Suction characteristics of a thick material pump at high concentrations of coal slime

A test system was designed to study the parameters affecting the volumetric efficiency of a thick-material pump for coal slime.The parameters studied included solid concentration,the slenderness ratio of the suction cylinder and the running speed of the hydraulic cylinder.In the experiment the concentrations of coal slime were 75.7%,76.3%,74.4%,73.5%,72.1%and 70.63%;the running speeds were 0.23,0.18,0.13,0.10 and 0.08 m/s;and the slenderness ratios of the suction cylinder were 1.63,2.26,2.88,3.50,4.13,4.78 and 5.38.The results show that the suction volumetric efficiency decreases gradually with an increase in material concentration.The critical concentration value is 72%;below 72%the suction volumetric efficiency is above 90%,otherwise it decreases rapidly.When the solid concentration reaches 76.3%,the suction volumetric efficiency is only 40%.When the running speed of the piston is less than or equal to 0.23 m/s,the suction volumetric efficiency increases with an increase in running speed.

Experimental research on flame propagation characteristics of coal dust combustion

The presence of coal dust explosions in coal mining are significant safety hazards.This study mainly explores the flame propagation of coal dust combustion so as to provide a theoretical basis for the prevention and control of coal dust explosions.In the experiment,a dust cloud ignition device was used to experimentally explore the influence of the coal dust concentration on the flame propagation of the coal dust,and high-speed photography was used to record the coal dust flame propagation process.The results show that the flame propagates vertically along the wall of the vertical glass tube,emits a bright yellow light during the propagation process,and forms a mushroom cloud-shaped flame at the upper end of the vertical glass tube.When the concentration of coal dust is 250 g/m^(3),its burning time is much less than those of 500 g/m^(3)and 750 g/m^(3).When the concentrations are 250 g/m^(3),500 g/m^(3)and 750 g/m^(3),respectively,the corresponding maximum propagation velocities of the flame front reach 1.51 m/s,2.00 m/s and 1.61 m/s at 100 ms,353 ms and 310 ms,respectively.The time for the flame front velocity to reach the maximum and the maximum velocity of flame propagation first increase and then decrease with the rising of concentration.

Experimental measurements of gas-solid flow and splitting mechanisms of a coal pipe splitter with a perpendicularly arranged upstream elbow

The effect of the vertical pipe length on the performance of a coal pipe splitter with a perpendicularly arranged upstream elbow was investigated experimentally employing a fiber optic measuring system. The upstream elbow and coal pipe splitter were installed in two perpendicular planes. Contours of dis- tributions of the particle concentration and size were obtained in different transverse sections. The experimental data show that the maximum/minimum concentration ratio in transverse sections A, B, and C decreased rapidly as the length of the vertical pipe increased. The left/right-leg average concentration ratio remained about 1, and a balanced split was thus achieved. With a perpendicularly arranged upstream elbow, the vertical pipe length had little effect on the splitter performance, which is beneficial for engineering design and convenient for industrial application.