4:00 PM - 4:15 PM
[SVC27-08] Fundamental study on free-settling particles ingested from downward air inlet
Keywords:Volcanic ash, Air intake facility, Particle ingestion, Numerical analysis
Gas turbines (GTs) and diesel generators (DGs) need intake air for fuel combustion, and thus, may ingest volcanic ash particles during ash-fall events produced by volcanic eruptions. Their vulnerability assessment is important, especially for emergency power generators installed at important facilities. Ingested volcanic ash particles may cause clogging of filters for the air intake system of power generators installed in the upstream of compressors, and may damage compressor blades, leading to the shutdown of GTs and DGs. Volcanic ash particles are larger and heavier than particulate matters (PMs), so they fall faster and have more inertia. Trajectory of volcanic ash particles near the air intake facility is determined by their physical properties, and are different from PMs that follows the air flow. To quantify particle ingestions by air intake, experiments and numerical analysis were conducted by settling particles from the ceiling into a chamber equipped with an air inlet with a downward opening.
The experimental equipment consists of a chamber measuring W4.5m x D4.5m x H5.3m, an air intake duct, and a particle feeding system. A suction fan is installed downstream of the duct, and air is sucked into an inlet (W0.24m x D0.24m) installed at a height of 1m in the center of the chamber. A feeder whose feeding rate can be controlled is used as the particle feeding system, and the test particles are allowed to freely settle into the chamber through a needle. The location of this needle was moved to change the horizontal distance to the air inlet. The test particles used were 50 μm spherical glass beads and 70 μm spherical resin beads. The terminal velocities of both particles are comparable. In the experiment, the test particles were allowed to settle at 1 g/min after the average cross-sectional wind velocity at the inlet stabilized at 5 m/s. Some of the settled particles are ingested into the air intake duct and collected by a filter, and the other particles fall onto the floor of the chamber. The ingestion mass ratio, defined as the ratio of the ingestion mass to the feed mass of the test particles, was measured for the distance from the inlet.
Large eddy simulations were performed with OpenFoam 8. The multiphase particle-in-cell method with two-way coupling was used to analyze the behavior of solid particles within a fluid flow. After the fully developed flow was obtained in the computational domain, spherical particles were injected from the top of the domain with the same size, density and feeding rate as the experiments. The ingestion mass ratio was calculated for the flow field after 30s, which is long enough after the particles were injected.
Both experimental results and analysis results confirmed that the ingestion mass ratios of both test particles decreased as the distance from the air inlet increased. It was confirmed that the ingestion mass ratios obtained from the analysis were approximately the same as the ratios obtained in the experiments, although there was some difference. Therefore, it is thought that this analysis method can estimate the ingestion of spherical particles.
Comparing the experimental results of the ingestion mass ratios of two types of test particles with similar terminal velocities, the results were almost the same, although the glass beads with smaller particle diameters tended to have higher ingestion mass ratios. The analysis showed almost no difference between the two test particles. This suggests that particles with similar terminal velocities have similar ingestion mass ratios. To establish the method to estimate the amount of volcanic ash ingestion based on its terminal velocity, experiments for particles with various sizes and shapes will be conducted.
The experimental equipment consists of a chamber measuring W4.5m x D4.5m x H5.3m, an air intake duct, and a particle feeding system. A suction fan is installed downstream of the duct, and air is sucked into an inlet (W0.24m x D0.24m) installed at a height of 1m in the center of the chamber. A feeder whose feeding rate can be controlled is used as the particle feeding system, and the test particles are allowed to freely settle into the chamber through a needle. The location of this needle was moved to change the horizontal distance to the air inlet. The test particles used were 50 μm spherical glass beads and 70 μm spherical resin beads. The terminal velocities of both particles are comparable. In the experiment, the test particles were allowed to settle at 1 g/min after the average cross-sectional wind velocity at the inlet stabilized at 5 m/s. Some of the settled particles are ingested into the air intake duct and collected by a filter, and the other particles fall onto the floor of the chamber. The ingestion mass ratio, defined as the ratio of the ingestion mass to the feed mass of the test particles, was measured for the distance from the inlet.
Large eddy simulations were performed with OpenFoam 8. The multiphase particle-in-cell method with two-way coupling was used to analyze the behavior of solid particles within a fluid flow. After the fully developed flow was obtained in the computational domain, spherical particles were injected from the top of the domain with the same size, density and feeding rate as the experiments. The ingestion mass ratio was calculated for the flow field after 30s, which is long enough after the particles were injected.
Both experimental results and analysis results confirmed that the ingestion mass ratios of both test particles decreased as the distance from the air inlet increased. It was confirmed that the ingestion mass ratios obtained from the analysis were approximately the same as the ratios obtained in the experiments, although there was some difference. Therefore, it is thought that this analysis method can estimate the ingestion of spherical particles.
Comparing the experimental results of the ingestion mass ratios of two types of test particles with similar terminal velocities, the results were almost the same, although the glass beads with smaller particle diameters tended to have higher ingestion mass ratios. The analysis showed almost no difference between the two test particles. This suggests that particles with similar terminal velocities have similar ingestion mass ratios. To establish the method to estimate the amount of volcanic ash ingestion based on its terminal velocity, experiments for particles with various sizes and shapes will be conducted.