FEATURES OF FIRE IN ELECTRIC VEHICLES ON HYDROGEN FUEL CELLS

Abstract

The purpose of the study is to reveal the characteristics of combustion and hazards arising from fires and traffic accidents involving FCEVs, which will create the basis for new approaches to responding to such events, as well as safe working conditions for rescuers. Description of the material. In general, the fire hazards associated with the use of FCEVs can be divided into the hazards associated with accidental hydrogen leakage and electric shock. Hazards associated with hydrogen arise from the depressurization of mains, which leads to the accidental release of hydrogen into the environment. The release of hydrogen can be long-term or instantaneous as a result of an explosion. Let's analyze the hydrogen supply system used in the FCEV. In general, it can be divided into the hydrogen storage subsystem, the supply subsystem to the fuel cell, and the fuel cell subsystem itself. The hydrogen supply subsystem to the fuel cell carries a greater fire hazard than the fuel cell subsystem. When the line is depressurized, the mechanism for covering the supply of hydrogen from the tank is activated, and the leak stops. However, in the event of ignition, the hydrogen contained in the lines will be sufficient to become a source of ignition for other materials of the vehicle. The hydrogen storage system carries the greatest fire hazard. To prevent an explosion due to heating of a hydrogen cylinder, a pressure valve is used, which is triggered by a thermal sensor when the temperature exceeds 90 ºС. Accidental handling of hydrogen can be accompanied by combustion. And with a faulty attitude valve, the worst situation from the point of view of fire danger can occur - an explosion. Usually, the pressure release valve is placed under the bottom of the car perpendicularly down, or at an angle of 45º. With a hole diameter of 4.2 mm and a hydrogen pressure of 70 MPa, the length of the flame torch when hydrogen leaks in the direction perpendicular to the surface of the earth will be 6.4 m when it leaks at an angle of 45º - 8.8 m, and under the condition of unobstructed combustion, i.e. the car overturned - 10.2 m. When the diameter of the opening increases, the length of the flame torch increases. The heat flow, which is formed due to the burning of hydrogen coming out of the car tank, can be 20 kW/m2 or more at a distance of 2-3 meters from the point of emission. With a heat flow of 1.6 kW/m2, during long-term exposure, there are no painful effects. When the heat flow increases to 4-5 kW/m2, a person who has no means of protection will get a 1st degree burn in 20 seconds; under the action of a heat flow of 9.5 kW/m2, a 2nd degree burn is formed after 20 seconds; 12.5-15 kW/m2 of heat radiation causes a 3rd degree burn. The most dangerous event that can happen for safety reasons is an explosion of a hydrogen tank. Scientists Koshkarov and Molkov investigated the dangerous distances due to the explosion of a hydrogen cylinder. Therefore, in the case of an explosion of a hydrogen cylinder with a volume of 100 l at a pressure of 70 MPa, lethal consequences occur at a distance of up to 8 m, and the zone of severe and medium injuries reaches up to 28 m. The safe distance for such a case is more than 100 m. It is obvious that from the increase pressure and volume of the balloon and such distance increases. Keywords: electric vehicle, hydrogen fuel cell, fire hazard of electric vehicles.