The advantage of a trielectrode (TED) plasma actuator in the flow separation control on the two two-dimensional airfoil model has been investigated experimentally in 30 m/s uniform flow ( Re = 6.0×10⁵). Two exposed electrodes are set on the surface o f a NACA0012 airfoil model. For driving SDBD and TED plasma actuators separately, one exposed electrode for applyin g AC voltages is located at the leadingleading-edge, and DC voltages is applied to another one pla ced in 41.43 mm downstream from the leading edge. The flow field around the model was analyzed using time time-resolved PIV in a wind tunnel . The results indicated superior performance of the TED plasma actuator in separation delay when a high negative voltage ( V_dc = -20 kV) was applied, compared to the SDBD p lasma actuator. At the same time, the TED plasma actuator showed higher efficiency in energy consumption, when compared in terms of thrust generated per power supplied.

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This experimental work details the impact of forest-elevated turbulence levels on wind farm performance. In this regard, the wind flow field and power generation of wind turbines in two wind farms in flat forested terrain and flat unforested terrain are assessed. A mobile scanning LiDAR system is used to make measurements of the wind speed and turbulence intensity both in the undisturbed flow and downstream of a forest. Turbulence intensities up to 26% are measured immediately downstream of the forest at hub height, whereas in the undisturbed flow the turbulence intensity does not exceed 15%. While the turbulence levels decay as the wind flow evolves downstream, even at a downstream distance of 20 times the forest height, the turbulence intensities are above the undisturbed flow turbulence intensities. Turbulence dissipation rate is measured to be 8 times higher downstream of forest. On the other hand the deficit in wind speed that is measured immediately downstream of the forest is negligible at a downstream distance of 15 times the forest height. A comparison of the power performance of wind turbine without and with a forested fetch is made. It is shown that with a forested fetch there is a 30% loss in performance due to the forest-affected wind flow. Measurements at an isolated turbine show that higher turbulence causes higher fluctuations in generated power, with highest sensitivity observed for wind speeds in range of 8m/s-10m/s, which is below rated wind speed. Additionally, wind turbines in forested terrain show 2 times higher power curve scatter compared to similar turbines in unforested terrain. An assessment of the power production of the individual wind turbines in the two wind farms is made to assess the impact of forest-elevated turbulence levels on wake losses. It is seen that the wake losses are lower in forested terrain compared to unforested terrain.

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The paper presents the results of large-scale numerical simulations which were conducted for better understanding of unsteady flow phenomena in a multi-stage axial flow compressor at near-stall condition. The compressor is a test rig compressor which was used for development of the industrial gas turbine, Kawasaki L30A. The compressor consists of 14 stages, the front two stages and the front half stages of which were investigated in the present study. According to the test data, it is considered that the 2nd stage and the 5th or 6th stage are suspected of leading to the stall. The final goal of this study is to elucidate the flow mechanism of the rotating stall inception in the multi-stage axial compressor for actual gas turbines. In order to capture precise flow physics in the compressor, a computational mesh for the simulation was generated to have at least several million cells per passage, which amounted to 650 million cells for the front 2-stage simulation and two billion cells for the front 7-stage simulation (three hundred million cells for each stage). Since these were still not enough for the large-eddy simulation (LES), the detached-eddy simulation (DES) was employed, which can calculate flow fields except near-wall region by LES. The required computational resources were quite large for such simulations, so the computations were conducted on the K computer (RIKEN AICS in Japan). Unsteady flow phenomena in the present compressor at near-stall condition were analyzed by using data mining techniques such as vortex identification and limiting streamline drawing with the LIC (line integral convolution) method. The simulation showed that the stall in the present compressor could be related to the corner separation on the hub side.

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The Micromix combustion principle, based on cross-flow mixing of air and hydrogen, promises low emission applications in future gas turbines. The Micromix combustion takes place in several hundreds of miniaturized diffusion-type micro-flames. The major advantage is the inherent safety against flash-back and low NOx-emissions due to a very short residence time of reactants in the flame region. The paper gives insight into the Micromix design and scaling procedure for different energy densities and the interaction of scaling laws and key design drivers in gas turbine integration. Numerical studies, experimental testing, gas turbine integration and interface considerations are evaluated. The aerodynamic stabilization of the miniaturized flamelets and the resulting flow field, flame structure and NOx formation are analysed experimentally and numerically. The results show and confirm the successful adaption of the low NOx Micromix characteristics for a range of different nozzle sizes, energy densities and thermal power output.

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In this work a three-dimensional finite element (FEM) code is used to perform the stability analysis of an experimental rig designed and operated in order to study the propensity of full-scale industrial burners to thermo-acoustic combustion instabilities. The Burner Transfer Matrix (BTM) approach is used to characterize the influence of the burner. An experimental transfer matrix is used and compared with an analytical model. In the combustion chamber, the influence of the three—dimensional spatial distribution of the thermodynamics quantities in presence of the flame is considered. Reynolds Averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) simulations are used to compute the base flow. A linear stability analysis of the entire system is performed considering the coupling between pressure oscillations (p’) and heat release fluctuations (q’) with a distributed n-t linear Flame Transfer Function (FTF). A three-dimensional spatial distribution of time delay (ｔ) is reconstructed assuming the delay due to convection as the predominant effect. Under these assumptions a good agreement between numerical and experimental results is found both in terms of thermo-acoustic resonant frequencies and mode shape of the resonant modes for different setups of the analyzed system.

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The first trial test for applying plasma actuation technology on a 1.75 MW field rotor was carried out. Specially developed plasma electrodes of 8 m in length were installed on the surface of the leading edge of each blade. An increase in turbine rotational speed has been identified for the plasma-on cases compared with the plasma-off cases for the same wind speed. Also, histogram of inlet wind speed showed a trend that inlet wind speed was shifted to higher speed region for the plasma-on case compared with the plasma-off case. The mechanism of plasma actuation on this behaviour was examined in qualitatively using CFD analysis of model turbine. Consequently, an averaged power increase of 4.9 % was achieved in the test period. Possibility of increase in wind turbine power even in a commercial scale large turbine has been proved by leading-edge flow separation control using the plasma actuation technology.

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