An analytical and experimental investigation of a gas-dynamic technique for the continuous feeding of powdered solids to high-pressure vessels

The "gas-dynamic injector", a device designed to feed powdered solids in a continuous, well-controlled manner to high-pressure vessels, is investigated analytically and experimentally to determine its feasibility for practical applications. The device operates with a high-pressure primary gas and a low-pressure secondary gas. By expanding the primary gas in a converging-diverging nozzle, a low-pressure region of supersonic flow is created. There, a suspension of solids in secondary gas is injected. After a constant-pressure mixing process occurs, the pressure is raised in a shock wave and a subsonic diffuser. The assumption that the gaseous and solid phases in the mixture are always in equilibrium allows the flows to be mathematically modeled as frictionless, one-dimensional flows of an ideal gas. Results from a parametric study show that the practical application of the gas-dynamic injector for the feeding of powdered coal to combustors operating at pressures on the order of 18 bar is possible. The experimental study, which was conducted to verify the mathematical model, indicates that viscous friction needs to be accounted for in future analyses.