Numerical Investigation of Active Flow Control of Low-Pressure Turbine Endwall Flow

Romero, Sergio; Groß, Andreas

doi:10.2514/1.b37281

Cited by 12 publications

(6 citation statements)

References 31 publications

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“…The recent literature shows much promise of scale-resolving tools (Lehmkuhl, Park, Bose, & Moin, 2018;Milani et al, 2019;Romero & Gross, 2019;Wu & Piomelli, 2018;Xia, Kalitzin, Lee, Medic, & Sharma, 2020;Xu, Yang, & Milani, 2021b; and machine learning (Milani, Ling, & Eaton, 2020;Milani, Ling, Saez-Mischlich, Bodart, & Eaton, 2018;Waschkowski, Zhao, Sandberg, & Klewicki, 2021;Weatheritt, Zhao, Sandberg, Mizukami, & Tanimoto, 2020;Zhou, He, & Yang, 2021). However, RANS is still the workhorse for the fluid engineering.…”

Section: Reynolds-averaged Navier Stokesmentioning

confidence: 99%

Direct numerical simulation of slot film cooling downstream of misaligned plates

Lynch

Yang

2022

Flow

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When manufacturing a turbine engine, the combustor annulus and the turbine annulus are created as separate parts and assembled. This leads to an inter-platform gap between the two components, which must be supplied with leakage air to prevent ingestion of the extremely hot combustion gases into the interior of the engine. The combustor and the turbine are likely to misalign because of differential thermal expansion or assembly tolerances. This paper presents a direct numerical simulation study of inter-platform misalignment with leakage flow supplied at the junction of the platforms. The geometry is two misaligned plates with a cross-flow and a leakage flow simulated as a slot jet. The misalignment of the two plates gives rise to a forward misalignment configuration and a backward misalignment configuration, and the jet/cross-flow gives rise to a windward mixing layer and a leeward mixing layer. Compared with the aligned configuration, the cooling effectiveness immediately downstream of the gap decreases in the forward misalignment configuration and increases in the backward misalignment configuration; this response amplifies as the flow rate through the gap increases. In addition to the cooling effectiveness, we report flow statistics, including the velocity, the temperature, the turbulent kinetic energy and the relevant turbulent fluxes. We find strong turbulence generation in the leeward mixing layer and high turbulence level as a result. Mixing of the thermal energy, on the other hand, occurs predominantly in the windward mixing layer. The eddy viscosity and the eddy conductivity that are critical to turbulence modelling are also reported. We find negative eddy viscosity at regions where the incoming boundary layer starts to mix with the leakage jet. The analysis shows that the negative eddy viscosity is a result of flow hysteresis: it takes time, or travel distance, before the eddies in the incoming boundary layer and the eddies in the leakage jet come to an equilibrium, thereby favouring a transport Reynolds stress model over a local eddy viscosity type model. The novelty of this paper lies in the direct numerical simulations, which provide direct access to the near-wall flow field and clarify the effects of blowing ratio and platform misalignment on heat transfer. The novelty also lies in the data analysis, which sheds light on how this flow should be modelled.

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Section: Reynolds-averaged Navier Stokesmentioning

confidence: 99%

Direct numerical simulation of slot film cooling downstream of misaligned plates

Lynch

Yang

2022

Flow

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“…A different approach with a similar goal, reducing the separation bubble on the suction side of the blades at low Reynolds numbers, has been tried by Rohr and Yang [20]. In their work, the authors use numerical studies to validate the use of a "jet flap" injection system.…”

Section: Introductionmentioning

confidence: 99%

Application of a Performance-Improvement Method for Small-Size Axial Flow Turbines

Nicoara,

Crunteanu,

Vilag

2023

Aerospace

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As a main component of most gas-turbine engines, the axial flow turbines have been in a process of continuous improvement, reaching high efficiencies and reliability. A well-known drawback of these systems is the rapid decrease in performance when operating at lower than nominal conditions. Thus, a novel performance-enhancement method for axial turbines operating at partial loads has been previously proposed and numerically characterized. In this paper, one applies the aforementioned method for a smaller size axial flow turbine, part of a gas-generator assembly for a microjet engine, to determine, by the use of CFD analysis, the influence of the system at different partial regimes across the working line. A logical scheme based on iterative steps and multiple numerical simulations is also used to determine the engine response to the injection of compressor bleed air into the turbine passages. The results show, as determined in the previous study, that the generated power can be increased for all partial regimes, with the influence being more noticeable at higher regimes, leading to a reduction in fuel consumption in order to achieve the same regimes.

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“…There have been some DMD applications on the analysis of the unsteady inner flow in the turbomachinery. [16][17][18] By using of the DMD method on the flow near the endwall of a low-pressure turbine, Romero and Gross 19 studied the evolution process of the vorticity modes and applied the modes on the designing of the active control system. Bases on plenty of the transient results from a centrifugal compressor, the effects of the unsteady characteristics under rotating frequency were well understood with the help of DMD method by Li et al 20 However, to the best of the author's knowledge, there is few published materials on applying the DMD mode to the tip region study of axial compressors.…”

Section: Introductionmentioning

confidence: 99%

Analysis on the unsteady flow structures in the tip region of axial compressor

Song

Yang

2021

Proceedings of the Institution of Mechanical Engineers, Part A:

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The unsteady characteristic in the tip region of an axial compressor has been numerically studied with the help of the dynamic mode decomposition analysis. The characteristics of frequency and dynamic modes are compared and discussed under different operating points and different parameters, such as tip clearance and rotating speeds. For the flowfield structures in the tip region, such as tip leakage flow, separation flow and shock wave, their relationships with the unsteadiness are studied in detail. Except for the unsteadiness caused by the interaction between rotating rotor and the stationary boundaries, it is found that the unsteadiness is attributed to the moving of the low-velocity cell. Based on the generation and the development of the low-velocity cell, the unsteady characteristics in tip region are divided into 4 types: BPF-dominated, shedding-dominated, self-induced and separation-dominated. When the tip leakage flow is weak, the unsteadiness in the tip region is only triggered by the blade sweeping. As the tip leakage flow gets stronger to a certain extent, the low-velocity cell is shed into the flow passage and mixed with the main-flow. When the main-flow is weaker under the low flowrate condition, the interaction between the low-velocity cell and the pressure side occurs and generates a new low-velocity cell near the leading-edge of the neighboring blade. The frequency of the new cell generation is actually the self-induced frequency. In the zero and small clearance model, the low-velocity is shed by the separation in the leading-edge and the casing-suction corner. By understanding these unsteady characteristics, the change tendency of the leading frequency in the rotor tip is easily explained and forecasted. Furthermore, under the transonic operation condition, the low-velocity cell is decelerated and eliminated by the shock wave in the unsteadiness of the self-induced type and the separation-dominated type, respectively. Thus, the leading frequency in the tip flow field is moderated.

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Numerical Investigation of Active Flow Control of Low-Pressure Turbine Endwall Flow

Cited by 12 publications

References 31 publications

Direct numerical simulation of slot film cooling downstream of misaligned plates

Direct numerical simulation of slot film cooling downstream of misaligned plates

Application of a Performance-Improvement Method for Small-Size Axial Flow Turbines

Analysis on the unsteady flow structures in the tip region of axial compressor

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