# Measurement of Instantaneous Mass Flow Rate of Polypropylene Gasification Products in Airflow
## 4 Typical Test Fires  
### Test Fires with Hydrogen-Assisted Ignition  
Figure 9 shows the typical time histories of gas pressure and temperature in test fires without and with PP sample combustion. Air is supplied to the GG from facility storage vessels in 0.5 s after triggering the data acquisition system. Hydrogen is supplied to the GG during 0.5 s (from 1.5 to 2.0 s after triggering the data acquisition system). The spark plug is then turned on for 0.3 s followed by hydrogen ignition. It was experimentally established that reliable ignition of the PP sample in this design of the experimental setup occurred when the air-to-hydrogen equivalence ratio, \(\alpha\), in the burning mixture upstream of the PP sample was in the range of 1.4-1.6, i.e., the mixture was fuel lean. Therefore, other values of \(\alpha\) were not considered. The total hydrogen consumption during ignition stage is 2.2-2.4 g with the rate of consumption of 4.2-4.6 g/s. The air-to-hydrogen equivalence ratio in the burning mixture upstream of the PP sample is \(\alpha\approx\) 1.4-1.6, i.e., the mixture is fuel lean. Due to hydrogen combustion, the temperature of the passing air increases sharply and provides PP sample ignition. After cutting hydrogen supply, cold air at ambient temperature (290 K) continues flowing into the GG, while the combustion of the PP pyrolysis products continues in the cold air flow for about 3 s. Thus, the mass flow rate of gasification products is many measured after ignition, when hydrogen is not supplied and its influence does not need to be taken into account.  
Test fire #1 in Figure 9 is a reference experiment without hydrogen ignition (spark plug is purposefully not activated). In this test fire, only a slight pressure rise caused by hydrogen supply is detected, while the temperatures at the PP sample inlet and outlet remain constant (ambient temperature). The sample mass is also not changed in this test fire. In test fires #2 and #3, the activation of spark plug results in hydrogen combustion followed by ignition and self-sustaining combustion of the PP sample. As seen, hydrogen assisted ignition of the PP sample results in a sharp pressure rise both at the sample inlet and outlet by a factor of 1.5-2. During ignition, the temperature at sample inlet and outlet increases to 1600-1800 K and 800-1000 K, respectively. If hydrogen consumption during ignition is taken equal to a mean value of 2.3 g (as discussed earlier in the paper), then combustion of this amount of hydrogen would release an energy of 120,000,000 \(\times\) 0.0023 = 276,000 J. The air consumption during ignition is \(\sim\)120 g. With the full use of the heat of hydrogen combustion, the air should have been heated to temperature 276,000/1000/0.120 + 300 = 2600 K. However, the actual temperature of the heated air at the sample inlet is  
Figure 8: Calculated time histories of total gas mass flow rates (**a**) and mass flow rate of gasification products (**b**) for test fire #9.  
below 1800 K. This means that the heat loss to the GG walls upstream of the PP sample is about 45%. After termination of hydrogen supply, the gas temperature at the sample inlet is seen to drop to 290 K, whereas the gas temperature at the sample outlet remains virtually constant at 1000-1100 K. This indicates that PP gasification products react with air leading to additional heat release.