Экспериментальное исследование температурных следов капель воды, водных массивов и аэрозольных потоков, движущихся через высокотемпературные продукты сгорания

Abstract

The experimental investigations of temperature, varying in a trace of water droplets, water flow masses and aerosol flows, moving through high-temperature combustion products, were conducted. The temperature values of vapor-gas mixture in an area, corresponding to the trace of water droplets, moving through high-temperature combustion products (initial temperature values were 450-950 K) were measured by quick-response thermocouples (time of thermal delay was less than 1 sec). The objects of investigations were aerosol flows with droplet sizes, equal to R d » 0.04÷0.40 mm, and droplet concentration, equal to g d » 3·10 -5 ÷12·10 -5 m 3 of droplets/m 3 of gas; single droplets with R d » 1.5÷2.5 mm, and significant water flow masses with characteristic size of 22-30 mm. Application of the quick-response thermocouples allowed defining the ranges of maximal reduction of gaseous medium temperature T g in a trace of extinguishing liquid according to a group of factors, such as a method of supplying of water into the combustion zone, characteristic size of the elements of liquid flow R d , droplet concentration in a water flow g d , temperature of the combustion products T g . The variation of combustion product temperature in a trace of motion of atomized flow, droplets and liquid flow masses was determined in the analysis of temperature trends, ranged from 15 K to 140 K. The values of preservation time t of low temperature of vapor-gas mixture in a trace of droplet flow, single droplets and significant liquid flow masses were determined relative to initial gas temperature: t » 4÷28 sec. It was experimentally defined that maximum values of time t correspond to supplying the atomized water, with characteristic sizes of elements, equal to R d » 0.15÷0.30 mm, and concentration, equal to g d » 3·10 -5 ÷12·10 -5 m 3 of droplets/m 3 of gas, into the standardized fire. The conditions when the characteristics of temperature and concentration traces have significant influence on processes of evaporation and heat exchange between gases and moving liquid (with accumulation of liquid energy) were determined. The ascertained experimental data prove the earlier made theoretical hypothesis about sufficiently long periods of preservation the temperature traces of water droplets, even if they are small. The obtained experimental information become the basis for developing the method of the effective reduction of fire temperature (flame and combustion products) in the technologies of polydisperse aerosol fire extinguishing.