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 (Tb_0.3D_0.7Fe_1.9) possesses intrinsic rapid response times while providing small and accurate displacements and high-energy efficiency, which 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 using Pro-Engineer which included magnetostrictive material Terfenol-D as the actuator material. A 2D cross-sectional geometry of the injector assembly, which incorporated the real linear or non-linear magnetic properties of corresponding materials, was modeled in both Finite Element Method Magnetics (FEMM) and ANSYS for 2D axisymmetric magnetic simulation. The coil-circuit parameters and the magnetic field strength were determined to achieve the required magnetostrictive strain, and consequently, the injector needle lift. The FEMM magnetic simulations were carried out with four different types of AWG coil wires and four different coil thicknesses. Eventually, the optimized parameters that were obtained for each coil thickness from FEMM results analysis were verified against ANSYS non-linear electromagnetic simulation, which showed identical consequences. 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 standard k-epsilon viscous model to determine 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.

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1. Tensile Stress-Strain Relationships of Magnetorheological Fluids under Various Factors