5
in airflow contours near the PAPR inlet, which is most
likely due to the steep gradients in the flow field near the
PAPR. Using results from the simulations, we plotted
the contours of velocity magnitude to identify the areas
where particles might concentrate around the miner’s
head. Results are shown in Figures 6–8. The area at the
back of the head shows a low-velocity profile in every case.
Therefore, this region is expected to trap particles locally
that will be captured by the PAPR. The effectiveness of the
PAPR becomes progressively weaker as the ambient airflow
speed is increased.
TRANSIENT-STATE SIMULATIONS
For the transient-state simulations, the inlet velocity was
lowered to 0.01 m/s, and an outlet airflow of 170 L/min
was added to the back of the head to capture the parti-
cles. This airflow is representative of the flow through a
typical Versaflow PAPR. Particles were injected at the five
probe points at a rate of 0.0013 kg/s. This corresponds to
a concentration of 4.08 mg/m3 in our domain, which is
the continuous miner operator’s exposure as obtained from
the literature [16]. Many graphs were plotted for each par-
ticle size. First, the velocities at the probe points were used
to monitor the state of the flow. Figure 9 shows one such
graph where airflow velocity is plotted at those probe points
for PM10. Similar graphs were plotted for other particle
sizes. The velocity magnitude remained the same for all par-
ticle sizes. This indicates that the airflow momentum domi-
nates the particulate transportation despite a bi-directional
coupling.
Finally, the mass flows were plotted to understand the
behavior of the particles under these specific conditions.
Figure 10–13 represent the mass flow rates of injected par-
ticles and the escaped particles through the control sur-
face at the back of the PAPR. As particles were injected
at specific points around the PAPR, it was expected that
the escaped particles graph would show different waves of
particles escaping the domain, meaning that the particles
were being carried by the airflow from the different injec-
tion points. Integrating the graph, it is possible to obtain
the mass balance after the first minute of operation. This is
shown in Table 7.
Figure 5. Normalized wall distance
Figure 6. Contours of velocity magnitude on a plane
through the PAPR for an inlet velocity of 1.0 m/s
Figure 7. Contours of velocity magnitude for an inlet
velocity of 2.0 m/s
Figure 8. Contours of velocity magnitude for an inlet
velocity of 3.0 m/s
in airflow contours near the PAPR inlet, which is most
likely due to the steep gradients in the flow field near the
PAPR. Using results from the simulations, we plotted
the contours of velocity magnitude to identify the areas
where particles might concentrate around the miner’s
head. Results are shown in Figures 6–8. The area at the
back of the head shows a low-velocity profile in every case.
Therefore, this region is expected to trap particles locally
that will be captured by the PAPR. The effectiveness of the
PAPR becomes progressively weaker as the ambient airflow
speed is increased.
TRANSIENT-STATE SIMULATIONS
For the transient-state simulations, the inlet velocity was
lowered to 0.01 m/s, and an outlet airflow of 170 L/min
was added to the back of the head to capture the parti-
cles. This airflow is representative of the flow through a
typical Versaflow PAPR. Particles were injected at the five
probe points at a rate of 0.0013 kg/s. This corresponds to
a concentration of 4.08 mg/m3 in our domain, which is
the continuous miner operator’s exposure as obtained from
the literature [16]. Many graphs were plotted for each par-
ticle size. First, the velocities at the probe points were used
to monitor the state of the flow. Figure 9 shows one such
graph where airflow velocity is plotted at those probe points
for PM10. Similar graphs were plotted for other particle
sizes. The velocity magnitude remained the same for all par-
ticle sizes. This indicates that the airflow momentum domi-
nates the particulate transportation despite a bi-directional
coupling.
Finally, the mass flows were plotted to understand the
behavior of the particles under these specific conditions.
Figure 10–13 represent the mass flow rates of injected par-
ticles and the escaped particles through the control sur-
face at the back of the PAPR. As particles were injected
at specific points around the PAPR, it was expected that
the escaped particles graph would show different waves of
particles escaping the domain, meaning that the particles
were being carried by the airflow from the different injec-
tion points. Integrating the graph, it is possible to obtain
the mass balance after the first minute of operation. This is
shown in Table 7.
Figure 5. Normalized wall distance
Figure 6. Contours of velocity magnitude on a plane
through the PAPR for an inlet velocity of 1.0 m/s
Figure 7. Contours of velocity magnitude for an inlet
velocity of 2.0 m/s
Figure 8. Contours of velocity magnitude for an inlet
velocity of 3.0 m/s