Equipment Design And Experimental Study Of Liquid Nitrogen Fire Fighting Platform

The occurrence of fires can cause significant casualties and huge property damage.The protection of equipment for critical occasions,such as computers,cabinets for documents,and first aid for injured people in the fire is an important issue in the fire protection process.In this paper,a liquid nitrogen fire-fighting platform for indoor " on-site fire extinguishing,on-site protection" is designed for this problem.It consists of three units:liquid nitrogen fire extinguishing unit,curing agent fireproof unit and oxygen supply mask emergency unit.In this paper,the overall design of the liquid nitrogen fire protection platform was first carried out.The platform is loaded on a tracked wheeled robot platform.Liquid nitrogen and solidifying agent are sprayed through nozzles controlled by the root motor.The oxygen supply mask is operated by a flexible robot.The curing agent on the platform is stored in a cylinder,the liquid nitrogen is stored in a liquid nitrogen dewar,and the oxygen mask is connected to the oxygen candle by an insulated breathing mask.The system does not need a pump,the pressure is maintained by liquid nitrogen dewar,and the structure is simple and convenient to control.In this paper,the following research is carried out by combining experimental and numerical simulations:(1)There are many problems in the selection of the working point of the liquid nitrogen injection fire extinguishing unit.Excessive design pressure will cause the total weight of the equipment to exceed the standard,and the robot platform is difficult to carry;the choice of nozzle diameter and structure will affect the injection effect.Through experimental measurements,it is found that the total weight of the equipment is reasonable when the initial pressure is 0.8 MPa.The linear jet 2.2 mm B-type nozzle can achieve the best liquid nitrogen injection effect.When the equipment pressure is 0.3-0.6 MPa,the liquid nitrogen stable injection distance is 5 m.The liquid nitrogen injection distance is independent of the equipment pressure.However,when the pressure is lower than 0.3 MPa,the liquid nitrogen injection cannot be maintained.(2)Since the details of the liquid nitrogen injection state are difficult to directly observe,the process is numerically simulated by using a VOF(Volume Of Fluid)model.It is known from the results that the liquid nitrogen nozzle structure has a great influence on the injection effect.In addition,liquid nitrogen does not form a liquid column during the spraying process,but rapidly ruptures and flies forward in the form of small droplets,and the small droplets in contact with the air gradually vaporize and lower the ambient temperature,eventually evaporating.(3)The strong convection environment in the fire will affect the spraying of the curing agent.In this paper,the linear jet is used to spray the curing agent.It has been experimentally verified that the best curing agent spray effect can be obtained when the initial pressure is 0.8 MPa using the SS5 nozzle.The linear jet state of the curing agent is relatively stable,and the curing agent sprayed on the target can achieve stable adhesion and form a rugged wrapping layer.(4)The smoke in the fire will cause fatal poisoning to the injured in the fire.This paper designed and verified a set of electric starting oxygen mask that can achieve stable oxygen supply for 10 minutes.Through the measurement of oxygen production flow rate,impurity concentration and total amount of oxygen,its performance meets the requirements of GB 24502-2009 "Chemical Oxygen Self-rescuer for Coal Mine" for emergency oxygen supply.The oxygen supply mask is electrically activated,and the overall weight of the chemical oxygen is light.These excellent properties can also achieve a good match of the unit to the robot platform.In general,the liquid nitrogen fire protection platform can meet the design requirements,the structure is simple,and the control is convenient.Each functional unit is arranged reasonably and does not interfere with each other.Through the combination with the robot chassis,the function of "on-site fire extinguishing,on-site protection" can be realized.