Flow Mechanism for Stall Margin Improvement via Axial Slot Casing Treatment on a Transonic Axial Compressor

Axial slot CTs were designed and applied on Rotor 67 to understand the physical mechanisms responsible for the improvement of the stall margin. Unsteady Reynolds-averaged Navier-Stokes was applied in addition to steady Reynolds-averaged Navier-Stokes to simulate the flow field of the rotor. The results show that aerodynamic performance and the rotor stability were improved. Stall margin improvement (SMI) improved by 26.85% after the CT covering 50% of the axial tip chord was applied, whereas peak efficiency (PE) decreased the least. The main reason for the rotor stall in the solid casing is the blockage caused by tip leakage flow. After axial slot CTs were applied, the tip leakage flow in the front part of the chord was obviously reduced, and the majority of the blockages in the tip region were removed. The absolute value of the axial momentum before 45% axial chord in CT_50 was reduced by 50%, whereas the maximum tangential momentum value of CT_50 was decreased by 70% relative to the solid casing. CT_50 configuration was located across the shock wave; thus, it can fully utilize the pressure gradient to bleed and remove the blockage region, and the across flow is considerably depressed

Research on Spacecraft Integrated Electronic System Architecture Based on Information Fusion

This paper has designed the integrated electronic system and protocol architecture based on the standard of Consultative Committee for Space Data Systems (CCSDS) and European Communication Satellite System (ECSS). The application layer, application support layer, transport layer and sub network layer in the architecture can be described in detail, and the functions can be realized through the combination of various business and protocols. The architecture can provide technical support for the intellectualization and networking of spacecraft, standardize the spacecraft interface and protocol, it can promote the generalization of spacecraft equipment and software, and provide more flexible and powerful functions for the spacecraft

Research on Spacecraft Integrated Electronic System Architecture Based on Information Fusion

This paper has designed the integrated electronic system and protocol architecture based on the standard of Consultative Committee for Space Data Systems (CCSDS) and European Communication Satellite System (ECSS). The application layer, application support layer, transport layer and sub network layer in the architecture can be described in detail, and the functions can be realized through the combination of various business and protocols. The architecture can provide technical support for the intellectualization and networking of spacecraft, standardize the spacecraft interface and protocol, it can promote the generalization of spacecraft equipment and software, and provide more flexible and powerful functions for the spacecraft

Research on Optimization Algorithm of RSSI Positioning Parameters Based on Improved Particle Swarm Optimization

The paper put forward to an algorithm based on hybrid mutation particle optimization swarm strategy (HMPOA), it can solve the position coordinates of the unknown nodes. The algorithm uses static sampling to determine the performance index values of particles, then the arc grouping method is used to divide the particle swarm into several subgroups. Finally, the hybrid mutation strategy is used to improve the convergence speed and positioning accuracy of the algorithm, which can overcome the location accuracy of unknown node that overly dependent on the RSSI physical measurement value. Numerical experiments show that the algorithm has fast convergence speed and high positioning accuracy for unknown nodes, and it is feasible for RSSI positioning

Research on Optimization Algorithm of RSSI Positioning Parameters Based on Improved Particle Swarm Optimization

The paper put forward to an algorithm based on hybrid mutation particle optimization swarm strategy (HMPOA), it can solve the position coordinates of the unknown nodes. The algorithm uses static sampling to determine the performance index values of particles, then the arc grouping method is used to divide the particle swarm into several subgroups. Finally, the hybrid mutation strategy is used to improve the convergence speed and positioning accuracy of the algorithm, which can overcome the location accuracy of unknown node that overly dependent on the RSSI physical measurement value. Numerical experiments show that the algorithm has fast convergence speed and high positioning accuracy for unknown nodes, and it is feasible for RSSI positioning

Characteristics and Environmental Factors of Stoichiometric Homeostasis of Soil Microbial Biomass Carbon, Nitrogen and Phosphorus in China

Marine studies have shown that the carbon:nitrogen:phosphorus (C:N:P) atomic ratio in planktonic organisms is generally 106:16:1, which is known as the “Redfield ratio„. This raises the question of whether there are similar patterns in terrestrial organisms, particularly in soil. In this study, we extracted 404 datasets from the literature to analyze the ecological stoichiometry of C, N and P, both in the soil and in the soil microbial biomass in China; additionally, we assessed their relationships with environmental factors, and calculated the homeostasis coefficient (H) of soil microbial biomass. First, although the concentrations of C, N and P in soil and soil microbial biomass showed high spatial heterogeneity, the atomic C:N:P ratios in the soil and soil microbial biomass were relatively consistent at the national scale. Second, the influences of temperature and precipitation on stoichiometric relationships among C, N and P in the soil and soil microbial biomass were limited in China; however, they decreased with the increase in soil pH. Third, the degree of stoichiometric homeostasis for soil microbes spanned a wide range, from non-homeostasis to strict homeostasis. For single elements, most of the soil microbes’ H ranged from 1.01 to 5.00; for elemental ratios, most of the soil microbes’ H displayed strict homeostasis. This study indicates that the “Redfield-like„ ratio exists in the soil microbial biomass in the 0–20 cm soil layer in China, with an atomic C:N:P ratio of 66:8:1 and it is close to the atomic C:N:P ratio in the soil (66:5:1) of terrestrial ecosystems. In addition to the N:P ratio in plants, the soil microbial biomass N:P ratio may also be used to judge the nutrient limitations because of its high stability

The Investigation of a New End Wall Contouring Method for Axial Compressors

To further control corner separation in high-load axial compressors, this study proposes a new end wall contouring method. It defines multiple standard “surface units” with particular flow control effects and then applies a linear combination, finally forming the geometry of the end wall surface. Based on design experiences, three different end wall contouring cases are generated and calculated on a high-load compressor cascade in the first step. The results show that the new method achieves a clear and intuitive influence on the end wall geometry, with a proper number of design variables, and can effectively combine variables with the development of secondary flow. In the second step, the new method was applied to an axial compressor, with an improvement in the design variables. Although the end wall contouring only improved the efficiency of the compressor stage on the right part of its operating map, the experimental results of the flow field show that the corner separation and end wall loss are suppressed at multiple inflow conditions. The results thus verified the practical effect of the newly developed end wall contouring method

Numerical Investigation into a New Method of Non-Axisymmetric End Wall Contouring for Axial Compressors

To deal with corner separation in high-load axial compressors, this paper proposes a new end wall contouring method aimed at controlling the end wall secondary flow in more than one local area, generating a geometry with fewer control variables that is applicable for multiple working conditions. The new method defines more than one surface unit function, with different effects on end wall secondary flow. Then, the geometry of these surface unit functions will be superposed to generate the end wall contouring, to combine their flow control effects. After applying the new method to a bi-objective optimization design process, with 15 design variables aimed at minimizing the loss of cascade at 0° and 4° incidence, the optimal design reduces the total pressure loss of the high-load cascade by 5% under the former incidence and by 3% under the latter. The most effective design rule is constructing an end wall surface with the rising suction side and sinking pressure side in the blade channel, while locally raising the SS corner with a gentle upstream slope. According to the analysis, the design variables of the new method show an intuitive influence on the variation of end wall geometry and the movement of secondary flow. The corner separation has been effectively suppressed, with fewer control variables than before. It, thus, indicates the advantage of the newly developed end wall contouring method compared with previous studies