Search

To verify the accuracy of the calculation method based on the indentation-pressure drop method to quickly determine the coal permeability coefficient, this paper simulated the gas pressure change curve of the borehole based on the COMSOL numerical simulation software. The pressure change curve obtained by setting different air permeability coefficients in the simulation software, combined with the rapid determination of the coal permeability coefficient calculation method to calculate the coal permeability coefficient, and the error between the simulated value and the calculated value is compared. The results show that the relative error between the simulated value and the calculated value is -23%~+45%, and the error between the calculated result and the simulated parameter is small, which verifies that the method of quickly determining the coal permeability coefficient based on the indentation-pressure drop method is correct and feasible. The simulation results show that the calculation results of the pressure curve obtained by the short-term simulation and the long-term simulation are basically the same. Therefore, the short-term measurement results can also be used to calculate the coal seam permeability coefficient. The rapid determination of the coal seam permeability coefficient is theoretically feasible.

This paper discusses a new method for optimization of mine ventilation system. The method is based on criteria as follows: (1) minimize the size of each regulator; (2) minimize the number of regulators; and (3) minimize the total power consumption of fans. Based on this theory, the optimization problem of the ventilation system is classified as optimization of mine ventilation network and calculation of operating points of fans. Furthermore an algorithm that determines the economical operating point of fans while calculating the optimum controls of ventilation network is proposed. The main features of this method are that it does not require the analysis of a large-scale nonlinear programming problem, and the optimal solution can be obtained by means of existing programs for mine ventilation network analysis.

First, this paper describes the overview of the data relevant to the mine ventilation such as the total volume of ventilation air, the number of fans, the size of ventilation network, etc. and the procedures of calculation of the airflow distribution which are actually employed in various mines. Then statistical analysis of the ventilation networks are given. As a result it is found that too small friction factors or too small ventilation resistances are being used in almost all network analyses. This may be one of the major reasons for the inaccuracy of the ventilation network analyses and therefore particular attention should be given to the fact when ventilation network data are compiled. The calculation time required for an airflow distribution analysis depends not only on the method of calculation for a node pressure but also on the method how to consider a fan characteristics. The paper also describes the new method for the calculation of the airflow rate by the fan, which enhances the calculation speed and the stability of the analysis. Finally, an improved node potential method for calculating the pressure of two nodes at both ends of an airway simultaneously is proposed. The calculation time is reduced to 55 % on the average through these improvements.

There are many ventilation networks utilizing multiple fan system. Not only the airflow distribution analysis but also the optimization of such ventilation networks are affected by the interaction of these fans. This paper describes the influence of the interaction of fans on the optimization of the network.Firstly, fundamental procedures for the optimization of multiple fan network are explained. They are similar to those for a single fan network, the interaction of the fans interferes the convergence of the analysis to the optimum conditions depending on the configurations of the network and fans. The economical conditions of such a procedures will be deduced theoretically.An improved method for optimization of multiple fan network system in various condition is developed on the basis of the theory. Finally, criteria for checking the optimization of a multiple fan ventilation network is proposed and several examples of the application will be shown.

This paper describes the optimum control of a ventilation network considering the total cost of the ventilation. Firstly, a basic theory to minimize the total cost of the ventilation is proposed. It leads to a conclusion, that is, the resistance changes required for the control of the network should be minimize to minimize the total cost. Then a practical method to calculate the resistance changes developed by the theory is described. Finally, some examples about the optimum control of a ventilation network are shown. The main features of the method are as follows;(1) The specified factor of the control model is the total cost of the ventilation that consists of the energy cost for the ventilation and the construction cost for the control.(2) The required air quantity for a roadway is not a fixed value but a value within some range.(3) The combination of the roadways to be controled can be selected regardless of the cotree of the ventilation network.