Selin Arslan

Fostering the entrepreneurial mindset in the junior and senior mechanical engineering curriculum with a multi-course problem-based learning experience

This paper presents a multi-course problem-based learning (PBL) experience to foster the entrepreneurial mindset in the junior and senior mechanical engineering curriculum. Previous senior project students designed, fabricated, and validated a fluid-powered gantry crane that exhibited areas for improvement. To improve upon the project gantry crane, junior-and senior-level students implemented concurrent problem-based learning activities in three courses: Fluid Mechanics, Heat Transfer, and Mechatronics. Even though the PBLs targeted both technical and entrepreneurial objectives, only the results of entrepreneurial mindset attributes are discussed in this paper. Assessment results including student commentary are detailed and discussed in the paper. Preliminary results indicate extensive student practice of entrepreneurial skills.

Using a Funded Capstone Project to Teach Fluid Power and Advanced Mechanical Design

The A. Leon Linton Department of Mechanical Engineering at Lawrence Technological University offered a new senior capstone project to a small group of students, funded by a teaching grant from the National Fluid Power Association. All mechanical engineering students at Lawrence Tech must complete a capstone project: either an SAE competition team or a project addressing a particular industry need. The team that worked on the current project consisted of students with various concentrations in mechanical engineering and included an international visiting student from Brazil. Three faculty in Mechanical Engineering, each with different areas of expertise: thermodynamics, heat transfer, fluid mechanics and mechatronics, mentored and worked closely with the students at every step of this project. The objective of this project was to design and fabricate a classroom-scale gantry crane for material handling. The undergraduate students were not only involved in the design of a fluid powered system, but also worked on the modeling of mechanical components and the mechanical system as well as circuit design for an operator interface. The self-guided and real-world design aspect of the project increases the effectiveness of teaching by the faculty and retention of the subject by the students involved in the project.Copyright

Multi-Objective Optimization of a Simplified Car Body Using Computational Fluid Dynamics

Today’s strict fuel economy requirement produces the need for the cars to have really optimized shapes among other characteristics as optimized cooling packages, reduced weight, to name a few. With the advances in automotive technology, tight global oil resources, lightweight automotive design process becomes a problem deserving important consideration. It is not however always clear how to modify the shape of the exterior of a car in order to minimize its aerodynamic resistance. Air motion is complex and operates differently at different weather conditions. This gap can be covered by the use of adjoint solvers which predict the sensibility of the aerodynamic forces to changes of the geometry. Alternatively, Computational Fluid Dynamics (CFD) solvers can be partnered with optimization software which guide model design changes and evaluate the corresponding results. Design changes can be executed by modifying a parameterized geometry or using mesh morphing techniques. With the advances in computational fluid dynamics, design optimization methods in the aerodynamic design are more important than ever. In the present paper, ANSYS Fluent will be used in conjunction with the optimization software ANSYS DesignXplorer to study ways of reducing drag and lift for a simplified car body. ANSYS simulation software allows one to predict, with confidence, the impact of fluid flows on the product throughout design and manufacturing as well as during end use. CFD is a complex technology involving strongly coupled non-linear partial differential equations which attempt to computationally simulate theoretical and experimental models in a discrete domain of complex geometric shape. A detailed assessment of errors and uncertainties has to concern itself with the three roots of CFD: theory, experiment, and computation. Further, the application of CFD is rapidly expanding with the growth in computational resources. The body in question in this study is the Ahmed body [1] which has been used numerous times for CFD code validation. This geometry represents a road legal car which is used to study the effect of different forces like, aerodynamic drag force, lift force, and some other major forces which affect a car’s motion significantly. Despite being a simple body, accurate prediction of its aerodynamic performance often requires very accurate and computationally expensive calculations. We would like to investigate if meaningful optimizations can be achieved by using reduced resources, by analyzing how air at different velocity affect the body and what changes might be necessary for a further optimized performance.The purpose here is not to predict the absolute values of drag for this body, but to demonstrate that optimization can be performed with limited resources relying on information about drag deltas rather than absolute values. Keeping limiting resources in mind, a grid independence study wasn’t done.Copyright

