Advanced Materials Research Vol. 402

Abstract: In particle impact drilling system, the steel particles would be recycled for economic reason. Thus, whether particles can return to the ground under certain conditions is an important problem. In this paper, the relationship between critical flow rate and annular gap is numerically studied using the Eulerian multiphase model in FLUENT software. Both the numerical and the experiment results show that the critical flow rate decreases with the increasing annular gap, and the simulation results correspond well with experimental results.

Abstract: Every year, China suffers greatly from economic losses caused by rockfall hazards. The key to effectively control rockfall hazards is to obtain an accurate rockfall trajectory. However, not only is rockfall trajectory complex and unable to be described accurately in mathematical formula, but basic parameters influencing its movement are also unable to be measured directly. Therefore, the back analysis method combining laboratory rockfall simulation test with computer numerical simulation is adopted to study rockfall trajectory and its basic parameters. The results show that the method can not only get basic parameters of rockfall trajectory such as coefficient of restitution and angle of frication, but also precisely deduce true rockfall trajectory, which can provide help in effectively controlling rockfall hazards.

Abstract: To solve the high or low speed air-intake contradictions in the air-intake system of fixed parameters，based on predesigning the air-intake pipe length variable system in electronic controlled gasoline engine, the gas flow in the pipes is computed and simulated according to the simulative calculation method. The Performance of electronically controlled gasoline engine is analysed under the different speed and load.At the end,the dynamic performance influenced by the length parameter vary air-intake pipe,which findings provide a good reference value for the improvement of the engine’s dynamic performance.

Abstract: Influence of ultrasonic wave, argon blowing agitating and their coordinated treatment on nitrogen content in low carbon steel was mainly studied. Results showed that ultrasonic wave, argon blowing or their coordinated treatment can all reduce the nitrogen content in low carbon molten steel. While treated with ultrasonic wave separately, removal rate of the nitrogen in molten steel is relatively low with 3.13%~9.04%. Using the argon blowing agitating separately, removal rate of the nitrogen in molten steel is relatively high with 6.89%~32.68%, when the argon blowing flow is 0.5 l/min, removal rate of nitrogen is 32.68%. The nitrogen removal effect of the ultrasonic wave-argon blowing agitating coordinated treatment is considerably improved than that of separately ultrasonic treatment. While 300 W ultrasonic wave and 0.5l/min argon blowing agitating cooperatively treatment on the low carbon molten steel, the removal rate of nitrogen is 26.95%.

Abstract: Methane-air explosion is one of the main accidents in coal mines. In this paper, the hazard effects of the gas explosion in a long straight coal laneway were studied by virtue of numerical simulation. Distribution characteristics of the shock wave overpressure, the flame speed and the temperature field were obtained. Along the increasing axial distance, shock wave overpressure increases in original methane-air area and decreases beyond the original methane-air area. Range of flame exceeds original methane-air area. Flame accelerates continually in original methane-air area and decelerates beyond the original methane-air area. The temperature attenuates slowly along the increasing distance in the flame area by virtue of flame front, and attenuates quickly along the increasing distance beyond the flame region. High temperature hazard involves farther area beyond original methane-air area.

Abstract: Low frequency electromagnetic casting (LFEC) process was used to make 7050 aluminum alloy 162mm ingots and study its effect on the as-cast microstructure. Effects of electromagnetic field parameters such as frequency and current intensity on microstructures were systemically investigated. The results showed that LFEC has a significant grain refining effect on 7050 alloy. The microstructures of LFEC ingot from the border to the center of the cross section are all equiaxed or nearly equiaxed grains which are much finer and more uniform than those of DC cast ingot. It was also found that electromagnetic field frequency and current intensity play important roles on the microstructure refinement. The discussion was mainly focused on the mechanism of grain refinement by LFEC process.

Abstract: The research on the development strategies of conventional gas field is quite mature both in and abroad, but less attention has been paid on development strategies of coalbed methane reservoirs. This paper elaborates the remarkable dissimilarities of development strategies between coalbed and conventional gas, including commingled development design, reasonable dewatering rate and well pattern design. Eventually, Liulin area, in Hedong coal field located in Shanxi Province, China, was taken as an example to conduct optimum design of development strategies by numerical simulation software. All the aspects mentioned above can provide guidance to China’s CBM development.

Abstract: In this paper, aerosol samples were collected with Andersen cascade sampler on typical polluted days at residential area in Hangzhou, China. The concentrations of sulfate, nitrate and ammonium in aerosol were analyzed by the ion chromatography. Results showed the concentrations of SO₄^2-, NO₃^- and NH₄⁺ on polluted days were 21.4, 31.2 and 10.8µg m^-3 in fine particles, respectively, and were 1.3-1.7 times higher than on unpolluted days. SO₄^2-, NO₃^- and NH₄⁺ in fine particles were the main threat of athlete health in the urban area of Yangtze River delta.

Abstract: In order to meet the need of the study on the tunnel fire safety system, taking the tunnel laboratory bench in the key laboratory of the university of science and technology of China as the object, this paper does a scale model experiment on the tunnel fire, and uses the Fire Dynamics Simulator（FDS）software to simulate fire smoke layer velocity under different longitudinal ventilation control, by comparing the experimental and simulation results, this paper not only gives the variation law of the tunnel fire smoke layer velocity under different longitudinal ventilation speed, but also proposes the concept of the smoke stratification critical wind speed , which will provide some references for the road tunnel fire control, rescue and evacuation.