For a long time, how to objectively and scientifically evaluate the protective performance of special clothing such as military uniforms, fire-resistant clothing, fire-fighting clothing, flame-retardant and high-temperature work clothing, has been a problem that plagued the industry. At present, this evaluation can generally only be made based on the burning or flame retardant experiments of clothing fabrics, and cannot reflect the actual effects of clothing composition and human body action, and may even result in insufficient or excessive protection of the overall clothing in the actual working environment. A well-known company outside the United Nations of Qinsun has developed a combustion dummy system, which can accurately sense high-temperature heat flow in different active postures, accurately predict the degree of burns on the skin of the body, and a combustion simulation environment experiment that simulates a high-risk environment in a fire field. room.
EN ISO 11612, EN ISO 11611, ISO 13506, EN469:2005, etc. are all applicable to this test system.
The burning dummy test system is used to test the overall thermal protection performance of protective clothing. The complete combustion dummy system consists of a combustion chamber, combustion dummy and gas supply control system.
Burning dummy and design principle:
The system is mainly composed of a burning dummy, a data acquisition device, a flame generation and control device, a skin heat transfer model and a burn assessment model, and a centralized control system and application software platform. The design principle is to test the surface temperature of the dummy by simulating the thermal exposure process of the wearing human body in the burning flame, and predict the possible second-degree and third-degree burns and the percentage of the total burn area. The flame retardant protection performance is worse.
The flame duration of the burning dummy body when used for clothing testing is generally 4 s. The surface of the dummy may need to withstand a burning flame up to 300 ℃. Therefore, the material of the dummy body must have a short-term burning flame above 300 ℃. Good thermal stability, can withstand harsh fire environment; the response of the sensor on the surface of the dummy to the burning flame should be close to the response of the human skin to the burning flame; the data acquisition and processing device can quickly collect the data of the sensor on the surface of the dummy.
Burning dummy body:
According to the above design requirements, through comparative analysis of the physical properties of high temperature resistant materials, polyimide with the highest temperature resistance grade, the best mechanical properties, dielectric properties, and corrosion resistance is selected as the main body material of the combustion dummy. According to the appearance characteristics of the model, the dummy body model is manufactured according to the following process: synthetic polyimide → curing resin material → making molds for various anatomical sections of the human body and high-temperature molding → vacuum curing → surface treatment.
Dummy surface thermal sensor:
The function of the thermal sensor on the surface of the dummy skin is to perceive the degree of heat exposure of the human skin under the fire environment, and to predict the degree of burns that may occur on the skin accordingly. The thermal sensors used abroad mainly include TPP copper sheet heat flow meter sensors, thermally insulated copper sheet sensors and embedded thermocouple sensors. Among the three types of sensors, the thermally insulated copper sensor is the most reliable thermal sensor.
Experiments show that:
The adiabatic copper sheet sensor is similar to the TPP copper sheet heat flow meter sensor, with stable readings, rapid response, wide range, and good repeatability. At the same time, the volume of the sensor is smaller than the TPP sensor, and the space and mass are much smaller than the TPP copper sheet heat flow meter. In a high-heat environment, the average response speed of embedded thermocouple sensors is slower than that of thermally insulated copper sheet sensors. To this end, the research team developed a thermally insulated copper sheet sensor with a diameter of 1 cm and a thickness of 0.16 cm. Using a brazing process, the copper sheet was connected to a K-type thermocouple with a wire diameter of 0.2 mm, and the measurement accuracy reached 0.2 ℃.
Taking into consideration factors such as dummy area, data collection, burn evaluation and calculation, 120 thermally insulated copper sheet sensors are evenly arranged on the dummy surface. When installing the sensor, use a milling cutter to drill holes according to the diameter and depth of the copper sheet to ensure that the surface of the sensor and its surroundings are closely matched with the dummy body, and the sensor is evenly distributed.
Experiment process of burning dummy:
A total of 6 groups of 12 flamethrowers are installed around the burning dummy. Each flamethrower can provide 84 kilowatts/square meter (kW/m2) heat flow within 2 to 3 seconds, which vividly simulates the deflagration flash in the critical state of the real fire field. fire. In the experiment, all the flamethrowers were ignited at once, and 12 fire dragons rose into the air. The burning dummy wearing fireproof clothing was instantly swallowed and submerged by flames as high as 3 meters. In order to study the characteristics of human emergency response in a realistic fire scene, the research experts also suspended the burning dummy to "move" in the fire scene, and automatically adjust the orientation and orientation of the dummy at different speeds. At the end of the experiment, by analyzing the data output by each sensor on the dummy and calculating the heat flow, the burn level, the total burn area, and the time that constitutes the second and third level burns on the skin surface where each sensor is located can be accurately reported. .
The system fully meets the relevant technical indicators of ISO13506, ASTMF1930 and other combustion dummy system evaluations. The body size of the dummy adopts the Chinese adult male standard body shape, and 135 heat flow sensors are set up all over the body, covering various parts such as the torso, head, hands, and feet. It can be used for the evaluation of thermal protective clothing, and can also meet the needs of the evaluation of a complete set of thermal protective equipment such as helmets, gloves, and fire boots; in addition, the burning dummy is also equipped with joints such as shoulders, elbows, hips, knees and ankles, as well as rotation, The sliding system can simulate various postures and activity states of the human body.