PIV Experimental Study On Flow Field Of Long Pressure Short Suction Heading Face

The mismeasurement of underground wind speed and wind pressure is one of the key scientific and technical problems of mine intelligent ventilation.Both the learning and training of artificial intelligence model and the early warning decision depend on a large number of effective ventilation data.From the perspective of turbulence,avoid the throttle switch,cage hoisting,car running and trackless vehicles under the condition of disturbance factors,such as a large number of laser doppler velocimeter(LDA),hot wire anemometer(CTA)and particle image velocimetry(PIV)the experimental results show that the downhole turbulent fluctuation characteristics of wind flow is the main reason for the uncertainty,It is also the key factor for the breakthrough of wind measurement technology.The jet air supply used in tunneling tunnel is restricted and influenced by the tunnel wall,forming the wall-attached jet.The wall-attached jet with displacement and mixing double weight functions plays a key role in the migration and diffusion of gas and dust in the tunnel.However,the distribution of airflow field is more complicated due to the stronger turbulent characteristics of the wall-attached jet.PIV has strong applicability for flow field measurement,which can realize the transient measurement of the whole flow field and obtain the time-average flow field from multiple groups of transient flow fields.In this thesis,an experimental model of long pressure and short suction ventilation roadway was designed based on the similarity theory.PIV was used to conduct non-contact measurement of the air flow field of the experimental model,and CFD software was used to analyze the flow field under the same conditions.The CFD software was used to analyze the experimental models of various sizes,and it was concluded that the critical wind speed of each size model increased with the decrease of the model.Considering the applicability of laboratory conditions and experimental equipment,the optimal similarity ratio of this experimental model was determined as 15:1.PIV was used to measure the two-dimensional flow field of the experimental model,and the flow field law of long pressure short suction-forward pressure and back suction ventilation was obtained.The jet is discharged from the outlet of the press-in air duct and diffuses when moving to the end face of the head face.Most of the air flow flows along the end face of the head face to form the wall area of the impact jet,and a vortex is generated at the head face.The return air flow and the air flow at the back of the roadway flow to the inlet of the suction air duct,forming a wind curtain.When the position of the suction air duct changes,the flow field at the head face changes little,but the wind speed of the return air duct decreases with the backward movement of the suction air duct.When the distance between the suction duct inlet and the head is greater than 4.5√S,the wind speed of the return air flow is reduced to about 0.5m/s.At this time,the return air flow not only has a long flow distance,but also the flow state is easily affected.The flow field and wind speed distribution at the headface are greatly affected when the position of the injection air duct changes.When the distance between the outlet of the press-in air duct and the head face is greater than 3√S,part of the jet flow rotates before moving to the working face,forming a large eddy current area,the jet velocity at the end face of the head face is only about 0.5m/s.The change of pressure and suction wind speed has little influence on the flow field at the head.Under the three conditions of pressure wind speed < suction wind speed,pressure wind speed > suction wind speed and pressure wind speed = suction wind speed,the location and size of vortex zone remain unchanged basically,and only the airflow direction behind the roadway will be changed.CFD software was used for numerical simulation of the experimental model,and the influence of air duct position on 2D and 3D flow field was obtained.By comparing the 2D flow field of PIV experiment and CFD simulation,the variation law was basically consistent.By analyzing the three-dimensional flow field,it is concluded that the eddy current exists not only in a certain plane,but also near the side wall of the roadway and the wall of the air duct.The thesis has 40 pictures,3 tables,and 77 references.