Gas-Dynamic Flow Structure in a Vertical Conical Diffuser with Air Supplied Through Nozzles at Different Angles

Conical diffusers perform a variety of critical functions in final products (gas, hydraulic, and wind turbines, ejectors, gasifiers, combustion chambers, etc.). The purpose of this study was to experimentally study the flow distribution features in a vertical conical diffuser with different technical air supply methods to find directions for optimal movement organization. The vertical diffuser (apparatus) consisted of a conical section with an opening angle of 30° and a cylindrical section. The scientific results were obtained based on an experimental stand and the thermal imaging method. The article presents simplified equations of continuity and momentum balance for the system under consideration. Two methods of air supply to the diffuser were investigated: air supply through a single duct and air supply through 4 nozzles installed at different angles of 45°, 60°, and 70°. The experiments were carried out for stationary air movement with volumetric flow consumption through the system from 0.0018 m3/s to 0.006 m3/s. The Reynolds number for the air flow at the diffuser inlet ranged from 10,500 to 106,000. Significant differences in the flow structure for air supply to a diffuser through a single duct and nozzles were identified. The possibility of controlling the flow structure in a vertical diffuser by varying the inclination of the supply nozzles was demonstrated. Four characteristic patterns of air distribution in the diffuser were obtained: firstly, a pronounced central flow through the entire apparatus with a noticeable deviation of the flow to the right side; secondly, a local (from 30 to 75% of the apparatus height), central flow in the diffuser; thirdly, active air movement in the lower part of the diffuser with subsequent flow along the side walls of the apparatus; fourthly, multidirectional flow movement throughout the entire volume of the diffuser.