This study develops a new method for the separation of small (10 m. in diameter and smaller) particles from a gas stream. In this method, the gas stream is arranged to flow as a jet, and forced to impinge upon a conically shaped impactor surface. The tip of the cone surface, and only a small fraction (termed the minority flow) actually moves through the aperture. The average size of the particles in the minority flow is much larger than that in the mainstream which passes over the particles because the larger particles, with greater momentum, cannot negotiate the turn and follow the small particles into the aperture. The aperture is joined to two concentric tubes. The outer tube has a solid wall, and the inner tube a porous wall for a short distance near its end joining the solid plate. Gas is supplied at high pressure to the annular space between the tubes, and passes through the porous part of the tube into the space behind the aperture creating a counterflow. Finally suction is applied in the inner tube, downstream from the aperture. The combination of suction and flow through the porous tube creates a plane of zero flow which separates gas flowing out of the bottom of the inner tube and gas flowing out of the aperture. Particles that have traveled through the aperture must progress against the counterflow. The ones large enough that their momentum can allow them to pass through the counterflow and eventually rejoin the majority flow over the cone. By adjusting the counterflow pressure the plane of zero flow can be moved, and this provides some control of the particle size distribution collected at the downstream end. The study will improve on this design by causing the jet gas stream impacting on the cone to move at supersonic speeds. Supersonic speeds allow large particle velocities, and permits smaller particles to pass through the plane of zero flow and be collected.
