Biomethanewas successfully substituted in two of the most popular
domestic Thai stoves, the swirl and the radial burner. A supply pressure
of 0.2 bar was found to be optimal. This is a fourfold increase over the
standard pressure which LPG is normally supplied, 0.05 bar. The nozzle
through which the gaseous fuel flows through needed to be enlarged.
The optimal nozzle inner diameter was found to be 1.0 mm and the
outer diameter was 1.8 mm as shown in Table 3. These diameters
were also predicted from analyzing the exit nozzle velocity and
matching the velocities for biomethane and LPG. A similar exit velocity
will entrain a similar amount of combustion air. For comparison the
inner and outer nozzle diameters for LPG combustion were 0.6 mm
and 0.9mm. A mapwas produced, as shown in Fig. 12, containing information
about the fuel supply pressure and nozzle sizes that produced a
stable flame at all stove operating conditions.
At the optimal condition, supply pressure and nozzle size, the performance
of each stove was assessed. The fuel flow rate, energy input,
energy output and the flame temperature were measured. The data
for these experiments are displayed in Table 3, Fig. 12 and Table 4
respectively. The conclusions for the biomethane are that its flame temperature
is between 22 °C and 92 °C lower, and have higher efficiencies
and slightly longer heating times depending on the exact setting.