Solving Military Vehicle Transient Heat Load Issues Using Phase Change Materials

Thermal management systems (TMS) of armored ground vehicle designs are often incapable of sustained heat rejection during high tractive effort conditions and ambient conditions. Latent heat energy storage systems that utilize Phase Change Materials (PCMs) present an effective way of storing thermal energy and offer key advantages such as high-energy storage density, high heat of fusion values, and greater stability in temperature control. Military vehicles frequently undergo high-transient thermal loads and often do not provide adequate cooling for powertrain subsystems.This work outlines an approach to temporarily store excess heat generated by the transmission during high tractive effort situations through the use of a passive PCM retrofit thereby extending the operating time, reducing temperature transients, and limiting overheating.A numerical heat transfer model has been developed based on a conceptual vehicle transmission TMS. The model predicts the transmission fluid temperature response with and without a PCM retrofit. The developed model captures the physics of the phase change processes to predict the transient heat absorption and rejection processes. It will be used to evaluate the effectiveness of proposed candidate implementations and provide input for TMS evaluations.Parametric studies of the heat transfer model have been conducted to establish desirable structural morphologies and PCM thermophysical properties. Key parameters include surface structural characteristics, conduction enhancing material, surface area, and PCM properties such as melt temperature, heat of fusion, and thermal conductivity.To demonstrate proof-of-concept, a passive PCM enclosure has been designed to be integrated between a transmission bell housing and torque converter. This PCM-augmented module will temporarily strategically absorb and release heat from the system at a controlled rate. This allows surging fluid temperatures to be clamped below the maximum effective fluid temperature rating thereby increasing component life, reliability, and performance. This work outlines cooling system boundary conditions, mobility/thermal loads, model details, enclosure design characteristics, potential PCM candidates, design considerations, performance data, cooling system impacts, conclusions, and potential future work.Copyright

Design and Optimization of the Restrictor of a Race Car

Formula SAE is a student competition organized by SAE International. The team of students design, manufacture and race a car. Restrictions are imposed by the Formula SAE rules committee to restrict the air flow into the intake manifold by putting a single restrictor of 20 mm. This rule limits the maximum engine power by reducing the mass flow rate flowing to the engine. The pull is greater at higher rpms and the pressure created inside the cylinder is low. As the diameter of the flow path is reduced, the cross sectional area for flow reduces. For cars running at low rpm when the engine requires less air, the reduction in area is compensated by accelerated flow of air through the restrictor. Since this is for racing purpose cars here are designed to run at very high rpms where the flow at the throat section reach sonic velocities. Due to these restrictions the teams are challenged to come up with improved restrictor designs that allow maximum pressure drop across the restrictor’s inlet and outlet. The design considered for optimizing a flow restrictor is a venturi type having 20 mm restriction between the inlet and the outlet complying with the rules set by Formula SAE committee.The primary objective of this work is to optimize the flow restriction device that achieves maximum mass flow and minimum pull from the engine. This implies the pressure difference created due to the cylinder pressure and the atmospheric pressure at the inlet should be minimum. An optimum flow restrictor is designed by conducting analysis on various converging and diverging angles and coming up with an optimum value.Venturi type is a tubular pipe with varying diameter along its length, through which the fluid flows. Law of governing fluid dynamics states that the “Velocity of the fluid increases as it passes through the constriction to satisfy the principle of continuity”. An equation can be derived from the combination of Bernoulli’s equation and Continuity equation for the pressure drop due to venturi effect. [1].A Computational Fluid Dynamics (CFD) tool is used to calculate the minimum pressure drop across the restrictor by running a series of analysis on various converging and diverging angles and calculating the pressure drop. As a result, an optimum air flow restrictor is achieved that maximizes the mass flow rate and minimizes the engine pull.Copyright

Study of Turbulent Incompressible Flow Separation on High Lift Devices Using Cutcell Meshing

Generating the mesh is a crucial part in all Computational Fluid Dynamics (CFD) analysis. Considerable time and effort have to be devoted into deciding the appropriate mesh densities that compromise between computing time and the desired accuracy. It is important that engineers generate high quality meshes around complex geometries which can capture the fine details of the inner layer.Flow separation develops when the velocity near a solid surface just becoming negative. An inflection point exists in the velocity profile due to a positive or adverse pressure gradient occurring in the direction of flow. The computational analysis carried out near wall sub-layer is one of the challenging issues due to the need for complex mesh generation.Separation has a major effect on the drag predictions, in this paper the authors look to extend their previous work [1, 2] to assess the capability of CutCell Cartesian meshing method for predicting the turbulent incompressible flow separation when applied to high lift devices. Although there is no experimental data available to verify the computational work, results can be the subject of future work to identify the factors which lead to flow separation experimentally. Complex aerodynamics shapes will be used and numerical simulation will be conducted using ANSYS Meshing and Fluent.Copyright

Optimum Driving Control Based on Throttling Mechanism Design

The performance of a racing engine is most dependent on the control of airflow entering the air intake manifold. In order to improve drivability and throttle response, the throttle angle within the throttle body must be precisely tuned with engine airflow. The actuation motion must be set as a direct function of the accelerator pedal position if this direct relationship is to be achieved.Many of the current throttling mechanisms are designed with a variable pedal-to-throttle response, meaning simply that a certain distance of pedal displacement does not necessarily result in a defined amount of throttle rotation. This setup, in most cases, is created by design in order to fit the type of vehicle being discussed. Known as brand DNA, this practice would, for instance, prescribe a smaller pedal-to-throttle ratio for a sports car than it would for a luxury car. This setup is acceptable for the common driver; however, in a racing situation a more precise relationship is needed.The airflow through a standard automotive throttle body is not exactly proportional to the displacement of the accelerator pedal. Therefore, another method is needed to open the butterfly valve in order to ensure that airflow through the throttle body is metered equal to pedal displacement. This paper finds that the implementation of a cam-type pulley is necessary to achieve this prescribed goal.© 2012 ASME