Abstract: In view of complex and changeable characteristics of operating conditions of electric vehicle A/C system, research is conducted on the performance of back pressure chamber under off-design conditions of its scroll compressor. In consideration of the influence of balance weight agitation, the flow distribution characteristics of the back pressure chamber with different inlet pressure under variable operating conditions is simulated by FLUENT sliding mesh technique. The results show that the flow distribution of the back pressure chamber, the axial balance force and the amount of circulating oil change regularly under variable operating conditions. A new design method is proposed to coordinate the design of the axial balance force and the axial gas force angle position in order to optimize the operation of the orbiting scroll, with the axial force amplitude reduced by 31%

Key words: electric vehicle, air conditioning, off-design condition, scroll compressor, back pressure chamber