Design And Research Of Anti-Freezing Air Door For Mine Ventilation System

Ventilation system is the key to ensure safe production in mines.Any mine must keep wind flowing in the corresponding ventilation circuit at all times.Even when the ventilation system needs to be switched over due to malfunction or regular maintenance,the time for interrupting the ventilation cannot exceed 10 minutes.It is best to achieve the non-stop switching of the main fan.The switching process of the main fan is realized by the cooperation of the opening and closing of multiple air doors.The reasonable design of multiple air door structures can not only adjust the direction and air volume of the air flowing into each working face of the shaft,but also realize the non-stop air switching function of the main fan.However,the actual production often occurs due to the failure of the air door,especially in the northern winter.It is very easy to cause failures or secondary accidents caused by the icing of the air door,which brings huge hidden dangers to coal mine safety production.In order to solve the above problems,this paper proposes a design scheme of the anti-freezing air door for the main ventilation system of the mine,and uses the heat flow coupled numerical simulation method to explore its internal flow and heat transfer characteristics.First and foremost,the faults of the air door are summarized and classified to form a typical fault database.The design work of two heating structures with single outlet and multiple outlets for the anti-freezing air door as well as the transmission device and the heating device is completed.The Fluent software is used to numerically simulate the flow and heat transfer performance inside the air door under the single-exit and multi-exit schemes,and the better scheme is selected.The numerical simulation results show that the heat transfer performance of each part of the air door panel is better when the structure is single exit.Compared with the multi-exit structure,the area-weighted average temperature of the middle section of the air door panel in the single-exit structure is increased by 1.04%.Secondly,in order to improve the heat transfer performance of the air door heating device and reduce the pressure loss of the gas flowing through the heating device,the structure is optimized by the L₉(3⁴)orthogonal design method combined with numerical simulation.The change curve of centrifugal fan pressure with flow rate is measured through experiments and use as the boundary condition of numerical simulation.The length and angle of the first and second deflectors of the heating device are used as the influencing factors,and the temperature rise and pressure drop are used as the evaluation indicators.Then the heating equipment models for nine design schemes are simulated by Fluent,and through intuitive analysis and range analysis to get the best plan.Finally,the internal flow and heat transfer characteristics of the heating device before and after optimization are compared.The research shows that the angle of the first stage deflector has the most significant effect on temperature rise and pressure drop.In the optimal structure,the angles of the first and second baffles are 11°and 27°,and the lengths are 130 mm and 110 mm,respectively.Compared with before optimization,the temperature rise is increased by 2.74%and the pressure loss is reduced by 9.1%.After optimization,the vortex inside the heating equipment is reduced,the turbulent flow energy is reduced,and the internal flow and heat transfer performance are better.Once again,In order to optimize the internal structure of the air door and improve its heat transfer performance,the optimized heating device and the three kinds of circulation path air doors are numerically simulated by heat flow coupling.Then the optimal structure is determined,and the heat transfer characteristics of the air door under the structure under variable flow conditions are analyzed.The research shows that under three types of circulation path structures,such as no deflector inside the air door,horizontal arrangement of the deflectors and vertical arrangement,the heat transfer performance of the hot air flow inside the air door is the best when it is longitudinally arranged.When longitudinally arranged,the area-weighted average temperature of the middle section of the air door reached 317.61 K,which increased by 3.91%and 0.20%respectively compared with the case without the deflector and the deflector in the lateral arrangement.Under variable flow conditions,as the flow rate increases,the speed of the hot air flow inside the air door increases,the turbulent flow energy increases,the vortex becomes more turbulent,and the temperature of each part of the air door panel gradually decreases.Eventually,a performance test platform for the air door heating device is built,and the heat transfer performance of the heating device under variable flow conditions is measured by experiments.Then the experiment and simulation results are compared to verify the rationality of the numerical simulation.The two NO 36 anti-freezing air doors operate normally and have a good seal,which meets the design requirements of D-LD2000.The anti-freezing air door is connected to the ventilation system,and the task of non-stop wind switching is completed within 10 minutes,reaching the design goal.