Study on the instability of airflow in mine hoisting-shaf

In order to discover the airflow pattern in mine shaft which outfitted with hoist equipment （HE）, this paper set up the physical model and anatomized the piston-wind caused by hoist equipment, and researched the flow field and velocity field around the hoist equipment during its moving process, and analyzed the airflow around single and couple hoist equipment as well as decisive range of piston effect and additional effect of hoist equipment to ventilation system. Research conclusion indicate that during hoist equipment movement, airflow pattern changes repeatedly because of the influence of pis-ton effect from hoist equipment, and the study of airflow stability in shaft is the foundation for the stability of ventilation in mine.

Flow Instability and Its Control in Compression Systems

This paper reviews the development in the research of flow instability and its control over the recent ten or more years. This development was largely stimulated by the novel idea of active control of the aerodynamic instability in compressors. Three topics are covered in the paper, which appeared as the major themes towards the goal of stability enhancement. The first topic is the pre-stall behavior of rotating stall, which plays a vital role in designing the control scheme and discovering the convenient route to find the causal factors of flow disturbances potentially leading to stall. The second topic is the mechanism of blade passage flow during stall and its inception, which is the basic knowledge needed to manipulate the blade design for the stability improvement and eventually to predict the unsteady performance of the compressor system. The third topic is the recent trend of the control strategy based on the learning of active vs. passive methods. To introduce to the discussion of these topics, a brief description of the history of the recent development is given at the beginning of the paper. In discussing each topic, future works are also highlighted to enhance the further development of this long-standing problem in turbomachinery research and application.

Unsteady Tip Clearance Flow Pattern in an Isolated Axial Compressor Rotor with Micro Tip Injection

A numerical study of the effect of discrete micro tip injection on unsteady tip clearance flow pattern in an isolated axial compressor rotor is presented, intending to better understand the flow mechanism behind stall control measures that act on tip clearance flow. Under the influence of injection the unsteadiness of self-induced tip clearance flow could be weakened. Also the radial migration of tip clearance vortex is confined to a smaller radial extent near the rotor tip and the trajectory of tip clearance flow is pushed more downstream. So the injection is beneficial to improve compressor stability and increase static pressure rise near rotor tip region. The results of injection with different injected mass flow rates show that for the special type of injector adopted in the paper the effect of injection on tip clearance flow may be different according to the relative strength between these two streams of flow. For a fixed injected mass flow rate, reducing the injector area to increase injection velocity can improve the effect of injection on tip clearance flow and thus the compressor stability. A comparison of calculations between single blade passage and multiple blade passages validates the utility of single passage computations to investigate the tip clearance flow for the case without injection and its interaction with injected flow for the case with tip injection.