A study of some factors affecting the effectiveness of casing treatment in a contra-rotating axial compressor stage

199-207<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:"times="" roman";mso-ansi-language:en-us;="" mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">The paper presents the results of an experimental investigation on the effects of some factors on the effectiveness of casing treatment in a contra-rotating axial compressor stage having a hub-tip ratio of 0.667 and tip diameter of 486 mm. Three types of casing treatments, viz., axial slots, axial skewed slots and circumferential grooves, have been examined for different contra-speed ratios and for two settings of axial spacing between contra-rotors, viz., close (1/3rd of blade chord) and large (2 times blade chord). The radial variation of flow structure, and pressure quantities are examined at downstream of contra-rotors for solid as well as treated casing and these traverse results are analyzed to derive the relative total head loss coefficients and total to total blade element efficiency for contra-rotors as well as the contra-stage. The study reveals that the type of casing treatment used, the speed ratio and the axial gap between contra-rotors significantly affects the effectiveness of casing treatment.