On Deepening Reform of Processing Trade Regulations

The processing trade has, since 1996, taken half of the total import and export trade value for a consecutive six years. Despite the impact and influence of the Asian financial crisis, it has maintained a momentum of steady growth. In the five years from 1997 to 2001, import and export value through the processing trade grew at an annual average rate of 10.5 percent, with exports growing at an annual average rate of 11.8 percent. This good growth momentum continued into

Flow response hysteresis of throat regulation process of a two-dimensional mixed-compression supersonic inlet

The variable geometry supersonic inlet tends to decrease the throat area to reduce the Mach number upstream of the terminal shock,so as to reduce the flow loss.However,excessive Internal Contraction Ratio(ICR)exposes the inlet to a greater risk of unstart,which inevitably results in a process of increasing the throat area to aid the inlet restart.In the above throat regulation process,the inlet undergoes the start,unstart,and restart states in turn.In order to reveal the flow structure and mechanism of this process,a two-dimensional unsteady numerical simulation combined with a dynamic mesh technique were employed.The shock-on-lip Mach number of the studied inlet is 4.0 and the flight angle of attack is+6°.Analysis was focused on the state with a freestream Mach number of 3.0.The results clearly show that the flow response hysteresis appears,and restart is only realized when the throat area is obviously increased as compared to that of unstart due to the historical unstart flow structure.In addition,three typical flow fields were analyzed,and it is found that the separation ahead of the inlet was the key factor affecting the hysteresis.Finally,unstart and restart boundaries of the inlet were discussed,and the factors influencing its deviation from the typical boundaries of dual-solution area were analyzed.The newly predicted unstart and restart boundaries are much closer to the CFD results.

Experimental investigation on unstart-restart hysteresis of a supersonic inlet during throat regulation

The hysteresis during the throat regulation process of a supersonic variable inlet is unconducive to restart.Hence,detailed experimental studies of such a hysteresis and its control are necessary.A throat variable supersonic inlet was designed at a shock-on-lip Mach number of 4.0 and an Internal Contraction Ratio(ICR)ranging over 1.21–2.94.Meanwhile,a distributed bleed system was proposed to suppress the hysteresis.The wind tunnel tests were conducted at Mach number 2.9.The throat regulation processes were recorded using a high-speed schlieren and dynamic pressure acquisition system.The results indicate that the unstart and restart ICRs during the uncontrolled inlet’s throat regulation process were 1.95 and 1.48,respectively,demonstrating an unstart-restart hysteresis.Four typical flowfields were summarized during the uncontrolled inlet’s restart process.The proposed bleed control increased the unstart and restart ICRs to 2.06 and 1.75,respectively,and the inlet realized the designed state as the ICR was further decreased to 1.67.The controlled inlet’s hysteresis loop was decreased compared to the uncontrolled inlet.Finally,the mechanism of the hysteresis,dominated by the entrance separation-induced wave system,was clarified.The mechanisms of the bleed control to broaden the unstart and restart boundaries and suppress the hysteresis were elucidated.