Abstract
The increasing turbine entry temperature has placed demands for improvements in engine cooling, and the work described in this paper is the development of a new film cooling configuration to meet this demand. In this study, numerical simulations were performed to predict the improvement in film cooling performance with novel film hole called an annular film hole. The film cooling performance parameters such as heat transfer coefficient (h), film cooling effectiveness (\({\eta)}\) and the net heat flux reduction (NHFR) over flat plate were investigated and compared with other configurations. Velocity profiles, pressure coefficient and turbulence kinetic energy contours were discussed. Four mass flow rates of secondary flow fluid were used to investigate the effects of film coolant velocity on the film cooling performance behavior. Results indicate that an annular film hole gives high film effectiveness, low heat transfer coefficient and higher NHFR compared to rectangular and circular film holes. The average values of laterally averaged film cooling effectiveness of the annular film hole increased to 106 and 328.5% compared with the rectangular and circular film holes at moderate flow rate, respectively. This difference is attributable to decreasing the jet vertical velocity component in a case of the annular hole. Also the low and high heat transfer coefficient regions were described for annular hole in detail.
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Abbreviations
- C P :
-
Pressure coefficient (–), \({C_P =\frac{P-P_\infty }{0.5\ast\rho _\infty \ast u_\infty ^2 }}\)
- D h :
-
Hydraulic hole diameter (m)
- DR :
-
Density ratio of coolant to mainstream, \({\rho_{{\rm c}}/\rho_{\infty }}\) (–)
- h :
-
Heat transfer coefficient (W/m2 K)
- L :
-
Hole length (m)
- M :
-
Blowing ratio of coolant to mainstream \({{M} = {\it {DR}}\ast {U}_{{c}}/ {U}_{\infty }}\) (–)
- NHFR:
-
Net heat flux reduction, \({{NHFR}=1-\frac{h}{h_o }(1-\eta{\ast}\varphi )}\)
- P :
-
Pressure of the fluid (Pa)
- \({\dot {q}}\) :
-
Heat flux rate (W/m2)
- \({{Re}_{{{D}}_{{h}}} }\) :
-
Reynolds number based on \({{u}_{\infty }}\) and D h \({{Re}_{{{D}}{_{{\rm h}}}} ={\rho u_\infty D_h }/\mu}\)
- S :
-
Hole spacing (m)
- T :
-
Temperature (K)
- Tu :
-
Mainstream turbulence intensity (%)
- u :
-
Velocity (m/s)
- X :
-
Streamwise coordinate along model surface (m)
- Y :
-
Vertical coordinate (m)
- Yplus:
-
Non-dimensional wall distance
- \({\varphi }\) :
-
Inverse of non-dimensional metal temperature, (\({{T}_{\infty }- {T}_{{c}})/({T}_{\infty }-{T}_{{w}})}\)
- \({\alpha}\) :
-
Coolant injection angle (\({^{\circ}}\))
- \({\eta}\) :
-
Adiabatic effectiveness, (\({{T}_{\infty }-{T}_{{aw}})/({T}_{\infty }-{T}_{{c}})}\)
- \({\theta}\) :
-
Non-dimensional temperature ratio, (\({{T}_{\infty }-{T})/({T}_{\infty }-{T}_{{c}})}\)
- \({\rho}\) :
-
Density (kg/m3)
- \({\infty}\) :
-
Mainstream
- aw :
-
Adiabatic wall
- c :
-
Coolant
- o :
-
without film cooling
- w :
-
Wall
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Abdala, A.M.M., Elwekeel, F.N.M. CFD Simulations of Film Cooling Effectiveness and Heat Transfer for Annular Film Hole. Arab J Sci Eng 41, 4247–4262 (2016). https://doi.org/10.1007/s13369-016-2028-3
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DOI: https://doi.org/10.1007/s13369-016-2028-3