Trailing edge shock modulation by pulsating coolant ejection

Saracoglu, Bayindir H.; Paniagua, Guillermo; Salvadori, Simone; Tomasoni, Flora; Duni, S.; Yasa, Tolga; Miranda, Alice

doi:10.1016/j.applthermaleng.2012.04.036

Cited by 21 publications

(12 citation statements)

References 19 publications

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“…The thin trailing edge of turbine blades cannot be protected using internal cooling passages, so cooler flow bled from the high pressure compressor is purged through slots or orifices to avoid the melting of the turbine components. As it has been shown by several authors [11,12], this cooling could be exploited to modulate the base region properties. Different studies [13][14][15] have been devoted to examine the effects of trailing edge bleeding on the base region.…”

Section: Introductionmentioning

confidence: 83%

Pressure Bifurcation Phenomenon on Supersonic Blowing Trailing Edges

et al. 2019

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Turbine blades operating in transonic-supersonic regime develop a complex shock wave system at the trailing edge, a phenomenon that leads to unfavorable pressure perturbations downstream and can interact with other turbine stages. Understanding the fluid behavior of the area adjacent to the trailing edge is essential in order to determine the parameters that have influence on these pressure fluctuations. Colder flow, bled from the high-pressure compressor, is often purged at the trailing edge to cool the thin blade edges, affecting the flow behavior and modulating the intensity and angle of the shock waves system. However, this purge flow can sometimes generate non-symmetrical configurations due to a pressure difference that is provoked by the injected flow. In this work, a combination of RANS simulations and global stability analysis is employed to explain the physical reasons of this flow bifurcation. Analyzing the features that naturally appear in the flow and become dominant for some value of the parameters involved in the problem, an anti-symmetrical global mode, related to the sudden geometrical expansion of the trailing edge slot, is identified as the main mechanism that forces the changes in the flow topology.

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Section: Introductionmentioning

confidence: 83%

Pressure Bifurcation Phenomenon on Supersonic Blowing Trailing Edges

et al. 2019

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“…The simulation of the unsteady interaction between the coolant and the main-flow would allow for the estimation of the enhanced mixing generated in the wake of the jets at the integral scales of turbulence by main-flow fluctuations (especially at higher BR values). Furthermore, an unsteady computation would reproduce the oblique shock fluctuation generated by the vortex shedding that occurs at the TE of the central plate (similarly to what is shown in [32]). It must be underlined that the correct intensity of a shock can be correctly captured only by an unsteady analysis due to non-linear, unsteady stress terms [33].…”

Section: Final Comments On the Deterministic Datamentioning

confidence: 77%

Uncertainty Quantification of Non-Dimensional Parameters for a Film Cooling Configuration in Supersonic Conditions

Salvadori

Carnevale

Fanciulli

et al. 2019

Fluids

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In transonic high-pressure turbine stages, oblique shocks originating from vane trailing edges impact the suction side of each adjacent vane. High-pressure vanes are cooled to tolerate the combustor exit-temperature levels, then it is highly probable that shock impingement will occur in proximity to a row of cooling holes. The presence of such a shock, together with the inevitable manufacturing deviations, alters the location of the shock impingement and of the performance parameters of each cooling hole. The present work provides a general description of the aero-thermal field that occurs on the rear suction side of a cooled vane. Computational Fluid Dynamics (CFD) is used to evaluate the deterministic response of the selected configurations in terms of adiabatic effectiveness, discharge coefficient, blowing ratio, density ratio, and momentum ratio. Turbulence is modelled by using both the Shear Stress Transport method (SST) and the Reynolds Stress Model (RSM) implemented in ANSYS FLUENT . The obtained results are compared with the experimental data obtained by the Institut für Thermische Strömungsmaschinen in Karlsruhe. Two uncertainty quantification methodologies based on Hermite polynomials and Padè-Legendre approximants are used to consider the probability distribution of the geometrical parameters and to evaluate the response surfaces for the system response quantities. Trailing-edge and cooling-hole diameters have been considered to be aleatory unknowns. Uncertainty quantification analysis allows for the assessment of the mutual effects on global and local parameters of the cooling device. Obtained results demonstrate that most of the parameters are independent by the variation of the aleatory unknowns while the standard deviation of the blowing ratio associated with the hole diameter uncertainty is around 12%, with no impact by the trailing-edge thickness. No relevant advantages are found using either SST model or RSM in combination with Hermite polynomials and Padè-Legendre approximants.

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“…Attenuating losses due to shock waves at the trailing edge and wake unsteadiness with pulsant coolant ejection was the focus of the research presented by Saracoglu et al 6 . In the last few years, research attempted different techniques to inhibit or delay separation.…”

Section: Introductionmentioning

confidence: 99%

Flow Control of Unsteadiness in the Wake of a Turbine Blade

Irsch

Davis

Clark

et al. 2015

53rd AIAA Aerospace Sciences Meeting

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Vortex shedding, such as the von Kármán vortex street, leads to higher mixing in the wake and unsteady forces on turbine airfoils. As a result, aerodynamic efficiency decreases and structural stress increases. The objective of the present work is to analyze the unsteadiness formed by vortex shedding at the trailing edge of a turbine vane and to manipulate/control this unsteadiness. The effects of steady injection through a tube at the trailing are studied. A detached-eddy simulation procedure, MBFLO2, is used to simulate the flow over and within the turbine vane section. It is found that the injection effectively reduces wake vortices and hence mixing in the wake as well as unsteady forces on the vane. Results show dependence on angular position of the tube as well as on the amount of injected flow.

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Trailing edge shock modulation by pulsating coolant ejection

Cited by 21 publications

References 19 publications

Pressure Bifurcation Phenomenon on Supersonic Blowing Trailing Edges

Pressure Bifurcation Phenomenon on Supersonic Blowing Trailing Edges

Uncertainty Quantification of Non-Dimensional Parameters for a Film Cooling Configuration in Supersonic Conditions

Flow Control of Unsteadiness in the Wake of a Turbine Blade

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