A COMBINED NUMERICAL AND EXPERIMENTAL ASSESSMENT OF AIR AND DUST FLOW IN A LOW-REYNOLDS NUMBER VALVE INCLUDING MODIFICATIONS TO PREVENT VALVE SEAL CONTAMINATION

摘要

High concentrations of particulate matter in air lead to deposition at the sealing radius of self-sealing valves involving direct intake from the environment. Dust deposition at and near this radius causes an increase in leakage flow when the valve is closed. In this paper, the mechanism which results in dust deposition in such valves is investigated and a new valve design which reduces leakage flow is developed and experimentally assessed. ANSYS Fluent 15.0 is used to numerically model the laminar flow assuming axisymmetry. Particle paths are predicted using Discrete Phase Modeling (DPM) as a post-processing step. Experimentally, dust deposition, mass flow at the operating pressure differential, and leakage flow rate are measured. The numerical and experimental results are utilized together to gain insight into the particles' behavior. One of the key outcomes of this work is a post-processing technique which allows the numerical and experimental particle deposition results to be quantitatively compared. This supports the utlity of the numerical approach as locations of high concentrations of particle impacts in the numerical simulations are associated with locations of dense dust deposition in the experiments. High concentrations of particles at and near the sealing radius are observed to lead to increased leakage flow. Therefore, the impact of high concentrations of particles in this region is to be avoided. Utilizing this insight, the valve geom- etry is modified to reduce the amount of dust deposited in the region of the sealing radius. In the modified design, leakage flow is decreased by up to 93%, with a maximum of 2.1% reduction in flow rate margin relative to valve specifications.