Experimental Study on Combined Cooling Method for Porous Struts in Supersonic Flow

A combined transpiration and opposing jet cooling method was experimentally investigated for protecting porous struts with microslits in the leading edge. Schlieren images showed that this cooling method significantly affects the stability of the flow field and the profile of the detached shock wave. Three different states of flow fields were observed when increasing the coolant injection pressure of a strut having a 0.20 mm wide microslit. The detached bow shock was pushed away by the opposing jet; it then became unstable and even disappeared when the coolant injection pressure was increased. Combined transpiration and opposing jet cooling could effectively cool the entire strut, especially the leading edge. The leading edge cooling efficiency increased from 3.5% for the leading edge without a slit to 52.8% for the leading edge with a 0.20 mm wide slit when the coolant injection pressure was 0.55 MPa. Moreover, combined transpiration and opposing jet cooling with nonuniform injection distribution made the strut temperature distribution more uniform and caused the maximum temperature to decrease compared to standard transpiration cooling.

Numerical Analysis of Fan Transonic Stall Flutter

This paper describes numerical investigation of fan transonic stall flutter, especially focused on flutter bite. A transonic stall flutter occurs in high loaded condition at part rotating speed. A region of the transonic stall flutter occasionally protrudes to an operating line at narrow rotational speed range. This protrusion of flutter boundary is called flutter bite. In that case, it is necessary to re-design the blade for securing sufficient operating range. The re-design process might require some compromise on performance and/or weight, and takes long time. So it is important to understand the mechanism of the flutter bite. Two types of fan blade, one has a flutter bite and another dose not, are numerically studied with a 3D Navier Stokes CFD code. Numerical results show agreement with rig test results for the fans in qualitative sense. Detailed flow fields reveal that a detached shock wave and separation due to the shock boundary layer interaction play significant role for the flutter stability.

Numerical Study on Damage Response of Ship Composite Armor Structures to Contact Underwater Explosion

As a new type of protection design, composite armor structures have good performance in impact resistance, and have been widely used in ship structure protection. Due to its academic value and potential applicability, the dynamic characteristics of ship composite armor structures were studied in this paper. The whole process of the shaped charge’s explosion and penetration, and the ship composite armor structures’ damage response were described. According to the numerical simulation with Ansys-Autodyn, it was found that the ship composite armor structures were damaged not only by the explosively formed projectile but also by the detached shock wave in the conditions of contact underwater explosion and the thickness of composite armor structures was the main factor effecting the impact resistance properties.