Preliminary study of effects of primary and back pressure on performance of supersonic ejector driven by compressed air

The ejectors have some advantages such as simple, reliable and no moving parts. They can be used in air-conditioning and refrigeration application. Six different ejectors use air as working fluid in this study were proposed and tested experimentally. The Variable Area Ratios of Ejectors (A3/At) were used with range from 10.68 to 30.62. The aim of this study was to investigate these ejectors under variation of primary pressure (1.5–6.0 brag) brag and adjustable spindle position from 0 to -25 mm. Two groups of ejectors (A and C) were categorised based on the type of nozzle. The effect of Variation of primary pressure (Pp) on entrainment ratio was carried out at different spindle positions. Furthermore, the effect of Variation of back pressure (Pb) on entrainment ratio (ω) was tested under range of primary pressure (3-4.5 brag). At maximum primary pressure (6.0 brag), the entrainment ratios (ω) of ejector (A A) were 0.35, 0.21 and 0.14 for spindle positions (- 25mm), (-15mm) and (-5mm), respectively. While, the maximal entrainment ratios (ω)obtained from ejector (C C) are 0.32, 0.35 and 0.39 for spindle positions (-15mm), (-20mm) and (-25mm), respectively The results show the maximal value for performance of ejector CC is higher than ejector AA about 11.4 %. The ejector (C B) has highest entrainment ratios (ω) about 0.43 compared with the rest of ejectors in groups (A) and (C) at maximum primary pressure (6.0 brag) and adjustable spindle position (-25mm). Group A is more proper for higher values of back pressure, whilst, Group C is more suitable for high performance of ejector.