To explore the inlet air cooling effect in a precooled turbine-based combined cycle engine, a numerical investigation for air/droplet fully coupled cooling is performed in the cooling section with a spray system. The accuracy of numerical simulation program for mass injection cooling methodology is qualified with the experimental data. Results indicate that an even spray arrangement is beneficial to the uniform distribution of flow field, and it is also the major factor resulting in the flow loss. Although the flow loss of dry air is irreversible in the flow process, the additional new energy of water vapor can contribute total energy of wet air mixture. In contrast, under the lowest requirement qualified of mass injection cooling at two high-altitude simulation environments, the total-pressure drop coefficients are 3.22-4.22% before mist injection and 2.87-3.86% after mist injection; the total-temperature drop coefficient is 10.09% and 16.29%, respectively, for dry air and wet air conditions. After optimization for spray apparatus, the flow loss can decrease by about 55.84% before mist injection and about 64.53% after mist injection. Additionally, a little influence is for flow field temperature. Therefore, water injection cooling can effectively improve the flow field characteristics due to a larger total-temperature drop and a smaller total-pressure loss in the cooling section. (C) 2019 Elsevier Ltd. All rights reserved.