mm. Also, different jet velocities (Uj) have been examined corresponding to Reynolds numbers of 4500 to 12,000. Both confined and unconfined cases were simulated.Copyright

Mixing Characteristics of a Two-Phase Flow (Gas-Liquid) Microchannel Mixer

Multiphase phase flows occur in many engineering and bio-medical applications. Bubble formation in microchannels can be beneficial or harmful depending upon their influence on the operation and performance of microfludic devices. Potential uses of bubble generation found in many applications such as microreactors, micropump, and micromixers. In the present work the flow and mixing process in a passive microchannel mixer were numerically investigated. Effects of velocity, and inlet width ratio (Dgas /Dliquid ) on the two phase flow were studied. Numerical results are obtained for 2-dimensional and 3-dimesional cases with a finite volume CFD code and using structured grids. Different liquid-gas Reynolds number ratios (Reliquid /Regas ) were used ranging from 4 to 42. In addition, three values of the inlet width ratio (Dgas /Dliquid ) were used. Results for the 3-D cases capture the actual shape of the air bubble with the thin film between the bubble and the walls. Also, increasing Reliquid increases the rate of the development of the air bubble. The bubble length increases with the increase of Dgas /Dliquid . For the same values of Re, the rate of growth of the bubble increases with the increase of Dgas /Dliquid . Finally, a correlation is provided to predict the length of the bubble with liquid-gas Reynolds number ratio (Reliquid /Regas ) and tube width.Copyright

Numerical Study of Flow and Heat Transfer Characteristics of Impinging Jets

This study presents results for flow and heat transfer characteristics of two-dimensional rectangular impinging jets and three-dimensional circular impinging jets. Flow geometries under consideration are single and multiple impinging jets issued from a plane wall. Both confined and unconfined configurations are simulated. Effects of Reynolds number and the distance between the jets are investigated. Results are obtained with a finite volume computational fluid dynamics (CFD) code. Structured grids are used in all cases of the present study. Turbulence is treated with a two equation k-e model. Different jet velocities have been examined corresponding to Reynolds numbers of 5,000 to 20,000. Results of the three-dimensional cases show that Reynolds number has no effect on the velocity distribution of the center jet. Results of both two-dimensional and three-dimensional cases show that Reynolds number highly affects the heat transfer and values of the Nusselt number. The maximum Nusselt number was always found at the stagnation point of the center jet.© 2010 ASME

Two-Dimensional Numerical Study of Two-Phase Flow (Gas-Liquid) in a Microchannel Mixer

Microfluidic systems are important in a variety of applications such as DNA sequencing, cell separation, environmental monitoring, heat transportation in spacecraft and space station [1–2]. Micromixers are the most important component in microfluidic systems and they can be classified as active and passive micromixers [3]. In micro dimensions, surface forces dominate over body forces requiring special attention for problems involving two-phase flows with free surfaces which are often driven by capillary forces [4]. In the present work the flow and mixing process in a passive microchannel mixer were numerically investigated. Effects of velocity, surface tension, and contact angle on the two phase flow were studied. Numerical results are obtained with a finite volume CFD code and using structured grids. Different liquids-gas Reynolds number ratios (Reliquid /Regas ) were used ranging from 4 to 42. In addition, five values of the contact-angle (0 – 120) and seven values of the liquid surface tension (0.02 – 0.1) were used. Results show that increasing Reliquid increases the rate of the development of the air bubble. Increased surface tension resulted in increased bubble length. Bubble length decreased with increased contact angle till 75 degrees and further increase resulted in increased bubble length.Copyright