How does intercooling reduce the work required by a gas-turbine compressor?

Intercooling reduces the work required by a gas-turbine compressor by decreasing the volume of the air being handled during the compression process.1

In practice, this is achieved by performing the compression in two or more stages and cooling the air between these steps—typically using water—to return it to its initial temperature. By compressing the air at a nearly constant temperature, the process effectively lowers the overall volume of the air throughout the compression cycle, which directly reduces the total work required to achieve the desired pressure. This technique is primarily utilized in stationary gas turbines, as the additional equipment required for intercooling is generally not feasible for aircraft engines due to weight and size constraints.1