Summary
The three‐phase foam consisted of solid, liquid and gas is regarded as a highly effective measure for the underground mine fire prevention. In this study, the three‐phase foam technology is introduced and a visualization platform is established to exhibit the foam flow in a physical goaf. The diffusion rule and extinguishing performance for three‐phase foam are researched. Test results show that the three‐phase foam has a superior heat resistance than expansion foam in the top goaf. The coal heating rate is postponed after the three‐phase foam processing and the active functional groups are suppressed effectively. Increasing the foam expansion ratio is adverse to the three‐phase foam stability. The field application of three‐phase foam was evaluated via the practical extinguishment effect. The marked reduction in the sealed zone temperature and CO concentration proved that the proposed three‐phase foam technology was effective on controlling the concealed goaf fire.
The water-sediment two-phase seepage in coarse fractures is one of the major factors to trigger mine water inrush disasters. Based on seepage mechanics theory, a mechanical model of the water-sediment two-phase seepage in coarse fractures was established. An experimental system was also developed to study the seepage characteristics under various conditions. The relationships between the absolute value of the pressure gradient and the seepage velocity were analyzed during the test process. The nonlinear characteristics of the seepage test were revealed. In addition, variation laws of the absolute value of the pressure gradient with the sand volume fraction and the sand particle size were illustrated, which were related to the loss of pressure during the particle movement. The impacts of the sand volume fraction and the sand particle size on the equivalent fluidity and
β
-factor of non-Darcy flow were discussed and analyzed. It was determined that the local turbulence was the main reason for the change of nonlinear variation characteristics of seepage parameters.
The causes of greater energy loss for throttling in the fan and pump were analyzed, and the principle of frequency control in energy saving were analyzed on the basis of the similarity theory, too. To export the relationship between the power saving rate and flow, the relationship between the energy consumption of throttling regulation and flow were described. Comparison between frequency control and throttling regulation in changing the flow shows that motor frequency control applied in pump and fan is an efficient way to save power. It confirms that under meeting the similarity condition, the power saving rate of theoretical calculation is consistent with the measured data.
Researching the gas’s temperature change trend was important for the system design of spray tower in which the liquid and the gas was mixed and the heat was exchanged. In temperature measurement, it must be concerned that the test data contain impulse noise due to the internal complex environment of spray tower. In order to get the real and accurate data and to acquire temperature change characteristics, the thermocouple sensors were used to do multipoint temperature measurement in different experimental conditions. The method of extremum median filter was used to remove impulse noise of signal. The simulation was made with MATLAB. The analysis result shows that the method can remove impulse noise of temperature signal and get accurate temperature data.
The instability of water-sediment flow in fractures can easily induce water-sediment disasters. Therefore, it is of great significance for the prevention and control of water-sediment inrush to study the water-sediment two-phase flow in fractures. Based on the water-sediment two-phase flow theory, a model of the water-sediment two-phase flow system was established. The Ansys Fluent software was used to study the characteristics of the water-sediment two-phase flow in smooth and rough fractures. The spatial-temporal evolution laws of the water-sediment two-phase flow were studied; the results indicated that they did not change with time in the smooth fractured flow fields, while changing continuously with time in the rough fractured flow fields and in a dynamic steady state. The research results can provide references for the water-sediment two-phase flow in fractures and rock mass.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.