Testing of Large Scale Pool Fire of Technical Ethanol

Aim: The aim of this article is to determine the characteristics of a pool fire, including the temperatures and thermal radiation densities caused by it. Mappings of pool fires occurring in actual emergency events were conducted by performing large-scale polygon tests. Project and methods: Experimental study of pool fire of technical ethanol was carried out on a specially built test stand in the training area of the Training Centre in Pionki of the Regional Headquarters of the State Fire Service in Warsaw. The pool fire test stand consisted of a test tray, with a test chamber with the diameter of 300 cm, founded on a reinforced concrete slab. Using a developed measurement system with data acquisition that included measurement sensors mounted at defined locations relative to the fire, temperatures and thermal radiation densities were measured at various distances/locations relative to the fire. Metrological data such as air temperature, atmospheric pressure, humidity, wind direction and speed were monitored and recorded using the weather station. The height of the fire flame was measured by comparing it to racks set up nearby with marked scales of specific lengths. Results: A polygon stand that was built to study pool fires, equipped with a temperature and thermal radiation density measuring system with measuring sensors distributed in defined locations, is discussed. A study of a pool fire resulting from the combustion of dehydrated, fully contaminated ethanol was conducted. The study measured temperatures, thermal radiation densities, and flame heights. The average and maximum values of temperatures and thermal radiation densities during the steady-state combustion stage (i.e., phase II of the fire) were determined. Conclusions: Based on the presented results of temperature and thermal radiation density measurements at various distances/locations relative to the pool fire site, there was a significant effect of wind direction and speed on these values. Higher temperature and heat radiation density were recorded at the sensors on the leeward side than on the windward side. As the wind speed decreased, there was an increase in the temperature values recorded on the thermocouples located above the centre of the bottom of the tray test chamber due to the flame, which, when not blown away, was allowed to rise vertically upward and fully sweep the temperature sensors.

Over the years, various experimental studies have been carried out on the problem of the pool fires [1, 4-6], most often with the aim of developing or verifying mathematical models to estimate the consequences of failure. Experimental studies were carried out at different scales -from small laboratory to large field scale. A detailed understanding of the phenomenon of liquid combustion in spills has allowed the development of effective methods for estimating its effects, enabling the correct assessment of the risk of an accident associated with it. Based on the results obtained from the field tests, the researchers also verified already existing mathematical models describing the flame characteristics [7][8]. This allowed to determine their level of accuracy or validity in the light of an increasing number of results from experimental studies.

Field test stand for pool fires
The pool fire test stand (see Figure 1) consisted of, among other things, a test tray with supporting elements, which was founded on a reinforced concrete slab. The slab was made in such a way as to protect the soil, ground water and underground water from the negative effects of combustion products and extinguishing water during the test. A technical drawing of the test tray, with a test chamber with the diameter of 300 cm, is shown in Figure 2. The tray was made of materials resistant to testing factors, including heat radiation and temperature shocks.
Water was used to cool the tray, which was placed in a ringshaped chamber located around the test chamber. W ramach projektu pt. "Program do oceny ryzyka wystąpienia awarii w obiektach przemysłowych stwarzających zagrożenie poza swoim terenem" [9][10]         The field test stand prepared for pool fire testing of technical ethanol is shown in Figure 7. Temperature and thermal radiation density were measured using a developed measuring system with data acquisition, which included measuring sensors mounted in the defined locations relative to the fire (see Figure 3).  and 138 s were recorded (see Table 2). For further considerations, the wind direction is taken as the direction from which the wind is blowing. The wind diagram (wind programme, wind rose) is shown in Figure 3.
Source: Own elaboration. Źródło: Opracowanie własne.  At the lowest wind speed prevailing during the test, 0.1 m/s, there was an increase in the temperature values recorded at thermocouples T1, T2 and T3 (see Figure 9). This was caused by a flame that, when not blown out, could rise vertically upwards and fully sweep the temperature sensors located above the centre of the bottom of the tray test chamber.
During the experiment, the thermal radiation generated by the flame, which is one of the most important heat transport mechanisms in the fire environment, was also recorded [14]. The set up heat radiation density sensors monitored the immediate zone of influence, where the emitted heat could lead to changes in the fire situation and endanger people. The maximum values that were recorded (see Figure 13) on sensors P1 and P3 can cause pain after 15-20 s, burns after 30 s [14]. Analysing the graph, also in this case, a strong influence of the wind direction on the magnitude of the recorded thermal radiation density is noticeable. The