Fuze New Missile-borne Piezoelectric Generator Airflow Control Air Intake Flow Field Numerical Simulation

The pneumatic piezoelectric generator of missile-borne fuze is a supply unit for modern fuze, and the air inlet is an important mechanical structure of its air driving system. The distribution of airflow velocity and turbulence intensity in air inlet decides the functioning of generator and the transmission of airflow momentum. Considering that it is very difficult to analyze the flow field in air inlet with analytical method or experimental method, Computational Fluid Dynamics (CFD) is used in the graduation thesis of the research on the response of flow pattern inside the air inlet construction with different characteristic dimensions when the Reynolds number is low and the input flow is asymmetrical.First,the numerical simulation method is described,the shear-stress transport turbulence model of near wall, and buildsthe transition model are discussed. On this basis, this paper studied the Second-order Up-wind discrete format, SIMPLEC and the hybrid-grid partition method which would be applied.Then, the warhead's shock theory and the transition theory of the boundary layer inside pipe was briefly discussed, and the boundary conditions of governing equation was explored. According to the theoretical analysis, the input flow of the air inlet of the pneumatic piezoelectric generator for fuze can be taken as the asymmetric and low Reynolds number flow.Finally, by applying the improved turbulence-transition model to close N-S equation, numerical calculation of flow field was done in three typical air inlets of fuze, namely, uniform section straight orifice, uniform section annular space and variable section trumpet.The results indicated that numerical simulation method with CFD can be used to simulate the response of flow pattern inside the air inlet of fuze. The responses of transition in three air inlets of fuze, the distribution-difference coefficient of the velocity and turbulence intensity, wall friction resistance coefficient and the thickness of boundary layer appeared different regularity with the changed asymmetric inflow conditions. The uniform section annular space fuze inlet has features of slowed flow, faster uniformly distribution of velocity by section, and shorter initial transition position. These features are more significant when the gap is smaller. Therefore the uniform section annular space fuze inlet is an appropriate air inlet construction for missile-borne pneumatic piezoelectric generator.