Abstract
The effect of conjugate heat transfer is investigated on a first stage nozzle guide vane (NGV) of a high pressure gas turbine which has both impingement and film cooling holes. The study is carried out computationally by considering a linear cascade domain, having two passages formed between the vanes, with a chord length of 228 mm and spacing of 200 mm. The effect of (i) coolant and mainstream Reynolds numbers, (ii) thermal conductivity (iii) temperature difference between the mainstream and coolant at the internal surface of the nozzle guide vane are investigated under conjugate thermal condition. The results show that, with increasing coolant Reynolds number the lower conducting material shows larger percentage decrease in surface temperature as compared to the higher conducting material. However, the internal surface temperature is nearly independent of mainstream Reynolds number variation but shows significant variation for higher conducting material. Further, the temperature gradient within the solid thickness of NGV is higher for the lower conductivity material.
Funding statement: GTRE and GATET Bangalore.
Nomenclature
- Bi
Biot number, non-dimensional
- C
Vane hord, m
- d
Jet diameter, m
- D
Coolant pipe diameter, m
- h
Heat transfer coefficient, W/m2K
- hi
Heat transfer coefficient of internal surface, W/m2K
- he
Heat transfer coefficient of external surface, W/m2K]
- H
Distance between jet hole and target surface, m
- k
Thermal conductivity, W/m.K
- l
Span length, m
- m
Mass flow, kg/s
- Nu
Nusselt number, non-dimensional
- q″
Heat flux
- Re
Reynolds number, non-dimensional
- S
Distance along the vane surface from leading edge, m
- Sp.max
Distance along pressure surface from leading edge to trailing edge, m
- Ss.max
Distance along suction surface from leading edge to trailing edge, m
- T
Temperature, K
- t
Thickness of vane, m
- V
Velocity
- Greek symbols
- ρ
Density, kg/m3
- κ
Turbulent kinetic energy, m2/s2
- ω
Specific dissipation rate, 1/sec
- μ
Coefficient of viscosity, N s/m2
- φ
Overall effectiveness, (Tm-Te)/(Tm-Tc)
- θ
Non-dimensional temperature, (Ti-Tc)/(Tm-Tc)
- Subscripts
- amb
Ambient
- c
Coolant
- e
External
- f
Fluid
- i
Internal
- m
Mainstream
- s
Solid
- w
Wall
Abbreviations
- AIT
Aft Impingement Tube
- DH
Hydraulic Diameter
- FIT
Front Impingement Tube
- HTC
Heat Transfer Coefficient
- LER
Leading Edge Region
- NDL
Non-Dimensional Length, (=S/Ss.max, S/Spmax)
- NDT
Non-Dimensional Temperature, θ
- NGV
Nozzle Guide Vane
- PSIH
Pressure Surface Impingement Hole
- PSMS
Pressure Surface Mid-Span
- RANS
Reynolds Averaged Navier Stokes
- SSFR
Suction Surface Fillet Region
- SSIH
Suction Surface Impingement Hole
- SSMS
Suction Surface Mid-Span
- SST
Shear Stress Transport
Acknowledgment
The authors would like to thank GATET and GTRE Bangalore for the financial support for the present investigation.
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