Application of Parametric Design to Mechanical Engineering

The definition and functions of parametric design were introduced. According to the practical condition of mechanical engineering design, the necessity and feasibility of parametric design for complex mechanical engineering design was analyzed. The related key technologies and methods were also discussed by a project example based on Inventor platform.

Service Power Rate and Electricity-Saving in Conventional Thermal Power Plants

Since reforming and opening to the outside world, the power construction in China has been expanding by leaps and bounds. As of the end of 2005, the nationwide generation installed capacity made a breakthrough of 500 GW, of which thermal power units represented three-fourths. Relevant predictions indicate that the installed capacity will reach 680-730 GW in 2010 and it will exceed 1000 GW in 2020 as expected.The present situation of service power rate of thermal power units and how to make it approach and come up to world level are questions to be discussed in this paper.

Malfunction analysis of OPGW of stainless steel-unit structure

Composite fiber optic overhead ground wire (OPGW) is increasingly applied in China's overhead transmission lines. The stainless steel structure is adopted by most OPGWs as it is very small and easy to match the existing ground wire. The malfunction of OPGW in Beijing-Shanghai Optical Communication Project was analyzed through the chemical composition method and spectrum semi-quantitative method. The analysis indicates that the cable fault was due to the failure of seepage and irregular holes in the steel pipe of the optical unit. The rain water and the watery air entered into the optical units, and the water in turn became ice when temperature dropped. The occurrence of ice led to the acceleration of attenuation of the fiber. The results show that the rupture of stainless steel tube is mainly due to the instability of welding technique. The malfunction of OPGW is due to the local defects of welding seam because of local stress concentration in the manufacturing process.

Abnormality monitoring model of cracks in concrete dams

The abnormality monitoring model (AMM) of cracks in concrete dams is established through integrating safety monitoring theories with abnormality diagnosis methods of cracks. In addition, emphasis is placed on the influence of crack depth on crack mouth opening displacement (CMOD). A linear hypothesis is proposed for the propagation process of cracks in concrete based on the fictitious crack model (FCM). Abnormality points are detected through testing methods of dynamical structure mutation and statistical model mutation. The solution of AMM is transformed into a global optimization problem, which is solved by the particle swarm optimization (PSO) method. Therefore, the AMM of cracks in concrete dams is established and solved completely. In the end of the paper, the proposed model is validated by a typical crack at the 105 m elevation of a concrete gravity arch dam.

Shale gas accumulation conditions and gas-bearing characteristics of the Lower Cambrian Niutitang Formation in Well Changye-1 in northwestern Hunan Province

To evaluate the accumulation conditions and gas-bearing properties of shale gas in the Lower Cambrian Niutitang Formation,northwestern Hunan Province,the first shale gas parameter well(Well Changye-1)that takes the Niutitang Formation as the target horizon in the Hunan Province was selected preferably and drilled,cumulatively revealing the thickest dark shale horizon of the Niutitang Formation among the single-well drillings in China,with a true vertical thickness of 674.5m.Through analyzing the core samples in terms of organic geochemistry,rock mineralogy and reservoir properties,the black shale horizons in the Niutitang Formation of Well Changye-1 have high organic carbon content(average 3.9%),moderate maturity(equivalent Ro average 2.6%),high brittle mineral content(quartz content average 50.1%),low clay mineral content(average 32.4%),low porosity(1.7%)and low permeability(1.32×10^(-3)mD),and well-developed meso to micro-pores and fractures,indicating good conditions for shale gas accumulation.Field desorption and laboratory isothermal adsorption measurements on core samples show that Well Changye-1 has good gas-bearing properties,and gas content generally increases with depth.The black shale horizons at the depth of 1100-1250m have an average organic carbon content up to 10.1%,total gas content of 0.5-2.1m^(3)/t and 3.7-6.4m^(3)/t,and this is the most favorable depth for shale gas development,indicating that the Niutitang Formation has good a prospect for shale gas exploration.Due to huge sedimentary thickness,the black shale in the middle-lower part of the Niutitang Formation should be given priority for exploration.