*Article* **Numerical Investigation of Single-Row Double-Jet Film Cooling of a Turbine Guide Vane under High-Temperature and High-Pressure Conditions**

**Jin Hang, Jingzhou Zhang \*, Chunhua Wang \* and Yong Shan**

Key Laboratory of Thermal Management and Energy Utilization of Aircraft, College of Energy and Power Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China; hjhangjin@163.com (J.H.); nuaasy@nuaa.edu.cn (Y.S.)

**\*** Correspondence: zhangjz@nuaa.edu.cn (J.Z.); chunhuawang@nuaa.edu.cn (C.W.)

**Abstract:** Single-row double-jet film cooling (DJFC) of a turbine guide vane is numerically investigated in the present study, under a realistic aero-thermal condition. The double-jet units are positioned at specific locations, with 57% axial chord length (*C*x) on the suction side or 28% *C*x on the pressure side with respect to the leading edge of the guide vane. Three spanwise spacings (*Z*) in double-jet unit (*Z* = 0, 0.5*d*, and 1.0*d*, here *d* is the film hole diameter) and four spanwise injection angles (*β* = 11◦, 17◦, 23◦, and 29◦) are considered in the layout design of double jets. The results show that the layout of double jets affects the coupling of adjacent jets and thus subsequently changes the jet-in-crossflow dynamics. Relative to the spanwise injection angle, the spanwise spacing in a double-jet unit is a more important geometric parameter that affects the jet-in-crossflow dynamics in the downstream flowfield. With the increase in the spanwise injection angle and spanwise spacing in the double-jet unit, the film cooling effectiveness is generally improved. On the suction surface, DJFC does not show any benefit on film cooling improvement under smaller blowing ratios. Only under larger blowing ratios does its positive potential for film cooling enhancement start to show. Compared to the suction surface, the positive potential of the DJFC on enhancing film cooling effectiveness behaves more obviously on the pressure surface. In particular, under large blowing ratios, the DJFC plays dual roles in suppressing jet detachment and broadening the coolant jet spread in a spanwise direction. With regard to the DJFC on the suction surface, its main role in film cooling enhancement relies on the improvement of the spanwise film layer coverage on the film-cooled surface.

**Keywords:** double-jet film cooling; turbine guide vane; pressure surface; suction surface; numerical simulation
