Maximizing pressure recovery using lobed nozzles in a supersonic ejector

Novel designs for supersonic ejectors in refrigeration applications focus on the reduction of the primary fluid flow rates required (entrainment ratio), as well as, increasing the total pressure recovery. This work improves the performance by enhanced mixing through flow instability by adding lobes to the circular nozzle design, combined with the profiling of the mixing channel. The objective was to determine the impact of the aspect ratio and total perimeter of the lobes on system pressure recovery and entrainment ratio. Using the conditions and geometry from the Eames [1] profiled mixing channel as the baseline and integrating a lobed nozzle, an improved pressure recovery of 6.4 from 4.0 with a perimeter value of 30 mm was achieved. Increasing the perimeter beyond this value drives the frictional losses along the wall surfaces to dominate the process and the recovered pressure reduces back to the circular nozzle. (C) 2011 Elsevier Ltd. All rights reserved.