Based on the multidimensional compressor model with steady air injection

and in consideration of the mass and momentum effects and the unsteady influence introduced by the unsteady flow

the multidimensional compressor model with unsteady air injection was established. The principle of compressor modal control was analyzed

and modal control law using unsteady air injection was derived. Taking an axial compressor as example

modal control with different modes were simulated under stall condition. It indicates that using unsteady air injection

the same effect is achieved with only 57%-80% injected mass flow compared with steady and continual air injection

the extended stability range reaches 2.34% with the first four mode control

and also the stability range extends with the increment of mode number controlled.