A numerical study of rotation effects on jets effusing from inclined holes into a cross-flow

Abstract

In this work, the complexity of the flow field arising from the impact of the interaction of coolant jets with a hot cross-flow under rotation conditions was numerically simulated using large eddy simulation with artificial inflow boundary condition. The finite-volume method and the unsteady PISO (Pressure Implicit with Splitting of Operators) algorithm were applied on a non-uniform staggered grid. The simulations were performed for four different values of rotation number (Ro) of 0.0, 0.03021, 0.06042, and 0.12084, a jet Reynolds number of 4700, based on the hole width and the jet exit velocity. The air jet was injected at 30 • and 90 • in the streamwise direction with a density ratio of 1.04 and a velocity ratio of 0.5. The flow fields of the present study were compared with experimental data in order to validate the reliability of the LES technique. It was shown that the rotation has a strong impact on the jet trajectory behaviour and the film cooling effectiveness. The film trajectory always inclines centrifugally. Under rotating conditions, the film trajectory departs from the centreline to the left boundary. The deflection becomes greater as Ro increases. Furthermore, it was also found that the injection angle has a strong impact on separation and reattachment behaviour as well as the strength of the penetration into the cross-flow. As it increases, the distribution of the film cooling downstream the jet exit is more non-uniform and the film cooling effectiveness level slightly decreases.

Modelling of heat transfer and fluid flow in the hot section of gas turbines used in power generation: A comprehensive survey

“…Furthermore, film cooling methods are widely used as the external cooling mechanism of gas turbine blades. Pin fin technology, cooling effusion, and transpiration cooling are other external cooling methods of gas turbine blades …”

“…Gas turbine cooling has a major impact on the efficiency, durability, and maintenance of the turbine. Previous work by Al‐Zurfi and Turan has assessed the development of a novel cooling technology based on “antivortex” concepts to significantly increase the cooling effectiveness. This has been achieved by employing advanced concepts in fluid mechanics incorporating boundary layer management methodologies .…”

“…Reynolds numbers vary in the range of 1 × 10 6 to 1.5 × 10 6 . According to Al‐Zurfi et al, heat transfer coefficients over the entire aerofoil surface show a significant increase when the exit Reynolds numbers are increased …”

“…Pin fin technology, cooling effusion, and transpiration cooling are other external cooling methods of gas turbine blades. 17,18 In film cooling mechanisms, cooling air is pumped out of the blade via multiple small holes in the structure. A thin layer (a film) of cooling air is created on the external surface of the blade, reducing heat transfer from main flow (which is at a higher temperature than the melting point of the blade material).…”

“…According to Al-Zurfi et al, heat transfer coefficients over the entire aerofoil surface show a significant increase when the exit Reynolds numbers are increased. 17 The surface roughness effect is another heat transfer enhancement factor of NGVs. Due to combustion deposits, the vane surface might become rough after a few hours of the operation.…”