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To solve the water hazard problem of Jurassic coal seam roof sandstone in Yinxing No.1 Coal Mine of Ningxia Province, the direct relationship between the sedimentary environment of Jurassic coal seam roof sandstone and water abundance was analyzed and the water abundance of sandstone aquifer was evaluated on the basis of combing the geological and hydro-geological conditions of the mine. The mechanism and characteristics of water disaster in Jurassic coal seam roof sandstone were analyzed based on the study of the mechanical properties, mineral composition, water stability characteristics and water-conducting fracture development law of coal seam roof strata. In this paper, we propose the idea of comprehensively applying various measures of “exploration, drainage, discharge, interception and monitoring”, and focusing on the basic exploration work, using hydrophobic and depressurizing technology to control water damage. The water damage control effect of 110301 working face show that it was feasible to control the sandstone water damage on the roof of Jurassic coal seam through hydrophobic depressurization.

Rotor tip clearance has significant influences on both the performances and internal flow fields of compressors. To explore the relationship between these influences and compressor loading levels, four single-stage compressors, with loading levels ranging from 0.36 to 0.59, have been designed for experiments. Compressor characteristics and flow fields at blade row inlet and outlet planes were measured under two rotor tip clearance conditions: 1% and 2.2% blade height. Based on these experimental results, an analysis was conducted to examine the influence of loading levels on the sensitivity to rotor tip clearance. The experimental results indicate that increase in the loading level enhances the sensitivity of compressor stage characteristics to rotor tip clearance. At the design point, an increase of 1% in the rotor tip clearance causes reductions of 1.3% in the stage efficiency and 2.3% in the stage static pressure rise when the loading level is 0.36. However, when the loading level is 0.59, the reductions are 2.9% and 3.4% in stage efficiency and stage static pressure rise, respectively. Increasing the rotor tip clearance brings the static pressure rise at the rotor tip region closer to its limit, resulting in a rapid growth of local loss. This trend becomes increasingly pronounced with higher compressor loading level. [ABSTRACT FROM AUTHOR]

A novel method has been proposed to design inlet gauzes in single-stage low-speed simulation compressor experiments. The aim is to investigate the method for designing inlet profiles and understand how they affect the repeatability of the compressor. Based on the inlet gauzes, the effect of the inlet profile on the compressor repeatability and its flow mechanisms was investigated by the experiments. The experiment results show that, for the single-stage low-speed compressor, as the inlet flow coefficient decreases, the loss and blockage near the rotor casing caused by the tip leakage flow are enhanced, resulting in an increase in the local absolute velocity and the total pressure. Meanwhile, the radial migration of the secondary cross flow in the stator is enhanced, leading to a thinner boundary layer at the stator outlet near casing region. Consequently, the flow capacity near the casing at the compressor outlet is enhanced with a decrease in the inlet flow coefficient. Given that the flow structure and the local loss of the compressor are not sensitive to the inlet profile at the near-choked condition, employing the inlet profile generated based on the compressor outlet profile at the near-stall condition can simulate the repeating stage environment accurately in the single-stage low-speed compressor experiment. [ABSTRACT FROM AUTHOR]

In aero engines, designing shorter aggressive compressor transition ducts contributes to improved performance and weight savings. An experimental and numerical investigation has been carried out to explore the internal flow mechanism of an aggressive compressor transition duct, which laid the foundation for subsequently reducing the axial length of the transition duct. Two different total pressure and flow angle profiles were created through the gauzes to simulate the design condition and the near stall (NS) condition in the aero engine. The results showed that in the downward path, flow separation was more likely to occur in the stator hub corner. Hub corner stall occurred at NS condition as a result of a decrease in total pressure and an increase in flow angle, which significantly increased total pressure loss. The existence of hub corner vortex and the uneven flow field at the stator outlet contribute to reducing the tendency for the flow along hub to separation. However, the mixing of these vortices also increased the duct loss. And the velocity deficit produced by the stator hub corner separation/stall was intensified by the adverse pressure gradient in the hub region after the stator. [ABSTRACT FROM AUTHOR]