Enhancement of film cooling effectiveness using backward injection holes

Park, Sehjin; Jung, Euo Chang; Kim, Seon Ho; Sohn, Hong Gyoo; Cho, Hyung Hee

doi:10.1016/j.ijthermalsci.2016.08.001

Cited by 47 publications

(4 citation statements)

References 13 publications

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“…It was found that the film cooling hole with backward injection provides higher film cooling effectiveness in the spanwise direction, by comparing with film cooling hole with forward injection. An experimental investigation on film cooling of a flat surface with forward and backward injection was carried out by Park et al [20]. The results indicated that at a high blowing ratio, the enhancement and uniform distribution of film cooling effectiveness were produced by cylindrical holes with backward injection.…”

Section: Introductionmentioning

confidence: 99%

An LBM-Based Investigation on the Mixing Mechanism of Double Rows Film Cooling with the Combination of Forward and Backward Jets

Shangguan

Cao

2022

Energies

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Film cooling has been widely applied to the highly efficient thermal protection of gas turbines. By using the simplified thermal lattice Boltzmann method (STLBM), a series of large-scale simulations of film cooling are performed to dig up the mixing mechanism of double rows film cooling with the combination of forward and backward jets at the first attempt. The combination of an upstream row with forward jet and a downstream row with backward jet is considered. The Reynolds number is 4000. The blowing ratio of the upstream coolant jet is fixed as BR1=0.5. For the downstream coolant jet (BR2), five values ranging from 0.2–0.8 are considered. The inclination angles of forward jet and backward jet are 35° and 145°, respectively. The numerical results reveal that the performance of film cooling is greatly improved by backward downstream jet due to the suppression of counterrotating vortex pair (CVP). Moreover, the flow structure is changed with the blowing ratio of backward jet. An anti-CVP having the opposite rotational direction to CVP appears as the blowing ratio of backward jet is large. The special flow structure weakens the adverse effect of CVP and transports much coolant jet to the cooled wall. Correspondingly, the time-averaged film cooling effectiveness is increased and the fluctuation of film cooling effectiveness is decreased. All of these indicate that a backward downstream jet with a large blowing ratio improves film cooling performance. The results obtained in this work help to the optimization of film cooling scheme, which also benefit the promotion and application of STLBM in gas turbine engineering.

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Section: Introductionmentioning

confidence: 99%

An LBM-Based Investigation on the Mixing Mechanism of Double Rows Film Cooling with the Combination of Forward and Backward Jets

Shangguan

Cao

2022

Energies

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“…Because backward coolant injection could provide a uniform film cooling in the lateral direction relative to the forward coolant injection, it was suggested to be a possible scheme for weakening the thermal gradients. For conventional cylindrical-hole film cooling, the backward injection was clearly identified by many researchers (Park et al [31], Singh et al [32], Prenter et al [33], Shi et al [34]) to be advantageous to forward injection in terms of average film cooling effectiveness and comparable net heat flux reduction. However, it remains unclear whether backward injection can achieve the same results in shaped-hole cooling as it does in cylindrical-hole cooling.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation on Backward-Injection Film Cooling with Upstream Ramps

et al. 2022

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The present study investigates the effects of upstream ramps on a backward-injection film cooling over a flat surface. Two ramp structures, referred to as a straight-wedge-shaped ramp (SWR) and sand-dune-shaped ramp (SDR), are considered under a series of blowing ratios ranging from M = 0.5 to M = 1.5. Regarding the backward injection, the key mechanism of upstream ramps on film cooling enhancement is suggested to be the enlargement of the horizontal scale of the separate wake vortices and the reduction of their normal dimension. When compared to the SDR, the SWR modifies the backward coolant injection well, such that a larger volume of coolant is suctioned and concentrated in the near-field region at the film-hole trailing edge. As a consequence, the SWR demonstrates a more pronounced enhancement in film cooling than the SDR in the backward-injection process, which is the opposite of the result for the forward-injection scheme. For the SWR, the backward injection provides a better film cooling effectiveness than the forward injection, regardless of blowing ratios. However, for the SDR, the backward injection could show a superior effect to the forward injection on film cooling enhancement, when the blowing ratio is beyond a critical blowing ratio. In the present SDR situation, the critical blowing ratio is identified to be M = 1.0.

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“…In this latter application an oxygen-free coolant gas is used, which allows the ACE to be inferred from the local oxygen concentration provided the surface pressure distribution is known. More recently, the PSP technique is adopted to help study various different parameters in effusion/film cooling, such as BR [12] and cooling hole arrangement [13].…”

Section: Introductionmentioning

confidence: 99%