Figure 1 Schematic diagram of the cup burner system.
The schematic of the cup burner system is shown in Figure 1[1].
There are specific descriptions about the standard cup burner apparatus
in ISO-14520. Hence, this study referred to the standard and gave a
brief description here. The cup burner apparatus consists of the burner
nozzle, the chimney, and the glass cover. The inner and outer diameters
of the burner nozzle are 26 and 31 mm, respectively. The burner nozzle
is located in the internal center of the chimney. The bottom of the
burner is filled with 5mm and 7mm glass beads for uniform flow of
air/agent. The outermost layer is a glass cover. The height of glass
cover is 537 mm and the inside and outside of diameters are 83 mm and 89
mm, respectively. The fuel used in this study is methane (purity≥ 99.9
%) and the oxidizer is synthetic air (O2 20.9 %;
N2 79.1 %). This study chose R123 as the main study
object and R125 as the reference object. Temperature measurement is
mainly achieved by K-type thermocouple and paperless recorder. There
were five K-type thermocouples forming a ‘thermocouple tree’ and they
are set at 0 cm (the bottom of the flame), 5 cm, 10 cm, 15 cm, and 20 cm
respectively. The changes of temperature at different flame heights were
measured in real time, and they were also displayed in real time by the
paperless recorder, and the temperature data were collected every 1
second. Digital and high-speed cameras separately recorded the entire
flame burning to extinguishing process.
Prior to the experiment, the mixing chamber and pipes were heated to 80
°C with heating bands to ensure that the R123 evaporated during
delivery. In the experiment, the air flow rate was kept at 40 L/min and
the flow rate of methane was adjusted to 240 mL/min, which were both
controlled by the flow meters, consequently keeping the flame at 8 cm.
After the stable burning of methane flame for at least 60 s, the agents
were transported to the mixing chamber with air, then flowing into the
cup burner. The amount in each increment of the flowmeter readings was
0.2 L/min, growing until flame extinguishment occurred. At the same
time, in order to ensure that the agent and air reached the burner
proportionally, the interval between each adjustment was at least 20 s.
And finally, the experiment was repeated 3 times to ensure the
reproducibility of the results. To investigate the extinguishing effect
of R123, R125 was chosen to do the same experimental procedures as the
reference object, and the experiments were also repeated for several
times.