Advanced Materials Research Vols. 455-456

Abstract: The effects of fuel octane number (RON) on homogeneous charge compression ignition (HCCI) combustion were studied under different combustion boundary conditions on a rapid compression machine. The results show that the maximum pressure raise rate and maximum combustion temperature decreased as the RON increased while the start of combustion is delayed and the combustion duration is shortened at the same time.

Abstract: With the development of natural gas industry, improving the accuracy of the flowmeter systems is becoming the common concerned problem both corporations and customers. Many experiments demonstrate that the different flow field structures in pipes with diverse baffle installations have great influence on the measure accuracy of flowmeters. In order to measure the flux in pipes more accurate, the flowmeters must be installed downstream the baffles far away so that the irregular flows induced by baffles have less influence on the flowmeters. However, the installation lengths downstream baffles for flowmeters in ISO are are usually much longer than the allowable lengths for the local flowmeters. To decrease the installation lengths and loss measure accuracy of flowmeters as little as possible, it is necessary to study the flows in pipes with baffles. CFD is a good tool for the study. Here, the flows in a diffusive pipe with various rectifiers are computed as examples. The lengths of the irregular flows induced by the diffuser and rectifier are shown. By analyzing and comparison the numerical results, the installation lengths for flowmeters and the rectification of the different rectifiers are confirmed. The study conclusions will be very useful for guiding the local flowmeter selection and installation in the future.

Abstract: In order to research the effects of leading edge shapes on the strength of centrifugal compressor compeller, the shrouded impellers of a large centrifugal compressor were introduced for finite element analysis. In the present study, the geometric models of 3 shrouded impellers were established in Solidworks 2007, and then numerical simulations were carried out using ANSYS. Through visualization of the computational result of the impellers with a square leading edge, a semi-circular leading edge and a elliptical leading edge, it was clarified by comparison that different leading edge shapes had significant influences on the compressor strength. According to the charts of the Von Mises stress versus leading edge shapes, it was indicated that approximately a 27% drop and a 32% drop in maximum Von Mises stress value occurred in the shrouded impellers of a semi-circular leading edge and a elliptical leading edge compared to a square leading edge respectively. That is, the semi-circular leading edge or elliptical leading edge employed in a centrifugal compressor would dramatically improve structural strength. This paper aims to provide the reference significance the structural optimization and reliability improvement of a large flow centrifugal compressor.

Abstract: A novel combined longitudinal vortex generator, comprising a rectangular wing mounted with an accessory rectangular wing, was introduced and the turbulent flow and heat transfer characteristics of a rectangular channel with rectangular winglet pair and combined winglet pair were numerically analyzed. The effects of six parameters were examined. The results show that in the range of the present study, the increase of the six parameters can result in the increase of heat transfer and pressure drop. Specially, the pressure drop decrease at large value of the distance of accessory wing from the channel bottom. The effect of the main attack angle of the combined winglet pair is somewhat different to that of the rectangular winglet pair. The heating plate temperature of the channel with combined winglet pair is lower than that of the channel with rectangular winglet pair, and hence the heat transfer is enhanced.

Abstract: Nanocrystalline SrSiO₃ with different morphologies was first selectively prepared by a facile template-free solvothermal method at different water/ethanol volume ratios. The as-prepared samples were characterized by X-ray diffraction, N₂-sorption, field emission scanning electron microscopy. The results showed that the as-prepared samples SrSiO3 displayed nanoflakes in pure water while obtained nanofibres in mixed solvent of water and ethanol (the volume ratio of water to ethanol is 1:1.). The BET specific surface area of SrSiO₃ nanofibre is 161.7 m² g^-1, which is much higher than that of nanoflake one. The mechanisms about the formations of shape-controlled SrSiO₃ are proposed and discussed based on a reaction-crystallization process. As a novel photocatalyst, the photocatalytic activity of as-prepared samples SrSiO₃ were evaluated by the photocatalytic degradation of orange II (20 mg L^-1) and the total organic carbon (TOC) value indicated that orange II solution can be mineralized in 120 min.

Abstract: In hydrogen-cooled generator, the quality of hydrogen environment directly affects generator’s operating especially the retaining ring. In order to research the relationship between the hydrogen environment and stress corrosion of material, the metallographic analysis is held for retired retaining ring of a power plant. There were intergranular and transcrystalline cracks, similar with hydrogen embrittlement. Designed generating system of occurrence for wet hydrogen, hydrogen charging is operated to retaining ring material used in tensile test, and then observed fracture by scanning electron microscope. The results showed that fracture was including cleavage, dimple and secondary crack caused by hydrogen-induced lagging plastic deformation.

Abstract: Energy storage technology is becoming more important nowadays due to use of renewable energy resources. The heat transfer performance of a PCM (phase change material) which is the carrier of energy is the main factor that affects its utilization. This paper presents the thermal characteristics of the PCM-20. An energy storage module is designed based on the numerical calculation results from the MATLAB. Numerical simulation about this module is carried out by CFD software. The simulation results have been compared with the results of numerical calculation and the error between them has been analyzed and discussed.

Abstract: The sodium silicate has activation function on the macroscopic mechanical properties and microscopic structure of the gas quenching steel slag cement. Research results show that: Under the activation of the sodium silicate, when the content of the gas quenching steel slag cement is 30% to 40%, acid Salt, Portland cement grade 42.5 can be produced. Even when the content of gas quenching steel slag is improved to 50%, slag Portland cement grade P·S·A32.5 can still be produced. Seen from the hydration products, the sodium silicate reacts with the ions in the gas quenching steel slag, on one hand, initial framework is formed to enrich the network structure; and on the other hand, in the hydration process, a large number of C-S-H gel, ettringite crystal and a small amount of Ca (OH)₂ are formed, which improves the strength of cement.

Abstract: The flow inside the impeller and diffuser of a turbocharger compressor was analyzed numerically in this paper. The results indicate that the internal flow is disturbed and efficiency is low. There exists a big vortex in the diffuser which dissipates a large amount of energy. Based on the commercial design software, different design parameters were optimized by trial-and-error. Numerical flow analysis results of the final design show that the efficiency is increased by 6.26% and internal flow is improved greatly. It can be concluded that the meridian radius of the impeller flow path has great effect on the compressor performance.

Abstract: Three-high gas well is High-production gas well, High-temperature gas well and High-sulfur gas well.In the mining process of three-high gas wells, due to the impact of the role of the fluid and the tubing string fluctuations lead to severe vibration, the role could easily lead to severe vibration column damage. Based on the high gas flow during the mining shaft and column structural characteristics, taking into account the weight of the tubing string, the packer constraints impact characteristics of steel tubing, pre-stressing, the fluid pressure force on the tubing string's vibration characteristics. Established a tubing string vibration equation, and the establishment of the corresponding mass matrix obtained, the stiffness matrix and damping matrix. Lanczos algorithm with inherent characteristics of the pipeline parameters. The modal superposition method to analyze vibration characteristics of the tubing string, to ensure that the calculation speed in the case met the approximate solution of engineering precision, For the three-high gas wells safe, efficient production of effective technical support.