**5. Conclusions**

In order to improve the cooling efficiency of internal turning processes and achieve green cutting, an internal spray cooling turning tool was developed. The fluid-solid thermal coupling simulation model was established to simulate heat transfer during internal turning with internal spray cooling. The parameters of the cooling tool structure were optimized. The cutting experiments were conducted to investigate the cooling performance of the optimized internal spray cooling turning tool. The main conclusions can be drawn as follows:


**Author Contributions:** Conceptualization, S.S. and L.L.; data curation, H.L. and X.C.; funding acquisition, S.S.; project administration, S.S. and L.L.; software, H.L.; writing—review and editing, H.L. and S.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the National Natural Science Foundation of China (Grant No. 52165058 and 51705153) and the Jiangxi Provincial Natural Science Foundation of China (Grant No. 20192BAB206029).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.
