The leading edge of turbine blades is one of the critical areas that need to be cooled effectively because of the high local heat transfer rate of the main flow. Film cooling with different shaped holes as well as internal cooling by impinging jets has successfully been applied in modern gas turbine applications. This paper numerically studies the cooling of the leading edge with a row of dual impinging jets — two jets close to each other. Heat transfer of the dual jets is compared to that of a single jet (in a row) based on the same flow rate or jet velocity. The effect of the distance between the dual jets and the jet inclination angle is examined to seek the best geometric parameters. In addition, the curvature of the leading edge surface is considered to examine the heat transfer difference between curved and flat walls. Various jet-to-target spacing and Reynolds numbers are also studied. Results show that the dual impinging jets generally produce two high heat transfer regions in the stagnation point, and the peak value is slightly higher than the single row of jets with the same Reynolds number. When the distance between two jets is 3d, the jet flow after bouncing back from the symmetry line affects the heat transfer as a crossflow. The target surface curvature has little effect on the overall heat transfer, but the peak heat transfer coefficient is lower on the curved surface than that on the flat surface. The dual impinging jets present a higher average heat transfer around the stagnation region.

She received her Ph. D. in Mechanical Engineering from the University of Maryland at Baltimore County (UMBC), Baltimore, Maryland, in May 2003. Her research interests include mechanical applications in microelectronics, biomechanics, system dynamics, and system optimizations, etc.

In this paper, the block diagram based SIMULINK models were developed to evaluate the dynamic response of a portable electronic product with various impact configurations. The visual interfaces of the developed models present results in a way that people can immediately identify the effects of changing system parameters. It was found that time durations of the input profiles play an important role in the dynamic response. The system response can be designed by carefully choosing the impact time. Certain input pulse time results in the response with very low ringing after first or second peaks. IntroductionDynamic performance during drop impact is a great concern to semiconductor and electronic product manufacturers, especially for portable devices such as mobile phones. Recently more attention and effort have been devoted toward upon mechanical modelling of microelectronic packages under drop impact loads [1][2][3][4][5][6][7][8].In this paper, the block diagram based SIMULINK analysis was introduced to determine the dynamic response of the portable electronic systems with various impact configurations. SIMULINK is an interactive, block-diagram-based tool for modelling and analyzing dynamic systems, and it is tightly coupled with MATLAB and supported by blocksets and extensions. Using such a tool, the relationship between input and output can be obtained and visualized easily and quickly with selected system parameters. As an example, a board level predictive dynamic model was established and the SIMULINK models were developed and used in building block diagrams, performing simulations, as well as analyzing results. The visual interface of the developed models present results in a way that one can immediately identify the effects of changing system parameters.In the section which follows, a simplified 2 DOF

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With an estimated three billion man-hours of use each year, improvements to the mechanical efficiency of lawnmower systems may yield significant reductions in emissions. Modifications to either the blade geometry or material have been considered in order to achieve the desired gains in efficiency. Specifically, focus is placed upon identification of a more efficient edge shape, reduction of required power input to the blade, and extending the life of the blade sharpness. Using software packages such as Parametric Technology Corporation’s (PTC’s) Pro/Engineer the students were able to increase the quality of design via finite element analysis (FEA) programs such as MSC. Nastran or PTC’s Mechanica. AISI 440C stainless steel was selected as a possible candidate based upon several appealing properties such as high strength, hardness, and resistance to corrosion. It does however have a lower fracture toughness and therefore presents a higher susceptibility to brittle fracture. When both the traditional stress analysis and fracture analysis were considered, opposing results were found. Due to this, other criteria such as cost of material, machining costs, and carbon footprint were considered before making a final design decision. Enhancing education in engineering by diversifying design criteria and encouraging students to address contemporary, real-world design problems was a primary goal of this project. The traditional mechanical design approach relies on stress-strain analysis in order to predict potential failure scenarios, and is the primary technique presented in most undergraduate engineering curricula. Despite its significance, the fracture mechanics approach is not often presented in great detail at the undergraduate level. The academic benefits of including these more universal considerations in the undergraduate engineering curriculum are illustrated in this paper.