The study described in this article is the application of energy method for the prediction of flutter boundary and the effects of some parameters on aeroelastic stability in turbomachinery. The unsteady flow with multi-layer moving grid technique for blade oscillation was undergone for aerodynamic work with the blade passage being discretized using a background fixed H-grid and a body-fitted O-grid moving with the blade. Also, with the assumption of equivalent viscous damping, aerodynamic modal damping ratio was defined based on energy method. The numerical method, with mode shapes and nodal diameter numbers considered, was applied for a transonic compressor rotor stage for which measured flutter boundary on characteristic map was available. It was found that the calculated flutter boundary in the first bending blade mode agreed well with the measured one. Furthermore, it was concluded that the mode shapes and inter-blade phase angle were key parameters on aeroelasticity in turbomachinery and that the flutter instability was mainly induced by the co-action of shock wave and separated flow.

The flexion effect of a flexible wing during the hovering flight is systematically studied by using computer simulations when Reynolds number is kept at 140. The aerodynamic forces and flow vortex are investigated by solving the two-dimensional time-dependent incompressible Navier-Stokes equations using the finite volume method. The wing is modelled as a thin plate which has a rigid leading portion and a flexible aft part. The simulations are performed for a variation of the location of rotational centre and the amplitude of the flexion, and the corresponding changes of the aerodynamic forces and vortex shedding mechanism in the wake structure are investigated. Form the quantitative comparisons, the present simulations reveal that a moderate flexion during the hovering fly can provide a better performance for a flapping wing, while an excessive flexion will lead the aerodynamic performance become worse. Though the flexion does not change the force trace of the hovering wing, the magnitude of the instantaneous peak forces and mean periodic forces are definitely changed by the chordwise deformation. Compared with a rigid hovering wing, the dynamic flexion during hovering alters the intensity of the leading edge vorticity and the transfer direction of the wake. Here, the present results indicate that the aerodynamic forces can be altered by adding some deformation characteristics to the trailing edge of the wing. Furthermore, the appropriate flexion can be used to alter the aerodynamic performance of a wing and will be helpful for design and control of the flexible microflying vehicles.

In order to study the interior ballistic characteristics of cased telescoped ammunition (CTA) armor-piercing projectile in the hypervelocity launch process, in this paper, based on the secondary ignition and propellant combustion technology, the zero-dimensional internal ballistic model of CTA is established. At the same time, in order to improve the lightweight of CTA and the energy utilization rate of the launch process, combustible cartridge materials are applied to the structure of cased telescoped ammunition. Numerical simulation of 105 mm CTA grenade shooting experiment has verified its correctness. On this basis, the internal ballistic process of 105 mm CTA armor-piercing projectile with semi-combustible cartridge is predicted and analyzed. When main charge propellant weight is 6 kg, the maximum pressure is 569.5 MPa and the muzzle velocity can reach 1702 m/s.

The high temperature and pressure gas in the combustion chamber pushes the projectile towards the muzzle during the firing of the gun. The projectile belt is squeezed and deformed by the forcing cone. In order to study the dynamic engraving characteristics of the projectile, a short-barrel gun launcher was designed for experimental research. The projectile dynamics and projectile base pressure curves during the engraving process were obtained. Based on the experimental loading conditions, the J-C elastic-plastic model was used to numerically simulate the dynamic engraving process of the copper elastic belt. The deformation process of the elastic belt and the change characteristics of the resistance after the elastic were studied and the intrusion displacement obtained by the numerical calculation was compared with the experimental results and the results are consistent.