Papers by Author: H.A. Chowdhury

Abstract: This paper presents experimental investigations of three MR fluid types under the influence of several factors in tension loading mode. One MR fluid was water-based, MRF-241ES, while the other two were both hydro-carbon based, MRF-132DG and MRF-122-2ED. The magnetic properties of the MR fluids varied significantly due to a higher particle density in the water-based MR fluid compared to the hydrocarbon-based MR fluids. Tension as a squeeze mode, is as an operational mode where two flat parallel surfaces, standing opposite to each other, are pulled apart from each other by an external force, acting along the path of the magnetic flux lines. The experiments were performed in a vertical direction in the environment of a DC magnetic field. Stress-strain curves of the MR fluids under tension showed similar characteristics despite the fact that different types of the carrier fluids were used. The results revealed that the magnitude of the stress, for a given strain value, depended on the applied current and the initial gap size. It was found that, for higher applied currents and smaller initial gap sizes, there were larger stress values. However, the tensile speed had no significant effect on the stress-strain curves of MR fluids.

Abstract: Magnetostriction is the deformation that spontaneously occurs in ferromagnetic materials when an external magnetic field is applied. In applications broadly defined for actuation, magnetostrictive material Terfenol-D (Tb0.3Dy0.7Fe1.9) possesses intrinsic rapid response times while providing small and accurate displacements and high-energy efficiency. These are some of the essential parameters required for fast control of fuel injector valves for decreased engine emissions and lower fuel consumption compared with the traditional solenoid fuel injection system. A prototype CNG fuel injector assembly was designed which included magnetostrictive material Terfenol-D as the actuator material. A 2D cross-sectional geometry of the injector assembly, which incorporated both linear and non-linear magnetic properties of the corresponding materials, was modeled in ANSYS for 2D axisymmetric magnetic simulation. Subsequently, a 3D replica of the CNG flow conduit was modeled in GAMBIT with the resultant injector lift. The meshed conduit was then simulated in FLUENT using the 3D time independent segregated solver with the Standard k  , the Realizable k   and RSM turbulence models to predict the mass flow rate of CNG to be injected. Eventually, the simulated flow rate was verified against mathematically derived static flow rate required for a standard automotive fuel injector considering standard horsepower, BSFC and injector duty cycle.

Abstract: In applications broadly defined for actuation, magnetostrictive materials possess intrinsic rapid response times while providing small and accurate displacements and high-energy efficiency, which are some of the essential parameters for fast control of fuel injector valves for decreased engine emissions and lower fuel consumption. This paper investigates the application of Terfenol-D as a magnetostrictive actuator material for CNG fuel injection actuation. A prototype fuel injector assembly, including Terfenol-D as the core actuator material, was modeled in both Finite Element Method Magnetics (FEMM) and ANSYS Electromagnetics simulation softwares for 2D magnetics simulation. Preferably, FEMM was used in order to determine the coil-circuit parameters and the required flux density or applied magnetic field to achieve the desired magnetostrictive strain, consequently, the injector needle lift. The FEMM magnetic simulation was carried out with four different types of AWG coil wires and four different coil thicknesses of the entire injector assembly in order to evaluate the relationship between the different coil types and thicknesses against the achieved strain or injector lift. Eventually, the optimized parameters derived from FEMM were inserted into ANSYS Electromagnetics to compare the variation of results between these two simulation environments.